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 files. Normally,
1047 @value{GDBN} executes the commands in these files after all the command
1048 options and arguments have been processed. @xref{Command Files,,Command
1054 @cindex @code{--quiet}
1055 @cindex @code{--silent}
1057 ``Quiet''. Do not print the introductory and copyright messages. These
1058 messages are also suppressed in batch mode.
1061 @cindex @code{--batch}
1062 Run in batch mode. Exit with status @code{0} after processing all the
1063 command files specified with @samp{-x} (and all commands from
1064 initialization files, if not inhibited with @samp{-n}). Exit with
1065 nonzero status if an error occurs in executing the @value{GDBN} commands
1066 in the command files. Batch mode also disables pagination, sets unlimited
1067 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1068 off} were in effect (@pxref{Messages/Warnings}).
1070 Batch mode may be useful for running @value{GDBN} as a filter, for
1071 example to download and run a program on another computer; in order to
1072 make this more useful, the message
1075 Program exited normally.
1079 (which is ordinarily issued whenever a program running under
1080 @value{GDBN} control terminates) is not issued when running in batch
1084 @cindex @code{--batch-silent}
1085 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1086 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1087 unaffected). This is much quieter than @samp{-silent} and would be useless
1088 for an interactive session.
1090 This is particularly useful when using targets that give @samp{Loading section}
1091 messages, for example.
1093 Note that targets that give their output via @value{GDBN}, as opposed to
1094 writing directly to @code{stdout}, will also be made silent.
1096 @item -return-child-result
1097 @cindex @code{--return-child-result}
1098 The return code from @value{GDBN} will be the return code from the child
1099 process (the process being debugged), with the following exceptions:
1103 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1104 internal error. In this case the exit code is the same as it would have been
1105 without @samp{-return-child-result}.
1107 The user quits with an explicit value. E.g., @samp{quit 1}.
1109 The child process never runs, or is not allowed to terminate, in which case
1110 the exit code will be -1.
1113 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1114 when @value{GDBN} is being used as a remote program loader or simulator
1119 @cindex @code{--nowindows}
1121 ``No windows''. If @value{GDBN} comes with a graphical user interface
1122 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1123 interface. If no GUI is available, this option has no effect.
1127 @cindex @code{--windows}
1129 If @value{GDBN} includes a GUI, then this option requires it to be
1132 @item -cd @var{directory}
1134 Run @value{GDBN} using @var{directory} as its working directory,
1135 instead of the current directory.
1137 @item -data-directory @var{directory}
1138 @cindex @code{--data-directory}
1139 Run @value{GDBN} using @var{directory} as its data directory.
1140 The data directory is where @value{GDBN} searches for its
1141 auxiliary files. @xref{Data Files}.
1145 @cindex @code{--fullname}
1147 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1148 subprocess. It tells @value{GDBN} to output the full file name and line
1149 number in a standard, recognizable fashion each time a stack frame is
1150 displayed (which includes each time your program stops). This
1151 recognizable format looks like two @samp{\032} characters, followed by
1152 the file name, line number and character position separated by colons,
1153 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1154 @samp{\032} characters as a signal to display the source code for the
1158 @cindex @code{--epoch}
1159 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1160 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1161 routines so as to allow Epoch to display values of expressions in a
1164 @item -annotate @var{level}
1165 @cindex @code{--annotate}
1166 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1167 effect is identical to using @samp{set annotate @var{level}}
1168 (@pxref{Annotations}). The annotation @var{level} controls how much
1169 information @value{GDBN} prints together with its prompt, values of
1170 expressions, source lines, and other types of output. Level 0 is the
1171 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1172 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1173 that control @value{GDBN}, and level 2 has been deprecated.
1175 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1179 @cindex @code{--args}
1180 Change interpretation of command line so that arguments following the
1181 executable file are passed as command line arguments to the inferior.
1182 This option stops option processing.
1184 @item -baud @var{bps}
1186 @cindex @code{--baud}
1188 Set the line speed (baud rate or bits per second) of any serial
1189 interface used by @value{GDBN} for remote debugging.
1191 @item -l @var{timeout}
1193 Set the timeout (in seconds) of any communication used by @value{GDBN}
1194 for remote debugging.
1196 @item -tty @var{device}
1197 @itemx -t @var{device}
1198 @cindex @code{--tty}
1200 Run using @var{device} for your program's standard input and output.
1201 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1203 @c resolve the situation of these eventually
1205 @cindex @code{--tui}
1206 Activate the @dfn{Text User Interface} when starting. The Text User
1207 Interface manages several text windows on the terminal, showing
1208 source, assembly, registers and @value{GDBN} command outputs
1209 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1210 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1211 Using @value{GDBN} under @sc{gnu} Emacs}).
1214 @c @cindex @code{--xdb}
1215 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1216 @c For information, see the file @file{xdb_trans.html}, which is usually
1217 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1220 @item -interpreter @var{interp}
1221 @cindex @code{--interpreter}
1222 Use the interpreter @var{interp} for interface with the controlling
1223 program or device. This option is meant to be set by programs which
1224 communicate with @value{GDBN} using it as a back end.
1225 @xref{Interpreters, , Command Interpreters}.
1227 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1228 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1229 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1230 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1231 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1232 @sc{gdb/mi} interfaces are no longer supported.
1235 @cindex @code{--write}
1236 Open the executable and core files for both reading and writing. This
1237 is equivalent to the @samp{set write on} command inside @value{GDBN}
1241 @cindex @code{--statistics}
1242 This option causes @value{GDBN} to print statistics about time and
1243 memory usage after it completes each command and returns to the prompt.
1246 @cindex @code{--version}
1247 This option causes @value{GDBN} to print its version number and
1248 no-warranty blurb, and exit.
1253 @subsection What @value{GDBN} Does During Startup
1254 @cindex @value{GDBN} startup
1256 Here's the description of what @value{GDBN} does during session startup:
1260 Sets up the command interpreter as specified by the command line
1261 (@pxref{Mode Options, interpreter}).
1265 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1266 used when building @value{GDBN}; @pxref{System-wide configuration,
1267 ,System-wide configuration and settings}) and executes all the commands in
1270 @anchor{Home Directory Init File}
1272 Reads the init file (if any) in your home directory@footnote{On
1273 DOS/Windows systems, the home directory is the one pointed to by the
1274 @code{HOME} environment variable.} and executes all the commands in
1277 @anchor{Option -init-eval-command}
1279 Executes commands and command files specified by the @samp{-iex} and
1280 @samp{-ix} options in their specified order. Usually you should use the
1281 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1282 settings before @value{GDBN} init files get executed and before inferior
1286 Processes command line options and operands.
1288 @anchor{Init File in the Current Directory during Startup}
1290 Reads and executes the commands from init file (if any) in the current
1291 working directory as long as @samp{set auto-load local-gdbinit} is set to
1292 @samp{on} (@pxref{Init File in the Current Directory}).
1293 This is only done if the current directory is
1294 different from your home directory. Thus, you can have more than one
1295 init file, one generic in your home directory, and another, specific
1296 to the program you are debugging, in the directory where you invoke
1300 If the command line specified a program to debug, or a process to
1301 attach to, or a core file, @value{GDBN} loads any auto-loaded
1302 scripts provided for the program or for its loaded shared libraries.
1303 @xref{Auto-loading}.
1305 If you wish to disable the auto-loading during startup,
1306 you must do something like the following:
1309 $ gdb -iex "set auto-load python-scripts off" myprogram
1312 Option @samp{-ex} does not work because the auto-loading is then turned
1316 Executes commands and command files specified by the @samp{-ex} and
1317 @samp{-x} options in their specified order. @xref{Command Files}, for
1318 more details about @value{GDBN} command files.
1321 Reads the command history recorded in the @dfn{history file}.
1322 @xref{Command History}, for more details about the command history and the
1323 files where @value{GDBN} records it.
1326 Init files use the same syntax as @dfn{command files} (@pxref{Command
1327 Files}) and are processed by @value{GDBN} in the same way. The init
1328 file in your home directory can set options (such as @samp{set
1329 complaints}) that affect subsequent processing of command line options
1330 and operands. Init files are not executed if you use the @samp{-nx}
1331 option (@pxref{Mode Options, ,Choosing Modes}).
1333 To display the list of init files loaded by gdb at startup, you
1334 can use @kbd{gdb --help}.
1336 @cindex init file name
1337 @cindex @file{.gdbinit}
1338 @cindex @file{gdb.ini}
1339 The @value{GDBN} init files are normally called @file{.gdbinit}.
1340 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1341 the limitations of file names imposed by DOS filesystems. The Windows
1342 ports of @value{GDBN} use the standard name, but if they find a
1343 @file{gdb.ini} file, they warn you about that and suggest to rename
1344 the file to the standard name.
1348 @section Quitting @value{GDBN}
1349 @cindex exiting @value{GDBN}
1350 @cindex leaving @value{GDBN}
1353 @kindex quit @r{[}@var{expression}@r{]}
1354 @kindex q @r{(@code{quit})}
1355 @item quit @r{[}@var{expression}@r{]}
1357 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1358 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1359 do not supply @var{expression}, @value{GDBN} will terminate normally;
1360 otherwise it will terminate using the result of @var{expression} as the
1365 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1366 terminates the action of any @value{GDBN} command that is in progress and
1367 returns to @value{GDBN} command level. It is safe to type the interrupt
1368 character at any time because @value{GDBN} does not allow it to take effect
1369 until a time when it is safe.
1371 If you have been using @value{GDBN} to control an attached process or
1372 device, you can release it with the @code{detach} command
1373 (@pxref{Attach, ,Debugging an Already-running Process}).
1375 @node Shell Commands
1376 @section Shell Commands
1378 If you need to execute occasional shell commands during your
1379 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1380 just use the @code{shell} command.
1385 @cindex shell escape
1386 @item shell @var{command-string}
1387 @itemx !@var{command-string}
1388 Invoke a standard shell to execute @var{command-string}.
1389 Note that no space is needed between @code{!} and @var{command-string}.
1390 If it exists, the environment variable @code{SHELL} determines which
1391 shell to run. Otherwise @value{GDBN} uses the default shell
1392 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1395 The utility @code{make} is often needed in development environments.
1396 You do not have to use the @code{shell} command for this purpose in
1401 @cindex calling make
1402 @item make @var{make-args}
1403 Execute the @code{make} program with the specified
1404 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1407 @node Logging Output
1408 @section Logging Output
1409 @cindex logging @value{GDBN} output
1410 @cindex save @value{GDBN} output to a file
1412 You may want to save the output of @value{GDBN} commands to a file.
1413 There are several commands to control @value{GDBN}'s logging.
1417 @item set logging on
1419 @item set logging off
1421 @cindex logging file name
1422 @item set logging file @var{file}
1423 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1424 @item set logging overwrite [on|off]
1425 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1426 you want @code{set logging on} to overwrite the logfile instead.
1427 @item set logging redirect [on|off]
1428 By default, @value{GDBN} output will go to both the terminal and the logfile.
1429 Set @code{redirect} if you want output to go only to the log file.
1430 @kindex show logging
1432 Show the current values of the logging settings.
1436 @chapter @value{GDBN} Commands
1438 You can abbreviate a @value{GDBN} command to the first few letters of the command
1439 name, if that abbreviation is unambiguous; and you can repeat certain
1440 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1441 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1442 show you the alternatives available, if there is more than one possibility).
1445 * Command Syntax:: How to give commands to @value{GDBN}
1446 * Completion:: Command completion
1447 * Help:: How to ask @value{GDBN} for help
1450 @node Command Syntax
1451 @section Command Syntax
1453 A @value{GDBN} command is a single line of input. There is no limit on
1454 how long it can be. It starts with a command name, which is followed by
1455 arguments whose meaning depends on the command name. For example, the
1456 command @code{step} accepts an argument which is the number of times to
1457 step, as in @samp{step 5}. You can also use the @code{step} command
1458 with no arguments. Some commands do not allow any arguments.
1460 @cindex abbreviation
1461 @value{GDBN} command names may always be truncated if that abbreviation is
1462 unambiguous. Other possible command abbreviations are listed in the
1463 documentation for individual commands. In some cases, even ambiguous
1464 abbreviations are allowed; for example, @code{s} is specially defined as
1465 equivalent to @code{step} even though there are other commands whose
1466 names start with @code{s}. You can test abbreviations by using them as
1467 arguments to the @code{help} command.
1469 @cindex repeating commands
1470 @kindex RET @r{(repeat last command)}
1471 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1472 repeat the previous command. Certain commands (for example, @code{run})
1473 will not repeat this way; these are commands whose unintentional
1474 repetition might cause trouble and which you are unlikely to want to
1475 repeat. User-defined commands can disable this feature; see
1476 @ref{Define, dont-repeat}.
1478 The @code{list} and @code{x} commands, when you repeat them with
1479 @key{RET}, construct new arguments rather than repeating
1480 exactly as typed. This permits easy scanning of source or memory.
1482 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1483 output, in a way similar to the common utility @code{more}
1484 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1485 @key{RET} too many in this situation, @value{GDBN} disables command
1486 repetition after any command that generates this sort of display.
1488 @kindex # @r{(a comment)}
1490 Any text from a @kbd{#} to the end of the line is a comment; it does
1491 nothing. This is useful mainly in command files (@pxref{Command
1492 Files,,Command Files}).
1494 @cindex repeating command sequences
1495 @kindex Ctrl-o @r{(operate-and-get-next)}
1496 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1497 commands. This command accepts the current line, like @key{RET}, and
1498 then fetches the next line relative to the current line from the history
1502 @section Command Completion
1505 @cindex word completion
1506 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1507 only one possibility; it can also show you what the valid possibilities
1508 are for the next word in a command, at any time. This works for @value{GDBN}
1509 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1511 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1512 of a word. If there is only one possibility, @value{GDBN} fills in the
1513 word, and waits for you to finish the command (or press @key{RET} to
1514 enter it). For example, if you type
1516 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1517 @c complete accuracy in these examples; space introduced for clarity.
1518 @c If texinfo enhancements make it unnecessary, it would be nice to
1519 @c replace " @key" by "@key" in the following...
1521 (@value{GDBP}) info bre @key{TAB}
1525 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1526 the only @code{info} subcommand beginning with @samp{bre}:
1529 (@value{GDBP}) info breakpoints
1533 You can either press @key{RET} at this point, to run the @code{info
1534 breakpoints} command, or backspace and enter something else, if
1535 @samp{breakpoints} does not look like the command you expected. (If you
1536 were sure you wanted @code{info breakpoints} in the first place, you
1537 might as well just type @key{RET} immediately after @samp{info bre},
1538 to exploit command abbreviations rather than command completion).
1540 If there is more than one possibility for the next word when you press
1541 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1542 characters and try again, or just press @key{TAB} a second time;
1543 @value{GDBN} displays all the possible completions for that word. For
1544 example, you might want to set a breakpoint on a subroutine whose name
1545 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1546 just sounds the bell. Typing @key{TAB} again displays all the
1547 function names in your program that begin with those characters, for
1551 (@value{GDBP}) b make_ @key{TAB}
1552 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1553 make_a_section_from_file make_environ
1554 make_abs_section make_function_type
1555 make_blockvector make_pointer_type
1556 make_cleanup make_reference_type
1557 make_command make_symbol_completion_list
1558 (@value{GDBP}) b make_
1562 After displaying the available possibilities, @value{GDBN} copies your
1563 partial input (@samp{b make_} in the example) so you can finish the
1566 If you just want to see the list of alternatives in the first place, you
1567 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1568 means @kbd{@key{META} ?}. You can type this either by holding down a
1569 key designated as the @key{META} shift on your keyboard (if there is
1570 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1572 @cindex quotes in commands
1573 @cindex completion of quoted strings
1574 Sometimes the string you need, while logically a ``word'', may contain
1575 parentheses or other characters that @value{GDBN} normally excludes from
1576 its notion of a word. To permit word completion to work in this
1577 situation, you may enclose words in @code{'} (single quote marks) in
1578 @value{GDBN} commands.
1580 The most likely situation where you might need this is in typing the
1581 name of a C@t{++} function. This is because C@t{++} allows function
1582 overloading (multiple definitions of the same function, distinguished
1583 by argument type). For example, when you want to set a breakpoint you
1584 may need to distinguish whether you mean the version of @code{name}
1585 that takes an @code{int} parameter, @code{name(int)}, or the version
1586 that takes a @code{float} parameter, @code{name(float)}. To use the
1587 word-completion facilities in this situation, type a single quote
1588 @code{'} at the beginning of the function name. This alerts
1589 @value{GDBN} that it may need to consider more information than usual
1590 when you press @key{TAB} or @kbd{M-?} to request word completion:
1593 (@value{GDBP}) b 'bubble( @kbd{M-?}
1594 bubble(double,double) bubble(int,int)
1595 (@value{GDBP}) b 'bubble(
1598 In some cases, @value{GDBN} can tell that completing a name requires using
1599 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1600 completing as much as it can) if you do not type the quote in the first
1604 (@value{GDBP}) b bub @key{TAB}
1605 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1606 (@value{GDBP}) b 'bubble(
1610 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1611 you have not yet started typing the argument list when you ask for
1612 completion on an overloaded symbol.
1614 For more information about overloaded functions, see @ref{C Plus Plus
1615 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1616 overload-resolution off} to disable overload resolution;
1617 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1619 @cindex completion of structure field names
1620 @cindex structure field name completion
1621 @cindex completion of union field names
1622 @cindex union field name completion
1623 When completing in an expression which looks up a field in a
1624 structure, @value{GDBN} also tries@footnote{The completer can be
1625 confused by certain kinds of invalid expressions. Also, it only
1626 examines the static type of the expression, not the dynamic type.} to
1627 limit completions to the field names available in the type of the
1631 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1632 magic to_fputs to_rewind
1633 to_data to_isatty to_write
1634 to_delete to_put to_write_async_safe
1639 This is because the @code{gdb_stdout} is a variable of the type
1640 @code{struct ui_file} that is defined in @value{GDBN} sources as
1647 ui_file_flush_ftype *to_flush;
1648 ui_file_write_ftype *to_write;
1649 ui_file_write_async_safe_ftype *to_write_async_safe;
1650 ui_file_fputs_ftype *to_fputs;
1651 ui_file_read_ftype *to_read;
1652 ui_file_delete_ftype *to_delete;
1653 ui_file_isatty_ftype *to_isatty;
1654 ui_file_rewind_ftype *to_rewind;
1655 ui_file_put_ftype *to_put;
1662 @section Getting Help
1663 @cindex online documentation
1666 You can always ask @value{GDBN} itself for information on its commands,
1667 using the command @code{help}.
1670 @kindex h @r{(@code{help})}
1673 You can use @code{help} (abbreviated @code{h}) with no arguments to
1674 display a short list of named classes of commands:
1678 List of classes of commands:
1680 aliases -- Aliases of other commands
1681 breakpoints -- Making program stop at certain points
1682 data -- Examining data
1683 files -- Specifying and examining files
1684 internals -- Maintenance commands
1685 obscure -- Obscure features
1686 running -- Running the program
1687 stack -- Examining the stack
1688 status -- Status inquiries
1689 support -- Support facilities
1690 tracepoints -- Tracing of program execution without
1691 stopping the program
1692 user-defined -- User-defined commands
1694 Type "help" followed by a class name for a list of
1695 commands in that class.
1696 Type "help" followed by command name for full
1698 Command name abbreviations are allowed if unambiguous.
1701 @c the above line break eliminates huge line overfull...
1703 @item help @var{class}
1704 Using one of the general help classes as an argument, you can get a
1705 list of the individual commands in that class. For example, here is the
1706 help display for the class @code{status}:
1709 (@value{GDBP}) help status
1714 @c Line break in "show" line falsifies real output, but needed
1715 @c to fit in smallbook page size.
1716 info -- Generic command for showing things
1717 about the program being debugged
1718 show -- Generic command for showing things
1721 Type "help" followed by command name for full
1723 Command name abbreviations are allowed if unambiguous.
1727 @item help @var{command}
1728 With a command name as @code{help} argument, @value{GDBN} displays a
1729 short paragraph on how to use that command.
1732 @item apropos @var{args}
1733 The @code{apropos} command searches through all of the @value{GDBN}
1734 commands, and their documentation, for the regular expression specified in
1735 @var{args}. It prints out all matches found. For example:
1746 alias -- Define a new command that is an alias of an existing command
1747 aliases -- Aliases of other commands
1748 d -- Delete some breakpoints or auto-display expressions
1749 del -- Delete some breakpoints or auto-display expressions
1750 delete -- Delete some breakpoints or auto-display expressions
1755 @item complete @var{args}
1756 The @code{complete @var{args}} command lists all the possible completions
1757 for the beginning of a command. Use @var{args} to specify the beginning of the
1758 command you want completed. For example:
1764 @noindent results in:
1775 @noindent This is intended for use by @sc{gnu} Emacs.
1778 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1779 and @code{show} to inquire about the state of your program, or the state
1780 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1781 manual introduces each of them in the appropriate context. The listings
1782 under @code{info} and under @code{show} in the Command, Variable, and
1783 Function Index point to all the sub-commands. @xref{Command and Variable
1789 @kindex i @r{(@code{info})}
1791 This command (abbreviated @code{i}) is for describing the state of your
1792 program. For example, you can show the arguments passed to a function
1793 with @code{info args}, list the registers currently in use with @code{info
1794 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1795 You can get a complete list of the @code{info} sub-commands with
1796 @w{@code{help info}}.
1800 You can assign the result of an expression to an environment variable with
1801 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1802 @code{set prompt $}.
1806 In contrast to @code{info}, @code{show} is for describing the state of
1807 @value{GDBN} itself.
1808 You can change most of the things you can @code{show}, by using the
1809 related command @code{set}; for example, you can control what number
1810 system is used for displays with @code{set radix}, or simply inquire
1811 which is currently in use with @code{show radix}.
1814 To display all the settable parameters and their current
1815 values, you can use @code{show} with no arguments; you may also use
1816 @code{info set}. Both commands produce the same display.
1817 @c FIXME: "info set" violates the rule that "info" is for state of
1818 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1819 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1823 Here are three miscellaneous @code{show} subcommands, all of which are
1824 exceptional in lacking corresponding @code{set} commands:
1827 @kindex show version
1828 @cindex @value{GDBN} version number
1830 Show what version of @value{GDBN} is running. You should include this
1831 information in @value{GDBN} bug-reports. If multiple versions of
1832 @value{GDBN} are in use at your site, you may need to determine which
1833 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1834 commands are introduced, and old ones may wither away. Also, many
1835 system vendors ship variant versions of @value{GDBN}, and there are
1836 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1837 The version number is the same as the one announced when you start
1840 @kindex show copying
1841 @kindex info copying
1842 @cindex display @value{GDBN} copyright
1845 Display information about permission for copying @value{GDBN}.
1847 @kindex show warranty
1848 @kindex info warranty
1850 @itemx info warranty
1851 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1852 if your version of @value{GDBN} comes with one.
1857 @chapter Running Programs Under @value{GDBN}
1859 When you run a program under @value{GDBN}, you must first generate
1860 debugging information when you compile it.
1862 You may start @value{GDBN} with its arguments, if any, in an environment
1863 of your choice. If you are doing native debugging, you may redirect
1864 your program's input and output, debug an already running process, or
1865 kill a child process.
1868 * Compilation:: Compiling for debugging
1869 * Starting:: Starting your program
1870 * Arguments:: Your program's arguments
1871 * Environment:: Your program's environment
1873 * Working Directory:: Your program's working directory
1874 * Input/Output:: Your program's input and output
1875 * Attach:: Debugging an already-running process
1876 * Kill Process:: Killing the child process
1878 * Inferiors and Programs:: Debugging multiple inferiors and programs
1879 * Threads:: Debugging programs with multiple threads
1880 * Forks:: Debugging forks
1881 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1885 @section Compiling for Debugging
1887 In order to debug a program effectively, you need to generate
1888 debugging information when you compile it. This debugging information
1889 is stored in the object file; it describes the data type of each
1890 variable or function and the correspondence between source line numbers
1891 and addresses in the executable code.
1893 To request debugging information, specify the @samp{-g} option when you run
1896 Programs that are to be shipped to your customers are compiled with
1897 optimizations, using the @samp{-O} compiler option. However, some
1898 compilers are unable to handle the @samp{-g} and @samp{-O} options
1899 together. Using those compilers, you cannot generate optimized
1900 executables containing debugging information.
1902 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1903 without @samp{-O}, making it possible to debug optimized code. We
1904 recommend that you @emph{always} use @samp{-g} whenever you compile a
1905 program. You may think your program is correct, but there is no sense
1906 in pushing your luck. For more information, see @ref{Optimized Code}.
1908 Older versions of the @sc{gnu} C compiler permitted a variant option
1909 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1910 format; if your @sc{gnu} C compiler has this option, do not use it.
1912 @value{GDBN} knows about preprocessor macros and can show you their
1913 expansion (@pxref{Macros}). Most compilers do not include information
1914 about preprocessor macros in the debugging information if you specify
1915 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
1916 the @sc{gnu} C compiler, provides macro information if you are using
1917 the DWARF debugging format, and specify the option @option{-g3}.
1919 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
1920 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
1921 information on @value{NGCC} options affecting debug information.
1923 You will have the best debugging experience if you use the latest
1924 version of the DWARF debugging format that your compiler supports.
1925 DWARF is currently the most expressive and best supported debugging
1926 format in @value{GDBN}.
1930 @section Starting your Program
1936 @kindex r @r{(@code{run})}
1939 Use the @code{run} command to start your program under @value{GDBN}.
1940 You must first specify the program name (except on VxWorks) with an
1941 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1942 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1943 (@pxref{Files, ,Commands to Specify Files}).
1947 If you are running your program in an execution environment that
1948 supports processes, @code{run} creates an inferior process and makes
1949 that process run your program. In some environments without processes,
1950 @code{run} jumps to the start of your program. Other targets,
1951 like @samp{remote}, are always running. If you get an error
1952 message like this one:
1955 The "remote" target does not support "run".
1956 Try "help target" or "continue".
1960 then use @code{continue} to run your program. You may need @code{load}
1961 first (@pxref{load}).
1963 The execution of a program is affected by certain information it
1964 receives from its superior. @value{GDBN} provides ways to specify this
1965 information, which you must do @emph{before} starting your program. (You
1966 can change it after starting your program, but such changes only affect
1967 your program the next time you start it.) This information may be
1968 divided into four categories:
1971 @item The @emph{arguments.}
1972 Specify the arguments to give your program as the arguments of the
1973 @code{run} command. If a shell is available on your target, the shell
1974 is used to pass the arguments, so that you may use normal conventions
1975 (such as wildcard expansion or variable substitution) in describing
1977 In Unix systems, you can control which shell is used with the
1978 @code{SHELL} environment variable.
1979 @xref{Arguments, ,Your Program's Arguments}.
1981 @item The @emph{environment.}
1982 Your program normally inherits its environment from @value{GDBN}, but you can
1983 use the @value{GDBN} commands @code{set environment} and @code{unset
1984 environment} to change parts of the environment that affect
1985 your program. @xref{Environment, ,Your Program's Environment}.
1987 @item The @emph{working directory.}
1988 Your program inherits its working directory from @value{GDBN}. You can set
1989 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1990 @xref{Working Directory, ,Your Program's Working Directory}.
1992 @item The @emph{standard input and output.}
1993 Your program normally uses the same device for standard input and
1994 standard output as @value{GDBN} is using. You can redirect input and output
1995 in the @code{run} command line, or you can use the @code{tty} command to
1996 set a different device for your program.
1997 @xref{Input/Output, ,Your Program's Input and Output}.
2000 @emph{Warning:} While input and output redirection work, you cannot use
2001 pipes to pass the output of the program you are debugging to another
2002 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2006 When you issue the @code{run} command, your program begins to execute
2007 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2008 of how to arrange for your program to stop. Once your program has
2009 stopped, you may call functions in your program, using the @code{print}
2010 or @code{call} commands. @xref{Data, ,Examining Data}.
2012 If the modification time of your symbol file has changed since the last
2013 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2014 table, and reads it again. When it does this, @value{GDBN} tries to retain
2015 your current breakpoints.
2020 @cindex run to main procedure
2021 The name of the main procedure can vary from language to language.
2022 With C or C@t{++}, the main procedure name is always @code{main}, but
2023 other languages such as Ada do not require a specific name for their
2024 main procedure. The debugger provides a convenient way to start the
2025 execution of the program and to stop at the beginning of the main
2026 procedure, depending on the language used.
2028 The @samp{start} command does the equivalent of setting a temporary
2029 breakpoint at the beginning of the main procedure and then invoking
2030 the @samp{run} command.
2032 @cindex elaboration phase
2033 Some programs contain an @dfn{elaboration} phase where some startup code is
2034 executed before the main procedure is called. This depends on the
2035 languages used to write your program. In C@t{++}, for instance,
2036 constructors for static and global objects are executed before
2037 @code{main} is called. It is therefore possible that the debugger stops
2038 before reaching the main procedure. However, the temporary breakpoint
2039 will remain to halt execution.
2041 Specify the arguments to give to your program as arguments to the
2042 @samp{start} command. These arguments will be given verbatim to the
2043 underlying @samp{run} command. Note that the same arguments will be
2044 reused if no argument is provided during subsequent calls to
2045 @samp{start} or @samp{run}.
2047 It is sometimes necessary to debug the program during elaboration. In
2048 these cases, using the @code{start} command would stop the execution of
2049 your program too late, as the program would have already completed the
2050 elaboration phase. Under these circumstances, insert breakpoints in your
2051 elaboration code before running your program.
2053 @kindex set exec-wrapper
2054 @item set exec-wrapper @var{wrapper}
2055 @itemx show exec-wrapper
2056 @itemx unset exec-wrapper
2057 When @samp{exec-wrapper} is set, the specified wrapper is used to
2058 launch programs for debugging. @value{GDBN} starts your program
2059 with a shell command of the form @kbd{exec @var{wrapper}
2060 @var{program}}. Quoting is added to @var{program} and its
2061 arguments, but not to @var{wrapper}, so you should add quotes if
2062 appropriate for your shell. The wrapper runs until it executes
2063 your program, and then @value{GDBN} takes control.
2065 You can use any program that eventually calls @code{execve} with
2066 its arguments as a wrapper. Several standard Unix utilities do
2067 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2068 with @code{exec "$@@"} will also work.
2070 For example, you can use @code{env} to pass an environment variable to
2071 the debugged program, without setting the variable in your shell's
2075 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2079 This command is available when debugging locally on most targets, excluding
2080 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2082 @kindex set disable-randomization
2083 @item set disable-randomization
2084 @itemx set disable-randomization on
2085 This option (enabled by default in @value{GDBN}) will turn off the native
2086 randomization of the virtual address space of the started program. This option
2087 is useful for multiple debugging sessions to make the execution better
2088 reproducible and memory addresses reusable across debugging sessions.
2090 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2091 On @sc{gnu}/Linux you can get the same behavior using
2094 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2097 @item set disable-randomization off
2098 Leave the behavior of the started executable unchanged. Some bugs rear their
2099 ugly heads only when the program is loaded at certain addresses. If your bug
2100 disappears when you run the program under @value{GDBN}, that might be because
2101 @value{GDBN} by default disables the address randomization on platforms, such
2102 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2103 disable-randomization off} to try to reproduce such elusive bugs.
2105 On targets where it is available, virtual address space randomization
2106 protects the programs against certain kinds of security attacks. In these
2107 cases the attacker needs to know the exact location of a concrete executable
2108 code. Randomizing its location makes it impossible to inject jumps misusing
2109 a code at its expected addresses.
2111 Prelinking shared libraries provides a startup performance advantage but it
2112 makes addresses in these libraries predictable for privileged processes by
2113 having just unprivileged access at the target system. Reading the shared
2114 library binary gives enough information for assembling the malicious code
2115 misusing it. Still even a prelinked shared library can get loaded at a new
2116 random address just requiring the regular relocation process during the
2117 startup. Shared libraries not already prelinked are always loaded at
2118 a randomly chosen address.
2120 Position independent executables (PIE) contain position independent code
2121 similar to the shared libraries and therefore such executables get loaded at
2122 a randomly chosen address upon startup. PIE executables always load even
2123 already prelinked shared libraries at a random address. You can build such
2124 executable using @command{gcc -fPIE -pie}.
2126 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2127 (as long as the randomization is enabled).
2129 @item show disable-randomization
2130 Show the current setting of the explicit disable of the native randomization of
2131 the virtual address space of the started program.
2136 @section Your Program's Arguments
2138 @cindex arguments (to your program)
2139 The arguments to your program can be specified by the arguments of the
2141 They are passed to a shell, which expands wildcard characters and
2142 performs redirection of I/O, and thence to your program. Your
2143 @code{SHELL} environment variable (if it exists) specifies what shell
2144 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2145 the default shell (@file{/bin/sh} on Unix).
2147 On non-Unix systems, the program is usually invoked directly by
2148 @value{GDBN}, which emulates I/O redirection via the appropriate system
2149 calls, and the wildcard characters are expanded by the startup code of
2150 the program, not by the shell.
2152 @code{run} with no arguments uses the same arguments used by the previous
2153 @code{run}, or those set by the @code{set args} command.
2158 Specify the arguments to be used the next time your program is run. If
2159 @code{set args} has no arguments, @code{run} executes your program
2160 with no arguments. Once you have run your program with arguments,
2161 using @code{set args} before the next @code{run} is the only way to run
2162 it again without arguments.
2166 Show the arguments to give your program when it is started.
2170 @section Your Program's Environment
2172 @cindex environment (of your program)
2173 The @dfn{environment} consists of a set of environment variables and
2174 their values. Environment variables conventionally record such things as
2175 your user name, your home directory, your terminal type, and your search
2176 path for programs to run. Usually you set up environment variables with
2177 the shell and they are inherited by all the other programs you run. When
2178 debugging, it can be useful to try running your program with a modified
2179 environment without having to start @value{GDBN} over again.
2183 @item path @var{directory}
2184 Add @var{directory} to the front of the @code{PATH} environment variable
2185 (the search path for executables) that will be passed to your program.
2186 The value of @code{PATH} used by @value{GDBN} does not change.
2187 You may specify several directory names, separated by whitespace or by a
2188 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2189 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2190 is moved to the front, so it is searched sooner.
2192 You can use the string @samp{$cwd} to refer to whatever is the current
2193 working directory at the time @value{GDBN} searches the path. If you
2194 use @samp{.} instead, it refers to the directory where you executed the
2195 @code{path} command. @value{GDBN} replaces @samp{.} in the
2196 @var{directory} argument (with the current path) before adding
2197 @var{directory} to the search path.
2198 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2199 @c document that, since repeating it would be a no-op.
2203 Display the list of search paths for executables (the @code{PATH}
2204 environment variable).
2206 @kindex show environment
2207 @item show environment @r{[}@var{varname}@r{]}
2208 Print the value of environment variable @var{varname} to be given to
2209 your program when it starts. If you do not supply @var{varname},
2210 print the names and values of all environment variables to be given to
2211 your program. You can abbreviate @code{environment} as @code{env}.
2213 @kindex set environment
2214 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2215 Set environment variable @var{varname} to @var{value}. The value
2216 changes for your program only, not for @value{GDBN} itself. @var{value} may
2217 be any string; the values of environment variables are just strings, and
2218 any interpretation is supplied by your program itself. The @var{value}
2219 parameter is optional; if it is eliminated, the variable is set to a
2221 @c "any string" here does not include leading, trailing
2222 @c blanks. Gnu asks: does anyone care?
2224 For example, this command:
2231 tells the debugged program, when subsequently run, that its user is named
2232 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2233 are not actually required.)
2235 @kindex unset environment
2236 @item unset environment @var{varname}
2237 Remove variable @var{varname} from the environment to be passed to your
2238 program. This is different from @samp{set env @var{varname} =};
2239 @code{unset environment} removes the variable from the environment,
2240 rather than assigning it an empty value.
2243 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2245 by your @code{SHELL} environment variable if it exists (or
2246 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2247 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2248 @file{.bashrc} for BASH---any variables you set in that file affect
2249 your program. You may wish to move setting of environment variables to
2250 files that are only run when you sign on, such as @file{.login} or
2253 @node Working Directory
2254 @section Your Program's Working Directory
2256 @cindex working directory (of your program)
2257 Each time you start your program with @code{run}, it inherits its
2258 working directory from the current working directory of @value{GDBN}.
2259 The @value{GDBN} working directory is initially whatever it inherited
2260 from its parent process (typically the shell), but you can specify a new
2261 working directory in @value{GDBN} with the @code{cd} command.
2263 The @value{GDBN} working directory also serves as a default for the commands
2264 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2269 @cindex change working directory
2270 @item cd @r{[}@var{directory}@r{]}
2271 Set the @value{GDBN} working directory to @var{directory}. If not
2272 given, @var{directory} uses @file{'~'}.
2276 Print the @value{GDBN} working directory.
2279 It is generally impossible to find the current working directory of
2280 the process being debugged (since a program can change its directory
2281 during its run). If you work on a system where @value{GDBN} is
2282 configured with the @file{/proc} support, you can use the @code{info
2283 proc} command (@pxref{SVR4 Process Information}) to find out the
2284 current working directory of the debuggee.
2287 @section Your Program's Input and Output
2292 By default, the program you run under @value{GDBN} does input and output to
2293 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2294 to its own terminal modes to interact with you, but it records the terminal
2295 modes your program was using and switches back to them when you continue
2296 running your program.
2299 @kindex info terminal
2301 Displays information recorded by @value{GDBN} about the terminal modes your
2305 You can redirect your program's input and/or output using shell
2306 redirection with the @code{run} command. For example,
2313 starts your program, diverting its output to the file @file{outfile}.
2316 @cindex controlling terminal
2317 Another way to specify where your program should do input and output is
2318 with the @code{tty} command. This command accepts a file name as
2319 argument, and causes this file to be the default for future @code{run}
2320 commands. It also resets the controlling terminal for the child
2321 process, for future @code{run} commands. For example,
2328 directs that processes started with subsequent @code{run} commands
2329 default to do input and output on the terminal @file{/dev/ttyb} and have
2330 that as their controlling terminal.
2332 An explicit redirection in @code{run} overrides the @code{tty} command's
2333 effect on the input/output device, but not its effect on the controlling
2336 When you use the @code{tty} command or redirect input in the @code{run}
2337 command, only the input @emph{for your program} is affected. The input
2338 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2339 for @code{set inferior-tty}.
2341 @cindex inferior tty
2342 @cindex set inferior controlling terminal
2343 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2344 display the name of the terminal that will be used for future runs of your
2348 @item set inferior-tty /dev/ttyb
2349 @kindex set inferior-tty
2350 Set the tty for the program being debugged to /dev/ttyb.
2352 @item show inferior-tty
2353 @kindex show inferior-tty
2354 Show the current tty for the program being debugged.
2358 @section Debugging an Already-running Process
2363 @item attach @var{process-id}
2364 This command attaches to a running process---one that was started
2365 outside @value{GDBN}. (@code{info files} shows your active
2366 targets.) The command takes as argument a process ID. The usual way to
2367 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2368 or with the @samp{jobs -l} shell command.
2370 @code{attach} does not repeat if you press @key{RET} a second time after
2371 executing the command.
2374 To use @code{attach}, your program must be running in an environment
2375 which supports processes; for example, @code{attach} does not work for
2376 programs on bare-board targets that lack an operating system. You must
2377 also have permission to send the process a signal.
2379 When you use @code{attach}, the debugger finds the program running in
2380 the process first by looking in the current working directory, then (if
2381 the program is not found) by using the source file search path
2382 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2383 the @code{file} command to load the program. @xref{Files, ,Commands to
2386 The first thing @value{GDBN} does after arranging to debug the specified
2387 process is to stop it. You can examine and modify an attached process
2388 with all the @value{GDBN} commands that are ordinarily available when
2389 you start processes with @code{run}. You can insert breakpoints; you
2390 can step and continue; you can modify storage. If you would rather the
2391 process continue running, you may use the @code{continue} command after
2392 attaching @value{GDBN} to the process.
2397 When you have finished debugging the attached process, you can use the
2398 @code{detach} command to release it from @value{GDBN} control. Detaching
2399 the process continues its execution. After the @code{detach} command,
2400 that process and @value{GDBN} become completely independent once more, and you
2401 are ready to @code{attach} another process or start one with @code{run}.
2402 @code{detach} does not repeat if you press @key{RET} again after
2403 executing the command.
2406 If you exit @value{GDBN} while you have an attached process, you detach
2407 that process. If you use the @code{run} command, you kill that process.
2408 By default, @value{GDBN} asks for confirmation if you try to do either of these
2409 things; you can control whether or not you need to confirm by using the
2410 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2414 @section Killing the Child Process
2419 Kill the child process in which your program is running under @value{GDBN}.
2422 This command is useful if you wish to debug a core dump instead of a
2423 running process. @value{GDBN} ignores any core dump file while your program
2426 On some operating systems, a program cannot be executed outside @value{GDBN}
2427 while you have breakpoints set on it inside @value{GDBN}. You can use the
2428 @code{kill} command in this situation to permit running your program
2429 outside the debugger.
2431 The @code{kill} command is also useful if you wish to recompile and
2432 relink your program, since on many systems it is impossible to modify an
2433 executable file while it is running in a process. In this case, when you
2434 next type @code{run}, @value{GDBN} notices that the file has changed, and
2435 reads the symbol table again (while trying to preserve your current
2436 breakpoint settings).
2438 @node Inferiors and Programs
2439 @section Debugging Multiple Inferiors and Programs
2441 @value{GDBN} lets you run and debug multiple programs in a single
2442 session. In addition, @value{GDBN} on some systems may let you run
2443 several programs simultaneously (otherwise you have to exit from one
2444 before starting another). In the most general case, you can have
2445 multiple threads of execution in each of multiple processes, launched
2446 from multiple executables.
2449 @value{GDBN} represents the state of each program execution with an
2450 object called an @dfn{inferior}. An inferior typically corresponds to
2451 a process, but is more general and applies also to targets that do not
2452 have processes. Inferiors may be created before a process runs, and
2453 may be retained after a process exits. Inferiors have unique
2454 identifiers that are different from process ids. Usually each
2455 inferior will also have its own distinct address space, although some
2456 embedded targets may have several inferiors running in different parts
2457 of a single address space. Each inferior may in turn have multiple
2458 threads running in it.
2460 To find out what inferiors exist at any moment, use @w{@code{info
2464 @kindex info inferiors
2465 @item info inferiors
2466 Print a list of all inferiors currently being managed by @value{GDBN}.
2468 @value{GDBN} displays for each inferior (in this order):
2472 the inferior number assigned by @value{GDBN}
2475 the target system's inferior identifier
2478 the name of the executable the inferior is running.
2483 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2484 indicates the current inferior.
2488 @c end table here to get a little more width for example
2491 (@value{GDBP}) info inferiors
2492 Num Description Executable
2493 2 process 2307 hello
2494 * 1 process 3401 goodbye
2497 To switch focus between inferiors, use the @code{inferior} command:
2500 @kindex inferior @var{infno}
2501 @item inferior @var{infno}
2502 Make inferior number @var{infno} the current inferior. The argument
2503 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2504 in the first field of the @samp{info inferiors} display.
2508 You can get multiple executables into a debugging session via the
2509 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2510 systems @value{GDBN} can add inferiors to the debug session
2511 automatically by following calls to @code{fork} and @code{exec}. To
2512 remove inferiors from the debugging session use the
2513 @w{@code{remove-inferiors}} command.
2516 @kindex add-inferior
2517 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2518 Adds @var{n} inferiors to be run using @var{executable} as the
2519 executable. @var{n} defaults to 1. If no executable is specified,
2520 the inferiors begins empty, with no program. You can still assign or
2521 change the program assigned to the inferior at any time by using the
2522 @code{file} command with the executable name as its argument.
2524 @kindex clone-inferior
2525 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2526 Adds @var{n} inferiors ready to execute the same program as inferior
2527 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2528 number of the current inferior. This is a convenient command when you
2529 want to run another instance of the inferior you are debugging.
2532 (@value{GDBP}) info inferiors
2533 Num Description Executable
2534 * 1 process 29964 helloworld
2535 (@value{GDBP}) clone-inferior
2538 (@value{GDBP}) info inferiors
2539 Num Description Executable
2541 * 1 process 29964 helloworld
2544 You can now simply switch focus to inferior 2 and run it.
2546 @kindex remove-inferiors
2547 @item remove-inferiors @var{infno}@dots{}
2548 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2549 possible to remove an inferior that is running with this command. For
2550 those, use the @code{kill} or @code{detach} command first.
2554 To quit debugging one of the running inferiors that is not the current
2555 inferior, you can either detach from it by using the @w{@code{detach
2556 inferior}} command (allowing it to run independently), or kill it
2557 using the @w{@code{kill inferiors}} command:
2560 @kindex detach inferiors @var{infno}@dots{}
2561 @item detach inferior @var{infno}@dots{}
2562 Detach from the inferior or inferiors identified by @value{GDBN}
2563 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2564 still stays on the list of inferiors shown by @code{info inferiors},
2565 but its Description will show @samp{<null>}.
2567 @kindex kill inferiors @var{infno}@dots{}
2568 @item kill inferiors @var{infno}@dots{}
2569 Kill the inferior or inferiors identified by @value{GDBN} inferior
2570 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2571 stays on the list of inferiors shown by @code{info inferiors}, but its
2572 Description will show @samp{<null>}.
2575 After the successful completion of a command such as @code{detach},
2576 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2577 a normal process exit, the inferior is still valid and listed with
2578 @code{info inferiors}, ready to be restarted.
2581 To be notified when inferiors are started or exit under @value{GDBN}'s
2582 control use @w{@code{set print inferior-events}}:
2585 @kindex set print inferior-events
2586 @cindex print messages on inferior start and exit
2587 @item set print inferior-events
2588 @itemx set print inferior-events on
2589 @itemx set print inferior-events off
2590 The @code{set print inferior-events} command allows you to enable or
2591 disable printing of messages when @value{GDBN} notices that new
2592 inferiors have started or that inferiors have exited or have been
2593 detached. By default, these messages will not be printed.
2595 @kindex show print inferior-events
2596 @item show print inferior-events
2597 Show whether messages will be printed when @value{GDBN} detects that
2598 inferiors have started, exited or have been detached.
2601 Many commands will work the same with multiple programs as with a
2602 single program: e.g., @code{print myglobal} will simply display the
2603 value of @code{myglobal} in the current inferior.
2606 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2607 get more info about the relationship of inferiors, programs, address
2608 spaces in a debug session. You can do that with the @w{@code{maint
2609 info program-spaces}} command.
2612 @kindex maint info program-spaces
2613 @item maint info program-spaces
2614 Print a list of all program spaces currently being managed by
2617 @value{GDBN} displays for each program space (in this order):
2621 the program space number assigned by @value{GDBN}
2624 the name of the executable loaded into the program space, with e.g.,
2625 the @code{file} command.
2630 An asterisk @samp{*} preceding the @value{GDBN} program space number
2631 indicates the current program space.
2633 In addition, below each program space line, @value{GDBN} prints extra
2634 information that isn't suitable to display in tabular form. For
2635 example, the list of inferiors bound to the program space.
2638 (@value{GDBP}) maint info program-spaces
2641 Bound inferiors: ID 1 (process 21561)
2645 Here we can see that no inferior is running the program @code{hello},
2646 while @code{process 21561} is running the program @code{goodbye}. On
2647 some targets, it is possible that multiple inferiors are bound to the
2648 same program space. The most common example is that of debugging both
2649 the parent and child processes of a @code{vfork} call. For example,
2652 (@value{GDBP}) maint info program-spaces
2655 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2658 Here, both inferior 2 and inferior 1 are running in the same program
2659 space as a result of inferior 1 having executed a @code{vfork} call.
2663 @section Debugging Programs with Multiple Threads
2665 @cindex threads of execution
2666 @cindex multiple threads
2667 @cindex switching threads
2668 In some operating systems, such as HP-UX and Solaris, a single program
2669 may have more than one @dfn{thread} of execution. The precise semantics
2670 of threads differ from one operating system to another, but in general
2671 the threads of a single program are akin to multiple processes---except
2672 that they share one address space (that is, they can all examine and
2673 modify the same variables). On the other hand, each thread has its own
2674 registers and execution stack, and perhaps private memory.
2676 @value{GDBN} provides these facilities for debugging multi-thread
2680 @item automatic notification of new threads
2681 @item @samp{thread @var{threadno}}, a command to switch among threads
2682 @item @samp{info threads}, a command to inquire about existing threads
2683 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2684 a command to apply a command to a list of threads
2685 @item thread-specific breakpoints
2686 @item @samp{set print thread-events}, which controls printing of
2687 messages on thread start and exit.
2688 @item @samp{set libthread-db-search-path @var{path}}, which lets
2689 the user specify which @code{libthread_db} to use if the default choice
2690 isn't compatible with the program.
2694 @emph{Warning:} These facilities are not yet available on every
2695 @value{GDBN} configuration where the operating system supports threads.
2696 If your @value{GDBN} does not support threads, these commands have no
2697 effect. For example, a system without thread support shows no output
2698 from @samp{info threads}, and always rejects the @code{thread} command,
2702 (@value{GDBP}) info threads
2703 (@value{GDBP}) thread 1
2704 Thread ID 1 not known. Use the "info threads" command to
2705 see the IDs of currently known threads.
2707 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2708 @c doesn't support threads"?
2711 @cindex focus of debugging
2712 @cindex current thread
2713 The @value{GDBN} thread debugging facility allows you to observe all
2714 threads while your program runs---but whenever @value{GDBN} takes
2715 control, one thread in particular is always the focus of debugging.
2716 This thread is called the @dfn{current thread}. Debugging commands show
2717 program information from the perspective of the current thread.
2719 @cindex @code{New} @var{systag} message
2720 @cindex thread identifier (system)
2721 @c FIXME-implementors!! It would be more helpful if the [New...] message
2722 @c included GDB's numeric thread handle, so you could just go to that
2723 @c thread without first checking `info threads'.
2724 Whenever @value{GDBN} detects a new thread in your program, it displays
2725 the target system's identification for the thread with a message in the
2726 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2727 whose form varies depending on the particular system. For example, on
2728 @sc{gnu}/Linux, you might see
2731 [New Thread 0x41e02940 (LWP 25582)]
2735 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2736 the @var{systag} is simply something like @samp{process 368}, with no
2739 @c FIXME!! (1) Does the [New...] message appear even for the very first
2740 @c thread of a program, or does it only appear for the
2741 @c second---i.e.@: when it becomes obvious we have a multithread
2743 @c (2) *Is* there necessarily a first thread always? Or do some
2744 @c multithread systems permit starting a program with multiple
2745 @c threads ab initio?
2747 @cindex thread number
2748 @cindex thread identifier (GDB)
2749 For debugging purposes, @value{GDBN} associates its own thread
2750 number---always a single integer---with each thread in your program.
2753 @kindex info threads
2754 @item info threads @r{[}@var{id}@dots{}@r{]}
2755 Display a summary of all threads currently in your program. Optional
2756 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2757 means to print information only about the specified thread or threads.
2758 @value{GDBN} displays for each thread (in this order):
2762 the thread number assigned by @value{GDBN}
2765 the target system's thread identifier (@var{systag})
2768 the thread's name, if one is known. A thread can either be named by
2769 the user (see @code{thread name}, below), or, in some cases, by the
2773 the current stack frame summary for that thread
2777 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2778 indicates the current thread.
2782 @c end table here to get a little more width for example
2785 (@value{GDBP}) info threads
2787 3 process 35 thread 27 0x34e5 in sigpause ()
2788 2 process 35 thread 23 0x34e5 in sigpause ()
2789 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2793 On Solaris, you can display more information about user threads with a
2794 Solaris-specific command:
2797 @item maint info sol-threads
2798 @kindex maint info sol-threads
2799 @cindex thread info (Solaris)
2800 Display info on Solaris user threads.
2804 @kindex thread @var{threadno}
2805 @item thread @var{threadno}
2806 Make thread number @var{threadno} the current thread. The command
2807 argument @var{threadno} is the internal @value{GDBN} thread number, as
2808 shown in the first field of the @samp{info threads} display.
2809 @value{GDBN} responds by displaying the system identifier of the thread
2810 you selected, and its current stack frame summary:
2813 (@value{GDBP}) thread 2
2814 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2815 #0 some_function (ignore=0x0) at example.c:8
2816 8 printf ("hello\n");
2820 As with the @samp{[New @dots{}]} message, the form of the text after
2821 @samp{Switching to} depends on your system's conventions for identifying
2824 @vindex $_thread@r{, convenience variable}
2825 The debugger convenience variable @samp{$_thread} contains the number
2826 of the current thread. You may find this useful in writing breakpoint
2827 conditional expressions, command scripts, and so forth. See
2828 @xref{Convenience Vars,, Convenience Variables}, for general
2829 information on convenience variables.
2831 @kindex thread apply
2832 @cindex apply command to several threads
2833 @item thread apply [@var{threadno} | all] @var{command}
2834 The @code{thread apply} command allows you to apply the named
2835 @var{command} to one or more threads. Specify the numbers of the
2836 threads that you want affected with the command argument
2837 @var{threadno}. It can be a single thread number, one of the numbers
2838 shown in the first field of the @samp{info threads} display; or it
2839 could be a range of thread numbers, as in @code{2-4}. To apply a
2840 command to all threads, type @kbd{thread apply all @var{command}}.
2843 @cindex name a thread
2844 @item thread name [@var{name}]
2845 This command assigns a name to the current thread. If no argument is
2846 given, any existing user-specified name is removed. The thread name
2847 appears in the @samp{info threads} display.
2849 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
2850 determine the name of the thread as given by the OS. On these
2851 systems, a name specified with @samp{thread name} will override the
2852 system-give name, and removing the user-specified name will cause
2853 @value{GDBN} to once again display the system-specified name.
2856 @cindex search for a thread
2857 @item thread find [@var{regexp}]
2858 Search for and display thread ids whose name or @var{systag}
2859 matches the supplied regular expression.
2861 As well as being the complement to the @samp{thread name} command,
2862 this command also allows you to identify a thread by its target
2863 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
2867 (@value{GDBN}) thread find 26688
2868 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
2869 (@value{GDBN}) info thread 4
2871 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
2874 @kindex set print thread-events
2875 @cindex print messages on thread start and exit
2876 @item set print thread-events
2877 @itemx set print thread-events on
2878 @itemx set print thread-events off
2879 The @code{set print thread-events} command allows you to enable or
2880 disable printing of messages when @value{GDBN} notices that new threads have
2881 started or that threads have exited. By default, these messages will
2882 be printed if detection of these events is supported by the target.
2883 Note that these messages cannot be disabled on all targets.
2885 @kindex show print thread-events
2886 @item show print thread-events
2887 Show whether messages will be printed when @value{GDBN} detects that threads
2888 have started and exited.
2891 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2892 more information about how @value{GDBN} behaves when you stop and start
2893 programs with multiple threads.
2895 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2896 watchpoints in programs with multiple threads.
2898 @anchor{set libthread-db-search-path}
2900 @kindex set libthread-db-search-path
2901 @cindex search path for @code{libthread_db}
2902 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2903 If this variable is set, @var{path} is a colon-separated list of
2904 directories @value{GDBN} will use to search for @code{libthread_db}.
2905 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2906 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
2907 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
2910 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2911 @code{libthread_db} library to obtain information about threads in the
2912 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2913 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
2914 specific thread debugging library loading is enabled
2915 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
2917 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
2918 refers to the default system directories that are
2919 normally searched for loading shared libraries. The @samp{$sdir} entry
2920 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
2921 (@pxref{libthread_db.so.1 file}).
2923 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
2924 refers to the directory from which @code{libpthread}
2925 was loaded in the inferior process.
2927 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2928 @value{GDBN} attempts to initialize it with the current inferior process.
2929 If this initialization fails (which could happen because of a version
2930 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2931 will unload @code{libthread_db}, and continue with the next directory.
2932 If none of @code{libthread_db} libraries initialize successfully,
2933 @value{GDBN} will issue a warning and thread debugging will be disabled.
2935 Setting @code{libthread-db-search-path} is currently implemented
2936 only on some platforms.
2938 @kindex show libthread-db-search-path
2939 @item show libthread-db-search-path
2940 Display current libthread_db search path.
2942 @kindex set debug libthread-db
2943 @kindex show debug libthread-db
2944 @cindex debugging @code{libthread_db}
2945 @item set debug libthread-db
2946 @itemx show debug libthread-db
2947 Turns on or off display of @code{libthread_db}-related events.
2948 Use @code{1} to enable, @code{0} to disable.
2952 @section Debugging Forks
2954 @cindex fork, debugging programs which call
2955 @cindex multiple processes
2956 @cindex processes, multiple
2957 On most systems, @value{GDBN} has no special support for debugging
2958 programs which create additional processes using the @code{fork}
2959 function. When a program forks, @value{GDBN} will continue to debug the
2960 parent process and the child process will run unimpeded. If you have
2961 set a breakpoint in any code which the child then executes, the child
2962 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2963 will cause it to terminate.
2965 However, if you want to debug the child process there is a workaround
2966 which isn't too painful. Put a call to @code{sleep} in the code which
2967 the child process executes after the fork. It may be useful to sleep
2968 only if a certain environment variable is set, or a certain file exists,
2969 so that the delay need not occur when you don't want to run @value{GDBN}
2970 on the child. While the child is sleeping, use the @code{ps} program to
2971 get its process ID. Then tell @value{GDBN} (a new invocation of
2972 @value{GDBN} if you are also debugging the parent process) to attach to
2973 the child process (@pxref{Attach}). From that point on you can debug
2974 the child process just like any other process which you attached to.
2976 On some systems, @value{GDBN} provides support for debugging programs that
2977 create additional processes using the @code{fork} or @code{vfork} functions.
2978 Currently, the only platforms with this feature are HP-UX (11.x and later
2979 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2981 By default, when a program forks, @value{GDBN} will continue to debug
2982 the parent process and the child process will run unimpeded.
2984 If you want to follow the child process instead of the parent process,
2985 use the command @w{@code{set follow-fork-mode}}.
2988 @kindex set follow-fork-mode
2989 @item set follow-fork-mode @var{mode}
2990 Set the debugger response to a program call of @code{fork} or
2991 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2992 process. The @var{mode} argument can be:
2996 The original process is debugged after a fork. The child process runs
2997 unimpeded. This is the default.
3000 The new process is debugged after a fork. The parent process runs
3005 @kindex show follow-fork-mode
3006 @item show follow-fork-mode
3007 Display the current debugger response to a @code{fork} or @code{vfork} call.
3010 @cindex debugging multiple processes
3011 On Linux, if you want to debug both the parent and child processes, use the
3012 command @w{@code{set detach-on-fork}}.
3015 @kindex set detach-on-fork
3016 @item set detach-on-fork @var{mode}
3017 Tells gdb whether to detach one of the processes after a fork, or
3018 retain debugger control over them both.
3022 The child process (or parent process, depending on the value of
3023 @code{follow-fork-mode}) will be detached and allowed to run
3024 independently. This is the default.
3027 Both processes will be held under the control of @value{GDBN}.
3028 One process (child or parent, depending on the value of
3029 @code{follow-fork-mode}) is debugged as usual, while the other
3034 @kindex show detach-on-fork
3035 @item show detach-on-fork
3036 Show whether detach-on-fork mode is on/off.
3039 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3040 will retain control of all forked processes (including nested forks).
3041 You can list the forked processes under the control of @value{GDBN} by
3042 using the @w{@code{info inferiors}} command, and switch from one fork
3043 to another by using the @code{inferior} command (@pxref{Inferiors and
3044 Programs, ,Debugging Multiple Inferiors and Programs}).
3046 To quit debugging one of the forked processes, you can either detach
3047 from it by using the @w{@code{detach inferiors}} command (allowing it
3048 to run independently), or kill it using the @w{@code{kill inferiors}}
3049 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3052 If you ask to debug a child process and a @code{vfork} is followed by an
3053 @code{exec}, @value{GDBN} executes the new target up to the first
3054 breakpoint in the new target. If you have a breakpoint set on
3055 @code{main} in your original program, the breakpoint will also be set on
3056 the child process's @code{main}.
3058 On some systems, when a child process is spawned by @code{vfork}, you
3059 cannot debug the child or parent until an @code{exec} call completes.
3061 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3062 call executes, the new target restarts. To restart the parent
3063 process, use the @code{file} command with the parent executable name
3064 as its argument. By default, after an @code{exec} call executes,
3065 @value{GDBN} discards the symbols of the previous executable image.
3066 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3070 @kindex set follow-exec-mode
3071 @item set follow-exec-mode @var{mode}
3073 Set debugger response to a program call of @code{exec}. An
3074 @code{exec} call replaces the program image of a process.
3076 @code{follow-exec-mode} can be:
3080 @value{GDBN} creates a new inferior and rebinds the process to this
3081 new inferior. The program the process was running before the
3082 @code{exec} call can be restarted afterwards by restarting the
3088 (@value{GDBP}) info inferiors
3090 Id Description Executable
3093 process 12020 is executing new program: prog2
3094 Program exited normally.
3095 (@value{GDBP}) info inferiors
3096 Id Description Executable
3102 @value{GDBN} keeps the process bound to the same inferior. The new
3103 executable image replaces the previous executable loaded in the
3104 inferior. Restarting the inferior after the @code{exec} call, with
3105 e.g., the @code{run} command, restarts the executable the process was
3106 running after the @code{exec} call. This is the default mode.
3111 (@value{GDBP}) info inferiors
3112 Id Description Executable
3115 process 12020 is executing new program: prog2
3116 Program exited normally.
3117 (@value{GDBP}) info inferiors
3118 Id Description Executable
3125 You can use the @code{catch} command to make @value{GDBN} stop whenever
3126 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3127 Catchpoints, ,Setting Catchpoints}.
3129 @node Checkpoint/Restart
3130 @section Setting a @emph{Bookmark} to Return to Later
3135 @cindex snapshot of a process
3136 @cindex rewind program state
3138 On certain operating systems@footnote{Currently, only
3139 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3140 program's state, called a @dfn{checkpoint}, and come back to it
3143 Returning to a checkpoint effectively undoes everything that has
3144 happened in the program since the @code{checkpoint} was saved. This
3145 includes changes in memory, registers, and even (within some limits)
3146 system state. Effectively, it is like going back in time to the
3147 moment when the checkpoint was saved.
3149 Thus, if you're stepping thru a program and you think you're
3150 getting close to the point where things go wrong, you can save
3151 a checkpoint. Then, if you accidentally go too far and miss
3152 the critical statement, instead of having to restart your program
3153 from the beginning, you can just go back to the checkpoint and
3154 start again from there.
3156 This can be especially useful if it takes a lot of time or
3157 steps to reach the point where you think the bug occurs.
3159 To use the @code{checkpoint}/@code{restart} method of debugging:
3164 Save a snapshot of the debugged program's current execution state.
3165 The @code{checkpoint} command takes no arguments, but each checkpoint
3166 is assigned a small integer id, similar to a breakpoint id.
3168 @kindex info checkpoints
3169 @item info checkpoints
3170 List the checkpoints that have been saved in the current debugging
3171 session. For each checkpoint, the following information will be
3178 @item Source line, or label
3181 @kindex restart @var{checkpoint-id}
3182 @item restart @var{checkpoint-id}
3183 Restore the program state that was saved as checkpoint number
3184 @var{checkpoint-id}. All program variables, registers, stack frames
3185 etc.@: will be returned to the values that they had when the checkpoint
3186 was saved. In essence, gdb will ``wind back the clock'' to the point
3187 in time when the checkpoint was saved.
3189 Note that breakpoints, @value{GDBN} variables, command history etc.
3190 are not affected by restoring a checkpoint. In general, a checkpoint
3191 only restores things that reside in the program being debugged, not in
3194 @kindex delete checkpoint @var{checkpoint-id}
3195 @item delete checkpoint @var{checkpoint-id}
3196 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3200 Returning to a previously saved checkpoint will restore the user state
3201 of the program being debugged, plus a significant subset of the system
3202 (OS) state, including file pointers. It won't ``un-write'' data from
3203 a file, but it will rewind the file pointer to the previous location,
3204 so that the previously written data can be overwritten. For files
3205 opened in read mode, the pointer will also be restored so that the
3206 previously read data can be read again.
3208 Of course, characters that have been sent to a printer (or other
3209 external device) cannot be ``snatched back'', and characters received
3210 from eg.@: a serial device can be removed from internal program buffers,
3211 but they cannot be ``pushed back'' into the serial pipeline, ready to
3212 be received again. Similarly, the actual contents of files that have
3213 been changed cannot be restored (at this time).
3215 However, within those constraints, you actually can ``rewind'' your
3216 program to a previously saved point in time, and begin debugging it
3217 again --- and you can change the course of events so as to debug a
3218 different execution path this time.
3220 @cindex checkpoints and process id
3221 Finally, there is one bit of internal program state that will be
3222 different when you return to a checkpoint --- the program's process
3223 id. Each checkpoint will have a unique process id (or @var{pid}),
3224 and each will be different from the program's original @var{pid}.
3225 If your program has saved a local copy of its process id, this could
3226 potentially pose a problem.
3228 @subsection A Non-obvious Benefit of Using Checkpoints
3230 On some systems such as @sc{gnu}/Linux, address space randomization
3231 is performed on new processes for security reasons. This makes it
3232 difficult or impossible to set a breakpoint, or watchpoint, on an
3233 absolute address if you have to restart the program, since the
3234 absolute location of a symbol will change from one execution to the
3237 A checkpoint, however, is an @emph{identical} copy of a process.
3238 Therefore if you create a checkpoint at (eg.@:) the start of main,
3239 and simply return to that checkpoint instead of restarting the
3240 process, you can avoid the effects of address randomization and
3241 your symbols will all stay in the same place.
3244 @chapter Stopping and Continuing
3246 The principal purposes of using a debugger are so that you can stop your
3247 program before it terminates; or so that, if your program runs into
3248 trouble, you can investigate and find out why.
3250 Inside @value{GDBN}, your program may stop for any of several reasons,
3251 such as a signal, a breakpoint, or reaching a new line after a
3252 @value{GDBN} command such as @code{step}. You may then examine and
3253 change variables, set new breakpoints or remove old ones, and then
3254 continue execution. Usually, the messages shown by @value{GDBN} provide
3255 ample explanation of the status of your program---but you can also
3256 explicitly request this information at any time.
3259 @kindex info program
3261 Display information about the status of your program: whether it is
3262 running or not, what process it is, and why it stopped.
3266 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3267 * Continuing and Stepping:: Resuming execution
3268 * Skipping Over Functions and Files::
3269 Skipping over functions and files
3271 * Thread Stops:: Stopping and starting multi-thread programs
3275 @section Breakpoints, Watchpoints, and Catchpoints
3278 A @dfn{breakpoint} makes your program stop whenever a certain point in
3279 the program is reached. For each breakpoint, you can add conditions to
3280 control in finer detail whether your program stops. You can set
3281 breakpoints with the @code{break} command and its variants (@pxref{Set
3282 Breaks, ,Setting Breakpoints}), to specify the place where your program
3283 should stop by line number, function name or exact address in the
3286 On some systems, you can set breakpoints in shared libraries before
3287 the executable is run. There is a minor limitation on HP-UX systems:
3288 you must wait until the executable is run in order to set breakpoints
3289 in shared library routines that are not called directly by the program
3290 (for example, routines that are arguments in a @code{pthread_create}
3294 @cindex data breakpoints
3295 @cindex memory tracing
3296 @cindex breakpoint on memory address
3297 @cindex breakpoint on variable modification
3298 A @dfn{watchpoint} is a special breakpoint that stops your program
3299 when the value of an expression changes. The expression may be a value
3300 of a variable, or it could involve values of one or more variables
3301 combined by operators, such as @samp{a + b}. This is sometimes called
3302 @dfn{data breakpoints}. You must use a different command to set
3303 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3304 from that, you can manage a watchpoint like any other breakpoint: you
3305 enable, disable, and delete both breakpoints and watchpoints using the
3308 You can arrange to have values from your program displayed automatically
3309 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3313 @cindex breakpoint on events
3314 A @dfn{catchpoint} is another special breakpoint that stops your program
3315 when a certain kind of event occurs, such as the throwing of a C@t{++}
3316 exception or the loading of a library. As with watchpoints, you use a
3317 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3318 Catchpoints}), but aside from that, you can manage a catchpoint like any
3319 other breakpoint. (To stop when your program receives a signal, use the
3320 @code{handle} command; see @ref{Signals, ,Signals}.)
3322 @cindex breakpoint numbers
3323 @cindex numbers for breakpoints
3324 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3325 catchpoint when you create it; these numbers are successive integers
3326 starting with one. In many of the commands for controlling various
3327 features of breakpoints you use the breakpoint number to say which
3328 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3329 @dfn{disabled}; if disabled, it has no effect on your program until you
3332 @cindex breakpoint ranges
3333 @cindex ranges of breakpoints
3334 Some @value{GDBN} commands accept a range of breakpoints on which to
3335 operate. A breakpoint range is either a single breakpoint number, like
3336 @samp{5}, or two such numbers, in increasing order, separated by a
3337 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3338 all breakpoints in that range are operated on.
3341 * Set Breaks:: Setting breakpoints
3342 * Set Watchpoints:: Setting watchpoints
3343 * Set Catchpoints:: Setting catchpoints
3344 * Delete Breaks:: Deleting breakpoints
3345 * Disabling:: Disabling breakpoints
3346 * Conditions:: Break conditions
3347 * Break Commands:: Breakpoint command lists
3348 * Dynamic Printf:: Dynamic printf
3349 * Save Breakpoints:: How to save breakpoints in a file
3350 * Static Probe Points:: Listing static probe points
3351 * Error in Breakpoints:: ``Cannot insert breakpoints''
3352 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3356 @subsection Setting Breakpoints
3358 @c FIXME LMB what does GDB do if no code on line of breakpt?
3359 @c consider in particular declaration with/without initialization.
3361 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3364 @kindex b @r{(@code{break})}
3365 @vindex $bpnum@r{, convenience variable}
3366 @cindex latest breakpoint
3367 Breakpoints are set with the @code{break} command (abbreviated
3368 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3369 number of the breakpoint you've set most recently; see @ref{Convenience
3370 Vars,, Convenience Variables}, for a discussion of what you can do with
3371 convenience variables.
3374 @item break @var{location}
3375 Set a breakpoint at the given @var{location}, which can specify a
3376 function name, a line number, or an address of an instruction.
3377 (@xref{Specify Location}, for a list of all the possible ways to
3378 specify a @var{location}.) The breakpoint will stop your program just
3379 before it executes any of the code in the specified @var{location}.
3381 When using source languages that permit overloading of symbols, such as
3382 C@t{++}, a function name may refer to more than one possible place to break.
3383 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3386 It is also possible to insert a breakpoint that will stop the program
3387 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3388 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3391 When called without any arguments, @code{break} sets a breakpoint at
3392 the next instruction to be executed in the selected stack frame
3393 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3394 innermost, this makes your program stop as soon as control
3395 returns to that frame. This is similar to the effect of a
3396 @code{finish} command in the frame inside the selected frame---except
3397 that @code{finish} does not leave an active breakpoint. If you use
3398 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3399 the next time it reaches the current location; this may be useful
3402 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3403 least one instruction has been executed. If it did not do this, you
3404 would be unable to proceed past a breakpoint without first disabling the
3405 breakpoint. This rule applies whether or not the breakpoint already
3406 existed when your program stopped.
3408 @item break @dots{} if @var{cond}
3409 Set a breakpoint with condition @var{cond}; evaluate the expression
3410 @var{cond} each time the breakpoint is reached, and stop only if the
3411 value is nonzero---that is, if @var{cond} evaluates as true.
3412 @samp{@dots{}} stands for one of the possible arguments described
3413 above (or no argument) specifying where to break. @xref{Conditions,
3414 ,Break Conditions}, for more information on breakpoint conditions.
3417 @item tbreak @var{args}
3418 Set a breakpoint enabled only for one stop. @var{args} are the
3419 same as for the @code{break} command, and the breakpoint is set in the same
3420 way, but the breakpoint is automatically deleted after the first time your
3421 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3424 @cindex hardware breakpoints
3425 @item hbreak @var{args}
3426 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3427 @code{break} command and the breakpoint is set in the same way, but the
3428 breakpoint requires hardware support and some target hardware may not
3429 have this support. The main purpose of this is EPROM/ROM code
3430 debugging, so you can set a breakpoint at an instruction without
3431 changing the instruction. This can be used with the new trap-generation
3432 provided by SPARClite DSU and most x86-based targets. These targets
3433 will generate traps when a program accesses some data or instruction
3434 address that is assigned to the debug registers. However the hardware
3435 breakpoint registers can take a limited number of breakpoints. For
3436 example, on the DSU, only two data breakpoints can be set at a time, and
3437 @value{GDBN} will reject this command if more than two are used. Delete
3438 or disable unused hardware breakpoints before setting new ones
3439 (@pxref{Disabling, ,Disabling Breakpoints}).
3440 @xref{Conditions, ,Break Conditions}.
3441 For remote targets, you can restrict the number of hardware
3442 breakpoints @value{GDBN} will use, see @ref{set remote
3443 hardware-breakpoint-limit}.
3446 @item thbreak @var{args}
3447 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3448 are the same as for the @code{hbreak} command and the breakpoint is set in
3449 the same way. However, like the @code{tbreak} command,
3450 the breakpoint is automatically deleted after the
3451 first time your program stops there. Also, like the @code{hbreak}
3452 command, the breakpoint requires hardware support and some target hardware
3453 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3454 See also @ref{Conditions, ,Break Conditions}.
3457 @cindex regular expression
3458 @cindex breakpoints at functions matching a regexp
3459 @cindex set breakpoints in many functions
3460 @item rbreak @var{regex}
3461 Set breakpoints on all functions matching the regular expression
3462 @var{regex}. This command sets an unconditional breakpoint on all
3463 matches, printing a list of all breakpoints it set. Once these
3464 breakpoints are set, they are treated just like the breakpoints set with
3465 the @code{break} command. You can delete them, disable them, or make
3466 them conditional the same way as any other breakpoint.
3468 The syntax of the regular expression is the standard one used with tools
3469 like @file{grep}. Note that this is different from the syntax used by
3470 shells, so for instance @code{foo*} matches all functions that include
3471 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3472 @code{.*} leading and trailing the regular expression you supply, so to
3473 match only functions that begin with @code{foo}, use @code{^foo}.
3475 @cindex non-member C@t{++} functions, set breakpoint in
3476 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3477 breakpoints on overloaded functions that are not members of any special
3480 @cindex set breakpoints on all functions
3481 The @code{rbreak} command can be used to set breakpoints in
3482 @strong{all} the functions in a program, like this:
3485 (@value{GDBP}) rbreak .
3488 @item rbreak @var{file}:@var{regex}
3489 If @code{rbreak} is called with a filename qualification, it limits
3490 the search for functions matching the given regular expression to the
3491 specified @var{file}. This can be used, for example, to set breakpoints on
3492 every function in a given file:
3495 (@value{GDBP}) rbreak file.c:.
3498 The colon separating the filename qualifier from the regex may
3499 optionally be surrounded by spaces.
3501 @kindex info breakpoints
3502 @cindex @code{$_} and @code{info breakpoints}
3503 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3504 @itemx info break @r{[}@var{n}@dots{}@r{]}
3505 Print a table of all breakpoints, watchpoints, and catchpoints set and
3506 not deleted. Optional argument @var{n} means print information only
3507 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3508 For each breakpoint, following columns are printed:
3511 @item Breakpoint Numbers
3513 Breakpoint, watchpoint, or catchpoint.
3515 Whether the breakpoint is marked to be disabled or deleted when hit.
3516 @item Enabled or Disabled
3517 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3518 that are not enabled.
3520 Where the breakpoint is in your program, as a memory address. For a
3521 pending breakpoint whose address is not yet known, this field will
3522 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3523 library that has the symbol or line referred by breakpoint is loaded.
3524 See below for details. A breakpoint with several locations will
3525 have @samp{<MULTIPLE>} in this field---see below for details.
3527 Where the breakpoint is in the source for your program, as a file and
3528 line number. For a pending breakpoint, the original string passed to
3529 the breakpoint command will be listed as it cannot be resolved until
3530 the appropriate shared library is loaded in the future.
3534 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3535 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3536 @value{GDBN} on the host's side. If it is ``target'', then the condition
3537 is evaluated by the target. The @code{info break} command shows
3538 the condition on the line following the affected breakpoint, together with
3539 its condition evaluation mode in between parentheses.
3541 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3542 allowed to have a condition specified for it. The condition is not parsed for
3543 validity until a shared library is loaded that allows the pending
3544 breakpoint to resolve to a valid location.
3547 @code{info break} with a breakpoint
3548 number @var{n} as argument lists only that breakpoint. The
3549 convenience variable @code{$_} and the default examining-address for
3550 the @code{x} command are set to the address of the last breakpoint
3551 listed (@pxref{Memory, ,Examining Memory}).
3554 @code{info break} displays a count of the number of times the breakpoint
3555 has been hit. This is especially useful in conjunction with the
3556 @code{ignore} command. You can ignore a large number of breakpoint
3557 hits, look at the breakpoint info to see how many times the breakpoint
3558 was hit, and then run again, ignoring one less than that number. This
3559 will get you quickly to the last hit of that breakpoint.
3562 For a breakpoints with an enable count (xref) greater than 1,
3563 @code{info break} also displays that count.
3567 @value{GDBN} allows you to set any number of breakpoints at the same place in
3568 your program. There is nothing silly or meaningless about this. When
3569 the breakpoints are conditional, this is even useful
3570 (@pxref{Conditions, ,Break Conditions}).
3572 @cindex multiple locations, breakpoints
3573 @cindex breakpoints, multiple locations
3574 It is possible that a breakpoint corresponds to several locations
3575 in your program. Examples of this situation are:
3579 Multiple functions in the program may have the same name.
3582 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3583 instances of the function body, used in different cases.
3586 For a C@t{++} template function, a given line in the function can
3587 correspond to any number of instantiations.
3590 For an inlined function, a given source line can correspond to
3591 several places where that function is inlined.
3594 In all those cases, @value{GDBN} will insert a breakpoint at all
3595 the relevant locations.
3597 A breakpoint with multiple locations is displayed in the breakpoint
3598 table using several rows---one header row, followed by one row for
3599 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3600 address column. The rows for individual locations contain the actual
3601 addresses for locations, and show the functions to which those
3602 locations belong. The number column for a location is of the form
3603 @var{breakpoint-number}.@var{location-number}.
3608 Num Type Disp Enb Address What
3609 1 breakpoint keep y <MULTIPLE>
3611 breakpoint already hit 1 time
3612 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3613 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3616 Each location can be individually enabled or disabled by passing
3617 @var{breakpoint-number}.@var{location-number} as argument to the
3618 @code{enable} and @code{disable} commands. Note that you cannot
3619 delete the individual locations from the list, you can only delete the
3620 entire list of locations that belong to their parent breakpoint (with
3621 the @kbd{delete @var{num}} command, where @var{num} is the number of
3622 the parent breakpoint, 1 in the above example). Disabling or enabling
3623 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3624 that belong to that breakpoint.
3626 @cindex pending breakpoints
3627 It's quite common to have a breakpoint inside a shared library.
3628 Shared libraries can be loaded and unloaded explicitly,
3629 and possibly repeatedly, as the program is executed. To support
3630 this use case, @value{GDBN} updates breakpoint locations whenever
3631 any shared library is loaded or unloaded. Typically, you would
3632 set a breakpoint in a shared library at the beginning of your
3633 debugging session, when the library is not loaded, and when the
3634 symbols from the library are not available. When you try to set
3635 breakpoint, @value{GDBN} will ask you if you want to set
3636 a so called @dfn{pending breakpoint}---breakpoint whose address
3637 is not yet resolved.
3639 After the program is run, whenever a new shared library is loaded,
3640 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3641 shared library contains the symbol or line referred to by some
3642 pending breakpoint, that breakpoint is resolved and becomes an
3643 ordinary breakpoint. When a library is unloaded, all breakpoints
3644 that refer to its symbols or source lines become pending again.
3646 This logic works for breakpoints with multiple locations, too. For
3647 example, if you have a breakpoint in a C@t{++} template function, and
3648 a newly loaded shared library has an instantiation of that template,
3649 a new location is added to the list of locations for the breakpoint.
3651 Except for having unresolved address, pending breakpoints do not
3652 differ from regular breakpoints. You can set conditions or commands,
3653 enable and disable them and perform other breakpoint operations.
3655 @value{GDBN} provides some additional commands for controlling what
3656 happens when the @samp{break} command cannot resolve breakpoint
3657 address specification to an address:
3659 @kindex set breakpoint pending
3660 @kindex show breakpoint pending
3662 @item set breakpoint pending auto
3663 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3664 location, it queries you whether a pending breakpoint should be created.
3666 @item set breakpoint pending on
3667 This indicates that an unrecognized breakpoint location should automatically
3668 result in a pending breakpoint being created.
3670 @item set breakpoint pending off
3671 This indicates that pending breakpoints are not to be created. Any
3672 unrecognized breakpoint location results in an error. This setting does
3673 not affect any pending breakpoints previously created.
3675 @item show breakpoint pending
3676 Show the current behavior setting for creating pending breakpoints.
3679 The settings above only affect the @code{break} command and its
3680 variants. Once breakpoint is set, it will be automatically updated
3681 as shared libraries are loaded and unloaded.
3683 @cindex automatic hardware breakpoints
3684 For some targets, @value{GDBN} can automatically decide if hardware or
3685 software breakpoints should be used, depending on whether the
3686 breakpoint address is read-only or read-write. This applies to
3687 breakpoints set with the @code{break} command as well as to internal
3688 breakpoints set by commands like @code{next} and @code{finish}. For
3689 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3692 You can control this automatic behaviour with the following commands::
3694 @kindex set breakpoint auto-hw
3695 @kindex show breakpoint auto-hw
3697 @item set breakpoint auto-hw on
3698 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3699 will try to use the target memory map to decide if software or hardware
3700 breakpoint must be used.
3702 @item set breakpoint auto-hw off
3703 This indicates @value{GDBN} should not automatically select breakpoint
3704 type. If the target provides a memory map, @value{GDBN} will warn when
3705 trying to set software breakpoint at a read-only address.
3708 @value{GDBN} normally implements breakpoints by replacing the program code
3709 at the breakpoint address with a special instruction, which, when
3710 executed, given control to the debugger. By default, the program
3711 code is so modified only when the program is resumed. As soon as
3712 the program stops, @value{GDBN} restores the original instructions. This
3713 behaviour guards against leaving breakpoints inserted in the
3714 target should gdb abrubptly disconnect. However, with slow remote
3715 targets, inserting and removing breakpoint can reduce the performance.
3716 This behavior can be controlled with the following commands::
3718 @kindex set breakpoint always-inserted
3719 @kindex show breakpoint always-inserted
3721 @item set breakpoint always-inserted off
3722 All breakpoints, including newly added by the user, are inserted in
3723 the target only when the target is resumed. All breakpoints are
3724 removed from the target when it stops.
3726 @item set breakpoint always-inserted on
3727 Causes all breakpoints to be inserted in the target at all times. If
3728 the user adds a new breakpoint, or changes an existing breakpoint, the
3729 breakpoints in the target are updated immediately. A breakpoint is
3730 removed from the target only when breakpoint itself is removed.
3732 @cindex non-stop mode, and @code{breakpoint always-inserted}
3733 @item set breakpoint always-inserted auto
3734 This is the default mode. If @value{GDBN} is controlling the inferior
3735 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3736 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3737 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3738 @code{breakpoint always-inserted} mode is off.
3741 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3742 when a breakpoint breaks. If the condition is true, then the process being
3743 debugged stops, otherwise the process is resumed.
3745 If the target supports evaluating conditions on its end, @value{GDBN} may
3746 download the breakpoint, together with its conditions, to it.
3748 This feature can be controlled via the following commands:
3750 @kindex set breakpoint condition-evaluation
3751 @kindex show breakpoint condition-evaluation
3753 @item set breakpoint condition-evaluation host
3754 This option commands @value{GDBN} to evaluate the breakpoint
3755 conditions on the host's side. Unconditional breakpoints are sent to
3756 the target which in turn receives the triggers and reports them back to GDB
3757 for condition evaluation. This is the standard evaluation mode.
3759 @item set breakpoint condition-evaluation target
3760 This option commands @value{GDBN} to download breakpoint conditions
3761 to the target at the moment of their insertion. The target
3762 is responsible for evaluating the conditional expression and reporting
3763 breakpoint stop events back to @value{GDBN} whenever the condition
3764 is true. Due to limitations of target-side evaluation, some conditions
3765 cannot be evaluated there, e.g., conditions that depend on local data
3766 that is only known to the host. Examples include
3767 conditional expressions involving convenience variables, complex types
3768 that cannot be handled by the agent expression parser and expressions
3769 that are too long to be sent over to the target, specially when the
3770 target is a remote system. In these cases, the conditions will be
3771 evaluated by @value{GDBN}.
3773 @item set breakpoint condition-evaluation auto
3774 This is the default mode. If the target supports evaluating breakpoint
3775 conditions on its end, @value{GDBN} will download breakpoint conditions to
3776 the target (limitations mentioned previously apply). If the target does
3777 not support breakpoint condition evaluation, then @value{GDBN} will fallback
3778 to evaluating all these conditions on the host's side.
3782 @cindex negative breakpoint numbers
3783 @cindex internal @value{GDBN} breakpoints
3784 @value{GDBN} itself sometimes sets breakpoints in your program for
3785 special purposes, such as proper handling of @code{longjmp} (in C
3786 programs). These internal breakpoints are assigned negative numbers,
3787 starting with @code{-1}; @samp{info breakpoints} does not display them.
3788 You can see these breakpoints with the @value{GDBN} maintenance command
3789 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3792 @node Set Watchpoints
3793 @subsection Setting Watchpoints
3795 @cindex setting watchpoints
3796 You can use a watchpoint to stop execution whenever the value of an
3797 expression changes, without having to predict a particular place where
3798 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3799 The expression may be as simple as the value of a single variable, or
3800 as complex as many variables combined by operators. Examples include:
3804 A reference to the value of a single variable.
3807 An address cast to an appropriate data type. For example,
3808 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3809 address (assuming an @code{int} occupies 4 bytes).
3812 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3813 expression can use any operators valid in the program's native
3814 language (@pxref{Languages}).
3817 You can set a watchpoint on an expression even if the expression can
3818 not be evaluated yet. For instance, you can set a watchpoint on
3819 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3820 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3821 the expression produces a valid value. If the expression becomes
3822 valid in some other way than changing a variable (e.g.@: if the memory
3823 pointed to by @samp{*global_ptr} becomes readable as the result of a
3824 @code{malloc} call), @value{GDBN} may not stop until the next time
3825 the expression changes.
3827 @cindex software watchpoints
3828 @cindex hardware watchpoints
3829 Depending on your system, watchpoints may be implemented in software or
3830 hardware. @value{GDBN} does software watchpointing by single-stepping your
3831 program and testing the variable's value each time, which is hundreds of
3832 times slower than normal execution. (But this may still be worth it, to
3833 catch errors where you have no clue what part of your program is the
3836 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3837 x86-based targets, @value{GDBN} includes support for hardware
3838 watchpoints, which do not slow down the running of your program.
3842 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3843 Set a watchpoint for an expression. @value{GDBN} will break when the
3844 expression @var{expr} is written into by the program and its value
3845 changes. The simplest (and the most popular) use of this command is
3846 to watch the value of a single variable:
3849 (@value{GDBP}) watch foo
3852 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3853 argument, @value{GDBN} breaks only when the thread identified by
3854 @var{threadnum} changes the value of @var{expr}. If any other threads
3855 change the value of @var{expr}, @value{GDBN} will not break. Note
3856 that watchpoints restricted to a single thread in this way only work
3857 with Hardware Watchpoints.
3859 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3860 (see below). The @code{-location} argument tells @value{GDBN} to
3861 instead watch the memory referred to by @var{expr}. In this case,
3862 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3863 and watch the memory at that address. The type of the result is used
3864 to determine the size of the watched memory. If the expression's
3865 result does not have an address, then @value{GDBN} will print an
3868 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
3869 of masked watchpoints, if the current architecture supports this
3870 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
3871 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
3872 to an address to watch. The mask specifies that some bits of an address
3873 (the bits which are reset in the mask) should be ignored when matching
3874 the address accessed by the inferior against the watchpoint address.
3875 Thus, a masked watchpoint watches many addresses simultaneously---those
3876 addresses whose unmasked bits are identical to the unmasked bits in the
3877 watchpoint address. The @code{mask} argument implies @code{-location}.
3881 (@value{GDBP}) watch foo mask 0xffff00ff
3882 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
3886 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3887 Set a watchpoint that will break when the value of @var{expr} is read
3891 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3892 Set a watchpoint that will break when @var{expr} is either read from
3893 or written into by the program.
3895 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
3896 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
3897 This command prints a list of watchpoints, using the same format as
3898 @code{info break} (@pxref{Set Breaks}).
3901 If you watch for a change in a numerically entered address you need to
3902 dereference it, as the address itself is just a constant number which will
3903 never change. @value{GDBN} refuses to create a watchpoint that watches
3904 a never-changing value:
3907 (@value{GDBP}) watch 0x600850
3908 Cannot watch constant value 0x600850.
3909 (@value{GDBP}) watch *(int *) 0x600850
3910 Watchpoint 1: *(int *) 6293584
3913 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3914 watchpoints execute very quickly, and the debugger reports a change in
3915 value at the exact instruction where the change occurs. If @value{GDBN}
3916 cannot set a hardware watchpoint, it sets a software watchpoint, which
3917 executes more slowly and reports the change in value at the next
3918 @emph{statement}, not the instruction, after the change occurs.
3920 @cindex use only software watchpoints
3921 You can force @value{GDBN} to use only software watchpoints with the
3922 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3923 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3924 the underlying system supports them. (Note that hardware-assisted
3925 watchpoints that were set @emph{before} setting
3926 @code{can-use-hw-watchpoints} to zero will still use the hardware
3927 mechanism of watching expression values.)
3930 @item set can-use-hw-watchpoints
3931 @kindex set can-use-hw-watchpoints
3932 Set whether or not to use hardware watchpoints.
3934 @item show can-use-hw-watchpoints
3935 @kindex show can-use-hw-watchpoints
3936 Show the current mode of using hardware watchpoints.
3939 For remote targets, you can restrict the number of hardware
3940 watchpoints @value{GDBN} will use, see @ref{set remote
3941 hardware-breakpoint-limit}.
3943 When you issue the @code{watch} command, @value{GDBN} reports
3946 Hardware watchpoint @var{num}: @var{expr}
3950 if it was able to set a hardware watchpoint.
3952 Currently, the @code{awatch} and @code{rwatch} commands can only set
3953 hardware watchpoints, because accesses to data that don't change the
3954 value of the watched expression cannot be detected without examining
3955 every instruction as it is being executed, and @value{GDBN} does not do
3956 that currently. If @value{GDBN} finds that it is unable to set a
3957 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3958 will print a message like this:
3961 Expression cannot be implemented with read/access watchpoint.
3964 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3965 data type of the watched expression is wider than what a hardware
3966 watchpoint on the target machine can handle. For example, some systems
3967 can only watch regions that are up to 4 bytes wide; on such systems you
3968 cannot set hardware watchpoints for an expression that yields a
3969 double-precision floating-point number (which is typically 8 bytes
3970 wide). As a work-around, it might be possible to break the large region
3971 into a series of smaller ones and watch them with separate watchpoints.
3973 If you set too many hardware watchpoints, @value{GDBN} might be unable
3974 to insert all of them when you resume the execution of your program.
3975 Since the precise number of active watchpoints is unknown until such
3976 time as the program is about to be resumed, @value{GDBN} might not be
3977 able to warn you about this when you set the watchpoints, and the
3978 warning will be printed only when the program is resumed:
3981 Hardware watchpoint @var{num}: Could not insert watchpoint
3985 If this happens, delete or disable some of the watchpoints.
3987 Watching complex expressions that reference many variables can also
3988 exhaust the resources available for hardware-assisted watchpoints.
3989 That's because @value{GDBN} needs to watch every variable in the
3990 expression with separately allocated resources.
3992 If you call a function interactively using @code{print} or @code{call},
3993 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3994 kind of breakpoint or the call completes.
3996 @value{GDBN} automatically deletes watchpoints that watch local
3997 (automatic) variables, or expressions that involve such variables, when
3998 they go out of scope, that is, when the execution leaves the block in
3999 which these variables were defined. In particular, when the program
4000 being debugged terminates, @emph{all} local variables go out of scope,
4001 and so only watchpoints that watch global variables remain set. If you
4002 rerun the program, you will need to set all such watchpoints again. One
4003 way of doing that would be to set a code breakpoint at the entry to the
4004 @code{main} function and when it breaks, set all the watchpoints.
4006 @cindex watchpoints and threads
4007 @cindex threads and watchpoints
4008 In multi-threaded programs, watchpoints will detect changes to the
4009 watched expression from every thread.
4012 @emph{Warning:} In multi-threaded programs, software watchpoints
4013 have only limited usefulness. If @value{GDBN} creates a software
4014 watchpoint, it can only watch the value of an expression @emph{in a
4015 single thread}. If you are confident that the expression can only
4016 change due to the current thread's activity (and if you are also
4017 confident that no other thread can become current), then you can use
4018 software watchpoints as usual. However, @value{GDBN} may not notice
4019 when a non-current thread's activity changes the expression. (Hardware
4020 watchpoints, in contrast, watch an expression in all threads.)
4023 @xref{set remote hardware-watchpoint-limit}.
4025 @node Set Catchpoints
4026 @subsection Setting Catchpoints
4027 @cindex catchpoints, setting
4028 @cindex exception handlers
4029 @cindex event handling
4031 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4032 kinds of program events, such as C@t{++} exceptions or the loading of a
4033 shared library. Use the @code{catch} command to set a catchpoint.
4037 @item catch @var{event}
4038 Stop when @var{event} occurs. @var{event} can be any of the following:
4041 @cindex stop on C@t{++} exceptions
4042 The throwing of a C@t{++} exception.
4045 The catching of a C@t{++} exception.
4048 @cindex Ada exception catching
4049 @cindex catch Ada exceptions
4050 An Ada exception being raised. If an exception name is specified
4051 at the end of the command (eg @code{catch exception Program_Error}),
4052 the debugger will stop only when this specific exception is raised.
4053 Otherwise, the debugger stops execution when any Ada exception is raised.
4055 When inserting an exception catchpoint on a user-defined exception whose
4056 name is identical to one of the exceptions defined by the language, the
4057 fully qualified name must be used as the exception name. Otherwise,
4058 @value{GDBN} will assume that it should stop on the pre-defined exception
4059 rather than the user-defined one. For instance, assuming an exception
4060 called @code{Constraint_Error} is defined in package @code{Pck}, then
4061 the command to use to catch such exceptions is @kbd{catch exception
4062 Pck.Constraint_Error}.
4064 @item exception unhandled
4065 An exception that was raised but is not handled by the program.
4068 A failed Ada assertion.
4071 @cindex break on fork/exec
4072 A call to @code{exec}. This is currently only available for HP-UX
4076 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
4077 @cindex break on a system call.
4078 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4079 syscall is a mechanism for application programs to request a service
4080 from the operating system (OS) or one of the OS system services.
4081 @value{GDBN} can catch some or all of the syscalls issued by the
4082 debuggee, and show the related information for each syscall. If no
4083 argument is specified, calls to and returns from all system calls
4086 @var{name} can be any system call name that is valid for the
4087 underlying OS. Just what syscalls are valid depends on the OS. On
4088 GNU and Unix systems, you can find the full list of valid syscall
4089 names on @file{/usr/include/asm/unistd.h}.
4091 @c For MS-Windows, the syscall names and the corresponding numbers
4092 @c can be found, e.g., on this URL:
4093 @c http://www.metasploit.com/users/opcode/syscalls.html
4094 @c but we don't support Windows syscalls yet.
4096 Normally, @value{GDBN} knows in advance which syscalls are valid for
4097 each OS, so you can use the @value{GDBN} command-line completion
4098 facilities (@pxref{Completion,, command completion}) to list the
4101 You may also specify the system call numerically. A syscall's
4102 number is the value passed to the OS's syscall dispatcher to
4103 identify the requested service. When you specify the syscall by its
4104 name, @value{GDBN} uses its database of syscalls to convert the name
4105 into the corresponding numeric code, but using the number directly
4106 may be useful if @value{GDBN}'s database does not have the complete
4107 list of syscalls on your system (e.g., because @value{GDBN} lags
4108 behind the OS upgrades).
4110 The example below illustrates how this command works if you don't provide
4114 (@value{GDBP}) catch syscall
4115 Catchpoint 1 (syscall)
4117 Starting program: /tmp/catch-syscall
4119 Catchpoint 1 (call to syscall 'close'), \
4120 0xffffe424 in __kernel_vsyscall ()
4124 Catchpoint 1 (returned from syscall 'close'), \
4125 0xffffe424 in __kernel_vsyscall ()
4129 Here is an example of catching a system call by name:
4132 (@value{GDBP}) catch syscall chroot
4133 Catchpoint 1 (syscall 'chroot' [61])
4135 Starting program: /tmp/catch-syscall
4137 Catchpoint 1 (call to syscall 'chroot'), \
4138 0xffffe424 in __kernel_vsyscall ()
4142 Catchpoint 1 (returned from syscall 'chroot'), \
4143 0xffffe424 in __kernel_vsyscall ()
4147 An example of specifying a system call numerically. In the case
4148 below, the syscall number has a corresponding entry in the XML
4149 file, so @value{GDBN} finds its name and prints it:
4152 (@value{GDBP}) catch syscall 252
4153 Catchpoint 1 (syscall(s) 'exit_group')
4155 Starting program: /tmp/catch-syscall
4157 Catchpoint 1 (call to syscall 'exit_group'), \
4158 0xffffe424 in __kernel_vsyscall ()
4162 Program exited normally.
4166 However, there can be situations when there is no corresponding name
4167 in XML file for that syscall number. In this case, @value{GDBN} prints
4168 a warning message saying that it was not able to find the syscall name,
4169 but the catchpoint will be set anyway. See the example below:
4172 (@value{GDBP}) catch syscall 764
4173 warning: The number '764' does not represent a known syscall.
4174 Catchpoint 2 (syscall 764)
4178 If you configure @value{GDBN} using the @samp{--without-expat} option,
4179 it will not be able to display syscall names. Also, if your
4180 architecture does not have an XML file describing its system calls,
4181 you will not be able to see the syscall names. It is important to
4182 notice that these two features are used for accessing the syscall
4183 name database. In either case, you will see a warning like this:
4186 (@value{GDBP}) catch syscall
4187 warning: Could not open "syscalls/i386-linux.xml"
4188 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4189 GDB will not be able to display syscall names.
4190 Catchpoint 1 (syscall)
4194 Of course, the file name will change depending on your architecture and system.
4196 Still using the example above, you can also try to catch a syscall by its
4197 number. In this case, you would see something like:
4200 (@value{GDBP}) catch syscall 252
4201 Catchpoint 1 (syscall(s) 252)
4204 Again, in this case @value{GDBN} would not be able to display syscall's names.
4207 A call to @code{fork}. This is currently only available for HP-UX
4211 A call to @code{vfork}. This is currently only available for HP-UX
4214 @item load @r{[}regexp@r{]}
4215 @itemx unload @r{[}regexp@r{]}
4216 The loading or unloading of a shared library. If @var{regexp} is
4217 given, then the catchpoint will stop only if the regular expression
4218 matches one of the affected libraries.
4222 @item tcatch @var{event}
4223 Set a catchpoint that is enabled only for one stop. The catchpoint is
4224 automatically deleted after the first time the event is caught.
4228 Use the @code{info break} command to list the current catchpoints.
4230 There are currently some limitations to C@t{++} exception handling
4231 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4235 If you call a function interactively, @value{GDBN} normally returns
4236 control to you when the function has finished executing. If the call
4237 raises an exception, however, the call may bypass the mechanism that
4238 returns control to you and cause your program either to abort or to
4239 simply continue running until it hits a breakpoint, catches a signal
4240 that @value{GDBN} is listening for, or exits. This is the case even if
4241 you set a catchpoint for the exception; catchpoints on exceptions are
4242 disabled within interactive calls.
4245 You cannot raise an exception interactively.
4248 You cannot install an exception handler interactively.
4251 @cindex raise exceptions
4252 Sometimes @code{catch} is not the best way to debug exception handling:
4253 if you need to know exactly where an exception is raised, it is better to
4254 stop @emph{before} the exception handler is called, since that way you
4255 can see the stack before any unwinding takes place. If you set a
4256 breakpoint in an exception handler instead, it may not be easy to find
4257 out where the exception was raised.
4259 To stop just before an exception handler is called, you need some
4260 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4261 raised by calling a library function named @code{__raise_exception}
4262 which has the following ANSI C interface:
4265 /* @var{addr} is where the exception identifier is stored.
4266 @var{id} is the exception identifier. */
4267 void __raise_exception (void **addr, void *id);
4271 To make the debugger catch all exceptions before any stack
4272 unwinding takes place, set a breakpoint on @code{__raise_exception}
4273 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4275 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4276 that depends on the value of @var{id}, you can stop your program when
4277 a specific exception is raised. You can use multiple conditional
4278 breakpoints to stop your program when any of a number of exceptions are
4283 @subsection Deleting Breakpoints
4285 @cindex clearing breakpoints, watchpoints, catchpoints
4286 @cindex deleting breakpoints, watchpoints, catchpoints
4287 It is often necessary to eliminate a breakpoint, watchpoint, or
4288 catchpoint once it has done its job and you no longer want your program
4289 to stop there. This is called @dfn{deleting} the breakpoint. A
4290 breakpoint that has been deleted no longer exists; it is forgotten.
4292 With the @code{clear} command you can delete breakpoints according to
4293 where they are in your program. With the @code{delete} command you can
4294 delete individual breakpoints, watchpoints, or catchpoints by specifying
4295 their breakpoint numbers.
4297 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4298 automatically ignores breakpoints on the first instruction to be executed
4299 when you continue execution without changing the execution address.
4304 Delete any breakpoints at the next instruction to be executed in the
4305 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4306 the innermost frame is selected, this is a good way to delete a
4307 breakpoint where your program just stopped.
4309 @item clear @var{location}
4310 Delete any breakpoints set at the specified @var{location}.
4311 @xref{Specify Location}, for the various forms of @var{location}; the
4312 most useful ones are listed below:
4315 @item clear @var{function}
4316 @itemx clear @var{filename}:@var{function}
4317 Delete any breakpoints set at entry to the named @var{function}.
4319 @item clear @var{linenum}
4320 @itemx clear @var{filename}:@var{linenum}
4321 Delete any breakpoints set at or within the code of the specified
4322 @var{linenum} of the specified @var{filename}.
4325 @cindex delete breakpoints
4327 @kindex d @r{(@code{delete})}
4328 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4329 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4330 ranges specified as arguments. If no argument is specified, delete all
4331 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4332 confirm off}). You can abbreviate this command as @code{d}.
4336 @subsection Disabling Breakpoints
4338 @cindex enable/disable a breakpoint
4339 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4340 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4341 it had been deleted, but remembers the information on the breakpoint so
4342 that you can @dfn{enable} it again later.
4344 You disable and enable breakpoints, watchpoints, and catchpoints with
4345 the @code{enable} and @code{disable} commands, optionally specifying
4346 one or more breakpoint numbers as arguments. Use @code{info break} to
4347 print a list of all breakpoints, watchpoints, and catchpoints if you
4348 do not know which numbers to use.
4350 Disabling and enabling a breakpoint that has multiple locations
4351 affects all of its locations.
4353 A breakpoint, watchpoint, or catchpoint can have any of several
4354 different states of enablement:
4358 Enabled. The breakpoint stops your program. A breakpoint set
4359 with the @code{break} command starts out in this state.
4361 Disabled. The breakpoint has no effect on your program.
4363 Enabled once. The breakpoint stops your program, but then becomes
4366 Enabled for a count. The breakpoint stops your program for the next
4367 N times, then becomes disabled.
4369 Enabled for deletion. The breakpoint stops your program, but
4370 immediately after it does so it is deleted permanently. A breakpoint
4371 set with the @code{tbreak} command starts out in this state.
4374 You can use the following commands to enable or disable breakpoints,
4375 watchpoints, and catchpoints:
4379 @kindex dis @r{(@code{disable})}
4380 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4381 Disable the specified breakpoints---or all breakpoints, if none are
4382 listed. A disabled breakpoint has no effect but is not forgotten. All
4383 options such as ignore-counts, conditions and commands are remembered in
4384 case the breakpoint is enabled again later. You may abbreviate
4385 @code{disable} as @code{dis}.
4388 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4389 Enable the specified breakpoints (or all defined breakpoints). They
4390 become effective once again in stopping your program.
4392 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4393 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4394 of these breakpoints immediately after stopping your program.
4396 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4397 Enable the specified breakpoints temporarily. @value{GDBN} records
4398 @var{count} with each of the specified breakpoints, and decrements a
4399 breakpoint's count when it is hit. When any count reaches 0,
4400 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4401 count (@pxref{Conditions, ,Break Conditions}), that will be
4402 decremented to 0 before @var{count} is affected.
4404 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4405 Enable the specified breakpoints to work once, then die. @value{GDBN}
4406 deletes any of these breakpoints as soon as your program stops there.
4407 Breakpoints set by the @code{tbreak} command start out in this state.
4410 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4411 @c confusing: tbreak is also initially enabled.
4412 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4413 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4414 subsequently, they become disabled or enabled only when you use one of
4415 the commands above. (The command @code{until} can set and delete a
4416 breakpoint of its own, but it does not change the state of your other
4417 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4421 @subsection Break Conditions
4422 @cindex conditional breakpoints
4423 @cindex breakpoint conditions
4425 @c FIXME what is scope of break condition expr? Context where wanted?
4426 @c in particular for a watchpoint?
4427 The simplest sort of breakpoint breaks every time your program reaches a
4428 specified place. You can also specify a @dfn{condition} for a
4429 breakpoint. A condition is just a Boolean expression in your
4430 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4431 a condition evaluates the expression each time your program reaches it,
4432 and your program stops only if the condition is @emph{true}.
4434 This is the converse of using assertions for program validation; in that
4435 situation, you want to stop when the assertion is violated---that is,
4436 when the condition is false. In C, if you want to test an assertion expressed
4437 by the condition @var{assert}, you should set the condition
4438 @samp{! @var{assert}} on the appropriate breakpoint.
4440 Conditions are also accepted for watchpoints; you may not need them,
4441 since a watchpoint is inspecting the value of an expression anyhow---but
4442 it might be simpler, say, to just set a watchpoint on a variable name,
4443 and specify a condition that tests whether the new value is an interesting
4446 Break conditions can have side effects, and may even call functions in
4447 your program. This can be useful, for example, to activate functions
4448 that log program progress, or to use your own print functions to
4449 format special data structures. The effects are completely predictable
4450 unless there is another enabled breakpoint at the same address. (In
4451 that case, @value{GDBN} might see the other breakpoint first and stop your
4452 program without checking the condition of this one.) Note that
4453 breakpoint commands are usually more convenient and flexible than break
4455 purpose of performing side effects when a breakpoint is reached
4456 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4458 Breakpoint conditions can also be evaluated on the target's side if
4459 the target supports it. Instead of evaluating the conditions locally,
4460 @value{GDBN} encodes the expression into an agent expression
4461 (@pxref{Agent Expressions}) suitable for execution on the target,
4462 independently of @value{GDBN}. Global variables become raw memory
4463 locations, locals become stack accesses, and so forth.
4465 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4466 when its condition evaluates to true. This mechanism may provide faster
4467 response times depending on the performance characteristics of the target
4468 since it does not need to keep @value{GDBN} informed about
4469 every breakpoint trigger, even those with false conditions.
4471 Break conditions can be specified when a breakpoint is set, by using
4472 @samp{if} in the arguments to the @code{break} command. @xref{Set
4473 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4474 with the @code{condition} command.
4476 You can also use the @code{if} keyword with the @code{watch} command.
4477 The @code{catch} command does not recognize the @code{if} keyword;
4478 @code{condition} is the only way to impose a further condition on a
4483 @item condition @var{bnum} @var{expression}
4484 Specify @var{expression} as the break condition for breakpoint,
4485 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4486 breakpoint @var{bnum} stops your program only if the value of
4487 @var{expression} is true (nonzero, in C). When you use
4488 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4489 syntactic correctness, and to determine whether symbols in it have
4490 referents in the context of your breakpoint. If @var{expression} uses
4491 symbols not referenced in the context of the breakpoint, @value{GDBN}
4492 prints an error message:
4495 No symbol "foo" in current context.
4500 not actually evaluate @var{expression} at the time the @code{condition}
4501 command (or a command that sets a breakpoint with a condition, like
4502 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4504 @item condition @var{bnum}
4505 Remove the condition from breakpoint number @var{bnum}. It becomes
4506 an ordinary unconditional breakpoint.
4509 @cindex ignore count (of breakpoint)
4510 A special case of a breakpoint condition is to stop only when the
4511 breakpoint has been reached a certain number of times. This is so
4512 useful that there is a special way to do it, using the @dfn{ignore
4513 count} of the breakpoint. Every breakpoint has an ignore count, which
4514 is an integer. Most of the time, the ignore count is zero, and
4515 therefore has no effect. But if your program reaches a breakpoint whose
4516 ignore count is positive, then instead of stopping, it just decrements
4517 the ignore count by one and continues. As a result, if the ignore count
4518 value is @var{n}, the breakpoint does not stop the next @var{n} times
4519 your program reaches it.
4523 @item ignore @var{bnum} @var{count}
4524 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4525 The next @var{count} times the breakpoint is reached, your program's
4526 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4529 To make the breakpoint stop the next time it is reached, specify
4532 When you use @code{continue} to resume execution of your program from a
4533 breakpoint, you can specify an ignore count directly as an argument to
4534 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4535 Stepping,,Continuing and Stepping}.
4537 If a breakpoint has a positive ignore count and a condition, the
4538 condition is not checked. Once the ignore count reaches zero,
4539 @value{GDBN} resumes checking the condition.
4541 You could achieve the effect of the ignore count with a condition such
4542 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4543 is decremented each time. @xref{Convenience Vars, ,Convenience
4547 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4550 @node Break Commands
4551 @subsection Breakpoint Command Lists
4553 @cindex breakpoint commands
4554 You can give any breakpoint (or watchpoint or catchpoint) a series of
4555 commands to execute when your program stops due to that breakpoint. For
4556 example, you might want to print the values of certain expressions, or
4557 enable other breakpoints.
4561 @kindex end@r{ (breakpoint commands)}
4562 @item commands @r{[}@var{range}@dots{}@r{]}
4563 @itemx @dots{} @var{command-list} @dots{}
4565 Specify a list of commands for the given breakpoints. The commands
4566 themselves appear on the following lines. Type a line containing just
4567 @code{end} to terminate the commands.
4569 To remove all commands from a breakpoint, type @code{commands} and
4570 follow it immediately with @code{end}; that is, give no commands.
4572 With no argument, @code{commands} refers to the last breakpoint,
4573 watchpoint, or catchpoint set (not to the breakpoint most recently
4574 encountered). If the most recent breakpoints were set with a single
4575 command, then the @code{commands} will apply to all the breakpoints
4576 set by that command. This applies to breakpoints set by
4577 @code{rbreak}, and also applies when a single @code{break} command
4578 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4582 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4583 disabled within a @var{command-list}.
4585 You can use breakpoint commands to start your program up again. Simply
4586 use the @code{continue} command, or @code{step}, or any other command
4587 that resumes execution.
4589 Any other commands in the command list, after a command that resumes
4590 execution, are ignored. This is because any time you resume execution
4591 (even with a simple @code{next} or @code{step}), you may encounter
4592 another breakpoint---which could have its own command list, leading to
4593 ambiguities about which list to execute.
4596 If the first command you specify in a command list is @code{silent}, the
4597 usual message about stopping at a breakpoint is not printed. This may
4598 be desirable for breakpoints that are to print a specific message and
4599 then continue. If none of the remaining commands print anything, you
4600 see no sign that the breakpoint was reached. @code{silent} is
4601 meaningful only at the beginning of a breakpoint command list.
4603 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4604 print precisely controlled output, and are often useful in silent
4605 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4607 For example, here is how you could use breakpoint commands to print the
4608 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4614 printf "x is %d\n",x
4619 One application for breakpoint commands is to compensate for one bug so
4620 you can test for another. Put a breakpoint just after the erroneous line
4621 of code, give it a condition to detect the case in which something
4622 erroneous has been done, and give it commands to assign correct values
4623 to any variables that need them. End with the @code{continue} command
4624 so that your program does not stop, and start with the @code{silent}
4625 command so that no output is produced. Here is an example:
4636 @node Dynamic Printf
4637 @subsection Dynamic Printf
4639 @cindex dynamic printf
4641 The dynamic printf command @code{dprintf} combines a breakpoint with
4642 formatted printing of your program's data to give you the effect of
4643 inserting @code{printf} calls into your program on-the-fly, without
4644 having to recompile it.
4646 In its most basic form, the output goes to the GDB console. However,
4647 you can set the variable @code{dprintf-style} for alternate handling.
4648 For instance, you can ask to format the output by calling your
4649 program's @code{printf} function. This has the advantage that the
4650 characters go to the program's output device, so they can recorded in
4651 redirects to files and so forth.
4653 If you are doing remote debugging with a stub or agent, you can also
4654 ask to have the printf handled by the remote agent. In addition to
4655 ensuring that the output goes to the remote program's device along
4656 with any other output the program might produce, you can also ask that
4657 the dprintf remain active even after disconnecting from the remote
4658 target. Using the stub/agent is also more efficient, as it can do
4659 everything without needing to communicate with @value{GDBN}.
4663 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
4664 Whenever execution reaches @var{location}, print the values of one or
4665 more @var{expressions} under the control of the string @var{template}.
4666 To print several values, separate them with commas.
4668 @item set dprintf-style @var{style}
4669 Set the dprintf output to be handled in one of several different
4670 styles enumerated below. A change of style affects all existing
4671 dynamic printfs immediately. (If you need individual control over the
4672 print commands, simply define normal breakpoints with
4673 explicitly-supplied command lists.)
4676 @kindex dprintf-style gdb
4677 Handle the output using the @value{GDBN} @code{printf} command.
4680 @kindex dprintf-style call
4681 Handle the output by calling a function in your program (normally
4685 @kindex dprintf-style agent
4686 Have the remote debugging agent (such as @code{gdbserver}) handle
4687 the output itself. This style is only available for agents that
4688 support running commands on the target.
4690 @item set dprintf-function @var{function}
4691 Set the function to call if the dprintf style is @code{call}. By
4692 default its value is @code{printf}. You may set it to any expression.
4693 that @value{GDBN} can evaluate to a function, as per the @code{call}
4696 @item set dprintf-channel @var{channel}
4697 Set a ``channel'' for dprintf. If set to a non-empty value,
4698 @value{GDBN} will evaluate it as an expression and pass the result as
4699 a first argument to the @code{dprintf-function}, in the manner of
4700 @code{fprintf} and similar functions. Otherwise, the dprintf format
4701 string will be the first argument, in the manner of @code{printf}.
4703 As an example, if you wanted @code{dprintf} output to go to a logfile
4704 that is a standard I/O stream assigned to the variable @code{mylog},
4705 you could do the following:
4708 (gdb) set dprintf-style call
4709 (gdb) set dprintf-function fprintf
4710 (gdb) set dprintf-channel mylog
4711 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
4712 Dprintf 1 at 0x123456: file main.c, line 25.
4714 1 dprintf keep y 0x00123456 in main at main.c:25
4715 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
4720 Note that the @code{info break} displays the dynamic printf commands
4721 as normal breakpoint commands; you can thus easily see the effect of
4722 the variable settings.
4724 @item set disconnected-dprintf on
4725 @itemx set disconnected-dprintf off
4726 @kindex set disconnected-dprintf
4727 Choose whether @code{dprintf} commands should continue to run if
4728 @value{GDBN} has disconnected from the target. This only applies
4729 if the @code{dprintf-style} is @code{agent}.
4731 @item show disconnected-dprintf off
4732 @kindex show disconnected-dprintf
4733 Show the current choice for disconnected @code{dprintf}.
4737 @value{GDBN} does not check the validity of function and channel,
4738 relying on you to supply values that are meaningful for the contexts
4739 in which they are being used. For instance, the function and channel
4740 may be the values of local variables, but if that is the case, then
4741 all enabled dynamic prints must be at locations within the scope of
4742 those locals. If evaluation fails, @value{GDBN} will report an error.
4744 @node Save Breakpoints
4745 @subsection How to save breakpoints to a file
4747 To save breakpoint definitions to a file use the @w{@code{save
4748 breakpoints}} command.
4751 @kindex save breakpoints
4752 @cindex save breakpoints to a file for future sessions
4753 @item save breakpoints [@var{filename}]
4754 This command saves all current breakpoint definitions together with
4755 their commands and ignore counts, into a file @file{@var{filename}}
4756 suitable for use in a later debugging session. This includes all
4757 types of breakpoints (breakpoints, watchpoints, catchpoints,
4758 tracepoints). To read the saved breakpoint definitions, use the
4759 @code{source} command (@pxref{Command Files}). Note that watchpoints
4760 with expressions involving local variables may fail to be recreated
4761 because it may not be possible to access the context where the
4762 watchpoint is valid anymore. Because the saved breakpoint definitions
4763 are simply a sequence of @value{GDBN} commands that recreate the
4764 breakpoints, you can edit the file in your favorite editing program,
4765 and remove the breakpoint definitions you're not interested in, or
4766 that can no longer be recreated.
4769 @node Static Probe Points
4770 @subsection Static Probe Points
4772 @cindex static probe point, SystemTap
4773 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
4774 for Statically Defined Tracing, and the probes are designed to have a tiny
4775 runtime code and data footprint, and no dynamic relocations. They are
4776 usable from assembly, C and C@t{++} languages. See
4777 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
4778 for a good reference on how the @acronym{SDT} probes are implemented.
4780 Currently, @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
4781 @acronym{SDT} probes are supported on ELF-compatible systems. See
4782 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
4783 for more information on how to add @code{SystemTap} @acronym{SDT} probes
4784 in your applications.
4786 @cindex semaphores on static probe points
4787 Some probes have an associated semaphore variable; for instance, this
4788 happens automatically if you defined your probe using a DTrace-style
4789 @file{.d} file. If your probe has a semaphore, @value{GDBN} will
4790 automatically enable it when you specify a breakpoint using the
4791 @samp{-probe-stap} notation. But, if you put a breakpoint at a probe's
4792 location by some other method (e.g., @code{break file:line}), then
4793 @value{GDBN} will not automatically set the semaphore.
4795 You can examine the available static static probes using @code{info
4796 probes}, with optional arguments:
4800 @item info probes stap @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
4801 If given, @var{provider} is a regular expression used to match against provider
4802 names when selecting which probes to list. If omitted, probes by all
4803 probes from all providers are listed.
4805 If given, @var{name} is a regular expression to match against probe names
4806 when selecting which probes to list. If omitted, probe names are not
4807 considered when deciding whether to display them.
4809 If given, @var{objfile} is a regular expression used to select which
4810 object files (executable or shared libraries) to examine. If not
4811 given, all object files are considered.
4813 @item info probes all
4814 List the available static probes, from all types.
4817 @vindex $_probe_arg@r{, convenience variable}
4818 A probe may specify up to twelve arguments. These are available at the
4819 point at which the probe is defined---that is, when the current PC is
4820 at the probe's location. The arguments are available using the
4821 convenience variables (@pxref{Convenience Vars})
4822 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. Each probe argument is
4823 an integer of the appropriate size; types are not preserved. The
4824 convenience variable @code{$_probe_argc} holds the number of arguments
4825 at the current probe point.
4827 These variables are always available, but attempts to access them at
4828 any location other than a probe point will cause @value{GDBN} to give
4832 @c @ifclear BARETARGET
4833 @node Error in Breakpoints
4834 @subsection ``Cannot insert breakpoints''
4836 If you request too many active hardware-assisted breakpoints and
4837 watchpoints, you will see this error message:
4839 @c FIXME: the precise wording of this message may change; the relevant
4840 @c source change is not committed yet (Sep 3, 1999).
4842 Stopped; cannot insert breakpoints.
4843 You may have requested too many hardware breakpoints and watchpoints.
4847 This message is printed when you attempt to resume the program, since
4848 only then @value{GDBN} knows exactly how many hardware breakpoints and
4849 watchpoints it needs to insert.
4851 When this message is printed, you need to disable or remove some of the
4852 hardware-assisted breakpoints and watchpoints, and then continue.
4854 @node Breakpoint-related Warnings
4855 @subsection ``Breakpoint address adjusted...''
4856 @cindex breakpoint address adjusted
4858 Some processor architectures place constraints on the addresses at
4859 which breakpoints may be placed. For architectures thus constrained,
4860 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4861 with the constraints dictated by the architecture.
4863 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4864 a VLIW architecture in which a number of RISC-like instructions may be
4865 bundled together for parallel execution. The FR-V architecture
4866 constrains the location of a breakpoint instruction within such a
4867 bundle to the instruction with the lowest address. @value{GDBN}
4868 honors this constraint by adjusting a breakpoint's address to the
4869 first in the bundle.
4871 It is not uncommon for optimized code to have bundles which contain
4872 instructions from different source statements, thus it may happen that
4873 a breakpoint's address will be adjusted from one source statement to
4874 another. Since this adjustment may significantly alter @value{GDBN}'s
4875 breakpoint related behavior from what the user expects, a warning is
4876 printed when the breakpoint is first set and also when the breakpoint
4879 A warning like the one below is printed when setting a breakpoint
4880 that's been subject to address adjustment:
4883 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4886 Such warnings are printed both for user settable and @value{GDBN}'s
4887 internal breakpoints. If you see one of these warnings, you should
4888 verify that a breakpoint set at the adjusted address will have the
4889 desired affect. If not, the breakpoint in question may be removed and
4890 other breakpoints may be set which will have the desired behavior.
4891 E.g., it may be sufficient to place the breakpoint at a later
4892 instruction. A conditional breakpoint may also be useful in some
4893 cases to prevent the breakpoint from triggering too often.
4895 @value{GDBN} will also issue a warning when stopping at one of these
4896 adjusted breakpoints:
4899 warning: Breakpoint 1 address previously adjusted from 0x00010414
4903 When this warning is encountered, it may be too late to take remedial
4904 action except in cases where the breakpoint is hit earlier or more
4905 frequently than expected.
4907 @node Continuing and Stepping
4908 @section Continuing and Stepping
4912 @cindex resuming execution
4913 @dfn{Continuing} means resuming program execution until your program
4914 completes normally. In contrast, @dfn{stepping} means executing just
4915 one more ``step'' of your program, where ``step'' may mean either one
4916 line of source code, or one machine instruction (depending on what
4917 particular command you use). Either when continuing or when stepping,
4918 your program may stop even sooner, due to a breakpoint or a signal. (If
4919 it stops due to a signal, you may want to use @code{handle}, or use
4920 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4924 @kindex c @r{(@code{continue})}
4925 @kindex fg @r{(resume foreground execution)}
4926 @item continue @r{[}@var{ignore-count}@r{]}
4927 @itemx c @r{[}@var{ignore-count}@r{]}
4928 @itemx fg @r{[}@var{ignore-count}@r{]}
4929 Resume program execution, at the address where your program last stopped;
4930 any breakpoints set at that address are bypassed. The optional argument
4931 @var{ignore-count} allows you to specify a further number of times to
4932 ignore a breakpoint at this location; its effect is like that of
4933 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4935 The argument @var{ignore-count} is meaningful only when your program
4936 stopped due to a breakpoint. At other times, the argument to
4937 @code{continue} is ignored.
4939 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4940 debugged program is deemed to be the foreground program) are provided
4941 purely for convenience, and have exactly the same behavior as
4945 To resume execution at a different place, you can use @code{return}
4946 (@pxref{Returning, ,Returning from a Function}) to go back to the
4947 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4948 Different Address}) to go to an arbitrary location in your program.
4950 A typical technique for using stepping is to set a breakpoint
4951 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4952 beginning of the function or the section of your program where a problem
4953 is believed to lie, run your program until it stops at that breakpoint,
4954 and then step through the suspect area, examining the variables that are
4955 interesting, until you see the problem happen.
4959 @kindex s @r{(@code{step})}
4961 Continue running your program until control reaches a different source
4962 line, then stop it and return control to @value{GDBN}. This command is
4963 abbreviated @code{s}.
4966 @c "without debugging information" is imprecise; actually "without line
4967 @c numbers in the debugging information". (gcc -g1 has debugging info but
4968 @c not line numbers). But it seems complex to try to make that
4969 @c distinction here.
4970 @emph{Warning:} If you use the @code{step} command while control is
4971 within a function that was compiled without debugging information,
4972 execution proceeds until control reaches a function that does have
4973 debugging information. Likewise, it will not step into a function which
4974 is compiled without debugging information. To step through functions
4975 without debugging information, use the @code{stepi} command, described
4979 The @code{step} command only stops at the first instruction of a source
4980 line. This prevents the multiple stops that could otherwise occur in
4981 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4982 to stop if a function that has debugging information is called within
4983 the line. In other words, @code{step} @emph{steps inside} any functions
4984 called within the line.
4986 Also, the @code{step} command only enters a function if there is line
4987 number information for the function. Otherwise it acts like the
4988 @code{next} command. This avoids problems when using @code{cc -gl}
4989 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
4990 was any debugging information about the routine.
4992 @item step @var{count}
4993 Continue running as in @code{step}, but do so @var{count} times. If a
4994 breakpoint is reached, or a signal not related to stepping occurs before
4995 @var{count} steps, stepping stops right away.
4998 @kindex n @r{(@code{next})}
4999 @item next @r{[}@var{count}@r{]}
5000 Continue to the next source line in the current (innermost) stack frame.
5001 This is similar to @code{step}, but function calls that appear within
5002 the line of code are executed without stopping. Execution stops when
5003 control reaches a different line of code at the original stack level
5004 that was executing when you gave the @code{next} command. This command
5005 is abbreviated @code{n}.
5007 An argument @var{count} is a repeat count, as for @code{step}.
5010 @c FIX ME!! Do we delete this, or is there a way it fits in with
5011 @c the following paragraph? --- Vctoria
5013 @c @code{next} within a function that lacks debugging information acts like
5014 @c @code{step}, but any function calls appearing within the code of the
5015 @c function are executed without stopping.
5017 The @code{next} command only stops at the first instruction of a
5018 source line. This prevents multiple stops that could otherwise occur in
5019 @code{switch} statements, @code{for} loops, etc.
5021 @kindex set step-mode
5023 @cindex functions without line info, and stepping
5024 @cindex stepping into functions with no line info
5025 @itemx set step-mode on
5026 The @code{set step-mode on} command causes the @code{step} command to
5027 stop at the first instruction of a function which contains no debug line
5028 information rather than stepping over it.
5030 This is useful in cases where you may be interested in inspecting the
5031 machine instructions of a function which has no symbolic info and do not
5032 want @value{GDBN} to automatically skip over this function.
5034 @item set step-mode off
5035 Causes the @code{step} command to step over any functions which contains no
5036 debug information. This is the default.
5038 @item show step-mode
5039 Show whether @value{GDBN} will stop in or step over functions without
5040 source line debug information.
5043 @kindex fin @r{(@code{finish})}
5045 Continue running until just after function in the selected stack frame
5046 returns. Print the returned value (if any). This command can be
5047 abbreviated as @code{fin}.
5049 Contrast this with the @code{return} command (@pxref{Returning,
5050 ,Returning from a Function}).
5053 @kindex u @r{(@code{until})}
5054 @cindex run until specified location
5057 Continue running until a source line past the current line, in the
5058 current stack frame, is reached. This command is used to avoid single
5059 stepping through a loop more than once. It is like the @code{next}
5060 command, except that when @code{until} encounters a jump, it
5061 automatically continues execution until the program counter is greater
5062 than the address of the jump.
5064 This means that when you reach the end of a loop after single stepping
5065 though it, @code{until} makes your program continue execution until it
5066 exits the loop. In contrast, a @code{next} command at the end of a loop
5067 simply steps back to the beginning of the loop, which forces you to step
5068 through the next iteration.
5070 @code{until} always stops your program if it attempts to exit the current
5073 @code{until} may produce somewhat counterintuitive results if the order
5074 of machine code does not match the order of the source lines. For
5075 example, in the following excerpt from a debugging session, the @code{f}
5076 (@code{frame}) command shows that execution is stopped at line
5077 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5081 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5083 (@value{GDBP}) until
5084 195 for ( ; argc > 0; NEXTARG) @{
5087 This happened because, for execution efficiency, the compiler had
5088 generated code for the loop closure test at the end, rather than the
5089 start, of the loop---even though the test in a C @code{for}-loop is
5090 written before the body of the loop. The @code{until} command appeared
5091 to step back to the beginning of the loop when it advanced to this
5092 expression; however, it has not really gone to an earlier
5093 statement---not in terms of the actual machine code.
5095 @code{until} with no argument works by means of single
5096 instruction stepping, and hence is slower than @code{until} with an
5099 @item until @var{location}
5100 @itemx u @var{location}
5101 Continue running your program until either the specified location is
5102 reached, or the current stack frame returns. @var{location} is any of
5103 the forms described in @ref{Specify Location}.
5104 This form of the command uses temporary breakpoints, and
5105 hence is quicker than @code{until} without an argument. The specified
5106 location is actually reached only if it is in the current frame. This
5107 implies that @code{until} can be used to skip over recursive function
5108 invocations. For instance in the code below, if the current location is
5109 line @code{96}, issuing @code{until 99} will execute the program up to
5110 line @code{99} in the same invocation of factorial, i.e., after the inner
5111 invocations have returned.
5114 94 int factorial (int value)
5116 96 if (value > 1) @{
5117 97 value *= factorial (value - 1);
5124 @kindex advance @var{location}
5125 @item advance @var{location}
5126 Continue running the program up to the given @var{location}. An argument is
5127 required, which should be of one of the forms described in
5128 @ref{Specify Location}.
5129 Execution will also stop upon exit from the current stack
5130 frame. This command is similar to @code{until}, but @code{advance} will
5131 not skip over recursive function calls, and the target location doesn't
5132 have to be in the same frame as the current one.
5136 @kindex si @r{(@code{stepi})}
5138 @itemx stepi @var{arg}
5140 Execute one machine instruction, then stop and return to the debugger.
5142 It is often useful to do @samp{display/i $pc} when stepping by machine
5143 instructions. This makes @value{GDBN} automatically display the next
5144 instruction to be executed, each time your program stops. @xref{Auto
5145 Display,, Automatic Display}.
5147 An argument is a repeat count, as in @code{step}.
5151 @kindex ni @r{(@code{nexti})}
5153 @itemx nexti @var{arg}
5155 Execute one machine instruction, but if it is a function call,
5156 proceed until the function returns.
5158 An argument is a repeat count, as in @code{next}.
5161 @node Skipping Over Functions and Files
5162 @section Skipping Over Functions and Files
5163 @cindex skipping over functions and files
5165 The program you are debugging may contain some functions which are
5166 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
5167 skip a function or all functions in a file when stepping.
5169 For example, consider the following C function:
5180 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5181 are not interested in stepping through @code{boring}. If you run @code{step}
5182 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5183 step over both @code{foo} and @code{boring}!
5185 One solution is to @code{step} into @code{boring} and use the @code{finish}
5186 command to immediately exit it. But this can become tedious if @code{boring}
5187 is called from many places.
5189 A more flexible solution is to execute @kbd{skip boring}. This instructs
5190 @value{GDBN} never to step into @code{boring}. Now when you execute
5191 @code{step} at line 103, you'll step over @code{boring} and directly into
5194 You can also instruct @value{GDBN} to skip all functions in a file, with, for
5195 example, @code{skip file boring.c}.
5198 @kindex skip function
5199 @item skip @r{[}@var{linespec}@r{]}
5200 @itemx skip function @r{[}@var{linespec}@r{]}
5201 After running this command, the function named by @var{linespec} or the
5202 function containing the line named by @var{linespec} will be skipped over when
5203 stepping. @xref{Specify Location}.
5205 If you do not specify @var{linespec}, the function you're currently debugging
5208 (If you have a function called @code{file} that you want to skip, use
5209 @kbd{skip function file}.)
5212 @item skip file @r{[}@var{filename}@r{]}
5213 After running this command, any function whose source lives in @var{filename}
5214 will be skipped over when stepping.
5216 If you do not specify @var{filename}, functions whose source lives in the file
5217 you're currently debugging will be skipped.
5220 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5221 These are the commands for managing your list of skips:
5225 @item info skip @r{[}@var{range}@r{]}
5226 Print details about the specified skip(s). If @var{range} is not specified,
5227 print a table with details about all functions and files marked for skipping.
5228 @code{info skip} prints the following information about each skip:
5232 A number identifying this skip.
5234 The type of this skip, either @samp{function} or @samp{file}.
5235 @item Enabled or Disabled
5236 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
5238 For function skips, this column indicates the address in memory of the function
5239 being skipped. If you've set a function skip on a function which has not yet
5240 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
5241 which has the function is loaded, @code{info skip} will show the function's
5244 For file skips, this field contains the filename being skipped. For functions
5245 skips, this field contains the function name and its line number in the file
5246 where it is defined.
5250 @item skip delete @r{[}@var{range}@r{]}
5251 Delete the specified skip(s). If @var{range} is not specified, delete all
5255 @item skip enable @r{[}@var{range}@r{]}
5256 Enable the specified skip(s). If @var{range} is not specified, enable all
5259 @kindex skip disable
5260 @item skip disable @r{[}@var{range}@r{]}
5261 Disable the specified skip(s). If @var{range} is not specified, disable all
5270 A signal is an asynchronous event that can happen in a program. The
5271 operating system defines the possible kinds of signals, and gives each
5272 kind a name and a number. For example, in Unix @code{SIGINT} is the
5273 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5274 @code{SIGSEGV} is the signal a program gets from referencing a place in
5275 memory far away from all the areas in use; @code{SIGALRM} occurs when
5276 the alarm clock timer goes off (which happens only if your program has
5277 requested an alarm).
5279 @cindex fatal signals
5280 Some signals, including @code{SIGALRM}, are a normal part of the
5281 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5282 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5283 program has not specified in advance some other way to handle the signal.
5284 @code{SIGINT} does not indicate an error in your program, but it is normally
5285 fatal so it can carry out the purpose of the interrupt: to kill the program.
5287 @value{GDBN} has the ability to detect any occurrence of a signal in your
5288 program. You can tell @value{GDBN} in advance what to do for each kind of
5291 @cindex handling signals
5292 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5293 @code{SIGALRM} be silently passed to your program
5294 (so as not to interfere with their role in the program's functioning)
5295 but to stop your program immediately whenever an error signal happens.
5296 You can change these settings with the @code{handle} command.
5299 @kindex info signals
5303 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5304 handle each one. You can use this to see the signal numbers of all
5305 the defined types of signals.
5307 @item info signals @var{sig}
5308 Similar, but print information only about the specified signal number.
5310 @code{info handle} is an alias for @code{info signals}.
5313 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5314 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
5315 can be the number of a signal or its name (with or without the
5316 @samp{SIG} at the beginning); a list of signal numbers of the form
5317 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5318 known signals. Optional arguments @var{keywords}, described below,
5319 say what change to make.
5323 The keywords allowed by the @code{handle} command can be abbreviated.
5324 Their full names are:
5328 @value{GDBN} should not stop your program when this signal happens. It may
5329 still print a message telling you that the signal has come in.
5332 @value{GDBN} should stop your program when this signal happens. This implies
5333 the @code{print} keyword as well.
5336 @value{GDBN} should print a message when this signal happens.
5339 @value{GDBN} should not mention the occurrence of the signal at all. This
5340 implies the @code{nostop} keyword as well.
5344 @value{GDBN} should allow your program to see this signal; your program
5345 can handle the signal, or else it may terminate if the signal is fatal
5346 and not handled. @code{pass} and @code{noignore} are synonyms.
5350 @value{GDBN} should not allow your program to see this signal.
5351 @code{nopass} and @code{ignore} are synonyms.
5355 When a signal stops your program, the signal is not visible to the
5357 continue. Your program sees the signal then, if @code{pass} is in
5358 effect for the signal in question @emph{at that time}. In other words,
5359 after @value{GDBN} reports a signal, you can use the @code{handle}
5360 command with @code{pass} or @code{nopass} to control whether your
5361 program sees that signal when you continue.
5363 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5364 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5365 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5368 You can also use the @code{signal} command to prevent your program from
5369 seeing a signal, or cause it to see a signal it normally would not see,
5370 or to give it any signal at any time. For example, if your program stopped
5371 due to some sort of memory reference error, you might store correct
5372 values into the erroneous variables and continue, hoping to see more
5373 execution; but your program would probably terminate immediately as
5374 a result of the fatal signal once it saw the signal. To prevent this,
5375 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5378 @cindex extra signal information
5379 @anchor{extra signal information}
5381 On some targets, @value{GDBN} can inspect extra signal information
5382 associated with the intercepted signal, before it is actually
5383 delivered to the program being debugged. This information is exported
5384 by the convenience variable @code{$_siginfo}, and consists of data
5385 that is passed by the kernel to the signal handler at the time of the
5386 receipt of a signal. The data type of the information itself is
5387 target dependent. You can see the data type using the @code{ptype
5388 $_siginfo} command. On Unix systems, it typically corresponds to the
5389 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5392 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5393 referenced address that raised a segmentation fault.
5397 (@value{GDBP}) continue
5398 Program received signal SIGSEGV, Segmentation fault.
5399 0x0000000000400766 in main ()
5401 (@value{GDBP}) ptype $_siginfo
5408 struct @{...@} _kill;
5409 struct @{...@} _timer;
5411 struct @{...@} _sigchld;
5412 struct @{...@} _sigfault;
5413 struct @{...@} _sigpoll;
5416 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5420 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5421 $1 = (void *) 0x7ffff7ff7000
5425 Depending on target support, @code{$_siginfo} may also be writable.
5428 @section Stopping and Starting Multi-thread Programs
5430 @cindex stopped threads
5431 @cindex threads, stopped
5433 @cindex continuing threads
5434 @cindex threads, continuing
5436 @value{GDBN} supports debugging programs with multiple threads
5437 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5438 are two modes of controlling execution of your program within the
5439 debugger. In the default mode, referred to as @dfn{all-stop mode},
5440 when any thread in your program stops (for example, at a breakpoint
5441 or while being stepped), all other threads in the program are also stopped by
5442 @value{GDBN}. On some targets, @value{GDBN} also supports
5443 @dfn{non-stop mode}, in which other threads can continue to run freely while
5444 you examine the stopped thread in the debugger.
5447 * All-Stop Mode:: All threads stop when GDB takes control
5448 * Non-Stop Mode:: Other threads continue to execute
5449 * Background Execution:: Running your program asynchronously
5450 * Thread-Specific Breakpoints:: Controlling breakpoints
5451 * Interrupted System Calls:: GDB may interfere with system calls
5452 * Observer Mode:: GDB does not alter program behavior
5456 @subsection All-Stop Mode
5458 @cindex all-stop mode
5460 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5461 @emph{all} threads of execution stop, not just the current thread. This
5462 allows you to examine the overall state of the program, including
5463 switching between threads, without worrying that things may change
5466 Conversely, whenever you restart the program, @emph{all} threads start
5467 executing. @emph{This is true even when single-stepping} with commands
5468 like @code{step} or @code{next}.
5470 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5471 Since thread scheduling is up to your debugging target's operating
5472 system (not controlled by @value{GDBN}), other threads may
5473 execute more than one statement while the current thread completes a
5474 single step. Moreover, in general other threads stop in the middle of a
5475 statement, rather than at a clean statement boundary, when the program
5478 You might even find your program stopped in another thread after
5479 continuing or even single-stepping. This happens whenever some other
5480 thread runs into a breakpoint, a signal, or an exception before the
5481 first thread completes whatever you requested.
5483 @cindex automatic thread selection
5484 @cindex switching threads automatically
5485 @cindex threads, automatic switching
5486 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5487 signal, it automatically selects the thread where that breakpoint or
5488 signal happened. @value{GDBN} alerts you to the context switch with a
5489 message such as @samp{[Switching to Thread @var{n}]} to identify the
5492 On some OSes, you can modify @value{GDBN}'s default behavior by
5493 locking the OS scheduler to allow only a single thread to run.
5496 @item set scheduler-locking @var{mode}
5497 @cindex scheduler locking mode
5498 @cindex lock scheduler
5499 Set the scheduler locking mode. If it is @code{off}, then there is no
5500 locking and any thread may run at any time. If @code{on}, then only the
5501 current thread may run when the inferior is resumed. The @code{step}
5502 mode optimizes for single-stepping; it prevents other threads
5503 from preempting the current thread while you are stepping, so that
5504 the focus of debugging does not change unexpectedly.
5505 Other threads only rarely (or never) get a chance to run
5506 when you step. They are more likely to run when you @samp{next} over a
5507 function call, and they are completely free to run when you use commands
5508 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5509 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5510 the current thread away from the thread that you are debugging.
5512 @item show scheduler-locking
5513 Display the current scheduler locking mode.
5516 @cindex resume threads of multiple processes simultaneously
5517 By default, when you issue one of the execution commands such as
5518 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5519 threads of the current inferior to run. For example, if @value{GDBN}
5520 is attached to two inferiors, each with two threads, the
5521 @code{continue} command resumes only the two threads of the current
5522 inferior. This is useful, for example, when you debug a program that
5523 forks and you want to hold the parent stopped (so that, for instance,
5524 it doesn't run to exit), while you debug the child. In other
5525 situations, you may not be interested in inspecting the current state
5526 of any of the processes @value{GDBN} is attached to, and you may want
5527 to resume them all until some breakpoint is hit. In the latter case,
5528 you can instruct @value{GDBN} to allow all threads of all the
5529 inferiors to run with the @w{@code{set schedule-multiple}} command.
5532 @kindex set schedule-multiple
5533 @item set schedule-multiple
5534 Set the mode for allowing threads of multiple processes to be resumed
5535 when an execution command is issued. When @code{on}, all threads of
5536 all processes are allowed to run. When @code{off}, only the threads
5537 of the current process are resumed. The default is @code{off}. The
5538 @code{scheduler-locking} mode takes precedence when set to @code{on},
5539 or while you are stepping and set to @code{step}.
5541 @item show schedule-multiple
5542 Display the current mode for resuming the execution of threads of
5547 @subsection Non-Stop Mode
5549 @cindex non-stop mode
5551 @c This section is really only a place-holder, and needs to be expanded
5552 @c with more details.
5554 For some multi-threaded targets, @value{GDBN} supports an optional
5555 mode of operation in which you can examine stopped program threads in
5556 the debugger while other threads continue to execute freely. This
5557 minimizes intrusion when debugging live systems, such as programs
5558 where some threads have real-time constraints or must continue to
5559 respond to external events. This is referred to as @dfn{non-stop} mode.
5561 In non-stop mode, when a thread stops to report a debugging event,
5562 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5563 threads as well, in contrast to the all-stop mode behavior. Additionally,
5564 execution commands such as @code{continue} and @code{step} apply by default
5565 only to the current thread in non-stop mode, rather than all threads as
5566 in all-stop mode. This allows you to control threads explicitly in
5567 ways that are not possible in all-stop mode --- for example, stepping
5568 one thread while allowing others to run freely, stepping
5569 one thread while holding all others stopped, or stepping several threads
5570 independently and simultaneously.
5572 To enter non-stop mode, use this sequence of commands before you run
5573 or attach to your program:
5576 # Enable the async interface.
5579 # If using the CLI, pagination breaks non-stop.
5582 # Finally, turn it on!
5586 You can use these commands to manipulate the non-stop mode setting:
5589 @kindex set non-stop
5590 @item set non-stop on
5591 Enable selection of non-stop mode.
5592 @item set non-stop off
5593 Disable selection of non-stop mode.
5594 @kindex show non-stop
5596 Show the current non-stop enablement setting.
5599 Note these commands only reflect whether non-stop mode is enabled,
5600 not whether the currently-executing program is being run in non-stop mode.
5601 In particular, the @code{set non-stop} preference is only consulted when
5602 @value{GDBN} starts or connects to the target program, and it is generally
5603 not possible to switch modes once debugging has started. Furthermore,
5604 since not all targets support non-stop mode, even when you have enabled
5605 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5608 In non-stop mode, all execution commands apply only to the current thread
5609 by default. That is, @code{continue} only continues one thread.
5610 To continue all threads, issue @code{continue -a} or @code{c -a}.
5612 You can use @value{GDBN}'s background execution commands
5613 (@pxref{Background Execution}) to run some threads in the background
5614 while you continue to examine or step others from @value{GDBN}.
5615 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5616 always executed asynchronously in non-stop mode.
5618 Suspending execution is done with the @code{interrupt} command when
5619 running in the background, or @kbd{Ctrl-c} during foreground execution.
5620 In all-stop mode, this stops the whole process;
5621 but in non-stop mode the interrupt applies only to the current thread.
5622 To stop the whole program, use @code{interrupt -a}.
5624 Other execution commands do not currently support the @code{-a} option.
5626 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5627 that thread current, as it does in all-stop mode. This is because the
5628 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5629 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5630 changed to a different thread just as you entered a command to operate on the
5631 previously current thread.
5633 @node Background Execution
5634 @subsection Background Execution
5636 @cindex foreground execution
5637 @cindex background execution
5638 @cindex asynchronous execution
5639 @cindex execution, foreground, background and asynchronous
5641 @value{GDBN}'s execution commands have two variants: the normal
5642 foreground (synchronous) behavior, and a background
5643 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5644 the program to report that some thread has stopped before prompting for
5645 another command. In background execution, @value{GDBN} immediately gives
5646 a command prompt so that you can issue other commands while your program runs.
5648 You need to explicitly enable asynchronous mode before you can use
5649 background execution commands. You can use these commands to
5650 manipulate the asynchronous mode setting:
5653 @kindex set target-async
5654 @item set target-async on
5655 Enable asynchronous mode.
5656 @item set target-async off
5657 Disable asynchronous mode.
5658 @kindex show target-async
5659 @item show target-async
5660 Show the current target-async setting.
5663 If the target doesn't support async mode, @value{GDBN} issues an error
5664 message if you attempt to use the background execution commands.
5666 To specify background execution, add a @code{&} to the command. For example,
5667 the background form of the @code{continue} command is @code{continue&}, or
5668 just @code{c&}. The execution commands that accept background execution
5674 @xref{Starting, , Starting your Program}.
5678 @xref{Attach, , Debugging an Already-running Process}.
5682 @xref{Continuing and Stepping, step}.
5686 @xref{Continuing and Stepping, stepi}.
5690 @xref{Continuing and Stepping, next}.
5694 @xref{Continuing and Stepping, nexti}.
5698 @xref{Continuing and Stepping, continue}.
5702 @xref{Continuing and Stepping, finish}.
5706 @xref{Continuing and Stepping, until}.
5710 Background execution is especially useful in conjunction with non-stop
5711 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5712 However, you can also use these commands in the normal all-stop mode with
5713 the restriction that you cannot issue another execution command until the
5714 previous one finishes. Examples of commands that are valid in all-stop
5715 mode while the program is running include @code{help} and @code{info break}.
5717 You can interrupt your program while it is running in the background by
5718 using the @code{interrupt} command.
5725 Suspend execution of the running program. In all-stop mode,
5726 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5727 only the current thread. To stop the whole program in non-stop mode,
5728 use @code{interrupt -a}.
5731 @node Thread-Specific Breakpoints
5732 @subsection Thread-Specific Breakpoints
5734 When your program has multiple threads (@pxref{Threads,, Debugging
5735 Programs with Multiple Threads}), you can choose whether to set
5736 breakpoints on all threads, or on a particular thread.
5739 @cindex breakpoints and threads
5740 @cindex thread breakpoints
5741 @kindex break @dots{} thread @var{threadno}
5742 @item break @var{linespec} thread @var{threadno}
5743 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5744 @var{linespec} specifies source lines; there are several ways of
5745 writing them (@pxref{Specify Location}), but the effect is always to
5746 specify some source line.
5748 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5749 to specify that you only want @value{GDBN} to stop the program when a
5750 particular thread reaches this breakpoint. @var{threadno} is one of the
5751 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5752 column of the @samp{info threads} display.
5754 If you do not specify @samp{thread @var{threadno}} when you set a
5755 breakpoint, the breakpoint applies to @emph{all} threads of your
5758 You can use the @code{thread} qualifier on conditional breakpoints as
5759 well; in this case, place @samp{thread @var{threadno}} before or
5760 after the breakpoint condition, like this:
5763 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5768 @node Interrupted System Calls
5769 @subsection Interrupted System Calls
5771 @cindex thread breakpoints and system calls
5772 @cindex system calls and thread breakpoints
5773 @cindex premature return from system calls
5774 There is an unfortunate side effect when using @value{GDBN} to debug
5775 multi-threaded programs. If one thread stops for a
5776 breakpoint, or for some other reason, and another thread is blocked in a
5777 system call, then the system call may return prematurely. This is a
5778 consequence of the interaction between multiple threads and the signals
5779 that @value{GDBN} uses to implement breakpoints and other events that
5782 To handle this problem, your program should check the return value of
5783 each system call and react appropriately. This is good programming
5786 For example, do not write code like this:
5792 The call to @code{sleep} will return early if a different thread stops
5793 at a breakpoint or for some other reason.
5795 Instead, write this:
5800 unslept = sleep (unslept);
5803 A system call is allowed to return early, so the system is still
5804 conforming to its specification. But @value{GDBN} does cause your
5805 multi-threaded program to behave differently than it would without
5808 Also, @value{GDBN} uses internal breakpoints in the thread library to
5809 monitor certain events such as thread creation and thread destruction.
5810 When such an event happens, a system call in another thread may return
5811 prematurely, even though your program does not appear to stop.
5814 @subsection Observer Mode
5816 If you want to build on non-stop mode and observe program behavior
5817 without any chance of disruption by @value{GDBN}, you can set
5818 variables to disable all of the debugger's attempts to modify state,
5819 whether by writing memory, inserting breakpoints, etc. These operate
5820 at a low level, intercepting operations from all commands.
5822 When all of these are set to @code{off}, then @value{GDBN} is said to
5823 be @dfn{observer mode}. As a convenience, the variable
5824 @code{observer} can be set to disable these, plus enable non-stop
5827 Note that @value{GDBN} will not prevent you from making nonsensical
5828 combinations of these settings. For instance, if you have enabled
5829 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5830 then breakpoints that work by writing trap instructions into the code
5831 stream will still not be able to be placed.
5836 @item set observer on
5837 @itemx set observer off
5838 When set to @code{on}, this disables all the permission variables
5839 below (except for @code{insert-fast-tracepoints}), plus enables
5840 non-stop debugging. Setting this to @code{off} switches back to
5841 normal debugging, though remaining in non-stop mode.
5844 Show whether observer mode is on or off.
5846 @kindex may-write-registers
5847 @item set may-write-registers on
5848 @itemx set may-write-registers off
5849 This controls whether @value{GDBN} will attempt to alter the values of
5850 registers, such as with assignment expressions in @code{print}, or the
5851 @code{jump} command. It defaults to @code{on}.
5853 @item show may-write-registers
5854 Show the current permission to write registers.
5856 @kindex may-write-memory
5857 @item set may-write-memory on
5858 @itemx set may-write-memory off
5859 This controls whether @value{GDBN} will attempt to alter the contents
5860 of memory, such as with assignment expressions in @code{print}. It
5861 defaults to @code{on}.
5863 @item show may-write-memory
5864 Show the current permission to write memory.
5866 @kindex may-insert-breakpoints
5867 @item set may-insert-breakpoints on
5868 @itemx set may-insert-breakpoints off
5869 This controls whether @value{GDBN} will attempt to insert breakpoints.
5870 This affects all breakpoints, including internal breakpoints defined
5871 by @value{GDBN}. It defaults to @code{on}.
5873 @item show may-insert-breakpoints
5874 Show the current permission to insert breakpoints.
5876 @kindex may-insert-tracepoints
5877 @item set may-insert-tracepoints on
5878 @itemx set may-insert-tracepoints off
5879 This controls whether @value{GDBN} will attempt to insert (regular)
5880 tracepoints at the beginning of a tracing experiment. It affects only
5881 non-fast tracepoints, fast tracepoints being under the control of
5882 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5884 @item show may-insert-tracepoints
5885 Show the current permission to insert tracepoints.
5887 @kindex may-insert-fast-tracepoints
5888 @item set may-insert-fast-tracepoints on
5889 @itemx set may-insert-fast-tracepoints off
5890 This controls whether @value{GDBN} will attempt to insert fast
5891 tracepoints at the beginning of a tracing experiment. It affects only
5892 fast tracepoints, regular (non-fast) tracepoints being under the
5893 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5895 @item show may-insert-fast-tracepoints
5896 Show the current permission to insert fast tracepoints.
5898 @kindex may-interrupt
5899 @item set may-interrupt on
5900 @itemx set may-interrupt off
5901 This controls whether @value{GDBN} will attempt to interrupt or stop
5902 program execution. When this variable is @code{off}, the
5903 @code{interrupt} command will have no effect, nor will
5904 @kbd{Ctrl-c}. It defaults to @code{on}.
5906 @item show may-interrupt
5907 Show the current permission to interrupt or stop the program.
5911 @node Reverse Execution
5912 @chapter Running programs backward
5913 @cindex reverse execution
5914 @cindex running programs backward
5916 When you are debugging a program, it is not unusual to realize that
5917 you have gone too far, and some event of interest has already happened.
5918 If the target environment supports it, @value{GDBN} can allow you to
5919 ``rewind'' the program by running it backward.
5921 A target environment that supports reverse execution should be able
5922 to ``undo'' the changes in machine state that have taken place as the
5923 program was executing normally. Variables, registers etc.@: should
5924 revert to their previous values. Obviously this requires a great
5925 deal of sophistication on the part of the target environment; not
5926 all target environments can support reverse execution.
5928 When a program is executed in reverse, the instructions that
5929 have most recently been executed are ``un-executed'', in reverse
5930 order. The program counter runs backward, following the previous
5931 thread of execution in reverse. As each instruction is ``un-executed'',
5932 the values of memory and/or registers that were changed by that
5933 instruction are reverted to their previous states. After executing
5934 a piece of source code in reverse, all side effects of that code
5935 should be ``undone'', and all variables should be returned to their
5936 prior values@footnote{
5937 Note that some side effects are easier to undo than others. For instance,
5938 memory and registers are relatively easy, but device I/O is hard. Some
5939 targets may be able undo things like device I/O, and some may not.
5941 The contract between @value{GDBN} and the reverse executing target
5942 requires only that the target do something reasonable when
5943 @value{GDBN} tells it to execute backwards, and then report the
5944 results back to @value{GDBN}. Whatever the target reports back to
5945 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5946 assumes that the memory and registers that the target reports are in a
5947 consistant state, but @value{GDBN} accepts whatever it is given.
5950 If you are debugging in a target environment that supports
5951 reverse execution, @value{GDBN} provides the following commands.
5954 @kindex reverse-continue
5955 @kindex rc @r{(@code{reverse-continue})}
5956 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5957 @itemx rc @r{[}@var{ignore-count}@r{]}
5958 Beginning at the point where your program last stopped, start executing
5959 in reverse. Reverse execution will stop for breakpoints and synchronous
5960 exceptions (signals), just like normal execution. Behavior of
5961 asynchronous signals depends on the target environment.
5963 @kindex reverse-step
5964 @kindex rs @r{(@code{step})}
5965 @item reverse-step @r{[}@var{count}@r{]}
5966 Run the program backward until control reaches the start of a
5967 different source line; then stop it, and return control to @value{GDBN}.
5969 Like the @code{step} command, @code{reverse-step} will only stop
5970 at the beginning of a source line. It ``un-executes'' the previously
5971 executed source line. If the previous source line included calls to
5972 debuggable functions, @code{reverse-step} will step (backward) into
5973 the called function, stopping at the beginning of the @emph{last}
5974 statement in the called function (typically a return statement).
5976 Also, as with the @code{step} command, if non-debuggable functions are
5977 called, @code{reverse-step} will run thru them backward without stopping.
5979 @kindex reverse-stepi
5980 @kindex rsi @r{(@code{reverse-stepi})}
5981 @item reverse-stepi @r{[}@var{count}@r{]}
5982 Reverse-execute one machine instruction. Note that the instruction
5983 to be reverse-executed is @emph{not} the one pointed to by the program
5984 counter, but the instruction executed prior to that one. For instance,
5985 if the last instruction was a jump, @code{reverse-stepi} will take you
5986 back from the destination of the jump to the jump instruction itself.
5988 @kindex reverse-next
5989 @kindex rn @r{(@code{reverse-next})}
5990 @item reverse-next @r{[}@var{count}@r{]}
5991 Run backward to the beginning of the previous line executed in
5992 the current (innermost) stack frame. If the line contains function
5993 calls, they will be ``un-executed'' without stopping. Starting from
5994 the first line of a function, @code{reverse-next} will take you back
5995 to the caller of that function, @emph{before} the function was called,
5996 just as the normal @code{next} command would take you from the last
5997 line of a function back to its return to its caller
5998 @footnote{Unless the code is too heavily optimized.}.
6000 @kindex reverse-nexti
6001 @kindex rni @r{(@code{reverse-nexti})}
6002 @item reverse-nexti @r{[}@var{count}@r{]}
6003 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6004 in reverse, except that called functions are ``un-executed'' atomically.
6005 That is, if the previously executed instruction was a return from
6006 another function, @code{reverse-nexti} will continue to execute
6007 in reverse until the call to that function (from the current stack
6010 @kindex reverse-finish
6011 @item reverse-finish
6012 Just as the @code{finish} command takes you to the point where the
6013 current function returns, @code{reverse-finish} takes you to the point
6014 where it was called. Instead of ending up at the end of the current
6015 function invocation, you end up at the beginning.
6017 @kindex set exec-direction
6018 @item set exec-direction
6019 Set the direction of target execution.
6020 @item set exec-direction reverse
6021 @cindex execute forward or backward in time
6022 @value{GDBN} will perform all execution commands in reverse, until the
6023 exec-direction mode is changed to ``forward''. Affected commands include
6024 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6025 command cannot be used in reverse mode.
6026 @item set exec-direction forward
6027 @value{GDBN} will perform all execution commands in the normal fashion.
6028 This is the default.
6032 @node Process Record and Replay
6033 @chapter Recording Inferior's Execution and Replaying It
6034 @cindex process record and replay
6035 @cindex recording inferior's execution and replaying it
6037 On some platforms, @value{GDBN} provides a special @dfn{process record
6038 and replay} target that can record a log of the process execution, and
6039 replay it later with both forward and reverse execution commands.
6042 When this target is in use, if the execution log includes the record
6043 for the next instruction, @value{GDBN} will debug in @dfn{replay
6044 mode}. In the replay mode, the inferior does not really execute code
6045 instructions. Instead, all the events that normally happen during
6046 code execution are taken from the execution log. While code is not
6047 really executed in replay mode, the values of registers (including the
6048 program counter register) and the memory of the inferior are still
6049 changed as they normally would. Their contents are taken from the
6053 If the record for the next instruction is not in the execution log,
6054 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6055 inferior executes normally, and @value{GDBN} records the execution log
6058 The process record and replay target supports reverse execution
6059 (@pxref{Reverse Execution}), even if the platform on which the
6060 inferior runs does not. However, the reverse execution is limited in
6061 this case by the range of the instructions recorded in the execution
6062 log. In other words, reverse execution on platforms that don't
6063 support it directly can only be done in the replay mode.
6065 When debugging in the reverse direction, @value{GDBN} will work in
6066 replay mode as long as the execution log includes the record for the
6067 previous instruction; otherwise, it will work in record mode, if the
6068 platform supports reverse execution, or stop if not.
6070 For architecture environments that support process record and replay,
6071 @value{GDBN} provides the following commands:
6074 @kindex target record
6078 This command starts the process record and replay target. The process
6079 record and replay target can only debug a process that is already
6080 running. Therefore, you need first to start the process with the
6081 @kbd{run} or @kbd{start} commands, and then start the recording with
6082 the @kbd{target record} command.
6084 Both @code{record} and @code{rec} are aliases of @code{target record}.
6086 @cindex displaced stepping, and process record and replay
6087 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6088 will be automatically disabled when process record and replay target
6089 is started. That's because the process record and replay target
6090 doesn't support displaced stepping.
6092 @cindex non-stop mode, and process record and replay
6093 @cindex asynchronous execution, and process record and replay
6094 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6095 the asynchronous execution mode (@pxref{Background Execution}), the
6096 process record and replay target cannot be started because it doesn't
6097 support these two modes.
6102 Stop the process record and replay target. When process record and
6103 replay target stops, the entire execution log will be deleted and the
6104 inferior will either be terminated, or will remain in its final state.
6106 When you stop the process record and replay target in record mode (at
6107 the end of the execution log), the inferior will be stopped at the
6108 next instruction that would have been recorded. In other words, if
6109 you record for a while and then stop recording, the inferior process
6110 will be left in the same state as if the recording never happened.
6112 On the other hand, if the process record and replay target is stopped
6113 while in replay mode (that is, not at the end of the execution log,
6114 but at some earlier point), the inferior process will become ``live''
6115 at that earlier state, and it will then be possible to continue the
6116 usual ``live'' debugging of the process from that state.
6118 When the inferior process exits, or @value{GDBN} detaches from it,
6119 process record and replay target will automatically stop itself.
6122 @item record save @var{filename}
6123 Save the execution log to a file @file{@var{filename}}.
6124 Default filename is @file{gdb_record.@var{process_id}}, where
6125 @var{process_id} is the process ID of the inferior.
6127 @kindex record restore
6128 @item record restore @var{filename}
6129 Restore the execution log from a file @file{@var{filename}}.
6130 File must have been created with @code{record save}.
6132 @kindex set record insn-number-max
6133 @item set record insn-number-max @var{limit}
6134 Set the limit of instructions to be recorded. Default value is 200000.
6136 If @var{limit} is a positive number, then @value{GDBN} will start
6137 deleting instructions from the log once the number of the record
6138 instructions becomes greater than @var{limit}. For every new recorded
6139 instruction, @value{GDBN} will delete the earliest recorded
6140 instruction to keep the number of recorded instructions at the limit.
6141 (Since deleting recorded instructions loses information, @value{GDBN}
6142 lets you control what happens when the limit is reached, by means of
6143 the @code{stop-at-limit} option, described below.)
6145 If @var{limit} is zero, @value{GDBN} will never delete recorded
6146 instructions from the execution log. The number of recorded
6147 instructions is unlimited in this case.
6149 @kindex show record insn-number-max
6150 @item show record insn-number-max
6151 Show the limit of instructions to be recorded.
6153 @kindex set record stop-at-limit
6154 @item set record stop-at-limit
6155 Control the behavior when the number of recorded instructions reaches
6156 the limit. If ON (the default), @value{GDBN} will stop when the limit
6157 is reached for the first time and ask you whether you want to stop the
6158 inferior or continue running it and recording the execution log. If
6159 you decide to continue recording, each new recorded instruction will
6160 cause the oldest one to be deleted.
6162 If this option is OFF, @value{GDBN} will automatically delete the
6163 oldest record to make room for each new one, without asking.
6165 @kindex show record stop-at-limit
6166 @item show record stop-at-limit
6167 Show the current setting of @code{stop-at-limit}.
6169 @kindex set record memory-query
6170 @item set record memory-query
6171 Control the behavior when @value{GDBN} is unable to record memory
6172 changes caused by an instruction. If ON, @value{GDBN} will query
6173 whether to stop the inferior in that case.
6175 If this option is OFF (the default), @value{GDBN} will automatically
6176 ignore the effect of such instructions on memory. Later, when
6177 @value{GDBN} replays this execution log, it will mark the log of this
6178 instruction as not accessible, and it will not affect the replay
6181 @kindex show record memory-query
6182 @item show record memory-query
6183 Show the current setting of @code{memory-query}.
6187 Show various statistics about the state of process record and its
6188 in-memory execution log buffer, including:
6192 Whether in record mode or replay mode.
6194 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6196 Highest recorded instruction number.
6198 Current instruction about to be replayed (if in replay mode).
6200 Number of instructions contained in the execution log.
6202 Maximum number of instructions that may be contained in the execution log.
6205 @kindex record delete
6208 When record target runs in replay mode (``in the past''), delete the
6209 subsequent execution log and begin to record a new execution log starting
6210 from the current address. This means you will abandon the previously
6211 recorded ``future'' and begin recording a new ``future''.
6216 @chapter Examining the Stack
6218 When your program has stopped, the first thing you need to know is where it
6219 stopped and how it got there.
6222 Each time your program performs a function call, information about the call
6224 That information includes the location of the call in your program,
6225 the arguments of the call,
6226 and the local variables of the function being called.
6227 The information is saved in a block of data called a @dfn{stack frame}.
6228 The stack frames are allocated in a region of memory called the @dfn{call
6231 When your program stops, the @value{GDBN} commands for examining the
6232 stack allow you to see all of this information.
6234 @cindex selected frame
6235 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6236 @value{GDBN} commands refer implicitly to the selected frame. In
6237 particular, whenever you ask @value{GDBN} for the value of a variable in
6238 your program, the value is found in the selected frame. There are
6239 special @value{GDBN} commands to select whichever frame you are
6240 interested in. @xref{Selection, ,Selecting a Frame}.
6242 When your program stops, @value{GDBN} automatically selects the
6243 currently executing frame and describes it briefly, similar to the
6244 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6247 * Frames:: Stack frames
6248 * Backtrace:: Backtraces
6249 * Selection:: Selecting a frame
6250 * Frame Info:: Information on a frame
6255 @section Stack Frames
6257 @cindex frame, definition
6259 The call stack is divided up into contiguous pieces called @dfn{stack
6260 frames}, or @dfn{frames} for short; each frame is the data associated
6261 with one call to one function. The frame contains the arguments given
6262 to the function, the function's local variables, and the address at
6263 which the function is executing.
6265 @cindex initial frame
6266 @cindex outermost frame
6267 @cindex innermost frame
6268 When your program is started, the stack has only one frame, that of the
6269 function @code{main}. This is called the @dfn{initial} frame or the
6270 @dfn{outermost} frame. Each time a function is called, a new frame is
6271 made. Each time a function returns, the frame for that function invocation
6272 is eliminated. If a function is recursive, there can be many frames for
6273 the same function. The frame for the function in which execution is
6274 actually occurring is called the @dfn{innermost} frame. This is the most
6275 recently created of all the stack frames that still exist.
6277 @cindex frame pointer
6278 Inside your program, stack frames are identified by their addresses. A
6279 stack frame consists of many bytes, each of which has its own address; each
6280 kind of computer has a convention for choosing one byte whose
6281 address serves as the address of the frame. Usually this address is kept
6282 in a register called the @dfn{frame pointer register}
6283 (@pxref{Registers, $fp}) while execution is going on in that frame.
6285 @cindex frame number
6286 @value{GDBN} assigns numbers to all existing stack frames, starting with
6287 zero for the innermost frame, one for the frame that called it,
6288 and so on upward. These numbers do not really exist in your program;
6289 they are assigned by @value{GDBN} to give you a way of designating stack
6290 frames in @value{GDBN} commands.
6292 @c The -fomit-frame-pointer below perennially causes hbox overflow
6293 @c underflow problems.
6294 @cindex frameless execution
6295 Some compilers provide a way to compile functions so that they operate
6296 without stack frames. (For example, the @value{NGCC} option
6298 @samp{-fomit-frame-pointer}
6300 generates functions without a frame.)
6301 This is occasionally done with heavily used library functions to save
6302 the frame setup time. @value{GDBN} has limited facilities for dealing
6303 with these function invocations. If the innermost function invocation
6304 has no stack frame, @value{GDBN} nevertheless regards it as though
6305 it had a separate frame, which is numbered zero as usual, allowing
6306 correct tracing of the function call chain. However, @value{GDBN} has
6307 no provision for frameless functions elsewhere in the stack.
6310 @kindex frame@r{, command}
6311 @cindex current stack frame
6312 @item frame @var{args}
6313 The @code{frame} command allows you to move from one stack frame to another,
6314 and to print the stack frame you select. @var{args} may be either the
6315 address of the frame or the stack frame number. Without an argument,
6316 @code{frame} prints the current stack frame.
6318 @kindex select-frame
6319 @cindex selecting frame silently
6321 The @code{select-frame} command allows you to move from one stack frame
6322 to another without printing the frame. This is the silent version of
6330 @cindex call stack traces
6331 A backtrace is a summary of how your program got where it is. It shows one
6332 line per frame, for many frames, starting with the currently executing
6333 frame (frame zero), followed by its caller (frame one), and on up the
6338 @kindex bt @r{(@code{backtrace})}
6341 Print a backtrace of the entire stack: one line per frame for all
6342 frames in the stack.
6344 You can stop the backtrace at any time by typing the system interrupt
6345 character, normally @kbd{Ctrl-c}.
6347 @item backtrace @var{n}
6349 Similar, but print only the innermost @var{n} frames.
6351 @item backtrace -@var{n}
6353 Similar, but print only the outermost @var{n} frames.
6355 @item backtrace full
6357 @itemx bt full @var{n}
6358 @itemx bt full -@var{n}
6359 Print the values of the local variables also. @var{n} specifies the
6360 number of frames to print, as described above.
6365 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6366 are additional aliases for @code{backtrace}.
6368 @cindex multiple threads, backtrace
6369 In a multi-threaded program, @value{GDBN} by default shows the
6370 backtrace only for the current thread. To display the backtrace for
6371 several or all of the threads, use the command @code{thread apply}
6372 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6373 apply all backtrace}, @value{GDBN} will display the backtrace for all
6374 the threads; this is handy when you debug a core dump of a
6375 multi-threaded program.
6377 Each line in the backtrace shows the frame number and the function name.
6378 The program counter value is also shown---unless you use @code{set
6379 print address off}. The backtrace also shows the source file name and
6380 line number, as well as the arguments to the function. The program
6381 counter value is omitted if it is at the beginning of the code for that
6384 Here is an example of a backtrace. It was made with the command
6385 @samp{bt 3}, so it shows the innermost three frames.
6389 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6391 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
6392 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
6394 (More stack frames follow...)
6399 The display for frame zero does not begin with a program counter
6400 value, indicating that your program has stopped at the beginning of the
6401 code for line @code{993} of @code{builtin.c}.
6404 The value of parameter @code{data} in frame 1 has been replaced by
6405 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
6406 only if it is a scalar (integer, pointer, enumeration, etc). See command
6407 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
6408 on how to configure the way function parameter values are printed.
6410 @cindex optimized out, in backtrace
6411 @cindex function call arguments, optimized out
6412 If your program was compiled with optimizations, some compilers will
6413 optimize away arguments passed to functions if those arguments are
6414 never used after the call. Such optimizations generate code that
6415 passes arguments through registers, but doesn't store those arguments
6416 in the stack frame. @value{GDBN} has no way of displaying such
6417 arguments in stack frames other than the innermost one. Here's what
6418 such a backtrace might look like:
6422 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6424 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6425 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6427 (More stack frames follow...)
6432 The values of arguments that were not saved in their stack frames are
6433 shown as @samp{<optimized out>}.
6435 If you need to display the values of such optimized-out arguments,
6436 either deduce that from other variables whose values depend on the one
6437 you are interested in, or recompile without optimizations.
6439 @cindex backtrace beyond @code{main} function
6440 @cindex program entry point
6441 @cindex startup code, and backtrace
6442 Most programs have a standard user entry point---a place where system
6443 libraries and startup code transition into user code. For C this is
6444 @code{main}@footnote{
6445 Note that embedded programs (the so-called ``free-standing''
6446 environment) are not required to have a @code{main} function as the
6447 entry point. They could even have multiple entry points.}.
6448 When @value{GDBN} finds the entry function in a backtrace
6449 it will terminate the backtrace, to avoid tracing into highly
6450 system-specific (and generally uninteresting) code.
6452 If you need to examine the startup code, or limit the number of levels
6453 in a backtrace, you can change this behavior:
6456 @item set backtrace past-main
6457 @itemx set backtrace past-main on
6458 @kindex set backtrace
6459 Backtraces will continue past the user entry point.
6461 @item set backtrace past-main off
6462 Backtraces will stop when they encounter the user entry point. This is the
6465 @item show backtrace past-main
6466 @kindex show backtrace
6467 Display the current user entry point backtrace policy.
6469 @item set backtrace past-entry
6470 @itemx set backtrace past-entry on
6471 Backtraces will continue past the internal entry point of an application.
6472 This entry point is encoded by the linker when the application is built,
6473 and is likely before the user entry point @code{main} (or equivalent) is called.
6475 @item set backtrace past-entry off
6476 Backtraces will stop when they encounter the internal entry point of an
6477 application. This is the default.
6479 @item show backtrace past-entry
6480 Display the current internal entry point backtrace policy.
6482 @item set backtrace limit @var{n}
6483 @itemx set backtrace limit 0
6484 @cindex backtrace limit
6485 Limit the backtrace to @var{n} levels. A value of zero means
6488 @item show backtrace limit
6489 Display the current limit on backtrace levels.
6493 @section Selecting a Frame
6495 Most commands for examining the stack and other data in your program work on
6496 whichever stack frame is selected at the moment. Here are the commands for
6497 selecting a stack frame; all of them finish by printing a brief description
6498 of the stack frame just selected.
6501 @kindex frame@r{, selecting}
6502 @kindex f @r{(@code{frame})}
6505 Select frame number @var{n}. Recall that frame zero is the innermost
6506 (currently executing) frame, frame one is the frame that called the
6507 innermost one, and so on. The highest-numbered frame is the one for
6510 @item frame @var{addr}
6512 Select the frame at address @var{addr}. This is useful mainly if the
6513 chaining of stack frames has been damaged by a bug, making it
6514 impossible for @value{GDBN} to assign numbers properly to all frames. In
6515 addition, this can be useful when your program has multiple stacks and
6516 switches between them.
6518 On the SPARC architecture, @code{frame} needs two addresses to
6519 select an arbitrary frame: a frame pointer and a stack pointer.
6521 On the @acronym{MIPS} and Alpha architecture, it needs two addresses: a stack
6522 pointer and a program counter.
6524 On the 29k architecture, it needs three addresses: a register stack
6525 pointer, a program counter, and a memory stack pointer.
6529 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6530 advances toward the outermost frame, to higher frame numbers, to frames
6531 that have existed longer. @var{n} defaults to one.
6534 @kindex do @r{(@code{down})}
6536 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6537 advances toward the innermost frame, to lower frame numbers, to frames
6538 that were created more recently. @var{n} defaults to one. You may
6539 abbreviate @code{down} as @code{do}.
6542 All of these commands end by printing two lines of output describing the
6543 frame. The first line shows the frame number, the function name, the
6544 arguments, and the source file and line number of execution in that
6545 frame. The second line shows the text of that source line.
6553 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6555 10 read_input_file (argv[i]);
6559 After such a printout, the @code{list} command with no arguments
6560 prints ten lines centered on the point of execution in the frame.
6561 You can also edit the program at the point of execution with your favorite
6562 editing program by typing @code{edit}.
6563 @xref{List, ,Printing Source Lines},
6567 @kindex down-silently
6569 @item up-silently @var{n}
6570 @itemx down-silently @var{n}
6571 These two commands are variants of @code{up} and @code{down},
6572 respectively; they differ in that they do their work silently, without
6573 causing display of the new frame. They are intended primarily for use
6574 in @value{GDBN} command scripts, where the output might be unnecessary and
6579 @section Information About a Frame
6581 There are several other commands to print information about the selected
6587 When used without any argument, this command does not change which
6588 frame is selected, but prints a brief description of the currently
6589 selected stack frame. It can be abbreviated @code{f}. With an
6590 argument, this command is used to select a stack frame.
6591 @xref{Selection, ,Selecting a Frame}.
6594 @kindex info f @r{(@code{info frame})}
6597 This command prints a verbose description of the selected stack frame,
6602 the address of the frame
6604 the address of the next frame down (called by this frame)
6606 the address of the next frame up (caller of this frame)
6608 the language in which the source code corresponding to this frame is written
6610 the address of the frame's arguments
6612 the address of the frame's local variables
6614 the program counter saved in it (the address of execution in the caller frame)
6616 which registers were saved in the frame
6619 @noindent The verbose description is useful when
6620 something has gone wrong that has made the stack format fail to fit
6621 the usual conventions.
6623 @item info frame @var{addr}
6624 @itemx info f @var{addr}
6625 Print a verbose description of the frame at address @var{addr}, without
6626 selecting that frame. The selected frame remains unchanged by this
6627 command. This requires the same kind of address (more than one for some
6628 architectures) that you specify in the @code{frame} command.
6629 @xref{Selection, ,Selecting a Frame}.
6633 Print the arguments of the selected frame, each on a separate line.
6637 Print the local variables of the selected frame, each on a separate
6638 line. These are all variables (declared either static or automatic)
6639 accessible at the point of execution of the selected frame.
6645 @chapter Examining Source Files
6647 @value{GDBN} can print parts of your program's source, since the debugging
6648 information recorded in the program tells @value{GDBN} what source files were
6649 used to build it. When your program stops, @value{GDBN} spontaneously prints
6650 the line where it stopped. Likewise, when you select a stack frame
6651 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6652 execution in that frame has stopped. You can print other portions of
6653 source files by explicit command.
6655 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6656 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6657 @value{GDBN} under @sc{gnu} Emacs}.
6660 * List:: Printing source lines
6661 * Specify Location:: How to specify code locations
6662 * Edit:: Editing source files
6663 * Search:: Searching source files
6664 * Source Path:: Specifying source directories
6665 * Machine Code:: Source and machine code
6669 @section Printing Source Lines
6672 @kindex l @r{(@code{list})}
6673 To print lines from a source file, use the @code{list} command
6674 (abbreviated @code{l}). By default, ten lines are printed.
6675 There are several ways to specify what part of the file you want to
6676 print; see @ref{Specify Location}, for the full list.
6678 Here are the forms of the @code{list} command most commonly used:
6681 @item list @var{linenum}
6682 Print lines centered around line number @var{linenum} in the
6683 current source file.
6685 @item list @var{function}
6686 Print lines centered around the beginning of function
6690 Print more lines. If the last lines printed were printed with a
6691 @code{list} command, this prints lines following the last lines
6692 printed; however, if the last line printed was a solitary line printed
6693 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6694 Stack}), this prints lines centered around that line.
6697 Print lines just before the lines last printed.
6700 @cindex @code{list}, how many lines to display
6701 By default, @value{GDBN} prints ten source lines with any of these forms of
6702 the @code{list} command. You can change this using @code{set listsize}:
6705 @kindex set listsize
6706 @item set listsize @var{count}
6707 Make the @code{list} command display @var{count} source lines (unless
6708 the @code{list} argument explicitly specifies some other number).
6710 @kindex show listsize
6712 Display the number of lines that @code{list} prints.
6715 Repeating a @code{list} command with @key{RET} discards the argument,
6716 so it is equivalent to typing just @code{list}. This is more useful
6717 than listing the same lines again. An exception is made for an
6718 argument of @samp{-}; that argument is preserved in repetition so that
6719 each repetition moves up in the source file.
6721 In general, the @code{list} command expects you to supply zero, one or two
6722 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6723 of writing them (@pxref{Specify Location}), but the effect is always
6724 to specify some source line.
6726 Here is a complete description of the possible arguments for @code{list}:
6729 @item list @var{linespec}
6730 Print lines centered around the line specified by @var{linespec}.
6732 @item list @var{first},@var{last}
6733 Print lines from @var{first} to @var{last}. Both arguments are
6734 linespecs. When a @code{list} command has two linespecs, and the
6735 source file of the second linespec is omitted, this refers to
6736 the same source file as the first linespec.
6738 @item list ,@var{last}
6739 Print lines ending with @var{last}.
6741 @item list @var{first},
6742 Print lines starting with @var{first}.
6745 Print lines just after the lines last printed.
6748 Print lines just before the lines last printed.
6751 As described in the preceding table.
6754 @node Specify Location
6755 @section Specifying a Location
6756 @cindex specifying location
6759 Several @value{GDBN} commands accept arguments that specify a location
6760 of your program's code. Since @value{GDBN} is a source-level
6761 debugger, a location usually specifies some line in the source code;
6762 for that reason, locations are also known as @dfn{linespecs}.
6764 Here are all the different ways of specifying a code location that
6765 @value{GDBN} understands:
6769 Specifies the line number @var{linenum} of the current source file.
6772 @itemx +@var{offset}
6773 Specifies the line @var{offset} lines before or after the @dfn{current
6774 line}. For the @code{list} command, the current line is the last one
6775 printed; for the breakpoint commands, this is the line at which
6776 execution stopped in the currently selected @dfn{stack frame}
6777 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6778 used as the second of the two linespecs in a @code{list} command,
6779 this specifies the line @var{offset} lines up or down from the first
6782 @item @var{filename}:@var{linenum}
6783 Specifies the line @var{linenum} in the source file @var{filename}.
6784 If @var{filename} is a relative file name, then it will match any
6785 source file name with the same trailing components. For example, if
6786 @var{filename} is @samp{gcc/expr.c}, then it will match source file
6787 name of @file{/build/trunk/gcc/expr.c}, but not
6788 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
6790 @item @var{function}
6791 Specifies the line that begins the body of the function @var{function}.
6792 For example, in C, this is the line with the open brace.
6794 @item @var{function}:@var{label}
6795 Specifies the line where @var{label} appears in @var{function}.
6797 @item @var{filename}:@var{function}
6798 Specifies the line that begins the body of the function @var{function}
6799 in the file @var{filename}. You only need the file name with a
6800 function name to avoid ambiguity when there are identically named
6801 functions in different source files.
6804 Specifies the line at which the label named @var{label} appears.
6805 @value{GDBN} searches for the label in the function corresponding to
6806 the currently selected stack frame. If there is no current selected
6807 stack frame (for instance, if the inferior is not running), then
6808 @value{GDBN} will not search for a label.
6810 @item *@var{address}
6811 Specifies the program address @var{address}. For line-oriented
6812 commands, such as @code{list} and @code{edit}, this specifies a source
6813 line that contains @var{address}. For @code{break} and other
6814 breakpoint oriented commands, this can be used to set breakpoints in
6815 parts of your program which do not have debugging information or
6818 Here @var{address} may be any expression valid in the current working
6819 language (@pxref{Languages, working language}) that specifies a code
6820 address. In addition, as a convenience, @value{GDBN} extends the
6821 semantics of expressions used in locations to cover the situations
6822 that frequently happen during debugging. Here are the various forms
6826 @item @var{expression}
6827 Any expression valid in the current working language.
6829 @item @var{funcaddr}
6830 An address of a function or procedure derived from its name. In C,
6831 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6832 simply the function's name @var{function} (and actually a special case
6833 of a valid expression). In Pascal and Modula-2, this is
6834 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6835 (although the Pascal form also works).
6837 This form specifies the address of the function's first instruction,
6838 before the stack frame and arguments have been set up.
6840 @item '@var{filename}'::@var{funcaddr}
6841 Like @var{funcaddr} above, but also specifies the name of the source
6842 file explicitly. This is useful if the name of the function does not
6843 specify the function unambiguously, e.g., if there are several
6844 functions with identical names in different source files.
6847 @cindex breakpoint at static probe point
6848 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
6849 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
6850 applications to embed static probes. @xref{Static Probe Points}, for more
6851 information on finding and using static probes. This form of linespec
6852 specifies the location of such a static probe.
6854 If @var{objfile} is given, only probes coming from that shared library
6855 or executable matching @var{objfile} as a regular expression are considered.
6856 If @var{provider} is given, then only probes from that provider are considered.
6857 If several probes match the spec, @value{GDBN} will insert a breakpoint at
6858 each one of those probes.
6864 @section Editing Source Files
6865 @cindex editing source files
6868 @kindex e @r{(@code{edit})}
6869 To edit the lines in a source file, use the @code{edit} command.
6870 The editing program of your choice
6871 is invoked with the current line set to
6872 the active line in the program.
6873 Alternatively, there are several ways to specify what part of the file you
6874 want to print if you want to see other parts of the program:
6877 @item edit @var{location}
6878 Edit the source file specified by @code{location}. Editing starts at
6879 that @var{location}, e.g., at the specified source line of the
6880 specified file. @xref{Specify Location}, for all the possible forms
6881 of the @var{location} argument; here are the forms of the @code{edit}
6882 command most commonly used:
6885 @item edit @var{number}
6886 Edit the current source file with @var{number} as the active line number.
6888 @item edit @var{function}
6889 Edit the file containing @var{function} at the beginning of its definition.
6894 @subsection Choosing your Editor
6895 You can customize @value{GDBN} to use any editor you want
6897 The only restriction is that your editor (say @code{ex}), recognizes the
6898 following command-line syntax:
6900 ex +@var{number} file
6902 The optional numeric value +@var{number} specifies the number of the line in
6903 the file where to start editing.}.
6904 By default, it is @file{@value{EDITOR}}, but you can change this
6905 by setting the environment variable @code{EDITOR} before using
6906 @value{GDBN}. For example, to configure @value{GDBN} to use the
6907 @code{vi} editor, you could use these commands with the @code{sh} shell:
6913 or in the @code{csh} shell,
6915 setenv EDITOR /usr/bin/vi
6920 @section Searching Source Files
6921 @cindex searching source files
6923 There are two commands for searching through the current source file for a
6928 @kindex forward-search
6929 @item forward-search @var{regexp}
6930 @itemx search @var{regexp}
6931 The command @samp{forward-search @var{regexp}} checks each line,
6932 starting with the one following the last line listed, for a match for
6933 @var{regexp}. It lists the line that is found. You can use the
6934 synonym @samp{search @var{regexp}} or abbreviate the command name as
6937 @kindex reverse-search
6938 @item reverse-search @var{regexp}
6939 The command @samp{reverse-search @var{regexp}} checks each line, starting
6940 with the one before the last line listed and going backward, for a match
6941 for @var{regexp}. It lists the line that is found. You can abbreviate
6942 this command as @code{rev}.
6946 @section Specifying Source Directories
6949 @cindex directories for source files
6950 Executable programs sometimes do not record the directories of the source
6951 files from which they were compiled, just the names. Even when they do,
6952 the directories could be moved between the compilation and your debugging
6953 session. @value{GDBN} has a list of directories to search for source files;
6954 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6955 it tries all the directories in the list, in the order they are present
6956 in the list, until it finds a file with the desired name.
6958 For example, suppose an executable references the file
6959 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6960 @file{/mnt/cross}. The file is first looked up literally; if this
6961 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6962 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6963 message is printed. @value{GDBN} does not look up the parts of the
6964 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6965 Likewise, the subdirectories of the source path are not searched: if
6966 the source path is @file{/mnt/cross}, and the binary refers to
6967 @file{foo.c}, @value{GDBN} would not find it under
6968 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6970 Plain file names, relative file names with leading directories, file
6971 names containing dots, etc.@: are all treated as described above; for
6972 instance, if the source path is @file{/mnt/cross}, and the source file
6973 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6974 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6975 that---@file{/mnt/cross/foo.c}.
6977 Note that the executable search path is @emph{not} used to locate the
6980 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6981 any information it has cached about where source files are found and where
6982 each line is in the file.
6986 When you start @value{GDBN}, its source path includes only @samp{cdir}
6987 and @samp{cwd}, in that order.
6988 To add other directories, use the @code{directory} command.
6990 The search path is used to find both program source files and @value{GDBN}
6991 script files (read using the @samp{-command} option and @samp{source} command).
6993 In addition to the source path, @value{GDBN} provides a set of commands
6994 that manage a list of source path substitution rules. A @dfn{substitution
6995 rule} specifies how to rewrite source directories stored in the program's
6996 debug information in case the sources were moved to a different
6997 directory between compilation and debugging. A rule is made of
6998 two strings, the first specifying what needs to be rewritten in
6999 the path, and the second specifying how it should be rewritten.
7000 In @ref{set substitute-path}, we name these two parts @var{from} and
7001 @var{to} respectively. @value{GDBN} does a simple string replacement
7002 of @var{from} with @var{to} at the start of the directory part of the
7003 source file name, and uses that result instead of the original file
7004 name to look up the sources.
7006 Using the previous example, suppose the @file{foo-1.0} tree has been
7007 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
7008 @value{GDBN} to replace @file{/usr/src} in all source path names with
7009 @file{/mnt/cross}. The first lookup will then be
7010 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
7011 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
7012 substitution rule, use the @code{set substitute-path} command
7013 (@pxref{set substitute-path}).
7015 To avoid unexpected substitution results, a rule is applied only if the
7016 @var{from} part of the directory name ends at a directory separator.
7017 For instance, a rule substituting @file{/usr/source} into
7018 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
7019 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
7020 is applied only at the beginning of the directory name, this rule will
7021 not be applied to @file{/root/usr/source/baz.c} either.
7023 In many cases, you can achieve the same result using the @code{directory}
7024 command. However, @code{set substitute-path} can be more efficient in
7025 the case where the sources are organized in a complex tree with multiple
7026 subdirectories. With the @code{directory} command, you need to add each
7027 subdirectory of your project. If you moved the entire tree while
7028 preserving its internal organization, then @code{set substitute-path}
7029 allows you to direct the debugger to all the sources with one single
7032 @code{set substitute-path} is also more than just a shortcut command.
7033 The source path is only used if the file at the original location no
7034 longer exists. On the other hand, @code{set substitute-path} modifies
7035 the debugger behavior to look at the rewritten location instead. So, if
7036 for any reason a source file that is not relevant to your executable is
7037 located at the original location, a substitution rule is the only
7038 method available to point @value{GDBN} at the new location.
7040 @cindex @samp{--with-relocated-sources}
7041 @cindex default source path substitution
7042 You can configure a default source path substitution rule by
7043 configuring @value{GDBN} with the
7044 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
7045 should be the name of a directory under @value{GDBN}'s configured
7046 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
7047 directory names in debug information under @var{dir} will be adjusted
7048 automatically if the installed @value{GDBN} is moved to a new
7049 location. This is useful if @value{GDBN}, libraries or executables
7050 with debug information and corresponding source code are being moved
7054 @item directory @var{dirname} @dots{}
7055 @item dir @var{dirname} @dots{}
7056 Add directory @var{dirname} to the front of the source path. Several
7057 directory names may be given to this command, separated by @samp{:}
7058 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
7059 part of absolute file names) or
7060 whitespace. You may specify a directory that is already in the source
7061 path; this moves it forward, so @value{GDBN} searches it sooner.
7065 @vindex $cdir@r{, convenience variable}
7066 @vindex $cwd@r{, convenience variable}
7067 @cindex compilation directory
7068 @cindex current directory
7069 @cindex working directory
7070 @cindex directory, current
7071 @cindex directory, compilation
7072 You can use the string @samp{$cdir} to refer to the compilation
7073 directory (if one is recorded), and @samp{$cwd} to refer to the current
7074 working directory. @samp{$cwd} is not the same as @samp{.}---the former
7075 tracks the current working directory as it changes during your @value{GDBN}
7076 session, while the latter is immediately expanded to the current
7077 directory at the time you add an entry to the source path.
7080 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
7082 @c RET-repeat for @code{directory} is explicitly disabled, but since
7083 @c repeating it would be a no-op we do not say that. (thanks to RMS)
7085 @item set directories @var{path-list}
7086 @kindex set directories
7087 Set the source path to @var{path-list}.
7088 @samp{$cdir:$cwd} are added if missing.
7090 @item show directories
7091 @kindex show directories
7092 Print the source path: show which directories it contains.
7094 @anchor{set substitute-path}
7095 @item set substitute-path @var{from} @var{to}
7096 @kindex set substitute-path
7097 Define a source path substitution rule, and add it at the end of the
7098 current list of existing substitution rules. If a rule with the same
7099 @var{from} was already defined, then the old rule is also deleted.
7101 For example, if the file @file{/foo/bar/baz.c} was moved to
7102 @file{/mnt/cross/baz.c}, then the command
7105 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
7109 will tell @value{GDBN} to replace @samp{/usr/src} with
7110 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
7111 @file{baz.c} even though it was moved.
7113 In the case when more than one substitution rule have been defined,
7114 the rules are evaluated one by one in the order where they have been
7115 defined. The first one matching, if any, is selected to perform
7118 For instance, if we had entered the following commands:
7121 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
7122 (@value{GDBP}) set substitute-path /usr/src /mnt/src
7126 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
7127 @file{/mnt/include/defs.h} by using the first rule. However, it would
7128 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
7129 @file{/mnt/src/lib/foo.c}.
7132 @item unset substitute-path [path]
7133 @kindex unset substitute-path
7134 If a path is specified, search the current list of substitution rules
7135 for a rule that would rewrite that path. Delete that rule if found.
7136 A warning is emitted by the debugger if no rule could be found.
7138 If no path is specified, then all substitution rules are deleted.
7140 @item show substitute-path [path]
7141 @kindex show substitute-path
7142 If a path is specified, then print the source path substitution rule
7143 which would rewrite that path, if any.
7145 If no path is specified, then print all existing source path substitution
7150 If your source path is cluttered with directories that are no longer of
7151 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
7152 versions of source. You can correct the situation as follows:
7156 Use @code{directory} with no argument to reset the source path to its default value.
7159 Use @code{directory} with suitable arguments to reinstall the
7160 directories you want in the source path. You can add all the
7161 directories in one command.
7165 @section Source and Machine Code
7166 @cindex source line and its code address
7168 You can use the command @code{info line} to map source lines to program
7169 addresses (and vice versa), and the command @code{disassemble} to display
7170 a range of addresses as machine instructions. You can use the command
7171 @code{set disassemble-next-line} to set whether to disassemble next
7172 source line when execution stops. When run under @sc{gnu} Emacs
7173 mode, the @code{info line} command causes the arrow to point to the
7174 line specified. Also, @code{info line} prints addresses in symbolic form as
7179 @item info line @var{linespec}
7180 Print the starting and ending addresses of the compiled code for
7181 source line @var{linespec}. You can specify source lines in any of
7182 the ways documented in @ref{Specify Location}.
7185 For example, we can use @code{info line} to discover the location of
7186 the object code for the first line of function
7187 @code{m4_changequote}:
7189 @c FIXME: I think this example should also show the addresses in
7190 @c symbolic form, as they usually would be displayed.
7192 (@value{GDBP}) info line m4_changequote
7193 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
7197 @cindex code address and its source line
7198 We can also inquire (using @code{*@var{addr}} as the form for
7199 @var{linespec}) what source line covers a particular address:
7201 (@value{GDBP}) info line *0x63ff
7202 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
7205 @cindex @code{$_} and @code{info line}
7206 @cindex @code{x} command, default address
7207 @kindex x@r{(examine), and} info line
7208 After @code{info line}, the default address for the @code{x} command
7209 is changed to the starting address of the line, so that @samp{x/i} is
7210 sufficient to begin examining the machine code (@pxref{Memory,
7211 ,Examining Memory}). Also, this address is saved as the value of the
7212 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
7217 @cindex assembly instructions
7218 @cindex instructions, assembly
7219 @cindex machine instructions
7220 @cindex listing machine instructions
7222 @itemx disassemble /m
7223 @itemx disassemble /r
7224 This specialized command dumps a range of memory as machine
7225 instructions. It can also print mixed source+disassembly by specifying
7226 the @code{/m} modifier and print the raw instructions in hex as well as
7227 in symbolic form by specifying the @code{/r}.
7228 The default memory range is the function surrounding the
7229 program counter of the selected frame. A single argument to this
7230 command is a program counter value; @value{GDBN} dumps the function
7231 surrounding this value. When two arguments are given, they should
7232 be separated by a comma, possibly surrounded by whitespace. The
7233 arguments specify a range of addresses to dump, in one of two forms:
7236 @item @var{start},@var{end}
7237 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
7238 @item @var{start},+@var{length}
7239 the addresses from @var{start} (inclusive) to
7240 @code{@var{start}+@var{length}} (exclusive).
7244 When 2 arguments are specified, the name of the function is also
7245 printed (since there could be several functions in the given range).
7247 The argument(s) can be any expression yielding a numeric value, such as
7248 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
7250 If the range of memory being disassembled contains current program counter,
7251 the instruction at that location is shown with a @code{=>} marker.
7254 The following example shows the disassembly of a range of addresses of
7255 HP PA-RISC 2.0 code:
7258 (@value{GDBP}) disas 0x32c4, 0x32e4
7259 Dump of assembler code from 0x32c4 to 0x32e4:
7260 0x32c4 <main+204>: addil 0,dp
7261 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
7262 0x32cc <main+212>: ldil 0x3000,r31
7263 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
7264 0x32d4 <main+220>: ldo 0(r31),rp
7265 0x32d8 <main+224>: addil -0x800,dp
7266 0x32dc <main+228>: ldo 0x588(r1),r26
7267 0x32e0 <main+232>: ldil 0x3000,r31
7268 End of assembler dump.
7271 Here is an example showing mixed source+assembly for Intel x86, when the
7272 program is stopped just after function prologue:
7275 (@value{GDBP}) disas /m main
7276 Dump of assembler code for function main:
7278 0x08048330 <+0>: push %ebp
7279 0x08048331 <+1>: mov %esp,%ebp
7280 0x08048333 <+3>: sub $0x8,%esp
7281 0x08048336 <+6>: and $0xfffffff0,%esp
7282 0x08048339 <+9>: sub $0x10,%esp
7284 6 printf ("Hello.\n");
7285 => 0x0804833c <+12>: movl $0x8048440,(%esp)
7286 0x08048343 <+19>: call 0x8048284 <puts@@plt>
7290 0x08048348 <+24>: mov $0x0,%eax
7291 0x0804834d <+29>: leave
7292 0x0804834e <+30>: ret
7294 End of assembler dump.
7297 Here is another example showing raw instructions in hex for AMD x86-64,
7300 (gdb) disas /r 0x400281,+10
7301 Dump of assembler code from 0x400281 to 0x40028b:
7302 0x0000000000400281: 38 36 cmp %dh,(%rsi)
7303 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
7304 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
7305 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
7306 End of assembler dump.
7309 Some architectures have more than one commonly-used set of instruction
7310 mnemonics or other syntax.
7312 For programs that were dynamically linked and use shared libraries,
7313 instructions that call functions or branch to locations in the shared
7314 libraries might show a seemingly bogus location---it's actually a
7315 location of the relocation table. On some architectures, @value{GDBN}
7316 might be able to resolve these to actual function names.
7319 @kindex set disassembly-flavor
7320 @cindex Intel disassembly flavor
7321 @cindex AT&T disassembly flavor
7322 @item set disassembly-flavor @var{instruction-set}
7323 Select the instruction set to use when disassembling the
7324 program via the @code{disassemble} or @code{x/i} commands.
7326 Currently this command is only defined for the Intel x86 family. You
7327 can set @var{instruction-set} to either @code{intel} or @code{att}.
7328 The default is @code{att}, the AT&T flavor used by default by Unix
7329 assemblers for x86-based targets.
7331 @kindex show disassembly-flavor
7332 @item show disassembly-flavor
7333 Show the current setting of the disassembly flavor.
7337 @kindex set disassemble-next-line
7338 @kindex show disassemble-next-line
7339 @item set disassemble-next-line
7340 @itemx show disassemble-next-line
7341 Control whether or not @value{GDBN} will disassemble the next source
7342 line or instruction when execution stops. If ON, @value{GDBN} will
7343 display disassembly of the next source line when execution of the
7344 program being debugged stops. This is @emph{in addition} to
7345 displaying the source line itself, which @value{GDBN} always does if
7346 possible. If the next source line cannot be displayed for some reason
7347 (e.g., if @value{GDBN} cannot find the source file, or there's no line
7348 info in the debug info), @value{GDBN} will display disassembly of the
7349 next @emph{instruction} instead of showing the next source line. If
7350 AUTO, @value{GDBN} will display disassembly of next instruction only
7351 if the source line cannot be displayed. This setting causes
7352 @value{GDBN} to display some feedback when you step through a function
7353 with no line info or whose source file is unavailable. The default is
7354 OFF, which means never display the disassembly of the next line or
7360 @chapter Examining Data
7362 @cindex printing data
7363 @cindex examining data
7366 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
7367 @c document because it is nonstandard... Under Epoch it displays in a
7368 @c different window or something like that.
7369 The usual way to examine data in your program is with the @code{print}
7370 command (abbreviated @code{p}), or its synonym @code{inspect}. It
7371 evaluates and prints the value of an expression of the language your
7372 program is written in (@pxref{Languages, ,Using @value{GDBN} with
7373 Different Languages}). It may also print the expression using a
7374 Python-based pretty-printer (@pxref{Pretty Printing}).
7377 @item print @var{expr}
7378 @itemx print /@var{f} @var{expr}
7379 @var{expr} is an expression (in the source language). By default the
7380 value of @var{expr} is printed in a format appropriate to its data type;
7381 you can choose a different format by specifying @samp{/@var{f}}, where
7382 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
7386 @itemx print /@var{f}
7387 @cindex reprint the last value
7388 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
7389 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
7390 conveniently inspect the same value in an alternative format.
7393 A more low-level way of examining data is with the @code{x} command.
7394 It examines data in memory at a specified address and prints it in a
7395 specified format. @xref{Memory, ,Examining Memory}.
7397 If you are interested in information about types, or about how the
7398 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
7399 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
7402 @cindex exploring hierarchical data structures
7404 Another way of examining values of expressions and type information is
7405 through the Python extension command @code{explore} (available only if
7406 the @value{GDBN} build is configured with @code{--with-python}). It
7407 offers an interactive way to start at the highest level (or, the most
7408 abstract level) of the data type of an expression (or, the data type
7409 itself) and explore all the way down to leaf scalar values/fields
7410 embedded in the higher level data types.
7413 @item explore @var{arg}
7414 @var{arg} is either an expression (in the source language), or a type
7415 visible in the current context of the program being debugged.
7418 The working of the @code{explore} command can be illustrated with an
7419 example. If a data type @code{struct ComplexStruct} is defined in your
7429 struct ComplexStruct
7431 struct SimpleStruct *ss_p;
7437 followed by variable declarations as
7440 struct SimpleStruct ss = @{ 10, 1.11 @};
7441 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
7445 then, the value of the variable @code{cs} can be explored using the
7446 @code{explore} command as follows.
7450 The value of `cs' is a struct/class of type `struct ComplexStruct' with
7451 the following fields:
7453 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
7454 arr = <Enter 1 to explore this field of type `int [10]'>
7456 Enter the field number of choice:
7460 Since the fields of @code{cs} are not scalar values, you are being
7461 prompted to chose the field you want to explore. Let's say you choose
7462 the field @code{ss_p} by entering @code{0}. Then, since this field is a
7463 pointer, you will be asked if it is pointing to a single value. From
7464 the declaration of @code{cs} above, it is indeed pointing to a single
7465 value, hence you enter @code{y}. If you enter @code{n}, then you will
7466 be asked if it were pointing to an array of values, in which case this
7467 field will be explored as if it were an array.
7470 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
7471 Continue exploring it as a pointer to a single value [y/n]: y
7472 The value of `*(cs.ss_p)' is a struct/class of type `struct
7473 SimpleStruct' with the following fields:
7475 i = 10 .. (Value of type `int')
7476 d = 1.1100000000000001 .. (Value of type `double')
7478 Press enter to return to parent value:
7482 If the field @code{arr} of @code{cs} was chosen for exploration by
7483 entering @code{1} earlier, then since it is as array, you will be
7484 prompted to enter the index of the element in the array that you want
7488 `cs.arr' is an array of `int'.
7489 Enter the index of the element you want to explore in `cs.arr': 5
7491 `(cs.arr)[5]' is a scalar value of type `int'.
7495 Press enter to return to parent value:
7498 In general, at any stage of exploration, you can go deeper towards the
7499 leaf values by responding to the prompts appropriately, or hit the
7500 return key to return to the enclosing data structure (the @i{higher}
7501 level data structure).
7503 Similar to exploring values, you can use the @code{explore} command to
7504 explore types. Instead of specifying a value (which is typically a
7505 variable name or an expression valid in the current context of the
7506 program being debugged), you specify a type name. If you consider the
7507 same example as above, your can explore the type
7508 @code{struct ComplexStruct} by passing the argument
7509 @code{struct ComplexStruct} to the @code{explore} command.
7512 (gdb) explore struct ComplexStruct
7516 By responding to the prompts appropriately in the subsequent interactive
7517 session, you can explore the type @code{struct ComplexStruct} in a
7518 manner similar to how the value @code{cs} was explored in the above
7521 The @code{explore} command also has two sub-commands,
7522 @code{explore value} and @code{explore type}. The former sub-command is
7523 a way to explicitly specify that value exploration of the argument is
7524 being invoked, while the latter is a way to explicitly specify that type
7525 exploration of the argument is being invoked.
7528 @item explore value @var{expr}
7529 @cindex explore value
7530 This sub-command of @code{explore} explores the value of the
7531 expression @var{expr} (if @var{expr} is an expression valid in the
7532 current context of the program being debugged). The behavior of this
7533 command is identical to that of the behavior of the @code{explore}
7534 command being passed the argument @var{expr}.
7536 @item explore type @var{arg}
7537 @cindex explore type
7538 This sub-command of @code{explore} explores the type of @var{arg} (if
7539 @var{arg} is a type visible in the current context of program being
7540 debugged), or the type of the value/expression @var{arg} (if @var{arg}
7541 is an expression valid in the current context of the program being
7542 debugged). If @var{arg} is a type, then the behavior of this command is
7543 identical to that of the @code{explore} command being passed the
7544 argument @var{arg}. If @var{arg} is an expression, then the behavior of
7545 this command will be identical to that of the @code{explore} command
7546 being passed the type of @var{arg} as the argument.
7550 * Expressions:: Expressions
7551 * Ambiguous Expressions:: Ambiguous Expressions
7552 * Variables:: Program variables
7553 * Arrays:: Artificial arrays
7554 * Output Formats:: Output formats
7555 * Memory:: Examining memory
7556 * Auto Display:: Automatic display
7557 * Print Settings:: Print settings
7558 * Pretty Printing:: Python pretty printing
7559 * Value History:: Value history
7560 * Convenience Vars:: Convenience variables
7561 * Convenience Funs:: Convenience functions
7562 * Registers:: Registers
7563 * Floating Point Hardware:: Floating point hardware
7564 * Vector Unit:: Vector Unit
7565 * OS Information:: Auxiliary data provided by operating system
7566 * Memory Region Attributes:: Memory region attributes
7567 * Dump/Restore Files:: Copy between memory and a file
7568 * Core File Generation:: Cause a program dump its core
7569 * Character Sets:: Debugging programs that use a different
7570 character set than GDB does
7571 * Caching Remote Data:: Data caching for remote targets
7572 * Searching Memory:: Searching memory for a sequence of bytes
7576 @section Expressions
7579 @code{print} and many other @value{GDBN} commands accept an expression and
7580 compute its value. Any kind of constant, variable or operator defined
7581 by the programming language you are using is valid in an expression in
7582 @value{GDBN}. This includes conditional expressions, function calls,
7583 casts, and string constants. It also includes preprocessor macros, if
7584 you compiled your program to include this information; see
7587 @cindex arrays in expressions
7588 @value{GDBN} supports array constants in expressions input by
7589 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
7590 you can use the command @code{print @{1, 2, 3@}} to create an array
7591 of three integers. If you pass an array to a function or assign it
7592 to a program variable, @value{GDBN} copies the array to memory that
7593 is @code{malloc}ed in the target program.
7595 Because C is so widespread, most of the expressions shown in examples in
7596 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
7597 Languages}, for information on how to use expressions in other
7600 In this section, we discuss operators that you can use in @value{GDBN}
7601 expressions regardless of your programming language.
7603 @cindex casts, in expressions
7604 Casts are supported in all languages, not just in C, because it is so
7605 useful to cast a number into a pointer in order to examine a structure
7606 at that address in memory.
7607 @c FIXME: casts supported---Mod2 true?
7609 @value{GDBN} supports these operators, in addition to those common
7610 to programming languages:
7614 @samp{@@} is a binary operator for treating parts of memory as arrays.
7615 @xref{Arrays, ,Artificial Arrays}, for more information.
7618 @samp{::} allows you to specify a variable in terms of the file or
7619 function where it is defined. @xref{Variables, ,Program Variables}.
7621 @cindex @{@var{type}@}
7622 @cindex type casting memory
7623 @cindex memory, viewing as typed object
7624 @cindex casts, to view memory
7625 @item @{@var{type}@} @var{addr}
7626 Refers to an object of type @var{type} stored at address @var{addr} in
7627 memory. @var{addr} may be any expression whose value is an integer or
7628 pointer (but parentheses are required around binary operators, just as in
7629 a cast). This construct is allowed regardless of what kind of data is
7630 normally supposed to reside at @var{addr}.
7633 @node Ambiguous Expressions
7634 @section Ambiguous Expressions
7635 @cindex ambiguous expressions
7637 Expressions can sometimes contain some ambiguous elements. For instance,
7638 some programming languages (notably Ada, C@t{++} and Objective-C) permit
7639 a single function name to be defined several times, for application in
7640 different contexts. This is called @dfn{overloading}. Another example
7641 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
7642 templates and is typically instantiated several times, resulting in
7643 the same function name being defined in different contexts.
7645 In some cases and depending on the language, it is possible to adjust
7646 the expression to remove the ambiguity. For instance in C@t{++}, you
7647 can specify the signature of the function you want to break on, as in
7648 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
7649 qualified name of your function often makes the expression unambiguous
7652 When an ambiguity that needs to be resolved is detected, the debugger
7653 has the capability to display a menu of numbered choices for each
7654 possibility, and then waits for the selection with the prompt @samp{>}.
7655 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
7656 aborts the current command. If the command in which the expression was
7657 used allows more than one choice to be selected, the next option in the
7658 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
7661 For example, the following session excerpt shows an attempt to set a
7662 breakpoint at the overloaded symbol @code{String::after}.
7663 We choose three particular definitions of that function name:
7665 @c FIXME! This is likely to change to show arg type lists, at least
7668 (@value{GDBP}) b String::after
7671 [2] file:String.cc; line number:867
7672 [3] file:String.cc; line number:860
7673 [4] file:String.cc; line number:875
7674 [5] file:String.cc; line number:853
7675 [6] file:String.cc; line number:846
7676 [7] file:String.cc; line number:735
7678 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7679 Breakpoint 2 at 0xb344: file String.cc, line 875.
7680 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7681 Multiple breakpoints were set.
7682 Use the "delete" command to delete unwanted
7689 @kindex set multiple-symbols
7690 @item set multiple-symbols @var{mode}
7691 @cindex multiple-symbols menu
7693 This option allows you to adjust the debugger behavior when an expression
7696 By default, @var{mode} is set to @code{all}. If the command with which
7697 the expression is used allows more than one choice, then @value{GDBN}
7698 automatically selects all possible choices. For instance, inserting
7699 a breakpoint on a function using an ambiguous name results in a breakpoint
7700 inserted on each possible match. However, if a unique choice must be made,
7701 then @value{GDBN} uses the menu to help you disambiguate the expression.
7702 For instance, printing the address of an overloaded function will result
7703 in the use of the menu.
7705 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7706 when an ambiguity is detected.
7708 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7709 an error due to the ambiguity and the command is aborted.
7711 @kindex show multiple-symbols
7712 @item show multiple-symbols
7713 Show the current value of the @code{multiple-symbols} setting.
7717 @section Program Variables
7719 The most common kind of expression to use is the name of a variable
7722 Variables in expressions are understood in the selected stack frame
7723 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7727 global (or file-static)
7734 visible according to the scope rules of the
7735 programming language from the point of execution in that frame
7738 @noindent This means that in the function
7753 you can examine and use the variable @code{a} whenever your program is
7754 executing within the function @code{foo}, but you can only use or
7755 examine the variable @code{b} while your program is executing inside
7756 the block where @code{b} is declared.
7758 @cindex variable name conflict
7759 There is an exception: you can refer to a variable or function whose
7760 scope is a single source file even if the current execution point is not
7761 in this file. But it is possible to have more than one such variable or
7762 function with the same name (in different source files). If that
7763 happens, referring to that name has unpredictable effects. If you wish,
7764 you can specify a static variable in a particular function or file by
7765 using the colon-colon (@code{::}) notation:
7767 @cindex colon-colon, context for variables/functions
7769 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
7770 @cindex @code{::}, context for variables/functions
7773 @var{file}::@var{variable}
7774 @var{function}::@var{variable}
7778 Here @var{file} or @var{function} is the name of the context for the
7779 static @var{variable}. In the case of file names, you can use quotes to
7780 make sure @value{GDBN} parses the file name as a single word---for example,
7781 to print a global value of @code{x} defined in @file{f2.c}:
7784 (@value{GDBP}) p 'f2.c'::x
7787 The @code{::} notation is normally used for referring to
7788 static variables, since you typically disambiguate uses of local variables
7789 in functions by selecting the appropriate frame and using the
7790 simple name of the variable. However, you may also use this notation
7791 to refer to local variables in frames enclosing the selected frame:
7800 process (a); /* Stop here */
7811 For example, if there is a breakpoint at the commented line,
7812 here is what you might see
7813 when the program stops after executing the call @code{bar(0)}:
7818 (@value{GDBP}) p bar::a
7821 #2 0x080483d0 in foo (a=5) at foobar.c:12
7824 (@value{GDBP}) p bar::a
7828 @cindex C@t{++} scope resolution
7829 These uses of @samp{::} are very rarely in conflict with the very similar
7830 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
7831 scope resolution operator in @value{GDBN} expressions.
7832 @c FIXME: Um, so what happens in one of those rare cases where it's in
7835 @cindex wrong values
7836 @cindex variable values, wrong
7837 @cindex function entry/exit, wrong values of variables
7838 @cindex optimized code, wrong values of variables
7840 @emph{Warning:} Occasionally, a local variable may appear to have the
7841 wrong value at certain points in a function---just after entry to a new
7842 scope, and just before exit.
7844 You may see this problem when you are stepping by machine instructions.
7845 This is because, on most machines, it takes more than one instruction to
7846 set up a stack frame (including local variable definitions); if you are
7847 stepping by machine instructions, variables may appear to have the wrong
7848 values until the stack frame is completely built. On exit, it usually
7849 also takes more than one machine instruction to destroy a stack frame;
7850 after you begin stepping through that group of instructions, local
7851 variable definitions may be gone.
7853 This may also happen when the compiler does significant optimizations.
7854 To be sure of always seeing accurate values, turn off all optimization
7857 @cindex ``No symbol "foo" in current context''
7858 Another possible effect of compiler optimizations is to optimize
7859 unused variables out of existence, or assign variables to registers (as
7860 opposed to memory addresses). Depending on the support for such cases
7861 offered by the debug info format used by the compiler, @value{GDBN}
7862 might not be able to display values for such local variables. If that
7863 happens, @value{GDBN} will print a message like this:
7866 No symbol "foo" in current context.
7869 To solve such problems, either recompile without optimizations, or use a
7870 different debug info format, if the compiler supports several such
7871 formats. @xref{Compilation}, for more information on choosing compiler
7872 options. @xref{C, ,C and C@t{++}}, for more information about debug
7873 info formats that are best suited to C@t{++} programs.
7875 If you ask to print an object whose contents are unknown to
7876 @value{GDBN}, e.g., because its data type is not completely specified
7877 by the debug information, @value{GDBN} will say @samp{<incomplete
7878 type>}. @xref{Symbols, incomplete type}, for more about this.
7880 If you append @kbd{@@entry} string to a function parameter name you get its
7881 value at the time the function got called. If the value is not available an
7882 error message is printed. Entry values are available only with some compilers.
7883 Entry values are normally also printed at the function parameter list according
7884 to @ref{set print entry-values}.
7887 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
7893 (gdb) print i@@entry
7897 Strings are identified as arrays of @code{char} values without specified
7898 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
7899 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
7900 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
7901 defines literal string type @code{"char"} as @code{char} without a sign.
7906 signed char var1[] = "A";
7909 You get during debugging
7914 $2 = @{65 'A', 0 '\0'@}
7918 @section Artificial Arrays
7920 @cindex artificial array
7922 @kindex @@@r{, referencing memory as an array}
7923 It is often useful to print out several successive objects of the
7924 same type in memory; a section of an array, or an array of
7925 dynamically determined size for which only a pointer exists in the
7928 You can do this by referring to a contiguous span of memory as an
7929 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7930 operand of @samp{@@} should be the first element of the desired array
7931 and be an individual object. The right operand should be the desired length
7932 of the array. The result is an array value whose elements are all of
7933 the type of the left argument. The first element is actually the left
7934 argument; the second element comes from bytes of memory immediately
7935 following those that hold the first element, and so on. Here is an
7936 example. If a program says
7939 int *array = (int *) malloc (len * sizeof (int));
7943 you can print the contents of @code{array} with
7949 The left operand of @samp{@@} must reside in memory. Array values made
7950 with @samp{@@} in this way behave just like other arrays in terms of
7951 subscripting, and are coerced to pointers when used in expressions.
7952 Artificial arrays most often appear in expressions via the value history
7953 (@pxref{Value History, ,Value History}), after printing one out.
7955 Another way to create an artificial array is to use a cast.
7956 This re-interprets a value as if it were an array.
7957 The value need not be in memory:
7959 (@value{GDBP}) p/x (short[2])0x12345678
7960 $1 = @{0x1234, 0x5678@}
7963 As a convenience, if you leave the array length out (as in
7964 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7965 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7967 (@value{GDBP}) p/x (short[])0x12345678
7968 $2 = @{0x1234, 0x5678@}
7971 Sometimes the artificial array mechanism is not quite enough; in
7972 moderately complex data structures, the elements of interest may not
7973 actually be adjacent---for example, if you are interested in the values
7974 of pointers in an array. One useful work-around in this situation is
7975 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
7976 Variables}) as a counter in an expression that prints the first
7977 interesting value, and then repeat that expression via @key{RET}. For
7978 instance, suppose you have an array @code{dtab} of pointers to
7979 structures, and you are interested in the values of a field @code{fv}
7980 in each structure. Here is an example of what you might type:
7990 @node Output Formats
7991 @section Output Formats
7993 @cindex formatted output
7994 @cindex output formats
7995 By default, @value{GDBN} prints a value according to its data type. Sometimes
7996 this is not what you want. For example, you might want to print a number
7997 in hex, or a pointer in decimal. Or you might want to view data in memory
7998 at a certain address as a character string or as an instruction. To do
7999 these things, specify an @dfn{output format} when you print a value.
8001 The simplest use of output formats is to say how to print a value
8002 already computed. This is done by starting the arguments of the
8003 @code{print} command with a slash and a format letter. The format
8004 letters supported are:
8008 Regard the bits of the value as an integer, and print the integer in
8012 Print as integer in signed decimal.
8015 Print as integer in unsigned decimal.
8018 Print as integer in octal.
8021 Print as integer in binary. The letter @samp{t} stands for ``two''.
8022 @footnote{@samp{b} cannot be used because these format letters are also
8023 used with the @code{x} command, where @samp{b} stands for ``byte'';
8024 see @ref{Memory,,Examining Memory}.}
8027 @cindex unknown address, locating
8028 @cindex locate address
8029 Print as an address, both absolute in hexadecimal and as an offset from
8030 the nearest preceding symbol. You can use this format used to discover
8031 where (in what function) an unknown address is located:
8034 (@value{GDBP}) p/a 0x54320
8035 $3 = 0x54320 <_initialize_vx+396>
8039 The command @code{info symbol 0x54320} yields similar results.
8040 @xref{Symbols, info symbol}.
8043 Regard as an integer and print it as a character constant. This
8044 prints both the numerical value and its character representation. The
8045 character representation is replaced with the octal escape @samp{\nnn}
8046 for characters outside the 7-bit @sc{ascii} range.
8048 Without this format, @value{GDBN} displays @code{char},
8049 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
8050 constants. Single-byte members of vectors are displayed as integer
8054 Regard the bits of the value as a floating point number and print
8055 using typical floating point syntax.
8058 @cindex printing strings
8059 @cindex printing byte arrays
8060 Regard as a string, if possible. With this format, pointers to single-byte
8061 data are displayed as null-terminated strings and arrays of single-byte data
8062 are displayed as fixed-length strings. Other values are displayed in their
8065 Without this format, @value{GDBN} displays pointers to and arrays of
8066 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
8067 strings. Single-byte members of a vector are displayed as an integer
8071 @cindex raw printing
8072 Print using the @samp{raw} formatting. By default, @value{GDBN} will
8073 use a Python-based pretty-printer, if one is available (@pxref{Pretty
8074 Printing}). This typically results in a higher-level display of the
8075 value's contents. The @samp{r} format bypasses any Python
8076 pretty-printer which might exist.
8079 For example, to print the program counter in hex (@pxref{Registers}), type
8086 Note that no space is required before the slash; this is because command
8087 names in @value{GDBN} cannot contain a slash.
8089 To reprint the last value in the value history with a different format,
8090 you can use the @code{print} command with just a format and no
8091 expression. For example, @samp{p/x} reprints the last value in hex.
8094 @section Examining Memory
8096 You can use the command @code{x} (for ``examine'') to examine memory in
8097 any of several formats, independently of your program's data types.
8099 @cindex examining memory
8101 @kindex x @r{(examine memory)}
8102 @item x/@var{nfu} @var{addr}
8105 Use the @code{x} command to examine memory.
8108 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
8109 much memory to display and how to format it; @var{addr} is an
8110 expression giving the address where you want to start displaying memory.
8111 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
8112 Several commands set convenient defaults for @var{addr}.
8115 @item @var{n}, the repeat count
8116 The repeat count is a decimal integer; the default is 1. It specifies
8117 how much memory (counting by units @var{u}) to display.
8118 @c This really is **decimal**; unaffected by 'set radix' as of GDB
8121 @item @var{f}, the display format
8122 The display format is one of the formats used by @code{print}
8123 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
8124 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
8125 The default is @samp{x} (hexadecimal) initially. The default changes
8126 each time you use either @code{x} or @code{print}.
8128 @item @var{u}, the unit size
8129 The unit size is any of
8135 Halfwords (two bytes).
8137 Words (four bytes). This is the initial default.
8139 Giant words (eight bytes).
8142 Each time you specify a unit size with @code{x}, that size becomes the
8143 default unit the next time you use @code{x}. For the @samp{i} format,
8144 the unit size is ignored and is normally not written. For the @samp{s} format,
8145 the unit size defaults to @samp{b}, unless it is explicitly given.
8146 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
8147 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
8148 Note that the results depend on the programming language of the
8149 current compilation unit. If the language is C, the @samp{s}
8150 modifier will use the UTF-16 encoding while @samp{w} will use
8151 UTF-32. The encoding is set by the programming language and cannot
8154 @item @var{addr}, starting display address
8155 @var{addr} is the address where you want @value{GDBN} to begin displaying
8156 memory. The expression need not have a pointer value (though it may);
8157 it is always interpreted as an integer address of a byte of memory.
8158 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
8159 @var{addr} is usually just after the last address examined---but several
8160 other commands also set the default address: @code{info breakpoints} (to
8161 the address of the last breakpoint listed), @code{info line} (to the
8162 starting address of a line), and @code{print} (if you use it to display
8163 a value from memory).
8166 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
8167 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
8168 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
8169 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
8170 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
8172 Since the letters indicating unit sizes are all distinct from the
8173 letters specifying output formats, you do not have to remember whether
8174 unit size or format comes first; either order works. The output
8175 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
8176 (However, the count @var{n} must come first; @samp{wx4} does not work.)
8178 Even though the unit size @var{u} is ignored for the formats @samp{s}
8179 and @samp{i}, you might still want to use a count @var{n}; for example,
8180 @samp{3i} specifies that you want to see three machine instructions,
8181 including any operands. For convenience, especially when used with
8182 the @code{display} command, the @samp{i} format also prints branch delay
8183 slot instructions, if any, beyond the count specified, which immediately
8184 follow the last instruction that is within the count. The command
8185 @code{disassemble} gives an alternative way of inspecting machine
8186 instructions; see @ref{Machine Code,,Source and Machine Code}.
8188 All the defaults for the arguments to @code{x} are designed to make it
8189 easy to continue scanning memory with minimal specifications each time
8190 you use @code{x}. For example, after you have inspected three machine
8191 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
8192 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
8193 the repeat count @var{n} is used again; the other arguments default as
8194 for successive uses of @code{x}.
8196 When examining machine instructions, the instruction at current program
8197 counter is shown with a @code{=>} marker. For example:
8200 (@value{GDBP}) x/5i $pc-6
8201 0x804837f <main+11>: mov %esp,%ebp
8202 0x8048381 <main+13>: push %ecx
8203 0x8048382 <main+14>: sub $0x4,%esp
8204 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
8205 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
8208 @cindex @code{$_}, @code{$__}, and value history
8209 The addresses and contents printed by the @code{x} command are not saved
8210 in the value history because there is often too much of them and they
8211 would get in the way. Instead, @value{GDBN} makes these values available for
8212 subsequent use in expressions as values of the convenience variables
8213 @code{$_} and @code{$__}. After an @code{x} command, the last address
8214 examined is available for use in expressions in the convenience variable
8215 @code{$_}. The contents of that address, as examined, are available in
8216 the convenience variable @code{$__}.
8218 If the @code{x} command has a repeat count, the address and contents saved
8219 are from the last memory unit printed; this is not the same as the last
8220 address printed if several units were printed on the last line of output.
8222 @cindex remote memory comparison
8223 @cindex verify remote memory image
8224 When you are debugging a program running on a remote target machine
8225 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
8226 remote machine's memory against the executable file you downloaded to
8227 the target. The @code{compare-sections} command is provided for such
8231 @kindex compare-sections
8232 @item compare-sections @r{[}@var{section-name}@r{]}
8233 Compare the data of a loadable section @var{section-name} in the
8234 executable file of the program being debugged with the same section in
8235 the remote machine's memory, and report any mismatches. With no
8236 arguments, compares all loadable sections. This command's
8237 availability depends on the target's support for the @code{"qCRC"}
8242 @section Automatic Display
8243 @cindex automatic display
8244 @cindex display of expressions
8246 If you find that you want to print the value of an expression frequently
8247 (to see how it changes), you might want to add it to the @dfn{automatic
8248 display list} so that @value{GDBN} prints its value each time your program stops.
8249 Each expression added to the list is given a number to identify it;
8250 to remove an expression from the list, you specify that number.
8251 The automatic display looks like this:
8255 3: bar[5] = (struct hack *) 0x3804
8259 This display shows item numbers, expressions and their current values. As with
8260 displays you request manually using @code{x} or @code{print}, you can
8261 specify the output format you prefer; in fact, @code{display} decides
8262 whether to use @code{print} or @code{x} depending your format
8263 specification---it uses @code{x} if you specify either the @samp{i}
8264 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
8268 @item display @var{expr}
8269 Add the expression @var{expr} to the list of expressions to display
8270 each time your program stops. @xref{Expressions, ,Expressions}.
8272 @code{display} does not repeat if you press @key{RET} again after using it.
8274 @item display/@var{fmt} @var{expr}
8275 For @var{fmt} specifying only a display format and not a size or
8276 count, add the expression @var{expr} to the auto-display list but
8277 arrange to display it each time in the specified format @var{fmt}.
8278 @xref{Output Formats,,Output Formats}.
8280 @item display/@var{fmt} @var{addr}
8281 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
8282 number of units, add the expression @var{addr} as a memory address to
8283 be examined each time your program stops. Examining means in effect
8284 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
8287 For example, @samp{display/i $pc} can be helpful, to see the machine
8288 instruction about to be executed each time execution stops (@samp{$pc}
8289 is a common name for the program counter; @pxref{Registers, ,Registers}).
8292 @kindex delete display
8294 @item undisplay @var{dnums}@dots{}
8295 @itemx delete display @var{dnums}@dots{}
8296 Remove items from the list of expressions to display. Specify the
8297 numbers of the displays that you want affected with the command
8298 argument @var{dnums}. It can be a single display number, one of the
8299 numbers shown in the first field of the @samp{info display} display;
8300 or it could be a range of display numbers, as in @code{2-4}.
8302 @code{undisplay} does not repeat if you press @key{RET} after using it.
8303 (Otherwise you would just get the error @samp{No display number @dots{}}.)
8305 @kindex disable display
8306 @item disable display @var{dnums}@dots{}
8307 Disable the display of item numbers @var{dnums}. A disabled display
8308 item is not printed automatically, but is not forgotten. It may be
8309 enabled again later. Specify the numbers of the displays that you
8310 want affected with the command argument @var{dnums}. It can be a
8311 single display number, one of the numbers shown in the first field of
8312 the @samp{info display} display; or it could be a range of display
8313 numbers, as in @code{2-4}.
8315 @kindex enable display
8316 @item enable display @var{dnums}@dots{}
8317 Enable display of item numbers @var{dnums}. It becomes effective once
8318 again in auto display of its expression, until you specify otherwise.
8319 Specify the numbers of the displays that you want affected with the
8320 command argument @var{dnums}. It can be a single display number, one
8321 of the numbers shown in the first field of the @samp{info display}
8322 display; or it could be a range of display numbers, as in @code{2-4}.
8325 Display the current values of the expressions on the list, just as is
8326 done when your program stops.
8328 @kindex info display
8330 Print the list of expressions previously set up to display
8331 automatically, each one with its item number, but without showing the
8332 values. This includes disabled expressions, which are marked as such.
8333 It also includes expressions which would not be displayed right now
8334 because they refer to automatic variables not currently available.
8337 @cindex display disabled out of scope
8338 If a display expression refers to local variables, then it does not make
8339 sense outside the lexical context for which it was set up. Such an
8340 expression is disabled when execution enters a context where one of its
8341 variables is not defined. For example, if you give the command
8342 @code{display last_char} while inside a function with an argument
8343 @code{last_char}, @value{GDBN} displays this argument while your program
8344 continues to stop inside that function. When it stops elsewhere---where
8345 there is no variable @code{last_char}---the display is disabled
8346 automatically. The next time your program stops where @code{last_char}
8347 is meaningful, you can enable the display expression once again.
8349 @node Print Settings
8350 @section Print Settings
8352 @cindex format options
8353 @cindex print settings
8354 @value{GDBN} provides the following ways to control how arrays, structures,
8355 and symbols are printed.
8358 These settings are useful for debugging programs in any language:
8362 @item set print address
8363 @itemx set print address on
8364 @cindex print/don't print memory addresses
8365 @value{GDBN} prints memory addresses showing the location of stack
8366 traces, structure values, pointer values, breakpoints, and so forth,
8367 even when it also displays the contents of those addresses. The default
8368 is @code{on}. For example, this is what a stack frame display looks like with
8369 @code{set print address on}:
8374 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
8376 530 if (lquote != def_lquote)
8380 @item set print address off
8381 Do not print addresses when displaying their contents. For example,
8382 this is the same stack frame displayed with @code{set print address off}:
8386 (@value{GDBP}) set print addr off
8388 #0 set_quotes (lq="<<", rq=">>") at input.c:530
8389 530 if (lquote != def_lquote)
8393 You can use @samp{set print address off} to eliminate all machine
8394 dependent displays from the @value{GDBN} interface. For example, with
8395 @code{print address off}, you should get the same text for backtraces on
8396 all machines---whether or not they involve pointer arguments.
8399 @item show print address
8400 Show whether or not addresses are to be printed.
8403 When @value{GDBN} prints a symbolic address, it normally prints the
8404 closest earlier symbol plus an offset. If that symbol does not uniquely
8405 identify the address (for example, it is a name whose scope is a single
8406 source file), you may need to clarify. One way to do this is with
8407 @code{info line}, for example @samp{info line *0x4537}. Alternately,
8408 you can set @value{GDBN} to print the source file and line number when
8409 it prints a symbolic address:
8412 @item set print symbol-filename on
8413 @cindex source file and line of a symbol
8414 @cindex symbol, source file and line
8415 Tell @value{GDBN} to print the source file name and line number of a
8416 symbol in the symbolic form of an address.
8418 @item set print symbol-filename off
8419 Do not print source file name and line number of a symbol. This is the
8422 @item show print symbol-filename
8423 Show whether or not @value{GDBN} will print the source file name and
8424 line number of a symbol in the symbolic form of an address.
8427 Another situation where it is helpful to show symbol filenames and line
8428 numbers is when disassembling code; @value{GDBN} shows you the line
8429 number and source file that corresponds to each instruction.
8431 Also, you may wish to see the symbolic form only if the address being
8432 printed is reasonably close to the closest earlier symbol:
8435 @item set print max-symbolic-offset @var{max-offset}
8436 @cindex maximum value for offset of closest symbol
8437 Tell @value{GDBN} to only display the symbolic form of an address if the
8438 offset between the closest earlier symbol and the address is less than
8439 @var{max-offset}. The default is 0, which tells @value{GDBN}
8440 to always print the symbolic form of an address if any symbol precedes it.
8442 @item show print max-symbolic-offset
8443 Ask how large the maximum offset is that @value{GDBN} prints in a
8447 @cindex wild pointer, interpreting
8448 @cindex pointer, finding referent
8449 If you have a pointer and you are not sure where it points, try
8450 @samp{set print symbol-filename on}. Then you can determine the name
8451 and source file location of the variable where it points, using
8452 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
8453 For example, here @value{GDBN} shows that a variable @code{ptt} points
8454 at another variable @code{t}, defined in @file{hi2.c}:
8457 (@value{GDBP}) set print symbol-filename on
8458 (@value{GDBP}) p/a ptt
8459 $4 = 0xe008 <t in hi2.c>
8463 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
8464 does not show the symbol name and filename of the referent, even with
8465 the appropriate @code{set print} options turned on.
8468 You can also enable @samp{/a}-like formatting all the time using
8469 @samp{set print symbol on}:
8472 @item set print symbol on
8473 Tell @value{GDBN} to print the symbol corresponding to an address, if
8476 @item set print symbol off
8477 Tell @value{GDBN} not to print the symbol corresponding to an
8478 address. In this mode, @value{GDBN} will still print the symbol
8479 corresponding to pointers to functions. This is the default.
8481 @item show print symbol
8482 Show whether @value{GDBN} will display the symbol corresponding to an
8486 Other settings control how different kinds of objects are printed:
8489 @item set print array
8490 @itemx set print array on
8491 @cindex pretty print arrays
8492 Pretty print arrays. This format is more convenient to read,
8493 but uses more space. The default is off.
8495 @item set print array off
8496 Return to compressed format for arrays.
8498 @item show print array
8499 Show whether compressed or pretty format is selected for displaying
8502 @cindex print array indexes
8503 @item set print array-indexes
8504 @itemx set print array-indexes on
8505 Print the index of each element when displaying arrays. May be more
8506 convenient to locate a given element in the array or quickly find the
8507 index of a given element in that printed array. The default is off.
8509 @item set print array-indexes off
8510 Stop printing element indexes when displaying arrays.
8512 @item show print array-indexes
8513 Show whether the index of each element is printed when displaying
8516 @item set print elements @var{number-of-elements}
8517 @cindex number of array elements to print
8518 @cindex limit on number of printed array elements
8519 Set a limit on how many elements of an array @value{GDBN} will print.
8520 If @value{GDBN} is printing a large array, it stops printing after it has
8521 printed the number of elements set by the @code{set print elements} command.
8522 This limit also applies to the display of strings.
8523 When @value{GDBN} starts, this limit is set to 200.
8524 Setting @var{number-of-elements} to zero means that the printing is unlimited.
8526 @item show print elements
8527 Display the number of elements of a large array that @value{GDBN} will print.
8528 If the number is 0, then the printing is unlimited.
8530 @item set print frame-arguments @var{value}
8531 @kindex set print frame-arguments
8532 @cindex printing frame argument values
8533 @cindex print all frame argument values
8534 @cindex print frame argument values for scalars only
8535 @cindex do not print frame argument values
8536 This command allows to control how the values of arguments are printed
8537 when the debugger prints a frame (@pxref{Frames}). The possible
8542 The values of all arguments are printed.
8545 Print the value of an argument only if it is a scalar. The value of more
8546 complex arguments such as arrays, structures, unions, etc, is replaced
8547 by @code{@dots{}}. This is the default. Here is an example where
8548 only scalar arguments are shown:
8551 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
8556 None of the argument values are printed. Instead, the value of each argument
8557 is replaced by @code{@dots{}}. In this case, the example above now becomes:
8560 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
8565 By default, only scalar arguments are printed. This command can be used
8566 to configure the debugger to print the value of all arguments, regardless
8567 of their type. However, it is often advantageous to not print the value
8568 of more complex parameters. For instance, it reduces the amount of
8569 information printed in each frame, making the backtrace more readable.
8570 Also, it improves performance when displaying Ada frames, because
8571 the computation of large arguments can sometimes be CPU-intensive,
8572 especially in large applications. Setting @code{print frame-arguments}
8573 to @code{scalars} (the default) or @code{none} avoids this computation,
8574 thus speeding up the display of each Ada frame.
8576 @item show print frame-arguments
8577 Show how the value of arguments should be displayed when printing a frame.
8579 @anchor{set print entry-values}
8580 @item set print entry-values @var{value}
8581 @kindex set print entry-values
8582 Set printing of frame argument values at function entry. In some cases
8583 @value{GDBN} can determine the value of function argument which was passed by
8584 the function caller, even if the value was modified inside the called function
8585 and therefore is different. With optimized code, the current value could be
8586 unavailable, but the entry value may still be known.
8588 The default value is @code{default} (see below for its description). Older
8589 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
8590 this feature will behave in the @code{default} setting the same way as with the
8593 This functionality is currently supported only by DWARF 2 debugging format and
8594 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
8595 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
8598 The @var{value} parameter can be one of the following:
8602 Print only actual parameter values, never print values from function entry
8606 #0 different (val=6)
8607 #0 lost (val=<optimized out>)
8609 #0 invalid (val=<optimized out>)
8613 Print only parameter values from function entry point. The actual parameter
8614 values are never printed.
8616 #0 equal (val@@entry=5)
8617 #0 different (val@@entry=5)
8618 #0 lost (val@@entry=5)
8619 #0 born (val@@entry=<optimized out>)
8620 #0 invalid (val@@entry=<optimized out>)
8624 Print only parameter values from function entry point. If value from function
8625 entry point is not known while the actual value is known, print the actual
8626 value for such parameter.
8628 #0 equal (val@@entry=5)
8629 #0 different (val@@entry=5)
8630 #0 lost (val@@entry=5)
8632 #0 invalid (val@@entry=<optimized out>)
8636 Print actual parameter values. If actual parameter value is not known while
8637 value from function entry point is known, print the entry point value for such
8641 #0 different (val=6)
8642 #0 lost (val@@entry=5)
8644 #0 invalid (val=<optimized out>)
8648 Always print both the actual parameter value and its value from function entry
8649 point, even if values of one or both are not available due to compiler
8652 #0 equal (val=5, val@@entry=5)
8653 #0 different (val=6, val@@entry=5)
8654 #0 lost (val=<optimized out>, val@@entry=5)
8655 #0 born (val=10, val@@entry=<optimized out>)
8656 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
8660 Print the actual parameter value if it is known and also its value from
8661 function entry point if it is known. If neither is known, print for the actual
8662 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
8663 values are known and identical, print the shortened
8664 @code{param=param@@entry=VALUE} notation.
8666 #0 equal (val=val@@entry=5)
8667 #0 different (val=6, val@@entry=5)
8668 #0 lost (val@@entry=5)
8670 #0 invalid (val=<optimized out>)
8674 Always print the actual parameter value. Print also its value from function
8675 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
8676 if both values are known and identical, print the shortened
8677 @code{param=param@@entry=VALUE} notation.
8679 #0 equal (val=val@@entry=5)
8680 #0 different (val=6, val@@entry=5)
8681 #0 lost (val=<optimized out>, val@@entry=5)
8683 #0 invalid (val=<optimized out>)
8687 For analysis messages on possible failures of frame argument values at function
8688 entry resolution see @ref{set debug entry-values}.
8690 @item show print entry-values
8691 Show the method being used for printing of frame argument values at function
8694 @item set print repeats
8695 @cindex repeated array elements
8696 Set the threshold for suppressing display of repeated array
8697 elements. When the number of consecutive identical elements of an
8698 array exceeds the threshold, @value{GDBN} prints the string
8699 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
8700 identical repetitions, instead of displaying the identical elements
8701 themselves. Setting the threshold to zero will cause all elements to
8702 be individually printed. The default threshold is 10.
8704 @item show print repeats
8705 Display the current threshold for printing repeated identical
8708 @item set print null-stop
8709 @cindex @sc{null} elements in arrays
8710 Cause @value{GDBN} to stop printing the characters of an array when the first
8711 @sc{null} is encountered. This is useful when large arrays actually
8712 contain only short strings.
8715 @item show print null-stop
8716 Show whether @value{GDBN} stops printing an array on the first
8717 @sc{null} character.
8719 @item set print pretty on
8720 @cindex print structures in indented form
8721 @cindex indentation in structure display
8722 Cause @value{GDBN} to print structures in an indented format with one member
8723 per line, like this:
8738 @item set print pretty off
8739 Cause @value{GDBN} to print structures in a compact format, like this:
8743 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
8744 meat = 0x54 "Pork"@}
8749 This is the default format.
8751 @item show print pretty
8752 Show which format @value{GDBN} is using to print structures.
8754 @item set print sevenbit-strings on
8755 @cindex eight-bit characters in strings
8756 @cindex octal escapes in strings
8757 Print using only seven-bit characters; if this option is set,
8758 @value{GDBN} displays any eight-bit characters (in strings or
8759 character values) using the notation @code{\}@var{nnn}. This setting is
8760 best if you are working in English (@sc{ascii}) and you use the
8761 high-order bit of characters as a marker or ``meta'' bit.
8763 @item set print sevenbit-strings off
8764 Print full eight-bit characters. This allows the use of more
8765 international character sets, and is the default.
8767 @item show print sevenbit-strings
8768 Show whether or not @value{GDBN} is printing only seven-bit characters.
8770 @item set print union on
8771 @cindex unions in structures, printing
8772 Tell @value{GDBN} to print unions which are contained in structures
8773 and other unions. This is the default setting.
8775 @item set print union off
8776 Tell @value{GDBN} not to print unions which are contained in
8777 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
8780 @item show print union
8781 Ask @value{GDBN} whether or not it will print unions which are contained in
8782 structures and other unions.
8784 For example, given the declarations
8787 typedef enum @{Tree, Bug@} Species;
8788 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
8789 typedef enum @{Caterpillar, Cocoon, Butterfly@}
8800 struct thing foo = @{Tree, @{Acorn@}@};
8804 with @code{set print union on} in effect @samp{p foo} would print
8807 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
8811 and with @code{set print union off} in effect it would print
8814 $1 = @{it = Tree, form = @{...@}@}
8818 @code{set print union} affects programs written in C-like languages
8824 These settings are of interest when debugging C@t{++} programs:
8827 @cindex demangling C@t{++} names
8828 @item set print demangle
8829 @itemx set print demangle on
8830 Print C@t{++} names in their source form rather than in the encoded
8831 (``mangled'') form passed to the assembler and linker for type-safe
8832 linkage. The default is on.
8834 @item show print demangle
8835 Show whether C@t{++} names are printed in mangled or demangled form.
8837 @item set print asm-demangle
8838 @itemx set print asm-demangle on
8839 Print C@t{++} names in their source form rather than their mangled form, even
8840 in assembler code printouts such as instruction disassemblies.
8843 @item show print asm-demangle
8844 Show whether C@t{++} names in assembly listings are printed in mangled
8847 @cindex C@t{++} symbol decoding style
8848 @cindex symbol decoding style, C@t{++}
8849 @kindex set demangle-style
8850 @item set demangle-style @var{style}
8851 Choose among several encoding schemes used by different compilers to
8852 represent C@t{++} names. The choices for @var{style} are currently:
8856 Allow @value{GDBN} to choose a decoding style by inspecting your program.
8859 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
8860 This is the default.
8863 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
8866 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
8869 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
8870 @strong{Warning:} this setting alone is not sufficient to allow
8871 debugging @code{cfront}-generated executables. @value{GDBN} would
8872 require further enhancement to permit that.
8875 If you omit @var{style}, you will see a list of possible formats.
8877 @item show demangle-style
8878 Display the encoding style currently in use for decoding C@t{++} symbols.
8880 @item set print object
8881 @itemx set print object on
8882 @cindex derived type of an object, printing
8883 @cindex display derived types
8884 When displaying a pointer to an object, identify the @emph{actual}
8885 (derived) type of the object rather than the @emph{declared} type, using
8886 the virtual function table. Note that the virtual function table is
8887 required---this feature can only work for objects that have run-time
8888 type identification; a single virtual method in the object's declared
8889 type is sufficient. Note that this setting is also taken into account when
8890 working with variable objects via MI (@pxref{GDB/MI}).
8892 @item set print object off
8893 Display only the declared type of objects, without reference to the
8894 virtual function table. This is the default setting.
8896 @item show print object
8897 Show whether actual, or declared, object types are displayed.
8899 @item set print static-members
8900 @itemx set print static-members on
8901 @cindex static members of C@t{++} objects
8902 Print static members when displaying a C@t{++} object. The default is on.
8904 @item set print static-members off
8905 Do not print static members when displaying a C@t{++} object.
8907 @item show print static-members
8908 Show whether C@t{++} static members are printed or not.
8910 @item set print pascal_static-members
8911 @itemx set print pascal_static-members on
8912 @cindex static members of Pascal objects
8913 @cindex Pascal objects, static members display
8914 Print static members when displaying a Pascal object. The default is on.
8916 @item set print pascal_static-members off
8917 Do not print static members when displaying a Pascal object.
8919 @item show print pascal_static-members
8920 Show whether Pascal static members are printed or not.
8922 @c These don't work with HP ANSI C++ yet.
8923 @item set print vtbl
8924 @itemx set print vtbl on
8925 @cindex pretty print C@t{++} virtual function tables
8926 @cindex virtual functions (C@t{++}) display
8927 @cindex VTBL display
8928 Pretty print C@t{++} virtual function tables. The default is off.
8929 (The @code{vtbl} commands do not work on programs compiled with the HP
8930 ANSI C@t{++} compiler (@code{aCC}).)
8932 @item set print vtbl off
8933 Do not pretty print C@t{++} virtual function tables.
8935 @item show print vtbl
8936 Show whether C@t{++} virtual function tables are pretty printed, or not.
8939 @node Pretty Printing
8940 @section Pretty Printing
8942 @value{GDBN} provides a mechanism to allow pretty-printing of values using
8943 Python code. It greatly simplifies the display of complex objects. This
8944 mechanism works for both MI and the CLI.
8947 * Pretty-Printer Introduction:: Introduction to pretty-printers
8948 * Pretty-Printer Example:: An example pretty-printer
8949 * Pretty-Printer Commands:: Pretty-printer commands
8952 @node Pretty-Printer Introduction
8953 @subsection Pretty-Printer Introduction
8955 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
8956 registered for the value. If there is then @value{GDBN} invokes the
8957 pretty-printer to print the value. Otherwise the value is printed normally.
8959 Pretty-printers are normally named. This makes them easy to manage.
8960 The @samp{info pretty-printer} command will list all the installed
8961 pretty-printers with their names.
8962 If a pretty-printer can handle multiple data types, then its
8963 @dfn{subprinters} are the printers for the individual data types.
8964 Each such subprinter has its own name.
8965 The format of the name is @var{printer-name};@var{subprinter-name}.
8967 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
8968 Typically they are automatically loaded and registered when the corresponding
8969 debug information is loaded, thus making them available without having to
8970 do anything special.
8972 There are three places where a pretty-printer can be registered.
8976 Pretty-printers registered globally are available when debugging
8980 Pretty-printers registered with a program space are available only
8981 when debugging that program.
8982 @xref{Progspaces In Python}, for more details on program spaces in Python.
8985 Pretty-printers registered with an objfile are loaded and unloaded
8986 with the corresponding objfile (e.g., shared library).
8987 @xref{Objfiles In Python}, for more details on objfiles in Python.
8990 @xref{Selecting Pretty-Printers}, for further information on how
8991 pretty-printers are selected,
8993 @xref{Writing a Pretty-Printer}, for implementing pretty printers
8996 @node Pretty-Printer Example
8997 @subsection Pretty-Printer Example
8999 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
9002 (@value{GDBP}) print s
9004 static npos = 4294967295,
9006 <std::allocator<char>> = @{
9007 <__gnu_cxx::new_allocator<char>> = @{
9008 <No data fields>@}, <No data fields>
9010 members of std::basic_string<char, std::char_traits<char>,
9011 std::allocator<char> >::_Alloc_hider:
9012 _M_p = 0x804a014 "abcd"
9017 With a pretty-printer for @code{std::string} only the contents are printed:
9020 (@value{GDBP}) print s
9024 @node Pretty-Printer Commands
9025 @subsection Pretty-Printer Commands
9026 @cindex pretty-printer commands
9029 @kindex info pretty-printer
9030 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9031 Print the list of installed pretty-printers.
9032 This includes disabled pretty-printers, which are marked as such.
9034 @var{object-regexp} is a regular expression matching the objects
9035 whose pretty-printers to list.
9036 Objects can be @code{global}, the program space's file
9037 (@pxref{Progspaces In Python}),
9038 and the object files within that program space (@pxref{Objfiles In Python}).
9039 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
9040 looks up a printer from these three objects.
9042 @var{name-regexp} is a regular expression matching the name of the printers
9045 @kindex disable pretty-printer
9046 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9047 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9048 A disabled pretty-printer is not forgotten, it may be enabled again later.
9050 @kindex enable pretty-printer
9051 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9052 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9057 Suppose we have three pretty-printers installed: one from library1.so
9058 named @code{foo} that prints objects of type @code{foo}, and
9059 another from library2.so named @code{bar} that prints two types of objects,
9060 @code{bar1} and @code{bar2}.
9063 (gdb) info pretty-printer
9070 (gdb) info pretty-printer library2
9075 (gdb) disable pretty-printer library1
9077 2 of 3 printers enabled
9078 (gdb) info pretty-printer
9085 (gdb) disable pretty-printer library2 bar:bar1
9087 1 of 3 printers enabled
9088 (gdb) info pretty-printer library2
9095 (gdb) disable pretty-printer library2 bar
9097 0 of 3 printers enabled
9098 (gdb) info pretty-printer library2
9107 Note that for @code{bar} the entire printer can be disabled,
9108 as can each individual subprinter.
9111 @section Value History
9113 @cindex value history
9114 @cindex history of values printed by @value{GDBN}
9115 Values printed by the @code{print} command are saved in the @value{GDBN}
9116 @dfn{value history}. This allows you to refer to them in other expressions.
9117 Values are kept until the symbol table is re-read or discarded
9118 (for example with the @code{file} or @code{symbol-file} commands).
9119 When the symbol table changes, the value history is discarded,
9120 since the values may contain pointers back to the types defined in the
9125 @cindex history number
9126 The values printed are given @dfn{history numbers} by which you can
9127 refer to them. These are successive integers starting with one.
9128 @code{print} shows you the history number assigned to a value by
9129 printing @samp{$@var{num} = } before the value; here @var{num} is the
9132 To refer to any previous value, use @samp{$} followed by the value's
9133 history number. The way @code{print} labels its output is designed to
9134 remind you of this. Just @code{$} refers to the most recent value in
9135 the history, and @code{$$} refers to the value before that.
9136 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
9137 is the value just prior to @code{$$}, @code{$$1} is equivalent to
9138 @code{$$}, and @code{$$0} is equivalent to @code{$}.
9140 For example, suppose you have just printed a pointer to a structure and
9141 want to see the contents of the structure. It suffices to type
9147 If you have a chain of structures where the component @code{next} points
9148 to the next one, you can print the contents of the next one with this:
9155 You can print successive links in the chain by repeating this
9156 command---which you can do by just typing @key{RET}.
9158 Note that the history records values, not expressions. If the value of
9159 @code{x} is 4 and you type these commands:
9167 then the value recorded in the value history by the @code{print} command
9168 remains 4 even though the value of @code{x} has changed.
9173 Print the last ten values in the value history, with their item numbers.
9174 This is like @samp{p@ $$9} repeated ten times, except that @code{show
9175 values} does not change the history.
9177 @item show values @var{n}
9178 Print ten history values centered on history item number @var{n}.
9181 Print ten history values just after the values last printed. If no more
9182 values are available, @code{show values +} produces no display.
9185 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
9186 same effect as @samp{show values +}.
9188 @node Convenience Vars
9189 @section Convenience Variables
9191 @cindex convenience variables
9192 @cindex user-defined variables
9193 @value{GDBN} provides @dfn{convenience variables} that you can use within
9194 @value{GDBN} to hold on to a value and refer to it later. These variables
9195 exist entirely within @value{GDBN}; they are not part of your program, and
9196 setting a convenience variable has no direct effect on further execution
9197 of your program. That is why you can use them freely.
9199 Convenience variables are prefixed with @samp{$}. Any name preceded by
9200 @samp{$} can be used for a convenience variable, unless it is one of
9201 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
9202 (Value history references, in contrast, are @emph{numbers} preceded
9203 by @samp{$}. @xref{Value History, ,Value History}.)
9205 You can save a value in a convenience variable with an assignment
9206 expression, just as you would set a variable in your program.
9210 set $foo = *object_ptr
9214 would save in @code{$foo} the value contained in the object pointed to by
9217 Using a convenience variable for the first time creates it, but its
9218 value is @code{void} until you assign a new value. You can alter the
9219 value with another assignment at any time.
9221 Convenience variables have no fixed types. You can assign a convenience
9222 variable any type of value, including structures and arrays, even if
9223 that variable already has a value of a different type. The convenience
9224 variable, when used as an expression, has the type of its current value.
9227 @kindex show convenience
9228 @cindex show all user variables and functions
9229 @item show convenience
9230 Print a list of convenience variables used so far, and their values,
9231 as well as a list of the convenience functions.
9232 Abbreviated @code{show conv}.
9234 @kindex init-if-undefined
9235 @cindex convenience variables, initializing
9236 @item init-if-undefined $@var{variable} = @var{expression}
9237 Set a convenience variable if it has not already been set. This is useful
9238 for user-defined commands that keep some state. It is similar, in concept,
9239 to using local static variables with initializers in C (except that
9240 convenience variables are global). It can also be used to allow users to
9241 override default values used in a command script.
9243 If the variable is already defined then the expression is not evaluated so
9244 any side-effects do not occur.
9247 One of the ways to use a convenience variable is as a counter to be
9248 incremented or a pointer to be advanced. For example, to print
9249 a field from successive elements of an array of structures:
9253 print bar[$i++]->contents
9257 Repeat that command by typing @key{RET}.
9259 Some convenience variables are created automatically by @value{GDBN} and given
9260 values likely to be useful.
9263 @vindex $_@r{, convenience variable}
9265 The variable @code{$_} is automatically set by the @code{x} command to
9266 the last address examined (@pxref{Memory, ,Examining Memory}). Other
9267 commands which provide a default address for @code{x} to examine also
9268 set @code{$_} to that address; these commands include @code{info line}
9269 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
9270 except when set by the @code{x} command, in which case it is a pointer
9271 to the type of @code{$__}.
9273 @vindex $__@r{, convenience variable}
9275 The variable @code{$__} is automatically set by the @code{x} command
9276 to the value found in the last address examined. Its type is chosen
9277 to match the format in which the data was printed.
9280 @vindex $_exitcode@r{, convenience variable}
9281 The variable @code{$_exitcode} is automatically set to the exit code when
9282 the program being debugged terminates.
9285 @itemx $_probe_arg0@dots{}$_probe_arg11
9286 Arguments to a static probe. @xref{Static Probe Points}.
9289 @vindex $_sdata@r{, inspect, convenience variable}
9290 The variable @code{$_sdata} contains extra collected static tracepoint
9291 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
9292 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
9293 if extra static tracepoint data has not been collected.
9296 @vindex $_siginfo@r{, convenience variable}
9297 The variable @code{$_siginfo} contains extra signal information
9298 (@pxref{extra signal information}). Note that @code{$_siginfo}
9299 could be empty, if the application has not yet received any signals.
9300 For example, it will be empty before you execute the @code{run} command.
9303 @vindex $_tlb@r{, convenience variable}
9304 The variable @code{$_tlb} is automatically set when debugging
9305 applications running on MS-Windows in native mode or connected to
9306 gdbserver that supports the @code{qGetTIBAddr} request.
9307 @xref{General Query Packets}.
9308 This variable contains the address of the thread information block.
9312 On HP-UX systems, if you refer to a function or variable name that
9313 begins with a dollar sign, @value{GDBN} searches for a user or system
9314 name first, before it searches for a convenience variable.
9316 @node Convenience Funs
9317 @section Convenience Functions
9319 @cindex convenience functions
9320 @value{GDBN} also supplies some @dfn{convenience functions}. These
9321 have a syntax similar to convenience variables. A convenience
9322 function can be used in an expression just like an ordinary function;
9323 however, a convenience function is implemented internally to
9326 These functions require @value{GDBN} to be configured with
9327 @code{Python} support.
9331 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
9332 @findex $_memeq@r{, convenience function}
9333 Returns one if the @var{length} bytes at the addresses given by
9334 @var{buf1} and @var{buf2} are equal.
9335 Otherwise it returns zero.
9337 @item $_regex(@var{str}, @var{regex})
9338 @findex $_regex@r{, convenience function}
9339 Returns one if the string @var{str} matches the regular expression
9340 @var{regex}. Otherwise it returns zero.
9341 The syntax of the regular expression is that specified by @code{Python}'s
9342 regular expression support.
9344 @item $_streq(@var{str1}, @var{str2})
9345 @findex $_streq@r{, convenience function}
9346 Returns one if the strings @var{str1} and @var{str2} are equal.
9347 Otherwise it returns zero.
9349 @item $_strlen(@var{str})
9350 @findex $_strlen@r{, convenience function}
9351 Returns the length of string @var{str}.
9355 @value{GDBN} provides the ability to list and get help on
9356 convenience functions.
9360 @kindex help function
9361 @cindex show all convenience functions
9362 Print a list of all convenience functions.
9369 You can refer to machine register contents, in expressions, as variables
9370 with names starting with @samp{$}. The names of registers are different
9371 for each machine; use @code{info registers} to see the names used on
9375 @kindex info registers
9376 @item info registers
9377 Print the names and values of all registers except floating-point
9378 and vector registers (in the selected stack frame).
9380 @kindex info all-registers
9381 @cindex floating point registers
9382 @item info all-registers
9383 Print the names and values of all registers, including floating-point
9384 and vector registers (in the selected stack frame).
9386 @item info registers @var{regname} @dots{}
9387 Print the @dfn{relativized} value of each specified register @var{regname}.
9388 As discussed in detail below, register values are normally relative to
9389 the selected stack frame. @var{regname} may be any register name valid on
9390 the machine you are using, with or without the initial @samp{$}.
9393 @cindex stack pointer register
9394 @cindex program counter register
9395 @cindex process status register
9396 @cindex frame pointer register
9397 @cindex standard registers
9398 @value{GDBN} has four ``standard'' register names that are available (in
9399 expressions) on most machines---whenever they do not conflict with an
9400 architecture's canonical mnemonics for registers. The register names
9401 @code{$pc} and @code{$sp} are used for the program counter register and
9402 the stack pointer. @code{$fp} is used for a register that contains a
9403 pointer to the current stack frame, and @code{$ps} is used for a
9404 register that contains the processor status. For example,
9405 you could print the program counter in hex with
9412 or print the instruction to be executed next with
9419 or add four to the stack pointer@footnote{This is a way of removing
9420 one word from the stack, on machines where stacks grow downward in
9421 memory (most machines, nowadays). This assumes that the innermost
9422 stack frame is selected; setting @code{$sp} is not allowed when other
9423 stack frames are selected. To pop entire frames off the stack,
9424 regardless of machine architecture, use @code{return};
9425 see @ref{Returning, ,Returning from a Function}.} with
9431 Whenever possible, these four standard register names are available on
9432 your machine even though the machine has different canonical mnemonics,
9433 so long as there is no conflict. The @code{info registers} command
9434 shows the canonical names. For example, on the SPARC, @code{info
9435 registers} displays the processor status register as @code{$psr} but you
9436 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
9437 is an alias for the @sc{eflags} register.
9439 @value{GDBN} always considers the contents of an ordinary register as an
9440 integer when the register is examined in this way. Some machines have
9441 special registers which can hold nothing but floating point; these
9442 registers are considered to have floating point values. There is no way
9443 to refer to the contents of an ordinary register as floating point value
9444 (although you can @emph{print} it as a floating point value with
9445 @samp{print/f $@var{regname}}).
9447 Some registers have distinct ``raw'' and ``virtual'' data formats. This
9448 means that the data format in which the register contents are saved by
9449 the operating system is not the same one that your program normally
9450 sees. For example, the registers of the 68881 floating point
9451 coprocessor are always saved in ``extended'' (raw) format, but all C
9452 programs expect to work with ``double'' (virtual) format. In such
9453 cases, @value{GDBN} normally works with the virtual format only (the format
9454 that makes sense for your program), but the @code{info registers} command
9455 prints the data in both formats.
9457 @cindex SSE registers (x86)
9458 @cindex MMX registers (x86)
9459 Some machines have special registers whose contents can be interpreted
9460 in several different ways. For example, modern x86-based machines
9461 have SSE and MMX registers that can hold several values packed
9462 together in several different formats. @value{GDBN} refers to such
9463 registers in @code{struct} notation:
9466 (@value{GDBP}) print $xmm1
9468 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
9469 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
9470 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
9471 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
9472 v4_int32 = @{0, 20657912, 11, 13@},
9473 v2_int64 = @{88725056443645952, 55834574859@},
9474 uint128 = 0x0000000d0000000b013b36f800000000
9479 To set values of such registers, you need to tell @value{GDBN} which
9480 view of the register you wish to change, as if you were assigning
9481 value to a @code{struct} member:
9484 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
9487 Normally, register values are relative to the selected stack frame
9488 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
9489 value that the register would contain if all stack frames farther in
9490 were exited and their saved registers restored. In order to see the
9491 true contents of hardware registers, you must select the innermost
9492 frame (with @samp{frame 0}).
9494 However, @value{GDBN} must deduce where registers are saved, from the machine
9495 code generated by your compiler. If some registers are not saved, or if
9496 @value{GDBN} is unable to locate the saved registers, the selected stack
9497 frame makes no difference.
9499 @node Floating Point Hardware
9500 @section Floating Point Hardware
9501 @cindex floating point
9503 Depending on the configuration, @value{GDBN} may be able to give
9504 you more information about the status of the floating point hardware.
9509 Display hardware-dependent information about the floating
9510 point unit. The exact contents and layout vary depending on the
9511 floating point chip. Currently, @samp{info float} is supported on
9512 the ARM and x86 machines.
9516 @section Vector Unit
9519 Depending on the configuration, @value{GDBN} may be able to give you
9520 more information about the status of the vector unit.
9525 Display information about the vector unit. The exact contents and
9526 layout vary depending on the hardware.
9529 @node OS Information
9530 @section Operating System Auxiliary Information
9531 @cindex OS information
9533 @value{GDBN} provides interfaces to useful OS facilities that can help
9534 you debug your program.
9536 @cindex @code{ptrace} system call
9537 @cindex @code{struct user} contents
9538 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
9539 machines), it interfaces with the inferior via the @code{ptrace}
9540 system call. The operating system creates a special sata structure,
9541 called @code{struct user}, for this interface. You can use the
9542 command @code{info udot} to display the contents of this data
9548 Display the contents of the @code{struct user} maintained by the OS
9549 kernel for the program being debugged. @value{GDBN} displays the
9550 contents of @code{struct user} as a list of hex numbers, similar to
9551 the @code{examine} command.
9554 @cindex auxiliary vector
9555 @cindex vector, auxiliary
9556 Some operating systems supply an @dfn{auxiliary vector} to programs at
9557 startup. This is akin to the arguments and environment that you
9558 specify for a program, but contains a system-dependent variety of
9559 binary values that tell system libraries important details about the
9560 hardware, operating system, and process. Each value's purpose is
9561 identified by an integer tag; the meanings are well-known but system-specific.
9562 Depending on the configuration and operating system facilities,
9563 @value{GDBN} may be able to show you this information. For remote
9564 targets, this functionality may further depend on the remote stub's
9565 support of the @samp{qXfer:auxv:read} packet, see
9566 @ref{qXfer auxiliary vector read}.
9571 Display the auxiliary vector of the inferior, which can be either a
9572 live process or a core dump file. @value{GDBN} prints each tag value
9573 numerically, and also shows names and text descriptions for recognized
9574 tags. Some values in the vector are numbers, some bit masks, and some
9575 pointers to strings or other data. @value{GDBN} displays each value in the
9576 most appropriate form for a recognized tag, and in hexadecimal for
9577 an unrecognized tag.
9580 On some targets, @value{GDBN} can access operating system-specific
9581 information and show it to you. The types of information available
9582 will differ depending on the type of operating system running on the
9583 target. The mechanism used to fetch the data is described in
9584 @ref{Operating System Information}. For remote targets, this
9585 functionality depends on the remote stub's support of the
9586 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
9590 @item info os @var{infotype}
9592 Display OS information of the requested type.
9594 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
9596 @anchor{linux info os infotypes}
9598 @kindex info os processes
9600 Display the list of processes on the target. For each process,
9601 @value{GDBN} prints the process identifier, the name of the user, the
9602 command corresponding to the process, and the list of processor cores
9603 that the process is currently running on. (To understand what these
9604 properties mean, for this and the following info types, please consult
9605 the general @sc{gnu}/Linux documentation.)
9607 @kindex info os procgroups
9609 Display the list of process groups on the target. For each process,
9610 @value{GDBN} prints the identifier of the process group that it belongs
9611 to, the command corresponding to the process group leader, the process
9612 identifier, and the command line of the process. The list is sorted
9613 first by the process group identifier, then by the process identifier,
9614 so that processes belonging to the same process group are grouped together
9615 and the process group leader is listed first.
9617 @kindex info os threads
9619 Display the list of threads running on the target. For each thread,
9620 @value{GDBN} prints the identifier of the process that the thread
9621 belongs to, the command of the process, the thread identifier, and the
9622 processor core that it is currently running on. The main thread of a
9623 process is not listed.
9625 @kindex info os files
9627 Display the list of open file descriptors on the target. For each
9628 file descriptor, @value{GDBN} prints the identifier of the process
9629 owning the descriptor, the command of the owning process, the value
9630 of the descriptor, and the target of the descriptor.
9632 @kindex info os sockets
9634 Display the list of Internet-domain sockets on the target. For each
9635 socket, @value{GDBN} prints the address and port of the local and
9636 remote endpoints, the current state of the connection, the creator of
9637 the socket, the IP address family of the socket, and the type of the
9642 Display the list of all System V shared-memory regions on the target.
9643 For each shared-memory region, @value{GDBN} prints the region key,
9644 the shared-memory identifier, the access permissions, the size of the
9645 region, the process that created the region, the process that last
9646 attached to or detached from the region, the current number of live
9647 attaches to the region, and the times at which the region was last
9648 attached to, detach from, and changed.
9650 @kindex info os semaphores
9652 Display the list of all System V semaphore sets on the target. For each
9653 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
9654 set identifier, the access permissions, the number of semaphores in the
9655 set, the user and group of the owner and creator of the semaphore set,
9656 and the times at which the semaphore set was operated upon and changed.
9660 Display the list of all System V message queues on the target. For each
9661 message queue, @value{GDBN} prints the message queue key, the message
9662 queue identifier, the access permissions, the current number of bytes
9663 on the queue, the current number of messages on the queue, the processes
9664 that last sent and received a message on the queue, the user and group
9665 of the owner and creator of the message queue, the times at which a
9666 message was last sent and received on the queue, and the time at which
9667 the message queue was last changed.
9669 @kindex info os modules
9671 Display the list of all loaded kernel modules on the target. For each
9672 module, @value{GDBN} prints the module name, the size of the module in
9673 bytes, the number of times the module is used, the dependencies of the
9674 module, the status of the module, and the address of the loaded module
9679 If @var{infotype} is omitted, then list the possible values for
9680 @var{infotype} and the kind of OS information available for each
9681 @var{infotype}. If the target does not return a list of possible
9682 types, this command will report an error.
9685 @node Memory Region Attributes
9686 @section Memory Region Attributes
9687 @cindex memory region attributes
9689 @dfn{Memory region attributes} allow you to describe special handling
9690 required by regions of your target's memory. @value{GDBN} uses
9691 attributes to determine whether to allow certain types of memory
9692 accesses; whether to use specific width accesses; and whether to cache
9693 target memory. By default the description of memory regions is
9694 fetched from the target (if the current target supports this), but the
9695 user can override the fetched regions.
9697 Defined memory regions can be individually enabled and disabled. When a
9698 memory region is disabled, @value{GDBN} uses the default attributes when
9699 accessing memory in that region. Similarly, if no memory regions have
9700 been defined, @value{GDBN} uses the default attributes when accessing
9703 When a memory region is defined, it is given a number to identify it;
9704 to enable, disable, or remove a memory region, you specify that number.
9708 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
9709 Define a memory region bounded by @var{lower} and @var{upper} with
9710 attributes @var{attributes}@dots{}, and add it to the list of regions
9711 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
9712 case: it is treated as the target's maximum memory address.
9713 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
9716 Discard any user changes to the memory regions and use target-supplied
9717 regions, if available, or no regions if the target does not support.
9720 @item delete mem @var{nums}@dots{}
9721 Remove memory regions @var{nums}@dots{} from the list of regions
9722 monitored by @value{GDBN}.
9725 @item disable mem @var{nums}@dots{}
9726 Disable monitoring of memory regions @var{nums}@dots{}.
9727 A disabled memory region is not forgotten.
9728 It may be enabled again later.
9731 @item enable mem @var{nums}@dots{}
9732 Enable monitoring of memory regions @var{nums}@dots{}.
9736 Print a table of all defined memory regions, with the following columns
9740 @item Memory Region Number
9741 @item Enabled or Disabled.
9742 Enabled memory regions are marked with @samp{y}.
9743 Disabled memory regions are marked with @samp{n}.
9746 The address defining the inclusive lower bound of the memory region.
9749 The address defining the exclusive upper bound of the memory region.
9752 The list of attributes set for this memory region.
9757 @subsection Attributes
9759 @subsubsection Memory Access Mode
9760 The access mode attributes set whether @value{GDBN} may make read or
9761 write accesses to a memory region.
9763 While these attributes prevent @value{GDBN} from performing invalid
9764 memory accesses, they do nothing to prevent the target system, I/O DMA,
9765 etc.@: from accessing memory.
9769 Memory is read only.
9771 Memory is write only.
9773 Memory is read/write. This is the default.
9776 @subsubsection Memory Access Size
9777 The access size attribute tells @value{GDBN} to use specific sized
9778 accesses in the memory region. Often memory mapped device registers
9779 require specific sized accesses. If no access size attribute is
9780 specified, @value{GDBN} may use accesses of any size.
9784 Use 8 bit memory accesses.
9786 Use 16 bit memory accesses.
9788 Use 32 bit memory accesses.
9790 Use 64 bit memory accesses.
9793 @c @subsubsection Hardware/Software Breakpoints
9794 @c The hardware/software breakpoint attributes set whether @value{GDBN}
9795 @c will use hardware or software breakpoints for the internal breakpoints
9796 @c used by the step, next, finish, until, etc. commands.
9800 @c Always use hardware breakpoints
9801 @c @item swbreak (default)
9804 @subsubsection Data Cache
9805 The data cache attributes set whether @value{GDBN} will cache target
9806 memory. While this generally improves performance by reducing debug
9807 protocol overhead, it can lead to incorrect results because @value{GDBN}
9808 does not know about volatile variables or memory mapped device
9813 Enable @value{GDBN} to cache target memory.
9815 Disable @value{GDBN} from caching target memory. This is the default.
9818 @subsection Memory Access Checking
9819 @value{GDBN} can be instructed to refuse accesses to memory that is
9820 not explicitly described. This can be useful if accessing such
9821 regions has undesired effects for a specific target, or to provide
9822 better error checking. The following commands control this behaviour.
9825 @kindex set mem inaccessible-by-default
9826 @item set mem inaccessible-by-default [on|off]
9827 If @code{on} is specified, make @value{GDBN} treat memory not
9828 explicitly described by the memory ranges as non-existent and refuse accesses
9829 to such memory. The checks are only performed if there's at least one
9830 memory range defined. If @code{off} is specified, make @value{GDBN}
9831 treat the memory not explicitly described by the memory ranges as RAM.
9832 The default value is @code{on}.
9833 @kindex show mem inaccessible-by-default
9834 @item show mem inaccessible-by-default
9835 Show the current handling of accesses to unknown memory.
9839 @c @subsubsection Memory Write Verification
9840 @c The memory write verification attributes set whether @value{GDBN}
9841 @c will re-reads data after each write to verify the write was successful.
9845 @c @item noverify (default)
9848 @node Dump/Restore Files
9849 @section Copy Between Memory and a File
9850 @cindex dump/restore files
9851 @cindex append data to a file
9852 @cindex dump data to a file
9853 @cindex restore data from a file
9855 You can use the commands @code{dump}, @code{append}, and
9856 @code{restore} to copy data between target memory and a file. The
9857 @code{dump} and @code{append} commands write data to a file, and the
9858 @code{restore} command reads data from a file back into the inferior's
9859 memory. Files may be in binary, Motorola S-record, Intel hex, or
9860 Tektronix Hex format; however, @value{GDBN} can only append to binary
9866 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9867 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
9868 Dump the contents of memory from @var{start_addr} to @var{end_addr},
9869 or the value of @var{expr}, to @var{filename} in the given format.
9871 The @var{format} parameter may be any one of:
9878 Motorola S-record format.
9880 Tektronix Hex format.
9883 @value{GDBN} uses the same definitions of these formats as the
9884 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
9885 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
9889 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9890 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
9891 Append the contents of memory from @var{start_addr} to @var{end_addr},
9892 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
9893 (@value{GDBN} can only append data to files in raw binary form.)
9896 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
9897 Restore the contents of file @var{filename} into memory. The
9898 @code{restore} command can automatically recognize any known @sc{bfd}
9899 file format, except for raw binary. To restore a raw binary file you
9900 must specify the optional keyword @code{binary} after the filename.
9902 If @var{bias} is non-zero, its value will be added to the addresses
9903 contained in the file. Binary files always start at address zero, so
9904 they will be restored at address @var{bias}. Other bfd files have
9905 a built-in location; they will be restored at offset @var{bias}
9908 If @var{start} and/or @var{end} are non-zero, then only data between
9909 file offset @var{start} and file offset @var{end} will be restored.
9910 These offsets are relative to the addresses in the file, before
9911 the @var{bias} argument is applied.
9915 @node Core File Generation
9916 @section How to Produce a Core File from Your Program
9917 @cindex dump core from inferior
9919 A @dfn{core file} or @dfn{core dump} is a file that records the memory
9920 image of a running process and its process status (register values
9921 etc.). Its primary use is post-mortem debugging of a program that
9922 crashed while it ran outside a debugger. A program that crashes
9923 automatically produces a core file, unless this feature is disabled by
9924 the user. @xref{Files}, for information on invoking @value{GDBN} in
9925 the post-mortem debugging mode.
9927 Occasionally, you may wish to produce a core file of the program you
9928 are debugging in order to preserve a snapshot of its state.
9929 @value{GDBN} has a special command for that.
9933 @kindex generate-core-file
9934 @item generate-core-file [@var{file}]
9935 @itemx gcore [@var{file}]
9936 Produce a core dump of the inferior process. The optional argument
9937 @var{file} specifies the file name where to put the core dump. If not
9938 specified, the file name defaults to @file{core.@var{pid}}, where
9939 @var{pid} is the inferior process ID.
9941 Note that this command is implemented only for some systems (as of
9942 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
9945 @node Character Sets
9946 @section Character Sets
9947 @cindex character sets
9949 @cindex translating between character sets
9950 @cindex host character set
9951 @cindex target character set
9953 If the program you are debugging uses a different character set to
9954 represent characters and strings than the one @value{GDBN} uses itself,
9955 @value{GDBN} can automatically translate between the character sets for
9956 you. The character set @value{GDBN} uses we call the @dfn{host
9957 character set}; the one the inferior program uses we call the
9958 @dfn{target character set}.
9960 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
9961 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
9962 remote protocol (@pxref{Remote Debugging}) to debug a program
9963 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
9964 then the host character set is Latin-1, and the target character set is
9965 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
9966 target-charset EBCDIC-US}, then @value{GDBN} translates between
9967 @sc{ebcdic} and Latin 1 as you print character or string values, or use
9968 character and string literals in expressions.
9970 @value{GDBN} has no way to automatically recognize which character set
9971 the inferior program uses; you must tell it, using the @code{set
9972 target-charset} command, described below.
9974 Here are the commands for controlling @value{GDBN}'s character set
9978 @item set target-charset @var{charset}
9979 @kindex set target-charset
9980 Set the current target character set to @var{charset}. To display the
9981 list of supported target character sets, type
9982 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
9984 @item set host-charset @var{charset}
9985 @kindex set host-charset
9986 Set the current host character set to @var{charset}.
9988 By default, @value{GDBN} uses a host character set appropriate to the
9989 system it is running on; you can override that default using the
9990 @code{set host-charset} command. On some systems, @value{GDBN} cannot
9991 automatically determine the appropriate host character set. In this
9992 case, @value{GDBN} uses @samp{UTF-8}.
9994 @value{GDBN} can only use certain character sets as its host character
9995 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
9996 @value{GDBN} will list the host character sets it supports.
9998 @item set charset @var{charset}
10000 Set the current host and target character sets to @var{charset}. As
10001 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
10002 @value{GDBN} will list the names of the character sets that can be used
10003 for both host and target.
10006 @kindex show charset
10007 Show the names of the current host and target character sets.
10009 @item show host-charset
10010 @kindex show host-charset
10011 Show the name of the current host character set.
10013 @item show target-charset
10014 @kindex show target-charset
10015 Show the name of the current target character set.
10017 @item set target-wide-charset @var{charset}
10018 @kindex set target-wide-charset
10019 Set the current target's wide character set to @var{charset}. This is
10020 the character set used by the target's @code{wchar_t} type. To
10021 display the list of supported wide character sets, type
10022 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
10024 @item show target-wide-charset
10025 @kindex show target-wide-charset
10026 Show the name of the current target's wide character set.
10029 Here is an example of @value{GDBN}'s character set support in action.
10030 Assume that the following source code has been placed in the file
10031 @file{charset-test.c}:
10037 = @{72, 101, 108, 108, 111, 44, 32, 119,
10038 111, 114, 108, 100, 33, 10, 0@};
10039 char ibm1047_hello[]
10040 = @{200, 133, 147, 147, 150, 107, 64, 166,
10041 150, 153, 147, 132, 90, 37, 0@};
10045 printf ("Hello, world!\n");
10049 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
10050 containing the string @samp{Hello, world!} followed by a newline,
10051 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
10053 We compile the program, and invoke the debugger on it:
10056 $ gcc -g charset-test.c -o charset-test
10057 $ gdb -nw charset-test
10058 GNU gdb 2001-12-19-cvs
10059 Copyright 2001 Free Software Foundation, Inc.
10064 We can use the @code{show charset} command to see what character sets
10065 @value{GDBN} is currently using to interpret and display characters and
10069 (@value{GDBP}) show charset
10070 The current host and target character set is `ISO-8859-1'.
10074 For the sake of printing this manual, let's use @sc{ascii} as our
10075 initial character set:
10077 (@value{GDBP}) set charset ASCII
10078 (@value{GDBP}) show charset
10079 The current host and target character set is `ASCII'.
10083 Let's assume that @sc{ascii} is indeed the correct character set for our
10084 host system --- in other words, let's assume that if @value{GDBN} prints
10085 characters using the @sc{ascii} character set, our terminal will display
10086 them properly. Since our current target character set is also
10087 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
10090 (@value{GDBP}) print ascii_hello
10091 $1 = 0x401698 "Hello, world!\n"
10092 (@value{GDBP}) print ascii_hello[0]
10097 @value{GDBN} uses the target character set for character and string
10098 literals you use in expressions:
10101 (@value{GDBP}) print '+'
10106 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
10109 @value{GDBN} relies on the user to tell it which character set the
10110 target program uses. If we print @code{ibm1047_hello} while our target
10111 character set is still @sc{ascii}, we get jibberish:
10114 (@value{GDBP}) print ibm1047_hello
10115 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
10116 (@value{GDBP}) print ibm1047_hello[0]
10121 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
10122 @value{GDBN} tells us the character sets it supports:
10125 (@value{GDBP}) set target-charset
10126 ASCII EBCDIC-US IBM1047 ISO-8859-1
10127 (@value{GDBP}) set target-charset
10130 We can select @sc{ibm1047} as our target character set, and examine the
10131 program's strings again. Now the @sc{ascii} string is wrong, but
10132 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
10133 target character set, @sc{ibm1047}, to the host character set,
10134 @sc{ascii}, and they display correctly:
10137 (@value{GDBP}) set target-charset IBM1047
10138 (@value{GDBP}) show charset
10139 The current host character set is `ASCII'.
10140 The current target character set is `IBM1047'.
10141 (@value{GDBP}) print ascii_hello
10142 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
10143 (@value{GDBP}) print ascii_hello[0]
10145 (@value{GDBP}) print ibm1047_hello
10146 $8 = 0x4016a8 "Hello, world!\n"
10147 (@value{GDBP}) print ibm1047_hello[0]
10152 As above, @value{GDBN} uses the target character set for character and
10153 string literals you use in expressions:
10156 (@value{GDBP}) print '+'
10161 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
10164 @node Caching Remote Data
10165 @section Caching Data of Remote Targets
10166 @cindex caching data of remote targets
10168 @value{GDBN} caches data exchanged between the debugger and a
10169 remote target (@pxref{Remote Debugging}). Such caching generally improves
10170 performance, because it reduces the overhead of the remote protocol by
10171 bundling memory reads and writes into large chunks. Unfortunately, simply
10172 caching everything would lead to incorrect results, since @value{GDBN}
10173 does not necessarily know anything about volatile values, memory-mapped I/O
10174 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
10175 memory can be changed @emph{while} a gdb command is executing.
10176 Therefore, by default, @value{GDBN} only caches data
10177 known to be on the stack@footnote{In non-stop mode, it is moderately
10178 rare for a running thread to modify the stack of a stopped thread
10179 in a way that would interfere with a backtrace, and caching of
10180 stack reads provides a significant speed up of remote backtraces.}.
10181 Other regions of memory can be explicitly marked as
10182 cacheable; see @pxref{Memory Region Attributes}.
10185 @kindex set remotecache
10186 @item set remotecache on
10187 @itemx set remotecache off
10188 This option no longer does anything; it exists for compatibility
10191 @kindex show remotecache
10192 @item show remotecache
10193 Show the current state of the obsolete remotecache flag.
10195 @kindex set stack-cache
10196 @item set stack-cache on
10197 @itemx set stack-cache off
10198 Enable or disable caching of stack accesses. When @code{ON}, use
10199 caching. By default, this option is @code{ON}.
10201 @kindex show stack-cache
10202 @item show stack-cache
10203 Show the current state of data caching for memory accesses.
10205 @kindex info dcache
10206 @item info dcache @r{[}line@r{]}
10207 Print the information about the data cache performance. The
10208 information displayed includes the dcache width and depth, and for
10209 each cache line, its number, address, and how many times it was
10210 referenced. This command is useful for debugging the data cache
10213 If a line number is specified, the contents of that line will be
10216 @item set dcache size @var{size}
10217 @cindex dcache size
10218 @kindex set dcache size
10219 Set maximum number of entries in dcache (dcache depth above).
10221 @item set dcache line-size @var{line-size}
10222 @cindex dcache line-size
10223 @kindex set dcache line-size
10224 Set number of bytes each dcache entry caches (dcache width above).
10225 Must be a power of 2.
10227 @item show dcache size
10228 @kindex show dcache size
10229 Show maximum number of dcache entries. See also @ref{Caching Remote Data, info dcache}.
10231 @item show dcache line-size
10232 @kindex show dcache line-size
10233 Show default size of dcache lines. See also @ref{Caching Remote Data, info dcache}.
10237 @node Searching Memory
10238 @section Search Memory
10239 @cindex searching memory
10241 Memory can be searched for a particular sequence of bytes with the
10242 @code{find} command.
10246 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10247 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10248 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
10249 etc. The search begins at address @var{start_addr} and continues for either
10250 @var{len} bytes or through to @var{end_addr} inclusive.
10253 @var{s} and @var{n} are optional parameters.
10254 They may be specified in either order, apart or together.
10257 @item @var{s}, search query size
10258 The size of each search query value.
10264 halfwords (two bytes)
10268 giant words (eight bytes)
10271 All values are interpreted in the current language.
10272 This means, for example, that if the current source language is C/C@t{++}
10273 then searching for the string ``hello'' includes the trailing '\0'.
10275 If the value size is not specified, it is taken from the
10276 value's type in the current language.
10277 This is useful when one wants to specify the search
10278 pattern as a mixture of types.
10279 Note that this means, for example, that in the case of C-like languages
10280 a search for an untyped 0x42 will search for @samp{(int) 0x42}
10281 which is typically four bytes.
10283 @item @var{n}, maximum number of finds
10284 The maximum number of matches to print. The default is to print all finds.
10287 You can use strings as search values. Quote them with double-quotes
10289 The string value is copied into the search pattern byte by byte,
10290 regardless of the endianness of the target and the size specification.
10292 The address of each match found is printed as well as a count of the
10293 number of matches found.
10295 The address of the last value found is stored in convenience variable
10297 A count of the number of matches is stored in @samp{$numfound}.
10299 For example, if stopped at the @code{printf} in this function:
10305 static char hello[] = "hello-hello";
10306 static struct @{ char c; short s; int i; @}
10307 __attribute__ ((packed)) mixed
10308 = @{ 'c', 0x1234, 0x87654321 @};
10309 printf ("%s\n", hello);
10314 you get during debugging:
10317 (gdb) find &hello[0], +sizeof(hello), "hello"
10318 0x804956d <hello.1620+6>
10320 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
10321 0x8049567 <hello.1620>
10322 0x804956d <hello.1620+6>
10324 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
10325 0x8049567 <hello.1620>
10327 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
10328 0x8049560 <mixed.1625>
10330 (gdb) print $numfound
10333 $2 = (void *) 0x8049560
10336 @node Optimized Code
10337 @chapter Debugging Optimized Code
10338 @cindex optimized code, debugging
10339 @cindex debugging optimized code
10341 Almost all compilers support optimization. With optimization
10342 disabled, the compiler generates assembly code that corresponds
10343 directly to your source code, in a simplistic way. As the compiler
10344 applies more powerful optimizations, the generated assembly code
10345 diverges from your original source code. With help from debugging
10346 information generated by the compiler, @value{GDBN} can map from
10347 the running program back to constructs from your original source.
10349 @value{GDBN} is more accurate with optimization disabled. If you
10350 can recompile without optimization, it is easier to follow the
10351 progress of your program during debugging. But, there are many cases
10352 where you may need to debug an optimized version.
10354 When you debug a program compiled with @samp{-g -O}, remember that the
10355 optimizer has rearranged your code; the debugger shows you what is
10356 really there. Do not be too surprised when the execution path does not
10357 exactly match your source file! An extreme example: if you define a
10358 variable, but never use it, @value{GDBN} never sees that
10359 variable---because the compiler optimizes it out of existence.
10361 Some things do not work as well with @samp{-g -O} as with just
10362 @samp{-g}, particularly on machines with instruction scheduling. If in
10363 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
10364 please report it to us as a bug (including a test case!).
10365 @xref{Variables}, for more information about debugging optimized code.
10368 * Inline Functions:: How @value{GDBN} presents inlining
10369 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
10372 @node Inline Functions
10373 @section Inline Functions
10374 @cindex inline functions, debugging
10376 @dfn{Inlining} is an optimization that inserts a copy of the function
10377 body directly at each call site, instead of jumping to a shared
10378 routine. @value{GDBN} displays inlined functions just like
10379 non-inlined functions. They appear in backtraces. You can view their
10380 arguments and local variables, step into them with @code{step}, skip
10381 them with @code{next}, and escape from them with @code{finish}.
10382 You can check whether a function was inlined by using the
10383 @code{info frame} command.
10385 For @value{GDBN} to support inlined functions, the compiler must
10386 record information about inlining in the debug information ---
10387 @value{NGCC} using the @sc{dwarf 2} format does this, and several
10388 other compilers do also. @value{GDBN} only supports inlined functions
10389 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
10390 do not emit two required attributes (@samp{DW_AT_call_file} and
10391 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
10392 function calls with earlier versions of @value{NGCC}. It instead
10393 displays the arguments and local variables of inlined functions as
10394 local variables in the caller.
10396 The body of an inlined function is directly included at its call site;
10397 unlike a non-inlined function, there are no instructions devoted to
10398 the call. @value{GDBN} still pretends that the call site and the
10399 start of the inlined function are different instructions. Stepping to
10400 the call site shows the call site, and then stepping again shows
10401 the first line of the inlined function, even though no additional
10402 instructions are executed.
10404 This makes source-level debugging much clearer; you can see both the
10405 context of the call and then the effect of the call. Only stepping by
10406 a single instruction using @code{stepi} or @code{nexti} does not do
10407 this; single instruction steps always show the inlined body.
10409 There are some ways that @value{GDBN} does not pretend that inlined
10410 function calls are the same as normal calls:
10414 Setting breakpoints at the call site of an inlined function may not
10415 work, because the call site does not contain any code. @value{GDBN}
10416 may incorrectly move the breakpoint to the next line of the enclosing
10417 function, after the call. This limitation will be removed in a future
10418 version of @value{GDBN}; until then, set a breakpoint on an earlier line
10419 or inside the inlined function instead.
10422 @value{GDBN} cannot locate the return value of inlined calls after
10423 using the @code{finish} command. This is a limitation of compiler-generated
10424 debugging information; after @code{finish}, you can step to the next line
10425 and print a variable where your program stored the return value.
10429 @node Tail Call Frames
10430 @section Tail Call Frames
10431 @cindex tail call frames, debugging
10433 Function @code{B} can call function @code{C} in its very last statement. In
10434 unoptimized compilation the call of @code{C} is immediately followed by return
10435 instruction at the end of @code{B} code. Optimizing compiler may replace the
10436 call and return in function @code{B} into one jump to function @code{C}
10437 instead. Such use of a jump instruction is called @dfn{tail call}.
10439 During execution of function @code{C}, there will be no indication in the
10440 function call stack frames that it was tail-called from @code{B}. If function
10441 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
10442 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
10443 some cases @value{GDBN} can determine that @code{C} was tail-called from
10444 @code{B}, and it will then create fictitious call frame for that, with the
10445 return address set up as if @code{B} called @code{C} normally.
10447 This functionality is currently supported only by DWARF 2 debugging format and
10448 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
10449 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
10452 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
10453 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
10457 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
10459 Stack level 1, frame at 0x7fffffffda30:
10460 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
10461 tail call frame, caller of frame at 0x7fffffffda30
10462 source language c++.
10463 Arglist at unknown address.
10464 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
10467 The detection of all the possible code path executions can find them ambiguous.
10468 There is no execution history stored (possible @ref{Reverse Execution} is never
10469 used for this purpose) and the last known caller could have reached the known
10470 callee by multiple different jump sequences. In such case @value{GDBN} still
10471 tries to show at least all the unambiguous top tail callers and all the
10472 unambiguous bottom tail calees, if any.
10475 @anchor{set debug entry-values}
10476 @item set debug entry-values
10477 @kindex set debug entry-values
10478 When set to on, enables printing of analysis messages for both frame argument
10479 values at function entry and tail calls. It will show all the possible valid
10480 tail calls code paths it has considered. It will also print the intersection
10481 of them with the final unambiguous (possibly partial or even empty) code path
10484 @item show debug entry-values
10485 @kindex show debug entry-values
10486 Show the current state of analysis messages printing for both frame argument
10487 values at function entry and tail calls.
10490 The analysis messages for tail calls can for example show why the virtual tail
10491 call frame for function @code{c} has not been recognized (due to the indirect
10492 reference by variable @code{x}):
10495 static void __attribute__((noinline, noclone)) c (void);
10496 void (*x) (void) = c;
10497 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
10498 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
10499 int main (void) @{ x (); return 0; @}
10501 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
10502 DW_TAG_GNU_call_site 0x40039a in main
10504 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
10507 #1 0x000000000040039a in main () at t.c:5
10510 Another possibility is an ambiguous virtual tail call frames resolution:
10514 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
10515 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
10516 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
10517 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
10518 static void __attribute__((noinline, noclone)) b (void)
10519 @{ if (i) c (); else e (); @}
10520 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
10521 int main (void) @{ a (); return 0; @}
10523 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
10524 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
10525 tailcall: reduced: 0x4004d2(a) |
10528 #1 0x00000000004004d2 in a () at t.c:8
10529 #2 0x0000000000400395 in main () at t.c:9
10532 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
10533 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
10535 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
10536 @ifset HAVE_MAKEINFO_CLICK
10537 @set ARROW @click{}
10538 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
10539 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
10541 @ifclear HAVE_MAKEINFO_CLICK
10543 @set CALLSEQ1B @value{CALLSEQ1A}
10544 @set CALLSEQ2B @value{CALLSEQ2A}
10547 Frames #0 and #2 are real, #1 is a virtual tail call frame.
10548 The code can have possible execution paths @value{CALLSEQ1B} or
10549 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
10551 @code{initial:} state shows some random possible calling sequence @value{GDBN}
10552 has found. It then finds another possible calling sequcen - that one is
10553 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
10554 printed as the @code{reduced:} calling sequence. That one could have many
10555 futher @code{compare:} and @code{reduced:} statements as long as there remain
10556 any non-ambiguous sequence entries.
10558 For the frame of function @code{b} in both cases there are different possible
10559 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
10560 also ambigous. The only non-ambiguous frame is the one for function @code{a},
10561 therefore this one is displayed to the user while the ambiguous frames are
10564 There can be also reasons why printing of frame argument values at function
10569 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
10570 static void __attribute__((noinline, noclone)) a (int i);
10571 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
10572 static void __attribute__((noinline, noclone)) a (int i)
10573 @{ if (i) b (i - 1); else c (0); @}
10574 int main (void) @{ a (5); return 0; @}
10577 #0 c (i=i@@entry=0) at t.c:2
10578 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
10579 function "a" at 0x400420 can call itself via tail calls
10580 i=<optimized out>) at t.c:6
10581 #2 0x000000000040036e in main () at t.c:7
10584 @value{GDBN} cannot find out from the inferior state if and how many times did
10585 function @code{a} call itself (via function @code{b}) as these calls would be
10586 tail calls. Such tail calls would modify thue @code{i} variable, therefore
10587 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
10588 prints @code{<optimized out>} instead.
10591 @chapter C Preprocessor Macros
10593 Some languages, such as C and C@t{++}, provide a way to define and invoke
10594 ``preprocessor macros'' which expand into strings of tokens.
10595 @value{GDBN} can evaluate expressions containing macro invocations, show
10596 the result of macro expansion, and show a macro's definition, including
10597 where it was defined.
10599 You may need to compile your program specially to provide @value{GDBN}
10600 with information about preprocessor macros. Most compilers do not
10601 include macros in their debugging information, even when you compile
10602 with the @option{-g} flag. @xref{Compilation}.
10604 A program may define a macro at one point, remove that definition later,
10605 and then provide a different definition after that. Thus, at different
10606 points in the program, a macro may have different definitions, or have
10607 no definition at all. If there is a current stack frame, @value{GDBN}
10608 uses the macros in scope at that frame's source code line. Otherwise,
10609 @value{GDBN} uses the macros in scope at the current listing location;
10612 Whenever @value{GDBN} evaluates an expression, it always expands any
10613 macro invocations present in the expression. @value{GDBN} also provides
10614 the following commands for working with macros explicitly.
10618 @kindex macro expand
10619 @cindex macro expansion, showing the results of preprocessor
10620 @cindex preprocessor macro expansion, showing the results of
10621 @cindex expanding preprocessor macros
10622 @item macro expand @var{expression}
10623 @itemx macro exp @var{expression}
10624 Show the results of expanding all preprocessor macro invocations in
10625 @var{expression}. Since @value{GDBN} simply expands macros, but does
10626 not parse the result, @var{expression} need not be a valid expression;
10627 it can be any string of tokens.
10630 @item macro expand-once @var{expression}
10631 @itemx macro exp1 @var{expression}
10632 @cindex expand macro once
10633 @i{(This command is not yet implemented.)} Show the results of
10634 expanding those preprocessor macro invocations that appear explicitly in
10635 @var{expression}. Macro invocations appearing in that expansion are
10636 left unchanged. This command allows you to see the effect of a
10637 particular macro more clearly, without being confused by further
10638 expansions. Since @value{GDBN} simply expands macros, but does not
10639 parse the result, @var{expression} need not be a valid expression; it
10640 can be any string of tokens.
10643 @cindex macro definition, showing
10644 @cindex definition of a macro, showing
10645 @cindex macros, from debug info
10646 @item info macro [-a|-all] [--] @var{macro}
10647 Show the current definition or all definitions of the named @var{macro},
10648 and describe the source location or compiler command-line where that
10649 definition was established. The optional double dash is to signify the end of
10650 argument processing and the beginning of @var{macro} for non C-like macros where
10651 the macro may begin with a hyphen.
10653 @kindex info macros
10654 @item info macros @var{linespec}
10655 Show all macro definitions that are in effect at the location specified
10656 by @var{linespec}, and describe the source location or compiler
10657 command-line where those definitions were established.
10659 @kindex macro define
10660 @cindex user-defined macros
10661 @cindex defining macros interactively
10662 @cindex macros, user-defined
10663 @item macro define @var{macro} @var{replacement-list}
10664 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
10665 Introduce a definition for a preprocessor macro named @var{macro},
10666 invocations of which are replaced by the tokens given in
10667 @var{replacement-list}. The first form of this command defines an
10668 ``object-like'' macro, which takes no arguments; the second form
10669 defines a ``function-like'' macro, which takes the arguments given in
10672 A definition introduced by this command is in scope in every
10673 expression evaluated in @value{GDBN}, until it is removed with the
10674 @code{macro undef} command, described below. The definition overrides
10675 all definitions for @var{macro} present in the program being debugged,
10676 as well as any previous user-supplied definition.
10678 @kindex macro undef
10679 @item macro undef @var{macro}
10680 Remove any user-supplied definition for the macro named @var{macro}.
10681 This command only affects definitions provided with the @code{macro
10682 define} command, described above; it cannot remove definitions present
10683 in the program being debugged.
10687 List all the macros defined using the @code{macro define} command.
10690 @cindex macros, example of debugging with
10691 Here is a transcript showing the above commands in action. First, we
10692 show our source files:
10697 #include "sample.h"
10700 #define ADD(x) (M + x)
10705 printf ("Hello, world!\n");
10707 printf ("We're so creative.\n");
10709 printf ("Goodbye, world!\n");
10716 Now, we compile the program using the @sc{gnu} C compiler,
10717 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
10718 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
10719 and @option{-gdwarf-4}; we recommend always choosing the most recent
10720 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
10721 includes information about preprocessor macros in the debugging
10725 $ gcc -gdwarf-2 -g3 sample.c -o sample
10729 Now, we start @value{GDBN} on our sample program:
10733 GNU gdb 2002-05-06-cvs
10734 Copyright 2002 Free Software Foundation, Inc.
10735 GDB is free software, @dots{}
10739 We can expand macros and examine their definitions, even when the
10740 program is not running. @value{GDBN} uses the current listing position
10741 to decide which macro definitions are in scope:
10744 (@value{GDBP}) list main
10747 5 #define ADD(x) (M + x)
10752 10 printf ("Hello, world!\n");
10754 12 printf ("We're so creative.\n");
10755 (@value{GDBP}) info macro ADD
10756 Defined at /home/jimb/gdb/macros/play/sample.c:5
10757 #define ADD(x) (M + x)
10758 (@value{GDBP}) info macro Q
10759 Defined at /home/jimb/gdb/macros/play/sample.h:1
10760 included at /home/jimb/gdb/macros/play/sample.c:2
10762 (@value{GDBP}) macro expand ADD(1)
10763 expands to: (42 + 1)
10764 (@value{GDBP}) macro expand-once ADD(1)
10765 expands to: once (M + 1)
10769 In the example above, note that @code{macro expand-once} expands only
10770 the macro invocation explicit in the original text --- the invocation of
10771 @code{ADD} --- but does not expand the invocation of the macro @code{M},
10772 which was introduced by @code{ADD}.
10774 Once the program is running, @value{GDBN} uses the macro definitions in
10775 force at the source line of the current stack frame:
10778 (@value{GDBP}) break main
10779 Breakpoint 1 at 0x8048370: file sample.c, line 10.
10781 Starting program: /home/jimb/gdb/macros/play/sample
10783 Breakpoint 1, main () at sample.c:10
10784 10 printf ("Hello, world!\n");
10788 At line 10, the definition of the macro @code{N} at line 9 is in force:
10791 (@value{GDBP}) info macro N
10792 Defined at /home/jimb/gdb/macros/play/sample.c:9
10794 (@value{GDBP}) macro expand N Q M
10795 expands to: 28 < 42
10796 (@value{GDBP}) print N Q M
10801 As we step over directives that remove @code{N}'s definition, and then
10802 give it a new definition, @value{GDBN} finds the definition (or lack
10803 thereof) in force at each point:
10806 (@value{GDBP}) next
10808 12 printf ("We're so creative.\n");
10809 (@value{GDBP}) info macro N
10810 The symbol `N' has no definition as a C/C++ preprocessor macro
10811 at /home/jimb/gdb/macros/play/sample.c:12
10812 (@value{GDBP}) next
10814 14 printf ("Goodbye, world!\n");
10815 (@value{GDBP}) info macro N
10816 Defined at /home/jimb/gdb/macros/play/sample.c:13
10818 (@value{GDBP}) macro expand N Q M
10819 expands to: 1729 < 42
10820 (@value{GDBP}) print N Q M
10825 In addition to source files, macros can be defined on the compilation command
10826 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
10827 such a way, @value{GDBN} displays the location of their definition as line zero
10828 of the source file submitted to the compiler.
10831 (@value{GDBP}) info macro __STDC__
10832 Defined at /home/jimb/gdb/macros/play/sample.c:0
10839 @chapter Tracepoints
10840 @c This chapter is based on the documentation written by Michael
10841 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
10843 @cindex tracepoints
10844 In some applications, it is not feasible for the debugger to interrupt
10845 the program's execution long enough for the developer to learn
10846 anything helpful about its behavior. If the program's correctness
10847 depends on its real-time behavior, delays introduced by a debugger
10848 might cause the program to change its behavior drastically, or perhaps
10849 fail, even when the code itself is correct. It is useful to be able
10850 to observe the program's behavior without interrupting it.
10852 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
10853 specify locations in the program, called @dfn{tracepoints}, and
10854 arbitrary expressions to evaluate when those tracepoints are reached.
10855 Later, using the @code{tfind} command, you can examine the values
10856 those expressions had when the program hit the tracepoints. The
10857 expressions may also denote objects in memory---structures or arrays,
10858 for example---whose values @value{GDBN} should record; while visiting
10859 a particular tracepoint, you may inspect those objects as if they were
10860 in memory at that moment. However, because @value{GDBN} records these
10861 values without interacting with you, it can do so quickly and
10862 unobtrusively, hopefully not disturbing the program's behavior.
10864 The tracepoint facility is currently available only for remote
10865 targets. @xref{Targets}. In addition, your remote target must know
10866 how to collect trace data. This functionality is implemented in the
10867 remote stub; however, none of the stubs distributed with @value{GDBN}
10868 support tracepoints as of this writing. The format of the remote
10869 packets used to implement tracepoints are described in @ref{Tracepoint
10872 It is also possible to get trace data from a file, in a manner reminiscent
10873 of corefiles; you specify the filename, and use @code{tfind} to search
10874 through the file. @xref{Trace Files}, for more details.
10876 This chapter describes the tracepoint commands and features.
10879 * Set Tracepoints::
10880 * Analyze Collected Data::
10881 * Tracepoint Variables::
10885 @node Set Tracepoints
10886 @section Commands to Set Tracepoints
10888 Before running such a @dfn{trace experiment}, an arbitrary number of
10889 tracepoints can be set. A tracepoint is actually a special type of
10890 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
10891 standard breakpoint commands. For instance, as with breakpoints,
10892 tracepoint numbers are successive integers starting from one, and many
10893 of the commands associated with tracepoints take the tracepoint number
10894 as their argument, to identify which tracepoint to work on.
10896 For each tracepoint, you can specify, in advance, some arbitrary set
10897 of data that you want the target to collect in the trace buffer when
10898 it hits that tracepoint. The collected data can include registers,
10899 local variables, or global data. Later, you can use @value{GDBN}
10900 commands to examine the values these data had at the time the
10901 tracepoint was hit.
10903 Tracepoints do not support every breakpoint feature. Ignore counts on
10904 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
10905 commands when they are hit. Tracepoints may not be thread-specific
10908 @cindex fast tracepoints
10909 Some targets may support @dfn{fast tracepoints}, which are inserted in
10910 a different way (such as with a jump instead of a trap), that is
10911 faster but possibly restricted in where they may be installed.
10913 @cindex static tracepoints
10914 @cindex markers, static tracepoints
10915 @cindex probing markers, static tracepoints
10916 Regular and fast tracepoints are dynamic tracing facilities, meaning
10917 that they can be used to insert tracepoints at (almost) any location
10918 in the target. Some targets may also support controlling @dfn{static
10919 tracepoints} from @value{GDBN}. With static tracing, a set of
10920 instrumentation points, also known as @dfn{markers}, are embedded in
10921 the target program, and can be activated or deactivated by name or
10922 address. These are usually placed at locations which facilitate
10923 investigating what the target is actually doing. @value{GDBN}'s
10924 support for static tracing includes being able to list instrumentation
10925 points, and attach them with @value{GDBN} defined high level
10926 tracepoints that expose the whole range of convenience of
10927 @value{GDBN}'s tracepoints support. Namely, support for collecting
10928 registers values and values of global or local (to the instrumentation
10929 point) variables; tracepoint conditions and trace state variables.
10930 The act of installing a @value{GDBN} static tracepoint on an
10931 instrumentation point, or marker, is referred to as @dfn{probing} a
10932 static tracepoint marker.
10934 @code{gdbserver} supports tracepoints on some target systems.
10935 @xref{Server,,Tracepoints support in @code{gdbserver}}.
10937 This section describes commands to set tracepoints and associated
10938 conditions and actions.
10941 * Create and Delete Tracepoints::
10942 * Enable and Disable Tracepoints::
10943 * Tracepoint Passcounts::
10944 * Tracepoint Conditions::
10945 * Trace State Variables::
10946 * Tracepoint Actions::
10947 * Listing Tracepoints::
10948 * Listing Static Tracepoint Markers::
10949 * Starting and Stopping Trace Experiments::
10950 * Tracepoint Restrictions::
10953 @node Create and Delete Tracepoints
10954 @subsection Create and Delete Tracepoints
10957 @cindex set tracepoint
10959 @item trace @var{location}
10960 The @code{trace} command is very similar to the @code{break} command.
10961 Its argument @var{location} can be a source line, a function name, or
10962 an address in the target program. @xref{Specify Location}. The
10963 @code{trace} command defines a tracepoint, which is a point in the
10964 target program where the debugger will briefly stop, collect some
10965 data, and then allow the program to continue. Setting a tracepoint or
10966 changing its actions takes effect immediately if the remote stub
10967 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
10969 If remote stub doesn't support the @samp{InstallInTrace} feature, all
10970 these changes don't take effect until the next @code{tstart}
10971 command, and once a trace experiment is running, further changes will
10972 not have any effect until the next trace experiment starts. In addition,
10973 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
10974 address is not yet resolved. (This is similar to pending breakpoints.)
10975 Pending tracepoints are not downloaded to the target and not installed
10976 until they are resolved. The resolution of pending tracepoints requires
10977 @value{GDBN} support---when debugging with the remote target, and
10978 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
10979 tracing}), pending tracepoints can not be resolved (and downloaded to
10980 the remote stub) while @value{GDBN} is disconnected.
10982 Here are some examples of using the @code{trace} command:
10985 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
10987 (@value{GDBP}) @b{trace +2} // 2 lines forward
10989 (@value{GDBP}) @b{trace my_function} // first source line of function
10991 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
10993 (@value{GDBP}) @b{trace *0x2117c4} // an address
10997 You can abbreviate @code{trace} as @code{tr}.
10999 @item trace @var{location} if @var{cond}
11000 Set a tracepoint with condition @var{cond}; evaluate the expression
11001 @var{cond} each time the tracepoint is reached, and collect data only
11002 if the value is nonzero---that is, if @var{cond} evaluates as true.
11003 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
11004 information on tracepoint conditions.
11006 @item ftrace @var{location} [ if @var{cond} ]
11007 @cindex set fast tracepoint
11008 @cindex fast tracepoints, setting
11010 The @code{ftrace} command sets a fast tracepoint. For targets that
11011 support them, fast tracepoints will use a more efficient but possibly
11012 less general technique to trigger data collection, such as a jump
11013 instruction instead of a trap, or some sort of hardware support. It
11014 may not be possible to create a fast tracepoint at the desired
11015 location, in which case the command will exit with an explanatory
11018 @value{GDBN} handles arguments to @code{ftrace} exactly as for
11021 On 32-bit x86-architecture systems, fast tracepoints normally need to
11022 be placed at an instruction that is 5 bytes or longer, but can be
11023 placed at 4-byte instructions if the low 64K of memory of the target
11024 program is available to install trampolines. Some Unix-type systems,
11025 such as @sc{gnu}/Linux, exclude low addresses from the program's
11026 address space; but for instance with the Linux kernel it is possible
11027 to let @value{GDBN} use this area by doing a @command{sysctl} command
11028 to set the @code{mmap_min_addr} kernel parameter, as in
11031 sudo sysctl -w vm.mmap_min_addr=32768
11035 which sets the low address to 32K, which leaves plenty of room for
11036 trampolines. The minimum address should be set to a page boundary.
11038 @item strace @var{location} [ if @var{cond} ]
11039 @cindex set static tracepoint
11040 @cindex static tracepoints, setting
11041 @cindex probe static tracepoint marker
11043 The @code{strace} command sets a static tracepoint. For targets that
11044 support it, setting a static tracepoint probes a static
11045 instrumentation point, or marker, found at @var{location}. It may not
11046 be possible to set a static tracepoint at the desired location, in
11047 which case the command will exit with an explanatory message.
11049 @value{GDBN} handles arguments to @code{strace} exactly as for
11050 @code{trace}, with the addition that the user can also specify
11051 @code{-m @var{marker}} as @var{location}. This probes the marker
11052 identified by the @var{marker} string identifier. This identifier
11053 depends on the static tracepoint backend library your program is
11054 using. You can find all the marker identifiers in the @samp{ID} field
11055 of the @code{info static-tracepoint-markers} command output.
11056 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
11057 Markers}. For example, in the following small program using the UST
11063 trace_mark(ust, bar33, "str %s", "FOOBAZ");
11068 the marker id is composed of joining the first two arguments to the
11069 @code{trace_mark} call with a slash, which translates to:
11072 (@value{GDBP}) info static-tracepoint-markers
11073 Cnt Enb ID Address What
11074 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
11080 so you may probe the marker above with:
11083 (@value{GDBP}) strace -m ust/bar33
11086 Static tracepoints accept an extra collect action --- @code{collect
11087 $_sdata}. This collects arbitrary user data passed in the probe point
11088 call to the tracing library. In the UST example above, you'll see
11089 that the third argument to @code{trace_mark} is a printf-like format
11090 string. The user data is then the result of running that formating
11091 string against the following arguments. Note that @code{info
11092 static-tracepoint-markers} command output lists that format string in
11093 the @samp{Data:} field.
11095 You can inspect this data when analyzing the trace buffer, by printing
11096 the $_sdata variable like any other variable available to
11097 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
11100 @cindex last tracepoint number
11101 @cindex recent tracepoint number
11102 @cindex tracepoint number
11103 The convenience variable @code{$tpnum} records the tracepoint number
11104 of the most recently set tracepoint.
11106 @kindex delete tracepoint
11107 @cindex tracepoint deletion
11108 @item delete tracepoint @r{[}@var{num}@r{]}
11109 Permanently delete one or more tracepoints. With no argument, the
11110 default is to delete all tracepoints. Note that the regular
11111 @code{delete} command can remove tracepoints also.
11116 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
11118 (@value{GDBP}) @b{delete trace} // remove all tracepoints
11122 You can abbreviate this command as @code{del tr}.
11125 @node Enable and Disable Tracepoints
11126 @subsection Enable and Disable Tracepoints
11128 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
11131 @kindex disable tracepoint
11132 @item disable tracepoint @r{[}@var{num}@r{]}
11133 Disable tracepoint @var{num}, or all tracepoints if no argument
11134 @var{num} is given. A disabled tracepoint will have no effect during
11135 a trace experiment, but it is not forgotten. You can re-enable
11136 a disabled tracepoint using the @code{enable tracepoint} command.
11137 If the command is issued during a trace experiment and the debug target
11138 has support for disabling tracepoints during a trace experiment, then the
11139 change will be effective immediately. Otherwise, it will be applied to the
11140 next trace experiment.
11142 @kindex enable tracepoint
11143 @item enable tracepoint @r{[}@var{num}@r{]}
11144 Enable tracepoint @var{num}, or all tracepoints. If this command is
11145 issued during a trace experiment and the debug target supports enabling
11146 tracepoints during a trace experiment, then the enabled tracepoints will
11147 become effective immediately. Otherwise, they will become effective the
11148 next time a trace experiment is run.
11151 @node Tracepoint Passcounts
11152 @subsection Tracepoint Passcounts
11156 @cindex tracepoint pass count
11157 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
11158 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
11159 automatically stop a trace experiment. If a tracepoint's passcount is
11160 @var{n}, then the trace experiment will be automatically stopped on
11161 the @var{n}'th time that tracepoint is hit. If the tracepoint number
11162 @var{num} is not specified, the @code{passcount} command sets the
11163 passcount of the most recently defined tracepoint. If no passcount is
11164 given, the trace experiment will run until stopped explicitly by the
11170 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
11171 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
11173 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
11174 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
11175 (@value{GDBP}) @b{trace foo}
11176 (@value{GDBP}) @b{pass 3}
11177 (@value{GDBP}) @b{trace bar}
11178 (@value{GDBP}) @b{pass 2}
11179 (@value{GDBP}) @b{trace baz}
11180 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
11181 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
11182 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
11183 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
11187 @node Tracepoint Conditions
11188 @subsection Tracepoint Conditions
11189 @cindex conditional tracepoints
11190 @cindex tracepoint conditions
11192 The simplest sort of tracepoint collects data every time your program
11193 reaches a specified place. You can also specify a @dfn{condition} for
11194 a tracepoint. A condition is just a Boolean expression in your
11195 programming language (@pxref{Expressions, ,Expressions}). A
11196 tracepoint with a condition evaluates the expression each time your
11197 program reaches it, and data collection happens only if the condition
11200 Tracepoint conditions can be specified when a tracepoint is set, by
11201 using @samp{if} in the arguments to the @code{trace} command.
11202 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
11203 also be set or changed at any time with the @code{condition} command,
11204 just as with breakpoints.
11206 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
11207 the conditional expression itself. Instead, @value{GDBN} encodes the
11208 expression into an agent expression (@pxref{Agent Expressions})
11209 suitable for execution on the target, independently of @value{GDBN}.
11210 Global variables become raw memory locations, locals become stack
11211 accesses, and so forth.
11213 For instance, suppose you have a function that is usually called
11214 frequently, but should not be called after an error has occurred. You
11215 could use the following tracepoint command to collect data about calls
11216 of that function that happen while the error code is propagating
11217 through the program; an unconditional tracepoint could end up
11218 collecting thousands of useless trace frames that you would have to
11222 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
11225 @node Trace State Variables
11226 @subsection Trace State Variables
11227 @cindex trace state variables
11229 A @dfn{trace state variable} is a special type of variable that is
11230 created and managed by target-side code. The syntax is the same as
11231 that for GDB's convenience variables (a string prefixed with ``$''),
11232 but they are stored on the target. They must be created explicitly,
11233 using a @code{tvariable} command. They are always 64-bit signed
11236 Trace state variables are remembered by @value{GDBN}, and downloaded
11237 to the target along with tracepoint information when the trace
11238 experiment starts. There are no intrinsic limits on the number of
11239 trace state variables, beyond memory limitations of the target.
11241 @cindex convenience variables, and trace state variables
11242 Although trace state variables are managed by the target, you can use
11243 them in print commands and expressions as if they were convenience
11244 variables; @value{GDBN} will get the current value from the target
11245 while the trace experiment is running. Trace state variables share
11246 the same namespace as other ``$'' variables, which means that you
11247 cannot have trace state variables with names like @code{$23} or
11248 @code{$pc}, nor can you have a trace state variable and a convenience
11249 variable with the same name.
11253 @item tvariable $@var{name} [ = @var{expression} ]
11255 The @code{tvariable} command creates a new trace state variable named
11256 @code{$@var{name}}, and optionally gives it an initial value of
11257 @var{expression}. @var{expression} is evaluated when this command is
11258 entered; the result will be converted to an integer if possible,
11259 otherwise @value{GDBN} will report an error. A subsequent
11260 @code{tvariable} command specifying the same name does not create a
11261 variable, but instead assigns the supplied initial value to the
11262 existing variable of that name, overwriting any previous initial
11263 value. The default initial value is 0.
11265 @item info tvariables
11266 @kindex info tvariables
11267 List all the trace state variables along with their initial values.
11268 Their current values may also be displayed, if the trace experiment is
11271 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
11272 @kindex delete tvariable
11273 Delete the given trace state variables, or all of them if no arguments
11278 @node Tracepoint Actions
11279 @subsection Tracepoint Action Lists
11283 @cindex tracepoint actions
11284 @item actions @r{[}@var{num}@r{]}
11285 This command will prompt for a list of actions to be taken when the
11286 tracepoint is hit. If the tracepoint number @var{num} is not
11287 specified, this command sets the actions for the one that was most
11288 recently defined (so that you can define a tracepoint and then say
11289 @code{actions} without bothering about its number). You specify the
11290 actions themselves on the following lines, one action at a time, and
11291 terminate the actions list with a line containing just @code{end}. So
11292 far, the only defined actions are @code{collect}, @code{teval}, and
11293 @code{while-stepping}.
11295 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
11296 Commands, ,Breakpoint Command Lists}), except that only the defined
11297 actions are allowed; any other @value{GDBN} command is rejected.
11299 @cindex remove actions from a tracepoint
11300 To remove all actions from a tracepoint, type @samp{actions @var{num}}
11301 and follow it immediately with @samp{end}.
11304 (@value{GDBP}) @b{collect @var{data}} // collect some data
11306 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
11308 (@value{GDBP}) @b{end} // signals the end of actions.
11311 In the following example, the action list begins with @code{collect}
11312 commands indicating the things to be collected when the tracepoint is
11313 hit. Then, in order to single-step and collect additional data
11314 following the tracepoint, a @code{while-stepping} command is used,
11315 followed by the list of things to be collected after each step in a
11316 sequence of single steps. The @code{while-stepping} command is
11317 terminated by its own separate @code{end} command. Lastly, the action
11318 list is terminated by an @code{end} command.
11321 (@value{GDBP}) @b{trace foo}
11322 (@value{GDBP}) @b{actions}
11323 Enter actions for tracepoint 1, one per line:
11326 > while-stepping 12
11327 > collect $pc, arr[i]
11332 @kindex collect @r{(tracepoints)}
11333 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
11334 Collect values of the given expressions when the tracepoint is hit.
11335 This command accepts a comma-separated list of any valid expressions.
11336 In addition to global, static, or local variables, the following
11337 special arguments are supported:
11341 Collect all registers.
11344 Collect all function arguments.
11347 Collect all local variables.
11350 Collect the return address. This is helpful if you want to see more
11354 Collects the number of arguments from the static probe at which the
11355 tracepoint is located.
11356 @xref{Static Probe Points}.
11358 @item $_probe_arg@var{n}
11359 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
11360 from the static probe at which the tracepoint is located.
11361 @xref{Static Probe Points}.
11364 @vindex $_sdata@r{, collect}
11365 Collect static tracepoint marker specific data. Only available for
11366 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
11367 Lists}. On the UST static tracepoints library backend, an
11368 instrumentation point resembles a @code{printf} function call. The
11369 tracing library is able to collect user specified data formatted to a
11370 character string using the format provided by the programmer that
11371 instrumented the program. Other backends have similar mechanisms.
11372 Here's an example of a UST marker call:
11375 const char master_name[] = "$your_name";
11376 trace_mark(channel1, marker1, "hello %s", master_name)
11379 In this case, collecting @code{$_sdata} collects the string
11380 @samp{hello $yourname}. When analyzing the trace buffer, you can
11381 inspect @samp{$_sdata} like any other variable available to
11385 You can give several consecutive @code{collect} commands, each one
11386 with a single argument, or one @code{collect} command with several
11387 arguments separated by commas; the effect is the same.
11389 The optional @var{mods} changes the usual handling of the arguments.
11390 @code{s} requests that pointers to chars be handled as strings, in
11391 particular collecting the contents of the memory being pointed at, up
11392 to the first zero. The upper bound is by default the value of the
11393 @code{print elements} variable; if @code{s} is followed by a decimal
11394 number, that is the upper bound instead. So for instance
11395 @samp{collect/s25 mystr} collects as many as 25 characters at
11398 The command @code{info scope} (@pxref{Symbols, info scope}) is
11399 particularly useful for figuring out what data to collect.
11401 @kindex teval @r{(tracepoints)}
11402 @item teval @var{expr1}, @var{expr2}, @dots{}
11403 Evaluate the given expressions when the tracepoint is hit. This
11404 command accepts a comma-separated list of expressions. The results
11405 are discarded, so this is mainly useful for assigning values to trace
11406 state variables (@pxref{Trace State Variables}) without adding those
11407 values to the trace buffer, as would be the case if the @code{collect}
11410 @kindex while-stepping @r{(tracepoints)}
11411 @item while-stepping @var{n}
11412 Perform @var{n} single-step instruction traces after the tracepoint,
11413 collecting new data after each step. The @code{while-stepping}
11414 command is followed by the list of what to collect while stepping
11415 (followed by its own @code{end} command):
11418 > while-stepping 12
11419 > collect $regs, myglobal
11425 Note that @code{$pc} is not automatically collected by
11426 @code{while-stepping}; you need to explicitly collect that register if
11427 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
11430 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
11431 @kindex set default-collect
11432 @cindex default collection action
11433 This variable is a list of expressions to collect at each tracepoint
11434 hit. It is effectively an additional @code{collect} action prepended
11435 to every tracepoint action list. The expressions are parsed
11436 individually for each tracepoint, so for instance a variable named
11437 @code{xyz} may be interpreted as a global for one tracepoint, and a
11438 local for another, as appropriate to the tracepoint's location.
11440 @item show default-collect
11441 @kindex show default-collect
11442 Show the list of expressions that are collected by default at each
11447 @node Listing Tracepoints
11448 @subsection Listing Tracepoints
11451 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
11452 @kindex info tp @r{[}@var{n}@dots{}@r{]}
11453 @cindex information about tracepoints
11454 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
11455 Display information about the tracepoint @var{num}. If you don't
11456 specify a tracepoint number, displays information about all the
11457 tracepoints defined so far. The format is similar to that used for
11458 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
11459 command, simply restricting itself to tracepoints.
11461 A tracepoint's listing may include additional information specific to
11466 its passcount as given by the @code{passcount @var{n}} command
11470 (@value{GDBP}) @b{info trace}
11471 Num Type Disp Enb Address What
11472 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
11474 collect globfoo, $regs
11483 This command can be abbreviated @code{info tp}.
11486 @node Listing Static Tracepoint Markers
11487 @subsection Listing Static Tracepoint Markers
11490 @kindex info static-tracepoint-markers
11491 @cindex information about static tracepoint markers
11492 @item info static-tracepoint-markers
11493 Display information about all static tracepoint markers defined in the
11496 For each marker, the following columns are printed:
11500 An incrementing counter, output to help readability. This is not a
11503 The marker ID, as reported by the target.
11504 @item Enabled or Disabled
11505 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
11506 that are not enabled.
11508 Where the marker is in your program, as a memory address.
11510 Where the marker is in the source for your program, as a file and line
11511 number. If the debug information included in the program does not
11512 allow @value{GDBN} to locate the source of the marker, this column
11513 will be left blank.
11517 In addition, the following information may be printed for each marker:
11521 User data passed to the tracing library by the marker call. In the
11522 UST backend, this is the format string passed as argument to the
11524 @item Static tracepoints probing the marker
11525 The list of static tracepoints attached to the marker.
11529 (@value{GDBP}) info static-tracepoint-markers
11530 Cnt ID Enb Address What
11531 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
11532 Data: number1 %d number2 %d
11533 Probed by static tracepoints: #2
11534 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
11540 @node Starting and Stopping Trace Experiments
11541 @subsection Starting and Stopping Trace Experiments
11544 @kindex tstart [ @var{notes} ]
11545 @cindex start a new trace experiment
11546 @cindex collected data discarded
11548 This command starts the trace experiment, and begins collecting data.
11549 It has the side effect of discarding all the data collected in the
11550 trace buffer during the previous trace experiment. If any arguments
11551 are supplied, they are taken as a note and stored with the trace
11552 experiment's state. The notes may be arbitrary text, and are
11553 especially useful with disconnected tracing in a multi-user context;
11554 the notes can explain what the trace is doing, supply user contact
11555 information, and so forth.
11557 @kindex tstop [ @var{notes} ]
11558 @cindex stop a running trace experiment
11560 This command stops the trace experiment. If any arguments are
11561 supplied, they are recorded with the experiment as a note. This is
11562 useful if you are stopping a trace started by someone else, for
11563 instance if the trace is interfering with the system's behavior and
11564 needs to be stopped quickly.
11566 @strong{Note}: a trace experiment and data collection may stop
11567 automatically if any tracepoint's passcount is reached
11568 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
11571 @cindex status of trace data collection
11572 @cindex trace experiment, status of
11574 This command displays the status of the current trace data
11578 Here is an example of the commands we described so far:
11581 (@value{GDBP}) @b{trace gdb_c_test}
11582 (@value{GDBP}) @b{actions}
11583 Enter actions for tracepoint #1, one per line.
11584 > collect $regs,$locals,$args
11585 > while-stepping 11
11589 (@value{GDBP}) @b{tstart}
11590 [time passes @dots{}]
11591 (@value{GDBP}) @b{tstop}
11594 @anchor{disconnected tracing}
11595 @cindex disconnected tracing
11596 You can choose to continue running the trace experiment even if
11597 @value{GDBN} disconnects from the target, voluntarily or
11598 involuntarily. For commands such as @code{detach}, the debugger will
11599 ask what you want to do with the trace. But for unexpected
11600 terminations (@value{GDBN} crash, network outage), it would be
11601 unfortunate to lose hard-won trace data, so the variable
11602 @code{disconnected-tracing} lets you decide whether the trace should
11603 continue running without @value{GDBN}.
11606 @item set disconnected-tracing on
11607 @itemx set disconnected-tracing off
11608 @kindex set disconnected-tracing
11609 Choose whether a tracing run should continue to run if @value{GDBN}
11610 has disconnected from the target. Note that @code{detach} or
11611 @code{quit} will ask you directly what to do about a running trace no
11612 matter what this variable's setting, so the variable is mainly useful
11613 for handling unexpected situations, such as loss of the network.
11615 @item show disconnected-tracing
11616 @kindex show disconnected-tracing
11617 Show the current choice for disconnected tracing.
11621 When you reconnect to the target, the trace experiment may or may not
11622 still be running; it might have filled the trace buffer in the
11623 meantime, or stopped for one of the other reasons. If it is running,
11624 it will continue after reconnection.
11626 Upon reconnection, the target will upload information about the
11627 tracepoints in effect. @value{GDBN} will then compare that
11628 information to the set of tracepoints currently defined, and attempt
11629 to match them up, allowing for the possibility that the numbers may
11630 have changed due to creation and deletion in the meantime. If one of
11631 the target's tracepoints does not match any in @value{GDBN}, the
11632 debugger will create a new tracepoint, so that you have a number with
11633 which to specify that tracepoint. This matching-up process is
11634 necessarily heuristic, and it may result in useless tracepoints being
11635 created; you may simply delete them if they are of no use.
11637 @cindex circular trace buffer
11638 If your target agent supports a @dfn{circular trace buffer}, then you
11639 can run a trace experiment indefinitely without filling the trace
11640 buffer; when space runs out, the agent deletes already-collected trace
11641 frames, oldest first, until there is enough room to continue
11642 collecting. This is especially useful if your tracepoints are being
11643 hit too often, and your trace gets terminated prematurely because the
11644 buffer is full. To ask for a circular trace buffer, simply set
11645 @samp{circular-trace-buffer} to on. You can set this at any time,
11646 including during tracing; if the agent can do it, it will change
11647 buffer handling on the fly, otherwise it will not take effect until
11651 @item set circular-trace-buffer on
11652 @itemx set circular-trace-buffer off
11653 @kindex set circular-trace-buffer
11654 Choose whether a tracing run should use a linear or circular buffer
11655 for trace data. A linear buffer will not lose any trace data, but may
11656 fill up prematurely, while a circular buffer will discard old trace
11657 data, but it will have always room for the latest tracepoint hits.
11659 @item show circular-trace-buffer
11660 @kindex show circular-trace-buffer
11661 Show the current choice for the trace buffer. Note that this may not
11662 match the agent's current buffer handling, nor is it guaranteed to
11663 match the setting that might have been in effect during a past run,
11664 for instance if you are looking at frames from a trace file.
11669 @item set trace-user @var{text}
11670 @kindex set trace-user
11672 @item show trace-user
11673 @kindex show trace-user
11675 @item set trace-notes @var{text}
11676 @kindex set trace-notes
11677 Set the trace run's notes.
11679 @item show trace-notes
11680 @kindex show trace-notes
11681 Show the trace run's notes.
11683 @item set trace-stop-notes @var{text}
11684 @kindex set trace-stop-notes
11685 Set the trace run's stop notes. The handling of the note is as for
11686 @code{tstop} arguments; the set command is convenient way to fix a
11687 stop note that is mistaken or incomplete.
11689 @item show trace-stop-notes
11690 @kindex show trace-stop-notes
11691 Show the trace run's stop notes.
11695 @node Tracepoint Restrictions
11696 @subsection Tracepoint Restrictions
11698 @cindex tracepoint restrictions
11699 There are a number of restrictions on the use of tracepoints. As
11700 described above, tracepoint data gathering occurs on the target
11701 without interaction from @value{GDBN}. Thus the full capabilities of
11702 the debugger are not available during data gathering, and then at data
11703 examination time, you will be limited by only having what was
11704 collected. The following items describe some common problems, but it
11705 is not exhaustive, and you may run into additional difficulties not
11711 Tracepoint expressions are intended to gather objects (lvalues). Thus
11712 the full flexibility of GDB's expression evaluator is not available.
11713 You cannot call functions, cast objects to aggregate types, access
11714 convenience variables or modify values (except by assignment to trace
11715 state variables). Some language features may implicitly call
11716 functions (for instance Objective-C fields with accessors), and therefore
11717 cannot be collected either.
11720 Collection of local variables, either individually or in bulk with
11721 @code{$locals} or @code{$args}, during @code{while-stepping} may
11722 behave erratically. The stepping action may enter a new scope (for
11723 instance by stepping into a function), or the location of the variable
11724 may change (for instance it is loaded into a register). The
11725 tracepoint data recorded uses the location information for the
11726 variables that is correct for the tracepoint location. When the
11727 tracepoint is created, it is not possible, in general, to determine
11728 where the steps of a @code{while-stepping} sequence will advance the
11729 program---particularly if a conditional branch is stepped.
11732 Collection of an incompletely-initialized or partially-destroyed object
11733 may result in something that @value{GDBN} cannot display, or displays
11734 in a misleading way.
11737 When @value{GDBN} displays a pointer to character it automatically
11738 dereferences the pointer to also display characters of the string
11739 being pointed to. However, collecting the pointer during tracing does
11740 not automatically collect the string. You need to explicitly
11741 dereference the pointer and provide size information if you want to
11742 collect not only the pointer, but the memory pointed to. For example,
11743 @code{*ptr@@50} can be used to collect the 50 element array pointed to
11747 It is not possible to collect a complete stack backtrace at a
11748 tracepoint. Instead, you may collect the registers and a few hundred
11749 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
11750 (adjust to use the name of the actual stack pointer register on your
11751 target architecture, and the amount of stack you wish to capture).
11752 Then the @code{backtrace} command will show a partial backtrace when
11753 using a trace frame. The number of stack frames that can be examined
11754 depends on the sizes of the frames in the collected stack. Note that
11755 if you ask for a block so large that it goes past the bottom of the
11756 stack, the target agent may report an error trying to read from an
11760 If you do not collect registers at a tracepoint, @value{GDBN} can
11761 infer that the value of @code{$pc} must be the same as the address of
11762 the tracepoint and use that when you are looking at a trace frame
11763 for that tracepoint. However, this cannot work if the tracepoint has
11764 multiple locations (for instance if it was set in a function that was
11765 inlined), or if it has a @code{while-stepping} loop. In those cases
11766 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
11771 @node Analyze Collected Data
11772 @section Using the Collected Data
11774 After the tracepoint experiment ends, you use @value{GDBN} commands
11775 for examining the trace data. The basic idea is that each tracepoint
11776 collects a trace @dfn{snapshot} every time it is hit and another
11777 snapshot every time it single-steps. All these snapshots are
11778 consecutively numbered from zero and go into a buffer, and you can
11779 examine them later. The way you examine them is to @dfn{focus} on a
11780 specific trace snapshot. When the remote stub is focused on a trace
11781 snapshot, it will respond to all @value{GDBN} requests for memory and
11782 registers by reading from the buffer which belongs to that snapshot,
11783 rather than from @emph{real} memory or registers of the program being
11784 debugged. This means that @strong{all} @value{GDBN} commands
11785 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
11786 behave as if we were currently debugging the program state as it was
11787 when the tracepoint occurred. Any requests for data that are not in
11788 the buffer will fail.
11791 * tfind:: How to select a trace snapshot
11792 * tdump:: How to display all data for a snapshot
11793 * save tracepoints:: How to save tracepoints for a future run
11797 @subsection @code{tfind @var{n}}
11800 @cindex select trace snapshot
11801 @cindex find trace snapshot
11802 The basic command for selecting a trace snapshot from the buffer is
11803 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
11804 counting from zero. If no argument @var{n} is given, the next
11805 snapshot is selected.
11807 Here are the various forms of using the @code{tfind} command.
11811 Find the first snapshot in the buffer. This is a synonym for
11812 @code{tfind 0} (since 0 is the number of the first snapshot).
11815 Stop debugging trace snapshots, resume @emph{live} debugging.
11818 Same as @samp{tfind none}.
11821 No argument means find the next trace snapshot.
11824 Find the previous trace snapshot before the current one. This permits
11825 retracing earlier steps.
11827 @item tfind tracepoint @var{num}
11828 Find the next snapshot associated with tracepoint @var{num}. Search
11829 proceeds forward from the last examined trace snapshot. If no
11830 argument @var{num} is given, it means find the next snapshot collected
11831 for the same tracepoint as the current snapshot.
11833 @item tfind pc @var{addr}
11834 Find the next snapshot associated with the value @var{addr} of the
11835 program counter. Search proceeds forward from the last examined trace
11836 snapshot. If no argument @var{addr} is given, it means find the next
11837 snapshot with the same value of PC as the current snapshot.
11839 @item tfind outside @var{addr1}, @var{addr2}
11840 Find the next snapshot whose PC is outside the given range of
11841 addresses (exclusive).
11843 @item tfind range @var{addr1}, @var{addr2}
11844 Find the next snapshot whose PC is between @var{addr1} and
11845 @var{addr2} (inclusive).
11847 @item tfind line @r{[}@var{file}:@r{]}@var{n}
11848 Find the next snapshot associated with the source line @var{n}. If
11849 the optional argument @var{file} is given, refer to line @var{n} in
11850 that source file. Search proceeds forward from the last examined
11851 trace snapshot. If no argument @var{n} is given, it means find the
11852 next line other than the one currently being examined; thus saying
11853 @code{tfind line} repeatedly can appear to have the same effect as
11854 stepping from line to line in a @emph{live} debugging session.
11857 The default arguments for the @code{tfind} commands are specifically
11858 designed to make it easy to scan through the trace buffer. For
11859 instance, @code{tfind} with no argument selects the next trace
11860 snapshot, and @code{tfind -} with no argument selects the previous
11861 trace snapshot. So, by giving one @code{tfind} command, and then
11862 simply hitting @key{RET} repeatedly you can examine all the trace
11863 snapshots in order. Or, by saying @code{tfind -} and then hitting
11864 @key{RET} repeatedly you can examine the snapshots in reverse order.
11865 The @code{tfind line} command with no argument selects the snapshot
11866 for the next source line executed. The @code{tfind pc} command with
11867 no argument selects the next snapshot with the same program counter
11868 (PC) as the current frame. The @code{tfind tracepoint} command with
11869 no argument selects the next trace snapshot collected by the same
11870 tracepoint as the current one.
11872 In addition to letting you scan through the trace buffer manually,
11873 these commands make it easy to construct @value{GDBN} scripts that
11874 scan through the trace buffer and print out whatever collected data
11875 you are interested in. Thus, if we want to examine the PC, FP, and SP
11876 registers from each trace frame in the buffer, we can say this:
11879 (@value{GDBP}) @b{tfind start}
11880 (@value{GDBP}) @b{while ($trace_frame != -1)}
11881 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
11882 $trace_frame, $pc, $sp, $fp
11886 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
11887 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
11888 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
11889 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
11890 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
11891 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
11892 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
11893 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
11894 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
11895 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
11896 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
11899 Or, if we want to examine the variable @code{X} at each source line in
11903 (@value{GDBP}) @b{tfind start}
11904 (@value{GDBP}) @b{while ($trace_frame != -1)}
11905 > printf "Frame %d, X == %d\n", $trace_frame, X
11915 @subsection @code{tdump}
11917 @cindex dump all data collected at tracepoint
11918 @cindex tracepoint data, display
11920 This command takes no arguments. It prints all the data collected at
11921 the current trace snapshot.
11924 (@value{GDBP}) @b{trace 444}
11925 (@value{GDBP}) @b{actions}
11926 Enter actions for tracepoint #2, one per line:
11927 > collect $regs, $locals, $args, gdb_long_test
11930 (@value{GDBP}) @b{tstart}
11932 (@value{GDBP}) @b{tfind line 444}
11933 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
11935 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
11937 (@value{GDBP}) @b{tdump}
11938 Data collected at tracepoint 2, trace frame 1:
11939 d0 0xc4aa0085 -995491707
11943 d4 0x71aea3d 119204413
11946 d7 0x380035 3670069
11947 a0 0x19e24a 1696330
11948 a1 0x3000668 50333288
11950 a3 0x322000 3284992
11951 a4 0x3000698 50333336
11952 a5 0x1ad3cc 1758156
11953 fp 0x30bf3c 0x30bf3c
11954 sp 0x30bf34 0x30bf34
11956 pc 0x20b2c8 0x20b2c8
11960 p = 0x20e5b4 "gdb-test"
11967 gdb_long_test = 17 '\021'
11972 @code{tdump} works by scanning the tracepoint's current collection
11973 actions and printing the value of each expression listed. So
11974 @code{tdump} can fail, if after a run, you change the tracepoint's
11975 actions to mention variables that were not collected during the run.
11977 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
11978 uses the collected value of @code{$pc} to distinguish between trace
11979 frames that were collected at the tracepoint hit, and frames that were
11980 collected while stepping. This allows it to correctly choose whether
11981 to display the basic list of collections, or the collections from the
11982 body of the while-stepping loop. However, if @code{$pc} was not collected,
11983 then @code{tdump} will always attempt to dump using the basic collection
11984 list, and may fail if a while-stepping frame does not include all the
11985 same data that is collected at the tracepoint hit.
11986 @c This is getting pretty arcane, example would be good.
11988 @node save tracepoints
11989 @subsection @code{save tracepoints @var{filename}}
11990 @kindex save tracepoints
11991 @kindex save-tracepoints
11992 @cindex save tracepoints for future sessions
11994 This command saves all current tracepoint definitions together with
11995 their actions and passcounts, into a file @file{@var{filename}}
11996 suitable for use in a later debugging session. To read the saved
11997 tracepoint definitions, use the @code{source} command (@pxref{Command
11998 Files}). The @w{@code{save-tracepoints}} command is a deprecated
11999 alias for @w{@code{save tracepoints}}
12001 @node Tracepoint Variables
12002 @section Convenience Variables for Tracepoints
12003 @cindex tracepoint variables
12004 @cindex convenience variables for tracepoints
12007 @vindex $trace_frame
12008 @item (int) $trace_frame
12009 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
12010 snapshot is selected.
12012 @vindex $tracepoint
12013 @item (int) $tracepoint
12014 The tracepoint for the current trace snapshot.
12016 @vindex $trace_line
12017 @item (int) $trace_line
12018 The line number for the current trace snapshot.
12020 @vindex $trace_file
12021 @item (char []) $trace_file
12022 The source file for the current trace snapshot.
12024 @vindex $trace_func
12025 @item (char []) $trace_func
12026 The name of the function containing @code{$tracepoint}.
12029 Note: @code{$trace_file} is not suitable for use in @code{printf},
12030 use @code{output} instead.
12032 Here's a simple example of using these convenience variables for
12033 stepping through all the trace snapshots and printing some of their
12034 data. Note that these are not the same as trace state variables,
12035 which are managed by the target.
12038 (@value{GDBP}) @b{tfind start}
12040 (@value{GDBP}) @b{while $trace_frame != -1}
12041 > output $trace_file
12042 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
12048 @section Using Trace Files
12049 @cindex trace files
12051 In some situations, the target running a trace experiment may no
12052 longer be available; perhaps it crashed, or the hardware was needed
12053 for a different activity. To handle these cases, you can arrange to
12054 dump the trace data into a file, and later use that file as a source
12055 of trace data, via the @code{target tfile} command.
12060 @item tsave [ -r ] @var{filename}
12061 Save the trace data to @var{filename}. By default, this command
12062 assumes that @var{filename} refers to the host filesystem, so if
12063 necessary @value{GDBN} will copy raw trace data up from the target and
12064 then save it. If the target supports it, you can also supply the
12065 optional argument @code{-r} (``remote'') to direct the target to save
12066 the data directly into @var{filename} in its own filesystem, which may be
12067 more efficient if the trace buffer is very large. (Note, however, that
12068 @code{target tfile} can only read from files accessible to the host.)
12070 @kindex target tfile
12072 @item target tfile @var{filename}
12073 Use the file named @var{filename} as a source of trace data. Commands
12074 that examine data work as they do with a live target, but it is not
12075 possible to run any new trace experiments. @code{tstatus} will report
12076 the state of the trace run at the moment the data was saved, as well
12077 as the current trace frame you are examining. @var{filename} must be
12078 on a filesystem accessible to the host.
12083 @chapter Debugging Programs That Use Overlays
12086 If your program is too large to fit completely in your target system's
12087 memory, you can sometimes use @dfn{overlays} to work around this
12088 problem. @value{GDBN} provides some support for debugging programs that
12092 * How Overlays Work:: A general explanation of overlays.
12093 * Overlay Commands:: Managing overlays in @value{GDBN}.
12094 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
12095 mapped by asking the inferior.
12096 * Overlay Sample Program:: A sample program using overlays.
12099 @node How Overlays Work
12100 @section How Overlays Work
12101 @cindex mapped overlays
12102 @cindex unmapped overlays
12103 @cindex load address, overlay's
12104 @cindex mapped address
12105 @cindex overlay area
12107 Suppose you have a computer whose instruction address space is only 64
12108 kilobytes long, but which has much more memory which can be accessed by
12109 other means: special instructions, segment registers, or memory
12110 management hardware, for example. Suppose further that you want to
12111 adapt a program which is larger than 64 kilobytes to run on this system.
12113 One solution is to identify modules of your program which are relatively
12114 independent, and need not call each other directly; call these modules
12115 @dfn{overlays}. Separate the overlays from the main program, and place
12116 their machine code in the larger memory. Place your main program in
12117 instruction memory, but leave at least enough space there to hold the
12118 largest overlay as well.
12120 Now, to call a function located in an overlay, you must first copy that
12121 overlay's machine code from the large memory into the space set aside
12122 for it in the instruction memory, and then jump to its entry point
12125 @c NB: In the below the mapped area's size is greater or equal to the
12126 @c size of all overlays. This is intentional to remind the developer
12127 @c that overlays don't necessarily need to be the same size.
12131 Data Instruction Larger
12132 Address Space Address Space Address Space
12133 +-----------+ +-----------+ +-----------+
12135 +-----------+ +-----------+ +-----------+<-- overlay 1
12136 | program | | main | .----| overlay 1 | load address
12137 | variables | | program | | +-----------+
12138 | and heap | | | | | |
12139 +-----------+ | | | +-----------+<-- overlay 2
12140 | | +-----------+ | | | load address
12141 +-----------+ | | | .-| overlay 2 |
12143 mapped --->+-----------+ | | +-----------+
12144 address | | | | | |
12145 | overlay | <-' | | |
12146 | area | <---' +-----------+<-- overlay 3
12147 | | <---. | | load address
12148 +-----------+ `--| overlay 3 |
12155 @anchor{A code overlay}A code overlay
12159 The diagram (@pxref{A code overlay}) shows a system with separate data
12160 and instruction address spaces. To map an overlay, the program copies
12161 its code from the larger address space to the instruction address space.
12162 Since the overlays shown here all use the same mapped address, only one
12163 may be mapped at a time. For a system with a single address space for
12164 data and instructions, the diagram would be similar, except that the
12165 program variables and heap would share an address space with the main
12166 program and the overlay area.
12168 An overlay loaded into instruction memory and ready for use is called a
12169 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
12170 instruction memory. An overlay not present (or only partially present)
12171 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
12172 is its address in the larger memory. The mapped address is also called
12173 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
12174 called the @dfn{load memory address}, or @dfn{LMA}.
12176 Unfortunately, overlays are not a completely transparent way to adapt a
12177 program to limited instruction memory. They introduce a new set of
12178 global constraints you must keep in mind as you design your program:
12183 Before calling or returning to a function in an overlay, your program
12184 must make sure that overlay is actually mapped. Otherwise, the call or
12185 return will transfer control to the right address, but in the wrong
12186 overlay, and your program will probably crash.
12189 If the process of mapping an overlay is expensive on your system, you
12190 will need to choose your overlays carefully to minimize their effect on
12191 your program's performance.
12194 The executable file you load onto your system must contain each
12195 overlay's instructions, appearing at the overlay's load address, not its
12196 mapped address. However, each overlay's instructions must be relocated
12197 and its symbols defined as if the overlay were at its mapped address.
12198 You can use GNU linker scripts to specify different load and relocation
12199 addresses for pieces of your program; see @ref{Overlay Description,,,
12200 ld.info, Using ld: the GNU linker}.
12203 The procedure for loading executable files onto your system must be able
12204 to load their contents into the larger address space as well as the
12205 instruction and data spaces.
12209 The overlay system described above is rather simple, and could be
12210 improved in many ways:
12215 If your system has suitable bank switch registers or memory management
12216 hardware, you could use those facilities to make an overlay's load area
12217 contents simply appear at their mapped address in instruction space.
12218 This would probably be faster than copying the overlay to its mapped
12219 area in the usual way.
12222 If your overlays are small enough, you could set aside more than one
12223 overlay area, and have more than one overlay mapped at a time.
12226 You can use overlays to manage data, as well as instructions. In
12227 general, data overlays are even less transparent to your design than
12228 code overlays: whereas code overlays only require care when you call or
12229 return to functions, data overlays require care every time you access
12230 the data. Also, if you change the contents of a data overlay, you
12231 must copy its contents back out to its load address before you can copy a
12232 different data overlay into the same mapped area.
12237 @node Overlay Commands
12238 @section Overlay Commands
12240 To use @value{GDBN}'s overlay support, each overlay in your program must
12241 correspond to a separate section of the executable file. The section's
12242 virtual memory address and load memory address must be the overlay's
12243 mapped and load addresses. Identifying overlays with sections allows
12244 @value{GDBN} to determine the appropriate address of a function or
12245 variable, depending on whether the overlay is mapped or not.
12247 @value{GDBN}'s overlay commands all start with the word @code{overlay};
12248 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
12253 Disable @value{GDBN}'s overlay support. When overlay support is
12254 disabled, @value{GDBN} assumes that all functions and variables are
12255 always present at their mapped addresses. By default, @value{GDBN}'s
12256 overlay support is disabled.
12258 @item overlay manual
12259 @cindex manual overlay debugging
12260 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
12261 relies on you to tell it which overlays are mapped, and which are not,
12262 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
12263 commands described below.
12265 @item overlay map-overlay @var{overlay}
12266 @itemx overlay map @var{overlay}
12267 @cindex map an overlay
12268 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
12269 be the name of the object file section containing the overlay. When an
12270 overlay is mapped, @value{GDBN} assumes it can find the overlay's
12271 functions and variables at their mapped addresses. @value{GDBN} assumes
12272 that any other overlays whose mapped ranges overlap that of
12273 @var{overlay} are now unmapped.
12275 @item overlay unmap-overlay @var{overlay}
12276 @itemx overlay unmap @var{overlay}
12277 @cindex unmap an overlay
12278 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
12279 must be the name of the object file section containing the overlay.
12280 When an overlay is unmapped, @value{GDBN} assumes it can find the
12281 overlay's functions and variables at their load addresses.
12284 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
12285 consults a data structure the overlay manager maintains in the inferior
12286 to see which overlays are mapped. For details, see @ref{Automatic
12287 Overlay Debugging}.
12289 @item overlay load-target
12290 @itemx overlay load
12291 @cindex reloading the overlay table
12292 Re-read the overlay table from the inferior. Normally, @value{GDBN}
12293 re-reads the table @value{GDBN} automatically each time the inferior
12294 stops, so this command should only be necessary if you have changed the
12295 overlay mapping yourself using @value{GDBN}. This command is only
12296 useful when using automatic overlay debugging.
12298 @item overlay list-overlays
12299 @itemx overlay list
12300 @cindex listing mapped overlays
12301 Display a list of the overlays currently mapped, along with their mapped
12302 addresses, load addresses, and sizes.
12306 Normally, when @value{GDBN} prints a code address, it includes the name
12307 of the function the address falls in:
12310 (@value{GDBP}) print main
12311 $3 = @{int ()@} 0x11a0 <main>
12314 When overlay debugging is enabled, @value{GDBN} recognizes code in
12315 unmapped overlays, and prints the names of unmapped functions with
12316 asterisks around them. For example, if @code{foo} is a function in an
12317 unmapped overlay, @value{GDBN} prints it this way:
12320 (@value{GDBP}) overlay list
12321 No sections are mapped.
12322 (@value{GDBP}) print foo
12323 $5 = @{int (int)@} 0x100000 <*foo*>
12326 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
12330 (@value{GDBP}) overlay list
12331 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
12332 mapped at 0x1016 - 0x104a
12333 (@value{GDBP}) print foo
12334 $6 = @{int (int)@} 0x1016 <foo>
12337 When overlay debugging is enabled, @value{GDBN} can find the correct
12338 address for functions and variables in an overlay, whether or not the
12339 overlay is mapped. This allows most @value{GDBN} commands, like
12340 @code{break} and @code{disassemble}, to work normally, even on unmapped
12341 code. However, @value{GDBN}'s breakpoint support has some limitations:
12345 @cindex breakpoints in overlays
12346 @cindex overlays, setting breakpoints in
12347 You can set breakpoints in functions in unmapped overlays, as long as
12348 @value{GDBN} can write to the overlay at its load address.
12350 @value{GDBN} can not set hardware or simulator-based breakpoints in
12351 unmapped overlays. However, if you set a breakpoint at the end of your
12352 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
12353 you are using manual overlay management), @value{GDBN} will re-set its
12354 breakpoints properly.
12358 @node Automatic Overlay Debugging
12359 @section Automatic Overlay Debugging
12360 @cindex automatic overlay debugging
12362 @value{GDBN} can automatically track which overlays are mapped and which
12363 are not, given some simple co-operation from the overlay manager in the
12364 inferior. If you enable automatic overlay debugging with the
12365 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
12366 looks in the inferior's memory for certain variables describing the
12367 current state of the overlays.
12369 Here are the variables your overlay manager must define to support
12370 @value{GDBN}'s automatic overlay debugging:
12374 @item @code{_ovly_table}:
12375 This variable must be an array of the following structures:
12380 /* The overlay's mapped address. */
12383 /* The size of the overlay, in bytes. */
12384 unsigned long size;
12386 /* The overlay's load address. */
12389 /* Non-zero if the overlay is currently mapped;
12391 unsigned long mapped;
12395 @item @code{_novlys}:
12396 This variable must be a four-byte signed integer, holding the total
12397 number of elements in @code{_ovly_table}.
12401 To decide whether a particular overlay is mapped or not, @value{GDBN}
12402 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
12403 @code{lma} members equal the VMA and LMA of the overlay's section in the
12404 executable file. When @value{GDBN} finds a matching entry, it consults
12405 the entry's @code{mapped} member to determine whether the overlay is
12408 In addition, your overlay manager may define a function called
12409 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
12410 will silently set a breakpoint there. If the overlay manager then
12411 calls this function whenever it has changed the overlay table, this
12412 will enable @value{GDBN} to accurately keep track of which overlays
12413 are in program memory, and update any breakpoints that may be set
12414 in overlays. This will allow breakpoints to work even if the
12415 overlays are kept in ROM or other non-writable memory while they
12416 are not being executed.
12418 @node Overlay Sample Program
12419 @section Overlay Sample Program
12420 @cindex overlay example program
12422 When linking a program which uses overlays, you must place the overlays
12423 at their load addresses, while relocating them to run at their mapped
12424 addresses. To do this, you must write a linker script (@pxref{Overlay
12425 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
12426 since linker scripts are specific to a particular host system, target
12427 architecture, and target memory layout, this manual cannot provide
12428 portable sample code demonstrating @value{GDBN}'s overlay support.
12430 However, the @value{GDBN} source distribution does contain an overlaid
12431 program, with linker scripts for a few systems, as part of its test
12432 suite. The program consists of the following files from
12433 @file{gdb/testsuite/gdb.base}:
12437 The main program file.
12439 A simple overlay manager, used by @file{overlays.c}.
12444 Overlay modules, loaded and used by @file{overlays.c}.
12447 Linker scripts for linking the test program on the @code{d10v-elf}
12448 and @code{m32r-elf} targets.
12451 You can build the test program using the @code{d10v-elf} GCC
12452 cross-compiler like this:
12455 $ d10v-elf-gcc -g -c overlays.c
12456 $ d10v-elf-gcc -g -c ovlymgr.c
12457 $ d10v-elf-gcc -g -c foo.c
12458 $ d10v-elf-gcc -g -c bar.c
12459 $ d10v-elf-gcc -g -c baz.c
12460 $ d10v-elf-gcc -g -c grbx.c
12461 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
12462 baz.o grbx.o -Wl,-Td10v.ld -o overlays
12465 The build process is identical for any other architecture, except that
12466 you must substitute the appropriate compiler and linker script for the
12467 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
12471 @chapter Using @value{GDBN} with Different Languages
12474 Although programming languages generally have common aspects, they are
12475 rarely expressed in the same manner. For instance, in ANSI C,
12476 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
12477 Modula-2, it is accomplished by @code{p^}. Values can also be
12478 represented (and displayed) differently. Hex numbers in C appear as
12479 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
12481 @cindex working language
12482 Language-specific information is built into @value{GDBN} for some languages,
12483 allowing you to express operations like the above in your program's
12484 native language, and allowing @value{GDBN} to output values in a manner
12485 consistent with the syntax of your program's native language. The
12486 language you use to build expressions is called the @dfn{working
12490 * Setting:: Switching between source languages
12491 * Show:: Displaying the language
12492 * Checks:: Type and range checks
12493 * Supported Languages:: Supported languages
12494 * Unsupported Languages:: Unsupported languages
12498 @section Switching Between Source Languages
12500 There are two ways to control the working language---either have @value{GDBN}
12501 set it automatically, or select it manually yourself. You can use the
12502 @code{set language} command for either purpose. On startup, @value{GDBN}
12503 defaults to setting the language automatically. The working language is
12504 used to determine how expressions you type are interpreted, how values
12507 In addition to the working language, every source file that
12508 @value{GDBN} knows about has its own working language. For some object
12509 file formats, the compiler might indicate which language a particular
12510 source file is in. However, most of the time @value{GDBN} infers the
12511 language from the name of the file. The language of a source file
12512 controls whether C@t{++} names are demangled---this way @code{backtrace} can
12513 show each frame appropriately for its own language. There is no way to
12514 set the language of a source file from within @value{GDBN}, but you can
12515 set the language associated with a filename extension. @xref{Show, ,
12516 Displaying the Language}.
12518 This is most commonly a problem when you use a program, such
12519 as @code{cfront} or @code{f2c}, that generates C but is written in
12520 another language. In that case, make the
12521 program use @code{#line} directives in its C output; that way
12522 @value{GDBN} will know the correct language of the source code of the original
12523 program, and will display that source code, not the generated C code.
12526 * Filenames:: Filename extensions and languages.
12527 * Manually:: Setting the working language manually
12528 * Automatically:: Having @value{GDBN} infer the source language
12532 @subsection List of Filename Extensions and Languages
12534 If a source file name ends in one of the following extensions, then
12535 @value{GDBN} infers that its language is the one indicated.
12553 C@t{++} source file
12559 Objective-C source file
12563 Fortran source file
12566 Modula-2 source file
12570 Assembler source file. This actually behaves almost like C, but
12571 @value{GDBN} does not skip over function prologues when stepping.
12574 In addition, you may set the language associated with a filename
12575 extension. @xref{Show, , Displaying the Language}.
12578 @subsection Setting the Working Language
12580 If you allow @value{GDBN} to set the language automatically,
12581 expressions are interpreted the same way in your debugging session and
12584 @kindex set language
12585 If you wish, you may set the language manually. To do this, issue the
12586 command @samp{set language @var{lang}}, where @var{lang} is the name of
12587 a language, such as
12588 @code{c} or @code{modula-2}.
12589 For a list of the supported languages, type @samp{set language}.
12591 Setting the language manually prevents @value{GDBN} from updating the working
12592 language automatically. This can lead to confusion if you try
12593 to debug a program when the working language is not the same as the
12594 source language, when an expression is acceptable to both
12595 languages---but means different things. For instance, if the current
12596 source file were written in C, and @value{GDBN} was parsing Modula-2, a
12604 might not have the effect you intended. In C, this means to add
12605 @code{b} and @code{c} and place the result in @code{a}. The result
12606 printed would be the value of @code{a}. In Modula-2, this means to compare
12607 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
12609 @node Automatically
12610 @subsection Having @value{GDBN} Infer the Source Language
12612 To have @value{GDBN} set the working language automatically, use
12613 @samp{set language local} or @samp{set language auto}. @value{GDBN}
12614 then infers the working language. That is, when your program stops in a
12615 frame (usually by encountering a breakpoint), @value{GDBN} sets the
12616 working language to the language recorded for the function in that
12617 frame. If the language for a frame is unknown (that is, if the function
12618 or block corresponding to the frame was defined in a source file that
12619 does not have a recognized extension), the current working language is
12620 not changed, and @value{GDBN} issues a warning.
12622 This may not seem necessary for most programs, which are written
12623 entirely in one source language. However, program modules and libraries
12624 written in one source language can be used by a main program written in
12625 a different source language. Using @samp{set language auto} in this
12626 case frees you from having to set the working language manually.
12629 @section Displaying the Language
12631 The following commands help you find out which language is the
12632 working language, and also what language source files were written in.
12635 @item show language
12636 @kindex show language
12637 Display the current working language. This is the
12638 language you can use with commands such as @code{print} to
12639 build and compute expressions that may involve variables in your program.
12642 @kindex info frame@r{, show the source language}
12643 Display the source language for this frame. This language becomes the
12644 working language if you use an identifier from this frame.
12645 @xref{Frame Info, ,Information about a Frame}, to identify the other
12646 information listed here.
12649 @kindex info source@r{, show the source language}
12650 Display the source language of this source file.
12651 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
12652 information listed here.
12655 In unusual circumstances, you may have source files with extensions
12656 not in the standard list. You can then set the extension associated
12657 with a language explicitly:
12660 @item set extension-language @var{ext} @var{language}
12661 @kindex set extension-language
12662 Tell @value{GDBN} that source files with extension @var{ext} are to be
12663 assumed as written in the source language @var{language}.
12665 @item info extensions
12666 @kindex info extensions
12667 List all the filename extensions and the associated languages.
12671 @section Type and Range Checking
12674 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
12675 checking are included, but they do not yet have any effect. This
12676 section documents the intended facilities.
12678 @c FIXME remove warning when type/range code added
12680 Some languages are designed to guard you against making seemingly common
12681 errors through a series of compile- and run-time checks. These include
12682 checking the type of arguments to functions and operators, and making
12683 sure mathematical overflows are caught at run time. Checks such as
12684 these help to ensure a program's correctness once it has been compiled
12685 by eliminating type mismatches, and providing active checks for range
12686 errors when your program is running.
12688 @value{GDBN} can check for conditions like the above if you wish.
12689 Although @value{GDBN} does not check the statements in your program,
12690 it can check expressions entered directly into @value{GDBN} for
12691 evaluation via the @code{print} command, for example. As with the
12692 working language, @value{GDBN} can also decide whether or not to check
12693 automatically based on your program's source language.
12694 @xref{Supported Languages, ,Supported Languages}, for the default
12695 settings of supported languages.
12698 * Type Checking:: An overview of type checking
12699 * Range Checking:: An overview of range checking
12702 @cindex type checking
12703 @cindex checks, type
12704 @node Type Checking
12705 @subsection An Overview of Type Checking
12707 Some languages, such as Modula-2, are strongly typed, meaning that the
12708 arguments to operators and functions have to be of the correct type,
12709 otherwise an error occurs. These checks prevent type mismatch
12710 errors from ever causing any run-time problems. For example,
12718 The second example fails because the @code{CARDINAL} 1 is not
12719 type-compatible with the @code{REAL} 2.3.
12721 For the expressions you use in @value{GDBN} commands, you can tell the
12722 @value{GDBN} type checker to skip checking;
12723 to treat any mismatches as errors and abandon the expression;
12724 or to only issue warnings when type mismatches occur,
12725 but evaluate the expression anyway. When you choose the last of
12726 these, @value{GDBN} evaluates expressions like the second example above, but
12727 also issues a warning.
12729 Even if you turn type checking off, there may be other reasons
12730 related to type that prevent @value{GDBN} from evaluating an expression.
12731 For instance, @value{GDBN} does not know how to add an @code{int} and
12732 a @code{struct foo}. These particular type errors have nothing to do
12733 with the language in use, and usually arise from expressions, such as
12734 the one described above, which make little sense to evaluate anyway.
12736 Each language defines to what degree it is strict about type. For
12737 instance, both Modula-2 and C require the arguments to arithmetical
12738 operators to be numbers. In C, enumerated types and pointers can be
12739 represented as numbers, so that they are valid arguments to mathematical
12740 operators. @xref{Supported Languages, ,Supported Languages}, for further
12741 details on specific languages.
12743 @value{GDBN} provides some additional commands for controlling the type checker:
12745 @kindex set check type
12746 @kindex show check type
12748 @item set check type auto
12749 Set type checking on or off based on the current working language.
12750 @xref{Supported Languages, ,Supported Languages}, for the default settings for
12753 @item set check type on
12754 @itemx set check type off
12755 Set type checking on or off, overriding the default setting for the
12756 current working language. Issue a warning if the setting does not
12757 match the language default. If any type mismatches occur in
12758 evaluating an expression while type checking is on, @value{GDBN} prints a
12759 message and aborts evaluation of the expression.
12761 @item set check type warn
12762 Cause the type checker to issue warnings, but to always attempt to
12763 evaluate the expression. Evaluating the expression may still
12764 be impossible for other reasons. For example, @value{GDBN} cannot add
12765 numbers and structures.
12768 Show the current setting of the type checker, and whether or not @value{GDBN}
12769 is setting it automatically.
12772 @cindex range checking
12773 @cindex checks, range
12774 @node Range Checking
12775 @subsection An Overview of Range Checking
12777 In some languages (such as Modula-2), it is an error to exceed the
12778 bounds of a type; this is enforced with run-time checks. Such range
12779 checking is meant to ensure program correctness by making sure
12780 computations do not overflow, or indices on an array element access do
12781 not exceed the bounds of the array.
12783 For expressions you use in @value{GDBN} commands, you can tell
12784 @value{GDBN} to treat range errors in one of three ways: ignore them,
12785 always treat them as errors and abandon the expression, or issue
12786 warnings but evaluate the expression anyway.
12788 A range error can result from numerical overflow, from exceeding an
12789 array index bound, or when you type a constant that is not a member
12790 of any type. Some languages, however, do not treat overflows as an
12791 error. In many implementations of C, mathematical overflow causes the
12792 result to ``wrap around'' to lower values---for example, if @var{m} is
12793 the largest integer value, and @var{s} is the smallest, then
12796 @var{m} + 1 @result{} @var{s}
12799 This, too, is specific to individual languages, and in some cases
12800 specific to individual compilers or machines. @xref{Supported Languages, ,
12801 Supported Languages}, for further details on specific languages.
12803 @value{GDBN} provides some additional commands for controlling the range checker:
12805 @kindex set check range
12806 @kindex show check range
12808 @item set check range auto
12809 Set range checking on or off based on the current working language.
12810 @xref{Supported Languages, ,Supported Languages}, for the default settings for
12813 @item set check range on
12814 @itemx set check range off
12815 Set range checking on or off, overriding the default setting for the
12816 current working language. A warning is issued if the setting does not
12817 match the language default. If a range error occurs and range checking is on,
12818 then a message is printed and evaluation of the expression is aborted.
12820 @item set check range warn
12821 Output messages when the @value{GDBN} range checker detects a range error,
12822 but attempt to evaluate the expression anyway. Evaluating the
12823 expression may still be impossible for other reasons, such as accessing
12824 memory that the process does not own (a typical example from many Unix
12828 Show the current setting of the range checker, and whether or not it is
12829 being set automatically by @value{GDBN}.
12832 @node Supported Languages
12833 @section Supported Languages
12835 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
12836 OpenCL C, Pascal, assembly, Modula-2, and Ada.
12837 @c This is false ...
12838 Some @value{GDBN} features may be used in expressions regardless of the
12839 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
12840 and the @samp{@{type@}addr} construct (@pxref{Expressions,
12841 ,Expressions}) can be used with the constructs of any supported
12844 The following sections detail to what degree each source language is
12845 supported by @value{GDBN}. These sections are not meant to be language
12846 tutorials or references, but serve only as a reference guide to what the
12847 @value{GDBN} expression parser accepts, and what input and output
12848 formats should look like for different languages. There are many good
12849 books written on each of these languages; please look to these for a
12850 language reference or tutorial.
12853 * C:: C and C@t{++}
12856 * Objective-C:: Objective-C
12857 * OpenCL C:: OpenCL C
12858 * Fortran:: Fortran
12860 * Modula-2:: Modula-2
12865 @subsection C and C@t{++}
12867 @cindex C and C@t{++}
12868 @cindex expressions in C or C@t{++}
12870 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
12871 to both languages. Whenever this is the case, we discuss those languages
12875 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
12876 @cindex @sc{gnu} C@t{++}
12877 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
12878 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
12879 effectively, you must compile your C@t{++} programs with a supported
12880 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
12881 compiler (@code{aCC}).
12884 * C Operators:: C and C@t{++} operators
12885 * C Constants:: C and C@t{++} constants
12886 * C Plus Plus Expressions:: C@t{++} expressions
12887 * C Defaults:: Default settings for C and C@t{++}
12888 * C Checks:: C and C@t{++} type and range checks
12889 * Debugging C:: @value{GDBN} and C
12890 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
12891 * Decimal Floating Point:: Numbers in Decimal Floating Point format
12895 @subsubsection C and C@t{++} Operators
12897 @cindex C and C@t{++} operators
12899 Operators must be defined on values of specific types. For instance,
12900 @code{+} is defined on numbers, but not on structures. Operators are
12901 often defined on groups of types.
12903 For the purposes of C and C@t{++}, the following definitions hold:
12908 @emph{Integral types} include @code{int} with any of its storage-class
12909 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
12912 @emph{Floating-point types} include @code{float}, @code{double}, and
12913 @code{long double} (if supported by the target platform).
12916 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
12919 @emph{Scalar types} include all of the above.
12924 The following operators are supported. They are listed here
12925 in order of increasing precedence:
12929 The comma or sequencing operator. Expressions in a comma-separated list
12930 are evaluated from left to right, with the result of the entire
12931 expression being the last expression evaluated.
12934 Assignment. The value of an assignment expression is the value
12935 assigned. Defined on scalar types.
12938 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
12939 and translated to @w{@code{@var{a} = @var{a op b}}}.
12940 @w{@code{@var{op}=}} and @code{=} have the same precedence.
12941 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
12942 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
12945 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
12946 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
12950 Logical @sc{or}. Defined on integral types.
12953 Logical @sc{and}. Defined on integral types.
12956 Bitwise @sc{or}. Defined on integral types.
12959 Bitwise exclusive-@sc{or}. Defined on integral types.
12962 Bitwise @sc{and}. Defined on integral types.
12965 Equality and inequality. Defined on scalar types. The value of these
12966 expressions is 0 for false and non-zero for true.
12968 @item <@r{, }>@r{, }<=@r{, }>=
12969 Less than, greater than, less than or equal, greater than or equal.
12970 Defined on scalar types. The value of these expressions is 0 for false
12971 and non-zero for true.
12974 left shift, and right shift. Defined on integral types.
12977 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
12980 Addition and subtraction. Defined on integral types, floating-point types and
12983 @item *@r{, }/@r{, }%
12984 Multiplication, division, and modulus. Multiplication and division are
12985 defined on integral and floating-point types. Modulus is defined on
12989 Increment and decrement. When appearing before a variable, the
12990 operation is performed before the variable is used in an expression;
12991 when appearing after it, the variable's value is used before the
12992 operation takes place.
12995 Pointer dereferencing. Defined on pointer types. Same precedence as
12999 Address operator. Defined on variables. Same precedence as @code{++}.
13001 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
13002 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
13003 to examine the address
13004 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
13008 Negative. Defined on integral and floating-point types. Same
13009 precedence as @code{++}.
13012 Logical negation. Defined on integral types. Same precedence as
13016 Bitwise complement operator. Defined on integral types. Same precedence as
13021 Structure member, and pointer-to-structure member. For convenience,
13022 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
13023 pointer based on the stored type information.
13024 Defined on @code{struct} and @code{union} data.
13027 Dereferences of pointers to members.
13030 Array indexing. @code{@var{a}[@var{i}]} is defined as
13031 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
13034 Function parameter list. Same precedence as @code{->}.
13037 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
13038 and @code{class} types.
13041 Doubled colons also represent the @value{GDBN} scope operator
13042 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
13046 If an operator is redefined in the user code, @value{GDBN} usually
13047 attempts to invoke the redefined version instead of using the operator's
13048 predefined meaning.
13051 @subsubsection C and C@t{++} Constants
13053 @cindex C and C@t{++} constants
13055 @value{GDBN} allows you to express the constants of C and C@t{++} in the
13060 Integer constants are a sequence of digits. Octal constants are
13061 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
13062 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
13063 @samp{l}, specifying that the constant should be treated as a
13067 Floating point constants are a sequence of digits, followed by a decimal
13068 point, followed by a sequence of digits, and optionally followed by an
13069 exponent. An exponent is of the form:
13070 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
13071 sequence of digits. The @samp{+} is optional for positive exponents.
13072 A floating-point constant may also end with a letter @samp{f} or
13073 @samp{F}, specifying that the constant should be treated as being of
13074 the @code{float} (as opposed to the default @code{double}) type; or with
13075 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
13079 Enumerated constants consist of enumerated identifiers, or their
13080 integral equivalents.
13083 Character constants are a single character surrounded by single quotes
13084 (@code{'}), or a number---the ordinal value of the corresponding character
13085 (usually its @sc{ascii} value). Within quotes, the single character may
13086 be represented by a letter or by @dfn{escape sequences}, which are of
13087 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
13088 of the character's ordinal value; or of the form @samp{\@var{x}}, where
13089 @samp{@var{x}} is a predefined special character---for example,
13090 @samp{\n} for newline.
13092 Wide character constants can be written by prefixing a character
13093 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
13094 form of @samp{x}. The target wide character set is used when
13095 computing the value of this constant (@pxref{Character Sets}).
13098 String constants are a sequence of character constants surrounded by
13099 double quotes (@code{"}). Any valid character constant (as described
13100 above) may appear. Double quotes within the string must be preceded by
13101 a backslash, so for instance @samp{"a\"b'c"} is a string of five
13104 Wide string constants can be written by prefixing a string constant
13105 with @samp{L}, as in C. The target wide character set is used when
13106 computing the value of this constant (@pxref{Character Sets}).
13109 Pointer constants are an integral value. You can also write pointers
13110 to constants using the C operator @samp{&}.
13113 Array constants are comma-separated lists surrounded by braces @samp{@{}
13114 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
13115 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
13116 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
13119 @node C Plus Plus Expressions
13120 @subsubsection C@t{++} Expressions
13122 @cindex expressions in C@t{++}
13123 @value{GDBN} expression handling can interpret most C@t{++} expressions.
13125 @cindex debugging C@t{++} programs
13126 @cindex C@t{++} compilers
13127 @cindex debug formats and C@t{++}
13128 @cindex @value{NGCC} and C@t{++}
13130 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
13131 the proper compiler and the proper debug format. Currently,
13132 @value{GDBN} works best when debugging C@t{++} code that is compiled
13133 with the most recent version of @value{NGCC} possible. The DWARF
13134 debugging format is preferred; @value{NGCC} defaults to this on most
13135 popular platforms. Other compilers and/or debug formats are likely to
13136 work badly or not at all when using @value{GDBN} to debug C@t{++}
13137 code. @xref{Compilation}.
13142 @cindex member functions
13144 Member function calls are allowed; you can use expressions like
13147 count = aml->GetOriginal(x, y)
13150 @vindex this@r{, inside C@t{++} member functions}
13151 @cindex namespace in C@t{++}
13153 While a member function is active (in the selected stack frame), your
13154 expressions have the same namespace available as the member function;
13155 that is, @value{GDBN} allows implicit references to the class instance
13156 pointer @code{this} following the same rules as C@t{++}. @code{using}
13157 declarations in the current scope are also respected by @value{GDBN}.
13159 @cindex call overloaded functions
13160 @cindex overloaded functions, calling
13161 @cindex type conversions in C@t{++}
13163 You can call overloaded functions; @value{GDBN} resolves the function
13164 call to the right definition, with some restrictions. @value{GDBN} does not
13165 perform overload resolution involving user-defined type conversions,
13166 calls to constructors, or instantiations of templates that do not exist
13167 in the program. It also cannot handle ellipsis argument lists or
13170 It does perform integral conversions and promotions, floating-point
13171 promotions, arithmetic conversions, pointer conversions, conversions of
13172 class objects to base classes, and standard conversions such as those of
13173 functions or arrays to pointers; it requires an exact match on the
13174 number of function arguments.
13176 Overload resolution is always performed, unless you have specified
13177 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
13178 ,@value{GDBN} Features for C@t{++}}.
13180 You must specify @code{set overload-resolution off} in order to use an
13181 explicit function signature to call an overloaded function, as in
13183 p 'foo(char,int)'('x', 13)
13186 The @value{GDBN} command-completion facility can simplify this;
13187 see @ref{Completion, ,Command Completion}.
13189 @cindex reference declarations
13191 @value{GDBN} understands variables declared as C@t{++} references; you can use
13192 them in expressions just as you do in C@t{++} source---they are automatically
13195 In the parameter list shown when @value{GDBN} displays a frame, the values of
13196 reference variables are not displayed (unlike other variables); this
13197 avoids clutter, since references are often used for large structures.
13198 The @emph{address} of a reference variable is always shown, unless
13199 you have specified @samp{set print address off}.
13202 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
13203 expressions can use it just as expressions in your program do. Since
13204 one scope may be defined in another, you can use @code{::} repeatedly if
13205 necessary, for example in an expression like
13206 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
13207 resolving name scope by reference to source files, in both C and C@t{++}
13208 debugging (@pxref{Variables, ,Program Variables}).
13211 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
13216 @subsubsection C and C@t{++} Defaults
13218 @cindex C and C@t{++} defaults
13220 If you allow @value{GDBN} to set type and range checking automatically, they
13221 both default to @code{off} whenever the working language changes to
13222 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
13223 selects the working language.
13225 If you allow @value{GDBN} to set the language automatically, it
13226 recognizes source files whose names end with @file{.c}, @file{.C}, or
13227 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
13228 these files, it sets the working language to C or C@t{++}.
13229 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
13230 for further details.
13232 @c Type checking is (a) primarily motivated by Modula-2, and (b)
13233 @c unimplemented. If (b) changes, it might make sense to let this node
13234 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
13237 @subsubsection C and C@t{++} Type and Range Checks
13239 @cindex C and C@t{++} checks
13241 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
13242 is not used. However, if you turn type checking on, @value{GDBN}
13243 considers two variables type equivalent if:
13247 The two variables are structured and have the same structure, union, or
13251 The two variables have the same type name, or types that have been
13252 declared equivalent through @code{typedef}.
13255 @c leaving this out because neither J Gilmore nor R Pesch understand it.
13258 The two @code{struct}, @code{union}, or @code{enum} variables are
13259 declared in the same declaration. (Note: this may not be true for all C
13264 Range checking, if turned on, is done on mathematical operations. Array
13265 indices are not checked, since they are often used to index a pointer
13266 that is not itself an array.
13269 @subsubsection @value{GDBN} and C
13271 The @code{set print union} and @code{show print union} commands apply to
13272 the @code{union} type. When set to @samp{on}, any @code{union} that is
13273 inside a @code{struct} or @code{class} is also printed. Otherwise, it
13274 appears as @samp{@{...@}}.
13276 The @code{@@} operator aids in the debugging of dynamic arrays, formed
13277 with pointers and a memory allocation function. @xref{Expressions,
13280 @node Debugging C Plus Plus
13281 @subsubsection @value{GDBN} Features for C@t{++}
13283 @cindex commands for C@t{++}
13285 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
13286 designed specifically for use with C@t{++}. Here is a summary:
13289 @cindex break in overloaded functions
13290 @item @r{breakpoint menus}
13291 When you want a breakpoint in a function whose name is overloaded,
13292 @value{GDBN} has the capability to display a menu of possible breakpoint
13293 locations to help you specify which function definition you want.
13294 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
13296 @cindex overloading in C@t{++}
13297 @item rbreak @var{regex}
13298 Setting breakpoints using regular expressions is helpful for setting
13299 breakpoints on overloaded functions that are not members of any special
13301 @xref{Set Breaks, ,Setting Breakpoints}.
13303 @cindex C@t{++} exception handling
13306 Debug C@t{++} exception handling using these commands. @xref{Set
13307 Catchpoints, , Setting Catchpoints}.
13309 @cindex inheritance
13310 @item ptype @var{typename}
13311 Print inheritance relationships as well as other information for type
13313 @xref{Symbols, ,Examining the Symbol Table}.
13315 @item info vtbl @var{expression}.
13316 The @code{info vtbl} command can be used to display the virtual
13317 method tables of the object computed by @var{expression}. This shows
13318 one entry per virtual table; there may be multiple virtual tables when
13319 multiple inheritance is in use.
13321 @cindex C@t{++} symbol display
13322 @item set print demangle
13323 @itemx show print demangle
13324 @itemx set print asm-demangle
13325 @itemx show print asm-demangle
13326 Control whether C@t{++} symbols display in their source form, both when
13327 displaying code as C@t{++} source and when displaying disassemblies.
13328 @xref{Print Settings, ,Print Settings}.
13330 @item set print object
13331 @itemx show print object
13332 Choose whether to print derived (actual) or declared types of objects.
13333 @xref{Print Settings, ,Print Settings}.
13335 @item set print vtbl
13336 @itemx show print vtbl
13337 Control the format for printing virtual function tables.
13338 @xref{Print Settings, ,Print Settings}.
13339 (The @code{vtbl} commands do not work on programs compiled with the HP
13340 ANSI C@t{++} compiler (@code{aCC}).)
13342 @kindex set overload-resolution
13343 @cindex overloaded functions, overload resolution
13344 @item set overload-resolution on
13345 Enable overload resolution for C@t{++} expression evaluation. The default
13346 is on. For overloaded functions, @value{GDBN} evaluates the arguments
13347 and searches for a function whose signature matches the argument types,
13348 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
13349 Expressions, ,C@t{++} Expressions}, for details).
13350 If it cannot find a match, it emits a message.
13352 @item set overload-resolution off
13353 Disable overload resolution for C@t{++} expression evaluation. For
13354 overloaded functions that are not class member functions, @value{GDBN}
13355 chooses the first function of the specified name that it finds in the
13356 symbol table, whether or not its arguments are of the correct type. For
13357 overloaded functions that are class member functions, @value{GDBN}
13358 searches for a function whose signature @emph{exactly} matches the
13361 @kindex show overload-resolution
13362 @item show overload-resolution
13363 Show the current setting of overload resolution.
13365 @item @r{Overloaded symbol names}
13366 You can specify a particular definition of an overloaded symbol, using
13367 the same notation that is used to declare such symbols in C@t{++}: type
13368 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
13369 also use the @value{GDBN} command-line word completion facilities to list the
13370 available choices, or to finish the type list for you.
13371 @xref{Completion,, Command Completion}, for details on how to do this.
13374 @node Decimal Floating Point
13375 @subsubsection Decimal Floating Point format
13376 @cindex decimal floating point format
13378 @value{GDBN} can examine, set and perform computations with numbers in
13379 decimal floating point format, which in the C language correspond to the
13380 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
13381 specified by the extension to support decimal floating-point arithmetic.
13383 There are two encodings in use, depending on the architecture: BID (Binary
13384 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
13385 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
13388 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
13389 to manipulate decimal floating point numbers, it is not possible to convert
13390 (using a cast, for example) integers wider than 32-bit to decimal float.
13392 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
13393 point computations, error checking in decimal float operations ignores
13394 underflow, overflow and divide by zero exceptions.
13396 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
13397 to inspect @code{_Decimal128} values stored in floating point registers.
13398 See @ref{PowerPC,,PowerPC} for more details.
13404 @value{GDBN} can be used to debug programs written in D and compiled with
13405 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
13406 specific feature --- dynamic arrays.
13411 @cindex Go (programming language)
13412 @value{GDBN} can be used to debug programs written in Go and compiled with
13413 @file{gccgo} or @file{6g} compilers.
13415 Here is a summary of the Go-specific features and restrictions:
13418 @cindex current Go package
13419 @item The current Go package
13420 The name of the current package does not need to be specified when
13421 specifying global variables and functions.
13423 For example, given the program:
13427 var myglob = "Shall we?"
13433 When stopped inside @code{main} either of these work:
13437 (gdb) p main.myglob
13440 @cindex builtin Go types
13441 @item Builtin Go types
13442 The @code{string} type is recognized by @value{GDBN} and is printed
13445 @cindex builtin Go functions
13446 @item Builtin Go functions
13447 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
13448 function and handles it internally.
13450 @cindex restrictions on Go expressions
13451 @item Restrictions on Go expressions
13452 All Go operators are supported except @code{&^}.
13453 The Go @code{_} ``blank identifier'' is not supported.
13454 Automatic dereferencing of pointers is not supported.
13458 @subsection Objective-C
13460 @cindex Objective-C
13461 This section provides information about some commands and command
13462 options that are useful for debugging Objective-C code. See also
13463 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
13464 few more commands specific to Objective-C support.
13467 * Method Names in Commands::
13468 * The Print Command with Objective-C::
13471 @node Method Names in Commands
13472 @subsubsection Method Names in Commands
13474 The following commands have been extended to accept Objective-C method
13475 names as line specifications:
13477 @kindex clear@r{, and Objective-C}
13478 @kindex break@r{, and Objective-C}
13479 @kindex info line@r{, and Objective-C}
13480 @kindex jump@r{, and Objective-C}
13481 @kindex list@r{, and Objective-C}
13485 @item @code{info line}
13490 A fully qualified Objective-C method name is specified as
13493 -[@var{Class} @var{methodName}]
13496 where the minus sign is used to indicate an instance method and a
13497 plus sign (not shown) is used to indicate a class method. The class
13498 name @var{Class} and method name @var{methodName} are enclosed in
13499 brackets, similar to the way messages are specified in Objective-C
13500 source code. For example, to set a breakpoint at the @code{create}
13501 instance method of class @code{Fruit} in the program currently being
13505 break -[Fruit create]
13508 To list ten program lines around the @code{initialize} class method,
13512 list +[NSText initialize]
13515 In the current version of @value{GDBN}, the plus or minus sign is
13516 required. In future versions of @value{GDBN}, the plus or minus
13517 sign will be optional, but you can use it to narrow the search. It
13518 is also possible to specify just a method name:
13524 You must specify the complete method name, including any colons. If
13525 your program's source files contain more than one @code{create} method,
13526 you'll be presented with a numbered list of classes that implement that
13527 method. Indicate your choice by number, or type @samp{0} to exit if
13530 As another example, to clear a breakpoint established at the
13531 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
13534 clear -[NSWindow makeKeyAndOrderFront:]
13537 @node The Print Command with Objective-C
13538 @subsubsection The Print Command With Objective-C
13539 @cindex Objective-C, print objects
13540 @kindex print-object
13541 @kindex po @r{(@code{print-object})}
13543 The print command has also been extended to accept methods. For example:
13546 print -[@var{object} hash]
13549 @cindex print an Objective-C object description
13550 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
13552 will tell @value{GDBN} to send the @code{hash} message to @var{object}
13553 and print the result. Also, an additional command has been added,
13554 @code{print-object} or @code{po} for short, which is meant to print
13555 the description of an object. However, this command may only work
13556 with certain Objective-C libraries that have a particular hook
13557 function, @code{_NSPrintForDebugger}, defined.
13560 @subsection OpenCL C
13563 This section provides information about @value{GDBN}s OpenCL C support.
13566 * OpenCL C Datatypes::
13567 * OpenCL C Expressions::
13568 * OpenCL C Operators::
13571 @node OpenCL C Datatypes
13572 @subsubsection OpenCL C Datatypes
13574 @cindex OpenCL C Datatypes
13575 @value{GDBN} supports the builtin scalar and vector datatypes specified
13576 by OpenCL 1.1. In addition the half- and double-precision floating point
13577 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
13578 extensions are also known to @value{GDBN}.
13580 @node OpenCL C Expressions
13581 @subsubsection OpenCL C Expressions
13583 @cindex OpenCL C Expressions
13584 @value{GDBN} supports accesses to vector components including the access as
13585 lvalue where possible. Since OpenCL C is based on C99 most C expressions
13586 supported by @value{GDBN} can be used as well.
13588 @node OpenCL C Operators
13589 @subsubsection OpenCL C Operators
13591 @cindex OpenCL C Operators
13592 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
13596 @subsection Fortran
13597 @cindex Fortran-specific support in @value{GDBN}
13599 @value{GDBN} can be used to debug programs written in Fortran, but it
13600 currently supports only the features of Fortran 77 language.
13602 @cindex trailing underscore, in Fortran symbols
13603 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
13604 among them) append an underscore to the names of variables and
13605 functions. When you debug programs compiled by those compilers, you
13606 will need to refer to variables and functions with a trailing
13610 * Fortran Operators:: Fortran operators and expressions
13611 * Fortran Defaults:: Default settings for Fortran
13612 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
13615 @node Fortran Operators
13616 @subsubsection Fortran Operators and Expressions
13618 @cindex Fortran operators and expressions
13620 Operators must be defined on values of specific types. For instance,
13621 @code{+} is defined on numbers, but not on characters or other non-
13622 arithmetic types. Operators are often defined on groups of types.
13626 The exponentiation operator. It raises the first operand to the power
13630 The range operator. Normally used in the form of array(low:high) to
13631 represent a section of array.
13634 The access component operator. Normally used to access elements in derived
13635 types. Also suitable for unions. As unions aren't part of regular Fortran,
13636 this can only happen when accessing a register that uses a gdbarch-defined
13640 @node Fortran Defaults
13641 @subsubsection Fortran Defaults
13643 @cindex Fortran Defaults
13645 Fortran symbols are usually case-insensitive, so @value{GDBN} by
13646 default uses case-insensitive matches for Fortran symbols. You can
13647 change that with the @samp{set case-insensitive} command, see
13648 @ref{Symbols}, for the details.
13650 @node Special Fortran Commands
13651 @subsubsection Special Fortran Commands
13653 @cindex Special Fortran commands
13655 @value{GDBN} has some commands to support Fortran-specific features,
13656 such as displaying common blocks.
13659 @cindex @code{COMMON} blocks, Fortran
13660 @kindex info common
13661 @item info common @r{[}@var{common-name}@r{]}
13662 This command prints the values contained in the Fortran @code{COMMON}
13663 block whose name is @var{common-name}. With no argument, the names of
13664 all @code{COMMON} blocks visible at the current program location are
13671 @cindex Pascal support in @value{GDBN}, limitations
13672 Debugging Pascal programs which use sets, subranges, file variables, or
13673 nested functions does not currently work. @value{GDBN} does not support
13674 entering expressions, printing values, or similar features using Pascal
13677 The Pascal-specific command @code{set print pascal_static-members}
13678 controls whether static members of Pascal objects are displayed.
13679 @xref{Print Settings, pascal_static-members}.
13682 @subsection Modula-2
13684 @cindex Modula-2, @value{GDBN} support
13686 The extensions made to @value{GDBN} to support Modula-2 only support
13687 output from the @sc{gnu} Modula-2 compiler (which is currently being
13688 developed). Other Modula-2 compilers are not currently supported, and
13689 attempting to debug executables produced by them is most likely
13690 to give an error as @value{GDBN} reads in the executable's symbol
13693 @cindex expressions in Modula-2
13695 * M2 Operators:: Built-in operators
13696 * Built-In Func/Proc:: Built-in functions and procedures
13697 * M2 Constants:: Modula-2 constants
13698 * M2 Types:: Modula-2 types
13699 * M2 Defaults:: Default settings for Modula-2
13700 * Deviations:: Deviations from standard Modula-2
13701 * M2 Checks:: Modula-2 type and range checks
13702 * M2 Scope:: The scope operators @code{::} and @code{.}
13703 * GDB/M2:: @value{GDBN} and Modula-2
13707 @subsubsection Operators
13708 @cindex Modula-2 operators
13710 Operators must be defined on values of specific types. For instance,
13711 @code{+} is defined on numbers, but not on structures. Operators are
13712 often defined on groups of types. For the purposes of Modula-2, the
13713 following definitions hold:
13718 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
13722 @emph{Character types} consist of @code{CHAR} and its subranges.
13725 @emph{Floating-point types} consist of @code{REAL}.
13728 @emph{Pointer types} consist of anything declared as @code{POINTER TO
13732 @emph{Scalar types} consist of all of the above.
13735 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
13738 @emph{Boolean types} consist of @code{BOOLEAN}.
13742 The following operators are supported, and appear in order of
13743 increasing precedence:
13747 Function argument or array index separator.
13750 Assignment. The value of @var{var} @code{:=} @var{value} is
13754 Less than, greater than on integral, floating-point, or enumerated
13758 Less than or equal to, greater than or equal to
13759 on integral, floating-point and enumerated types, or set inclusion on
13760 set types. Same precedence as @code{<}.
13762 @item =@r{, }<>@r{, }#
13763 Equality and two ways of expressing inequality, valid on scalar types.
13764 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
13765 available for inequality, since @code{#} conflicts with the script
13769 Set membership. Defined on set types and the types of their members.
13770 Same precedence as @code{<}.
13773 Boolean disjunction. Defined on boolean types.
13776 Boolean conjunction. Defined on boolean types.
13779 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13782 Addition and subtraction on integral and floating-point types, or union
13783 and difference on set types.
13786 Multiplication on integral and floating-point types, or set intersection
13790 Division on floating-point types, or symmetric set difference on set
13791 types. Same precedence as @code{*}.
13794 Integer division and remainder. Defined on integral types. Same
13795 precedence as @code{*}.
13798 Negative. Defined on @code{INTEGER} and @code{REAL} data.
13801 Pointer dereferencing. Defined on pointer types.
13804 Boolean negation. Defined on boolean types. Same precedence as
13808 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
13809 precedence as @code{^}.
13812 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
13815 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
13819 @value{GDBN} and Modula-2 scope operators.
13823 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
13824 treats the use of the operator @code{IN}, or the use of operators
13825 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
13826 @code{<=}, and @code{>=} on sets as an error.
13830 @node Built-In Func/Proc
13831 @subsubsection Built-in Functions and Procedures
13832 @cindex Modula-2 built-ins
13834 Modula-2 also makes available several built-in procedures and functions.
13835 In describing these, the following metavariables are used:
13840 represents an @code{ARRAY} variable.
13843 represents a @code{CHAR} constant or variable.
13846 represents a variable or constant of integral type.
13849 represents an identifier that belongs to a set. Generally used in the
13850 same function with the metavariable @var{s}. The type of @var{s} should
13851 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
13854 represents a variable or constant of integral or floating-point type.
13857 represents a variable or constant of floating-point type.
13863 represents a variable.
13866 represents a variable or constant of one of many types. See the
13867 explanation of the function for details.
13870 All Modula-2 built-in procedures also return a result, described below.
13874 Returns the absolute value of @var{n}.
13877 If @var{c} is a lower case letter, it returns its upper case
13878 equivalent, otherwise it returns its argument.
13881 Returns the character whose ordinal value is @var{i}.
13884 Decrements the value in the variable @var{v} by one. Returns the new value.
13886 @item DEC(@var{v},@var{i})
13887 Decrements the value in the variable @var{v} by @var{i}. Returns the
13890 @item EXCL(@var{m},@var{s})
13891 Removes the element @var{m} from the set @var{s}. Returns the new
13894 @item FLOAT(@var{i})
13895 Returns the floating point equivalent of the integer @var{i}.
13897 @item HIGH(@var{a})
13898 Returns the index of the last member of @var{a}.
13901 Increments the value in the variable @var{v} by one. Returns the new value.
13903 @item INC(@var{v},@var{i})
13904 Increments the value in the variable @var{v} by @var{i}. Returns the
13907 @item INCL(@var{m},@var{s})
13908 Adds the element @var{m} to the set @var{s} if it is not already
13909 there. Returns the new set.
13912 Returns the maximum value of the type @var{t}.
13915 Returns the minimum value of the type @var{t}.
13918 Returns boolean TRUE if @var{i} is an odd number.
13921 Returns the ordinal value of its argument. For example, the ordinal
13922 value of a character is its @sc{ascii} value (on machines supporting the
13923 @sc{ascii} character set). @var{x} must be of an ordered type, which include
13924 integral, character and enumerated types.
13926 @item SIZE(@var{x})
13927 Returns the size of its argument. @var{x} can be a variable or a type.
13929 @item TRUNC(@var{r})
13930 Returns the integral part of @var{r}.
13932 @item TSIZE(@var{x})
13933 Returns the size of its argument. @var{x} can be a variable or a type.
13935 @item VAL(@var{t},@var{i})
13936 Returns the member of the type @var{t} whose ordinal value is @var{i}.
13940 @emph{Warning:} Sets and their operations are not yet supported, so
13941 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
13945 @cindex Modula-2 constants
13947 @subsubsection Constants
13949 @value{GDBN} allows you to express the constants of Modula-2 in the following
13955 Integer constants are simply a sequence of digits. When used in an
13956 expression, a constant is interpreted to be type-compatible with the
13957 rest of the expression. Hexadecimal integers are specified by a
13958 trailing @samp{H}, and octal integers by a trailing @samp{B}.
13961 Floating point constants appear as a sequence of digits, followed by a
13962 decimal point and another sequence of digits. An optional exponent can
13963 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
13964 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
13965 digits of the floating point constant must be valid decimal (base 10)
13969 Character constants consist of a single character enclosed by a pair of
13970 like quotes, either single (@code{'}) or double (@code{"}). They may
13971 also be expressed by their ordinal value (their @sc{ascii} value, usually)
13972 followed by a @samp{C}.
13975 String constants consist of a sequence of characters enclosed by a
13976 pair of like quotes, either single (@code{'}) or double (@code{"}).
13977 Escape sequences in the style of C are also allowed. @xref{C
13978 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
13982 Enumerated constants consist of an enumerated identifier.
13985 Boolean constants consist of the identifiers @code{TRUE} and
13989 Pointer constants consist of integral values only.
13992 Set constants are not yet supported.
13996 @subsubsection Modula-2 Types
13997 @cindex Modula-2 types
13999 Currently @value{GDBN} can print the following data types in Modula-2
14000 syntax: array types, record types, set types, pointer types, procedure
14001 types, enumerated types, subrange types and base types. You can also
14002 print the contents of variables declared using these type.
14003 This section gives a number of simple source code examples together with
14004 sample @value{GDBN} sessions.
14006 The first example contains the following section of code:
14015 and you can request @value{GDBN} to interrogate the type and value of
14016 @code{r} and @code{s}.
14019 (@value{GDBP}) print s
14021 (@value{GDBP}) ptype s
14023 (@value{GDBP}) print r
14025 (@value{GDBP}) ptype r
14030 Likewise if your source code declares @code{s} as:
14034 s: SET ['A'..'Z'] ;
14038 then you may query the type of @code{s} by:
14041 (@value{GDBP}) ptype s
14042 type = SET ['A'..'Z']
14046 Note that at present you cannot interactively manipulate set
14047 expressions using the debugger.
14049 The following example shows how you might declare an array in Modula-2
14050 and how you can interact with @value{GDBN} to print its type and contents:
14054 s: ARRAY [-10..10] OF CHAR ;
14058 (@value{GDBP}) ptype s
14059 ARRAY [-10..10] OF CHAR
14062 Note that the array handling is not yet complete and although the type
14063 is printed correctly, expression handling still assumes that all
14064 arrays have a lower bound of zero and not @code{-10} as in the example
14067 Here are some more type related Modula-2 examples:
14071 colour = (blue, red, yellow, green) ;
14072 t = [blue..yellow] ;
14080 The @value{GDBN} interaction shows how you can query the data type
14081 and value of a variable.
14084 (@value{GDBP}) print s
14086 (@value{GDBP}) ptype t
14087 type = [blue..yellow]
14091 In this example a Modula-2 array is declared and its contents
14092 displayed. Observe that the contents are written in the same way as
14093 their @code{C} counterparts.
14097 s: ARRAY [1..5] OF CARDINAL ;
14103 (@value{GDBP}) print s
14104 $1 = @{1, 0, 0, 0, 0@}
14105 (@value{GDBP}) ptype s
14106 type = ARRAY [1..5] OF CARDINAL
14109 The Modula-2 language interface to @value{GDBN} also understands
14110 pointer types as shown in this example:
14114 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
14121 and you can request that @value{GDBN} describes the type of @code{s}.
14124 (@value{GDBP}) ptype s
14125 type = POINTER TO ARRAY [1..5] OF CARDINAL
14128 @value{GDBN} handles compound types as we can see in this example.
14129 Here we combine array types, record types, pointer types and subrange
14140 myarray = ARRAY myrange OF CARDINAL ;
14141 myrange = [-2..2] ;
14143 s: POINTER TO ARRAY myrange OF foo ;
14147 and you can ask @value{GDBN} to describe the type of @code{s} as shown
14151 (@value{GDBP}) ptype s
14152 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
14155 f3 : ARRAY [-2..2] OF CARDINAL;
14160 @subsubsection Modula-2 Defaults
14161 @cindex Modula-2 defaults
14163 If type and range checking are set automatically by @value{GDBN}, they
14164 both default to @code{on} whenever the working language changes to
14165 Modula-2. This happens regardless of whether you or @value{GDBN}
14166 selected the working language.
14168 If you allow @value{GDBN} to set the language automatically, then entering
14169 code compiled from a file whose name ends with @file{.mod} sets the
14170 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
14171 Infer the Source Language}, for further details.
14174 @subsubsection Deviations from Standard Modula-2
14175 @cindex Modula-2, deviations from
14177 A few changes have been made to make Modula-2 programs easier to debug.
14178 This is done primarily via loosening its type strictness:
14182 Unlike in standard Modula-2, pointer constants can be formed by
14183 integers. This allows you to modify pointer variables during
14184 debugging. (In standard Modula-2, the actual address contained in a
14185 pointer variable is hidden from you; it can only be modified
14186 through direct assignment to another pointer variable or expression that
14187 returned a pointer.)
14190 C escape sequences can be used in strings and characters to represent
14191 non-printable characters. @value{GDBN} prints out strings with these
14192 escape sequences embedded. Single non-printable characters are
14193 printed using the @samp{CHR(@var{nnn})} format.
14196 The assignment operator (@code{:=}) returns the value of its right-hand
14200 All built-in procedures both modify @emph{and} return their argument.
14204 @subsubsection Modula-2 Type and Range Checks
14205 @cindex Modula-2 checks
14208 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
14211 @c FIXME remove warning when type/range checks added
14213 @value{GDBN} considers two Modula-2 variables type equivalent if:
14217 They are of types that have been declared equivalent via a @code{TYPE
14218 @var{t1} = @var{t2}} statement
14221 They have been declared on the same line. (Note: This is true of the
14222 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
14225 As long as type checking is enabled, any attempt to combine variables
14226 whose types are not equivalent is an error.
14228 Range checking is done on all mathematical operations, assignment, array
14229 index bounds, and all built-in functions and procedures.
14232 @subsubsection The Scope Operators @code{::} and @code{.}
14234 @cindex @code{.}, Modula-2 scope operator
14235 @cindex colon, doubled as scope operator
14237 @vindex colon-colon@r{, in Modula-2}
14238 @c Info cannot handle :: but TeX can.
14241 @vindex ::@r{, in Modula-2}
14244 There are a few subtle differences between the Modula-2 scope operator
14245 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
14250 @var{module} . @var{id}
14251 @var{scope} :: @var{id}
14255 where @var{scope} is the name of a module or a procedure,
14256 @var{module} the name of a module, and @var{id} is any declared
14257 identifier within your program, except another module.
14259 Using the @code{::} operator makes @value{GDBN} search the scope
14260 specified by @var{scope} for the identifier @var{id}. If it is not
14261 found in the specified scope, then @value{GDBN} searches all scopes
14262 enclosing the one specified by @var{scope}.
14264 Using the @code{.} operator makes @value{GDBN} search the current scope for
14265 the identifier specified by @var{id} that was imported from the
14266 definition module specified by @var{module}. With this operator, it is
14267 an error if the identifier @var{id} was not imported from definition
14268 module @var{module}, or if @var{id} is not an identifier in
14272 @subsubsection @value{GDBN} and Modula-2
14274 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
14275 Five subcommands of @code{set print} and @code{show print} apply
14276 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
14277 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
14278 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
14279 analogue in Modula-2.
14281 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
14282 with any language, is not useful with Modula-2. Its
14283 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
14284 created in Modula-2 as they can in C or C@t{++}. However, because an
14285 address can be specified by an integral constant, the construct
14286 @samp{@{@var{type}@}@var{adrexp}} is still useful.
14288 @cindex @code{#} in Modula-2
14289 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
14290 interpreted as the beginning of a comment. Use @code{<>} instead.
14296 The extensions made to @value{GDBN} for Ada only support
14297 output from the @sc{gnu} Ada (GNAT) compiler.
14298 Other Ada compilers are not currently supported, and
14299 attempting to debug executables produced by them is most likely
14303 @cindex expressions in Ada
14305 * Ada Mode Intro:: General remarks on the Ada syntax
14306 and semantics supported by Ada mode
14308 * Omissions from Ada:: Restrictions on the Ada expression syntax.
14309 * Additions to Ada:: Extensions of the Ada expression syntax.
14310 * Stopping Before Main Program:: Debugging the program during elaboration.
14311 * Ada Tasks:: Listing and setting breakpoints in tasks.
14312 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
14313 * Ravenscar Profile:: Tasking Support when using the Ravenscar
14315 * Ada Glitches:: Known peculiarities of Ada mode.
14318 @node Ada Mode Intro
14319 @subsubsection Introduction
14320 @cindex Ada mode, general
14322 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
14323 syntax, with some extensions.
14324 The philosophy behind the design of this subset is
14328 That @value{GDBN} should provide basic literals and access to operations for
14329 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
14330 leaving more sophisticated computations to subprograms written into the
14331 program (which therefore may be called from @value{GDBN}).
14334 That type safety and strict adherence to Ada language restrictions
14335 are not particularly important to the @value{GDBN} user.
14338 That brevity is important to the @value{GDBN} user.
14341 Thus, for brevity, the debugger acts as if all names declared in
14342 user-written packages are directly visible, even if they are not visible
14343 according to Ada rules, thus making it unnecessary to fully qualify most
14344 names with their packages, regardless of context. Where this causes
14345 ambiguity, @value{GDBN} asks the user's intent.
14347 The debugger will start in Ada mode if it detects an Ada main program.
14348 As for other languages, it will enter Ada mode when stopped in a program that
14349 was translated from an Ada source file.
14351 While in Ada mode, you may use `@t{--}' for comments. This is useful
14352 mostly for documenting command files. The standard @value{GDBN} comment
14353 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
14354 middle (to allow based literals).
14356 The debugger supports limited overloading. Given a subprogram call in which
14357 the function symbol has multiple definitions, it will use the number of
14358 actual parameters and some information about their types to attempt to narrow
14359 the set of definitions. It also makes very limited use of context, preferring
14360 procedures to functions in the context of the @code{call} command, and
14361 functions to procedures elsewhere.
14363 @node Omissions from Ada
14364 @subsubsection Omissions from Ada
14365 @cindex Ada, omissions from
14367 Here are the notable omissions from the subset:
14371 Only a subset of the attributes are supported:
14375 @t{'First}, @t{'Last}, and @t{'Length}
14376 on array objects (not on types and subtypes).
14379 @t{'Min} and @t{'Max}.
14382 @t{'Pos} and @t{'Val}.
14388 @t{'Range} on array objects (not subtypes), but only as the right
14389 operand of the membership (@code{in}) operator.
14392 @t{'Access}, @t{'Unchecked_Access}, and
14393 @t{'Unrestricted_Access} (a GNAT extension).
14401 @code{Characters.Latin_1} are not available and
14402 concatenation is not implemented. Thus, escape characters in strings are
14403 not currently available.
14406 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
14407 equality of representations. They will generally work correctly
14408 for strings and arrays whose elements have integer or enumeration types.
14409 They may not work correctly for arrays whose element
14410 types have user-defined equality, for arrays of real values
14411 (in particular, IEEE-conformant floating point, because of negative
14412 zeroes and NaNs), and for arrays whose elements contain unused bits with
14413 indeterminate values.
14416 The other component-by-component array operations (@code{and}, @code{or},
14417 @code{xor}, @code{not}, and relational tests other than equality)
14418 are not implemented.
14421 @cindex array aggregates (Ada)
14422 @cindex record aggregates (Ada)
14423 @cindex aggregates (Ada)
14424 There is limited support for array and record aggregates. They are
14425 permitted only on the right sides of assignments, as in these examples:
14428 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
14429 (@value{GDBP}) set An_Array := (1, others => 0)
14430 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
14431 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
14432 (@value{GDBP}) set A_Record := (1, "Peter", True);
14433 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
14437 discriminant's value by assigning an aggregate has an
14438 undefined effect if that discriminant is used within the record.
14439 However, you can first modify discriminants by directly assigning to
14440 them (which normally would not be allowed in Ada), and then performing an
14441 aggregate assignment. For example, given a variable @code{A_Rec}
14442 declared to have a type such as:
14445 type Rec (Len : Small_Integer := 0) is record
14447 Vals : IntArray (1 .. Len);
14451 you can assign a value with a different size of @code{Vals} with two
14455 (@value{GDBP}) set A_Rec.Len := 4
14456 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
14459 As this example also illustrates, @value{GDBN} is very loose about the usual
14460 rules concerning aggregates. You may leave out some of the
14461 components of an array or record aggregate (such as the @code{Len}
14462 component in the assignment to @code{A_Rec} above); they will retain their
14463 original values upon assignment. You may freely use dynamic values as
14464 indices in component associations. You may even use overlapping or
14465 redundant component associations, although which component values are
14466 assigned in such cases is not defined.
14469 Calls to dispatching subprograms are not implemented.
14472 The overloading algorithm is much more limited (i.e., less selective)
14473 than that of real Ada. It makes only limited use of the context in
14474 which a subexpression appears to resolve its meaning, and it is much
14475 looser in its rules for allowing type matches. As a result, some
14476 function calls will be ambiguous, and the user will be asked to choose
14477 the proper resolution.
14480 The @code{new} operator is not implemented.
14483 Entry calls are not implemented.
14486 Aside from printing, arithmetic operations on the native VAX floating-point
14487 formats are not supported.
14490 It is not possible to slice a packed array.
14493 The names @code{True} and @code{False}, when not part of a qualified name,
14494 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
14496 Should your program
14497 redefine these names in a package or procedure (at best a dubious practice),
14498 you will have to use fully qualified names to access their new definitions.
14501 @node Additions to Ada
14502 @subsubsection Additions to Ada
14503 @cindex Ada, deviations from
14505 As it does for other languages, @value{GDBN} makes certain generic
14506 extensions to Ada (@pxref{Expressions}):
14510 If the expression @var{E} is a variable residing in memory (typically
14511 a local variable or array element) and @var{N} is a positive integer,
14512 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
14513 @var{N}-1 adjacent variables following it in memory as an array. In
14514 Ada, this operator is generally not necessary, since its prime use is
14515 in displaying parts of an array, and slicing will usually do this in
14516 Ada. However, there are occasional uses when debugging programs in
14517 which certain debugging information has been optimized away.
14520 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
14521 appears in function or file @var{B}.'' When @var{B} is a file name,
14522 you must typically surround it in single quotes.
14525 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
14526 @var{type} that appears at address @var{addr}.''
14529 A name starting with @samp{$} is a convenience variable
14530 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
14533 In addition, @value{GDBN} provides a few other shortcuts and outright
14534 additions specific to Ada:
14538 The assignment statement is allowed as an expression, returning
14539 its right-hand operand as its value. Thus, you may enter
14542 (@value{GDBP}) set x := y + 3
14543 (@value{GDBP}) print A(tmp := y + 1)
14547 The semicolon is allowed as an ``operator,'' returning as its value
14548 the value of its right-hand operand.
14549 This allows, for example,
14550 complex conditional breaks:
14553 (@value{GDBP}) break f
14554 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
14558 Rather than use catenation and symbolic character names to introduce special
14559 characters into strings, one may instead use a special bracket notation,
14560 which is also used to print strings. A sequence of characters of the form
14561 @samp{["@var{XX}"]} within a string or character literal denotes the
14562 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
14563 sequence of characters @samp{["""]} also denotes a single quotation mark
14564 in strings. For example,
14566 "One line.["0a"]Next line.["0a"]"
14569 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
14573 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
14574 @t{'Max} is optional (and is ignored in any case). For example, it is valid
14578 (@value{GDBP}) print 'max(x, y)
14582 When printing arrays, @value{GDBN} uses positional notation when the
14583 array has a lower bound of 1, and uses a modified named notation otherwise.
14584 For example, a one-dimensional array of three integers with a lower bound
14585 of 3 might print as
14592 That is, in contrast to valid Ada, only the first component has a @code{=>}
14596 You may abbreviate attributes in expressions with any unique,
14597 multi-character subsequence of
14598 their names (an exact match gets preference).
14599 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
14600 in place of @t{a'length}.
14603 @cindex quoting Ada internal identifiers
14604 Since Ada is case-insensitive, the debugger normally maps identifiers you type
14605 to lower case. The GNAT compiler uses upper-case characters for
14606 some of its internal identifiers, which are normally of no interest to users.
14607 For the rare occasions when you actually have to look at them,
14608 enclose them in angle brackets to avoid the lower-case mapping.
14611 (@value{GDBP}) print <JMPBUF_SAVE>[0]
14615 Printing an object of class-wide type or dereferencing an
14616 access-to-class-wide value will display all the components of the object's
14617 specific type (as indicated by its run-time tag). Likewise, component
14618 selection on such a value will operate on the specific type of the
14623 @node Stopping Before Main Program
14624 @subsubsection Stopping at the Very Beginning
14626 @cindex breakpointing Ada elaboration code
14627 It is sometimes necessary to debug the program during elaboration, and
14628 before reaching the main procedure.
14629 As defined in the Ada Reference
14630 Manual, the elaboration code is invoked from a procedure called
14631 @code{adainit}. To run your program up to the beginning of
14632 elaboration, simply use the following two commands:
14633 @code{tbreak adainit} and @code{run}.
14636 @subsubsection Extensions for Ada Tasks
14637 @cindex Ada, tasking
14639 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
14640 @value{GDBN} provides the following task-related commands:
14645 This command shows a list of current Ada tasks, as in the following example:
14652 (@value{GDBP}) info tasks
14653 ID TID P-ID Pri State Name
14654 1 8088000 0 15 Child Activation Wait main_task
14655 2 80a4000 1 15 Accept Statement b
14656 3 809a800 1 15 Child Activation Wait a
14657 * 4 80ae800 3 15 Runnable c
14662 In this listing, the asterisk before the last task indicates it to be the
14663 task currently being inspected.
14667 Represents @value{GDBN}'s internal task number.
14673 The parent's task ID (@value{GDBN}'s internal task number).
14676 The base priority of the task.
14679 Current state of the task.
14683 The task has been created but has not been activated. It cannot be
14687 The task is not blocked for any reason known to Ada. (It may be waiting
14688 for a mutex, though.) It is conceptually "executing" in normal mode.
14691 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
14692 that were waiting on terminate alternatives have been awakened and have
14693 terminated themselves.
14695 @item Child Activation Wait
14696 The task is waiting for created tasks to complete activation.
14698 @item Accept Statement
14699 The task is waiting on an accept or selective wait statement.
14701 @item Waiting on entry call
14702 The task is waiting on an entry call.
14704 @item Async Select Wait
14705 The task is waiting to start the abortable part of an asynchronous
14709 The task is waiting on a select statement with only a delay
14712 @item Child Termination Wait
14713 The task is sleeping having completed a master within itself, and is
14714 waiting for the tasks dependent on that master to become terminated or
14715 waiting on a terminate Phase.
14717 @item Wait Child in Term Alt
14718 The task is sleeping waiting for tasks on terminate alternatives to
14719 finish terminating.
14721 @item Accepting RV with @var{taskno}
14722 The task is accepting a rendez-vous with the task @var{taskno}.
14726 Name of the task in the program.
14730 @kindex info task @var{taskno}
14731 @item info task @var{taskno}
14732 This command shows detailled informations on the specified task, as in
14733 the following example:
14738 (@value{GDBP}) info tasks
14739 ID TID P-ID Pri State Name
14740 1 8077880 0 15 Child Activation Wait main_task
14741 * 2 807c468 1 15 Runnable task_1
14742 (@value{GDBP}) info task 2
14743 Ada Task: 0x807c468
14746 Parent: 1 (main_task)
14752 @kindex task@r{ (Ada)}
14753 @cindex current Ada task ID
14754 This command prints the ID of the current task.
14760 (@value{GDBP}) info tasks
14761 ID TID P-ID Pri State Name
14762 1 8077870 0 15 Child Activation Wait main_task
14763 * 2 807c458 1 15 Runnable t
14764 (@value{GDBP}) task
14765 [Current task is 2]
14768 @item task @var{taskno}
14769 @cindex Ada task switching
14770 This command is like the @code{thread @var{threadno}}
14771 command (@pxref{Threads}). It switches the context of debugging
14772 from the current task to the given task.
14778 (@value{GDBP}) info tasks
14779 ID TID P-ID Pri State Name
14780 1 8077870 0 15 Child Activation Wait main_task
14781 * 2 807c458 1 15 Runnable t
14782 (@value{GDBP}) task 1
14783 [Switching to task 1]
14784 #0 0x8067726 in pthread_cond_wait ()
14786 #0 0x8067726 in pthread_cond_wait ()
14787 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
14788 #2 0x805cb63 in system.task_primitives.operations.sleep ()
14789 #3 0x806153e in system.tasking.stages.activate_tasks ()
14790 #4 0x804aacc in un () at un.adb:5
14793 @item break @var{linespec} task @var{taskno}
14794 @itemx break @var{linespec} task @var{taskno} if @dots{}
14795 @cindex breakpoints and tasks, in Ada
14796 @cindex task breakpoints, in Ada
14797 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
14798 These commands are like the @code{break @dots{} thread @dots{}}
14799 command (@pxref{Thread Stops}).
14800 @var{linespec} specifies source lines, as described
14801 in @ref{Specify Location}.
14803 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
14804 to specify that you only want @value{GDBN} to stop the program when a
14805 particular Ada task reaches this breakpoint. @var{taskno} is one of the
14806 numeric task identifiers assigned by @value{GDBN}, shown in the first
14807 column of the @samp{info tasks} display.
14809 If you do not specify @samp{task @var{taskno}} when you set a
14810 breakpoint, the breakpoint applies to @emph{all} tasks of your
14813 You can use the @code{task} qualifier on conditional breakpoints as
14814 well; in this case, place @samp{task @var{taskno}} before the
14815 breakpoint condition (before the @code{if}).
14823 (@value{GDBP}) info tasks
14824 ID TID P-ID Pri State Name
14825 1 140022020 0 15 Child Activation Wait main_task
14826 2 140045060 1 15 Accept/Select Wait t2
14827 3 140044840 1 15 Runnable t1
14828 * 4 140056040 1 15 Runnable t3
14829 (@value{GDBP}) b 15 task 2
14830 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
14831 (@value{GDBP}) cont
14836 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
14838 (@value{GDBP}) info tasks
14839 ID TID P-ID Pri State Name
14840 1 140022020 0 15 Child Activation Wait main_task
14841 * 2 140045060 1 15 Runnable t2
14842 3 140044840 1 15 Runnable t1
14843 4 140056040 1 15 Delay Sleep t3
14847 @node Ada Tasks and Core Files
14848 @subsubsection Tasking Support when Debugging Core Files
14849 @cindex Ada tasking and core file debugging
14851 When inspecting a core file, as opposed to debugging a live program,
14852 tasking support may be limited or even unavailable, depending on
14853 the platform being used.
14854 For instance, on x86-linux, the list of tasks is available, but task
14855 switching is not supported. On Tru64, however, task switching will work
14858 On certain platforms, including Tru64, the debugger needs to perform some
14859 memory writes in order to provide Ada tasking support. When inspecting
14860 a core file, this means that the core file must be opened with read-write
14861 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
14862 Under these circumstances, you should make a backup copy of the core
14863 file before inspecting it with @value{GDBN}.
14865 @node Ravenscar Profile
14866 @subsubsection Tasking Support when using the Ravenscar Profile
14867 @cindex Ravenscar Profile
14869 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
14870 specifically designed for systems with safety-critical real-time
14874 @kindex set ravenscar task-switching on
14875 @cindex task switching with program using Ravenscar Profile
14876 @item set ravenscar task-switching on
14877 Allows task switching when debugging a program that uses the Ravenscar
14878 Profile. This is the default.
14880 @kindex set ravenscar task-switching off
14881 @item set ravenscar task-switching off
14882 Turn off task switching when debugging a program that uses the Ravenscar
14883 Profile. This is mostly intended to disable the code that adds support
14884 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
14885 the Ravenscar runtime is preventing @value{GDBN} from working properly.
14886 To be effective, this command should be run before the program is started.
14888 @kindex show ravenscar task-switching
14889 @item show ravenscar task-switching
14890 Show whether it is possible to switch from task to task in a program
14891 using the Ravenscar Profile.
14896 @subsubsection Known Peculiarities of Ada Mode
14897 @cindex Ada, problems
14899 Besides the omissions listed previously (@pxref{Omissions from Ada}),
14900 we know of several problems with and limitations of Ada mode in
14902 some of which will be fixed with planned future releases of the debugger
14903 and the GNU Ada compiler.
14907 Static constants that the compiler chooses not to materialize as objects in
14908 storage are invisible to the debugger.
14911 Named parameter associations in function argument lists are ignored (the
14912 argument lists are treated as positional).
14915 Many useful library packages are currently invisible to the debugger.
14918 Fixed-point arithmetic, conversions, input, and output is carried out using
14919 floating-point arithmetic, and may give results that only approximate those on
14923 The GNAT compiler never generates the prefix @code{Standard} for any of
14924 the standard symbols defined by the Ada language. @value{GDBN} knows about
14925 this: it will strip the prefix from names when you use it, and will never
14926 look for a name you have so qualified among local symbols, nor match against
14927 symbols in other packages or subprograms. If you have
14928 defined entities anywhere in your program other than parameters and
14929 local variables whose simple names match names in @code{Standard},
14930 GNAT's lack of qualification here can cause confusion. When this happens,
14931 you can usually resolve the confusion
14932 by qualifying the problematic names with package
14933 @code{Standard} explicitly.
14936 Older versions of the compiler sometimes generate erroneous debugging
14937 information, resulting in the debugger incorrectly printing the value
14938 of affected entities. In some cases, the debugger is able to work
14939 around an issue automatically. In other cases, the debugger is able
14940 to work around the issue, but the work-around has to be specifically
14943 @kindex set ada trust-PAD-over-XVS
14944 @kindex show ada trust-PAD-over-XVS
14947 @item set ada trust-PAD-over-XVS on
14948 Configure GDB to strictly follow the GNAT encoding when computing the
14949 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
14950 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
14951 a complete description of the encoding used by the GNAT compiler).
14952 This is the default.
14954 @item set ada trust-PAD-over-XVS off
14955 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
14956 sometimes prints the wrong value for certain entities, changing @code{ada
14957 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
14958 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
14959 @code{off}, but this incurs a slight performance penalty, so it is
14960 recommended to leave this setting to @code{on} unless necessary.
14964 @node Unsupported Languages
14965 @section Unsupported Languages
14967 @cindex unsupported languages
14968 @cindex minimal language
14969 In addition to the other fully-supported programming languages,
14970 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
14971 It does not represent a real programming language, but provides a set
14972 of capabilities close to what the C or assembly languages provide.
14973 This should allow most simple operations to be performed while debugging
14974 an application that uses a language currently not supported by @value{GDBN}.
14976 If the language is set to @code{auto}, @value{GDBN} will automatically
14977 select this language if the current frame corresponds to an unsupported
14981 @chapter Examining the Symbol Table
14983 The commands described in this chapter allow you to inquire about the
14984 symbols (names of variables, functions and types) defined in your
14985 program. This information is inherent in the text of your program and
14986 does not change as your program executes. @value{GDBN} finds it in your
14987 program's symbol table, in the file indicated when you started @value{GDBN}
14988 (@pxref{File Options, ,Choosing Files}), or by one of the
14989 file-management commands (@pxref{Files, ,Commands to Specify Files}).
14991 @cindex symbol names
14992 @cindex names of symbols
14993 @cindex quoting names
14994 Occasionally, you may need to refer to symbols that contain unusual
14995 characters, which @value{GDBN} ordinarily treats as word delimiters. The
14996 most frequent case is in referring to static variables in other
14997 source files (@pxref{Variables,,Program Variables}). File names
14998 are recorded in object files as debugging symbols, but @value{GDBN} would
14999 ordinarily parse a typical file name, like @file{foo.c}, as the three words
15000 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
15001 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
15008 looks up the value of @code{x} in the scope of the file @file{foo.c}.
15011 @cindex case-insensitive symbol names
15012 @cindex case sensitivity in symbol names
15013 @kindex set case-sensitive
15014 @item set case-sensitive on
15015 @itemx set case-sensitive off
15016 @itemx set case-sensitive auto
15017 Normally, when @value{GDBN} looks up symbols, it matches their names
15018 with case sensitivity determined by the current source language.
15019 Occasionally, you may wish to control that. The command @code{set
15020 case-sensitive} lets you do that by specifying @code{on} for
15021 case-sensitive matches or @code{off} for case-insensitive ones. If
15022 you specify @code{auto}, case sensitivity is reset to the default
15023 suitable for the source language. The default is case-sensitive
15024 matches for all languages except for Fortran, for which the default is
15025 case-insensitive matches.
15027 @kindex show case-sensitive
15028 @item show case-sensitive
15029 This command shows the current setting of case sensitivity for symbols
15032 @kindex info address
15033 @cindex address of a symbol
15034 @item info address @var{symbol}
15035 Describe where the data for @var{symbol} is stored. For a register
15036 variable, this says which register it is kept in. For a non-register
15037 local variable, this prints the stack-frame offset at which the variable
15040 Note the contrast with @samp{print &@var{symbol}}, which does not work
15041 at all for a register variable, and for a stack local variable prints
15042 the exact address of the current instantiation of the variable.
15044 @kindex info symbol
15045 @cindex symbol from address
15046 @cindex closest symbol and offset for an address
15047 @item info symbol @var{addr}
15048 Print the name of a symbol which is stored at the address @var{addr}.
15049 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
15050 nearest symbol and an offset from it:
15053 (@value{GDBP}) info symbol 0x54320
15054 _initialize_vx + 396 in section .text
15058 This is the opposite of the @code{info address} command. You can use
15059 it to find out the name of a variable or a function given its address.
15061 For dynamically linked executables, the name of executable or shared
15062 library containing the symbol is also printed:
15065 (@value{GDBP}) info symbol 0x400225
15066 _start + 5 in section .text of /tmp/a.out
15067 (@value{GDBP}) info symbol 0x2aaaac2811cf
15068 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
15072 @item whatis [@var{arg}]
15073 Print the data type of @var{arg}, which can be either an expression
15074 or a name of a data type. With no argument, print the data type of
15075 @code{$}, the last value in the value history.
15077 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
15078 is not actually evaluated, and any side-effecting operations (such as
15079 assignments or function calls) inside it do not take place.
15081 If @var{arg} is a variable or an expression, @code{whatis} prints its
15082 literal type as it is used in the source code. If the type was
15083 defined using a @code{typedef}, @code{whatis} will @emph{not} print
15084 the data type underlying the @code{typedef}. If the type of the
15085 variable or the expression is a compound data type, such as
15086 @code{struct} or @code{class}, @code{whatis} never prints their
15087 fields or methods. It just prints the @code{struct}/@code{class}
15088 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
15089 such a compound data type, use @code{ptype}.
15091 If @var{arg} is a type name that was defined using @code{typedef},
15092 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
15093 Unrolling means that @code{whatis} will show the underlying type used
15094 in the @code{typedef} declaration of @var{arg}. However, if that
15095 underlying type is also a @code{typedef}, @code{whatis} will not
15098 For C code, the type names may also have the form @samp{class
15099 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
15100 @var{union-tag}} or @samp{enum @var{enum-tag}}.
15103 @item ptype [@var{arg}]
15104 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
15105 detailed description of the type, instead of just the name of the type.
15106 @xref{Expressions, ,Expressions}.
15108 Contrary to @code{whatis}, @code{ptype} always unrolls any
15109 @code{typedef}s in its argument declaration, whether the argument is
15110 a variable, expression, or a data type. This means that @code{ptype}
15111 of a variable or an expression will not print literally its type as
15112 present in the source code---use @code{whatis} for that. @code{typedef}s at
15113 the pointer or reference targets are also unrolled. Only @code{typedef}s of
15114 fields, methods and inner @code{class typedef}s of @code{struct}s,
15115 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
15117 For example, for this variable declaration:
15120 typedef double real_t;
15121 struct complex @{ real_t real; double imag; @};
15122 typedef struct complex complex_t;
15124 real_t *real_pointer_var;
15128 the two commands give this output:
15132 (@value{GDBP}) whatis var
15134 (@value{GDBP}) ptype var
15135 type = struct complex @{
15139 (@value{GDBP}) whatis complex_t
15140 type = struct complex
15141 (@value{GDBP}) whatis struct complex
15142 type = struct complex
15143 (@value{GDBP}) ptype struct complex
15144 type = struct complex @{
15148 (@value{GDBP}) whatis real_pointer_var
15150 (@value{GDBP}) ptype real_pointer_var
15156 As with @code{whatis}, using @code{ptype} without an argument refers to
15157 the type of @code{$}, the last value in the value history.
15159 @cindex incomplete type
15160 Sometimes, programs use opaque data types or incomplete specifications
15161 of complex data structure. If the debug information included in the
15162 program does not allow @value{GDBN} to display a full declaration of
15163 the data type, it will say @samp{<incomplete type>}. For example,
15164 given these declarations:
15168 struct foo *fooptr;
15172 but no definition for @code{struct foo} itself, @value{GDBN} will say:
15175 (@value{GDBP}) ptype foo
15176 $1 = <incomplete type>
15180 ``Incomplete type'' is C terminology for data types that are not
15181 completely specified.
15184 @item info types @var{regexp}
15186 Print a brief description of all types whose names match the regular
15187 expression @var{regexp} (or all types in your program, if you supply
15188 no argument). Each complete typename is matched as though it were a
15189 complete line; thus, @samp{i type value} gives information on all
15190 types in your program whose names include the string @code{value}, but
15191 @samp{i type ^value$} gives information only on types whose complete
15192 name is @code{value}.
15194 This command differs from @code{ptype} in two ways: first, like
15195 @code{whatis}, it does not print a detailed description; second, it
15196 lists all source files where a type is defined.
15199 @cindex local variables
15200 @item info scope @var{location}
15201 List all the variables local to a particular scope. This command
15202 accepts a @var{location} argument---a function name, a source line, or
15203 an address preceded by a @samp{*}, and prints all the variables local
15204 to the scope defined by that location. (@xref{Specify Location}, for
15205 details about supported forms of @var{location}.) For example:
15208 (@value{GDBP}) @b{info scope command_line_handler}
15209 Scope for command_line_handler:
15210 Symbol rl is an argument at stack/frame offset 8, length 4.
15211 Symbol linebuffer is in static storage at address 0x150a18, length 4.
15212 Symbol linelength is in static storage at address 0x150a1c, length 4.
15213 Symbol p is a local variable in register $esi, length 4.
15214 Symbol p1 is a local variable in register $ebx, length 4.
15215 Symbol nline is a local variable in register $edx, length 4.
15216 Symbol repeat is a local variable at frame offset -8, length 4.
15220 This command is especially useful for determining what data to collect
15221 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
15224 @kindex info source
15226 Show information about the current source file---that is, the source file for
15227 the function containing the current point of execution:
15230 the name of the source file, and the directory containing it,
15232 the directory it was compiled in,
15234 its length, in lines,
15236 which programming language it is written in,
15238 whether the executable includes debugging information for that file, and
15239 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
15241 whether the debugging information includes information about
15242 preprocessor macros.
15246 @kindex info sources
15248 Print the names of all source files in your program for which there is
15249 debugging information, organized into two lists: files whose symbols
15250 have already been read, and files whose symbols will be read when needed.
15252 @kindex info functions
15253 @item info functions
15254 Print the names and data types of all defined functions.
15256 @item info functions @var{regexp}
15257 Print the names and data types of all defined functions
15258 whose names contain a match for regular expression @var{regexp}.
15259 Thus, @samp{info fun step} finds all functions whose names
15260 include @code{step}; @samp{info fun ^step} finds those whose names
15261 start with @code{step}. If a function name contains characters
15262 that conflict with the regular expression language (e.g.@:
15263 @samp{operator*()}), they may be quoted with a backslash.
15265 @kindex info variables
15266 @item info variables
15267 Print the names and data types of all variables that are defined
15268 outside of functions (i.e.@: excluding local variables).
15270 @item info variables @var{regexp}
15271 Print the names and data types of all variables (except for local
15272 variables) whose names contain a match for regular expression
15275 @kindex info classes
15276 @cindex Objective-C, classes and selectors
15278 @itemx info classes @var{regexp}
15279 Display all Objective-C classes in your program, or
15280 (with the @var{regexp} argument) all those matching a particular regular
15283 @kindex info selectors
15284 @item info selectors
15285 @itemx info selectors @var{regexp}
15286 Display all Objective-C selectors in your program, or
15287 (with the @var{regexp} argument) all those matching a particular regular
15291 This was never implemented.
15292 @kindex info methods
15294 @itemx info methods @var{regexp}
15295 The @code{info methods} command permits the user to examine all defined
15296 methods within C@t{++} program, or (with the @var{regexp} argument) a
15297 specific set of methods found in the various C@t{++} classes. Many
15298 C@t{++} classes provide a large number of methods. Thus, the output
15299 from the @code{ptype} command can be overwhelming and hard to use. The
15300 @code{info-methods} command filters the methods, printing only those
15301 which match the regular-expression @var{regexp}.
15304 @cindex opaque data types
15305 @kindex set opaque-type-resolution
15306 @item set opaque-type-resolution on
15307 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
15308 declared as a pointer to a @code{struct}, @code{class}, or
15309 @code{union}---for example, @code{struct MyType *}---that is used in one
15310 source file although the full declaration of @code{struct MyType} is in
15311 another source file. The default is on.
15313 A change in the setting of this subcommand will not take effect until
15314 the next time symbols for a file are loaded.
15316 @item set opaque-type-resolution off
15317 Tell @value{GDBN} not to resolve opaque types. In this case, the type
15318 is printed as follows:
15320 @{<no data fields>@}
15323 @kindex show opaque-type-resolution
15324 @item show opaque-type-resolution
15325 Show whether opaque types are resolved or not.
15327 @kindex maint print symbols
15328 @cindex symbol dump
15329 @kindex maint print psymbols
15330 @cindex partial symbol dump
15331 @item maint print symbols @var{filename}
15332 @itemx maint print psymbols @var{filename}
15333 @itemx maint print msymbols @var{filename}
15334 Write a dump of debugging symbol data into the file @var{filename}.
15335 These commands are used to debug the @value{GDBN} symbol-reading code. Only
15336 symbols with debugging data are included. If you use @samp{maint print
15337 symbols}, @value{GDBN} includes all the symbols for which it has already
15338 collected full details: that is, @var{filename} reflects symbols for
15339 only those files whose symbols @value{GDBN} has read. You can use the
15340 command @code{info sources} to find out which files these are. If you
15341 use @samp{maint print psymbols} instead, the dump shows information about
15342 symbols that @value{GDBN} only knows partially---that is, symbols defined in
15343 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
15344 @samp{maint print msymbols} dumps just the minimal symbol information
15345 required for each object file from which @value{GDBN} has read some symbols.
15346 @xref{Files, ,Commands to Specify Files}, for a discussion of how
15347 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
15349 @kindex maint info symtabs
15350 @kindex maint info psymtabs
15351 @cindex listing @value{GDBN}'s internal symbol tables
15352 @cindex symbol tables, listing @value{GDBN}'s internal
15353 @cindex full symbol tables, listing @value{GDBN}'s internal
15354 @cindex partial symbol tables, listing @value{GDBN}'s internal
15355 @item maint info symtabs @r{[} @var{regexp} @r{]}
15356 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
15358 List the @code{struct symtab} or @code{struct partial_symtab}
15359 structures whose names match @var{regexp}. If @var{regexp} is not
15360 given, list them all. The output includes expressions which you can
15361 copy into a @value{GDBN} debugging this one to examine a particular
15362 structure in more detail. For example:
15365 (@value{GDBP}) maint info psymtabs dwarf2read
15366 @{ objfile /home/gnu/build/gdb/gdb
15367 ((struct objfile *) 0x82e69d0)
15368 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
15369 ((struct partial_symtab *) 0x8474b10)
15372 text addresses 0x814d3c8 -- 0x8158074
15373 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
15374 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
15375 dependencies (none)
15378 (@value{GDBP}) maint info symtabs
15382 We see that there is one partial symbol table whose filename contains
15383 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
15384 and we see that @value{GDBN} has not read in any symtabs yet at all.
15385 If we set a breakpoint on a function, that will cause @value{GDBN} to
15386 read the symtab for the compilation unit containing that function:
15389 (@value{GDBP}) break dwarf2_psymtab_to_symtab
15390 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
15392 (@value{GDBP}) maint info symtabs
15393 @{ objfile /home/gnu/build/gdb/gdb
15394 ((struct objfile *) 0x82e69d0)
15395 @{ symtab /home/gnu/src/gdb/dwarf2read.c
15396 ((struct symtab *) 0x86c1f38)
15399 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
15400 linetable ((struct linetable *) 0x8370fa0)
15401 debugformat DWARF 2
15410 @chapter Altering Execution
15412 Once you think you have found an error in your program, you might want to
15413 find out for certain whether correcting the apparent error would lead to
15414 correct results in the rest of the run. You can find the answer by
15415 experiment, using the @value{GDBN} features for altering execution of the
15418 For example, you can store new values into variables or memory
15419 locations, give your program a signal, restart it at a different
15420 address, or even return prematurely from a function.
15423 * Assignment:: Assignment to variables
15424 * Jumping:: Continuing at a different address
15425 * Signaling:: Giving your program a signal
15426 * Returning:: Returning from a function
15427 * Calling:: Calling your program's functions
15428 * Patching:: Patching your program
15432 @section Assignment to Variables
15435 @cindex setting variables
15436 To alter the value of a variable, evaluate an assignment expression.
15437 @xref{Expressions, ,Expressions}. For example,
15444 stores the value 4 into the variable @code{x}, and then prints the
15445 value of the assignment expression (which is 4).
15446 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
15447 information on operators in supported languages.
15449 @kindex set variable
15450 @cindex variables, setting
15451 If you are not interested in seeing the value of the assignment, use the
15452 @code{set} command instead of the @code{print} command. @code{set} is
15453 really the same as @code{print} except that the expression's value is
15454 not printed and is not put in the value history (@pxref{Value History,
15455 ,Value History}). The expression is evaluated only for its effects.
15457 If the beginning of the argument string of the @code{set} command
15458 appears identical to a @code{set} subcommand, use the @code{set
15459 variable} command instead of just @code{set}. This command is identical
15460 to @code{set} except for its lack of subcommands. For example, if your
15461 program has a variable @code{width}, you get an error if you try to set
15462 a new value with just @samp{set width=13}, because @value{GDBN} has the
15463 command @code{set width}:
15466 (@value{GDBP}) whatis width
15468 (@value{GDBP}) p width
15470 (@value{GDBP}) set width=47
15471 Invalid syntax in expression.
15475 The invalid expression, of course, is @samp{=47}. In
15476 order to actually set the program's variable @code{width}, use
15479 (@value{GDBP}) set var width=47
15482 Because the @code{set} command has many subcommands that can conflict
15483 with the names of program variables, it is a good idea to use the
15484 @code{set variable} command instead of just @code{set}. For example, if
15485 your program has a variable @code{g}, you run into problems if you try
15486 to set a new value with just @samp{set g=4}, because @value{GDBN} has
15487 the command @code{set gnutarget}, abbreviated @code{set g}:
15491 (@value{GDBP}) whatis g
15495 (@value{GDBP}) set g=4
15499 The program being debugged has been started already.
15500 Start it from the beginning? (y or n) y
15501 Starting program: /home/smith/cc_progs/a.out
15502 "/home/smith/cc_progs/a.out": can't open to read symbols:
15503 Invalid bfd target.
15504 (@value{GDBP}) show g
15505 The current BFD target is "=4".
15510 The program variable @code{g} did not change, and you silently set the
15511 @code{gnutarget} to an invalid value. In order to set the variable
15515 (@value{GDBP}) set var g=4
15518 @value{GDBN} allows more implicit conversions in assignments than C; you can
15519 freely store an integer value into a pointer variable or vice versa,
15520 and you can convert any structure to any other structure that is the
15521 same length or shorter.
15522 @comment FIXME: how do structs align/pad in these conversions?
15523 @comment /doc@cygnus.com 18dec1990
15525 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
15526 construct to generate a value of specified type at a specified address
15527 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
15528 to memory location @code{0x83040} as an integer (which implies a certain size
15529 and representation in memory), and
15532 set @{int@}0x83040 = 4
15536 stores the value 4 into that memory location.
15539 @section Continuing at a Different Address
15541 Ordinarily, when you continue your program, you do so at the place where
15542 it stopped, with the @code{continue} command. You can instead continue at
15543 an address of your own choosing, with the following commands:
15547 @item jump @var{linespec}
15548 @itemx jump @var{location}
15549 Resume execution at line @var{linespec} or at address given by
15550 @var{location}. Execution stops again immediately if there is a
15551 breakpoint there. @xref{Specify Location}, for a description of the
15552 different forms of @var{linespec} and @var{location}. It is common
15553 practice to use the @code{tbreak} command in conjunction with
15554 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
15556 The @code{jump} command does not change the current stack frame, or
15557 the stack pointer, or the contents of any memory location or any
15558 register other than the program counter. If line @var{linespec} is in
15559 a different function from the one currently executing, the results may
15560 be bizarre if the two functions expect different patterns of arguments or
15561 of local variables. For this reason, the @code{jump} command requests
15562 confirmation if the specified line is not in the function currently
15563 executing. However, even bizarre results are predictable if you are
15564 well acquainted with the machine-language code of your program.
15567 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
15568 On many systems, you can get much the same effect as the @code{jump}
15569 command by storing a new value into the register @code{$pc}. The
15570 difference is that this does not start your program running; it only
15571 changes the address of where it @emph{will} run when you continue. For
15579 makes the next @code{continue} command or stepping command execute at
15580 address @code{0x485}, rather than at the address where your program stopped.
15581 @xref{Continuing and Stepping, ,Continuing and Stepping}.
15583 The most common occasion to use the @code{jump} command is to back
15584 up---perhaps with more breakpoints set---over a portion of a program
15585 that has already executed, in order to examine its execution in more
15590 @section Giving your Program a Signal
15591 @cindex deliver a signal to a program
15595 @item signal @var{signal}
15596 Resume execution where your program stopped, but immediately give it the
15597 signal @var{signal}. @var{signal} can be the name or the number of a
15598 signal. For example, on many systems @code{signal 2} and @code{signal
15599 SIGINT} are both ways of sending an interrupt signal.
15601 Alternatively, if @var{signal} is zero, continue execution without
15602 giving a signal. This is useful when your program stopped on account of
15603 a signal and would ordinary see the signal when resumed with the
15604 @code{continue} command; @samp{signal 0} causes it to resume without a
15607 @code{signal} does not repeat when you press @key{RET} a second time
15608 after executing the command.
15612 Invoking the @code{signal} command is not the same as invoking the
15613 @code{kill} utility from the shell. Sending a signal with @code{kill}
15614 causes @value{GDBN} to decide what to do with the signal depending on
15615 the signal handling tables (@pxref{Signals}). The @code{signal} command
15616 passes the signal directly to your program.
15620 @section Returning from a Function
15623 @cindex returning from a function
15626 @itemx return @var{expression}
15627 You can cancel execution of a function call with the @code{return}
15628 command. If you give an
15629 @var{expression} argument, its value is used as the function's return
15633 When you use @code{return}, @value{GDBN} discards the selected stack frame
15634 (and all frames within it). You can think of this as making the
15635 discarded frame return prematurely. If you wish to specify a value to
15636 be returned, give that value as the argument to @code{return}.
15638 This pops the selected stack frame (@pxref{Selection, ,Selecting a
15639 Frame}), and any other frames inside of it, leaving its caller as the
15640 innermost remaining frame. That frame becomes selected. The
15641 specified value is stored in the registers used for returning values
15644 The @code{return} command does not resume execution; it leaves the
15645 program stopped in the state that would exist if the function had just
15646 returned. In contrast, the @code{finish} command (@pxref{Continuing
15647 and Stepping, ,Continuing and Stepping}) resumes execution until the
15648 selected stack frame returns naturally.
15650 @value{GDBN} needs to know how the @var{expression} argument should be set for
15651 the inferior. The concrete registers assignment depends on the OS ABI and the
15652 type being returned by the selected stack frame. For example it is common for
15653 OS ABI to return floating point values in FPU registers while integer values in
15654 CPU registers. Still some ABIs return even floating point values in CPU
15655 registers. Larger integer widths (such as @code{long long int}) also have
15656 specific placement rules. @value{GDBN} already knows the OS ABI from its
15657 current target so it needs to find out also the type being returned to make the
15658 assignment into the right register(s).
15660 Normally, the selected stack frame has debug info. @value{GDBN} will always
15661 use the debug info instead of the implicit type of @var{expression} when the
15662 debug info is available. For example, if you type @kbd{return -1}, and the
15663 function in the current stack frame is declared to return a @code{long long
15664 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
15665 into a @code{long long int}:
15668 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
15670 (@value{GDBP}) return -1
15671 Make func return now? (y or n) y
15672 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
15673 43 printf ("result=%lld\n", func ());
15677 However, if the selected stack frame does not have a debug info, e.g., if the
15678 function was compiled without debug info, @value{GDBN} has to find out the type
15679 to return from user. Specifying a different type by mistake may set the value
15680 in different inferior registers than the caller code expects. For example,
15681 typing @kbd{return -1} with its implicit type @code{int} would set only a part
15682 of a @code{long long int} result for a debug info less function (on 32-bit
15683 architectures). Therefore the user is required to specify the return type by
15684 an appropriate cast explicitly:
15687 Breakpoint 2, 0x0040050b in func ()
15688 (@value{GDBP}) return -1
15689 Return value type not available for selected stack frame.
15690 Please use an explicit cast of the value to return.
15691 (@value{GDBP}) return (long long int) -1
15692 Make selected stack frame return now? (y or n) y
15693 #0 0x00400526 in main ()
15698 @section Calling Program Functions
15701 @cindex calling functions
15702 @cindex inferior functions, calling
15703 @item print @var{expr}
15704 Evaluate the expression @var{expr} and display the resulting value.
15705 @var{expr} may include calls to functions in the program being
15709 @item call @var{expr}
15710 Evaluate the expression @var{expr} without displaying @code{void}
15713 You can use this variant of the @code{print} command if you want to
15714 execute a function from your program that does not return anything
15715 (a.k.a.@: @dfn{a void function}), but without cluttering the output
15716 with @code{void} returned values that @value{GDBN} will otherwise
15717 print. If the result is not void, it is printed and saved in the
15721 It is possible for the function you call via the @code{print} or
15722 @code{call} command to generate a signal (e.g., if there's a bug in
15723 the function, or if you passed it incorrect arguments). What happens
15724 in that case is controlled by the @code{set unwindonsignal} command.
15726 Similarly, with a C@t{++} program it is possible for the function you
15727 call via the @code{print} or @code{call} command to generate an
15728 exception that is not handled due to the constraints of the dummy
15729 frame. In this case, any exception that is raised in the frame, but has
15730 an out-of-frame exception handler will not be found. GDB builds a
15731 dummy-frame for the inferior function call, and the unwinder cannot
15732 seek for exception handlers outside of this dummy-frame. What happens
15733 in that case is controlled by the
15734 @code{set unwind-on-terminating-exception} command.
15737 @item set unwindonsignal
15738 @kindex set unwindonsignal
15739 @cindex unwind stack in called functions
15740 @cindex call dummy stack unwinding
15741 Set unwinding of the stack if a signal is received while in a function
15742 that @value{GDBN} called in the program being debugged. If set to on,
15743 @value{GDBN} unwinds the stack it created for the call and restores
15744 the context to what it was before the call. If set to off (the
15745 default), @value{GDBN} stops in the frame where the signal was
15748 @item show unwindonsignal
15749 @kindex show unwindonsignal
15750 Show the current setting of stack unwinding in the functions called by
15753 @item set unwind-on-terminating-exception
15754 @kindex set unwind-on-terminating-exception
15755 @cindex unwind stack in called functions with unhandled exceptions
15756 @cindex call dummy stack unwinding on unhandled exception.
15757 Set unwinding of the stack if a C@t{++} exception is raised, but left
15758 unhandled while in a function that @value{GDBN} called in the program being
15759 debugged. If set to on (the default), @value{GDBN} unwinds the stack
15760 it created for the call and restores the context to what it was before
15761 the call. If set to off, @value{GDBN} the exception is delivered to
15762 the default C@t{++} exception handler and the inferior terminated.
15764 @item show unwind-on-terminating-exception
15765 @kindex show unwind-on-terminating-exception
15766 Show the current setting of stack unwinding in the functions called by
15771 @cindex weak alias functions
15772 Sometimes, a function you wish to call is actually a @dfn{weak alias}
15773 for another function. In such case, @value{GDBN} might not pick up
15774 the type information, including the types of the function arguments,
15775 which causes @value{GDBN} to call the inferior function incorrectly.
15776 As a result, the called function will function erroneously and may
15777 even crash. A solution to that is to use the name of the aliased
15781 @section Patching Programs
15783 @cindex patching binaries
15784 @cindex writing into executables
15785 @cindex writing into corefiles
15787 By default, @value{GDBN} opens the file containing your program's
15788 executable code (or the corefile) read-only. This prevents accidental
15789 alterations to machine code; but it also prevents you from intentionally
15790 patching your program's binary.
15792 If you'd like to be able to patch the binary, you can specify that
15793 explicitly with the @code{set write} command. For example, you might
15794 want to turn on internal debugging flags, or even to make emergency
15800 @itemx set write off
15801 If you specify @samp{set write on}, @value{GDBN} opens executable and
15802 core files for both reading and writing; if you specify @kbd{set write
15803 off} (the default), @value{GDBN} opens them read-only.
15805 If you have already loaded a file, you must load it again (using the
15806 @code{exec-file} or @code{core-file} command) after changing @code{set
15807 write}, for your new setting to take effect.
15811 Display whether executable files and core files are opened for writing
15812 as well as reading.
15816 @chapter @value{GDBN} Files
15818 @value{GDBN} needs to know the file name of the program to be debugged,
15819 both in order to read its symbol table and in order to start your
15820 program. To debug a core dump of a previous run, you must also tell
15821 @value{GDBN} the name of the core dump file.
15824 * Files:: Commands to specify files
15825 * Separate Debug Files:: Debugging information in separate files
15826 * Index Files:: Index files speed up GDB
15827 * Symbol Errors:: Errors reading symbol files
15828 * Data Files:: GDB data files
15832 @section Commands to Specify Files
15834 @cindex symbol table
15835 @cindex core dump file
15837 You may want to specify executable and core dump file names. The usual
15838 way to do this is at start-up time, using the arguments to
15839 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
15840 Out of @value{GDBN}}).
15842 Occasionally it is necessary to change to a different file during a
15843 @value{GDBN} session. Or you may run @value{GDBN} and forget to
15844 specify a file you want to use. Or you are debugging a remote target
15845 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
15846 Program}). In these situations the @value{GDBN} commands to specify
15847 new files are useful.
15850 @cindex executable file
15852 @item file @var{filename}
15853 Use @var{filename} as the program to be debugged. It is read for its
15854 symbols and for the contents of pure memory. It is also the program
15855 executed when you use the @code{run} command. If you do not specify a
15856 directory and the file is not found in the @value{GDBN} working directory,
15857 @value{GDBN} uses the environment variable @code{PATH} as a list of
15858 directories to search, just as the shell does when looking for a program
15859 to run. You can change the value of this variable, for both @value{GDBN}
15860 and your program, using the @code{path} command.
15862 @cindex unlinked object files
15863 @cindex patching object files
15864 You can load unlinked object @file{.o} files into @value{GDBN} using
15865 the @code{file} command. You will not be able to ``run'' an object
15866 file, but you can disassemble functions and inspect variables. Also,
15867 if the underlying BFD functionality supports it, you could use
15868 @kbd{gdb -write} to patch object files using this technique. Note
15869 that @value{GDBN} can neither interpret nor modify relocations in this
15870 case, so branches and some initialized variables will appear to go to
15871 the wrong place. But this feature is still handy from time to time.
15874 @code{file} with no argument makes @value{GDBN} discard any information it
15875 has on both executable file and the symbol table.
15878 @item exec-file @r{[} @var{filename} @r{]}
15879 Specify that the program to be run (but not the symbol table) is found
15880 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
15881 if necessary to locate your program. Omitting @var{filename} means to
15882 discard information on the executable file.
15884 @kindex symbol-file
15885 @item symbol-file @r{[} @var{filename} @r{]}
15886 Read symbol table information from file @var{filename}. @code{PATH} is
15887 searched when necessary. Use the @code{file} command to get both symbol
15888 table and program to run from the same file.
15890 @code{symbol-file} with no argument clears out @value{GDBN} information on your
15891 program's symbol table.
15893 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
15894 some breakpoints and auto-display expressions. This is because they may
15895 contain pointers to the internal data recording symbols and data types,
15896 which are part of the old symbol table data being discarded inside
15899 @code{symbol-file} does not repeat if you press @key{RET} again after
15902 When @value{GDBN} is configured for a particular environment, it
15903 understands debugging information in whatever format is the standard
15904 generated for that environment; you may use either a @sc{gnu} compiler, or
15905 other compilers that adhere to the local conventions.
15906 Best results are usually obtained from @sc{gnu} compilers; for example,
15907 using @code{@value{NGCC}} you can generate debugging information for
15910 For most kinds of object files, with the exception of old SVR3 systems
15911 using COFF, the @code{symbol-file} command does not normally read the
15912 symbol table in full right away. Instead, it scans the symbol table
15913 quickly to find which source files and which symbols are present. The
15914 details are read later, one source file at a time, as they are needed.
15916 The purpose of this two-stage reading strategy is to make @value{GDBN}
15917 start up faster. For the most part, it is invisible except for
15918 occasional pauses while the symbol table details for a particular source
15919 file are being read. (The @code{set verbose} command can turn these
15920 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
15921 Warnings and Messages}.)
15923 We have not implemented the two-stage strategy for COFF yet. When the
15924 symbol table is stored in COFF format, @code{symbol-file} reads the
15925 symbol table data in full right away. Note that ``stabs-in-COFF''
15926 still does the two-stage strategy, since the debug info is actually
15930 @cindex reading symbols immediately
15931 @cindex symbols, reading immediately
15932 @item symbol-file @r{[} -readnow @r{]} @var{filename}
15933 @itemx file @r{[} -readnow @r{]} @var{filename}
15934 You can override the @value{GDBN} two-stage strategy for reading symbol
15935 tables by using the @samp{-readnow} option with any of the commands that
15936 load symbol table information, if you want to be sure @value{GDBN} has the
15937 entire symbol table available.
15939 @c FIXME: for now no mention of directories, since this seems to be in
15940 @c flux. 13mar1992 status is that in theory GDB would look either in
15941 @c current dir or in same dir as myprog; but issues like competing
15942 @c GDB's, or clutter in system dirs, mean that in practice right now
15943 @c only current dir is used. FFish says maybe a special GDB hierarchy
15944 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
15948 @item core-file @r{[}@var{filename}@r{]}
15950 Specify the whereabouts of a core dump file to be used as the ``contents
15951 of memory''. Traditionally, core files contain only some parts of the
15952 address space of the process that generated them; @value{GDBN} can access the
15953 executable file itself for other parts.
15955 @code{core-file} with no argument specifies that no core file is
15958 Note that the core file is ignored when your program is actually running
15959 under @value{GDBN}. So, if you have been running your program and you
15960 wish to debug a core file instead, you must kill the subprocess in which
15961 the program is running. To do this, use the @code{kill} command
15962 (@pxref{Kill Process, ,Killing the Child Process}).
15964 @kindex add-symbol-file
15965 @cindex dynamic linking
15966 @item add-symbol-file @var{filename} @var{address}
15967 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
15968 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
15969 The @code{add-symbol-file} command reads additional symbol table
15970 information from the file @var{filename}. You would use this command
15971 when @var{filename} has been dynamically loaded (by some other means)
15972 into the program that is running. @var{address} should be the memory
15973 address at which the file has been loaded; @value{GDBN} cannot figure
15974 this out for itself. You can additionally specify an arbitrary number
15975 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
15976 section name and base address for that section. You can specify any
15977 @var{address} as an expression.
15979 The symbol table of the file @var{filename} is added to the symbol table
15980 originally read with the @code{symbol-file} command. You can use the
15981 @code{add-symbol-file} command any number of times; the new symbol data
15982 thus read keeps adding to the old. To discard all old symbol data
15983 instead, use the @code{symbol-file} command without any arguments.
15985 @cindex relocatable object files, reading symbols from
15986 @cindex object files, relocatable, reading symbols from
15987 @cindex reading symbols from relocatable object files
15988 @cindex symbols, reading from relocatable object files
15989 @cindex @file{.o} files, reading symbols from
15990 Although @var{filename} is typically a shared library file, an
15991 executable file, or some other object file which has been fully
15992 relocated for loading into a process, you can also load symbolic
15993 information from relocatable @file{.o} files, as long as:
15997 the file's symbolic information refers only to linker symbols defined in
15998 that file, not to symbols defined by other object files,
16000 every section the file's symbolic information refers to has actually
16001 been loaded into the inferior, as it appears in the file, and
16003 you can determine the address at which every section was loaded, and
16004 provide these to the @code{add-symbol-file} command.
16008 Some embedded operating systems, like Sun Chorus and VxWorks, can load
16009 relocatable files into an already running program; such systems
16010 typically make the requirements above easy to meet. However, it's
16011 important to recognize that many native systems use complex link
16012 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
16013 assembly, for example) that make the requirements difficult to meet. In
16014 general, one cannot assume that using @code{add-symbol-file} to read a
16015 relocatable object file's symbolic information will have the same effect
16016 as linking the relocatable object file into the program in the normal
16019 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
16021 @kindex add-symbol-file-from-memory
16022 @cindex @code{syscall DSO}
16023 @cindex load symbols from memory
16024 @item add-symbol-file-from-memory @var{address}
16025 Load symbols from the given @var{address} in a dynamically loaded
16026 object file whose image is mapped directly into the inferior's memory.
16027 For example, the Linux kernel maps a @code{syscall DSO} into each
16028 process's address space; this DSO provides kernel-specific code for
16029 some system calls. The argument can be any expression whose
16030 evaluation yields the address of the file's shared object file header.
16031 For this command to work, you must have used @code{symbol-file} or
16032 @code{exec-file} commands in advance.
16034 @kindex add-shared-symbol-files
16036 @item add-shared-symbol-files @var{library-file}
16037 @itemx assf @var{library-file}
16038 The @code{add-shared-symbol-files} command can currently be used only
16039 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
16040 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
16041 @value{GDBN} automatically looks for shared libraries, however if
16042 @value{GDBN} does not find yours, you can invoke
16043 @code{add-shared-symbol-files}. It takes one argument: the shared
16044 library's file name. @code{assf} is a shorthand alias for
16045 @code{add-shared-symbol-files}.
16048 @item section @var{section} @var{addr}
16049 The @code{section} command changes the base address of the named
16050 @var{section} of the exec file to @var{addr}. This can be used if the
16051 exec file does not contain section addresses, (such as in the
16052 @code{a.out} format), or when the addresses specified in the file
16053 itself are wrong. Each section must be changed separately. The
16054 @code{info files} command, described below, lists all the sections and
16058 @kindex info target
16061 @code{info files} and @code{info target} are synonymous; both print the
16062 current target (@pxref{Targets, ,Specifying a Debugging Target}),
16063 including the names of the executable and core dump files currently in
16064 use by @value{GDBN}, and the files from which symbols were loaded. The
16065 command @code{help target} lists all possible targets rather than
16068 @kindex maint info sections
16069 @item maint info sections
16070 Another command that can give you extra information about program sections
16071 is @code{maint info sections}. In addition to the section information
16072 displayed by @code{info files}, this command displays the flags and file
16073 offset of each section in the executable and core dump files. In addition,
16074 @code{maint info sections} provides the following command options (which
16075 may be arbitrarily combined):
16079 Display sections for all loaded object files, including shared libraries.
16080 @item @var{sections}
16081 Display info only for named @var{sections}.
16082 @item @var{section-flags}
16083 Display info only for sections for which @var{section-flags} are true.
16084 The section flags that @value{GDBN} currently knows about are:
16087 Section will have space allocated in the process when loaded.
16088 Set for all sections except those containing debug information.
16090 Section will be loaded from the file into the child process memory.
16091 Set for pre-initialized code and data, clear for @code{.bss} sections.
16093 Section needs to be relocated before loading.
16095 Section cannot be modified by the child process.
16097 Section contains executable code only.
16099 Section contains data only (no executable code).
16101 Section will reside in ROM.
16103 Section contains data for constructor/destructor lists.
16105 Section is not empty.
16107 An instruction to the linker to not output the section.
16108 @item COFF_SHARED_LIBRARY
16109 A notification to the linker that the section contains
16110 COFF shared library information.
16112 Section contains common symbols.
16115 @kindex set trust-readonly-sections
16116 @cindex read-only sections
16117 @item set trust-readonly-sections on
16118 Tell @value{GDBN} that readonly sections in your object file
16119 really are read-only (i.e.@: that their contents will not change).
16120 In that case, @value{GDBN} can fetch values from these sections
16121 out of the object file, rather than from the target program.
16122 For some targets (notably embedded ones), this can be a significant
16123 enhancement to debugging performance.
16125 The default is off.
16127 @item set trust-readonly-sections off
16128 Tell @value{GDBN} not to trust readonly sections. This means that
16129 the contents of the section might change while the program is running,
16130 and must therefore be fetched from the target when needed.
16132 @item show trust-readonly-sections
16133 Show the current setting of trusting readonly sections.
16136 All file-specifying commands allow both absolute and relative file names
16137 as arguments. @value{GDBN} always converts the file name to an absolute file
16138 name and remembers it that way.
16140 @cindex shared libraries
16141 @anchor{Shared Libraries}
16142 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
16143 and IBM RS/6000 AIX shared libraries.
16145 On MS-Windows @value{GDBN} must be linked with the Expat library to support
16146 shared libraries. @xref{Expat}.
16148 @value{GDBN} automatically loads symbol definitions from shared libraries
16149 when you use the @code{run} command, or when you examine a core file.
16150 (Before you issue the @code{run} command, @value{GDBN} does not understand
16151 references to a function in a shared library, however---unless you are
16152 debugging a core file).
16154 On HP-UX, if the program loads a library explicitly, @value{GDBN}
16155 automatically loads the symbols at the time of the @code{shl_load} call.
16157 @c FIXME: some @value{GDBN} release may permit some refs to undef
16158 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
16159 @c FIXME...lib; check this from time to time when updating manual
16161 There are times, however, when you may wish to not automatically load
16162 symbol definitions from shared libraries, such as when they are
16163 particularly large or there are many of them.
16165 To control the automatic loading of shared library symbols, use the
16169 @kindex set auto-solib-add
16170 @item set auto-solib-add @var{mode}
16171 If @var{mode} is @code{on}, symbols from all shared object libraries
16172 will be loaded automatically when the inferior begins execution, you
16173 attach to an independently started inferior, or when the dynamic linker
16174 informs @value{GDBN} that a new library has been loaded. If @var{mode}
16175 is @code{off}, symbols must be loaded manually, using the
16176 @code{sharedlibrary} command. The default value is @code{on}.
16178 @cindex memory used for symbol tables
16179 If your program uses lots of shared libraries with debug info that
16180 takes large amounts of memory, you can decrease the @value{GDBN}
16181 memory footprint by preventing it from automatically loading the
16182 symbols from shared libraries. To that end, type @kbd{set
16183 auto-solib-add off} before running the inferior, then load each
16184 library whose debug symbols you do need with @kbd{sharedlibrary
16185 @var{regexp}}, where @var{regexp} is a regular expression that matches
16186 the libraries whose symbols you want to be loaded.
16188 @kindex show auto-solib-add
16189 @item show auto-solib-add
16190 Display the current autoloading mode.
16193 @cindex load shared library
16194 To explicitly load shared library symbols, use the @code{sharedlibrary}
16198 @kindex info sharedlibrary
16200 @item info share @var{regex}
16201 @itemx info sharedlibrary @var{regex}
16202 Print the names of the shared libraries which are currently loaded
16203 that match @var{regex}. If @var{regex} is omitted then print
16204 all shared libraries that are loaded.
16206 @kindex sharedlibrary
16208 @item sharedlibrary @var{regex}
16209 @itemx share @var{regex}
16210 Load shared object library symbols for files matching a
16211 Unix regular expression.
16212 As with files loaded automatically, it only loads shared libraries
16213 required by your program for a core file or after typing @code{run}. If
16214 @var{regex} is omitted all shared libraries required by your program are
16217 @item nosharedlibrary
16218 @kindex nosharedlibrary
16219 @cindex unload symbols from shared libraries
16220 Unload all shared object library symbols. This discards all symbols
16221 that have been loaded from all shared libraries. Symbols from shared
16222 libraries that were loaded by explicit user requests are not
16226 Sometimes you may wish that @value{GDBN} stops and gives you control
16227 when any of shared library events happen. The best way to do this is
16228 to use @code{catch load} and @code{catch unload} (@pxref{Set
16231 @value{GDBN} also supports the the @code{set stop-on-solib-events}
16232 command for this. This command exists for historical reasons. It is
16233 less useful than setting a catchpoint, because it does not allow for
16234 conditions or commands as a catchpoint does.
16237 @item set stop-on-solib-events
16238 @kindex set stop-on-solib-events
16239 This command controls whether @value{GDBN} should give you control
16240 when the dynamic linker notifies it about some shared library event.
16241 The most common event of interest is loading or unloading of a new
16244 @item show stop-on-solib-events
16245 @kindex show stop-on-solib-events
16246 Show whether @value{GDBN} stops and gives you control when shared
16247 library events happen.
16250 Shared libraries are also supported in many cross or remote debugging
16251 configurations. @value{GDBN} needs to have access to the target's libraries;
16252 this can be accomplished either by providing copies of the libraries
16253 on the host system, or by asking @value{GDBN} to automatically retrieve the
16254 libraries from the target. If copies of the target libraries are
16255 provided, they need to be the same as the target libraries, although the
16256 copies on the target can be stripped as long as the copies on the host are
16259 @cindex where to look for shared libraries
16260 For remote debugging, you need to tell @value{GDBN} where the target
16261 libraries are, so that it can load the correct copies---otherwise, it
16262 may try to load the host's libraries. @value{GDBN} has two variables
16263 to specify the search directories for target libraries.
16266 @cindex prefix for shared library file names
16267 @cindex system root, alternate
16268 @kindex set solib-absolute-prefix
16269 @kindex set sysroot
16270 @item set sysroot @var{path}
16271 Use @var{path} as the system root for the program being debugged. Any
16272 absolute shared library paths will be prefixed with @var{path}; many
16273 runtime loaders store the absolute paths to the shared library in the
16274 target program's memory. If you use @code{set sysroot} to find shared
16275 libraries, they need to be laid out in the same way that they are on
16276 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
16279 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
16280 retrieve the target libraries from the remote system. This is only
16281 supported when using a remote target that supports the @code{remote get}
16282 command (@pxref{File Transfer,,Sending files to a remote system}).
16283 The part of @var{path} following the initial @file{remote:}
16284 (if present) is used as system root prefix on the remote file system.
16285 @footnote{If you want to specify a local system root using a directory
16286 that happens to be named @file{remote:}, you need to use some equivalent
16287 variant of the name like @file{./remote:}.}
16289 For targets with an MS-DOS based filesystem, such as MS-Windows and
16290 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
16291 absolute file name with @var{path}. But first, on Unix hosts,
16292 @value{GDBN} converts all backslash directory separators into forward
16293 slashes, because the backslash is not a directory separator on Unix:
16296 c:\foo\bar.dll @result{} c:/foo/bar.dll
16299 Then, @value{GDBN} attempts prefixing the target file name with
16300 @var{path}, and looks for the resulting file name in the host file
16304 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
16307 If that does not find the shared library, @value{GDBN} tries removing
16308 the @samp{:} character from the drive spec, both for convenience, and,
16309 for the case of the host file system not supporting file names with
16313 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
16316 This makes it possible to have a system root that mirrors a target
16317 with more than one drive. E.g., you may want to setup your local
16318 copies of the target system shared libraries like so (note @samp{c} vs
16322 @file{/path/to/sysroot/c/sys/bin/foo.dll}
16323 @file{/path/to/sysroot/c/sys/bin/bar.dll}
16324 @file{/path/to/sysroot/z/sys/bin/bar.dll}
16328 and point the system root at @file{/path/to/sysroot}, so that
16329 @value{GDBN} can find the correct copies of both
16330 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
16332 If that still does not find the shared library, @value{GDBN} tries
16333 removing the whole drive spec from the target file name:
16336 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
16339 This last lookup makes it possible to not care about the drive name,
16340 if you don't want or need to.
16342 The @code{set solib-absolute-prefix} command is an alias for @code{set
16345 @cindex default system root
16346 @cindex @samp{--with-sysroot}
16347 You can set the default system root by using the configure-time
16348 @samp{--with-sysroot} option. If the system root is inside
16349 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
16350 @samp{--exec-prefix}), then the default system root will be updated
16351 automatically if the installed @value{GDBN} is moved to a new
16354 @kindex show sysroot
16356 Display the current shared library prefix.
16358 @kindex set solib-search-path
16359 @item set solib-search-path @var{path}
16360 If this variable is set, @var{path} is a colon-separated list of
16361 directories to search for shared libraries. @samp{solib-search-path}
16362 is used after @samp{sysroot} fails to locate the library, or if the
16363 path to the library is relative instead of absolute. If you want to
16364 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
16365 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
16366 finding your host's libraries. @samp{sysroot} is preferred; setting
16367 it to a nonexistent directory may interfere with automatic loading
16368 of shared library symbols.
16370 @kindex show solib-search-path
16371 @item show solib-search-path
16372 Display the current shared library search path.
16374 @cindex DOS file-name semantics of file names.
16375 @kindex set target-file-system-kind (unix|dos-based|auto)
16376 @kindex show target-file-system-kind
16377 @item set target-file-system-kind @var{kind}
16378 Set assumed file system kind for target reported file names.
16380 Shared library file names as reported by the target system may not
16381 make sense as is on the system @value{GDBN} is running on. For
16382 example, when remote debugging a target that has MS-DOS based file
16383 system semantics, from a Unix host, the target may be reporting to
16384 @value{GDBN} a list of loaded shared libraries with file names such as
16385 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
16386 drive letters, so the @samp{c:\} prefix is not normally understood as
16387 indicating an absolute file name, and neither is the backslash
16388 normally considered a directory separator character. In that case,
16389 the native file system would interpret this whole absolute file name
16390 as a relative file name with no directory components. This would make
16391 it impossible to point @value{GDBN} at a copy of the remote target's
16392 shared libraries on the host using @code{set sysroot}, and impractical
16393 with @code{set solib-search-path}. Setting
16394 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
16395 to interpret such file names similarly to how the target would, and to
16396 map them to file names valid on @value{GDBN}'s native file system
16397 semantics. The value of @var{kind} can be @code{"auto"}, in addition
16398 to one of the supported file system kinds. In that case, @value{GDBN}
16399 tries to determine the appropriate file system variant based on the
16400 current target's operating system (@pxref{ABI, ,Configuring the
16401 Current ABI}). The supported file system settings are:
16405 Instruct @value{GDBN} to assume the target file system is of Unix
16406 kind. Only file names starting the forward slash (@samp{/}) character
16407 are considered absolute, and the directory separator character is also
16411 Instruct @value{GDBN} to assume the target file system is DOS based.
16412 File names starting with either a forward slash, or a drive letter
16413 followed by a colon (e.g., @samp{c:}), are considered absolute, and
16414 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
16415 considered directory separators.
16418 Instruct @value{GDBN} to use the file system kind associated with the
16419 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
16420 This is the default.
16424 @cindex file name canonicalization
16425 @cindex base name differences
16426 When processing file names provided by the user, @value{GDBN}
16427 frequently needs to compare them to the file names recorded in the
16428 program's debug info. Normally, @value{GDBN} compares just the
16429 @dfn{base names} of the files as strings, which is reasonably fast
16430 even for very large programs. (The base name of a file is the last
16431 portion of its name, after stripping all the leading directories.)
16432 This shortcut in comparison is based upon the assumption that files
16433 cannot have more than one base name. This is usually true, but
16434 references to files that use symlinks or similar filesystem
16435 facilities violate that assumption. If your program records files
16436 using such facilities, or if you provide file names to @value{GDBN}
16437 using symlinks etc., you can set @code{basenames-may-differ} to
16438 @code{true} to instruct @value{GDBN} to completely canonicalize each
16439 pair of file names it needs to compare. This will make file-name
16440 comparisons accurate, but at a price of a significant slowdown.
16443 @item set basenames-may-differ
16444 @kindex set basenames-may-differ
16445 Set whether a source file may have multiple base names.
16447 @item show basenames-may-differ
16448 @kindex show basenames-may-differ
16449 Show whether a source file may have multiple base names.
16452 @node Separate Debug Files
16453 @section Debugging Information in Separate Files
16454 @cindex separate debugging information files
16455 @cindex debugging information in separate files
16456 @cindex @file{.debug} subdirectories
16457 @cindex debugging information directory, global
16458 @cindex global debugging information directories
16459 @cindex build ID, and separate debugging files
16460 @cindex @file{.build-id} directory
16462 @value{GDBN} allows you to put a program's debugging information in a
16463 file separate from the executable itself, in a way that allows
16464 @value{GDBN} to find and load the debugging information automatically.
16465 Since debugging information can be very large---sometimes larger
16466 than the executable code itself---some systems distribute debugging
16467 information for their executables in separate files, which users can
16468 install only when they need to debug a problem.
16470 @value{GDBN} supports two ways of specifying the separate debug info
16475 The executable contains a @dfn{debug link} that specifies the name of
16476 the separate debug info file. The separate debug file's name is
16477 usually @file{@var{executable}.debug}, where @var{executable} is the
16478 name of the corresponding executable file without leading directories
16479 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
16480 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
16481 checksum for the debug file, which @value{GDBN} uses to validate that
16482 the executable and the debug file came from the same build.
16485 The executable contains a @dfn{build ID}, a unique bit string that is
16486 also present in the corresponding debug info file. (This is supported
16487 only on some operating systems, notably those which use the ELF format
16488 for binary files and the @sc{gnu} Binutils.) For more details about
16489 this feature, see the description of the @option{--build-id}
16490 command-line option in @ref{Options, , Command Line Options, ld.info,
16491 The GNU Linker}. The debug info file's name is not specified
16492 explicitly by the build ID, but can be computed from the build ID, see
16496 Depending on the way the debug info file is specified, @value{GDBN}
16497 uses two different methods of looking for the debug file:
16501 For the ``debug link'' method, @value{GDBN} looks up the named file in
16502 the directory of the executable file, then in a subdirectory of that
16503 directory named @file{.debug}, and finally under each one of the global debug
16504 directories, in a subdirectory whose name is identical to the leading
16505 directories of the executable's absolute file name.
16508 For the ``build ID'' method, @value{GDBN} looks in the
16509 @file{.build-id} subdirectory of each one of the global debug directories for
16510 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
16511 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
16512 are the rest of the bit string. (Real build ID strings are 32 or more
16513 hex characters, not 10.)
16516 So, for example, suppose you ask @value{GDBN} to debug
16517 @file{/usr/bin/ls}, which has a debug link that specifies the
16518 file @file{ls.debug}, and a build ID whose value in hex is
16519 @code{abcdef1234}. If the list of the global debug directories includes
16520 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
16521 debug information files, in the indicated order:
16525 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
16527 @file{/usr/bin/ls.debug}
16529 @file{/usr/bin/.debug/ls.debug}
16531 @file{/usr/lib/debug/usr/bin/ls.debug}.
16534 @anchor{debug-file-directory}
16535 Global debugging info directories default to what is set by @value{GDBN}
16536 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
16537 you can also set the global debugging info directories, and view the list
16538 @value{GDBN} is currently using.
16542 @kindex set debug-file-directory
16543 @item set debug-file-directory @var{directories}
16544 Set the directories which @value{GDBN} searches for separate debugging
16545 information files to @var{directory}. Multiple path components can be set
16546 concatenating them by a path separator.
16548 @kindex show debug-file-directory
16549 @item show debug-file-directory
16550 Show the directories @value{GDBN} searches for separate debugging
16555 @cindex @code{.gnu_debuglink} sections
16556 @cindex debug link sections
16557 A debug link is a special section of the executable file named
16558 @code{.gnu_debuglink}. The section must contain:
16562 A filename, with any leading directory components removed, followed by
16565 zero to three bytes of padding, as needed to reach the next four-byte
16566 boundary within the section, and
16568 a four-byte CRC checksum, stored in the same endianness used for the
16569 executable file itself. The checksum is computed on the debugging
16570 information file's full contents by the function given below, passing
16571 zero as the @var{crc} argument.
16574 Any executable file format can carry a debug link, as long as it can
16575 contain a section named @code{.gnu_debuglink} with the contents
16578 @cindex @code{.note.gnu.build-id} sections
16579 @cindex build ID sections
16580 The build ID is a special section in the executable file (and in other
16581 ELF binary files that @value{GDBN} may consider). This section is
16582 often named @code{.note.gnu.build-id}, but that name is not mandatory.
16583 It contains unique identification for the built files---the ID remains
16584 the same across multiple builds of the same build tree. The default
16585 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
16586 content for the build ID string. The same section with an identical
16587 value is present in the original built binary with symbols, in its
16588 stripped variant, and in the separate debugging information file.
16590 The debugging information file itself should be an ordinary
16591 executable, containing a full set of linker symbols, sections, and
16592 debugging information. The sections of the debugging information file
16593 should have the same names, addresses, and sizes as the original file,
16594 but they need not contain any data---much like a @code{.bss} section
16595 in an ordinary executable.
16597 The @sc{gnu} binary utilities (Binutils) package includes the
16598 @samp{objcopy} utility that can produce
16599 the separated executable / debugging information file pairs using the
16600 following commands:
16603 @kbd{objcopy --only-keep-debug foo foo.debug}
16608 These commands remove the debugging
16609 information from the executable file @file{foo} and place it in the file
16610 @file{foo.debug}. You can use the first, second or both methods to link the
16615 The debug link method needs the following additional command to also leave
16616 behind a debug link in @file{foo}:
16619 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
16622 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
16623 a version of the @code{strip} command such that the command @kbd{strip foo -f
16624 foo.debug} has the same functionality as the two @code{objcopy} commands and
16625 the @code{ln -s} command above, together.
16628 Build ID gets embedded into the main executable using @code{ld --build-id} or
16629 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
16630 compatibility fixes for debug files separation are present in @sc{gnu} binary
16631 utilities (Binutils) package since version 2.18.
16636 @cindex CRC algorithm definition
16637 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
16638 IEEE 802.3 using the polynomial:
16640 @c TexInfo requires naked braces for multi-digit exponents for Tex
16641 @c output, but this causes HTML output to barf. HTML has to be set using
16642 @c raw commands. So we end up having to specify this equation in 2
16647 <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>
16648 + <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
16654 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
16655 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
16659 The function is computed byte at a time, taking the least
16660 significant bit of each byte first. The initial pattern
16661 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
16662 the final result is inverted to ensure trailing zeros also affect the
16665 @emph{Note:} This is the same CRC polynomial as used in handling the
16666 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
16667 , @value{GDBN} Remote Serial Protocol}). However in the
16668 case of the Remote Serial Protocol, the CRC is computed @emph{most}
16669 significant bit first, and the result is not inverted, so trailing
16670 zeros have no effect on the CRC value.
16672 To complete the description, we show below the code of the function
16673 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
16674 initially supplied @code{crc} argument means that an initial call to
16675 this function passing in zero will start computing the CRC using
16678 @kindex gnu_debuglink_crc32
16681 gnu_debuglink_crc32 (unsigned long crc,
16682 unsigned char *buf, size_t len)
16684 static const unsigned long crc32_table[256] =
16686 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
16687 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
16688 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
16689 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
16690 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
16691 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
16692 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
16693 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
16694 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
16695 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
16696 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
16697 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
16698 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
16699 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
16700 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
16701 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
16702 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
16703 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
16704 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
16705 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
16706 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
16707 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
16708 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
16709 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
16710 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
16711 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
16712 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
16713 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
16714 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
16715 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
16716 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
16717 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
16718 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
16719 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
16720 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
16721 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
16722 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
16723 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
16724 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
16725 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
16726 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
16727 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
16728 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
16729 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
16730 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
16731 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
16732 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
16733 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
16734 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
16735 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
16736 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
16739 unsigned char *end;
16741 crc = ~crc & 0xffffffff;
16742 for (end = buf + len; buf < end; ++buf)
16743 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
16744 return ~crc & 0xffffffff;
16749 This computation does not apply to the ``build ID'' method.
16753 @section Index Files Speed Up @value{GDBN}
16754 @cindex index files
16755 @cindex @samp{.gdb_index} section
16757 When @value{GDBN} finds a symbol file, it scans the symbols in the
16758 file in order to construct an internal symbol table. This lets most
16759 @value{GDBN} operations work quickly---at the cost of a delay early
16760 on. For large programs, this delay can be quite lengthy, so
16761 @value{GDBN} provides a way to build an index, which speeds up
16764 The index is stored as a section in the symbol file. @value{GDBN} can
16765 write the index to a file, then you can put it into the symbol file
16766 using @command{objcopy}.
16768 To create an index file, use the @code{save gdb-index} command:
16771 @item save gdb-index @var{directory}
16772 @kindex save gdb-index
16773 Create an index file for each symbol file currently known by
16774 @value{GDBN}. Each file is named after its corresponding symbol file,
16775 with @samp{.gdb-index} appended, and is written into the given
16779 Once you have created an index file you can merge it into your symbol
16780 file, here named @file{symfile}, using @command{objcopy}:
16783 $ objcopy --add-section .gdb_index=symfile.gdb-index \
16784 --set-section-flags .gdb_index=readonly symfile symfile
16787 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
16788 sections that have been deprecated. Usually they are deprecated because
16789 they are missing a new feature or have performance issues.
16790 To tell @value{GDBN} to use a deprecated index section anyway
16791 specify @code{set use-deprecated-index-sections on}.
16792 The default is @code{off}.
16793 This can speed up startup, but may result in some functionality being lost.
16794 @xref{Index Section Format}.
16796 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
16797 must be done before gdb reads the file. The following will not work:
16800 $ gdb -ex "set use-deprecated-index-sections on" <program>
16803 Instead you must do, for example,
16806 $ gdb -iex "set use-deprecated-index-sections on" <program>
16809 There are currently some limitation on indices. They only work when
16810 for DWARF debugging information, not stabs. And, they do not
16811 currently work for programs using Ada.
16813 @node Symbol Errors
16814 @section Errors Reading Symbol Files
16816 While reading a symbol file, @value{GDBN} occasionally encounters problems,
16817 such as symbol types it does not recognize, or known bugs in compiler
16818 output. By default, @value{GDBN} does not notify you of such problems, since
16819 they are relatively common and primarily of interest to people
16820 debugging compilers. If you are interested in seeing information
16821 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
16822 only one message about each such type of problem, no matter how many
16823 times the problem occurs; or you can ask @value{GDBN} to print more messages,
16824 to see how many times the problems occur, with the @code{set
16825 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
16828 The messages currently printed, and their meanings, include:
16831 @item inner block not inside outer block in @var{symbol}
16833 The symbol information shows where symbol scopes begin and end
16834 (such as at the start of a function or a block of statements). This
16835 error indicates that an inner scope block is not fully contained
16836 in its outer scope blocks.
16838 @value{GDBN} circumvents the problem by treating the inner block as if it had
16839 the same scope as the outer block. In the error message, @var{symbol}
16840 may be shown as ``@code{(don't know)}'' if the outer block is not a
16843 @item block at @var{address} out of order
16845 The symbol information for symbol scope blocks should occur in
16846 order of increasing addresses. This error indicates that it does not
16849 @value{GDBN} does not circumvent this problem, and has trouble
16850 locating symbols in the source file whose symbols it is reading. (You
16851 can often determine what source file is affected by specifying
16852 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
16855 @item bad block start address patched
16857 The symbol information for a symbol scope block has a start address
16858 smaller than the address of the preceding source line. This is known
16859 to occur in the SunOS 4.1.1 (and earlier) C compiler.
16861 @value{GDBN} circumvents the problem by treating the symbol scope block as
16862 starting on the previous source line.
16864 @item bad string table offset in symbol @var{n}
16867 Symbol number @var{n} contains a pointer into the string table which is
16868 larger than the size of the string table.
16870 @value{GDBN} circumvents the problem by considering the symbol to have the
16871 name @code{foo}, which may cause other problems if many symbols end up
16874 @item unknown symbol type @code{0x@var{nn}}
16876 The symbol information contains new data types that @value{GDBN} does
16877 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
16878 uncomprehended information, in hexadecimal.
16880 @value{GDBN} circumvents the error by ignoring this symbol information.
16881 This usually allows you to debug your program, though certain symbols
16882 are not accessible. If you encounter such a problem and feel like
16883 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
16884 on @code{complain}, then go up to the function @code{read_dbx_symtab}
16885 and examine @code{*bufp} to see the symbol.
16887 @item stub type has NULL name
16889 @value{GDBN} could not find the full definition for a struct or class.
16891 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
16892 The symbol information for a C@t{++} member function is missing some
16893 information that recent versions of the compiler should have output for
16896 @item info mismatch between compiler and debugger
16898 @value{GDBN} could not parse a type specification output by the compiler.
16903 @section GDB Data Files
16905 @cindex prefix for data files
16906 @value{GDBN} will sometimes read an auxiliary data file. These files
16907 are kept in a directory known as the @dfn{data directory}.
16909 You can set the data directory's name, and view the name @value{GDBN}
16910 is currently using.
16913 @kindex set data-directory
16914 @item set data-directory @var{directory}
16915 Set the directory which @value{GDBN} searches for auxiliary data files
16916 to @var{directory}.
16918 @kindex show data-directory
16919 @item show data-directory
16920 Show the directory @value{GDBN} searches for auxiliary data files.
16923 @cindex default data directory
16924 @cindex @samp{--with-gdb-datadir}
16925 You can set the default data directory by using the configure-time
16926 @samp{--with-gdb-datadir} option. If the data directory is inside
16927 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
16928 @samp{--exec-prefix}), then the default data directory will be updated
16929 automatically if the installed @value{GDBN} is moved to a new
16932 The data directory may also be specified with the
16933 @code{--data-directory} command line option.
16934 @xref{Mode Options}.
16937 @chapter Specifying a Debugging Target
16939 @cindex debugging target
16940 A @dfn{target} is the execution environment occupied by your program.
16942 Often, @value{GDBN} runs in the same host environment as your program;
16943 in that case, the debugging target is specified as a side effect when
16944 you use the @code{file} or @code{core} commands. When you need more
16945 flexibility---for example, running @value{GDBN} on a physically separate
16946 host, or controlling a standalone system over a serial port or a
16947 realtime system over a TCP/IP connection---you can use the @code{target}
16948 command to specify one of the target types configured for @value{GDBN}
16949 (@pxref{Target Commands, ,Commands for Managing Targets}).
16951 @cindex target architecture
16952 It is possible to build @value{GDBN} for several different @dfn{target
16953 architectures}. When @value{GDBN} is built like that, you can choose
16954 one of the available architectures with the @kbd{set architecture}
16958 @kindex set architecture
16959 @kindex show architecture
16960 @item set architecture @var{arch}
16961 This command sets the current target architecture to @var{arch}. The
16962 value of @var{arch} can be @code{"auto"}, in addition to one of the
16963 supported architectures.
16965 @item show architecture
16966 Show the current target architecture.
16968 @item set processor
16970 @kindex set processor
16971 @kindex show processor
16972 These are alias commands for, respectively, @code{set architecture}
16973 and @code{show architecture}.
16977 * Active Targets:: Active targets
16978 * Target Commands:: Commands for managing targets
16979 * Byte Order:: Choosing target byte order
16982 @node Active Targets
16983 @section Active Targets
16985 @cindex stacking targets
16986 @cindex active targets
16987 @cindex multiple targets
16989 There are multiple classes of targets such as: processes, executable files or
16990 recording sessions. Core files belong to the process class, making core file
16991 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
16992 on multiple active targets, one in each class. This allows you to (for
16993 example) start a process and inspect its activity, while still having access to
16994 the executable file after the process finishes. Or if you start process
16995 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
16996 presented a virtual layer of the recording target, while the process target
16997 remains stopped at the chronologically last point of the process execution.
16999 Use the @code{core-file} and @code{exec-file} commands to select a new core
17000 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
17001 specify as a target a process that is already running, use the @code{attach}
17002 command (@pxref{Attach, ,Debugging an Already-running Process}).
17004 @node Target Commands
17005 @section Commands for Managing Targets
17008 @item target @var{type} @var{parameters}
17009 Connects the @value{GDBN} host environment to a target machine or
17010 process. A target is typically a protocol for talking to debugging
17011 facilities. You use the argument @var{type} to specify the type or
17012 protocol of the target machine.
17014 Further @var{parameters} are interpreted by the target protocol, but
17015 typically include things like device names or host names to connect
17016 with, process numbers, and baud rates.
17018 The @code{target} command does not repeat if you press @key{RET} again
17019 after executing the command.
17021 @kindex help target
17023 Displays the names of all targets available. To display targets
17024 currently selected, use either @code{info target} or @code{info files}
17025 (@pxref{Files, ,Commands to Specify Files}).
17027 @item help target @var{name}
17028 Describe a particular target, including any parameters necessary to
17031 @kindex set gnutarget
17032 @item set gnutarget @var{args}
17033 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
17034 knows whether it is reading an @dfn{executable},
17035 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
17036 with the @code{set gnutarget} command. Unlike most @code{target} commands,
17037 with @code{gnutarget} the @code{target} refers to a program, not a machine.
17040 @emph{Warning:} To specify a file format with @code{set gnutarget},
17041 you must know the actual BFD name.
17045 @xref{Files, , Commands to Specify Files}.
17047 @kindex show gnutarget
17048 @item show gnutarget
17049 Use the @code{show gnutarget} command to display what file format
17050 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
17051 @value{GDBN} will determine the file format for each file automatically,
17052 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
17055 @cindex common targets
17056 Here are some common targets (available, or not, depending on the GDB
17061 @item target exec @var{program}
17062 @cindex executable file target
17063 An executable file. @samp{target exec @var{program}} is the same as
17064 @samp{exec-file @var{program}}.
17066 @item target core @var{filename}
17067 @cindex core dump file target
17068 A core dump file. @samp{target core @var{filename}} is the same as
17069 @samp{core-file @var{filename}}.
17071 @item target remote @var{medium}
17072 @cindex remote target
17073 A remote system connected to @value{GDBN} via a serial line or network
17074 connection. This command tells @value{GDBN} to use its own remote
17075 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
17077 For example, if you have a board connected to @file{/dev/ttya} on the
17078 machine running @value{GDBN}, you could say:
17081 target remote /dev/ttya
17084 @code{target remote} supports the @code{load} command. This is only
17085 useful if you have some other way of getting the stub to the target
17086 system, and you can put it somewhere in memory where it won't get
17087 clobbered by the download.
17089 @item target sim @r{[}@var{simargs}@r{]} @dots{}
17090 @cindex built-in simulator target
17091 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
17099 works; however, you cannot assume that a specific memory map, device
17100 drivers, or even basic I/O is available, although some simulators do
17101 provide these. For info about any processor-specific simulator details,
17102 see the appropriate section in @ref{Embedded Processors, ,Embedded
17107 Some configurations may include these targets as well:
17111 @item target nrom @var{dev}
17112 @cindex NetROM ROM emulator target
17113 NetROM ROM emulator. This target only supports downloading.
17117 Different targets are available on different configurations of @value{GDBN};
17118 your configuration may have more or fewer targets.
17120 Many remote targets require you to download the executable's code once
17121 you've successfully established a connection. You may wish to control
17122 various aspects of this process.
17127 @kindex set hash@r{, for remote monitors}
17128 @cindex hash mark while downloading
17129 This command controls whether a hash mark @samp{#} is displayed while
17130 downloading a file to the remote monitor. If on, a hash mark is
17131 displayed after each S-record is successfully downloaded to the
17135 @kindex show hash@r{, for remote monitors}
17136 Show the current status of displaying the hash mark.
17138 @item set debug monitor
17139 @kindex set debug monitor
17140 @cindex display remote monitor communications
17141 Enable or disable display of communications messages between
17142 @value{GDBN} and the remote monitor.
17144 @item show debug monitor
17145 @kindex show debug monitor
17146 Show the current status of displaying communications between
17147 @value{GDBN} and the remote monitor.
17152 @kindex load @var{filename}
17153 @item load @var{filename}
17155 Depending on what remote debugging facilities are configured into
17156 @value{GDBN}, the @code{load} command may be available. Where it exists, it
17157 is meant to make @var{filename} (an executable) available for debugging
17158 on the remote system---by downloading, or dynamic linking, for example.
17159 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
17160 the @code{add-symbol-file} command.
17162 If your @value{GDBN} does not have a @code{load} command, attempting to
17163 execute it gets the error message ``@code{You can't do that when your
17164 target is @dots{}}''
17166 The file is loaded at whatever address is specified in the executable.
17167 For some object file formats, you can specify the load address when you
17168 link the program; for other formats, like a.out, the object file format
17169 specifies a fixed address.
17170 @c FIXME! This would be a good place for an xref to the GNU linker doc.
17172 Depending on the remote side capabilities, @value{GDBN} may be able to
17173 load programs into flash memory.
17175 @code{load} does not repeat if you press @key{RET} again after using it.
17179 @section Choosing Target Byte Order
17181 @cindex choosing target byte order
17182 @cindex target byte order
17184 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
17185 offer the ability to run either big-endian or little-endian byte
17186 orders. Usually the executable or symbol will include a bit to
17187 designate the endian-ness, and you will not need to worry about
17188 which to use. However, you may still find it useful to adjust
17189 @value{GDBN}'s idea of processor endian-ness manually.
17193 @item set endian big
17194 Instruct @value{GDBN} to assume the target is big-endian.
17196 @item set endian little
17197 Instruct @value{GDBN} to assume the target is little-endian.
17199 @item set endian auto
17200 Instruct @value{GDBN} to use the byte order associated with the
17204 Display @value{GDBN}'s current idea of the target byte order.
17208 Note that these commands merely adjust interpretation of symbolic
17209 data on the host, and that they have absolutely no effect on the
17213 @node Remote Debugging
17214 @chapter Debugging Remote Programs
17215 @cindex remote debugging
17217 If you are trying to debug a program running on a machine that cannot run
17218 @value{GDBN} in the usual way, it is often useful to use remote debugging.
17219 For example, you might use remote debugging on an operating system kernel,
17220 or on a small system which does not have a general purpose operating system
17221 powerful enough to run a full-featured debugger.
17223 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
17224 to make this work with particular debugging targets. In addition,
17225 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
17226 but not specific to any particular target system) which you can use if you
17227 write the remote stubs---the code that runs on the remote system to
17228 communicate with @value{GDBN}.
17230 Other remote targets may be available in your
17231 configuration of @value{GDBN}; use @code{help target} to list them.
17234 * Connecting:: Connecting to a remote target
17235 * File Transfer:: Sending files to a remote system
17236 * Server:: Using the gdbserver program
17237 * Remote Configuration:: Remote configuration
17238 * Remote Stub:: Implementing a remote stub
17242 @section Connecting to a Remote Target
17244 On the @value{GDBN} host machine, you will need an unstripped copy of
17245 your program, since @value{GDBN} needs symbol and debugging information.
17246 Start up @value{GDBN} as usual, using the name of the local copy of your
17247 program as the first argument.
17249 @cindex @code{target remote}
17250 @value{GDBN} can communicate with the target over a serial line, or
17251 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
17252 each case, @value{GDBN} uses the same protocol for debugging your
17253 program; only the medium carrying the debugging packets varies. The
17254 @code{target remote} command establishes a connection to the target.
17255 Its arguments indicate which medium to use:
17259 @item target remote @var{serial-device}
17260 @cindex serial line, @code{target remote}
17261 Use @var{serial-device} to communicate with the target. For example,
17262 to use a serial line connected to the device named @file{/dev/ttyb}:
17265 target remote /dev/ttyb
17268 If you're using a serial line, you may want to give @value{GDBN} the
17269 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
17270 (@pxref{Remote Configuration, set remotebaud}) before the
17271 @code{target} command.
17273 @item target remote @code{@var{host}:@var{port}}
17274 @itemx target remote @code{tcp:@var{host}:@var{port}}
17275 @cindex @acronym{TCP} port, @code{target remote}
17276 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
17277 The @var{host} may be either a host name or a numeric @acronym{IP}
17278 address; @var{port} must be a decimal number. The @var{host} could be
17279 the target machine itself, if it is directly connected to the net, or
17280 it might be a terminal server which in turn has a serial line to the
17283 For example, to connect to port 2828 on a terminal server named
17287 target remote manyfarms:2828
17290 If your remote target is actually running on the same machine as your
17291 debugger session (e.g.@: a simulator for your target running on the
17292 same host), you can omit the hostname. For example, to connect to
17293 port 1234 on your local machine:
17296 target remote :1234
17300 Note that the colon is still required here.
17302 @item target remote @code{udp:@var{host}:@var{port}}
17303 @cindex @acronym{UDP} port, @code{target remote}
17304 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
17305 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
17308 target remote udp:manyfarms:2828
17311 When using a @acronym{UDP} connection for remote debugging, you should
17312 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
17313 can silently drop packets on busy or unreliable networks, which will
17314 cause havoc with your debugging session.
17316 @item target remote | @var{command}
17317 @cindex pipe, @code{target remote} to
17318 Run @var{command} in the background and communicate with it using a
17319 pipe. The @var{command} is a shell command, to be parsed and expanded
17320 by the system's command shell, @code{/bin/sh}; it should expect remote
17321 protocol packets on its standard input, and send replies on its
17322 standard output. You could use this to run a stand-alone simulator
17323 that speaks the remote debugging protocol, to make net connections
17324 using programs like @code{ssh}, or for other similar tricks.
17326 If @var{command} closes its standard output (perhaps by exiting),
17327 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
17328 program has already exited, this will have no effect.)
17332 Once the connection has been established, you can use all the usual
17333 commands to examine and change data. The remote program is already
17334 running; you can use @kbd{step} and @kbd{continue}, and you do not
17335 need to use @kbd{run}.
17337 @cindex interrupting remote programs
17338 @cindex remote programs, interrupting
17339 Whenever @value{GDBN} is waiting for the remote program, if you type the
17340 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
17341 program. This may or may not succeed, depending in part on the hardware
17342 and the serial drivers the remote system uses. If you type the
17343 interrupt character once again, @value{GDBN} displays this prompt:
17346 Interrupted while waiting for the program.
17347 Give up (and stop debugging it)? (y or n)
17350 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
17351 (If you decide you want to try again later, you can use @samp{target
17352 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
17353 goes back to waiting.
17356 @kindex detach (remote)
17358 When you have finished debugging the remote program, you can use the
17359 @code{detach} command to release it from @value{GDBN} control.
17360 Detaching from the target normally resumes its execution, but the results
17361 will depend on your particular remote stub. After the @code{detach}
17362 command, @value{GDBN} is free to connect to another target.
17366 The @code{disconnect} command behaves like @code{detach}, except that
17367 the target is generally not resumed. It will wait for @value{GDBN}
17368 (this instance or another one) to connect and continue debugging. After
17369 the @code{disconnect} command, @value{GDBN} is again free to connect to
17372 @cindex send command to remote monitor
17373 @cindex extend @value{GDBN} for remote targets
17374 @cindex add new commands for external monitor
17376 @item monitor @var{cmd}
17377 This command allows you to send arbitrary commands directly to the
17378 remote monitor. Since @value{GDBN} doesn't care about the commands it
17379 sends like this, this command is the way to extend @value{GDBN}---you
17380 can add new commands that only the external monitor will understand
17384 @node File Transfer
17385 @section Sending files to a remote system
17386 @cindex remote target, file transfer
17387 @cindex file transfer
17388 @cindex sending files to remote systems
17390 Some remote targets offer the ability to transfer files over the same
17391 connection used to communicate with @value{GDBN}. This is convenient
17392 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
17393 running @code{gdbserver} over a network interface. For other targets,
17394 e.g.@: embedded devices with only a single serial port, this may be
17395 the only way to upload or download files.
17397 Not all remote targets support these commands.
17401 @item remote put @var{hostfile} @var{targetfile}
17402 Copy file @var{hostfile} from the host system (the machine running
17403 @value{GDBN}) to @var{targetfile} on the target system.
17406 @item remote get @var{targetfile} @var{hostfile}
17407 Copy file @var{targetfile} from the target system to @var{hostfile}
17408 on the host system.
17410 @kindex remote delete
17411 @item remote delete @var{targetfile}
17412 Delete @var{targetfile} from the target system.
17417 @section Using the @code{gdbserver} Program
17420 @cindex remote connection without stubs
17421 @code{gdbserver} is a control program for Unix-like systems, which
17422 allows you to connect your program with a remote @value{GDBN} via
17423 @code{target remote}---but without linking in the usual debugging stub.
17425 @code{gdbserver} is not a complete replacement for the debugging stubs,
17426 because it requires essentially the same operating-system facilities
17427 that @value{GDBN} itself does. In fact, a system that can run
17428 @code{gdbserver} to connect to a remote @value{GDBN} could also run
17429 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
17430 because it is a much smaller program than @value{GDBN} itself. It is
17431 also easier to port than all of @value{GDBN}, so you may be able to get
17432 started more quickly on a new system by using @code{gdbserver}.
17433 Finally, if you develop code for real-time systems, you may find that
17434 the tradeoffs involved in real-time operation make it more convenient to
17435 do as much development work as possible on another system, for example
17436 by cross-compiling. You can use @code{gdbserver} to make a similar
17437 choice for debugging.
17439 @value{GDBN} and @code{gdbserver} communicate via either a serial line
17440 or a TCP connection, using the standard @value{GDBN} remote serial
17444 @emph{Warning:} @code{gdbserver} does not have any built-in security.
17445 Do not run @code{gdbserver} connected to any public network; a
17446 @value{GDBN} connection to @code{gdbserver} provides access to the
17447 target system with the same privileges as the user running
17451 @subsection Running @code{gdbserver}
17452 @cindex arguments, to @code{gdbserver}
17453 @cindex @code{gdbserver}, command-line arguments
17455 Run @code{gdbserver} on the target system. You need a copy of the
17456 program you want to debug, including any libraries it requires.
17457 @code{gdbserver} does not need your program's symbol table, so you can
17458 strip the program if necessary to save space. @value{GDBN} on the host
17459 system does all the symbol handling.
17461 To use the server, you must tell it how to communicate with @value{GDBN};
17462 the name of your program; and the arguments for your program. The usual
17466 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
17469 @var{comm} is either a device name (to use a serial line), or a TCP
17470 hostname and portnumber, or @code{-} or @code{stdio} to use
17471 stdin/stdout of @code{gdbserver}.
17472 For example, to debug Emacs with the argument
17473 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
17477 target> gdbserver /dev/com1 emacs foo.txt
17480 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
17483 To use a TCP connection instead of a serial line:
17486 target> gdbserver host:2345 emacs foo.txt
17489 The only difference from the previous example is the first argument,
17490 specifying that you are communicating with the host @value{GDBN} via
17491 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
17492 expect a TCP connection from machine @samp{host} to local TCP port 2345.
17493 (Currently, the @samp{host} part is ignored.) You can choose any number
17494 you want for the port number as long as it does not conflict with any
17495 TCP ports already in use on the target system (for example, @code{23} is
17496 reserved for @code{telnet}).@footnote{If you choose a port number that
17497 conflicts with another service, @code{gdbserver} prints an error message
17498 and exits.} You must use the same port number with the host @value{GDBN}
17499 @code{target remote} command.
17501 The @code{stdio} connection is useful when starting @code{gdbserver}
17505 (gdb) target remote | ssh -T hostname gdbserver - hello
17508 The @samp{-T} option to ssh is provided because we don't need a remote pty,
17509 and we don't want escape-character handling. Ssh does this by default when
17510 a command is provided, the flag is provided to make it explicit.
17511 You could elide it if you want to.
17513 Programs started with stdio-connected gdbserver have @file{/dev/null} for
17514 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
17515 display through a pipe connected to gdbserver.
17516 Both @code{stdout} and @code{stderr} use the same pipe.
17518 @subsubsection Attaching to a Running Program
17519 @cindex attach to a program, @code{gdbserver}
17520 @cindex @option{--attach}, @code{gdbserver} option
17522 On some targets, @code{gdbserver} can also attach to running programs.
17523 This is accomplished via the @code{--attach} argument. The syntax is:
17526 target> gdbserver --attach @var{comm} @var{pid}
17529 @var{pid} is the process ID of a currently running process. It isn't necessary
17530 to point @code{gdbserver} at a binary for the running process.
17533 You can debug processes by name instead of process ID if your target has the
17534 @code{pidof} utility:
17537 target> gdbserver --attach @var{comm} `pidof @var{program}`
17540 In case more than one copy of @var{program} is running, or @var{program}
17541 has multiple threads, most versions of @code{pidof} support the
17542 @code{-s} option to only return the first process ID.
17544 @subsubsection Multi-Process Mode for @code{gdbserver}
17545 @cindex @code{gdbserver}, multiple processes
17546 @cindex multiple processes with @code{gdbserver}
17548 When you connect to @code{gdbserver} using @code{target remote},
17549 @code{gdbserver} debugs the specified program only once. When the
17550 program exits, or you detach from it, @value{GDBN} closes the connection
17551 and @code{gdbserver} exits.
17553 If you connect using @kbd{target extended-remote}, @code{gdbserver}
17554 enters multi-process mode. When the debugged program exits, or you
17555 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
17556 though no program is running. The @code{run} and @code{attach}
17557 commands instruct @code{gdbserver} to run or attach to a new program.
17558 The @code{run} command uses @code{set remote exec-file} (@pxref{set
17559 remote exec-file}) to select the program to run. Command line
17560 arguments are supported, except for wildcard expansion and I/O
17561 redirection (@pxref{Arguments}).
17563 @cindex @option{--multi}, @code{gdbserver} option
17564 To start @code{gdbserver} without supplying an initial command to run
17565 or process ID to attach, use the @option{--multi} command line option.
17566 Then you can connect using @kbd{target extended-remote} and start
17567 the program you want to debug.
17569 In multi-process mode @code{gdbserver} does not automatically exit unless you
17570 use the option @option{--once}. You can terminate it by using
17571 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
17572 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
17573 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
17574 @option{--multi} option to @code{gdbserver} has no influence on that.
17576 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
17578 This section applies only when @code{gdbserver} is run to listen on a TCP port.
17580 @code{gdbserver} normally terminates after all of its debugged processes have
17581 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
17582 extended-remote}, @code{gdbserver} stays running even with no processes left.
17583 @value{GDBN} normally terminates the spawned debugged process on its exit,
17584 which normally also terminates @code{gdbserver} in the @kbd{target remote}
17585 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
17586 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
17587 stays running even in the @kbd{target remote} mode.
17589 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
17590 Such reconnecting is useful for features like @ref{disconnected tracing}. For
17591 completeness, at most one @value{GDBN} can be connected at a time.
17593 @cindex @option{--once}, @code{gdbserver} option
17594 By default, @code{gdbserver} keeps the listening TCP port open, so that
17595 additional connections are possible. However, if you start @code{gdbserver}
17596 with the @option{--once} option, it will stop listening for any further
17597 connection attempts after connecting to the first @value{GDBN} session. This
17598 means no further connections to @code{gdbserver} will be possible after the
17599 first one. It also means @code{gdbserver} will terminate after the first
17600 connection with remote @value{GDBN} has closed, even for unexpectedly closed
17601 connections and even in the @kbd{target extended-remote} mode. The
17602 @option{--once} option allows reusing the same port number for connecting to
17603 multiple instances of @code{gdbserver} running on the same host, since each
17604 instance closes its port after the first connection.
17606 @subsubsection Other Command-Line Arguments for @code{gdbserver}
17608 @cindex @option{--debug}, @code{gdbserver} option
17609 The @option{--debug} option tells @code{gdbserver} to display extra
17610 status information about the debugging process.
17611 @cindex @option{--remote-debug}, @code{gdbserver} option
17612 The @option{--remote-debug} option tells @code{gdbserver} to display
17613 remote protocol debug output. These options are intended for
17614 @code{gdbserver} development and for bug reports to the developers.
17616 @cindex @option{--wrapper}, @code{gdbserver} option
17617 The @option{--wrapper} option specifies a wrapper to launch programs
17618 for debugging. The option should be followed by the name of the
17619 wrapper, then any command-line arguments to pass to the wrapper, then
17620 @kbd{--} indicating the end of the wrapper arguments.
17622 @code{gdbserver} runs the specified wrapper program with a combined
17623 command line including the wrapper arguments, then the name of the
17624 program to debug, then any arguments to the program. The wrapper
17625 runs until it executes your program, and then @value{GDBN} gains control.
17627 You can use any program that eventually calls @code{execve} with
17628 its arguments as a wrapper. Several standard Unix utilities do
17629 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
17630 with @code{exec "$@@"} will also work.
17632 For example, you can use @code{env} to pass an environment variable to
17633 the debugged program, without setting the variable in @code{gdbserver}'s
17637 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
17640 @subsection Connecting to @code{gdbserver}
17642 Run @value{GDBN} on the host system.
17644 First make sure you have the necessary symbol files. Load symbols for
17645 your application using the @code{file} command before you connect. Use
17646 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
17647 was compiled with the correct sysroot using @code{--with-sysroot}).
17649 The symbol file and target libraries must exactly match the executable
17650 and libraries on the target, with one exception: the files on the host
17651 system should not be stripped, even if the files on the target system
17652 are. Mismatched or missing files will lead to confusing results
17653 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
17654 files may also prevent @code{gdbserver} from debugging multi-threaded
17657 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
17658 For TCP connections, you must start up @code{gdbserver} prior to using
17659 the @code{target remote} command. Otherwise you may get an error whose
17660 text depends on the host system, but which usually looks something like
17661 @samp{Connection refused}. Don't use the @code{load}
17662 command in @value{GDBN} when using @code{gdbserver}, since the program is
17663 already on the target.
17665 @subsection Monitor Commands for @code{gdbserver}
17666 @cindex monitor commands, for @code{gdbserver}
17667 @anchor{Monitor Commands for gdbserver}
17669 During a @value{GDBN} session using @code{gdbserver}, you can use the
17670 @code{monitor} command to send special requests to @code{gdbserver}.
17671 Here are the available commands.
17675 List the available monitor commands.
17677 @item monitor set debug 0
17678 @itemx monitor set debug 1
17679 Disable or enable general debugging messages.
17681 @item monitor set remote-debug 0
17682 @itemx monitor set remote-debug 1
17683 Disable or enable specific debugging messages associated with the remote
17684 protocol (@pxref{Remote Protocol}).
17686 @item monitor set libthread-db-search-path [PATH]
17687 @cindex gdbserver, search path for @code{libthread_db}
17688 When this command is issued, @var{path} is a colon-separated list of
17689 directories to search for @code{libthread_db} (@pxref{Threads,,set
17690 libthread-db-search-path}). If you omit @var{path},
17691 @samp{libthread-db-search-path} will be reset to its default value.
17693 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
17694 not supported in @code{gdbserver}.
17697 Tell gdbserver to exit immediately. This command should be followed by
17698 @code{disconnect} to close the debugging session. @code{gdbserver} will
17699 detach from any attached processes and kill any processes it created.
17700 Use @code{monitor exit} to terminate @code{gdbserver} at the end
17701 of a multi-process mode debug session.
17705 @subsection Tracepoints support in @code{gdbserver}
17706 @cindex tracepoints support in @code{gdbserver}
17708 On some targets, @code{gdbserver} supports tracepoints, fast
17709 tracepoints and static tracepoints.
17711 For fast or static tracepoints to work, a special library called the
17712 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
17713 This library is built and distributed as an integral part of
17714 @code{gdbserver}. In addition, support for static tracepoints
17715 requires building the in-process agent library with static tracepoints
17716 support. At present, the UST (LTTng Userspace Tracer,
17717 @url{http://lttng.org/ust}) tracing engine is supported. This support
17718 is automatically available if UST development headers are found in the
17719 standard include path when @code{gdbserver} is built, or if
17720 @code{gdbserver} was explicitly configured using @option{--with-ust}
17721 to point at such headers. You can explicitly disable the support
17722 using @option{--with-ust=no}.
17724 There are several ways to load the in-process agent in your program:
17727 @item Specifying it as dependency at link time
17729 You can link your program dynamically with the in-process agent
17730 library. On most systems, this is accomplished by adding
17731 @code{-linproctrace} to the link command.
17733 @item Using the system's preloading mechanisms
17735 You can force loading the in-process agent at startup time by using
17736 your system's support for preloading shared libraries. Many Unixes
17737 support the concept of preloading user defined libraries. In most
17738 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
17739 in the environment. See also the description of @code{gdbserver}'s
17740 @option{--wrapper} command line option.
17742 @item Using @value{GDBN} to force loading the agent at run time
17744 On some systems, you can force the inferior to load a shared library,
17745 by calling a dynamic loader function in the inferior that takes care
17746 of dynamically looking up and loading a shared library. On most Unix
17747 systems, the function is @code{dlopen}. You'll use the @code{call}
17748 command for that. For example:
17751 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
17754 Note that on most Unix systems, for the @code{dlopen} function to be
17755 available, the program needs to be linked with @code{-ldl}.
17758 On systems that have a userspace dynamic loader, like most Unix
17759 systems, when you connect to @code{gdbserver} using @code{target
17760 remote}, you'll find that the program is stopped at the dynamic
17761 loader's entry point, and no shared library has been loaded in the
17762 program's address space yet, including the in-process agent. In that
17763 case, before being able to use any of the fast or static tracepoints
17764 features, you need to let the loader run and load the shared
17765 libraries. The simplest way to do that is to run the program to the
17766 main procedure. E.g., if debugging a C or C@t{++} program, start
17767 @code{gdbserver} like so:
17770 $ gdbserver :9999 myprogram
17773 Start GDB and connect to @code{gdbserver} like so, and run to main:
17777 (@value{GDBP}) target remote myhost:9999
17778 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
17779 (@value{GDBP}) b main
17780 (@value{GDBP}) continue
17783 The in-process tracing agent library should now be loaded into the
17784 process; you can confirm it with the @code{info sharedlibrary}
17785 command, which will list @file{libinproctrace.so} as loaded in the
17786 process. You are now ready to install fast tracepoints, list static
17787 tracepoint markers, probe static tracepoints markers, and start
17790 @node Remote Configuration
17791 @section Remote Configuration
17794 @kindex show remote
17795 This section documents the configuration options available when
17796 debugging remote programs. For the options related to the File I/O
17797 extensions of the remote protocol, see @ref{system,
17798 system-call-allowed}.
17801 @item set remoteaddresssize @var{bits}
17802 @cindex address size for remote targets
17803 @cindex bits in remote address
17804 Set the maximum size of address in a memory packet to the specified
17805 number of bits. @value{GDBN} will mask off the address bits above
17806 that number, when it passes addresses to the remote target. The
17807 default value is the number of bits in the target's address.
17809 @item show remoteaddresssize
17810 Show the current value of remote address size in bits.
17812 @item set remotebaud @var{n}
17813 @cindex baud rate for remote targets
17814 Set the baud rate for the remote serial I/O to @var{n} baud. The
17815 value is used to set the speed of the serial port used for debugging
17818 @item show remotebaud
17819 Show the current speed of the remote connection.
17821 @item set remotebreak
17822 @cindex interrupt remote programs
17823 @cindex BREAK signal instead of Ctrl-C
17824 @anchor{set remotebreak}
17825 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
17826 when you type @kbd{Ctrl-c} to interrupt the program running
17827 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
17828 character instead. The default is off, since most remote systems
17829 expect to see @samp{Ctrl-C} as the interrupt signal.
17831 @item show remotebreak
17832 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
17833 interrupt the remote program.
17835 @item set remoteflow on
17836 @itemx set remoteflow off
17837 @kindex set remoteflow
17838 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
17839 on the serial port used to communicate to the remote target.
17841 @item show remoteflow
17842 @kindex show remoteflow
17843 Show the current setting of hardware flow control.
17845 @item set remotelogbase @var{base}
17846 Set the base (a.k.a.@: radix) of logging serial protocol
17847 communications to @var{base}. Supported values of @var{base} are:
17848 @code{ascii}, @code{octal}, and @code{hex}. The default is
17851 @item show remotelogbase
17852 Show the current setting of the radix for logging remote serial
17855 @item set remotelogfile @var{file}
17856 @cindex record serial communications on file
17857 Record remote serial communications on the named @var{file}. The
17858 default is not to record at all.
17860 @item show remotelogfile.
17861 Show the current setting of the file name on which to record the
17862 serial communications.
17864 @item set remotetimeout @var{num}
17865 @cindex timeout for serial communications
17866 @cindex remote timeout
17867 Set the timeout limit to wait for the remote target to respond to
17868 @var{num} seconds. The default is 2 seconds.
17870 @item show remotetimeout
17871 Show the current number of seconds to wait for the remote target
17874 @cindex limit hardware breakpoints and watchpoints
17875 @cindex remote target, limit break- and watchpoints
17876 @anchor{set remote hardware-watchpoint-limit}
17877 @anchor{set remote hardware-breakpoint-limit}
17878 @item set remote hardware-watchpoint-limit @var{limit}
17879 @itemx set remote hardware-breakpoint-limit @var{limit}
17880 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
17881 watchpoints. A limit of -1, the default, is treated as unlimited.
17883 @cindex limit hardware watchpoints length
17884 @cindex remote target, limit watchpoints length
17885 @anchor{set remote hardware-watchpoint-length-limit}
17886 @item set remote hardware-watchpoint-length-limit @var{limit}
17887 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
17888 a remote hardware watchpoint. A limit of -1, the default, is treated
17891 @item show remote hardware-watchpoint-length-limit
17892 Show the current limit (in bytes) of the maximum length of
17893 a remote hardware watchpoint.
17895 @item set remote exec-file @var{filename}
17896 @itemx show remote exec-file
17897 @anchor{set remote exec-file}
17898 @cindex executable file, for remote target
17899 Select the file used for @code{run} with @code{target
17900 extended-remote}. This should be set to a filename valid on the
17901 target system. If it is not set, the target will use a default
17902 filename (e.g.@: the last program run).
17904 @item set remote interrupt-sequence
17905 @cindex interrupt remote programs
17906 @cindex select Ctrl-C, BREAK or BREAK-g
17907 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
17908 @samp{BREAK-g} as the
17909 sequence to the remote target in order to interrupt the execution.
17910 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
17911 is high level of serial line for some certain time.
17912 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
17913 It is @code{BREAK} signal followed by character @code{g}.
17915 @item show interrupt-sequence
17916 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
17917 is sent by @value{GDBN} to interrupt the remote program.
17918 @code{BREAK-g} is BREAK signal followed by @code{g} and
17919 also known as Magic SysRq g.
17921 @item set remote interrupt-on-connect
17922 @cindex send interrupt-sequence on start
17923 Specify whether interrupt-sequence is sent to remote target when
17924 @value{GDBN} connects to it. This is mostly needed when you debug
17925 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
17926 which is known as Magic SysRq g in order to connect @value{GDBN}.
17928 @item show interrupt-on-connect
17929 Show whether interrupt-sequence is sent
17930 to remote target when @value{GDBN} connects to it.
17934 @item set tcp auto-retry on
17935 @cindex auto-retry, for remote TCP target
17936 Enable auto-retry for remote TCP connections. This is useful if the remote
17937 debugging agent is launched in parallel with @value{GDBN}; there is a race
17938 condition because the agent may not become ready to accept the connection
17939 before @value{GDBN} attempts to connect. When auto-retry is
17940 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
17941 to establish the connection using the timeout specified by
17942 @code{set tcp connect-timeout}.
17944 @item set tcp auto-retry off
17945 Do not auto-retry failed TCP connections.
17947 @item show tcp auto-retry
17948 Show the current auto-retry setting.
17950 @item set tcp connect-timeout @var{seconds}
17951 @cindex connection timeout, for remote TCP target
17952 @cindex timeout, for remote target connection
17953 Set the timeout for establishing a TCP connection to the remote target to
17954 @var{seconds}. The timeout affects both polling to retry failed connections
17955 (enabled by @code{set tcp auto-retry on}) and waiting for connections
17956 that are merely slow to complete, and represents an approximate cumulative
17959 @item show tcp connect-timeout
17960 Show the current connection timeout setting.
17963 @cindex remote packets, enabling and disabling
17964 The @value{GDBN} remote protocol autodetects the packets supported by
17965 your debugging stub. If you need to override the autodetection, you
17966 can use these commands to enable or disable individual packets. Each
17967 packet can be set to @samp{on} (the remote target supports this
17968 packet), @samp{off} (the remote target does not support this packet),
17969 or @samp{auto} (detect remote target support for this packet). They
17970 all default to @samp{auto}. For more information about each packet,
17971 see @ref{Remote Protocol}.
17973 During normal use, you should not have to use any of these commands.
17974 If you do, that may be a bug in your remote debugging stub, or a bug
17975 in @value{GDBN}. You may want to report the problem to the
17976 @value{GDBN} developers.
17978 For each packet @var{name}, the command to enable or disable the
17979 packet is @code{set remote @var{name}-packet}. The available settings
17982 @multitable @columnfractions 0.28 0.32 0.25
17985 @tab Related Features
17987 @item @code{fetch-register}
17989 @tab @code{info registers}
17991 @item @code{set-register}
17995 @item @code{binary-download}
17997 @tab @code{load}, @code{set}
17999 @item @code{read-aux-vector}
18000 @tab @code{qXfer:auxv:read}
18001 @tab @code{info auxv}
18003 @item @code{symbol-lookup}
18004 @tab @code{qSymbol}
18005 @tab Detecting multiple threads
18007 @item @code{attach}
18008 @tab @code{vAttach}
18011 @item @code{verbose-resume}
18013 @tab Stepping or resuming multiple threads
18019 @item @code{software-breakpoint}
18023 @item @code{hardware-breakpoint}
18027 @item @code{write-watchpoint}
18031 @item @code{read-watchpoint}
18035 @item @code{access-watchpoint}
18039 @item @code{target-features}
18040 @tab @code{qXfer:features:read}
18041 @tab @code{set architecture}
18043 @item @code{library-info}
18044 @tab @code{qXfer:libraries:read}
18045 @tab @code{info sharedlibrary}
18047 @item @code{memory-map}
18048 @tab @code{qXfer:memory-map:read}
18049 @tab @code{info mem}
18051 @item @code{read-sdata-object}
18052 @tab @code{qXfer:sdata:read}
18053 @tab @code{print $_sdata}
18055 @item @code{read-spu-object}
18056 @tab @code{qXfer:spu:read}
18057 @tab @code{info spu}
18059 @item @code{write-spu-object}
18060 @tab @code{qXfer:spu:write}
18061 @tab @code{info spu}
18063 @item @code{read-siginfo-object}
18064 @tab @code{qXfer:siginfo:read}
18065 @tab @code{print $_siginfo}
18067 @item @code{write-siginfo-object}
18068 @tab @code{qXfer:siginfo:write}
18069 @tab @code{set $_siginfo}
18071 @item @code{threads}
18072 @tab @code{qXfer:threads:read}
18073 @tab @code{info threads}
18075 @item @code{get-thread-local-@*storage-address}
18076 @tab @code{qGetTLSAddr}
18077 @tab Displaying @code{__thread} variables
18079 @item @code{get-thread-information-block-address}
18080 @tab @code{qGetTIBAddr}
18081 @tab Display MS-Windows Thread Information Block.
18083 @item @code{search-memory}
18084 @tab @code{qSearch:memory}
18087 @item @code{supported-packets}
18088 @tab @code{qSupported}
18089 @tab Remote communications parameters
18091 @item @code{pass-signals}
18092 @tab @code{QPassSignals}
18093 @tab @code{handle @var{signal}}
18095 @item @code{program-signals}
18096 @tab @code{QProgramSignals}
18097 @tab @code{handle @var{signal}}
18099 @item @code{hostio-close-packet}
18100 @tab @code{vFile:close}
18101 @tab @code{remote get}, @code{remote put}
18103 @item @code{hostio-open-packet}
18104 @tab @code{vFile:open}
18105 @tab @code{remote get}, @code{remote put}
18107 @item @code{hostio-pread-packet}
18108 @tab @code{vFile:pread}
18109 @tab @code{remote get}, @code{remote put}
18111 @item @code{hostio-pwrite-packet}
18112 @tab @code{vFile:pwrite}
18113 @tab @code{remote get}, @code{remote put}
18115 @item @code{hostio-unlink-packet}
18116 @tab @code{vFile:unlink}
18117 @tab @code{remote delete}
18119 @item @code{hostio-readlink-packet}
18120 @tab @code{vFile:readlink}
18123 @item @code{noack-packet}
18124 @tab @code{QStartNoAckMode}
18125 @tab Packet acknowledgment
18127 @item @code{osdata}
18128 @tab @code{qXfer:osdata:read}
18129 @tab @code{info os}
18131 @item @code{query-attached}
18132 @tab @code{qAttached}
18133 @tab Querying remote process attach state.
18135 @item @code{traceframe-info}
18136 @tab @code{qXfer:traceframe-info:read}
18137 @tab Traceframe info
18139 @item @code{install-in-trace}
18140 @tab @code{InstallInTrace}
18141 @tab Install tracepoint in tracing
18143 @item @code{disable-randomization}
18144 @tab @code{QDisableRandomization}
18145 @tab @code{set disable-randomization}
18147 @item @code{conditional-breakpoints-packet}
18148 @tab @code{Z0 and Z1}
18149 @tab @code{Support for target-side breakpoint condition evaluation}
18153 @section Implementing a Remote Stub
18155 @cindex debugging stub, example
18156 @cindex remote stub, example
18157 @cindex stub example, remote debugging
18158 The stub files provided with @value{GDBN} implement the target side of the
18159 communication protocol, and the @value{GDBN} side is implemented in the
18160 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
18161 these subroutines to communicate, and ignore the details. (If you're
18162 implementing your own stub file, you can still ignore the details: start
18163 with one of the existing stub files. @file{sparc-stub.c} is the best
18164 organized, and therefore the easiest to read.)
18166 @cindex remote serial debugging, overview
18167 To debug a program running on another machine (the debugging
18168 @dfn{target} machine), you must first arrange for all the usual
18169 prerequisites for the program to run by itself. For example, for a C
18174 A startup routine to set up the C runtime environment; these usually
18175 have a name like @file{crt0}. The startup routine may be supplied by
18176 your hardware supplier, or you may have to write your own.
18179 A C subroutine library to support your program's
18180 subroutine calls, notably managing input and output.
18183 A way of getting your program to the other machine---for example, a
18184 download program. These are often supplied by the hardware
18185 manufacturer, but you may have to write your own from hardware
18189 The next step is to arrange for your program to use a serial port to
18190 communicate with the machine where @value{GDBN} is running (the @dfn{host}
18191 machine). In general terms, the scheme looks like this:
18195 @value{GDBN} already understands how to use this protocol; when everything
18196 else is set up, you can simply use the @samp{target remote} command
18197 (@pxref{Targets,,Specifying a Debugging Target}).
18199 @item On the target,
18200 you must link with your program a few special-purpose subroutines that
18201 implement the @value{GDBN} remote serial protocol. The file containing these
18202 subroutines is called a @dfn{debugging stub}.
18204 On certain remote targets, you can use an auxiliary program
18205 @code{gdbserver} instead of linking a stub into your program.
18206 @xref{Server,,Using the @code{gdbserver} Program}, for details.
18209 The debugging stub is specific to the architecture of the remote
18210 machine; for example, use @file{sparc-stub.c} to debug programs on
18213 @cindex remote serial stub list
18214 These working remote stubs are distributed with @value{GDBN}:
18219 @cindex @file{i386-stub.c}
18222 For Intel 386 and compatible architectures.
18225 @cindex @file{m68k-stub.c}
18226 @cindex Motorola 680x0
18228 For Motorola 680x0 architectures.
18231 @cindex @file{sh-stub.c}
18234 For Renesas SH architectures.
18237 @cindex @file{sparc-stub.c}
18239 For @sc{sparc} architectures.
18241 @item sparcl-stub.c
18242 @cindex @file{sparcl-stub.c}
18245 For Fujitsu @sc{sparclite} architectures.
18249 The @file{README} file in the @value{GDBN} distribution may list other
18250 recently added stubs.
18253 * Stub Contents:: What the stub can do for you
18254 * Bootstrapping:: What you must do for the stub
18255 * Debug Session:: Putting it all together
18258 @node Stub Contents
18259 @subsection What the Stub Can Do for You
18261 @cindex remote serial stub
18262 The debugging stub for your architecture supplies these three
18266 @item set_debug_traps
18267 @findex set_debug_traps
18268 @cindex remote serial stub, initialization
18269 This routine arranges for @code{handle_exception} to run when your
18270 program stops. You must call this subroutine explicitly in your
18271 program's startup code.
18273 @item handle_exception
18274 @findex handle_exception
18275 @cindex remote serial stub, main routine
18276 This is the central workhorse, but your program never calls it
18277 explicitly---the setup code arranges for @code{handle_exception} to
18278 run when a trap is triggered.
18280 @code{handle_exception} takes control when your program stops during
18281 execution (for example, on a breakpoint), and mediates communications
18282 with @value{GDBN} on the host machine. This is where the communications
18283 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
18284 representative on the target machine. It begins by sending summary
18285 information on the state of your program, then continues to execute,
18286 retrieving and transmitting any information @value{GDBN} needs, until you
18287 execute a @value{GDBN} command that makes your program resume; at that point,
18288 @code{handle_exception} returns control to your own code on the target
18292 @cindex @code{breakpoint} subroutine, remote
18293 Use this auxiliary subroutine to make your program contain a
18294 breakpoint. Depending on the particular situation, this may be the only
18295 way for @value{GDBN} to get control. For instance, if your target
18296 machine has some sort of interrupt button, you won't need to call this;
18297 pressing the interrupt button transfers control to
18298 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
18299 simply receiving characters on the serial port may also trigger a trap;
18300 again, in that situation, you don't need to call @code{breakpoint} from
18301 your own program---simply running @samp{target remote} from the host
18302 @value{GDBN} session gets control.
18304 Call @code{breakpoint} if none of these is true, or if you simply want
18305 to make certain your program stops at a predetermined point for the
18306 start of your debugging session.
18309 @node Bootstrapping
18310 @subsection What You Must Do for the Stub
18312 @cindex remote stub, support routines
18313 The debugging stubs that come with @value{GDBN} are set up for a particular
18314 chip architecture, but they have no information about the rest of your
18315 debugging target machine.
18317 First of all you need to tell the stub how to communicate with the
18321 @item int getDebugChar()
18322 @findex getDebugChar
18323 Write this subroutine to read a single character from the serial port.
18324 It may be identical to @code{getchar} for your target system; a
18325 different name is used to allow you to distinguish the two if you wish.
18327 @item void putDebugChar(int)
18328 @findex putDebugChar
18329 Write this subroutine to write a single character to the serial port.
18330 It may be identical to @code{putchar} for your target system; a
18331 different name is used to allow you to distinguish the two if you wish.
18334 @cindex control C, and remote debugging
18335 @cindex interrupting remote targets
18336 If you want @value{GDBN} to be able to stop your program while it is
18337 running, you need to use an interrupt-driven serial driver, and arrange
18338 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
18339 character). That is the character which @value{GDBN} uses to tell the
18340 remote system to stop.
18342 Getting the debugging target to return the proper status to @value{GDBN}
18343 probably requires changes to the standard stub; one quick and dirty way
18344 is to just execute a breakpoint instruction (the ``dirty'' part is that
18345 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
18347 Other routines you need to supply are:
18350 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
18351 @findex exceptionHandler
18352 Write this function to install @var{exception_address} in the exception
18353 handling tables. You need to do this because the stub does not have any
18354 way of knowing what the exception handling tables on your target system
18355 are like (for example, the processor's table might be in @sc{rom},
18356 containing entries which point to a table in @sc{ram}).
18357 @var{exception_number} is the exception number which should be changed;
18358 its meaning is architecture-dependent (for example, different numbers
18359 might represent divide by zero, misaligned access, etc). When this
18360 exception occurs, control should be transferred directly to
18361 @var{exception_address}, and the processor state (stack, registers,
18362 and so on) should be just as it is when a processor exception occurs. So if
18363 you want to use a jump instruction to reach @var{exception_address}, it
18364 should be a simple jump, not a jump to subroutine.
18366 For the 386, @var{exception_address} should be installed as an interrupt
18367 gate so that interrupts are masked while the handler runs. The gate
18368 should be at privilege level 0 (the most privileged level). The
18369 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
18370 help from @code{exceptionHandler}.
18372 @item void flush_i_cache()
18373 @findex flush_i_cache
18374 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
18375 instruction cache, if any, on your target machine. If there is no
18376 instruction cache, this subroutine may be a no-op.
18378 On target machines that have instruction caches, @value{GDBN} requires this
18379 function to make certain that the state of your program is stable.
18383 You must also make sure this library routine is available:
18386 @item void *memset(void *, int, int)
18388 This is the standard library function @code{memset} that sets an area of
18389 memory to a known value. If you have one of the free versions of
18390 @code{libc.a}, @code{memset} can be found there; otherwise, you must
18391 either obtain it from your hardware manufacturer, or write your own.
18394 If you do not use the GNU C compiler, you may need other standard
18395 library subroutines as well; this varies from one stub to another,
18396 but in general the stubs are likely to use any of the common library
18397 subroutines which @code{@value{NGCC}} generates as inline code.
18400 @node Debug Session
18401 @subsection Putting it All Together
18403 @cindex remote serial debugging summary
18404 In summary, when your program is ready to debug, you must follow these
18409 Make sure you have defined the supporting low-level routines
18410 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
18412 @code{getDebugChar}, @code{putDebugChar},
18413 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
18417 Insert these lines in your program's startup code, before the main
18418 procedure is called:
18425 On some machines, when a breakpoint trap is raised, the hardware
18426 automatically makes the PC point to the instruction after the
18427 breakpoint. If your machine doesn't do that, you may need to adjust
18428 @code{handle_exception} to arrange for it to return to the instruction
18429 after the breakpoint on this first invocation, so that your program
18430 doesn't keep hitting the initial breakpoint instead of making
18434 For the 680x0 stub only, you need to provide a variable called
18435 @code{exceptionHook}. Normally you just use:
18438 void (*exceptionHook)() = 0;
18442 but if before calling @code{set_debug_traps}, you set it to point to a
18443 function in your program, that function is called when
18444 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
18445 error). The function indicated by @code{exceptionHook} is called with
18446 one parameter: an @code{int} which is the exception number.
18449 Compile and link together: your program, the @value{GDBN} debugging stub for
18450 your target architecture, and the supporting subroutines.
18453 Make sure you have a serial connection between your target machine and
18454 the @value{GDBN} host, and identify the serial port on the host.
18457 @c The "remote" target now provides a `load' command, so we should
18458 @c document that. FIXME.
18459 Download your program to your target machine (or get it there by
18460 whatever means the manufacturer provides), and start it.
18463 Start @value{GDBN} on the host, and connect to the target
18464 (@pxref{Connecting,,Connecting to a Remote Target}).
18468 @node Configurations
18469 @chapter Configuration-Specific Information
18471 While nearly all @value{GDBN} commands are available for all native and
18472 cross versions of the debugger, there are some exceptions. This chapter
18473 describes things that are only available in certain configurations.
18475 There are three major categories of configurations: native
18476 configurations, where the host and target are the same, embedded
18477 operating system configurations, which are usually the same for several
18478 different processor architectures, and bare embedded processors, which
18479 are quite different from each other.
18484 * Embedded Processors::
18491 This section describes details specific to particular native
18496 * BSD libkvm Interface:: Debugging BSD kernel memory images
18497 * SVR4 Process Information:: SVR4 process information
18498 * DJGPP Native:: Features specific to the DJGPP port
18499 * Cygwin Native:: Features specific to the Cygwin port
18500 * Hurd Native:: Features specific to @sc{gnu} Hurd
18501 * Darwin:: Features specific to Darwin
18507 On HP-UX systems, if you refer to a function or variable name that
18508 begins with a dollar sign, @value{GDBN} searches for a user or system
18509 name first, before it searches for a convenience variable.
18512 @node BSD libkvm Interface
18513 @subsection BSD libkvm Interface
18516 @cindex kernel memory image
18517 @cindex kernel crash dump
18519 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
18520 interface that provides a uniform interface for accessing kernel virtual
18521 memory images, including live systems and crash dumps. @value{GDBN}
18522 uses this interface to allow you to debug live kernels and kernel crash
18523 dumps on many native BSD configurations. This is implemented as a
18524 special @code{kvm} debugging target. For debugging a live system, load
18525 the currently running kernel into @value{GDBN} and connect to the
18529 (@value{GDBP}) @b{target kvm}
18532 For debugging crash dumps, provide the file name of the crash dump as an
18536 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
18539 Once connected to the @code{kvm} target, the following commands are
18545 Set current context from the @dfn{Process Control Block} (PCB) address.
18548 Set current context from proc address. This command isn't available on
18549 modern FreeBSD systems.
18552 @node SVR4 Process Information
18553 @subsection SVR4 Process Information
18555 @cindex examine process image
18556 @cindex process info via @file{/proc}
18558 Many versions of SVR4 and compatible systems provide a facility called
18559 @samp{/proc} that can be used to examine the image of a running
18560 process using file-system subroutines. If @value{GDBN} is configured
18561 for an operating system with this facility, the command @code{info
18562 proc} is available to report information about the process running
18563 your program, or about any process running on your system. @code{info
18564 proc} works only on SVR4 systems that include the @code{procfs} code.
18565 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
18566 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
18572 @itemx info proc @var{process-id}
18573 Summarize available information about any running process. If a
18574 process ID is specified by @var{process-id}, display information about
18575 that process; otherwise display information about the program being
18576 debugged. The summary includes the debugged process ID, the command
18577 line used to invoke it, its current working directory, and its
18578 executable file's absolute file name.
18580 On some systems, @var{process-id} can be of the form
18581 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
18582 within a process. If the optional @var{pid} part is missing, it means
18583 a thread from the process being debugged (the leading @samp{/} still
18584 needs to be present, or else @value{GDBN} will interpret the number as
18585 a process ID rather than a thread ID).
18587 @item info proc mappings
18588 @cindex memory address space mappings
18589 Report the memory address space ranges accessible in the program, with
18590 information on whether the process has read, write, or execute access
18591 rights to each range. On @sc{gnu}/Linux systems, each memory range
18592 includes the object file which is mapped to that range, instead of the
18593 memory access rights to that range.
18595 @item info proc stat
18596 @itemx info proc status
18597 @cindex process detailed status information
18598 These subcommands are specific to @sc{gnu}/Linux systems. They show
18599 the process-related information, including the user ID and group ID;
18600 how many threads are there in the process; its virtual memory usage;
18601 the signals that are pending, blocked, and ignored; its TTY; its
18602 consumption of system and user time; its stack size; its @samp{nice}
18603 value; etc. For more information, see the @samp{proc} man page
18604 (type @kbd{man 5 proc} from your shell prompt).
18606 @item info proc all
18607 Show all the information about the process described under all of the
18608 above @code{info proc} subcommands.
18611 @comment These sub-options of 'info proc' were not included when
18612 @comment procfs.c was re-written. Keep their descriptions around
18613 @comment against the day when someone finds the time to put them back in.
18614 @kindex info proc times
18615 @item info proc times
18616 Starting time, user CPU time, and system CPU time for your program and
18619 @kindex info proc id
18621 Report on the process IDs related to your program: its own process ID,
18622 the ID of its parent, the process group ID, and the session ID.
18625 @item set procfs-trace
18626 @kindex set procfs-trace
18627 @cindex @code{procfs} API calls
18628 This command enables and disables tracing of @code{procfs} API calls.
18630 @item show procfs-trace
18631 @kindex show procfs-trace
18632 Show the current state of @code{procfs} API call tracing.
18634 @item set procfs-file @var{file}
18635 @kindex set procfs-file
18636 Tell @value{GDBN} to write @code{procfs} API trace to the named
18637 @var{file}. @value{GDBN} appends the trace info to the previous
18638 contents of the file. The default is to display the trace on the
18641 @item show procfs-file
18642 @kindex show procfs-file
18643 Show the file to which @code{procfs} API trace is written.
18645 @item proc-trace-entry
18646 @itemx proc-trace-exit
18647 @itemx proc-untrace-entry
18648 @itemx proc-untrace-exit
18649 @kindex proc-trace-entry
18650 @kindex proc-trace-exit
18651 @kindex proc-untrace-entry
18652 @kindex proc-untrace-exit
18653 These commands enable and disable tracing of entries into and exits
18654 from the @code{syscall} interface.
18657 @kindex info pidlist
18658 @cindex process list, QNX Neutrino
18659 For QNX Neutrino only, this command displays the list of all the
18660 processes and all the threads within each process.
18663 @kindex info meminfo
18664 @cindex mapinfo list, QNX Neutrino
18665 For QNX Neutrino only, this command displays the list of all mapinfos.
18669 @subsection Features for Debugging @sc{djgpp} Programs
18670 @cindex @sc{djgpp} debugging
18671 @cindex native @sc{djgpp} debugging
18672 @cindex MS-DOS-specific commands
18675 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
18676 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
18677 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
18678 top of real-mode DOS systems and their emulations.
18680 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
18681 defines a few commands specific to the @sc{djgpp} port. This
18682 subsection describes those commands.
18687 This is a prefix of @sc{djgpp}-specific commands which print
18688 information about the target system and important OS structures.
18691 @cindex MS-DOS system info
18692 @cindex free memory information (MS-DOS)
18693 @item info dos sysinfo
18694 This command displays assorted information about the underlying
18695 platform: the CPU type and features, the OS version and flavor, the
18696 DPMI version, and the available conventional and DPMI memory.
18701 @cindex segment descriptor tables
18702 @cindex descriptor tables display
18704 @itemx info dos ldt
18705 @itemx info dos idt
18706 These 3 commands display entries from, respectively, Global, Local,
18707 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
18708 tables are data structures which store a descriptor for each segment
18709 that is currently in use. The segment's selector is an index into a
18710 descriptor table; the table entry for that index holds the
18711 descriptor's base address and limit, and its attributes and access
18714 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
18715 segment (used for both data and the stack), and a DOS segment (which
18716 allows access to DOS/BIOS data structures and absolute addresses in
18717 conventional memory). However, the DPMI host will usually define
18718 additional segments in order to support the DPMI environment.
18720 @cindex garbled pointers
18721 These commands allow to display entries from the descriptor tables.
18722 Without an argument, all entries from the specified table are
18723 displayed. An argument, which should be an integer expression, means
18724 display a single entry whose index is given by the argument. For
18725 example, here's a convenient way to display information about the
18726 debugged program's data segment:
18729 @exdent @code{(@value{GDBP}) info dos ldt $ds}
18730 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
18734 This comes in handy when you want to see whether a pointer is outside
18735 the data segment's limit (i.e.@: @dfn{garbled}).
18737 @cindex page tables display (MS-DOS)
18739 @itemx info dos pte
18740 These two commands display entries from, respectively, the Page
18741 Directory and the Page Tables. Page Directories and Page Tables are
18742 data structures which control how virtual memory addresses are mapped
18743 into physical addresses. A Page Table includes an entry for every
18744 page of memory that is mapped into the program's address space; there
18745 may be several Page Tables, each one holding up to 4096 entries. A
18746 Page Directory has up to 4096 entries, one each for every Page Table
18747 that is currently in use.
18749 Without an argument, @kbd{info dos pde} displays the entire Page
18750 Directory, and @kbd{info dos pte} displays all the entries in all of
18751 the Page Tables. An argument, an integer expression, given to the
18752 @kbd{info dos pde} command means display only that entry from the Page
18753 Directory table. An argument given to the @kbd{info dos pte} command
18754 means display entries from a single Page Table, the one pointed to by
18755 the specified entry in the Page Directory.
18757 @cindex direct memory access (DMA) on MS-DOS
18758 These commands are useful when your program uses @dfn{DMA} (Direct
18759 Memory Access), which needs physical addresses to program the DMA
18762 These commands are supported only with some DPMI servers.
18764 @cindex physical address from linear address
18765 @item info dos address-pte @var{addr}
18766 This command displays the Page Table entry for a specified linear
18767 address. The argument @var{addr} is a linear address which should
18768 already have the appropriate segment's base address added to it,
18769 because this command accepts addresses which may belong to @emph{any}
18770 segment. For example, here's how to display the Page Table entry for
18771 the page where a variable @code{i} is stored:
18774 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
18775 @exdent @code{Page Table entry for address 0x11a00d30:}
18776 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
18780 This says that @code{i} is stored at offset @code{0xd30} from the page
18781 whose physical base address is @code{0x02698000}, and shows all the
18782 attributes of that page.
18784 Note that you must cast the addresses of variables to a @code{char *},
18785 since otherwise the value of @code{__djgpp_base_address}, the base
18786 address of all variables and functions in a @sc{djgpp} program, will
18787 be added using the rules of C pointer arithmetics: if @code{i} is
18788 declared an @code{int}, @value{GDBN} will add 4 times the value of
18789 @code{__djgpp_base_address} to the address of @code{i}.
18791 Here's another example, it displays the Page Table entry for the
18795 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
18796 @exdent @code{Page Table entry for address 0x29110:}
18797 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
18801 (The @code{+ 3} offset is because the transfer buffer's address is the
18802 3rd member of the @code{_go32_info_block} structure.) The output
18803 clearly shows that this DPMI server maps the addresses in conventional
18804 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
18805 linear (@code{0x29110}) addresses are identical.
18807 This command is supported only with some DPMI servers.
18810 @cindex DOS serial data link, remote debugging
18811 In addition to native debugging, the DJGPP port supports remote
18812 debugging via a serial data link. The following commands are specific
18813 to remote serial debugging in the DJGPP port of @value{GDBN}.
18816 @kindex set com1base
18817 @kindex set com1irq
18818 @kindex set com2base
18819 @kindex set com2irq
18820 @kindex set com3base
18821 @kindex set com3irq
18822 @kindex set com4base
18823 @kindex set com4irq
18824 @item set com1base @var{addr}
18825 This command sets the base I/O port address of the @file{COM1} serial
18828 @item set com1irq @var{irq}
18829 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
18830 for the @file{COM1} serial port.
18832 There are similar commands @samp{set com2base}, @samp{set com3irq},
18833 etc.@: for setting the port address and the @code{IRQ} lines for the
18836 @kindex show com1base
18837 @kindex show com1irq
18838 @kindex show com2base
18839 @kindex show com2irq
18840 @kindex show com3base
18841 @kindex show com3irq
18842 @kindex show com4base
18843 @kindex show com4irq
18844 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
18845 display the current settings of the base address and the @code{IRQ}
18846 lines used by the COM ports.
18849 @kindex info serial
18850 @cindex DOS serial port status
18851 This command prints the status of the 4 DOS serial ports. For each
18852 port, it prints whether it's active or not, its I/O base address and
18853 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
18854 counts of various errors encountered so far.
18858 @node Cygwin Native
18859 @subsection Features for Debugging MS Windows PE Executables
18860 @cindex MS Windows debugging
18861 @cindex native Cygwin debugging
18862 @cindex Cygwin-specific commands
18864 @value{GDBN} supports native debugging of MS Windows programs, including
18865 DLLs with and without symbolic debugging information.
18867 @cindex Ctrl-BREAK, MS-Windows
18868 @cindex interrupt debuggee on MS-Windows
18869 MS-Windows programs that call @code{SetConsoleMode} to switch off the
18870 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
18871 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
18872 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
18873 sequence, which can be used to interrupt the debuggee even if it
18876 There are various additional Cygwin-specific commands, described in
18877 this section. Working with DLLs that have no debugging symbols is
18878 described in @ref{Non-debug DLL Symbols}.
18883 This is a prefix of MS Windows-specific commands which print
18884 information about the target system and important OS structures.
18886 @item info w32 selector
18887 This command displays information returned by
18888 the Win32 API @code{GetThreadSelectorEntry} function.
18889 It takes an optional argument that is evaluated to
18890 a long value to give the information about this given selector.
18891 Without argument, this command displays information
18892 about the six segment registers.
18894 @item info w32 thread-information-block
18895 This command displays thread specific information stored in the
18896 Thread Information Block (readable on the X86 CPU family using @code{$fs}
18897 selector for 32-bit programs and @code{$gs} for 64-bit programs).
18901 This is a Cygwin-specific alias of @code{info shared}.
18903 @kindex dll-symbols
18905 This command loads symbols from a dll similarly to
18906 add-sym command but without the need to specify a base address.
18908 @kindex set cygwin-exceptions
18909 @cindex debugging the Cygwin DLL
18910 @cindex Cygwin DLL, debugging
18911 @item set cygwin-exceptions @var{mode}
18912 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
18913 happen inside the Cygwin DLL. If @var{mode} is @code{off},
18914 @value{GDBN} will delay recognition of exceptions, and may ignore some
18915 exceptions which seem to be caused by internal Cygwin DLL
18916 ``bookkeeping''. This option is meant primarily for debugging the
18917 Cygwin DLL itself; the default value is @code{off} to avoid annoying
18918 @value{GDBN} users with false @code{SIGSEGV} signals.
18920 @kindex show cygwin-exceptions
18921 @item show cygwin-exceptions
18922 Displays whether @value{GDBN} will break on exceptions that happen
18923 inside the Cygwin DLL itself.
18925 @kindex set new-console
18926 @item set new-console @var{mode}
18927 If @var{mode} is @code{on} the debuggee will
18928 be started in a new console on next start.
18929 If @var{mode} is @code{off}, the debuggee will
18930 be started in the same console as the debugger.
18932 @kindex show new-console
18933 @item show new-console
18934 Displays whether a new console is used
18935 when the debuggee is started.
18937 @kindex set new-group
18938 @item set new-group @var{mode}
18939 This boolean value controls whether the debuggee should
18940 start a new group or stay in the same group as the debugger.
18941 This affects the way the Windows OS handles
18944 @kindex show new-group
18945 @item show new-group
18946 Displays current value of new-group boolean.
18948 @kindex set debugevents
18949 @item set debugevents
18950 This boolean value adds debug output concerning kernel events related
18951 to the debuggee seen by the debugger. This includes events that
18952 signal thread and process creation and exit, DLL loading and
18953 unloading, console interrupts, and debugging messages produced by the
18954 Windows @code{OutputDebugString} API call.
18956 @kindex set debugexec
18957 @item set debugexec
18958 This boolean value adds debug output concerning execute events
18959 (such as resume thread) seen by the debugger.
18961 @kindex set debugexceptions
18962 @item set debugexceptions
18963 This boolean value adds debug output concerning exceptions in the
18964 debuggee seen by the debugger.
18966 @kindex set debugmemory
18967 @item set debugmemory
18968 This boolean value adds debug output concerning debuggee memory reads
18969 and writes by the debugger.
18973 This boolean values specifies whether the debuggee is called
18974 via a shell or directly (default value is on).
18978 Displays if the debuggee will be started with a shell.
18983 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
18986 @node Non-debug DLL Symbols
18987 @subsubsection Support for DLLs without Debugging Symbols
18988 @cindex DLLs with no debugging symbols
18989 @cindex Minimal symbols and DLLs
18991 Very often on windows, some of the DLLs that your program relies on do
18992 not include symbolic debugging information (for example,
18993 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
18994 symbols in a DLL, it relies on the minimal amount of symbolic
18995 information contained in the DLL's export table. This section
18996 describes working with such symbols, known internally to @value{GDBN} as
18997 ``minimal symbols''.
18999 Note that before the debugged program has started execution, no DLLs
19000 will have been loaded. The easiest way around this problem is simply to
19001 start the program --- either by setting a breakpoint or letting the
19002 program run once to completion. It is also possible to force
19003 @value{GDBN} to load a particular DLL before starting the executable ---
19004 see the shared library information in @ref{Files}, or the
19005 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
19006 explicitly loading symbols from a DLL with no debugging information will
19007 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
19008 which may adversely affect symbol lookup performance.
19010 @subsubsection DLL Name Prefixes
19012 In keeping with the naming conventions used by the Microsoft debugging
19013 tools, DLL export symbols are made available with a prefix based on the
19014 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
19015 also entered into the symbol table, so @code{CreateFileA} is often
19016 sufficient. In some cases there will be name clashes within a program
19017 (particularly if the executable itself includes full debugging symbols)
19018 necessitating the use of the fully qualified name when referring to the
19019 contents of the DLL. Use single-quotes around the name to avoid the
19020 exclamation mark (``!'') being interpreted as a language operator.
19022 Note that the internal name of the DLL may be all upper-case, even
19023 though the file name of the DLL is lower-case, or vice-versa. Since
19024 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
19025 some confusion. If in doubt, try the @code{info functions} and
19026 @code{info variables} commands or even @code{maint print msymbols}
19027 (@pxref{Symbols}). Here's an example:
19030 (@value{GDBP}) info function CreateFileA
19031 All functions matching regular expression "CreateFileA":
19033 Non-debugging symbols:
19034 0x77e885f4 CreateFileA
19035 0x77e885f4 KERNEL32!CreateFileA
19039 (@value{GDBP}) info function !
19040 All functions matching regular expression "!":
19042 Non-debugging symbols:
19043 0x6100114c cygwin1!__assert
19044 0x61004034 cygwin1!_dll_crt0@@0
19045 0x61004240 cygwin1!dll_crt0(per_process *)
19049 @subsubsection Working with Minimal Symbols
19051 Symbols extracted from a DLL's export table do not contain very much
19052 type information. All that @value{GDBN} can do is guess whether a symbol
19053 refers to a function or variable depending on the linker section that
19054 contains the symbol. Also note that the actual contents of the memory
19055 contained in a DLL are not available unless the program is running. This
19056 means that you cannot examine the contents of a variable or disassemble
19057 a function within a DLL without a running program.
19059 Variables are generally treated as pointers and dereferenced
19060 automatically. For this reason, it is often necessary to prefix a
19061 variable name with the address-of operator (``&'') and provide explicit
19062 type information in the command. Here's an example of the type of
19066 (@value{GDBP}) print 'cygwin1!__argv'
19071 (@value{GDBP}) x 'cygwin1!__argv'
19072 0x10021610: "\230y\""
19075 And two possible solutions:
19078 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
19079 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
19083 (@value{GDBP}) x/2x &'cygwin1!__argv'
19084 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
19085 (@value{GDBP}) x/x 0x10021608
19086 0x10021608: 0x0022fd98
19087 (@value{GDBP}) x/s 0x0022fd98
19088 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
19091 Setting a break point within a DLL is possible even before the program
19092 starts execution. However, under these circumstances, @value{GDBN} can't
19093 examine the initial instructions of the function in order to skip the
19094 function's frame set-up code. You can work around this by using ``*&''
19095 to set the breakpoint at a raw memory address:
19098 (@value{GDBP}) break *&'python22!PyOS_Readline'
19099 Breakpoint 1 at 0x1e04eff0
19102 The author of these extensions is not entirely convinced that setting a
19103 break point within a shared DLL like @file{kernel32.dll} is completely
19107 @subsection Commands Specific to @sc{gnu} Hurd Systems
19108 @cindex @sc{gnu} Hurd debugging
19110 This subsection describes @value{GDBN} commands specific to the
19111 @sc{gnu} Hurd native debugging.
19116 @kindex set signals@r{, Hurd command}
19117 @kindex set sigs@r{, Hurd command}
19118 This command toggles the state of inferior signal interception by
19119 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
19120 affected by this command. @code{sigs} is a shorthand alias for
19125 @kindex show signals@r{, Hurd command}
19126 @kindex show sigs@r{, Hurd command}
19127 Show the current state of intercepting inferior's signals.
19129 @item set signal-thread
19130 @itemx set sigthread
19131 @kindex set signal-thread
19132 @kindex set sigthread
19133 This command tells @value{GDBN} which thread is the @code{libc} signal
19134 thread. That thread is run when a signal is delivered to a running
19135 process. @code{set sigthread} is the shorthand alias of @code{set
19138 @item show signal-thread
19139 @itemx show sigthread
19140 @kindex show signal-thread
19141 @kindex show sigthread
19142 These two commands show which thread will run when the inferior is
19143 delivered a signal.
19146 @kindex set stopped@r{, Hurd command}
19147 This commands tells @value{GDBN} that the inferior process is stopped,
19148 as with the @code{SIGSTOP} signal. The stopped process can be
19149 continued by delivering a signal to it.
19152 @kindex show stopped@r{, Hurd command}
19153 This command shows whether @value{GDBN} thinks the debuggee is
19156 @item set exceptions
19157 @kindex set exceptions@r{, Hurd command}
19158 Use this command to turn off trapping of exceptions in the inferior.
19159 When exception trapping is off, neither breakpoints nor
19160 single-stepping will work. To restore the default, set exception
19163 @item show exceptions
19164 @kindex show exceptions@r{, Hurd command}
19165 Show the current state of trapping exceptions in the inferior.
19167 @item set task pause
19168 @kindex set task@r{, Hurd commands}
19169 @cindex task attributes (@sc{gnu} Hurd)
19170 @cindex pause current task (@sc{gnu} Hurd)
19171 This command toggles task suspension when @value{GDBN} has control.
19172 Setting it to on takes effect immediately, and the task is suspended
19173 whenever @value{GDBN} gets control. Setting it to off will take
19174 effect the next time the inferior is continued. If this option is set
19175 to off, you can use @code{set thread default pause on} or @code{set
19176 thread pause on} (see below) to pause individual threads.
19178 @item show task pause
19179 @kindex show task@r{, Hurd commands}
19180 Show the current state of task suspension.
19182 @item set task detach-suspend-count
19183 @cindex task suspend count
19184 @cindex detach from task, @sc{gnu} Hurd
19185 This command sets the suspend count the task will be left with when
19186 @value{GDBN} detaches from it.
19188 @item show task detach-suspend-count
19189 Show the suspend count the task will be left with when detaching.
19191 @item set task exception-port
19192 @itemx set task excp
19193 @cindex task exception port, @sc{gnu} Hurd
19194 This command sets the task exception port to which @value{GDBN} will
19195 forward exceptions. The argument should be the value of the @dfn{send
19196 rights} of the task. @code{set task excp} is a shorthand alias.
19198 @item set noninvasive
19199 @cindex noninvasive task options
19200 This command switches @value{GDBN} to a mode that is the least
19201 invasive as far as interfering with the inferior is concerned. This
19202 is the same as using @code{set task pause}, @code{set exceptions}, and
19203 @code{set signals} to values opposite to the defaults.
19205 @item info send-rights
19206 @itemx info receive-rights
19207 @itemx info port-rights
19208 @itemx info port-sets
19209 @itemx info dead-names
19212 @cindex send rights, @sc{gnu} Hurd
19213 @cindex receive rights, @sc{gnu} Hurd
19214 @cindex port rights, @sc{gnu} Hurd
19215 @cindex port sets, @sc{gnu} Hurd
19216 @cindex dead names, @sc{gnu} Hurd
19217 These commands display information about, respectively, send rights,
19218 receive rights, port rights, port sets, and dead names of a task.
19219 There are also shorthand aliases: @code{info ports} for @code{info
19220 port-rights} and @code{info psets} for @code{info port-sets}.
19222 @item set thread pause
19223 @kindex set thread@r{, Hurd command}
19224 @cindex thread properties, @sc{gnu} Hurd
19225 @cindex pause current thread (@sc{gnu} Hurd)
19226 This command toggles current thread suspension when @value{GDBN} has
19227 control. Setting it to on takes effect immediately, and the current
19228 thread is suspended whenever @value{GDBN} gets control. Setting it to
19229 off will take effect the next time the inferior is continued.
19230 Normally, this command has no effect, since when @value{GDBN} has
19231 control, the whole task is suspended. However, if you used @code{set
19232 task pause off} (see above), this command comes in handy to suspend
19233 only the current thread.
19235 @item show thread pause
19236 @kindex show thread@r{, Hurd command}
19237 This command shows the state of current thread suspension.
19239 @item set thread run
19240 This command sets whether the current thread is allowed to run.
19242 @item show thread run
19243 Show whether the current thread is allowed to run.
19245 @item set thread detach-suspend-count
19246 @cindex thread suspend count, @sc{gnu} Hurd
19247 @cindex detach from thread, @sc{gnu} Hurd
19248 This command sets the suspend count @value{GDBN} will leave on a
19249 thread when detaching. This number is relative to the suspend count
19250 found by @value{GDBN} when it notices the thread; use @code{set thread
19251 takeover-suspend-count} to force it to an absolute value.
19253 @item show thread detach-suspend-count
19254 Show the suspend count @value{GDBN} will leave on the thread when
19257 @item set thread exception-port
19258 @itemx set thread excp
19259 Set the thread exception port to which to forward exceptions. This
19260 overrides the port set by @code{set task exception-port} (see above).
19261 @code{set thread excp} is the shorthand alias.
19263 @item set thread takeover-suspend-count
19264 Normally, @value{GDBN}'s thread suspend counts are relative to the
19265 value @value{GDBN} finds when it notices each thread. This command
19266 changes the suspend counts to be absolute instead.
19268 @item set thread default
19269 @itemx show thread default
19270 @cindex thread default settings, @sc{gnu} Hurd
19271 Each of the above @code{set thread} commands has a @code{set thread
19272 default} counterpart (e.g., @code{set thread default pause}, @code{set
19273 thread default exception-port}, etc.). The @code{thread default}
19274 variety of commands sets the default thread properties for all
19275 threads; you can then change the properties of individual threads with
19276 the non-default commands.
19283 @value{GDBN} provides the following commands specific to the Darwin target:
19286 @item set debug darwin @var{num}
19287 @kindex set debug darwin
19288 When set to a non zero value, enables debugging messages specific to
19289 the Darwin support. Higher values produce more verbose output.
19291 @item show debug darwin
19292 @kindex show debug darwin
19293 Show the current state of Darwin messages.
19295 @item set debug mach-o @var{num}
19296 @kindex set debug mach-o
19297 When set to a non zero value, enables debugging messages while
19298 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
19299 file format used on Darwin for object and executable files.) Higher
19300 values produce more verbose output. This is a command to diagnose
19301 problems internal to @value{GDBN} and should not be needed in normal
19304 @item show debug mach-o
19305 @kindex show debug mach-o
19306 Show the current state of Mach-O file messages.
19308 @item set mach-exceptions on
19309 @itemx set mach-exceptions off
19310 @kindex set mach-exceptions
19311 On Darwin, faults are first reported as a Mach exception and are then
19312 mapped to a Posix signal. Use this command to turn on trapping of
19313 Mach exceptions in the inferior. This might be sometimes useful to
19314 better understand the cause of a fault. The default is off.
19316 @item show mach-exceptions
19317 @kindex show mach-exceptions
19318 Show the current state of exceptions trapping.
19323 @section Embedded Operating Systems
19325 This section describes configurations involving the debugging of
19326 embedded operating systems that are available for several different
19330 * VxWorks:: Using @value{GDBN} with VxWorks
19333 @value{GDBN} includes the ability to debug programs running on
19334 various real-time operating systems.
19337 @subsection Using @value{GDBN} with VxWorks
19343 @kindex target vxworks
19344 @item target vxworks @var{machinename}
19345 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
19346 is the target system's machine name or IP address.
19350 On VxWorks, @code{load} links @var{filename} dynamically on the
19351 current target system as well as adding its symbols in @value{GDBN}.
19353 @value{GDBN} enables developers to spawn and debug tasks running on networked
19354 VxWorks targets from a Unix host. Already-running tasks spawned from
19355 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
19356 both the Unix host and on the VxWorks target. The program
19357 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
19358 installed with the name @code{vxgdb}, to distinguish it from a
19359 @value{GDBN} for debugging programs on the host itself.)
19362 @item VxWorks-timeout @var{args}
19363 @kindex vxworks-timeout
19364 All VxWorks-based targets now support the option @code{vxworks-timeout}.
19365 This option is set by the user, and @var{args} represents the number of
19366 seconds @value{GDBN} waits for responses to rpc's. You might use this if
19367 your VxWorks target is a slow software simulator or is on the far side
19368 of a thin network line.
19371 The following information on connecting to VxWorks was current when
19372 this manual was produced; newer releases of VxWorks may use revised
19375 @findex INCLUDE_RDB
19376 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
19377 to include the remote debugging interface routines in the VxWorks
19378 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
19379 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
19380 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
19381 source debugging task @code{tRdbTask} when VxWorks is booted. For more
19382 information on configuring and remaking VxWorks, see the manufacturer's
19384 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
19386 Once you have included @file{rdb.a} in your VxWorks system image and set
19387 your Unix execution search path to find @value{GDBN}, you are ready to
19388 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
19389 @code{vxgdb}, depending on your installation).
19391 @value{GDBN} comes up showing the prompt:
19398 * VxWorks Connection:: Connecting to VxWorks
19399 * VxWorks Download:: VxWorks download
19400 * VxWorks Attach:: Running tasks
19403 @node VxWorks Connection
19404 @subsubsection Connecting to VxWorks
19406 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
19407 network. To connect to a target whose host name is ``@code{tt}'', type:
19410 (vxgdb) target vxworks tt
19414 @value{GDBN} displays messages like these:
19417 Attaching remote machine across net...
19422 @value{GDBN} then attempts to read the symbol tables of any object modules
19423 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
19424 these files by searching the directories listed in the command search
19425 path (@pxref{Environment, ,Your Program's Environment}); if it fails
19426 to find an object file, it displays a message such as:
19429 prog.o: No such file or directory.
19432 When this happens, add the appropriate directory to the search path with
19433 the @value{GDBN} command @code{path}, and execute the @code{target}
19436 @node VxWorks Download
19437 @subsubsection VxWorks Download
19439 @cindex download to VxWorks
19440 If you have connected to the VxWorks target and you want to debug an
19441 object that has not yet been loaded, you can use the @value{GDBN}
19442 @code{load} command to download a file from Unix to VxWorks
19443 incrementally. The object file given as an argument to the @code{load}
19444 command is actually opened twice: first by the VxWorks target in order
19445 to download the code, then by @value{GDBN} in order to read the symbol
19446 table. This can lead to problems if the current working directories on
19447 the two systems differ. If both systems have NFS mounted the same
19448 filesystems, you can avoid these problems by using absolute paths.
19449 Otherwise, it is simplest to set the working directory on both systems
19450 to the directory in which the object file resides, and then to reference
19451 the file by its name, without any path. For instance, a program
19452 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
19453 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
19454 program, type this on VxWorks:
19457 -> cd "@var{vxpath}/vw/demo/rdb"
19461 Then, in @value{GDBN}, type:
19464 (vxgdb) cd @var{hostpath}/vw/demo/rdb
19465 (vxgdb) load prog.o
19468 @value{GDBN} displays a response similar to this:
19471 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
19474 You can also use the @code{load} command to reload an object module
19475 after editing and recompiling the corresponding source file. Note that
19476 this makes @value{GDBN} delete all currently-defined breakpoints,
19477 auto-displays, and convenience variables, and to clear the value
19478 history. (This is necessary in order to preserve the integrity of
19479 debugger's data structures that reference the target system's symbol
19482 @node VxWorks Attach
19483 @subsubsection Running Tasks
19485 @cindex running VxWorks tasks
19486 You can also attach to an existing task using the @code{attach} command as
19490 (vxgdb) attach @var{task}
19494 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
19495 or suspended when you attach to it. Running tasks are suspended at
19496 the time of attachment.
19498 @node Embedded Processors
19499 @section Embedded Processors
19501 This section goes into details specific to particular embedded
19504 @cindex send command to simulator
19505 Whenever a specific embedded processor has a simulator, @value{GDBN}
19506 allows to send an arbitrary command to the simulator.
19509 @item sim @var{command}
19510 @kindex sim@r{, a command}
19511 Send an arbitrary @var{command} string to the simulator. Consult the
19512 documentation for the specific simulator in use for information about
19513 acceptable commands.
19519 * M32R/D:: Renesas M32R/D
19520 * M68K:: Motorola M68K
19521 * MicroBlaze:: Xilinx MicroBlaze
19522 * MIPS Embedded:: MIPS Embedded
19523 * OpenRISC 1000:: OpenRisc 1000
19524 * PowerPC Embedded:: PowerPC Embedded
19525 * PA:: HP PA Embedded
19526 * Sparclet:: Tsqware Sparclet
19527 * Sparclite:: Fujitsu Sparclite
19528 * Z8000:: Zilog Z8000
19531 * Super-H:: Renesas Super-H
19540 @item target rdi @var{dev}
19541 ARM Angel monitor, via RDI library interface to ADP protocol. You may
19542 use this target to communicate with both boards running the Angel
19543 monitor, or with the EmbeddedICE JTAG debug device.
19546 @item target rdp @var{dev}
19551 @value{GDBN} provides the following ARM-specific commands:
19554 @item set arm disassembler
19556 This commands selects from a list of disassembly styles. The
19557 @code{"std"} style is the standard style.
19559 @item show arm disassembler
19561 Show the current disassembly style.
19563 @item set arm apcs32
19564 @cindex ARM 32-bit mode
19565 This command toggles ARM operation mode between 32-bit and 26-bit.
19567 @item show arm apcs32
19568 Display the current usage of the ARM 32-bit mode.
19570 @item set arm fpu @var{fputype}
19571 This command sets the ARM floating-point unit (FPU) type. The
19572 argument @var{fputype} can be one of these:
19576 Determine the FPU type by querying the OS ABI.
19578 Software FPU, with mixed-endian doubles on little-endian ARM
19581 GCC-compiled FPA co-processor.
19583 Software FPU with pure-endian doubles.
19589 Show the current type of the FPU.
19592 This command forces @value{GDBN} to use the specified ABI.
19595 Show the currently used ABI.
19597 @item set arm fallback-mode (arm|thumb|auto)
19598 @value{GDBN} uses the symbol table, when available, to determine
19599 whether instructions are ARM or Thumb. This command controls
19600 @value{GDBN}'s default behavior when the symbol table is not
19601 available. The default is @samp{auto}, which causes @value{GDBN} to
19602 use the current execution mode (from the @code{T} bit in the @code{CPSR}
19605 @item show arm fallback-mode
19606 Show the current fallback instruction mode.
19608 @item set arm force-mode (arm|thumb|auto)
19609 This command overrides use of the symbol table to determine whether
19610 instructions are ARM or Thumb. The default is @samp{auto}, which
19611 causes @value{GDBN} to use the symbol table and then the setting
19612 of @samp{set arm fallback-mode}.
19614 @item show arm force-mode
19615 Show the current forced instruction mode.
19617 @item set debug arm
19618 Toggle whether to display ARM-specific debugging messages from the ARM
19619 target support subsystem.
19621 @item show debug arm
19622 Show whether ARM-specific debugging messages are enabled.
19625 The following commands are available when an ARM target is debugged
19626 using the RDI interface:
19629 @item rdilogfile @r{[}@var{file}@r{]}
19631 @cindex ADP (Angel Debugger Protocol) logging
19632 Set the filename for the ADP (Angel Debugger Protocol) packet log.
19633 With an argument, sets the log file to the specified @var{file}. With
19634 no argument, show the current log file name. The default log file is
19637 @item rdilogenable @r{[}@var{arg}@r{]}
19638 @kindex rdilogenable
19639 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
19640 enables logging, with an argument 0 or @code{"no"} disables it. With
19641 no arguments displays the current setting. When logging is enabled,
19642 ADP packets exchanged between @value{GDBN} and the RDI target device
19643 are logged to a file.
19645 @item set rdiromatzero
19646 @kindex set rdiromatzero
19647 @cindex ROM at zero address, RDI
19648 Tell @value{GDBN} whether the target has ROM at address 0. If on,
19649 vector catching is disabled, so that zero address can be used. If off
19650 (the default), vector catching is enabled. For this command to take
19651 effect, it needs to be invoked prior to the @code{target rdi} command.
19653 @item show rdiromatzero
19654 @kindex show rdiromatzero
19655 Show the current setting of ROM at zero address.
19657 @item set rdiheartbeat
19658 @kindex set rdiheartbeat
19659 @cindex RDI heartbeat
19660 Enable or disable RDI heartbeat packets. It is not recommended to
19661 turn on this option, since it confuses ARM and EPI JTAG interface, as
19662 well as the Angel monitor.
19664 @item show rdiheartbeat
19665 @kindex show rdiheartbeat
19666 Show the setting of RDI heartbeat packets.
19670 @item target sim @r{[}@var{simargs}@r{]} @dots{}
19671 The @value{GDBN} ARM simulator accepts the following optional arguments.
19674 @item --swi-support=@var{type}
19675 Tell the simulator which SWI interfaces to support.
19676 @var{type} may be a comma separated list of the following values.
19677 The default value is @code{all}.
19690 @subsection Renesas M32R/D and M32R/SDI
19693 @kindex target m32r
19694 @item target m32r @var{dev}
19695 Renesas M32R/D ROM monitor.
19697 @kindex target m32rsdi
19698 @item target m32rsdi @var{dev}
19699 Renesas M32R SDI server, connected via parallel port to the board.
19702 The following @value{GDBN} commands are specific to the M32R monitor:
19705 @item set download-path @var{path}
19706 @kindex set download-path
19707 @cindex find downloadable @sc{srec} files (M32R)
19708 Set the default path for finding downloadable @sc{srec} files.
19710 @item show download-path
19711 @kindex show download-path
19712 Show the default path for downloadable @sc{srec} files.
19714 @item set board-address @var{addr}
19715 @kindex set board-address
19716 @cindex M32-EVA target board address
19717 Set the IP address for the M32R-EVA target board.
19719 @item show board-address
19720 @kindex show board-address
19721 Show the current IP address of the target board.
19723 @item set server-address @var{addr}
19724 @kindex set server-address
19725 @cindex download server address (M32R)
19726 Set the IP address for the download server, which is the @value{GDBN}'s
19729 @item show server-address
19730 @kindex show server-address
19731 Display the IP address of the download server.
19733 @item upload @r{[}@var{file}@r{]}
19734 @kindex upload@r{, M32R}
19735 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
19736 upload capability. If no @var{file} argument is given, the current
19737 executable file is uploaded.
19739 @item tload @r{[}@var{file}@r{]}
19740 @kindex tload@r{, M32R}
19741 Test the @code{upload} command.
19744 The following commands are available for M32R/SDI:
19749 @cindex reset SDI connection, M32R
19750 This command resets the SDI connection.
19754 This command shows the SDI connection status.
19757 @kindex debug_chaos
19758 @cindex M32R/Chaos debugging
19759 Instructs the remote that M32R/Chaos debugging is to be used.
19761 @item use_debug_dma
19762 @kindex use_debug_dma
19763 Instructs the remote to use the DEBUG_DMA method of accessing memory.
19766 @kindex use_mon_code
19767 Instructs the remote to use the MON_CODE method of accessing memory.
19770 @kindex use_ib_break
19771 Instructs the remote to set breakpoints by IB break.
19773 @item use_dbt_break
19774 @kindex use_dbt_break
19775 Instructs the remote to set breakpoints by DBT.
19781 The Motorola m68k configuration includes ColdFire support, and a
19782 target command for the following ROM monitor.
19786 @kindex target dbug
19787 @item target dbug @var{dev}
19788 dBUG ROM monitor for Motorola ColdFire.
19793 @subsection MicroBlaze
19794 @cindex Xilinx MicroBlaze
19795 @cindex XMD, Xilinx Microprocessor Debugger
19797 The MicroBlaze is a soft-core processor supported on various Xilinx
19798 FPGAs, such as Spartan or Virtex series. Boards with these processors
19799 usually have JTAG ports which connect to a host system running the Xilinx
19800 Embedded Development Kit (EDK) or Software Development Kit (SDK).
19801 This host system is used to download the configuration bitstream to
19802 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
19803 communicates with the target board using the JTAG interface and
19804 presents a @code{gdbserver} interface to the board. By default
19805 @code{xmd} uses port @code{1234}. (While it is possible to change
19806 this default port, it requires the use of undocumented @code{xmd}
19807 commands. Contact Xilinx support if you need to do this.)
19809 Use these GDB commands to connect to the MicroBlaze target processor.
19812 @item target remote :1234
19813 Use this command to connect to the target if you are running @value{GDBN}
19814 on the same system as @code{xmd}.
19816 @item target remote @var{xmd-host}:1234
19817 Use this command to connect to the target if it is connected to @code{xmd}
19818 running on a different system named @var{xmd-host}.
19821 Use this command to download a program to the MicroBlaze target.
19823 @item set debug microblaze @var{n}
19824 Enable MicroBlaze-specific debugging messages if non-zero.
19826 @item show debug microblaze @var{n}
19827 Show MicroBlaze-specific debugging level.
19830 @node MIPS Embedded
19831 @subsection @acronym{MIPS} Embedded
19833 @cindex @acronym{MIPS} boards
19834 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
19835 @acronym{MIPS} board attached to a serial line. This is available when
19836 you configure @value{GDBN} with @samp{--target=mips-elf}.
19839 Use these @value{GDBN} commands to specify the connection to your target board:
19842 @item target mips @var{port}
19843 @kindex target mips @var{port}
19844 To run a program on the board, start up @code{@value{GDBP}} with the
19845 name of your program as the argument. To connect to the board, use the
19846 command @samp{target mips @var{port}}, where @var{port} is the name of
19847 the serial port connected to the board. If the program has not already
19848 been downloaded to the board, you may use the @code{load} command to
19849 download it. You can then use all the usual @value{GDBN} commands.
19851 For example, this sequence connects to the target board through a serial
19852 port, and loads and runs a program called @var{prog} through the
19856 host$ @value{GDBP} @var{prog}
19857 @value{GDBN} is free software and @dots{}
19858 (@value{GDBP}) target mips /dev/ttyb
19859 (@value{GDBP}) load @var{prog}
19863 @item target mips @var{hostname}:@var{portnumber}
19864 On some @value{GDBN} host configurations, you can specify a TCP
19865 connection (for instance, to a serial line managed by a terminal
19866 concentrator) instead of a serial port, using the syntax
19867 @samp{@var{hostname}:@var{portnumber}}.
19869 @item target pmon @var{port}
19870 @kindex target pmon @var{port}
19873 @item target ddb @var{port}
19874 @kindex target ddb @var{port}
19875 NEC's DDB variant of PMON for Vr4300.
19877 @item target lsi @var{port}
19878 @kindex target lsi @var{port}
19879 LSI variant of PMON.
19881 @kindex target r3900
19882 @item target r3900 @var{dev}
19883 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
19885 @kindex target array
19886 @item target array @var{dev}
19887 Array Tech LSI33K RAID controller board.
19893 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
19896 @item set mipsfpu double
19897 @itemx set mipsfpu single
19898 @itemx set mipsfpu none
19899 @itemx set mipsfpu auto
19900 @itemx show mipsfpu
19901 @kindex set mipsfpu
19902 @kindex show mipsfpu
19903 @cindex @acronym{MIPS} remote floating point
19904 @cindex floating point, @acronym{MIPS} remote
19905 If your target board does not support the @acronym{MIPS} floating point
19906 coprocessor, you should use the command @samp{set mipsfpu none} (if you
19907 need this, you may wish to put the command in your @value{GDBN} init
19908 file). This tells @value{GDBN} how to find the return value of
19909 functions which return floating point values. It also allows
19910 @value{GDBN} to avoid saving the floating point registers when calling
19911 functions on the board. If you are using a floating point coprocessor
19912 with only single precision floating point support, as on the @sc{r4650}
19913 processor, use the command @samp{set mipsfpu single}. The default
19914 double precision floating point coprocessor may be selected using
19915 @samp{set mipsfpu double}.
19917 In previous versions the only choices were double precision or no
19918 floating point, so @samp{set mipsfpu on} will select double precision
19919 and @samp{set mipsfpu off} will select no floating point.
19921 As usual, you can inquire about the @code{mipsfpu} variable with
19922 @samp{show mipsfpu}.
19924 @item set timeout @var{seconds}
19925 @itemx set retransmit-timeout @var{seconds}
19926 @itemx show timeout
19927 @itemx show retransmit-timeout
19928 @cindex @code{timeout}, @acronym{MIPS} protocol
19929 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
19930 @kindex set timeout
19931 @kindex show timeout
19932 @kindex set retransmit-timeout
19933 @kindex show retransmit-timeout
19934 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
19935 remote protocol, with the @code{set timeout @var{seconds}} command. The
19936 default is 5 seconds. Similarly, you can control the timeout used while
19937 waiting for an acknowledgment of a packet with the @code{set
19938 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
19939 You can inspect both values with @code{show timeout} and @code{show
19940 retransmit-timeout}. (These commands are @emph{only} available when
19941 @value{GDBN} is configured for @samp{--target=mips-elf}.)
19943 The timeout set by @code{set timeout} does not apply when @value{GDBN}
19944 is waiting for your program to stop. In that case, @value{GDBN} waits
19945 forever because it has no way of knowing how long the program is going
19946 to run before stopping.
19948 @item set syn-garbage-limit @var{num}
19949 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
19950 @cindex synchronize with remote @acronym{MIPS} target
19951 Limit the maximum number of characters @value{GDBN} should ignore when
19952 it tries to synchronize with the remote target. The default is 10
19953 characters. Setting the limit to -1 means there's no limit.
19955 @item show syn-garbage-limit
19956 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
19957 Show the current limit on the number of characters to ignore when
19958 trying to synchronize with the remote system.
19960 @item set monitor-prompt @var{prompt}
19961 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
19962 @cindex remote monitor prompt
19963 Tell @value{GDBN} to expect the specified @var{prompt} string from the
19964 remote monitor. The default depends on the target:
19974 @item show monitor-prompt
19975 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
19976 Show the current strings @value{GDBN} expects as the prompt from the
19979 @item set monitor-warnings
19980 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
19981 Enable or disable monitor warnings about hardware breakpoints. This
19982 has effect only for the @code{lsi} target. When on, @value{GDBN} will
19983 display warning messages whose codes are returned by the @code{lsi}
19984 PMON monitor for breakpoint commands.
19986 @item show monitor-warnings
19987 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
19988 Show the current setting of printing monitor warnings.
19990 @item pmon @var{command}
19991 @kindex pmon@r{, @acronym{MIPS} remote}
19992 @cindex send PMON command
19993 This command allows sending an arbitrary @var{command} string to the
19994 monitor. The monitor must be in debug mode for this to work.
19997 @node OpenRISC 1000
19998 @subsection OpenRISC 1000
19999 @cindex OpenRISC 1000
20001 @cindex or1k boards
20002 See OR1k Architecture document (@uref{www.opencores.org}) for more information
20003 about platform and commands.
20007 @kindex target jtag
20008 @item target jtag jtag://@var{host}:@var{port}
20010 Connects to remote JTAG server.
20011 JTAG remote server can be either an or1ksim or JTAG server,
20012 connected via parallel port to the board.
20014 Example: @code{target jtag jtag://localhost:9999}
20017 @item or1ksim @var{command}
20018 If connected to @code{or1ksim} OpenRISC 1000 Architectural
20019 Simulator, proprietary commands can be executed.
20021 @kindex info or1k spr
20022 @item info or1k spr
20023 Displays spr groups.
20025 @item info or1k spr @var{group}
20026 @itemx info or1k spr @var{groupno}
20027 Displays register names in selected group.
20029 @item info or1k spr @var{group} @var{register}
20030 @itemx info or1k spr @var{register}
20031 @itemx info or1k spr @var{groupno} @var{registerno}
20032 @itemx info or1k spr @var{registerno}
20033 Shows information about specified spr register.
20036 @item spr @var{group} @var{register} @var{value}
20037 @itemx spr @var{register @var{value}}
20038 @itemx spr @var{groupno} @var{registerno @var{value}}
20039 @itemx spr @var{registerno @var{value}}
20040 Writes @var{value} to specified spr register.
20043 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
20044 It is very similar to @value{GDBN} trace, except it does not interfere with normal
20045 program execution and is thus much faster. Hardware breakpoints/watchpoint
20046 triggers can be set using:
20049 Load effective address/data
20051 Store effective address/data
20053 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
20058 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
20059 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
20061 @code{htrace} commands:
20062 @cindex OpenRISC 1000 htrace
20065 @item hwatch @var{conditional}
20066 Set hardware watchpoint on combination of Load/Store Effective Address(es)
20067 or Data. For example:
20069 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
20071 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
20075 Display information about current HW trace configuration.
20077 @item htrace trigger @var{conditional}
20078 Set starting criteria for HW trace.
20080 @item htrace qualifier @var{conditional}
20081 Set acquisition qualifier for HW trace.
20083 @item htrace stop @var{conditional}
20084 Set HW trace stopping criteria.
20086 @item htrace record [@var{data}]*
20087 Selects the data to be recorded, when qualifier is met and HW trace was
20090 @item htrace enable
20091 @itemx htrace disable
20092 Enables/disables the HW trace.
20094 @item htrace rewind [@var{filename}]
20095 Clears currently recorded trace data.
20097 If filename is specified, new trace file is made and any newly collected data
20098 will be written there.
20100 @item htrace print [@var{start} [@var{len}]]
20101 Prints trace buffer, using current record configuration.
20103 @item htrace mode continuous
20104 Set continuous trace mode.
20106 @item htrace mode suspend
20107 Set suspend trace mode.
20111 @node PowerPC Embedded
20112 @subsection PowerPC Embedded
20114 @cindex DVC register
20115 @value{GDBN} supports using the DVC (Data Value Compare) register to
20116 implement in hardware simple hardware watchpoint conditions of the form:
20119 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
20120 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
20123 The DVC register will be automatically used when @value{GDBN} detects
20124 such pattern in a condition expression, and the created watchpoint uses one
20125 debug register (either the @code{exact-watchpoints} option is on and the
20126 variable is scalar, or the variable has a length of one byte). This feature
20127 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
20130 When running on PowerPC embedded processors, @value{GDBN} automatically uses
20131 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
20132 in which case watchpoints using only one debug register are created when
20133 watching variables of scalar types.
20135 You can create an artificial array to watch an arbitrary memory
20136 region using one of the following commands (@pxref{Expressions}):
20139 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
20140 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
20143 PowerPC embedded processors support masked watchpoints. See the discussion
20144 about the @code{mask} argument in @ref{Set Watchpoints}.
20146 @cindex ranged breakpoint
20147 PowerPC embedded processors support hardware accelerated
20148 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
20149 the inferior whenever it executes an instruction at any address within
20150 the range it specifies. To set a ranged breakpoint in @value{GDBN},
20151 use the @code{break-range} command.
20153 @value{GDBN} provides the following PowerPC-specific commands:
20156 @kindex break-range
20157 @item break-range @var{start-location}, @var{end-location}
20158 Set a breakpoint for an address range.
20159 @var{start-location} and @var{end-location} can specify a function name,
20160 a line number, an offset of lines from the current line or from the start
20161 location, or an address of an instruction (see @ref{Specify Location},
20162 for a list of all the possible ways to specify a @var{location}.)
20163 The breakpoint will stop execution of the inferior whenever it
20164 executes an instruction at any address within the specified range,
20165 (including @var{start-location} and @var{end-location}.)
20167 @kindex set powerpc
20168 @item set powerpc soft-float
20169 @itemx show powerpc soft-float
20170 Force @value{GDBN} to use (or not use) a software floating point calling
20171 convention. By default, @value{GDBN} selects the calling convention based
20172 on the selected architecture and the provided executable file.
20174 @item set powerpc vector-abi
20175 @itemx show powerpc vector-abi
20176 Force @value{GDBN} to use the specified calling convention for vector
20177 arguments and return values. The valid options are @samp{auto};
20178 @samp{generic}, to avoid vector registers even if they are present;
20179 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
20180 registers. By default, @value{GDBN} selects the calling convention
20181 based on the selected architecture and the provided executable file.
20183 @item set powerpc exact-watchpoints
20184 @itemx show powerpc exact-watchpoints
20185 Allow @value{GDBN} to use only one debug register when watching a variable
20186 of scalar type, thus assuming that the variable is accessed through the
20187 address of its first byte.
20189 @kindex target dink32
20190 @item target dink32 @var{dev}
20191 DINK32 ROM monitor.
20193 @kindex target ppcbug
20194 @item target ppcbug @var{dev}
20195 @kindex target ppcbug1
20196 @item target ppcbug1 @var{dev}
20197 PPCBUG ROM monitor for PowerPC.
20200 @item target sds @var{dev}
20201 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
20204 @cindex SDS protocol
20205 The following commands specific to the SDS protocol are supported
20209 @item set sdstimeout @var{nsec}
20210 @kindex set sdstimeout
20211 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
20212 default is 2 seconds.
20214 @item show sdstimeout
20215 @kindex show sdstimeout
20216 Show the current value of the SDS timeout.
20218 @item sds @var{command}
20219 @kindex sds@r{, a command}
20220 Send the specified @var{command} string to the SDS monitor.
20225 @subsection HP PA Embedded
20229 @kindex target op50n
20230 @item target op50n @var{dev}
20231 OP50N monitor, running on an OKI HPPA board.
20233 @kindex target w89k
20234 @item target w89k @var{dev}
20235 W89K monitor, running on a Winbond HPPA board.
20240 @subsection Tsqware Sparclet
20244 @value{GDBN} enables developers to debug tasks running on
20245 Sparclet targets from a Unix host.
20246 @value{GDBN} uses code that runs on
20247 both the Unix host and on the Sparclet target. The program
20248 @code{@value{GDBP}} is installed and executed on the Unix host.
20251 @item remotetimeout @var{args}
20252 @kindex remotetimeout
20253 @value{GDBN} supports the option @code{remotetimeout}.
20254 This option is set by the user, and @var{args} represents the number of
20255 seconds @value{GDBN} waits for responses.
20258 @cindex compiling, on Sparclet
20259 When compiling for debugging, include the options @samp{-g} to get debug
20260 information and @samp{-Ttext} to relocate the program to where you wish to
20261 load it on the target. You may also want to add the options @samp{-n} or
20262 @samp{-N} in order to reduce the size of the sections. Example:
20265 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
20268 You can use @code{objdump} to verify that the addresses are what you intended:
20271 sparclet-aout-objdump --headers --syms prog
20274 @cindex running, on Sparclet
20276 your Unix execution search path to find @value{GDBN}, you are ready to
20277 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
20278 (or @code{sparclet-aout-gdb}, depending on your installation).
20280 @value{GDBN} comes up showing the prompt:
20287 * Sparclet File:: Setting the file to debug
20288 * Sparclet Connection:: Connecting to Sparclet
20289 * Sparclet Download:: Sparclet download
20290 * Sparclet Execution:: Running and debugging
20293 @node Sparclet File
20294 @subsubsection Setting File to Debug
20296 The @value{GDBN} command @code{file} lets you choose with program to debug.
20299 (gdbslet) file prog
20303 @value{GDBN} then attempts to read the symbol table of @file{prog}.
20304 @value{GDBN} locates
20305 the file by searching the directories listed in the command search
20307 If the file was compiled with debug information (option @samp{-g}), source
20308 files will be searched as well.
20309 @value{GDBN} locates
20310 the source files by searching the directories listed in the directory search
20311 path (@pxref{Environment, ,Your Program's Environment}).
20313 to find a file, it displays a message such as:
20316 prog: No such file or directory.
20319 When this happens, add the appropriate directories to the search paths with
20320 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
20321 @code{target} command again.
20323 @node Sparclet Connection
20324 @subsubsection Connecting to Sparclet
20326 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
20327 To connect to a target on serial port ``@code{ttya}'', type:
20330 (gdbslet) target sparclet /dev/ttya
20331 Remote target sparclet connected to /dev/ttya
20332 main () at ../prog.c:3
20336 @value{GDBN} displays messages like these:
20342 @node Sparclet Download
20343 @subsubsection Sparclet Download
20345 @cindex download to Sparclet
20346 Once connected to the Sparclet target,
20347 you can use the @value{GDBN}
20348 @code{load} command to download the file from the host to the target.
20349 The file name and load offset should be given as arguments to the @code{load}
20351 Since the file format is aout, the program must be loaded to the starting
20352 address. You can use @code{objdump} to find out what this value is. The load
20353 offset is an offset which is added to the VMA (virtual memory address)
20354 of each of the file's sections.
20355 For instance, if the program
20356 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
20357 and bss at 0x12010170, in @value{GDBN}, type:
20360 (gdbslet) load prog 0x12010000
20361 Loading section .text, size 0xdb0 vma 0x12010000
20364 If the code is loaded at a different address then what the program was linked
20365 to, you may need to use the @code{section} and @code{add-symbol-file} commands
20366 to tell @value{GDBN} where to map the symbol table.
20368 @node Sparclet Execution
20369 @subsubsection Running and Debugging
20371 @cindex running and debugging Sparclet programs
20372 You can now begin debugging the task using @value{GDBN}'s execution control
20373 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
20374 manual for the list of commands.
20378 Breakpoint 1 at 0x12010000: file prog.c, line 3.
20380 Starting program: prog
20381 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
20382 3 char *symarg = 0;
20384 4 char *execarg = "hello!";
20389 @subsection Fujitsu Sparclite
20393 @kindex target sparclite
20394 @item target sparclite @var{dev}
20395 Fujitsu sparclite boards, used only for the purpose of loading.
20396 You must use an additional command to debug the program.
20397 For example: target remote @var{dev} using @value{GDBN} standard
20403 @subsection Zilog Z8000
20406 @cindex simulator, Z8000
20407 @cindex Zilog Z8000 simulator
20409 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
20412 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
20413 unsegmented variant of the Z8000 architecture) or the Z8001 (the
20414 segmented variant). The simulator recognizes which architecture is
20415 appropriate by inspecting the object code.
20418 @item target sim @var{args}
20420 @kindex target sim@r{, with Z8000}
20421 Debug programs on a simulated CPU. If the simulator supports setup
20422 options, specify them via @var{args}.
20426 After specifying this target, you can debug programs for the simulated
20427 CPU in the same style as programs for your host computer; use the
20428 @code{file} command to load a new program image, the @code{run} command
20429 to run your program, and so on.
20431 As well as making available all the usual machine registers
20432 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
20433 additional items of information as specially named registers:
20438 Counts clock-ticks in the simulator.
20441 Counts instructions run in the simulator.
20444 Execution time in 60ths of a second.
20448 You can refer to these values in @value{GDBN} expressions with the usual
20449 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
20450 conditional breakpoint that suspends only after at least 5000
20451 simulated clock ticks.
20454 @subsection Atmel AVR
20457 When configured for debugging the Atmel AVR, @value{GDBN} supports the
20458 following AVR-specific commands:
20461 @item info io_registers
20462 @kindex info io_registers@r{, AVR}
20463 @cindex I/O registers (Atmel AVR)
20464 This command displays information about the AVR I/O registers. For
20465 each register, @value{GDBN} prints its number and value.
20472 When configured for debugging CRIS, @value{GDBN} provides the
20473 following CRIS-specific commands:
20476 @item set cris-version @var{ver}
20477 @cindex CRIS version
20478 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
20479 The CRIS version affects register names and sizes. This command is useful in
20480 case autodetection of the CRIS version fails.
20482 @item show cris-version
20483 Show the current CRIS version.
20485 @item set cris-dwarf2-cfi
20486 @cindex DWARF-2 CFI and CRIS
20487 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
20488 Change to @samp{off} when using @code{gcc-cris} whose version is below
20491 @item show cris-dwarf2-cfi
20492 Show the current state of using DWARF-2 CFI.
20494 @item set cris-mode @var{mode}
20496 Set the current CRIS mode to @var{mode}. It should only be changed when
20497 debugging in guru mode, in which case it should be set to
20498 @samp{guru} (the default is @samp{normal}).
20500 @item show cris-mode
20501 Show the current CRIS mode.
20505 @subsection Renesas Super-H
20508 For the Renesas Super-H processor, @value{GDBN} provides these
20513 @kindex regs@r{, Super-H}
20514 This command is deprecated, and @code{info all-registers} should be
20517 Show the values of all Super-H registers.
20519 @item set sh calling-convention @var{convention}
20520 @kindex set sh calling-convention
20521 Set the calling-convention used when calling functions from @value{GDBN}.
20522 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
20523 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
20524 convention. If the DWARF-2 information of the called function specifies
20525 that the function follows the Renesas calling convention, the function
20526 is called using the Renesas calling convention. If the calling convention
20527 is set to @samp{renesas}, the Renesas calling convention is always used,
20528 regardless of the DWARF-2 information. This can be used to override the
20529 default of @samp{gcc} if debug information is missing, or the compiler
20530 does not emit the DWARF-2 calling convention entry for a function.
20532 @item show sh calling-convention
20533 @kindex show sh calling-convention
20534 Show the current calling convention setting.
20539 @node Architectures
20540 @section Architectures
20542 This section describes characteristics of architectures that affect
20543 all uses of @value{GDBN} with the architecture, both native and cross.
20549 * HPPA:: HP PA architecture
20550 * SPU:: Cell Broadband Engine SPU architecture
20555 @subsection x86 Architecture-specific Issues
20558 @item set struct-convention @var{mode}
20559 @kindex set struct-convention
20560 @cindex struct return convention
20561 @cindex struct/union returned in registers
20562 Set the convention used by the inferior to return @code{struct}s and
20563 @code{union}s from functions to @var{mode}. Possible values of
20564 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
20565 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
20566 are returned on the stack, while @code{"reg"} means that a
20567 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
20568 be returned in a register.
20570 @item show struct-convention
20571 @kindex show struct-convention
20572 Show the current setting of the convention to return @code{struct}s
20579 See the following section.
20582 @subsection @acronym{MIPS}
20584 @cindex stack on Alpha
20585 @cindex stack on @acronym{MIPS}
20586 @cindex Alpha stack
20587 @cindex @acronym{MIPS} stack
20588 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
20589 sometimes requires @value{GDBN} to search backward in the object code to
20590 find the beginning of a function.
20592 @cindex response time, @acronym{MIPS} debugging
20593 To improve response time (especially for embedded applications, where
20594 @value{GDBN} may be restricted to a slow serial line for this search)
20595 you may want to limit the size of this search, using one of these
20599 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
20600 @item set heuristic-fence-post @var{limit}
20601 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
20602 search for the beginning of a function. A value of @var{0} (the
20603 default) means there is no limit. However, except for @var{0}, the
20604 larger the limit the more bytes @code{heuristic-fence-post} must search
20605 and therefore the longer it takes to run. You should only need to use
20606 this command when debugging a stripped executable.
20608 @item show heuristic-fence-post
20609 Display the current limit.
20613 These commands are available @emph{only} when @value{GDBN} is configured
20614 for debugging programs on Alpha or @acronym{MIPS} processors.
20616 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
20620 @item set mips abi @var{arg}
20621 @kindex set mips abi
20622 @cindex set ABI for @acronym{MIPS}
20623 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
20624 values of @var{arg} are:
20628 The default ABI associated with the current binary (this is the
20638 @item show mips abi
20639 @kindex show mips abi
20640 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
20642 @item set mips compression @var{arg}
20643 @kindex set mips compression
20644 @cindex code compression, @acronym{MIPS}
20645 Tell @value{GDBN} which @acronym{MIPS} compressed
20646 @acronym{ISA, Instruction Set Architecture} encoding is used by the
20647 inferior. @value{GDBN} uses this for code disassembly and other
20648 internal interpretation purposes. This setting is only referred to
20649 when no executable has been associated with the debugging session or
20650 the executable does not provide information about the encoding it uses.
20651 Otherwise this setting is automatically updated from information
20652 provided by the executable.
20654 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
20655 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
20656 executables containing @acronym{MIPS16} code frequently are not
20657 identified as such.
20659 This setting is ``sticky''; that is, it retains its value across
20660 debugging sessions until reset either explicitly with this command or
20661 implicitly from an executable.
20663 The compiler and/or assembler typically add symbol table annotations to
20664 identify functions compiled for the @acronym{MIPS16} or
20665 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
20666 are present, @value{GDBN} uses them in preference to the global
20667 compressed @acronym{ISA} encoding setting.
20669 @item show mips compression
20670 @kindex show mips compression
20671 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
20672 @value{GDBN} to debug the inferior.
20675 @itemx show mipsfpu
20676 @xref{MIPS Embedded, set mipsfpu}.
20678 @item set mips mask-address @var{arg}
20679 @kindex set mips mask-address
20680 @cindex @acronym{MIPS} addresses, masking
20681 This command determines whether the most-significant 32 bits of 64-bit
20682 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
20683 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
20684 setting, which lets @value{GDBN} determine the correct value.
20686 @item show mips mask-address
20687 @kindex show mips mask-address
20688 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
20691 @item set remote-mips64-transfers-32bit-regs
20692 @kindex set remote-mips64-transfers-32bit-regs
20693 This command controls compatibility with 64-bit @acronym{MIPS} targets that
20694 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
20695 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
20696 and 64 bits for other registers, set this option to @samp{on}.
20698 @item show remote-mips64-transfers-32bit-regs
20699 @kindex show remote-mips64-transfers-32bit-regs
20700 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
20702 @item set debug mips
20703 @kindex set debug mips
20704 This command turns on and off debugging messages for the @acronym{MIPS}-specific
20705 target code in @value{GDBN}.
20707 @item show debug mips
20708 @kindex show debug mips
20709 Show the current setting of @acronym{MIPS} debugging messages.
20715 @cindex HPPA support
20717 When @value{GDBN} is debugging the HP PA architecture, it provides the
20718 following special commands:
20721 @item set debug hppa
20722 @kindex set debug hppa
20723 This command determines whether HPPA architecture-specific debugging
20724 messages are to be displayed.
20726 @item show debug hppa
20727 Show whether HPPA debugging messages are displayed.
20729 @item maint print unwind @var{address}
20730 @kindex maint print unwind@r{, HPPA}
20731 This command displays the contents of the unwind table entry at the
20732 given @var{address}.
20738 @subsection Cell Broadband Engine SPU architecture
20739 @cindex Cell Broadband Engine
20742 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
20743 it provides the following special commands:
20746 @item info spu event
20748 Display SPU event facility status. Shows current event mask
20749 and pending event status.
20751 @item info spu signal
20752 Display SPU signal notification facility status. Shows pending
20753 signal-control word and signal notification mode of both signal
20754 notification channels.
20756 @item info spu mailbox
20757 Display SPU mailbox facility status. Shows all pending entries,
20758 in order of processing, in each of the SPU Write Outbound,
20759 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
20762 Display MFC DMA status. Shows all pending commands in the MFC
20763 DMA queue. For each entry, opcode, tag, class IDs, effective
20764 and local store addresses and transfer size are shown.
20766 @item info spu proxydma
20767 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
20768 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
20769 and local store addresses and transfer size are shown.
20773 When @value{GDBN} is debugging a combined PowerPC/SPU application
20774 on the Cell Broadband Engine, it provides in addition the following
20778 @item set spu stop-on-load @var{arg}
20780 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
20781 will give control to the user when a new SPE thread enters its @code{main}
20782 function. The default is @code{off}.
20784 @item show spu stop-on-load
20786 Show whether to stop for new SPE threads.
20788 @item set spu auto-flush-cache @var{arg}
20789 Set whether to automatically flush the software-managed cache. When set to
20790 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
20791 cache to be flushed whenever SPE execution stops. This provides a consistent
20792 view of PowerPC memory that is accessed via the cache. If an application
20793 does not use the software-managed cache, this option has no effect.
20795 @item show spu auto-flush-cache
20796 Show whether to automatically flush the software-managed cache.
20801 @subsection PowerPC
20802 @cindex PowerPC architecture
20804 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
20805 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
20806 numbers stored in the floating point registers. These values must be stored
20807 in two consecutive registers, always starting at an even register like
20808 @code{f0} or @code{f2}.
20810 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
20811 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
20812 @code{f2} and @code{f3} for @code{$dl1} and so on.
20814 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
20815 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
20818 @node Controlling GDB
20819 @chapter Controlling @value{GDBN}
20821 You can alter the way @value{GDBN} interacts with you by using the
20822 @code{set} command. For commands controlling how @value{GDBN} displays
20823 data, see @ref{Print Settings, ,Print Settings}. Other settings are
20828 * Editing:: Command editing
20829 * Command History:: Command history
20830 * Screen Size:: Screen size
20831 * Numbers:: Numbers
20832 * ABI:: Configuring the current ABI
20833 * Auto-loading:: Automatically loading associated files
20834 * Messages/Warnings:: Optional warnings and messages
20835 * Debugging Output:: Optional messages about internal happenings
20836 * Other Misc Settings:: Other Miscellaneous Settings
20844 @value{GDBN} indicates its readiness to read a command by printing a string
20845 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
20846 can change the prompt string with the @code{set prompt} command. For
20847 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
20848 the prompt in one of the @value{GDBN} sessions so that you can always tell
20849 which one you are talking to.
20851 @emph{Note:} @code{set prompt} does not add a space for you after the
20852 prompt you set. This allows you to set a prompt which ends in a space
20853 or a prompt that does not.
20857 @item set prompt @var{newprompt}
20858 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
20860 @kindex show prompt
20862 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
20865 Versions of @value{GDBN} that ship with Python scripting enabled have
20866 prompt extensions. The commands for interacting with these extensions
20870 @kindex set extended-prompt
20871 @item set extended-prompt @var{prompt}
20872 Set an extended prompt that allows for substitutions.
20873 @xref{gdb.prompt}, for a list of escape sequences that can be used for
20874 substitution. Any escape sequences specified as part of the prompt
20875 string are replaced with the corresponding strings each time the prompt
20881 set extended-prompt Current working directory: \w (gdb)
20884 Note that when an extended-prompt is set, it takes control of the
20885 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
20887 @kindex show extended-prompt
20888 @item show extended-prompt
20889 Prints the extended prompt. Any escape sequences specified as part of
20890 the prompt string with @code{set extended-prompt}, are replaced with the
20891 corresponding strings each time the prompt is displayed.
20895 @section Command Editing
20897 @cindex command line editing
20899 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
20900 @sc{gnu} library provides consistent behavior for programs which provide a
20901 command line interface to the user. Advantages are @sc{gnu} Emacs-style
20902 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
20903 substitution, and a storage and recall of command history across
20904 debugging sessions.
20906 You may control the behavior of command line editing in @value{GDBN} with the
20907 command @code{set}.
20910 @kindex set editing
20913 @itemx set editing on
20914 Enable command line editing (enabled by default).
20916 @item set editing off
20917 Disable command line editing.
20919 @kindex show editing
20921 Show whether command line editing is enabled.
20924 @ifset SYSTEM_READLINE
20925 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
20927 @ifclear SYSTEM_READLINE
20928 @xref{Command Line Editing},
20930 for more details about the Readline
20931 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
20932 encouraged to read that chapter.
20934 @node Command History
20935 @section Command History
20936 @cindex command history
20938 @value{GDBN} can keep track of the commands you type during your
20939 debugging sessions, so that you can be certain of precisely what
20940 happened. Use these commands to manage the @value{GDBN} command
20943 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
20944 package, to provide the history facility.
20945 @ifset SYSTEM_READLINE
20946 @xref{Using History Interactively, , , history, GNU History Library},
20948 @ifclear SYSTEM_READLINE
20949 @xref{Using History Interactively},
20951 for the detailed description of the History library.
20953 To issue a command to @value{GDBN} without affecting certain aspects of
20954 the state which is seen by users, prefix it with @samp{server }
20955 (@pxref{Server Prefix}). This
20956 means that this command will not affect the command history, nor will it
20957 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
20958 pressed on a line by itself.
20960 @cindex @code{server}, command prefix
20961 The server prefix does not affect the recording of values into the value
20962 history; to print a value without recording it into the value history,
20963 use the @code{output} command instead of the @code{print} command.
20965 Here is the description of @value{GDBN} commands related to command
20969 @cindex history substitution
20970 @cindex history file
20971 @kindex set history filename
20972 @cindex @env{GDBHISTFILE}, environment variable
20973 @item set history filename @var{fname}
20974 Set the name of the @value{GDBN} command history file to @var{fname}.
20975 This is the file where @value{GDBN} reads an initial command history
20976 list, and where it writes the command history from this session when it
20977 exits. You can access this list through history expansion or through
20978 the history command editing characters listed below. This file defaults
20979 to the value of the environment variable @code{GDBHISTFILE}, or to
20980 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
20983 @cindex save command history
20984 @kindex set history save
20985 @item set history save
20986 @itemx set history save on
20987 Record command history in a file, whose name may be specified with the
20988 @code{set history filename} command. By default, this option is disabled.
20990 @item set history save off
20991 Stop recording command history in a file.
20993 @cindex history size
20994 @kindex set history size
20995 @cindex @env{HISTSIZE}, environment variable
20996 @item set history size @var{size}
20997 Set the number of commands which @value{GDBN} keeps in its history list.
20998 This defaults to the value of the environment variable
20999 @code{HISTSIZE}, or to 256 if this variable is not set.
21002 History expansion assigns special meaning to the character @kbd{!}.
21003 @ifset SYSTEM_READLINE
21004 @xref{Event Designators, , , history, GNU History Library},
21006 @ifclear SYSTEM_READLINE
21007 @xref{Event Designators},
21011 @cindex history expansion, turn on/off
21012 Since @kbd{!} is also the logical not operator in C, history expansion
21013 is off by default. If you decide to enable history expansion with the
21014 @code{set history expansion on} command, you may sometimes need to
21015 follow @kbd{!} (when it is used as logical not, in an expression) with
21016 a space or a tab to prevent it from being expanded. The readline
21017 history facilities do not attempt substitution on the strings
21018 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
21020 The commands to control history expansion are:
21023 @item set history expansion on
21024 @itemx set history expansion
21025 @kindex set history expansion
21026 Enable history expansion. History expansion is off by default.
21028 @item set history expansion off
21029 Disable history expansion.
21032 @kindex show history
21034 @itemx show history filename
21035 @itemx show history save
21036 @itemx show history size
21037 @itemx show history expansion
21038 These commands display the state of the @value{GDBN} history parameters.
21039 @code{show history} by itself displays all four states.
21044 @kindex show commands
21045 @cindex show last commands
21046 @cindex display command history
21047 @item show commands
21048 Display the last ten commands in the command history.
21050 @item show commands @var{n}
21051 Print ten commands centered on command number @var{n}.
21053 @item show commands +
21054 Print ten commands just after the commands last printed.
21058 @section Screen Size
21059 @cindex size of screen
21060 @cindex pauses in output
21062 Certain commands to @value{GDBN} may produce large amounts of
21063 information output to the screen. To help you read all of it,
21064 @value{GDBN} pauses and asks you for input at the end of each page of
21065 output. Type @key{RET} when you want to continue the output, or @kbd{q}
21066 to discard the remaining output. Also, the screen width setting
21067 determines when to wrap lines of output. Depending on what is being
21068 printed, @value{GDBN} tries to break the line at a readable place,
21069 rather than simply letting it overflow onto the following line.
21071 Normally @value{GDBN} knows the size of the screen from the terminal
21072 driver software. For example, on Unix @value{GDBN} uses the termcap data base
21073 together with the value of the @code{TERM} environment variable and the
21074 @code{stty rows} and @code{stty cols} settings. If this is not correct,
21075 you can override it with the @code{set height} and @code{set
21082 @kindex show height
21083 @item set height @var{lpp}
21085 @itemx set width @var{cpl}
21087 These @code{set} commands specify a screen height of @var{lpp} lines and
21088 a screen width of @var{cpl} characters. The associated @code{show}
21089 commands display the current settings.
21091 If you specify a height of zero lines, @value{GDBN} does not pause during
21092 output no matter how long the output is. This is useful if output is to a
21093 file or to an editor buffer.
21095 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
21096 from wrapping its output.
21098 @item set pagination on
21099 @itemx set pagination off
21100 @kindex set pagination
21101 Turn the output pagination on or off; the default is on. Turning
21102 pagination off is the alternative to @code{set height 0}. Note that
21103 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
21104 Options, -batch}) also automatically disables pagination.
21106 @item show pagination
21107 @kindex show pagination
21108 Show the current pagination mode.
21113 @cindex number representation
21114 @cindex entering numbers
21116 You can always enter numbers in octal, decimal, or hexadecimal in
21117 @value{GDBN} by the usual conventions: octal numbers begin with
21118 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
21119 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
21120 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
21121 10; likewise, the default display for numbers---when no particular
21122 format is specified---is base 10. You can change the default base for
21123 both input and output with the commands described below.
21126 @kindex set input-radix
21127 @item set input-radix @var{base}
21128 Set the default base for numeric input. Supported choices
21129 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
21130 specified either unambiguously or using the current input radix; for
21134 set input-radix 012
21135 set input-radix 10.
21136 set input-radix 0xa
21140 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
21141 leaves the input radix unchanged, no matter what it was, since
21142 @samp{10}, being without any leading or trailing signs of its base, is
21143 interpreted in the current radix. Thus, if the current radix is 16,
21144 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
21147 @kindex set output-radix
21148 @item set output-radix @var{base}
21149 Set the default base for numeric display. Supported choices
21150 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
21151 specified either unambiguously or using the current input radix.
21153 @kindex show input-radix
21154 @item show input-radix
21155 Display the current default base for numeric input.
21157 @kindex show output-radix
21158 @item show output-radix
21159 Display the current default base for numeric display.
21161 @item set radix @r{[}@var{base}@r{]}
21165 These commands set and show the default base for both input and output
21166 of numbers. @code{set radix} sets the radix of input and output to
21167 the same base; without an argument, it resets the radix back to its
21168 default value of 10.
21173 @section Configuring the Current ABI
21175 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
21176 application automatically. However, sometimes you need to override its
21177 conclusions. Use these commands to manage @value{GDBN}'s view of the
21184 One @value{GDBN} configuration can debug binaries for multiple operating
21185 system targets, either via remote debugging or native emulation.
21186 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
21187 but you can override its conclusion using the @code{set osabi} command.
21188 One example where this is useful is in debugging of binaries which use
21189 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
21190 not have the same identifying marks that the standard C library for your
21195 Show the OS ABI currently in use.
21198 With no argument, show the list of registered available OS ABI's.
21200 @item set osabi @var{abi}
21201 Set the current OS ABI to @var{abi}.
21204 @cindex float promotion
21206 Generally, the way that an argument of type @code{float} is passed to a
21207 function depends on whether the function is prototyped. For a prototyped
21208 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
21209 according to the architecture's convention for @code{float}. For unprototyped
21210 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
21211 @code{double} and then passed.
21213 Unfortunately, some forms of debug information do not reliably indicate whether
21214 a function is prototyped. If @value{GDBN} calls a function that is not marked
21215 as prototyped, it consults @kbd{set coerce-float-to-double}.
21218 @kindex set coerce-float-to-double
21219 @item set coerce-float-to-double
21220 @itemx set coerce-float-to-double on
21221 Arguments of type @code{float} will be promoted to @code{double} when passed
21222 to an unprototyped function. This is the default setting.
21224 @item set coerce-float-to-double off
21225 Arguments of type @code{float} will be passed directly to unprototyped
21228 @kindex show coerce-float-to-double
21229 @item show coerce-float-to-double
21230 Show the current setting of promoting @code{float} to @code{double}.
21234 @kindex show cp-abi
21235 @value{GDBN} needs to know the ABI used for your program's C@t{++}
21236 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
21237 used to build your application. @value{GDBN} only fully supports
21238 programs with a single C@t{++} ABI; if your program contains code using
21239 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
21240 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
21241 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
21242 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
21243 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
21244 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
21249 Show the C@t{++} ABI currently in use.
21252 With no argument, show the list of supported C@t{++} ABI's.
21254 @item set cp-abi @var{abi}
21255 @itemx set cp-abi auto
21256 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
21260 @section Automatically loading associated files
21261 @cindex auto-loading
21263 @value{GDBN} sometimes reads files with commands and settings automatically,
21264 without being explicitly told so by the user. We call this feature
21265 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
21266 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
21267 results or introduce security risks (e.g., if the file comes from untrusted
21270 Note that loading of these associated files (including the local @file{.gdbinit}
21271 file) requires accordingly configured @code{auto-load safe-path}
21272 (@pxref{Auto-loading safe path}).
21274 For these reasons, @value{GDBN} includes commands and options to let you
21275 control when to auto-load files and which files should be auto-loaded.
21278 @anchor{set auto-load off}
21279 @kindex set auto-load off
21280 @item set auto-load off
21281 Globally disable loading of all auto-loaded files.
21282 You may want to use this command with the @samp{-iex} option
21283 (@pxref{Option -init-eval-command}) such as:
21285 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
21288 Be aware that system init file (@pxref{System-wide configuration})
21289 and init files from your home directory (@pxref{Home Directory Init File})
21290 still get read (as they come from generally trusted directories).
21291 To prevent @value{GDBN} from auto-loading even those init files, use the
21292 @option{-nx} option (@pxref{Mode Options}), in addition to
21293 @code{set auto-load no}.
21295 @anchor{show auto-load}
21296 @kindex show auto-load
21297 @item show auto-load
21298 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
21302 (gdb) show auto-load
21303 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
21304 libthread-db: Auto-loading of inferior specific libthread_db is on.
21305 local-gdbinit: Auto-loading of .gdbinit script from current directory
21307 python-scripts: Auto-loading of Python scripts is on.
21308 safe-path: List of directories from which it is safe to auto-load files
21309 is $debugdir:$datadir/auto-load.
21310 scripts-directory: List of directories from which to load auto-loaded scripts
21311 is $debugdir:$datadir/auto-load.
21314 @anchor{info auto-load}
21315 @kindex info auto-load
21316 @item info auto-load
21317 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
21321 (gdb) info auto-load
21324 Yes /home/user/gdb/gdb-gdb.gdb
21325 libthread-db: No auto-loaded libthread-db.
21326 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
21330 Yes /home/user/gdb/gdb-gdb.py
21334 These are various kinds of files @value{GDBN} can automatically load:
21338 @xref{objfile-gdb.py file}, controlled by @ref{set auto-load python-scripts}.
21340 @xref{objfile-gdb.gdb file}, controlled by @ref{set auto-load gdb-scripts}.
21342 @xref{dotdebug_gdb_scripts section},
21343 controlled by @ref{set auto-load python-scripts}.
21345 @xref{Init File in the Current Directory},
21346 controlled by @ref{set auto-load local-gdbinit}.
21348 @xref{libthread_db.so.1 file}, controlled by @ref{set auto-load libthread-db}.
21351 These are @value{GDBN} control commands for the auto-loading:
21353 @multitable @columnfractions .5 .5
21354 @item @xref{set auto-load off}.
21355 @tab Disable auto-loading globally.
21356 @item @xref{show auto-load}.
21357 @tab Show setting of all kinds of files.
21358 @item @xref{info auto-load}.
21359 @tab Show state of all kinds of files.
21360 @item @xref{set auto-load gdb-scripts}.
21361 @tab Control for @value{GDBN} command scripts.
21362 @item @xref{show auto-load gdb-scripts}.
21363 @tab Show setting of @value{GDBN} command scripts.
21364 @item @xref{info auto-load gdb-scripts}.
21365 @tab Show state of @value{GDBN} command scripts.
21366 @item @xref{set auto-load python-scripts}.
21367 @tab Control for @value{GDBN} Python scripts.
21368 @item @xref{show auto-load python-scripts}.
21369 @tab Show setting of @value{GDBN} Python scripts.
21370 @item @xref{info auto-load python-scripts}.
21371 @tab Show state of @value{GDBN} Python scripts.
21372 @item @xref{set auto-load scripts-directory}.
21373 @tab Control for @value{GDBN} auto-loaded scripts location.
21374 @item @xref{show auto-load scripts-directory}.
21375 @tab Show @value{GDBN} auto-loaded scripts location.
21376 @item @xref{set auto-load local-gdbinit}.
21377 @tab Control for init file in the current directory.
21378 @item @xref{show auto-load local-gdbinit}.
21379 @tab Show setting of init file in the current directory.
21380 @item @xref{info auto-load local-gdbinit}.
21381 @tab Show state of init file in the current directory.
21382 @item @xref{set auto-load libthread-db}.
21383 @tab Control for thread debugging library.
21384 @item @xref{show auto-load libthread-db}.
21385 @tab Show setting of thread debugging library.
21386 @item @xref{info auto-load libthread-db}.
21387 @tab Show state of thread debugging library.
21388 @item @xref{set auto-load safe-path}.
21389 @tab Control directories trusted for automatic loading.
21390 @item @xref{show auto-load safe-path}.
21391 @tab Show directories trusted for automatic loading.
21392 @item @xref{add-auto-load-safe-path}.
21393 @tab Add directory trusted for automatic loading.
21397 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
21398 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
21399 * objfile-gdb.gdb file:: @samp{set/show/info auto-load gdb-script}
21400 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
21401 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
21402 @xref{Python Auto-loading}.
21405 @node Init File in the Current Directory
21406 @subsection Automatically loading init file in the current directory
21407 @cindex auto-loading init file in the current directory
21409 By default, @value{GDBN} reads and executes the canned sequences of commands
21410 from init file (if any) in the current working directory,
21411 see @ref{Init File in the Current Directory during Startup}.
21413 Note that loading of this local @file{.gdbinit} file also requires accordingly
21414 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
21417 @anchor{set auto-load local-gdbinit}
21418 @kindex set auto-load local-gdbinit
21419 @item set auto-load local-gdbinit [on|off]
21420 Enable or disable the auto-loading of canned sequences of commands
21421 (@pxref{Sequences}) found in init file in the current directory.
21423 @anchor{show auto-load local-gdbinit}
21424 @kindex show auto-load local-gdbinit
21425 @item show auto-load local-gdbinit
21426 Show whether auto-loading of canned sequences of commands from init file in the
21427 current directory is enabled or disabled.
21429 @anchor{info auto-load local-gdbinit}
21430 @kindex info auto-load local-gdbinit
21431 @item info auto-load local-gdbinit
21432 Print whether canned sequences of commands from init file in the
21433 current directory have been auto-loaded.
21436 @node libthread_db.so.1 file
21437 @subsection Automatically loading thread debugging library
21438 @cindex auto-loading libthread_db.so.1
21440 This feature is currently present only on @sc{gnu}/Linux native hosts.
21442 @value{GDBN} reads in some cases thread debugging library from places specific
21443 to the inferior (@pxref{set libthread-db-search-path}).
21445 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
21446 without checking this @samp{set auto-load libthread-db} switch as system
21447 libraries have to be trusted in general. In all other cases of
21448 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
21449 auto-load libthread-db} is enabled before trying to open such thread debugging
21452 Note that loading of this debugging library also requires accordingly configured
21453 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
21456 @anchor{set auto-load libthread-db}
21457 @kindex set auto-load libthread-db
21458 @item set auto-load libthread-db [on|off]
21459 Enable or disable the auto-loading of inferior specific thread debugging library.
21461 @anchor{show auto-load libthread-db}
21462 @kindex show auto-load libthread-db
21463 @item show auto-load libthread-db
21464 Show whether auto-loading of inferior specific thread debugging library is
21465 enabled or disabled.
21467 @anchor{info auto-load libthread-db}
21468 @kindex info auto-load libthread-db
21469 @item info auto-load libthread-db
21470 Print the list of all loaded inferior specific thread debugging libraries and
21471 for each such library print list of inferior @var{pid}s using it.
21474 @node objfile-gdb.gdb file
21475 @subsection The @file{@var{objfile}-gdb.gdb} file
21476 @cindex auto-loading @file{@var{objfile}-gdb.gdb}
21478 @value{GDBN} tries to load an @file{@var{objfile}-gdb.gdb} file containing
21479 canned sequences of commands (@pxref{Sequences}), as long as @samp{set
21480 auto-load gdb-scripts} is set to @samp{on}.
21482 Note that loading of this script file also requires accordingly configured
21483 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
21485 For more background refer to the similar Python scripts auto-loading
21486 description (@pxref{objfile-gdb.py file}).
21489 @anchor{set auto-load gdb-scripts}
21490 @kindex set auto-load gdb-scripts
21491 @item set auto-load gdb-scripts [on|off]
21492 Enable or disable the auto-loading of canned sequences of commands scripts.
21494 @anchor{show auto-load gdb-scripts}
21495 @kindex show auto-load gdb-scripts
21496 @item show auto-load gdb-scripts
21497 Show whether auto-loading of canned sequences of commands scripts is enabled or
21500 @anchor{info auto-load gdb-scripts}
21501 @kindex info auto-load gdb-scripts
21502 @cindex print list of auto-loaded canned sequences of commands scripts
21503 @item info auto-load gdb-scripts [@var{regexp}]
21504 Print the list of all canned sequences of commands scripts that @value{GDBN}
21508 If @var{regexp} is supplied only canned sequences of commands scripts with
21509 matching names are printed.
21511 @node Auto-loading safe path
21512 @subsection Security restriction for auto-loading
21513 @cindex auto-loading safe-path
21515 As the files of inferior can come from untrusted source (such as submitted by
21516 an application user) @value{GDBN} does not always load any files automatically.
21517 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
21518 directories trusted for loading files not explicitly requested by user.
21519 Each directory can also be a shell wildcard pattern.
21521 If the path is not set properly you will see a warning and the file will not
21526 Reading symbols from /home/user/gdb/gdb...done.
21527 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
21528 declined by your `auto-load safe-path' set
21529 to "$debugdir:$datadir/auto-load".
21530 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
21531 declined by your `auto-load safe-path' set
21532 to "$debugdir:$datadir/auto-load".
21535 The list of trusted directories is controlled by the following commands:
21538 @anchor{set auto-load safe-path}
21539 @kindex set auto-load safe-path
21540 @item set auto-load safe-path @r{[}@var{directories}@r{]}
21541 Set the list of directories (and their subdirectories) trusted for automatic
21542 loading and execution of scripts. You can also enter a specific trusted file.
21543 Each directory can also be a shell wildcard pattern; wildcards do not match
21544 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
21545 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
21546 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
21547 its default value as specified during @value{GDBN} compilation.
21549 The list of directories uses path separator (@samp{:} on GNU and Unix
21550 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
21551 to the @env{PATH} environment variable.
21553 @anchor{show auto-load safe-path}
21554 @kindex show auto-load safe-path
21555 @item show auto-load safe-path
21556 Show the list of directories trusted for automatic loading and execution of
21559 @anchor{add-auto-load-safe-path}
21560 @kindex add-auto-load-safe-path
21561 @item add-auto-load-safe-path
21562 Add an entry (or list of entries) the list of directories trusted for automatic
21563 loading and execution of scripts. Multiple entries may be delimited by the
21564 host platform path separator in use.
21567 This variable defaults to what @code{--with-auto-load-dir} has been configured
21568 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
21569 substitution applies the same as for @ref{set auto-load scripts-directory}.
21570 The default @code{set auto-load safe-path} value can be also overriden by
21571 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
21573 Setting this variable to @file{/} disables this security protection,
21574 corresponding @value{GDBN} configuration option is
21575 @option{--without-auto-load-safe-path}.
21576 This variable is supposed to be set to the system directories writable by the
21577 system superuser only. Users can add their source directories in init files in
21578 their home directories (@pxref{Home Directory Init File}). See also deprecated
21579 init file in the current directory
21580 (@pxref{Init File in the Current Directory during Startup}).
21582 To force @value{GDBN} to load the files it declined to load in the previous
21583 example, you could use one of the following ways:
21586 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
21587 Specify this trusted directory (or a file) as additional component of the list.
21588 You have to specify also any existing directories displayed by
21589 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
21591 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
21592 Specify this directory as in the previous case but just for a single
21593 @value{GDBN} session.
21595 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
21596 Disable auto-loading safety for a single @value{GDBN} session.
21597 This assumes all the files you debug during this @value{GDBN} session will come
21598 from trusted sources.
21600 @item @kbd{./configure --without-auto-load-safe-path}
21601 During compilation of @value{GDBN} you may disable any auto-loading safety.
21602 This assumes all the files you will ever debug with this @value{GDBN} come from
21606 On the other hand you can also explicitly forbid automatic files loading which
21607 also suppresses any such warning messages:
21610 @item @kbd{gdb -iex "set auto-load no" @dots{}}
21611 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
21613 @item @file{~/.gdbinit}: @samp{set auto-load no}
21614 Disable auto-loading globally for the user
21615 (@pxref{Home Directory Init File}). While it is improbable, you could also
21616 use system init file instead (@pxref{System-wide configuration}).
21619 This setting applies to the file names as entered by user. If no entry matches
21620 @value{GDBN} tries as a last resort to also resolve all the file names into
21621 their canonical form (typically resolving symbolic links) and compare the
21622 entries again. @value{GDBN} already canonicalizes most of the filenames on its
21623 own before starting the comparison so a canonical form of directories is
21624 recommended to be entered.
21626 @node Auto-loading verbose mode
21627 @subsection Displaying files tried for auto-load
21628 @cindex auto-loading verbose mode
21630 For better visibility of all the file locations where you can place scripts to
21631 be auto-loaded with inferior --- or to protect yourself against accidental
21632 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
21633 all the files attempted to be loaded. Both existing and non-existing files may
21636 For example the list of directories from which it is safe to auto-load files
21637 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
21638 may not be too obvious while setting it up.
21641 (gdb) set debug auto-load on
21642 (gdb) file ~/src/t/true
21643 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
21644 for objfile "/tmp/true".
21645 auto-load: Updating directories of "/usr:/opt".
21646 auto-load: Using directory "/usr".
21647 auto-load: Using directory "/opt".
21648 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
21649 by your `auto-load safe-path' set to "/usr:/opt".
21653 @anchor{set debug auto-load}
21654 @kindex set debug auto-load
21655 @item set debug auto-load [on|off]
21656 Set whether to print the filenames attempted to be auto-loaded.
21658 @anchor{show debug auto-load}
21659 @kindex show debug auto-load
21660 @item show debug auto-load
21661 Show whether printing of the filenames attempted to be auto-loaded is turned
21665 @node Messages/Warnings
21666 @section Optional Warnings and Messages
21668 @cindex verbose operation
21669 @cindex optional warnings
21670 By default, @value{GDBN} is silent about its inner workings. If you are
21671 running on a slow machine, you may want to use the @code{set verbose}
21672 command. This makes @value{GDBN} tell you when it does a lengthy
21673 internal operation, so you will not think it has crashed.
21675 Currently, the messages controlled by @code{set verbose} are those
21676 which announce that the symbol table for a source file is being read;
21677 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
21680 @kindex set verbose
21681 @item set verbose on
21682 Enables @value{GDBN} output of certain informational messages.
21684 @item set verbose off
21685 Disables @value{GDBN} output of certain informational messages.
21687 @kindex show verbose
21689 Displays whether @code{set verbose} is on or off.
21692 By default, if @value{GDBN} encounters bugs in the symbol table of an
21693 object file, it is silent; but if you are debugging a compiler, you may
21694 find this information useful (@pxref{Symbol Errors, ,Errors Reading
21699 @kindex set complaints
21700 @item set complaints @var{limit}
21701 Permits @value{GDBN} to output @var{limit} complaints about each type of
21702 unusual symbols before becoming silent about the problem. Set
21703 @var{limit} to zero to suppress all complaints; set it to a large number
21704 to prevent complaints from being suppressed.
21706 @kindex show complaints
21707 @item show complaints
21708 Displays how many symbol complaints @value{GDBN} is permitted to produce.
21712 @anchor{confirmation requests}
21713 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
21714 lot of stupid questions to confirm certain commands. For example, if
21715 you try to run a program which is already running:
21719 The program being debugged has been started already.
21720 Start it from the beginning? (y or n)
21723 If you are willing to unflinchingly face the consequences of your own
21724 commands, you can disable this ``feature'':
21728 @kindex set confirm
21730 @cindex confirmation
21731 @cindex stupid questions
21732 @item set confirm off
21733 Disables confirmation requests. Note that running @value{GDBN} with
21734 the @option{--batch} option (@pxref{Mode Options, -batch}) also
21735 automatically disables confirmation requests.
21737 @item set confirm on
21738 Enables confirmation requests (the default).
21740 @kindex show confirm
21742 Displays state of confirmation requests.
21746 @cindex command tracing
21747 If you need to debug user-defined commands or sourced files you may find it
21748 useful to enable @dfn{command tracing}. In this mode each command will be
21749 printed as it is executed, prefixed with one or more @samp{+} symbols, the
21750 quantity denoting the call depth of each command.
21753 @kindex set trace-commands
21754 @cindex command scripts, debugging
21755 @item set trace-commands on
21756 Enable command tracing.
21757 @item set trace-commands off
21758 Disable command tracing.
21759 @item show trace-commands
21760 Display the current state of command tracing.
21763 @node Debugging Output
21764 @section Optional Messages about Internal Happenings
21765 @cindex optional debugging messages
21767 @value{GDBN} has commands that enable optional debugging messages from
21768 various @value{GDBN} subsystems; normally these commands are of
21769 interest to @value{GDBN} maintainers, or when reporting a bug. This
21770 section documents those commands.
21773 @kindex set exec-done-display
21774 @item set exec-done-display
21775 Turns on or off the notification of asynchronous commands'
21776 completion. When on, @value{GDBN} will print a message when an
21777 asynchronous command finishes its execution. The default is off.
21778 @kindex show exec-done-display
21779 @item show exec-done-display
21780 Displays the current setting of asynchronous command completion
21783 @cindex gdbarch debugging info
21784 @cindex architecture debugging info
21785 @item set debug arch
21786 Turns on or off display of gdbarch debugging info. The default is off
21788 @item show debug arch
21789 Displays the current state of displaying gdbarch debugging info.
21790 @item set debug aix-thread
21791 @cindex AIX threads
21792 Display debugging messages about inner workings of the AIX thread
21794 @item show debug aix-thread
21795 Show the current state of AIX thread debugging info display.
21796 @item set debug check-physname
21798 Check the results of the ``physname'' computation. When reading DWARF
21799 debugging information for C@t{++}, @value{GDBN} attempts to compute
21800 each entity's name. @value{GDBN} can do this computation in two
21801 different ways, depending on exactly what information is present.
21802 When enabled, this setting causes @value{GDBN} to compute the names
21803 both ways and display any discrepancies.
21804 @item show debug check-physname
21805 Show the current state of ``physname'' checking.
21806 @item set debug dwarf2-die
21807 @cindex DWARF2 DIEs
21808 Dump DWARF2 DIEs after they are read in.
21809 The value is the number of nesting levels to print.
21810 A value of zero turns off the display.
21811 @item show debug dwarf2-die
21812 Show the current state of DWARF2 DIE debugging.
21813 @item set debug dwarf2-read
21814 @cindex DWARF2 Reading
21815 Turns on or off display of debugging messages related to reading
21816 DWARF debug info. The default is off.
21817 @item show debug dwarf2-read
21818 Show the current state of DWARF2 reader debugging.
21819 @item set debug displaced
21820 @cindex displaced stepping debugging info
21821 Turns on or off display of @value{GDBN} debugging info for the
21822 displaced stepping support. The default is off.
21823 @item show debug displaced
21824 Displays the current state of displaying @value{GDBN} debugging info
21825 related to displaced stepping.
21826 @item set debug event
21827 @cindex event debugging info
21828 Turns on or off display of @value{GDBN} event debugging info. The
21830 @item show debug event
21831 Displays the current state of displaying @value{GDBN} event debugging
21833 @item set debug expression
21834 @cindex expression debugging info
21835 Turns on or off display of debugging info about @value{GDBN}
21836 expression parsing. The default is off.
21837 @item show debug expression
21838 Displays the current state of displaying debugging info about
21839 @value{GDBN} expression parsing.
21840 @item set debug frame
21841 @cindex frame debugging info
21842 Turns on or off display of @value{GDBN} frame debugging info. The
21844 @item show debug frame
21845 Displays the current state of displaying @value{GDBN} frame debugging
21847 @item set debug gnu-nat
21848 @cindex @sc{gnu}/Hurd debug messages
21849 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
21850 @item show debug gnu-nat
21851 Show the current state of @sc{gnu}/Hurd debugging messages.
21852 @item set debug infrun
21853 @cindex inferior debugging info
21854 Turns on or off display of @value{GDBN} debugging info for running the inferior.
21855 The default is off. @file{infrun.c} contains GDB's runtime state machine used
21856 for implementing operations such as single-stepping the inferior.
21857 @item show debug infrun
21858 Displays the current state of @value{GDBN} inferior debugging.
21859 @item set debug jit
21860 @cindex just-in-time compilation, debugging messages
21861 Turns on or off debugging messages from JIT debug support.
21862 @item show debug jit
21863 Displays the current state of @value{GDBN} JIT debugging.
21864 @item set debug lin-lwp
21865 @cindex @sc{gnu}/Linux LWP debug messages
21866 @cindex Linux lightweight processes
21867 Turns on or off debugging messages from the Linux LWP debug support.
21868 @item show debug lin-lwp
21869 Show the current state of Linux LWP debugging messages.
21870 @item set debug observer
21871 @cindex observer debugging info
21872 Turns on or off display of @value{GDBN} observer debugging. This
21873 includes info such as the notification of observable events.
21874 @item show debug observer
21875 Displays the current state of observer debugging.
21876 @item set debug overload
21877 @cindex C@t{++} overload debugging info
21878 Turns on or off display of @value{GDBN} C@t{++} overload debugging
21879 info. This includes info such as ranking of functions, etc. The default
21881 @item show debug overload
21882 Displays the current state of displaying @value{GDBN} C@t{++} overload
21884 @cindex expression parser, debugging info
21885 @cindex debug expression parser
21886 @item set debug parser
21887 Turns on or off the display of expression parser debugging output.
21888 Internally, this sets the @code{yydebug} variable in the expression
21889 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
21890 details. The default is off.
21891 @item show debug parser
21892 Show the current state of expression parser debugging.
21893 @cindex packets, reporting on stdout
21894 @cindex serial connections, debugging
21895 @cindex debug remote protocol
21896 @cindex remote protocol debugging
21897 @cindex display remote packets
21898 @item set debug remote
21899 Turns on or off display of reports on all packets sent back and forth across
21900 the serial line to the remote machine. The info is printed on the
21901 @value{GDBN} standard output stream. The default is off.
21902 @item show debug remote
21903 Displays the state of display of remote packets.
21904 @item set debug serial
21905 Turns on or off display of @value{GDBN} serial debugging info. The
21907 @item show debug serial
21908 Displays the current state of displaying @value{GDBN} serial debugging
21910 @item set debug solib-frv
21911 @cindex FR-V shared-library debugging
21912 Turns on or off debugging messages for FR-V shared-library code.
21913 @item show debug solib-frv
21914 Display the current state of FR-V shared-library code debugging
21916 @item set debug symtab-create
21917 @cindex symbol table creation
21918 Turns on or off display of debugging messages related to symbol table creation.
21919 The default is off.
21920 @item show debug symtab-create
21921 Show the current state of symbol table creation debugging.
21922 @item set debug target
21923 @cindex target debugging info
21924 Turns on or off display of @value{GDBN} target debugging info. This info
21925 includes what is going on at the target level of GDB, as it happens. The
21926 default is 0. Set it to 1 to track events, and to 2 to also track the
21927 value of large memory transfers. Changes to this flag do not take effect
21928 until the next time you connect to a target or use the @code{run} command.
21929 @item show debug target
21930 Displays the current state of displaying @value{GDBN} target debugging
21932 @item set debug timestamp
21933 @cindex timestampping debugging info
21934 Turns on or off display of timestamps with @value{GDBN} debugging info.
21935 When enabled, seconds and microseconds are displayed before each debugging
21937 @item show debug timestamp
21938 Displays the current state of displaying timestamps with @value{GDBN}
21940 @item set debugvarobj
21941 @cindex variable object debugging info
21942 Turns on or off display of @value{GDBN} variable object debugging
21943 info. The default is off.
21944 @item show debugvarobj
21945 Displays the current state of displaying @value{GDBN} variable object
21947 @item set debug xml
21948 @cindex XML parser debugging
21949 Turns on or off debugging messages for built-in XML parsers.
21950 @item show debug xml
21951 Displays the current state of XML debugging messages.
21954 @node Other Misc Settings
21955 @section Other Miscellaneous Settings
21956 @cindex miscellaneous settings
21959 @kindex set interactive-mode
21960 @item set interactive-mode
21961 If @code{on}, forces @value{GDBN} to assume that GDB was started
21962 in a terminal. In practice, this means that @value{GDBN} should wait
21963 for the user to answer queries generated by commands entered at
21964 the command prompt. If @code{off}, forces @value{GDBN} to operate
21965 in the opposite mode, and it uses the default answers to all queries.
21966 If @code{auto} (the default), @value{GDBN} tries to determine whether
21967 its standard input is a terminal, and works in interactive-mode if it
21968 is, non-interactively otherwise.
21970 In the vast majority of cases, the debugger should be able to guess
21971 correctly which mode should be used. But this setting can be useful
21972 in certain specific cases, such as running a MinGW @value{GDBN}
21973 inside a cygwin window.
21975 @kindex show interactive-mode
21976 @item show interactive-mode
21977 Displays whether the debugger is operating in interactive mode or not.
21980 @node Extending GDB
21981 @chapter Extending @value{GDBN}
21982 @cindex extending GDB
21984 @value{GDBN} provides three mechanisms for extension. The first is based
21985 on composition of @value{GDBN} commands, the second is based on the
21986 Python scripting language, and the third is for defining new aliases of
21989 To facilitate the use of the first two extensions, @value{GDBN} is capable
21990 of evaluating the contents of a file. When doing so, @value{GDBN}
21991 can recognize which scripting language is being used by looking at
21992 the filename extension. Files with an unrecognized filename extension
21993 are always treated as a @value{GDBN} Command Files.
21994 @xref{Command Files,, Command files}.
21996 You can control how @value{GDBN} evaluates these files with the following
22000 @kindex set script-extension
22001 @kindex show script-extension
22002 @item set script-extension off
22003 All scripts are always evaluated as @value{GDBN} Command Files.
22005 @item set script-extension soft
22006 The debugger determines the scripting language based on filename
22007 extension. If this scripting language is supported, @value{GDBN}
22008 evaluates the script using that language. Otherwise, it evaluates
22009 the file as a @value{GDBN} Command File.
22011 @item set script-extension strict
22012 The debugger determines the scripting language based on filename
22013 extension, and evaluates the script using that language. If the
22014 language is not supported, then the evaluation fails.
22016 @item show script-extension
22017 Display the current value of the @code{script-extension} option.
22022 * Sequences:: Canned Sequences of Commands
22023 * Python:: Scripting @value{GDBN} using Python
22024 * Aliases:: Creating new spellings of existing commands
22028 @section Canned Sequences of Commands
22030 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
22031 Command Lists}), @value{GDBN} provides two ways to store sequences of
22032 commands for execution as a unit: user-defined commands and command
22036 * Define:: How to define your own commands
22037 * Hooks:: Hooks for user-defined commands
22038 * Command Files:: How to write scripts of commands to be stored in a file
22039 * Output:: Commands for controlled output
22043 @subsection User-defined Commands
22045 @cindex user-defined command
22046 @cindex arguments, to user-defined commands
22047 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
22048 which you assign a new name as a command. This is done with the
22049 @code{define} command. User commands may accept up to 10 arguments
22050 separated by whitespace. Arguments are accessed within the user command
22051 via @code{$arg0@dots{}$arg9}. A trivial example:
22055 print $arg0 + $arg1 + $arg2
22060 To execute the command use:
22067 This defines the command @code{adder}, which prints the sum of
22068 its three arguments. Note the arguments are text substitutions, so they may
22069 reference variables, use complex expressions, or even perform inferior
22072 @cindex argument count in user-defined commands
22073 @cindex how many arguments (user-defined commands)
22074 In addition, @code{$argc} may be used to find out how many arguments have
22075 been passed. This expands to a number in the range 0@dots{}10.
22080 print $arg0 + $arg1
22083 print $arg0 + $arg1 + $arg2
22091 @item define @var{commandname}
22092 Define a command named @var{commandname}. If there is already a command
22093 by that name, you are asked to confirm that you want to redefine it.
22094 @var{commandname} may be a bare command name consisting of letters,
22095 numbers, dashes, and underscores. It may also start with any predefined
22096 prefix command. For example, @samp{define target my-target} creates
22097 a user-defined @samp{target my-target} command.
22099 The definition of the command is made up of other @value{GDBN} command lines,
22100 which are given following the @code{define} command. The end of these
22101 commands is marked by a line containing @code{end}.
22104 @kindex end@r{ (user-defined commands)}
22105 @item document @var{commandname}
22106 Document the user-defined command @var{commandname}, so that it can be
22107 accessed by @code{help}. The command @var{commandname} must already be
22108 defined. This command reads lines of documentation just as @code{define}
22109 reads the lines of the command definition, ending with @code{end}.
22110 After the @code{document} command is finished, @code{help} on command
22111 @var{commandname} displays the documentation you have written.
22113 You may use the @code{document} command again to change the
22114 documentation of a command. Redefining the command with @code{define}
22115 does not change the documentation.
22117 @kindex dont-repeat
22118 @cindex don't repeat command
22120 Used inside a user-defined command, this tells @value{GDBN} that this
22121 command should not be repeated when the user hits @key{RET}
22122 (@pxref{Command Syntax, repeat last command}).
22124 @kindex help user-defined
22125 @item help user-defined
22126 List all user-defined commands and all python commands defined in class
22127 COMAND_USER. The first line of the documentation or docstring is
22132 @itemx show user @var{commandname}
22133 Display the @value{GDBN} commands used to define @var{commandname} (but
22134 not its documentation). If no @var{commandname} is given, display the
22135 definitions for all user-defined commands.
22136 This does not work for user-defined python commands.
22138 @cindex infinite recursion in user-defined commands
22139 @kindex show max-user-call-depth
22140 @kindex set max-user-call-depth
22141 @item show max-user-call-depth
22142 @itemx set max-user-call-depth
22143 The value of @code{max-user-call-depth} controls how many recursion
22144 levels are allowed in user-defined commands before @value{GDBN} suspects an
22145 infinite recursion and aborts the command.
22146 This does not apply to user-defined python commands.
22149 In addition to the above commands, user-defined commands frequently
22150 use control flow commands, described in @ref{Command Files}.
22152 When user-defined commands are executed, the
22153 commands of the definition are not printed. An error in any command
22154 stops execution of the user-defined command.
22156 If used interactively, commands that would ask for confirmation proceed
22157 without asking when used inside a user-defined command. Many @value{GDBN}
22158 commands that normally print messages to say what they are doing omit the
22159 messages when used in a user-defined command.
22162 @subsection User-defined Command Hooks
22163 @cindex command hooks
22164 @cindex hooks, for commands
22165 @cindex hooks, pre-command
22168 You may define @dfn{hooks}, which are a special kind of user-defined
22169 command. Whenever you run the command @samp{foo}, if the user-defined
22170 command @samp{hook-foo} exists, it is executed (with no arguments)
22171 before that command.
22173 @cindex hooks, post-command
22175 A hook may also be defined which is run after the command you executed.
22176 Whenever you run the command @samp{foo}, if the user-defined command
22177 @samp{hookpost-foo} exists, it is executed (with no arguments) after
22178 that command. Post-execution hooks may exist simultaneously with
22179 pre-execution hooks, for the same command.
22181 It is valid for a hook to call the command which it hooks. If this
22182 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
22184 @c It would be nice if hookpost could be passed a parameter indicating
22185 @c if the command it hooks executed properly or not. FIXME!
22187 @kindex stop@r{, a pseudo-command}
22188 In addition, a pseudo-command, @samp{stop} exists. Defining
22189 (@samp{hook-stop}) makes the associated commands execute every time
22190 execution stops in your program: before breakpoint commands are run,
22191 displays are printed, or the stack frame is printed.
22193 For example, to ignore @code{SIGALRM} signals while
22194 single-stepping, but treat them normally during normal execution,
22199 handle SIGALRM nopass
22203 handle SIGALRM pass
22206 define hook-continue
22207 handle SIGALRM pass
22211 As a further example, to hook at the beginning and end of the @code{echo}
22212 command, and to add extra text to the beginning and end of the message,
22220 define hookpost-echo
22224 (@value{GDBP}) echo Hello World
22225 <<<---Hello World--->>>
22230 You can define a hook for any single-word command in @value{GDBN}, but
22231 not for command aliases; you should define a hook for the basic command
22232 name, e.g.@: @code{backtrace} rather than @code{bt}.
22233 @c FIXME! So how does Joe User discover whether a command is an alias
22235 You can hook a multi-word command by adding @code{hook-} or
22236 @code{hookpost-} to the last word of the command, e.g.@:
22237 @samp{define target hook-remote} to add a hook to @samp{target remote}.
22239 If an error occurs during the execution of your hook, execution of
22240 @value{GDBN} commands stops and @value{GDBN} issues a prompt
22241 (before the command that you actually typed had a chance to run).
22243 If you try to define a hook which does not match any known command, you
22244 get a warning from the @code{define} command.
22246 @node Command Files
22247 @subsection Command Files
22249 @cindex command files
22250 @cindex scripting commands
22251 A command file for @value{GDBN} is a text file made of lines that are
22252 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
22253 also be included. An empty line in a command file does nothing; it
22254 does not mean to repeat the last command, as it would from the
22257 You can request the execution of a command file with the @code{source}
22258 command. Note that the @code{source} command is also used to evaluate
22259 scripts that are not Command Files. The exact behavior can be configured
22260 using the @code{script-extension} setting.
22261 @xref{Extending GDB,, Extending GDB}.
22265 @cindex execute commands from a file
22266 @item source [-s] [-v] @var{filename}
22267 Execute the command file @var{filename}.
22270 The lines in a command file are generally executed sequentially,
22271 unless the order of execution is changed by one of the
22272 @emph{flow-control commands} described below. The commands are not
22273 printed as they are executed. An error in any command terminates
22274 execution of the command file and control is returned to the console.
22276 @value{GDBN} first searches for @var{filename} in the current directory.
22277 If the file is not found there, and @var{filename} does not specify a
22278 directory, then @value{GDBN} also looks for the file on the source search path
22279 (specified with the @samp{directory} command);
22280 except that @file{$cdir} is not searched because the compilation directory
22281 is not relevant to scripts.
22283 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
22284 on the search path even if @var{filename} specifies a directory.
22285 The search is done by appending @var{filename} to each element of the
22286 search path. So, for example, if @var{filename} is @file{mylib/myscript}
22287 and the search path contains @file{/home/user} then @value{GDBN} will
22288 look for the script @file{/home/user/mylib/myscript}.
22289 The search is also done if @var{filename} is an absolute path.
22290 For example, if @var{filename} is @file{/tmp/myscript} and
22291 the search path contains @file{/home/user} then @value{GDBN} will
22292 look for the script @file{/home/user/tmp/myscript}.
22293 For DOS-like systems, if @var{filename} contains a drive specification,
22294 it is stripped before concatenation. For example, if @var{filename} is
22295 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
22296 will look for the script @file{c:/tmp/myscript}.
22298 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
22299 each command as it is executed. The option must be given before
22300 @var{filename}, and is interpreted as part of the filename anywhere else.
22302 Commands that would ask for confirmation if used interactively proceed
22303 without asking when used in a command file. Many @value{GDBN} commands that
22304 normally print messages to say what they are doing omit the messages
22305 when called from command files.
22307 @value{GDBN} also accepts command input from standard input. In this
22308 mode, normal output goes to standard output and error output goes to
22309 standard error. Errors in a command file supplied on standard input do
22310 not terminate execution of the command file---execution continues with
22314 gdb < cmds > log 2>&1
22317 (The syntax above will vary depending on the shell used.) This example
22318 will execute commands from the file @file{cmds}. All output and errors
22319 would be directed to @file{log}.
22321 Since commands stored on command files tend to be more general than
22322 commands typed interactively, they frequently need to deal with
22323 complicated situations, such as different or unexpected values of
22324 variables and symbols, changes in how the program being debugged is
22325 built, etc. @value{GDBN} provides a set of flow-control commands to
22326 deal with these complexities. Using these commands, you can write
22327 complex scripts that loop over data structures, execute commands
22328 conditionally, etc.
22335 This command allows to include in your script conditionally executed
22336 commands. The @code{if} command takes a single argument, which is an
22337 expression to evaluate. It is followed by a series of commands that
22338 are executed only if the expression is true (its value is nonzero).
22339 There can then optionally be an @code{else} line, followed by a series
22340 of commands that are only executed if the expression was false. The
22341 end of the list is marked by a line containing @code{end}.
22345 This command allows to write loops. Its syntax is similar to
22346 @code{if}: the command takes a single argument, which is an expression
22347 to evaluate, and must be followed by the commands to execute, one per
22348 line, terminated by an @code{end}. These commands are called the
22349 @dfn{body} of the loop. The commands in the body of @code{while} are
22350 executed repeatedly as long as the expression evaluates to true.
22354 This command exits the @code{while} loop in whose body it is included.
22355 Execution of the script continues after that @code{while}s @code{end}
22358 @kindex loop_continue
22359 @item loop_continue
22360 This command skips the execution of the rest of the body of commands
22361 in the @code{while} loop in whose body it is included. Execution
22362 branches to the beginning of the @code{while} loop, where it evaluates
22363 the controlling expression.
22365 @kindex end@r{ (if/else/while commands)}
22367 Terminate the block of commands that are the body of @code{if},
22368 @code{else}, or @code{while} flow-control commands.
22373 @subsection Commands for Controlled Output
22375 During the execution of a command file or a user-defined command, normal
22376 @value{GDBN} output is suppressed; the only output that appears is what is
22377 explicitly printed by the commands in the definition. This section
22378 describes three commands useful for generating exactly the output you
22383 @item echo @var{text}
22384 @c I do not consider backslash-space a standard C escape sequence
22385 @c because it is not in ANSI.
22386 Print @var{text}. Nonprinting characters can be included in
22387 @var{text} using C escape sequences, such as @samp{\n} to print a
22388 newline. @strong{No newline is printed unless you specify one.}
22389 In addition to the standard C escape sequences, a backslash followed
22390 by a space stands for a space. This is useful for displaying a
22391 string with spaces at the beginning or the end, since leading and
22392 trailing spaces are otherwise trimmed from all arguments.
22393 To print @samp{@w{ }and foo =@w{ }}, use the command
22394 @samp{echo \@w{ }and foo = \@w{ }}.
22396 A backslash at the end of @var{text} can be used, as in C, to continue
22397 the command onto subsequent lines. For example,
22400 echo This is some text\n\
22401 which is continued\n\
22402 onto several lines.\n
22405 produces the same output as
22408 echo This is some text\n
22409 echo which is continued\n
22410 echo onto several lines.\n
22414 @item output @var{expression}
22415 Print the value of @var{expression} and nothing but that value: no
22416 newlines, no @samp{$@var{nn} = }. The value is not entered in the
22417 value history either. @xref{Expressions, ,Expressions}, for more information
22420 @item output/@var{fmt} @var{expression}
22421 Print the value of @var{expression} in format @var{fmt}. You can use
22422 the same formats as for @code{print}. @xref{Output Formats,,Output
22423 Formats}, for more information.
22426 @item printf @var{template}, @var{expressions}@dots{}
22427 Print the values of one or more @var{expressions} under the control of
22428 the string @var{template}. To print several values, make
22429 @var{expressions} be a comma-separated list of individual expressions,
22430 which may be either numbers or pointers. Their values are printed as
22431 specified by @var{template}, exactly as a C program would do by
22432 executing the code below:
22435 printf (@var{template}, @var{expressions}@dots{});
22438 As in @code{C} @code{printf}, ordinary characters in @var{template}
22439 are printed verbatim, while @dfn{conversion specification} introduced
22440 by the @samp{%} character cause subsequent @var{expressions} to be
22441 evaluated, their values converted and formatted according to type and
22442 style information encoded in the conversion specifications, and then
22445 For example, you can print two values in hex like this:
22448 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
22451 @code{printf} supports all the standard @code{C} conversion
22452 specifications, including the flags and modifiers between the @samp{%}
22453 character and the conversion letter, with the following exceptions:
22457 The argument-ordering modifiers, such as @samp{2$}, are not supported.
22460 The modifier @samp{*} is not supported for specifying precision or
22464 The @samp{'} flag (for separation of digits into groups according to
22465 @code{LC_NUMERIC'}) is not supported.
22468 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
22472 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
22475 The conversion letters @samp{a} and @samp{A} are not supported.
22479 Note that the @samp{ll} type modifier is supported only if the
22480 underlying @code{C} implementation used to build @value{GDBN} supports
22481 the @code{long long int} type, and the @samp{L} type modifier is
22482 supported only if @code{long double} type is available.
22484 As in @code{C}, @code{printf} supports simple backslash-escape
22485 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
22486 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
22487 single character. Octal and hexadecimal escape sequences are not
22490 Additionally, @code{printf} supports conversion specifications for DFP
22491 (@dfn{Decimal Floating Point}) types using the following length modifiers
22492 together with a floating point specifier.
22497 @samp{H} for printing @code{Decimal32} types.
22500 @samp{D} for printing @code{Decimal64} types.
22503 @samp{DD} for printing @code{Decimal128} types.
22506 If the underlying @code{C} implementation used to build @value{GDBN} has
22507 support for the three length modifiers for DFP types, other modifiers
22508 such as width and precision will also be available for @value{GDBN} to use.
22510 In case there is no such @code{C} support, no additional modifiers will be
22511 available and the value will be printed in the standard way.
22513 Here's an example of printing DFP types using the above conversion letters:
22515 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
22519 @item eval @var{template}, @var{expressions}@dots{}
22520 Convert the values of one or more @var{expressions} under the control of
22521 the string @var{template} to a command line, and call it.
22526 @section Scripting @value{GDBN} using Python
22527 @cindex python scripting
22528 @cindex scripting with python
22530 You can script @value{GDBN} using the @uref{http://www.python.org/,
22531 Python programming language}. This feature is available only if
22532 @value{GDBN} was configured using @option{--with-python}.
22534 @cindex python directory
22535 Python scripts used by @value{GDBN} should be installed in
22536 @file{@var{data-directory}/python}, where @var{data-directory} is
22537 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
22538 This directory, known as the @dfn{python directory},
22539 is automatically added to the Python Search Path in order to allow
22540 the Python interpreter to locate all scripts installed at this location.
22542 Additionally, @value{GDBN} commands and convenience functions which
22543 are written in Python and are located in the
22544 @file{@var{data-directory}/python/gdb/command} or
22545 @file{@var{data-directory}/python/gdb/function} directories are
22546 automatically imported when @value{GDBN} starts.
22549 * Python Commands:: Accessing Python from @value{GDBN}.
22550 * Python API:: Accessing @value{GDBN} from Python.
22551 * Python Auto-loading:: Automatically loading Python code.
22552 * Python modules:: Python modules provided by @value{GDBN}.
22555 @node Python Commands
22556 @subsection Python Commands
22557 @cindex python commands
22558 @cindex commands to access python
22560 @value{GDBN} provides one command for accessing the Python interpreter,
22561 and one related setting:
22565 @item python @r{[}@var{code}@r{]}
22566 The @code{python} command can be used to evaluate Python code.
22568 If given an argument, the @code{python} command will evaluate the
22569 argument as a Python command. For example:
22572 (@value{GDBP}) python print 23
22576 If you do not provide an argument to @code{python}, it will act as a
22577 multi-line command, like @code{define}. In this case, the Python
22578 script is made up of subsequent command lines, given after the
22579 @code{python} command. This command list is terminated using a line
22580 containing @code{end}. For example:
22583 (@value{GDBP}) python
22585 End with a line saying just "end".
22591 @kindex set python print-stack
22592 @item set python print-stack
22593 By default, @value{GDBN} will print only the message component of a
22594 Python exception when an error occurs in a Python script. This can be
22595 controlled using @code{set python print-stack}: if @code{full}, then
22596 full Python stack printing is enabled; if @code{none}, then Python stack
22597 and message printing is disabled; if @code{message}, the default, only
22598 the message component of the error is printed.
22601 It is also possible to execute a Python script from the @value{GDBN}
22605 @item source @file{script-name}
22606 The script name must end with @samp{.py} and @value{GDBN} must be configured
22607 to recognize the script language based on filename extension using
22608 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
22610 @item python execfile ("script-name")
22611 This method is based on the @code{execfile} Python built-in function,
22612 and thus is always available.
22616 @subsection Python API
22618 @cindex programming in python
22620 @cindex python stdout
22621 @cindex python pagination
22622 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
22623 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
22624 A Python program which outputs to one of these streams may have its
22625 output interrupted by the user (@pxref{Screen Size}). In this
22626 situation, a Python @code{KeyboardInterrupt} exception is thrown.
22629 * Basic Python:: Basic Python Functions.
22630 * Exception Handling:: How Python exceptions are translated.
22631 * Values From Inferior:: Python representation of values.
22632 * Types In Python:: Python representation of types.
22633 * Pretty Printing API:: Pretty-printing values.
22634 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
22635 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
22636 * Inferiors In Python:: Python representation of inferiors (processes)
22637 * Events In Python:: Listening for events from @value{GDBN}.
22638 * Threads In Python:: Accessing inferior threads from Python.
22639 * Commands In Python:: Implementing new commands in Python.
22640 * Parameters In Python:: Adding new @value{GDBN} parameters.
22641 * Functions In Python:: Writing new convenience functions.
22642 * Progspaces In Python:: Program spaces.
22643 * Objfiles In Python:: Object files.
22644 * Frames In Python:: Accessing inferior stack frames from Python.
22645 * Blocks In Python:: Accessing frame blocks from Python.
22646 * Symbols In Python:: Python representation of symbols.
22647 * Symbol Tables In Python:: Python representation of symbol tables.
22648 * Breakpoints In Python:: Manipulating breakpoints using Python.
22649 * Finish Breakpoints in Python:: Setting Breakpoints on function return
22651 * Lazy Strings In Python:: Python representation of lazy strings.
22655 @subsubsection Basic Python
22657 @cindex python functions
22658 @cindex python module
22660 @value{GDBN} introduces a new Python module, named @code{gdb}. All
22661 methods and classes added by @value{GDBN} are placed in this module.
22662 @value{GDBN} automatically @code{import}s the @code{gdb} module for
22663 use in all scripts evaluated by the @code{python} command.
22665 @findex gdb.PYTHONDIR
22666 @defvar gdb.PYTHONDIR
22667 A string containing the python directory (@pxref{Python}).
22670 @findex gdb.execute
22671 @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]})
22672 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
22673 If a GDB exception happens while @var{command} runs, it is
22674 translated as described in @ref{Exception Handling,,Exception Handling}.
22676 @var{from_tty} specifies whether @value{GDBN} ought to consider this
22677 command as having originated from the user invoking it interactively.
22678 It must be a boolean value. If omitted, it defaults to @code{False}.
22680 By default, any output produced by @var{command} is sent to
22681 @value{GDBN}'s standard output. If the @var{to_string} parameter is
22682 @code{True}, then output will be collected by @code{gdb.execute} and
22683 returned as a string. The default is @code{False}, in which case the
22684 return value is @code{None}. If @var{to_string} is @code{True}, the
22685 @value{GDBN} virtual terminal will be temporarily set to unlimited width
22686 and height, and its pagination will be disabled; @pxref{Screen Size}.
22689 @findex gdb.breakpoints
22690 @defun gdb.breakpoints ()
22691 Return a sequence holding all of @value{GDBN}'s breakpoints.
22692 @xref{Breakpoints In Python}, for more information.
22695 @findex gdb.parameter
22696 @defun gdb.parameter (parameter)
22697 Return the value of a @value{GDBN} parameter. @var{parameter} is a
22698 string naming the parameter to look up; @var{parameter} may contain
22699 spaces if the parameter has a multi-part name. For example,
22700 @samp{print object} is a valid parameter name.
22702 If the named parameter does not exist, this function throws a
22703 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
22704 parameter's value is converted to a Python value of the appropriate
22705 type, and returned.
22708 @findex gdb.history
22709 @defun gdb.history (number)
22710 Return a value from @value{GDBN}'s value history (@pxref{Value
22711 History}). @var{number} indicates which history element to return.
22712 If @var{number} is negative, then @value{GDBN} will take its absolute value
22713 and count backward from the last element (i.e., the most recent element) to
22714 find the value to return. If @var{number} is zero, then @value{GDBN} will
22715 return the most recent element. If the element specified by @var{number}
22716 doesn't exist in the value history, a @code{gdb.error} exception will be
22719 If no exception is raised, the return value is always an instance of
22720 @code{gdb.Value} (@pxref{Values From Inferior}).
22723 @findex gdb.parse_and_eval
22724 @defun gdb.parse_and_eval (expression)
22725 Parse @var{expression} as an expression in the current language,
22726 evaluate it, and return the result as a @code{gdb.Value}.
22727 @var{expression} must be a string.
22729 This function can be useful when implementing a new command
22730 (@pxref{Commands In Python}), as it provides a way to parse the
22731 command's argument as an expression. It is also useful simply to
22732 compute values, for example, it is the only way to get the value of a
22733 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
22736 @findex gdb.find_pc_line
22737 @defun gdb.find_pc_line (pc)
22738 Return the @code{gdb.Symtab_and_line} object corresponding to the
22739 @var{pc} value. @xref{Symbol Tables In Python}. If an invalid
22740 value of @var{pc} is passed as an argument, then the @code{symtab} and
22741 @code{line} attributes of the returned @code{gdb.Symtab_and_line} object
22742 will be @code{None} and 0 respectively.
22745 @findex gdb.post_event
22746 @defun gdb.post_event (event)
22747 Put @var{event}, a callable object taking no arguments, into
22748 @value{GDBN}'s internal event queue. This callable will be invoked at
22749 some later point, during @value{GDBN}'s event processing. Events
22750 posted using @code{post_event} will be run in the order in which they
22751 were posted; however, there is no way to know when they will be
22752 processed relative to other events inside @value{GDBN}.
22754 @value{GDBN} is not thread-safe. If your Python program uses multiple
22755 threads, you must be careful to only call @value{GDBN}-specific
22756 functions in the main @value{GDBN} thread. @code{post_event} ensures
22760 (@value{GDBP}) python
22764 > def __init__(self, message):
22765 > self.message = message;
22766 > def __call__(self):
22767 > gdb.write(self.message)
22769 >class MyThread1 (threading.Thread):
22771 > gdb.post_event(Writer("Hello "))
22773 >class MyThread2 (threading.Thread):
22775 > gdb.post_event(Writer("World\n"))
22777 >MyThread1().start()
22778 >MyThread2().start()
22780 (@value{GDBP}) Hello World
22785 @defun gdb.write (string @r{[}, stream{]})
22786 Print a string to @value{GDBN}'s paginated output stream. The
22787 optional @var{stream} determines the stream to print to. The default
22788 stream is @value{GDBN}'s standard output stream. Possible stream
22795 @value{GDBN}'s standard output stream.
22800 @value{GDBN}'s standard error stream.
22805 @value{GDBN}'s log stream (@pxref{Logging Output}).
22808 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
22809 call this function and will automatically direct the output to the
22814 @defun gdb.flush ()
22815 Flush the buffer of a @value{GDBN} paginated stream so that the
22816 contents are displayed immediately. @value{GDBN} will flush the
22817 contents of a stream automatically when it encounters a newline in the
22818 buffer. The optional @var{stream} determines the stream to flush. The
22819 default stream is @value{GDBN}'s standard output stream. Possible
22826 @value{GDBN}'s standard output stream.
22831 @value{GDBN}'s standard error stream.
22836 @value{GDBN}'s log stream (@pxref{Logging Output}).
22840 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
22841 call this function for the relevant stream.
22844 @findex gdb.target_charset
22845 @defun gdb.target_charset ()
22846 Return the name of the current target character set (@pxref{Character
22847 Sets}). This differs from @code{gdb.parameter('target-charset')} in
22848 that @samp{auto} is never returned.
22851 @findex gdb.target_wide_charset
22852 @defun gdb.target_wide_charset ()
22853 Return the name of the current target wide character set
22854 (@pxref{Character Sets}). This differs from
22855 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
22859 @findex gdb.solib_name
22860 @defun gdb.solib_name (address)
22861 Return the name of the shared library holding the given @var{address}
22862 as a string, or @code{None}.
22865 @findex gdb.decode_line
22866 @defun gdb.decode_line @r{[}expression@r{]}
22867 Return locations of the line specified by @var{expression}, or of the
22868 current line if no argument was given. This function returns a Python
22869 tuple containing two elements. The first element contains a string
22870 holding any unparsed section of @var{expression} (or @code{None} if
22871 the expression has been fully parsed). The second element contains
22872 either @code{None} or another tuple that contains all the locations
22873 that match the expression represented as @code{gdb.Symtab_and_line}
22874 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
22875 provided, it is decoded the way that @value{GDBN}'s inbuilt
22876 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
22879 @defun gdb.prompt_hook (current_prompt)
22880 @anchor{prompt_hook}
22882 If @var{prompt_hook} is callable, @value{GDBN} will call the method
22883 assigned to this operation before a prompt is displayed by
22886 The parameter @code{current_prompt} contains the current @value{GDBN}
22887 prompt. This method must return a Python string, or @code{None}. If
22888 a string is returned, the @value{GDBN} prompt will be set to that
22889 string. If @code{None} is returned, @value{GDBN} will continue to use
22890 the current prompt.
22892 Some prompts cannot be substituted in @value{GDBN}. Secondary prompts
22893 such as those used by readline for command input, and annotation
22894 related prompts are prohibited from being changed.
22897 @node Exception Handling
22898 @subsubsection Exception Handling
22899 @cindex python exceptions
22900 @cindex exceptions, python
22902 When executing the @code{python} command, Python exceptions
22903 uncaught within the Python code are translated to calls to
22904 @value{GDBN} error-reporting mechanism. If the command that called
22905 @code{python} does not handle the error, @value{GDBN} will
22906 terminate it and print an error message containing the Python
22907 exception name, the associated value, and the Python call stack
22908 backtrace at the point where the exception was raised. Example:
22911 (@value{GDBP}) python print foo
22912 Traceback (most recent call last):
22913 File "<string>", line 1, in <module>
22914 NameError: name 'foo' is not defined
22917 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
22918 Python code are converted to Python exceptions. The type of the
22919 Python exception depends on the error.
22923 This is the base class for most exceptions generated by @value{GDBN}.
22924 It is derived from @code{RuntimeError}, for compatibility with earlier
22925 versions of @value{GDBN}.
22927 If an error occurring in @value{GDBN} does not fit into some more
22928 specific category, then the generated exception will have this type.
22930 @item gdb.MemoryError
22931 This is a subclass of @code{gdb.error} which is thrown when an
22932 operation tried to access invalid memory in the inferior.
22934 @item KeyboardInterrupt
22935 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
22936 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
22939 In all cases, your exception handler will see the @value{GDBN} error
22940 message as its value and the Python call stack backtrace at the Python
22941 statement closest to where the @value{GDBN} error occured as the
22944 @findex gdb.GdbError
22945 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
22946 it is useful to be able to throw an exception that doesn't cause a
22947 traceback to be printed. For example, the user may have invoked the
22948 command incorrectly. Use the @code{gdb.GdbError} exception
22949 to handle this case. Example:
22953 >class HelloWorld (gdb.Command):
22954 > """Greet the whole world."""
22955 > def __init__ (self):
22956 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
22957 > def invoke (self, args, from_tty):
22958 > argv = gdb.string_to_argv (args)
22959 > if len (argv) != 0:
22960 > raise gdb.GdbError ("hello-world takes no arguments")
22961 > print "Hello, World!"
22964 (gdb) hello-world 42
22965 hello-world takes no arguments
22968 @node Values From Inferior
22969 @subsubsection Values From Inferior
22970 @cindex values from inferior, with Python
22971 @cindex python, working with values from inferior
22973 @cindex @code{gdb.Value}
22974 @value{GDBN} provides values it obtains from the inferior program in
22975 an object of type @code{gdb.Value}. @value{GDBN} uses this object
22976 for its internal bookkeeping of the inferior's values, and for
22977 fetching values when necessary.
22979 Inferior values that are simple scalars can be used directly in
22980 Python expressions that are valid for the value's data type. Here's
22981 an example for an integer or floating-point value @code{some_val}:
22988 As result of this, @code{bar} will also be a @code{gdb.Value} object
22989 whose values are of the same type as those of @code{some_val}.
22991 Inferior values that are structures or instances of some class can
22992 be accessed using the Python @dfn{dictionary syntax}. For example, if
22993 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
22994 can access its @code{foo} element with:
22997 bar = some_val['foo']
23000 Again, @code{bar} will also be a @code{gdb.Value} object.
23002 A @code{gdb.Value} that represents a function can be executed via
23003 inferior function call. Any arguments provided to the call must match
23004 the function's prototype, and must be provided in the order specified
23007 For example, @code{some_val} is a @code{gdb.Value} instance
23008 representing a function that takes two integers as arguments. To
23009 execute this function, call it like so:
23012 result = some_val (10,20)
23015 Any values returned from a function call will be stored as a
23018 The following attributes are provided:
23021 @defvar Value.address
23022 If this object is addressable, this read-only attribute holds a
23023 @code{gdb.Value} object representing the address. Otherwise,
23024 this attribute holds @code{None}.
23027 @cindex optimized out value in Python
23028 @defvar Value.is_optimized_out
23029 This read-only boolean attribute is true if the compiler optimized out
23030 this value, thus it is not available for fetching from the inferior.
23034 The type of this @code{gdb.Value}. The value of this attribute is a
23035 @code{gdb.Type} object (@pxref{Types In Python}).
23038 @defvar Value.dynamic_type
23039 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
23040 type information (@acronym{RTTI}) to determine the dynamic type of the
23041 value. If this value is of class type, it will return the class in
23042 which the value is embedded, if any. If this value is of pointer or
23043 reference to a class type, it will compute the dynamic type of the
23044 referenced object, and return a pointer or reference to that type,
23045 respectively. In all other cases, it will return the value's static
23048 Note that this feature will only work when debugging a C@t{++} program
23049 that includes @acronym{RTTI} for the object in question. Otherwise,
23050 it will just return the static type of the value as in @kbd{ptype foo}
23051 (@pxref{Symbols, ptype}).
23054 @defvar Value.is_lazy
23055 The value of this read-only boolean attribute is @code{True} if this
23056 @code{gdb.Value} has not yet been fetched from the inferior.
23057 @value{GDBN} does not fetch values until necessary, for efficiency.
23061 myval = gdb.parse_and_eval ('somevar')
23064 The value of @code{somevar} is not fetched at this time. It will be
23065 fetched when the value is needed, or when the @code{fetch_lazy}
23070 The following methods are provided:
23073 @defun Value.__init__ (@var{val})
23074 Many Python values can be converted directly to a @code{gdb.Value} via
23075 this object initializer. Specifically:
23078 @item Python boolean
23079 A Python boolean is converted to the boolean type from the current
23082 @item Python integer
23083 A Python integer is converted to the C @code{long} type for the
23084 current architecture.
23087 A Python long is converted to the C @code{long long} type for the
23088 current architecture.
23091 A Python float is converted to the C @code{double} type for the
23092 current architecture.
23094 @item Python string
23095 A Python string is converted to a target string, using the current
23098 @item @code{gdb.Value}
23099 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
23101 @item @code{gdb.LazyString}
23102 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
23103 Python}), then the lazy string's @code{value} method is called, and
23104 its result is used.
23108 @defun Value.cast (type)
23109 Return a new instance of @code{gdb.Value} that is the result of
23110 casting this instance to the type described by @var{type}, which must
23111 be a @code{gdb.Type} object. If the cast cannot be performed for some
23112 reason, this method throws an exception.
23115 @defun Value.dereference ()
23116 For pointer data types, this method returns a new @code{gdb.Value} object
23117 whose contents is the object pointed to by the pointer. For example, if
23118 @code{foo} is a C pointer to an @code{int}, declared in your C program as
23125 then you can use the corresponding @code{gdb.Value} to access what
23126 @code{foo} points to like this:
23129 bar = foo.dereference ()
23132 The result @code{bar} will be a @code{gdb.Value} object holding the
23133 value pointed to by @code{foo}.
23135 A similar function @code{Value.referenced_value} exists which also
23136 returns @code{gdb.Value} objects corresonding to the values pointed to
23137 by pointer values (and additionally, values referenced by reference
23138 values). However, the behavior of @code{Value.dereference}
23139 differs from @code{Value.referenced_value} by the fact that the
23140 behavior of @code{Value.dereference} is identical to applying the C
23141 unary operator @code{*} on a given value. For example, consider a
23142 reference to a pointer @code{ptrref}, declared in your C@t{++} program
23146 typedef int *intptr;
23150 intptr &ptrref = ptr;
23153 Though @code{ptrref} is a reference value, one can apply the method
23154 @code{Value.dereference} to the @code{gdb.Value} object corresponding
23155 to it and obtain a @code{gdb.Value} which is identical to that
23156 corresponding to @code{val}. However, if you apply the method
23157 @code{Value.referenced_value}, the result would be a @code{gdb.Value}
23158 object identical to that corresponding to @code{ptr}.
23161 py_ptrref = gdb.parse_and_eval ("ptrref")
23162 py_val = py_ptrref.dereference ()
23163 py_ptr = py_ptrref.referenced_value ()
23166 The @code{gdb.Value} object @code{py_val} is identical to that
23167 corresponding to @code{val}, and @code{py_ptr} is identical to that
23168 corresponding to @code{ptr}. In general, @code{Value.dereference} can
23169 be applied whenever the C unary operator @code{*} can be applied
23170 to the corresponding C value. For those cases where applying both
23171 @code{Value.dereference} and @code{Value.referenced_value} is allowed,
23172 the results obtained need not be identical (as we have seen in the above
23173 example). The results are however identical when applied on
23174 @code{gdb.Value} objects corresponding to pointers (@code{gdb.Value}
23175 objects with type code @code{TYPE_CODE_PTR}) in a C/C@t{++} program.
23178 @defun Value.referenced_value ()
23179 For pointer or reference data types, this method returns a new
23180 @code{gdb.Value} object corresponding to the value referenced by the
23181 pointer/reference value. For pointer data types,
23182 @code{Value.dereference} and @code{Value.referenced_value} produce
23183 identical results. The difference between these methods is that
23184 @code{Value.dereference} cannot get the values referenced by reference
23185 values. For example, consider a reference to an @code{int}, declared
23186 in your C@t{++} program as
23194 then applying @code{Value.dereference} to the @code{gdb.Value} object
23195 corresponding to @code{ref} will result in an error, while applying
23196 @code{Value.referenced_value} will result in a @code{gdb.Value} object
23197 identical to that corresponding to @code{val}.
23200 py_ref = gdb.parse_and_eval ("ref")
23201 er_ref = py_ref.dereference () # Results in error
23202 py_val = py_ref.referenced_value () # Returns the referenced value
23205 The @code{gdb.Value} object @code{py_val} is identical to that
23206 corresponding to @code{val}.
23209 @defun Value.dynamic_cast (type)
23210 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
23211 operator were used. Consult a C@t{++} reference for details.
23214 @defun Value.reinterpret_cast (type)
23215 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
23216 operator were used. Consult a C@t{++} reference for details.
23219 @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]})
23220 If this @code{gdb.Value} represents a string, then this method
23221 converts the contents to a Python string. Otherwise, this method will
23222 throw an exception.
23224 Strings are recognized in a language-specific way; whether a given
23225 @code{gdb.Value} represents a string is determined by the current
23228 For C-like languages, a value is a string if it is a pointer to or an
23229 array of characters or ints. The string is assumed to be terminated
23230 by a zero of the appropriate width. However if the optional length
23231 argument is given, the string will be converted to that given length,
23232 ignoring any embedded zeros that the string may contain.
23234 If the optional @var{encoding} argument is given, it must be a string
23235 naming the encoding of the string in the @code{gdb.Value}, such as
23236 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
23237 the same encodings as the corresponding argument to Python's
23238 @code{string.decode} method, and the Python codec machinery will be used
23239 to convert the string. If @var{encoding} is not given, or if
23240 @var{encoding} is the empty string, then either the @code{target-charset}
23241 (@pxref{Character Sets}) will be used, or a language-specific encoding
23242 will be used, if the current language is able to supply one.
23244 The optional @var{errors} argument is the same as the corresponding
23245 argument to Python's @code{string.decode} method.
23247 If the optional @var{length} argument is given, the string will be
23248 fetched and converted to the given length.
23251 @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]})
23252 If this @code{gdb.Value} represents a string, then this method
23253 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
23254 In Python}). Otherwise, this method will throw an exception.
23256 If the optional @var{encoding} argument is given, it must be a string
23257 naming the encoding of the @code{gdb.LazyString}. Some examples are:
23258 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
23259 @var{encoding} argument is an encoding that @value{GDBN} does
23260 recognize, @value{GDBN} will raise an error.
23262 When a lazy string is printed, the @value{GDBN} encoding machinery is
23263 used to convert the string during printing. If the optional
23264 @var{encoding} argument is not provided, or is an empty string,
23265 @value{GDBN} will automatically select the encoding most suitable for
23266 the string type. For further information on encoding in @value{GDBN}
23267 please see @ref{Character Sets}.
23269 If the optional @var{length} argument is given, the string will be
23270 fetched and encoded to the length of characters specified. If
23271 the @var{length} argument is not provided, the string will be fetched
23272 and encoded until a null of appropriate width is found.
23275 @defun Value.fetch_lazy ()
23276 If the @code{gdb.Value} object is currently a lazy value
23277 (@code{gdb.Value.is_lazy} is @code{True}), then the value is
23278 fetched from the inferior. Any errors that occur in the process
23279 will produce a Python exception.
23281 If the @code{gdb.Value} object is not a lazy value, this method
23284 This method does not return a value.
23289 @node Types In Python
23290 @subsubsection Types In Python
23291 @cindex types in Python
23292 @cindex Python, working with types
23295 @value{GDBN} represents types from the inferior using the class
23298 The following type-related functions are available in the @code{gdb}
23301 @findex gdb.lookup_type
23302 @defun gdb.lookup_type (name @r{[}, block@r{]})
23303 This function looks up a type by name. @var{name} is the name of the
23304 type to look up. It must be a string.
23306 If @var{block} is given, then @var{name} is looked up in that scope.
23307 Otherwise, it is searched for globally.
23309 Ordinarily, this function will return an instance of @code{gdb.Type}.
23310 If the named type cannot be found, it will throw an exception.
23313 If the type is a structure or class type, or an enum type, the fields
23314 of that type can be accessed using the Python @dfn{dictionary syntax}.
23315 For example, if @code{some_type} is a @code{gdb.Type} instance holding
23316 a structure type, you can access its @code{foo} field with:
23319 bar = some_type['foo']
23322 @code{bar} will be a @code{gdb.Field} object; see below under the
23323 description of the @code{Type.fields} method for a description of the
23324 @code{gdb.Field} class.
23326 An instance of @code{Type} has the following attributes:
23330 The type code for this type. The type code will be one of the
23331 @code{TYPE_CODE_} constants defined below.
23334 @defvar Type.sizeof
23335 The size of this type, in target @code{char} units. Usually, a
23336 target's @code{char} type will be an 8-bit byte. However, on some
23337 unusual platforms, this type may have a different size.
23341 The tag name for this type. The tag name is the name after
23342 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
23343 languages have this concept. If this type has no tag name, then
23344 @code{None} is returned.
23348 The following methods are provided:
23351 @defun Type.fields ()
23352 For structure and union types, this method returns the fields. Range
23353 types have two fields, the minimum and maximum values. Enum types
23354 have one field per enum constant. Function and method types have one
23355 field per parameter. The base types of C@t{++} classes are also
23356 represented as fields. If the type has no fields, or does not fit
23357 into one of these categories, an empty sequence will be returned.
23359 Each field is a @code{gdb.Field} object, with some pre-defined attributes:
23362 This attribute is not available for @code{static} fields (as in
23363 C@t{++} or Java). For non-@code{static} fields, the value is the bit
23364 position of the field. For @code{enum} fields, the value is the
23365 enumeration member's integer representation.
23368 The name of the field, or @code{None} for anonymous fields.
23371 This is @code{True} if the field is artificial, usually meaning that
23372 it was provided by the compiler and not the user. This attribute is
23373 always provided, and is @code{False} if the field is not artificial.
23375 @item is_base_class
23376 This is @code{True} if the field represents a base class of a C@t{++}
23377 structure. This attribute is always provided, and is @code{False}
23378 if the field is not a base class of the type that is the argument of
23379 @code{fields}, or if that type was not a C@t{++} class.
23382 If the field is packed, or is a bitfield, then this will have a
23383 non-zero value, which is the size of the field in bits. Otherwise,
23384 this will be zero; in this case the field's size is given by its type.
23387 The type of the field. This is usually an instance of @code{Type},
23388 but it can be @code{None} in some situations.
23392 @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]})
23393 Return a new @code{gdb.Type} object which represents an array of this
23394 type. If one argument is given, it is the inclusive upper bound of
23395 the array; in this case the lower bound is zero. If two arguments are
23396 given, the first argument is the lower bound of the array, and the
23397 second argument is the upper bound of the array. An array's length
23398 must not be negative, but the bounds can be.
23401 @defun Type.vector (@var{n1} @r{[}, @var{n2}@r{]})
23402 Return a new @code{gdb.Type} object which represents a vector of this
23403 type. If one argument is given, it is the inclusive upper bound of
23404 the vector; in this case the lower bound is zero. If two arguments are
23405 given, the first argument is the lower bound of the vector, and the
23406 second argument is the upper bound of the vector. A vector's length
23407 must not be negative, but the bounds can be.
23409 The difference between an @code{array} and a @code{vector} is that
23410 arrays behave like in C: when used in expressions they decay to a pointer
23411 to the first element whereas vectors are treated as first class values.
23414 @defun Type.const ()
23415 Return a new @code{gdb.Type} object which represents a
23416 @code{const}-qualified variant of this type.
23419 @defun Type.volatile ()
23420 Return a new @code{gdb.Type} object which represents a
23421 @code{volatile}-qualified variant of this type.
23424 @defun Type.unqualified ()
23425 Return a new @code{gdb.Type} object which represents an unqualified
23426 variant of this type. That is, the result is neither @code{const} nor
23430 @defun Type.range ()
23431 Return a Python @code{Tuple} object that contains two elements: the
23432 low bound of the argument type and the high bound of that type. If
23433 the type does not have a range, @value{GDBN} will raise a
23434 @code{gdb.error} exception (@pxref{Exception Handling}).
23437 @defun Type.reference ()
23438 Return a new @code{gdb.Type} object which represents a reference to this
23442 @defun Type.pointer ()
23443 Return a new @code{gdb.Type} object which represents a pointer to this
23447 @defun Type.strip_typedefs ()
23448 Return a new @code{gdb.Type} that represents the real type,
23449 after removing all layers of typedefs.
23452 @defun Type.target ()
23453 Return a new @code{gdb.Type} object which represents the target type
23456 For a pointer type, the target type is the type of the pointed-to
23457 object. For an array type (meaning C-like arrays), the target type is
23458 the type of the elements of the array. For a function or method type,
23459 the target type is the type of the return value. For a complex type,
23460 the target type is the type of the elements. For a typedef, the
23461 target type is the aliased type.
23463 If the type does not have a target, this method will throw an
23467 @defun Type.template_argument (n @r{[}, block@r{]})
23468 If this @code{gdb.Type} is an instantiation of a template, this will
23469 return a new @code{gdb.Type} which represents the type of the
23470 @var{n}th template argument.
23472 If this @code{gdb.Type} is not a template type, this will throw an
23473 exception. Ordinarily, only C@t{++} code will have template types.
23475 If @var{block} is given, then @var{name} is looked up in that scope.
23476 Otherwise, it is searched for globally.
23481 Each type has a code, which indicates what category this type falls
23482 into. The available type categories are represented by constants
23483 defined in the @code{gdb} module:
23486 @findex TYPE_CODE_PTR
23487 @findex gdb.TYPE_CODE_PTR
23488 @item gdb.TYPE_CODE_PTR
23489 The type is a pointer.
23491 @findex TYPE_CODE_ARRAY
23492 @findex gdb.TYPE_CODE_ARRAY
23493 @item gdb.TYPE_CODE_ARRAY
23494 The type is an array.
23496 @findex TYPE_CODE_STRUCT
23497 @findex gdb.TYPE_CODE_STRUCT
23498 @item gdb.TYPE_CODE_STRUCT
23499 The type is a structure.
23501 @findex TYPE_CODE_UNION
23502 @findex gdb.TYPE_CODE_UNION
23503 @item gdb.TYPE_CODE_UNION
23504 The type is a union.
23506 @findex TYPE_CODE_ENUM
23507 @findex gdb.TYPE_CODE_ENUM
23508 @item gdb.TYPE_CODE_ENUM
23509 The type is an enum.
23511 @findex TYPE_CODE_FLAGS
23512 @findex gdb.TYPE_CODE_FLAGS
23513 @item gdb.TYPE_CODE_FLAGS
23514 A bit flags type, used for things such as status registers.
23516 @findex TYPE_CODE_FUNC
23517 @findex gdb.TYPE_CODE_FUNC
23518 @item gdb.TYPE_CODE_FUNC
23519 The type is a function.
23521 @findex TYPE_CODE_INT
23522 @findex gdb.TYPE_CODE_INT
23523 @item gdb.TYPE_CODE_INT
23524 The type is an integer type.
23526 @findex TYPE_CODE_FLT
23527 @findex gdb.TYPE_CODE_FLT
23528 @item gdb.TYPE_CODE_FLT
23529 A floating point type.
23531 @findex TYPE_CODE_VOID
23532 @findex gdb.TYPE_CODE_VOID
23533 @item gdb.TYPE_CODE_VOID
23534 The special type @code{void}.
23536 @findex TYPE_CODE_SET
23537 @findex gdb.TYPE_CODE_SET
23538 @item gdb.TYPE_CODE_SET
23541 @findex TYPE_CODE_RANGE
23542 @findex gdb.TYPE_CODE_RANGE
23543 @item gdb.TYPE_CODE_RANGE
23544 A range type, that is, an integer type with bounds.
23546 @findex TYPE_CODE_STRING
23547 @findex gdb.TYPE_CODE_STRING
23548 @item gdb.TYPE_CODE_STRING
23549 A string type. Note that this is only used for certain languages with
23550 language-defined string types; C strings are not represented this way.
23552 @findex TYPE_CODE_BITSTRING
23553 @findex gdb.TYPE_CODE_BITSTRING
23554 @item gdb.TYPE_CODE_BITSTRING
23557 @findex TYPE_CODE_ERROR
23558 @findex gdb.TYPE_CODE_ERROR
23559 @item gdb.TYPE_CODE_ERROR
23560 An unknown or erroneous type.
23562 @findex TYPE_CODE_METHOD
23563 @findex gdb.TYPE_CODE_METHOD
23564 @item gdb.TYPE_CODE_METHOD
23565 A method type, as found in C@t{++} or Java.
23567 @findex TYPE_CODE_METHODPTR
23568 @findex gdb.TYPE_CODE_METHODPTR
23569 @item gdb.TYPE_CODE_METHODPTR
23570 A pointer-to-member-function.
23572 @findex TYPE_CODE_MEMBERPTR
23573 @findex gdb.TYPE_CODE_MEMBERPTR
23574 @item gdb.TYPE_CODE_MEMBERPTR
23575 A pointer-to-member.
23577 @findex TYPE_CODE_REF
23578 @findex gdb.TYPE_CODE_REF
23579 @item gdb.TYPE_CODE_REF
23582 @findex TYPE_CODE_CHAR
23583 @findex gdb.TYPE_CODE_CHAR
23584 @item gdb.TYPE_CODE_CHAR
23587 @findex TYPE_CODE_BOOL
23588 @findex gdb.TYPE_CODE_BOOL
23589 @item gdb.TYPE_CODE_BOOL
23592 @findex TYPE_CODE_COMPLEX
23593 @findex gdb.TYPE_CODE_COMPLEX
23594 @item gdb.TYPE_CODE_COMPLEX
23595 A complex float type.
23597 @findex TYPE_CODE_TYPEDEF
23598 @findex gdb.TYPE_CODE_TYPEDEF
23599 @item gdb.TYPE_CODE_TYPEDEF
23600 A typedef to some other type.
23602 @findex TYPE_CODE_NAMESPACE
23603 @findex gdb.TYPE_CODE_NAMESPACE
23604 @item gdb.TYPE_CODE_NAMESPACE
23605 A C@t{++} namespace.
23607 @findex TYPE_CODE_DECFLOAT
23608 @findex gdb.TYPE_CODE_DECFLOAT
23609 @item gdb.TYPE_CODE_DECFLOAT
23610 A decimal floating point type.
23612 @findex TYPE_CODE_INTERNAL_FUNCTION
23613 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
23614 @item gdb.TYPE_CODE_INTERNAL_FUNCTION
23615 A function internal to @value{GDBN}. This is the type used to represent
23616 convenience functions.
23619 Further support for types is provided in the @code{gdb.types}
23620 Python module (@pxref{gdb.types}).
23622 @node Pretty Printing API
23623 @subsubsection Pretty Printing API
23625 An example output is provided (@pxref{Pretty Printing}).
23627 A pretty-printer is just an object that holds a value and implements a
23628 specific interface, defined here.
23630 @defun pretty_printer.children (self)
23631 @value{GDBN} will call this method on a pretty-printer to compute the
23632 children of the pretty-printer's value.
23634 This method must return an object conforming to the Python iterator
23635 protocol. Each item returned by the iterator must be a tuple holding
23636 two elements. The first element is the ``name'' of the child; the
23637 second element is the child's value. The value can be any Python
23638 object which is convertible to a @value{GDBN} value.
23640 This method is optional. If it does not exist, @value{GDBN} will act
23641 as though the value has no children.
23644 @defun pretty_printer.display_hint (self)
23645 The CLI may call this method and use its result to change the
23646 formatting of a value. The result will also be supplied to an MI
23647 consumer as a @samp{displayhint} attribute of the variable being
23650 This method is optional. If it does exist, this method must return a
23653 Some display hints are predefined by @value{GDBN}:
23657 Indicate that the object being printed is ``array-like''. The CLI
23658 uses this to respect parameters such as @code{set print elements} and
23659 @code{set print array}.
23662 Indicate that the object being printed is ``map-like'', and that the
23663 children of this value can be assumed to alternate between keys and
23667 Indicate that the object being printed is ``string-like''. If the
23668 printer's @code{to_string} method returns a Python string of some
23669 kind, then @value{GDBN} will call its internal language-specific
23670 string-printing function to format the string. For the CLI this means
23671 adding quotation marks, possibly escaping some characters, respecting
23672 @code{set print elements}, and the like.
23676 @defun pretty_printer.to_string (self)
23677 @value{GDBN} will call this method to display the string
23678 representation of the value passed to the object's constructor.
23680 When printing from the CLI, if the @code{to_string} method exists,
23681 then @value{GDBN} will prepend its result to the values returned by
23682 @code{children}. Exactly how this formatting is done is dependent on
23683 the display hint, and may change as more hints are added. Also,
23684 depending on the print settings (@pxref{Print Settings}), the CLI may
23685 print just the result of @code{to_string} in a stack trace, omitting
23686 the result of @code{children}.
23688 If this method returns a string, it is printed verbatim.
23690 Otherwise, if this method returns an instance of @code{gdb.Value},
23691 then @value{GDBN} prints this value. This may result in a call to
23692 another pretty-printer.
23694 If instead the method returns a Python value which is convertible to a
23695 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
23696 the resulting value. Again, this may result in a call to another
23697 pretty-printer. Python scalars (integers, floats, and booleans) and
23698 strings are convertible to @code{gdb.Value}; other types are not.
23700 Finally, if this method returns @code{None} then no further operations
23701 are peformed in this method and nothing is printed.
23703 If the result is not one of these types, an exception is raised.
23706 @value{GDBN} provides a function which can be used to look up the
23707 default pretty-printer for a @code{gdb.Value}:
23709 @findex gdb.default_visualizer
23710 @defun gdb.default_visualizer (value)
23711 This function takes a @code{gdb.Value} object as an argument. If a
23712 pretty-printer for this value exists, then it is returned. If no such
23713 printer exists, then this returns @code{None}.
23716 @node Selecting Pretty-Printers
23717 @subsubsection Selecting Pretty-Printers
23719 The Python list @code{gdb.pretty_printers} contains an array of
23720 functions or callable objects that have been registered via addition
23721 as a pretty-printer. Printers in this list are called @code{global}
23722 printers, they're available when debugging all inferiors.
23723 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
23724 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
23727 Each function on these lists is passed a single @code{gdb.Value}
23728 argument and should return a pretty-printer object conforming to the
23729 interface definition above (@pxref{Pretty Printing API}). If a function
23730 cannot create a pretty-printer for the value, it should return
23733 @value{GDBN} first checks the @code{pretty_printers} attribute of each
23734 @code{gdb.Objfile} in the current program space and iteratively calls
23735 each enabled lookup routine in the list for that @code{gdb.Objfile}
23736 until it receives a pretty-printer object.
23737 If no pretty-printer is found in the objfile lists, @value{GDBN} then
23738 searches the pretty-printer list of the current program space,
23739 calling each enabled function until an object is returned.
23740 After these lists have been exhausted, it tries the global
23741 @code{gdb.pretty_printers} list, again calling each enabled function until an
23742 object is returned.
23744 The order in which the objfiles are searched is not specified. For a
23745 given list, functions are always invoked from the head of the list,
23746 and iterated over sequentially until the end of the list, or a printer
23747 object is returned.
23749 For various reasons a pretty-printer may not work.
23750 For example, the underlying data structure may have changed and
23751 the pretty-printer is out of date.
23753 The consequences of a broken pretty-printer are severe enough that
23754 @value{GDBN} provides support for enabling and disabling individual
23755 printers. For example, if @code{print frame-arguments} is on,
23756 a backtrace can become highly illegible if any argument is printed
23757 with a broken printer.
23759 Pretty-printers are enabled and disabled by attaching an @code{enabled}
23760 attribute to the registered function or callable object. If this attribute
23761 is present and its value is @code{False}, the printer is disabled, otherwise
23762 the printer is enabled.
23764 @node Writing a Pretty-Printer
23765 @subsubsection Writing a Pretty-Printer
23766 @cindex writing a pretty-printer
23768 A pretty-printer consists of two parts: a lookup function to detect
23769 if the type is supported, and the printer itself.
23771 Here is an example showing how a @code{std::string} printer might be
23772 written. @xref{Pretty Printing API}, for details on the API this class
23776 class StdStringPrinter(object):
23777 "Print a std::string"
23779 def __init__(self, val):
23782 def to_string(self):
23783 return self.val['_M_dataplus']['_M_p']
23785 def display_hint(self):
23789 And here is an example showing how a lookup function for the printer
23790 example above might be written.
23793 def str_lookup_function(val):
23794 lookup_tag = val.type.tag
23795 if lookup_tag == None:
23797 regex = re.compile("^std::basic_string<char,.*>$")
23798 if regex.match(lookup_tag):
23799 return StdStringPrinter(val)
23803 The example lookup function extracts the value's type, and attempts to
23804 match it to a type that it can pretty-print. If it is a type the
23805 printer can pretty-print, it will return a printer object. If not, it
23806 returns @code{None}.
23808 We recommend that you put your core pretty-printers into a Python
23809 package. If your pretty-printers are for use with a library, we
23810 further recommend embedding a version number into the package name.
23811 This practice will enable @value{GDBN} to load multiple versions of
23812 your pretty-printers at the same time, because they will have
23815 You should write auto-loaded code (@pxref{Python Auto-loading}) such that it
23816 can be evaluated multiple times without changing its meaning. An
23817 ideal auto-load file will consist solely of @code{import}s of your
23818 printer modules, followed by a call to a register pretty-printers with
23819 the current objfile.
23821 Taken as a whole, this approach will scale nicely to multiple
23822 inferiors, each potentially using a different library version.
23823 Embedding a version number in the Python package name will ensure that
23824 @value{GDBN} is able to load both sets of printers simultaneously.
23825 Then, because the search for pretty-printers is done by objfile, and
23826 because your auto-loaded code took care to register your library's
23827 printers with a specific objfile, @value{GDBN} will find the correct
23828 printers for the specific version of the library used by each
23831 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
23832 this code might appear in @code{gdb.libstdcxx.v6}:
23835 def register_printers(objfile):
23836 objfile.pretty_printers.append(str_lookup_function)
23840 And then the corresponding contents of the auto-load file would be:
23843 import gdb.libstdcxx.v6
23844 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
23847 The previous example illustrates a basic pretty-printer.
23848 There are a few things that can be improved on.
23849 The printer doesn't have a name, making it hard to identify in a
23850 list of installed printers. The lookup function has a name, but
23851 lookup functions can have arbitrary, even identical, names.
23853 Second, the printer only handles one type, whereas a library typically has
23854 several types. One could install a lookup function for each desired type
23855 in the library, but one could also have a single lookup function recognize
23856 several types. The latter is the conventional way this is handled.
23857 If a pretty-printer can handle multiple data types, then its
23858 @dfn{subprinters} are the printers for the individual data types.
23860 The @code{gdb.printing} module provides a formal way of solving these
23861 problems (@pxref{gdb.printing}).
23862 Here is another example that handles multiple types.
23864 These are the types we are going to pretty-print:
23867 struct foo @{ int a, b; @};
23868 struct bar @{ struct foo x, y; @};
23871 Here are the printers:
23875 """Print a foo object."""
23877 def __init__(self, val):
23880 def to_string(self):
23881 return ("a=<" + str(self.val["a"]) +
23882 "> b=<" + str(self.val["b"]) + ">")
23885 """Print a bar object."""
23887 def __init__(self, val):
23890 def to_string(self):
23891 return ("x=<" + str(self.val["x"]) +
23892 "> y=<" + str(self.val["y"]) + ">")
23895 This example doesn't need a lookup function, that is handled by the
23896 @code{gdb.printing} module. Instead a function is provided to build up
23897 the object that handles the lookup.
23900 import gdb.printing
23902 def build_pretty_printer():
23903 pp = gdb.printing.RegexpCollectionPrettyPrinter(
23905 pp.add_printer('foo', '^foo$', fooPrinter)
23906 pp.add_printer('bar', '^bar$', barPrinter)
23910 And here is the autoload support:
23913 import gdb.printing
23915 gdb.printing.register_pretty_printer(
23916 gdb.current_objfile(),
23917 my_library.build_pretty_printer())
23920 Finally, when this printer is loaded into @value{GDBN}, here is the
23921 corresponding output of @samp{info pretty-printer}:
23924 (gdb) info pretty-printer
23931 @node Inferiors In Python
23932 @subsubsection Inferiors In Python
23933 @cindex inferiors in Python
23935 @findex gdb.Inferior
23936 Programs which are being run under @value{GDBN} are called inferiors
23937 (@pxref{Inferiors and Programs}). Python scripts can access
23938 information about and manipulate inferiors controlled by @value{GDBN}
23939 via objects of the @code{gdb.Inferior} class.
23941 The following inferior-related functions are available in the @code{gdb}
23944 @defun gdb.inferiors ()
23945 Return a tuple containing all inferior objects.
23948 @defun gdb.selected_inferior ()
23949 Return an object representing the current inferior.
23952 A @code{gdb.Inferior} object has the following attributes:
23955 @defvar Inferior.num
23956 ID of inferior, as assigned by GDB.
23959 @defvar Inferior.pid
23960 Process ID of the inferior, as assigned by the underlying operating
23964 @defvar Inferior.was_attached
23965 Boolean signaling whether the inferior was created using `attach', or
23966 started by @value{GDBN} itself.
23970 A @code{gdb.Inferior} object has the following methods:
23973 @defun Inferior.is_valid ()
23974 Returns @code{True} if the @code{gdb.Inferior} object is valid,
23975 @code{False} if not. A @code{gdb.Inferior} object will become invalid
23976 if the inferior no longer exists within @value{GDBN}. All other
23977 @code{gdb.Inferior} methods will throw an exception if it is invalid
23978 at the time the method is called.
23981 @defun Inferior.threads ()
23982 This method returns a tuple holding all the threads which are valid
23983 when it is called. If there are no valid threads, the method will
23984 return an empty tuple.
23987 @findex Inferior.read_memory
23988 @defun Inferior.read_memory (address, length)
23989 Read @var{length} bytes of memory from the inferior, starting at
23990 @var{address}. Returns a buffer object, which behaves much like an array
23991 or a string. It can be modified and given to the
23992 @code{Inferior.write_memory} function.
23995 @findex Inferior.write_memory
23996 @defun Inferior.write_memory (address, buffer @r{[}, length@r{]})
23997 Write the contents of @var{buffer} to the inferior, starting at
23998 @var{address}. The @var{buffer} parameter must be a Python object
23999 which supports the buffer protocol, i.e., a string, an array or the
24000 object returned from @code{Inferior.read_memory}. If given, @var{length}
24001 determines the number of bytes from @var{buffer} to be written.
24004 @findex gdb.search_memory
24005 @defun Inferior.search_memory (address, length, pattern)
24006 Search a region of the inferior memory starting at @var{address} with
24007 the given @var{length} using the search pattern supplied in
24008 @var{pattern}. The @var{pattern} parameter must be a Python object
24009 which supports the buffer protocol, i.e., a string, an array or the
24010 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
24011 containing the address where the pattern was found, or @code{None} if
24012 the pattern could not be found.
24016 @node Events In Python
24017 @subsubsection Events In Python
24018 @cindex inferior events in Python
24020 @value{GDBN} provides a general event facility so that Python code can be
24021 notified of various state changes, particularly changes that occur in
24024 An @dfn{event} is just an object that describes some state change. The
24025 type of the object and its attributes will vary depending on the details
24026 of the change. All the existing events are described below.
24028 In order to be notified of an event, you must register an event handler
24029 with an @dfn{event registry}. An event registry is an object in the
24030 @code{gdb.events} module which dispatches particular events. A registry
24031 provides methods to register and unregister event handlers:
24034 @defun EventRegistry.connect (object)
24035 Add the given callable @var{object} to the registry. This object will be
24036 called when an event corresponding to this registry occurs.
24039 @defun EventRegistry.disconnect (object)
24040 Remove the given @var{object} from the registry. Once removed, the object
24041 will no longer receive notifications of events.
24045 Here is an example:
24048 def exit_handler (event):
24049 print "event type: exit"
24050 print "exit code: %d" % (event.exit_code)
24052 gdb.events.exited.connect (exit_handler)
24055 In the above example we connect our handler @code{exit_handler} to the
24056 registry @code{events.exited}. Once connected, @code{exit_handler} gets
24057 called when the inferior exits. The argument @dfn{event} in this example is
24058 of type @code{gdb.ExitedEvent}. As you can see in the example the
24059 @code{ExitedEvent} object has an attribute which indicates the exit code of
24062 The following is a listing of the event registries that are available and
24063 details of the events they emit:
24068 Emits @code{gdb.ThreadEvent}.
24070 Some events can be thread specific when @value{GDBN} is running in non-stop
24071 mode. When represented in Python, these events all extend
24072 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
24073 events which are emitted by this or other modules might extend this event.
24074 Examples of these events are @code{gdb.BreakpointEvent} and
24075 @code{gdb.ContinueEvent}.
24078 @defvar ThreadEvent.inferior_thread
24079 In non-stop mode this attribute will be set to the specific thread which was
24080 involved in the emitted event. Otherwise, it will be set to @code{None}.
24084 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
24086 This event indicates that the inferior has been continued after a stop. For
24087 inherited attribute refer to @code{gdb.ThreadEvent} above.
24089 @item events.exited
24090 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
24091 @code{events.ExitedEvent} has two attributes:
24093 @defvar ExitedEvent.exit_code
24094 An integer representing the exit code, if available, which the inferior
24095 has returned. (The exit code could be unavailable if, for example,
24096 @value{GDBN} detaches from the inferior.) If the exit code is unavailable,
24097 the attribute does not exist.
24099 @defvar ExitedEvent inferior
24100 A reference to the inferior which triggered the @code{exited} event.
24105 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
24107 Indicates that the inferior has stopped. All events emitted by this registry
24108 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
24109 will indicate the stopped thread when @value{GDBN} is running in non-stop
24110 mode. Refer to @code{gdb.ThreadEvent} above for more details.
24112 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
24114 This event indicates that the inferior or one of its threads has received as
24115 signal. @code{gdb.SignalEvent} has the following attributes:
24118 @defvar SignalEvent.stop_signal
24119 A string representing the signal received by the inferior. A list of possible
24120 signal values can be obtained by running the command @code{info signals} in
24121 the @value{GDBN} command prompt.
24125 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
24127 @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have
24128 been hit, and has the following attributes:
24131 @defvar BreakpointEvent.breakpoints
24132 A sequence containing references to all the breakpoints (type
24133 @code{gdb.Breakpoint}) that were hit.
24134 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
24136 @defvar BreakpointEvent.breakpoint
24137 A reference to the first breakpoint that was hit.
24138 This function is maintained for backward compatibility and is now deprecated
24139 in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute.
24143 @item events.new_objfile
24144 Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has
24145 been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute:
24148 @defvar NewObjFileEvent.new_objfile
24149 A reference to the object file (@code{gdb.Objfile}) which has been loaded.
24150 @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object.
24156 @node Threads In Python
24157 @subsubsection Threads In Python
24158 @cindex threads in python
24160 @findex gdb.InferiorThread
24161 Python scripts can access information about, and manipulate inferior threads
24162 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
24164 The following thread-related functions are available in the @code{gdb}
24167 @findex gdb.selected_thread
24168 @defun gdb.selected_thread ()
24169 This function returns the thread object for the selected thread. If there
24170 is no selected thread, this will return @code{None}.
24173 A @code{gdb.InferiorThread} object has the following attributes:
24176 @defvar InferiorThread.name
24177 The name of the thread. If the user specified a name using
24178 @code{thread name}, then this returns that name. Otherwise, if an
24179 OS-supplied name is available, then it is returned. Otherwise, this
24180 returns @code{None}.
24182 This attribute can be assigned to. The new value must be a string
24183 object, which sets the new name, or @code{None}, which removes any
24184 user-specified thread name.
24187 @defvar InferiorThread.num
24188 ID of the thread, as assigned by GDB.
24191 @defvar InferiorThread.ptid
24192 ID of the thread, as assigned by the operating system. This attribute is a
24193 tuple containing three integers. The first is the Process ID (PID); the second
24194 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
24195 Either the LWPID or TID may be 0, which indicates that the operating system
24196 does not use that identifier.
24200 A @code{gdb.InferiorThread} object has the following methods:
24203 @defun InferiorThread.is_valid ()
24204 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
24205 @code{False} if not. A @code{gdb.InferiorThread} object will become
24206 invalid if the thread exits, or the inferior that the thread belongs
24207 is deleted. All other @code{gdb.InferiorThread} methods will throw an
24208 exception if it is invalid at the time the method is called.
24211 @defun InferiorThread.switch ()
24212 This changes @value{GDBN}'s currently selected thread to the one represented
24216 @defun InferiorThread.is_stopped ()
24217 Return a Boolean indicating whether the thread is stopped.
24220 @defun InferiorThread.is_running ()
24221 Return a Boolean indicating whether the thread is running.
24224 @defun InferiorThread.is_exited ()
24225 Return a Boolean indicating whether the thread is exited.
24229 @node Commands In Python
24230 @subsubsection Commands In Python
24232 @cindex commands in python
24233 @cindex python commands
24234 You can implement new @value{GDBN} CLI commands in Python. A CLI
24235 command is implemented using an instance of the @code{gdb.Command}
24236 class, most commonly using a subclass.
24238 @defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]})
24239 The object initializer for @code{Command} registers the new command
24240 with @value{GDBN}. This initializer is normally invoked from the
24241 subclass' own @code{__init__} method.
24243 @var{name} is the name of the command. If @var{name} consists of
24244 multiple words, then the initial words are looked for as prefix
24245 commands. In this case, if one of the prefix commands does not exist,
24246 an exception is raised.
24248 There is no support for multi-line commands.
24250 @var{command_class} should be one of the @samp{COMMAND_} constants
24251 defined below. This argument tells @value{GDBN} how to categorize the
24252 new command in the help system.
24254 @var{completer_class} is an optional argument. If given, it should be
24255 one of the @samp{COMPLETE_} constants defined below. This argument
24256 tells @value{GDBN} how to perform completion for this command. If not
24257 given, @value{GDBN} will attempt to complete using the object's
24258 @code{complete} method (see below); if no such method is found, an
24259 error will occur when completion is attempted.
24261 @var{prefix} is an optional argument. If @code{True}, then the new
24262 command is a prefix command; sub-commands of this command may be
24265 The help text for the new command is taken from the Python
24266 documentation string for the command's class, if there is one. If no
24267 documentation string is provided, the default value ``This command is
24268 not documented.'' is used.
24271 @cindex don't repeat Python command
24272 @defun Command.dont_repeat ()
24273 By default, a @value{GDBN} command is repeated when the user enters a
24274 blank line at the command prompt. A command can suppress this
24275 behavior by invoking the @code{dont_repeat} method. This is similar
24276 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
24279 @defun Command.invoke (argument, from_tty)
24280 This method is called by @value{GDBN} when this command is invoked.
24282 @var{argument} is a string. It is the argument to the command, after
24283 leading and trailing whitespace has been stripped.
24285 @var{from_tty} is a boolean argument. When true, this means that the
24286 command was entered by the user at the terminal; when false it means
24287 that the command came from elsewhere.
24289 If this method throws an exception, it is turned into a @value{GDBN}
24290 @code{error} call. Otherwise, the return value is ignored.
24292 @findex gdb.string_to_argv
24293 To break @var{argument} up into an argv-like string use
24294 @code{gdb.string_to_argv}. This function behaves identically to
24295 @value{GDBN}'s internal argument lexer @code{buildargv}.
24296 It is recommended to use this for consistency.
24297 Arguments are separated by spaces and may be quoted.
24301 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
24302 ['1', '2 "3', '4 "5', "6 '7"]
24307 @cindex completion of Python commands
24308 @defun Command.complete (text, word)
24309 This method is called by @value{GDBN} when the user attempts
24310 completion on this command. All forms of completion are handled by
24311 this method, that is, the @key{TAB} and @key{M-?} key bindings
24312 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
24315 The arguments @var{text} and @var{word} are both strings. @var{text}
24316 holds the complete command line up to the cursor's location.
24317 @var{word} holds the last word of the command line; this is computed
24318 using a word-breaking heuristic.
24320 The @code{complete} method can return several values:
24323 If the return value is a sequence, the contents of the sequence are
24324 used as the completions. It is up to @code{complete} to ensure that the
24325 contents actually do complete the word. A zero-length sequence is
24326 allowed, it means that there were no completions available. Only
24327 string elements of the sequence are used; other elements in the
24328 sequence are ignored.
24331 If the return value is one of the @samp{COMPLETE_} constants defined
24332 below, then the corresponding @value{GDBN}-internal completion
24333 function is invoked, and its result is used.
24336 All other results are treated as though there were no available
24341 When a new command is registered, it must be declared as a member of
24342 some general class of commands. This is used to classify top-level
24343 commands in the on-line help system; note that prefix commands are not
24344 listed under their own category but rather that of their top-level
24345 command. The available classifications are represented by constants
24346 defined in the @code{gdb} module:
24349 @findex COMMAND_NONE
24350 @findex gdb.COMMAND_NONE
24351 @item gdb.COMMAND_NONE
24352 The command does not belong to any particular class. A command in
24353 this category will not be displayed in any of the help categories.
24355 @findex COMMAND_RUNNING
24356 @findex gdb.COMMAND_RUNNING
24357 @item gdb.COMMAND_RUNNING
24358 The command is related to running the inferior. For example,
24359 @code{start}, @code{step}, and @code{continue} are in this category.
24360 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
24361 commands in this category.
24363 @findex COMMAND_DATA
24364 @findex gdb.COMMAND_DATA
24365 @item gdb.COMMAND_DATA
24366 The command is related to data or variables. For example,
24367 @code{call}, @code{find}, and @code{print} are in this category. Type
24368 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
24371 @findex COMMAND_STACK
24372 @findex gdb.COMMAND_STACK
24373 @item gdb.COMMAND_STACK
24374 The command has to do with manipulation of the stack. For example,
24375 @code{backtrace}, @code{frame}, and @code{return} are in this
24376 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
24377 list of commands in this category.
24379 @findex COMMAND_FILES
24380 @findex gdb.COMMAND_FILES
24381 @item gdb.COMMAND_FILES
24382 This class is used for file-related commands. For example,
24383 @code{file}, @code{list} and @code{section} are in this category.
24384 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
24385 commands in this category.
24387 @findex COMMAND_SUPPORT
24388 @findex gdb.COMMAND_SUPPORT
24389 @item gdb.COMMAND_SUPPORT
24390 This should be used for ``support facilities'', generally meaning
24391 things that are useful to the user when interacting with @value{GDBN},
24392 but not related to the state of the inferior. For example,
24393 @code{help}, @code{make}, and @code{shell} are in this category. Type
24394 @kbd{help support} at the @value{GDBN} prompt to see a list of
24395 commands in this category.
24397 @findex COMMAND_STATUS
24398 @findex gdb.COMMAND_STATUS
24399 @item gdb.COMMAND_STATUS
24400 The command is an @samp{info}-related command, that is, related to the
24401 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
24402 and @code{show} are in this category. Type @kbd{help status} at the
24403 @value{GDBN} prompt to see a list of commands in this category.
24405 @findex COMMAND_BREAKPOINTS
24406 @findex gdb.COMMAND_BREAKPOINTS
24407 @item gdb.COMMAND_BREAKPOINTS
24408 The command has to do with breakpoints. For example, @code{break},
24409 @code{clear}, and @code{delete} are in this category. Type @kbd{help
24410 breakpoints} at the @value{GDBN} prompt to see a list of commands in
24413 @findex COMMAND_TRACEPOINTS
24414 @findex gdb.COMMAND_TRACEPOINTS
24415 @item gdb.COMMAND_TRACEPOINTS
24416 The command has to do with tracepoints. For example, @code{trace},
24417 @code{actions}, and @code{tfind} are in this category. Type
24418 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
24419 commands in this category.
24421 @findex COMMAND_USER
24422 @findex gdb.COMMAND_USER
24423 @item gdb.COMMAND_USER
24424 The command is a general purpose command for the user, and typically
24425 does not fit in one of the other categories.
24426 Type @kbd{help user-defined} at the @value{GDBN} prompt to see
24427 a list of commands in this category, as well as the list of gdb macros
24428 (@pxref{Sequences}).
24430 @findex COMMAND_OBSCURE
24431 @findex gdb.COMMAND_OBSCURE
24432 @item gdb.COMMAND_OBSCURE
24433 The command is only used in unusual circumstances, or is not of
24434 general interest to users. For example, @code{checkpoint},
24435 @code{fork}, and @code{stop} are in this category. Type @kbd{help
24436 obscure} at the @value{GDBN} prompt to see a list of commands in this
24439 @findex COMMAND_MAINTENANCE
24440 @findex gdb.COMMAND_MAINTENANCE
24441 @item gdb.COMMAND_MAINTENANCE
24442 The command is only useful to @value{GDBN} maintainers. The
24443 @code{maintenance} and @code{flushregs} commands are in this category.
24444 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
24445 commands in this category.
24448 A new command can use a predefined completion function, either by
24449 specifying it via an argument at initialization, or by returning it
24450 from the @code{complete} method. These predefined completion
24451 constants are all defined in the @code{gdb} module:
24454 @findex COMPLETE_NONE
24455 @findex gdb.COMPLETE_NONE
24456 @item gdb.COMPLETE_NONE
24457 This constant means that no completion should be done.
24459 @findex COMPLETE_FILENAME
24460 @findex gdb.COMPLETE_FILENAME
24461 @item gdb.COMPLETE_FILENAME
24462 This constant means that filename completion should be performed.
24464 @findex COMPLETE_LOCATION
24465 @findex gdb.COMPLETE_LOCATION
24466 @item gdb.COMPLETE_LOCATION
24467 This constant means that location completion should be done.
24468 @xref{Specify Location}.
24470 @findex COMPLETE_COMMAND
24471 @findex gdb.COMPLETE_COMMAND
24472 @item gdb.COMPLETE_COMMAND
24473 This constant means that completion should examine @value{GDBN}
24476 @findex COMPLETE_SYMBOL
24477 @findex gdb.COMPLETE_SYMBOL
24478 @item gdb.COMPLETE_SYMBOL
24479 This constant means that completion should be done using symbol names
24483 The following code snippet shows how a trivial CLI command can be
24484 implemented in Python:
24487 class HelloWorld (gdb.Command):
24488 """Greet the whole world."""
24490 def __init__ (self):
24491 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
24493 def invoke (self, arg, from_tty):
24494 print "Hello, World!"
24499 The last line instantiates the class, and is necessary to trigger the
24500 registration of the command with @value{GDBN}. Depending on how the
24501 Python code is read into @value{GDBN}, you may need to import the
24502 @code{gdb} module explicitly.
24504 @node Parameters In Python
24505 @subsubsection Parameters In Python
24507 @cindex parameters in python
24508 @cindex python parameters
24509 @tindex gdb.Parameter
24511 You can implement new @value{GDBN} parameters using Python. A new
24512 parameter is implemented as an instance of the @code{gdb.Parameter}
24515 Parameters are exposed to the user via the @code{set} and
24516 @code{show} commands. @xref{Help}.
24518 There are many parameters that already exist and can be set in
24519 @value{GDBN}. Two examples are: @code{set follow fork} and
24520 @code{set charset}. Setting these parameters influences certain
24521 behavior in @value{GDBN}. Similarly, you can define parameters that
24522 can be used to influence behavior in custom Python scripts and commands.
24524 @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]})
24525 The object initializer for @code{Parameter} registers the new
24526 parameter with @value{GDBN}. This initializer is normally invoked
24527 from the subclass' own @code{__init__} method.
24529 @var{name} is the name of the new parameter. If @var{name} consists
24530 of multiple words, then the initial words are looked for as prefix
24531 parameters. An example of this can be illustrated with the
24532 @code{set print} set of parameters. If @var{name} is
24533 @code{print foo}, then @code{print} will be searched as the prefix
24534 parameter. In this case the parameter can subsequently be accessed in
24535 @value{GDBN} as @code{set print foo}.
24537 If @var{name} consists of multiple words, and no prefix parameter group
24538 can be found, an exception is raised.
24540 @var{command-class} should be one of the @samp{COMMAND_} constants
24541 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
24542 categorize the new parameter in the help system.
24544 @var{parameter-class} should be one of the @samp{PARAM_} constants
24545 defined below. This argument tells @value{GDBN} the type of the new
24546 parameter; this information is used for input validation and
24549 If @var{parameter-class} is @code{PARAM_ENUM}, then
24550 @var{enum-sequence} must be a sequence of strings. These strings
24551 represent the possible values for the parameter.
24553 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
24554 of a fourth argument will cause an exception to be thrown.
24556 The help text for the new parameter is taken from the Python
24557 documentation string for the parameter's class, if there is one. If
24558 there is no documentation string, a default value is used.
24561 @defvar Parameter.set_doc
24562 If this attribute exists, and is a string, then its value is used as
24563 the help text for this parameter's @code{set} command. The value is
24564 examined when @code{Parameter.__init__} is invoked; subsequent changes
24568 @defvar Parameter.show_doc
24569 If this attribute exists, and is a string, then its value is used as
24570 the help text for this parameter's @code{show} command. The value is
24571 examined when @code{Parameter.__init__} is invoked; subsequent changes
24575 @defvar Parameter.value
24576 The @code{value} attribute holds the underlying value of the
24577 parameter. It can be read and assigned to just as any other
24578 attribute. @value{GDBN} does validation when assignments are made.
24581 There are two methods that should be implemented in any
24582 @code{Parameter} class. These are:
24584 @defun Parameter.get_set_string (self)
24585 @value{GDBN} will call this method when a @var{parameter}'s value has
24586 been changed via the @code{set} API (for example, @kbd{set foo off}).
24587 The @code{value} attribute has already been populated with the new
24588 value and may be used in output. This method must return a string.
24591 @defun Parameter.get_show_string (self, svalue)
24592 @value{GDBN} will call this method when a @var{parameter}'s
24593 @code{show} API has been invoked (for example, @kbd{show foo}). The
24594 argument @code{svalue} receives the string representation of the
24595 current value. This method must return a string.
24598 When a new parameter is defined, its type must be specified. The
24599 available types are represented by constants defined in the @code{gdb}
24603 @findex PARAM_BOOLEAN
24604 @findex gdb.PARAM_BOOLEAN
24605 @item gdb.PARAM_BOOLEAN
24606 The value is a plain boolean. The Python boolean values, @code{True}
24607 and @code{False} are the only valid values.
24609 @findex PARAM_AUTO_BOOLEAN
24610 @findex gdb.PARAM_AUTO_BOOLEAN
24611 @item gdb.PARAM_AUTO_BOOLEAN
24612 The value has three possible states: true, false, and @samp{auto}. In
24613 Python, true and false are represented using boolean constants, and
24614 @samp{auto} is represented using @code{None}.
24616 @findex PARAM_UINTEGER
24617 @findex gdb.PARAM_UINTEGER
24618 @item gdb.PARAM_UINTEGER
24619 The value is an unsigned integer. The value of 0 should be
24620 interpreted to mean ``unlimited''.
24622 @findex PARAM_INTEGER
24623 @findex gdb.PARAM_INTEGER
24624 @item gdb.PARAM_INTEGER
24625 The value is a signed integer. The value of 0 should be interpreted
24626 to mean ``unlimited''.
24628 @findex PARAM_STRING
24629 @findex gdb.PARAM_STRING
24630 @item gdb.PARAM_STRING
24631 The value is a string. When the user modifies the string, any escape
24632 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
24633 translated into corresponding characters and encoded into the current
24636 @findex PARAM_STRING_NOESCAPE
24637 @findex gdb.PARAM_STRING_NOESCAPE
24638 @item gdb.PARAM_STRING_NOESCAPE
24639 The value is a string. When the user modifies the string, escapes are
24640 passed through untranslated.
24642 @findex PARAM_OPTIONAL_FILENAME
24643 @findex gdb.PARAM_OPTIONAL_FILENAME
24644 @item gdb.PARAM_OPTIONAL_FILENAME
24645 The value is a either a filename (a string), or @code{None}.
24647 @findex PARAM_FILENAME
24648 @findex gdb.PARAM_FILENAME
24649 @item gdb.PARAM_FILENAME
24650 The value is a filename. This is just like
24651 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
24653 @findex PARAM_ZINTEGER
24654 @findex gdb.PARAM_ZINTEGER
24655 @item gdb.PARAM_ZINTEGER
24656 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
24657 is interpreted as itself.
24660 @findex gdb.PARAM_ENUM
24661 @item gdb.PARAM_ENUM
24662 The value is a string, which must be one of a collection string
24663 constants provided when the parameter is created.
24666 @node Functions In Python
24667 @subsubsection Writing new convenience functions
24669 @cindex writing convenience functions
24670 @cindex convenience functions in python
24671 @cindex python convenience functions
24672 @tindex gdb.Function
24674 You can implement new convenience functions (@pxref{Convenience Vars})
24675 in Python. A convenience function is an instance of a subclass of the
24676 class @code{gdb.Function}.
24678 @defun Function.__init__ (name)
24679 The initializer for @code{Function} registers the new function with
24680 @value{GDBN}. The argument @var{name} is the name of the function,
24681 a string. The function will be visible to the user as a convenience
24682 variable of type @code{internal function}, whose name is the same as
24683 the given @var{name}.
24685 The documentation for the new function is taken from the documentation
24686 string for the new class.
24689 @defun Function.invoke (@var{*args})
24690 When a convenience function is evaluated, its arguments are converted
24691 to instances of @code{gdb.Value}, and then the function's
24692 @code{invoke} method is called. Note that @value{GDBN} does not
24693 predetermine the arity of convenience functions. Instead, all
24694 available arguments are passed to @code{invoke}, following the
24695 standard Python calling convention. In particular, a convenience
24696 function can have default values for parameters without ill effect.
24698 The return value of this method is used as its value in the enclosing
24699 expression. If an ordinary Python value is returned, it is converted
24700 to a @code{gdb.Value} following the usual rules.
24703 The following code snippet shows how a trivial convenience function can
24704 be implemented in Python:
24707 class Greet (gdb.Function):
24708 """Return string to greet someone.
24709 Takes a name as argument."""
24711 def __init__ (self):
24712 super (Greet, self).__init__ ("greet")
24714 def invoke (self, name):
24715 return "Hello, %s!" % name.string ()
24720 The last line instantiates the class, and is necessary to trigger the
24721 registration of the function with @value{GDBN}. Depending on how the
24722 Python code is read into @value{GDBN}, you may need to import the
24723 @code{gdb} module explicitly.
24725 @node Progspaces In Python
24726 @subsubsection Program Spaces In Python
24728 @cindex progspaces in python
24729 @tindex gdb.Progspace
24731 A program space, or @dfn{progspace}, represents a symbolic view
24732 of an address space.
24733 It consists of all of the objfiles of the program.
24734 @xref{Objfiles In Python}.
24735 @xref{Inferiors and Programs, program spaces}, for more details
24736 about program spaces.
24738 The following progspace-related functions are available in the
24741 @findex gdb.current_progspace
24742 @defun gdb.current_progspace ()
24743 This function returns the program space of the currently selected inferior.
24744 @xref{Inferiors and Programs}.
24747 @findex gdb.progspaces
24748 @defun gdb.progspaces ()
24749 Return a sequence of all the progspaces currently known to @value{GDBN}.
24752 Each progspace is represented by an instance of the @code{gdb.Progspace}
24755 @defvar Progspace.filename
24756 The file name of the progspace as a string.
24759 @defvar Progspace.pretty_printers
24760 The @code{pretty_printers} attribute is a list of functions. It is
24761 used to look up pretty-printers. A @code{Value} is passed to each
24762 function in order; if the function returns @code{None}, then the
24763 search continues. Otherwise, the return value should be an object
24764 which is used to format the value. @xref{Pretty Printing API}, for more
24768 @node Objfiles In Python
24769 @subsubsection Objfiles In Python
24771 @cindex objfiles in python
24772 @tindex gdb.Objfile
24774 @value{GDBN} loads symbols for an inferior from various
24775 symbol-containing files (@pxref{Files}). These include the primary
24776 executable file, any shared libraries used by the inferior, and any
24777 separate debug info files (@pxref{Separate Debug Files}).
24778 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
24780 The following objfile-related functions are available in the
24783 @findex gdb.current_objfile
24784 @defun gdb.current_objfile ()
24785 When auto-loading a Python script (@pxref{Python Auto-loading}), @value{GDBN}
24786 sets the ``current objfile'' to the corresponding objfile. This
24787 function returns the current objfile. If there is no current objfile,
24788 this function returns @code{None}.
24791 @findex gdb.objfiles
24792 @defun gdb.objfiles ()
24793 Return a sequence of all the objfiles current known to @value{GDBN}.
24794 @xref{Objfiles In Python}.
24797 Each objfile is represented by an instance of the @code{gdb.Objfile}
24800 @defvar Objfile.filename
24801 The file name of the objfile as a string.
24804 @defvar Objfile.pretty_printers
24805 The @code{pretty_printers} attribute is a list of functions. It is
24806 used to look up pretty-printers. A @code{Value} is passed to each
24807 function in order; if the function returns @code{None}, then the
24808 search continues. Otherwise, the return value should be an object
24809 which is used to format the value. @xref{Pretty Printing API}, for more
24813 A @code{gdb.Objfile} object has the following methods:
24815 @defun Objfile.is_valid ()
24816 Returns @code{True} if the @code{gdb.Objfile} object is valid,
24817 @code{False} if not. A @code{gdb.Objfile} object can become invalid
24818 if the object file it refers to is not loaded in @value{GDBN} any
24819 longer. All other @code{gdb.Objfile} methods will throw an exception
24820 if it is invalid at the time the method is called.
24823 @node Frames In Python
24824 @subsubsection Accessing inferior stack frames from Python.
24826 @cindex frames in python
24827 When the debugged program stops, @value{GDBN} is able to analyze its call
24828 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
24829 represents a frame in the stack. A @code{gdb.Frame} object is only valid
24830 while its corresponding frame exists in the inferior's stack. If you try
24831 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
24832 exception (@pxref{Exception Handling}).
24834 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
24838 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
24842 The following frame-related functions are available in the @code{gdb} module:
24844 @findex gdb.selected_frame
24845 @defun gdb.selected_frame ()
24846 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
24849 @findex gdb.newest_frame
24850 @defun gdb.newest_frame ()
24851 Return the newest frame object for the selected thread.
24854 @defun gdb.frame_stop_reason_string (reason)
24855 Return a string explaining the reason why @value{GDBN} stopped unwinding
24856 frames, as expressed by the given @var{reason} code (an integer, see the
24857 @code{unwind_stop_reason} method further down in this section).
24860 A @code{gdb.Frame} object has the following methods:
24863 @defun Frame.is_valid ()
24864 Returns true if the @code{gdb.Frame} object is valid, false if not.
24865 A frame object can become invalid if the frame it refers to doesn't
24866 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
24867 an exception if it is invalid at the time the method is called.
24870 @defun Frame.name ()
24871 Returns the function name of the frame, or @code{None} if it can't be
24875 @defun Frame.type ()
24876 Returns the type of the frame. The value can be one of:
24878 @item gdb.NORMAL_FRAME
24879 An ordinary stack frame.
24881 @item gdb.DUMMY_FRAME
24882 A fake stack frame that was created by @value{GDBN} when performing an
24883 inferior function call.
24885 @item gdb.INLINE_FRAME
24886 A frame representing an inlined function. The function was inlined
24887 into a @code{gdb.NORMAL_FRAME} that is older than this one.
24889 @item gdb.TAILCALL_FRAME
24890 A frame representing a tail call. @xref{Tail Call Frames}.
24892 @item gdb.SIGTRAMP_FRAME
24893 A signal trampoline frame. This is the frame created by the OS when
24894 it calls into a signal handler.
24896 @item gdb.ARCH_FRAME
24897 A fake stack frame representing a cross-architecture call.
24899 @item gdb.SENTINEL_FRAME
24900 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
24905 @defun Frame.unwind_stop_reason ()
24906 Return an integer representing the reason why it's not possible to find
24907 more frames toward the outermost frame. Use
24908 @code{gdb.frame_stop_reason_string} to convert the value returned by this
24909 function to a string. The value can be one of:
24912 @item gdb.FRAME_UNWIND_NO_REASON
24913 No particular reason (older frames should be available).
24915 @item gdb.FRAME_UNWIND_NULL_ID
24916 The previous frame's analyzer returns an invalid result.
24918 @item gdb.FRAME_UNWIND_OUTERMOST
24919 This frame is the outermost.
24921 @item gdb.FRAME_UNWIND_UNAVAILABLE
24922 Cannot unwind further, because that would require knowing the
24923 values of registers or memory that have not been collected.
24925 @item gdb.FRAME_UNWIND_INNER_ID
24926 This frame ID looks like it ought to belong to a NEXT frame,
24927 but we got it for a PREV frame. Normally, this is a sign of
24928 unwinder failure. It could also indicate stack corruption.
24930 @item gdb.FRAME_UNWIND_SAME_ID
24931 This frame has the same ID as the previous one. That means
24932 that unwinding further would almost certainly give us another
24933 frame with exactly the same ID, so break the chain. Normally,
24934 this is a sign of unwinder failure. It could also indicate
24937 @item gdb.FRAME_UNWIND_NO_SAVED_PC
24938 The frame unwinder did not find any saved PC, but we needed
24939 one to unwind further.
24941 @item gdb.FRAME_UNWIND_FIRST_ERROR
24942 Any stop reason greater or equal to this value indicates some kind
24943 of error. This special value facilitates writing code that tests
24944 for errors in unwinding in a way that will work correctly even if
24945 the list of the other values is modified in future @value{GDBN}
24946 versions. Using it, you could write:
24948 reason = gdb.selected_frame().unwind_stop_reason ()
24949 reason_str = gdb.frame_stop_reason_string (reason)
24950 if reason >= gdb.FRAME_UNWIND_FIRST_ERROR:
24951 print "An error occured: %s" % reason_str
24958 Returns the frame's resume address.
24961 @defun Frame.block ()
24962 Return the frame's code block. @xref{Blocks In Python}.
24965 @defun Frame.function ()
24966 Return the symbol for the function corresponding to this frame.
24967 @xref{Symbols In Python}.
24970 @defun Frame.older ()
24971 Return the frame that called this frame.
24974 @defun Frame.newer ()
24975 Return the frame called by this frame.
24978 @defun Frame.find_sal ()
24979 Return the frame's symtab and line object.
24980 @xref{Symbol Tables In Python}.
24983 @defun Frame.read_var (variable @r{[}, block@r{]})
24984 Return the value of @var{variable} in this frame. If the optional
24985 argument @var{block} is provided, search for the variable from that
24986 block; otherwise start at the frame's current block (which is
24987 determined by the frame's current program counter). @var{variable}
24988 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
24989 @code{gdb.Block} object.
24992 @defun Frame.select ()
24993 Set this frame to be the selected frame. @xref{Stack, ,Examining the
24998 @node Blocks In Python
24999 @subsubsection Accessing frame blocks from Python.
25001 @cindex blocks in python
25004 Within each frame, @value{GDBN} maintains information on each block
25005 stored in that frame. These blocks are organized hierarchically, and
25006 are represented individually in Python as a @code{gdb.Block}.
25007 Please see @ref{Frames In Python}, for a more in-depth discussion on
25008 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
25009 detailed technical information on @value{GDBN}'s book-keeping of the
25012 A @code{gdb.Block} is iterable. The iterator returns the symbols
25013 (@pxref{Symbols In Python}) local to the block. Python programs
25014 should not assume that a specific block object will always contain a
25015 given symbol, since changes in @value{GDBN} features and
25016 infrastructure may cause symbols move across blocks in a symbol
25019 The following block-related functions are available in the @code{gdb}
25022 @findex gdb.block_for_pc
25023 @defun gdb.block_for_pc (pc)
25024 Return the @code{gdb.Block} containing the given @var{pc} value. If the
25025 block cannot be found for the @var{pc} value specified, the function
25026 will return @code{None}.
25029 A @code{gdb.Block} object has the following methods:
25032 @defun Block.is_valid ()
25033 Returns @code{True} if the @code{gdb.Block} object is valid,
25034 @code{False} if not. A block object can become invalid if the block it
25035 refers to doesn't exist anymore in the inferior. All other
25036 @code{gdb.Block} methods will throw an exception if it is invalid at
25037 the time the method is called. The block's validity is also checked
25038 during iteration over symbols of the block.
25042 A @code{gdb.Block} object has the following attributes:
25045 @defvar Block.start
25046 The start address of the block. This attribute is not writable.
25050 The end address of the block. This attribute is not writable.
25053 @defvar Block.function
25054 The name of the block represented as a @code{gdb.Symbol}. If the
25055 block is not named, then this attribute holds @code{None}. This
25056 attribute is not writable.
25059 @defvar Block.superblock
25060 The block containing this block. If this parent block does not exist,
25061 this attribute holds @code{None}. This attribute is not writable.
25064 @defvar Block.global_block
25065 The global block associated with this block. This attribute is not
25069 @defvar Block.static_block
25070 The static block associated with this block. This attribute is not
25074 @defvar Block.is_global
25075 @code{True} if the @code{gdb.Block} object is a global block,
25076 @code{False} if not. This attribute is not
25080 @defvar Block.is_static
25081 @code{True} if the @code{gdb.Block} object is a static block,
25082 @code{False} if not. This attribute is not writable.
25086 @node Symbols In Python
25087 @subsubsection Python representation of Symbols.
25089 @cindex symbols in python
25092 @value{GDBN} represents every variable, function and type as an
25093 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
25094 Similarly, Python represents these symbols in @value{GDBN} with the
25095 @code{gdb.Symbol} object.
25097 The following symbol-related functions are available in the @code{gdb}
25100 @findex gdb.lookup_symbol
25101 @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]})
25102 This function searches for a symbol by name. The search scope can be
25103 restricted to the parameters defined in the optional domain and block
25106 @var{name} is the name of the symbol. It must be a string. The
25107 optional @var{block} argument restricts the search to symbols visible
25108 in that @var{block}. The @var{block} argument must be a
25109 @code{gdb.Block} object. If omitted, the block for the current frame
25110 is used. The optional @var{domain} argument restricts
25111 the search to the domain type. The @var{domain} argument must be a
25112 domain constant defined in the @code{gdb} module and described later
25115 The result is a tuple of two elements.
25116 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
25118 If the symbol is found, the second element is @code{True} if the symbol
25119 is a field of a method's object (e.g., @code{this} in C@t{++}),
25120 otherwise it is @code{False}.
25121 If the symbol is not found, the second element is @code{False}.
25124 @findex gdb.lookup_global_symbol
25125 @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]})
25126 This function searches for a global symbol by name.
25127 The search scope can be restricted to by the domain argument.
25129 @var{name} is the name of the symbol. It must be a string.
25130 The optional @var{domain} argument restricts the search to the domain type.
25131 The @var{domain} argument must be a domain constant defined in the @code{gdb}
25132 module and described later in this chapter.
25134 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
25138 A @code{gdb.Symbol} object has the following attributes:
25141 @defvar Symbol.type
25142 The type of the symbol or @code{None} if no type is recorded.
25143 This attribute is represented as a @code{gdb.Type} object.
25144 @xref{Types In Python}. This attribute is not writable.
25147 @defvar Symbol.symtab
25148 The symbol table in which the symbol appears. This attribute is
25149 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
25150 Python}. This attribute is not writable.
25153 @defvar Symbol.line
25154 The line number in the source code at which the symbol was defined.
25155 This is an integer.
25158 @defvar Symbol.name
25159 The name of the symbol as a string. This attribute is not writable.
25162 @defvar Symbol.linkage_name
25163 The name of the symbol, as used by the linker (i.e., may be mangled).
25164 This attribute is not writable.
25167 @defvar Symbol.print_name
25168 The name of the symbol in a form suitable for output. This is either
25169 @code{name} or @code{linkage_name}, depending on whether the user
25170 asked @value{GDBN} to display demangled or mangled names.
25173 @defvar Symbol.addr_class
25174 The address class of the symbol. This classifies how to find the value
25175 of a symbol. Each address class is a constant defined in the
25176 @code{gdb} module and described later in this chapter.
25179 @defvar Symbol.needs_frame
25180 This is @code{True} if evaluating this symbol's value requires a frame
25181 (@pxref{Frames In Python}) and @code{False} otherwise. Typically,
25182 local variables will require a frame, but other symbols will not.
25185 @defvar Symbol.is_argument
25186 @code{True} if the symbol is an argument of a function.
25189 @defvar Symbol.is_constant
25190 @code{True} if the symbol is a constant.
25193 @defvar Symbol.is_function
25194 @code{True} if the symbol is a function or a method.
25197 @defvar Symbol.is_variable
25198 @code{True} if the symbol is a variable.
25202 A @code{gdb.Symbol} object has the following methods:
25205 @defun Symbol.is_valid ()
25206 Returns @code{True} if the @code{gdb.Symbol} object is valid,
25207 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
25208 the symbol it refers to does not exist in @value{GDBN} any longer.
25209 All other @code{gdb.Symbol} methods will throw an exception if it is
25210 invalid at the time the method is called.
25213 @defun Symbol.value (@r{[}frame@r{]})
25214 Compute the value of the symbol, as a @code{gdb.Value}. For
25215 functions, this computes the address of the function, cast to the
25216 appropriate type. If the symbol requires a frame in order to compute
25217 its value, then @var{frame} must be given. If @var{frame} is not
25218 given, or if @var{frame} is invalid, then this method will throw an
25223 The available domain categories in @code{gdb.Symbol} are represented
25224 as constants in the @code{gdb} module:
25227 @findex SYMBOL_UNDEF_DOMAIN
25228 @findex gdb.SYMBOL_UNDEF_DOMAIN
25229 @item gdb.SYMBOL_UNDEF_DOMAIN
25230 This is used when a domain has not been discovered or none of the
25231 following domains apply. This usually indicates an error either
25232 in the symbol information or in @value{GDBN}'s handling of symbols.
25233 @findex SYMBOL_VAR_DOMAIN
25234 @findex gdb.SYMBOL_VAR_DOMAIN
25235 @item gdb.SYMBOL_VAR_DOMAIN
25236 This domain contains variables, function names, typedef names and enum
25238 @findex SYMBOL_STRUCT_DOMAIN
25239 @findex gdb.SYMBOL_STRUCT_DOMAIN
25240 @item gdb.SYMBOL_STRUCT_DOMAIN
25241 This domain holds struct, union and enum type names.
25242 @findex SYMBOL_LABEL_DOMAIN
25243 @findex gdb.SYMBOL_LABEL_DOMAIN
25244 @item gdb.SYMBOL_LABEL_DOMAIN
25245 This domain contains names of labels (for gotos).
25246 @findex SYMBOL_VARIABLES_DOMAIN
25247 @findex gdb.SYMBOL_VARIABLES_DOMAIN
25248 @item gdb.SYMBOL_VARIABLES_DOMAIN
25249 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
25250 contains everything minus functions and types.
25251 @findex SYMBOL_FUNCTIONS_DOMAIN
25252 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
25253 @item gdb.SYMBOL_FUNCTION_DOMAIN
25254 This domain contains all functions.
25255 @findex SYMBOL_TYPES_DOMAIN
25256 @findex gdb.SYMBOL_TYPES_DOMAIN
25257 @item gdb.SYMBOL_TYPES_DOMAIN
25258 This domain contains all types.
25261 The available address class categories in @code{gdb.Symbol} are represented
25262 as constants in the @code{gdb} module:
25265 @findex SYMBOL_LOC_UNDEF
25266 @findex gdb.SYMBOL_LOC_UNDEF
25267 @item gdb.SYMBOL_LOC_UNDEF
25268 If this is returned by address class, it indicates an error either in
25269 the symbol information or in @value{GDBN}'s handling of symbols.
25270 @findex SYMBOL_LOC_CONST
25271 @findex gdb.SYMBOL_LOC_CONST
25272 @item gdb.SYMBOL_LOC_CONST
25273 Value is constant int.
25274 @findex SYMBOL_LOC_STATIC
25275 @findex gdb.SYMBOL_LOC_STATIC
25276 @item gdb.SYMBOL_LOC_STATIC
25277 Value is at a fixed address.
25278 @findex SYMBOL_LOC_REGISTER
25279 @findex gdb.SYMBOL_LOC_REGISTER
25280 @item gdb.SYMBOL_LOC_REGISTER
25281 Value is in a register.
25282 @findex SYMBOL_LOC_ARG
25283 @findex gdb.SYMBOL_LOC_ARG
25284 @item gdb.SYMBOL_LOC_ARG
25285 Value is an argument. This value is at the offset stored within the
25286 symbol inside the frame's argument list.
25287 @findex SYMBOL_LOC_REF_ARG
25288 @findex gdb.SYMBOL_LOC_REF_ARG
25289 @item gdb.SYMBOL_LOC_REF_ARG
25290 Value address is stored in the frame's argument list. Just like
25291 @code{LOC_ARG} except that the value's address is stored at the
25292 offset, not the value itself.
25293 @findex SYMBOL_LOC_REGPARM_ADDR
25294 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
25295 @item gdb.SYMBOL_LOC_REGPARM_ADDR
25296 Value is a specified register. Just like @code{LOC_REGISTER} except
25297 the register holds the address of the argument instead of the argument
25299 @findex SYMBOL_LOC_LOCAL
25300 @findex gdb.SYMBOL_LOC_LOCAL
25301 @item gdb.SYMBOL_LOC_LOCAL
25302 Value is a local variable.
25303 @findex SYMBOL_LOC_TYPEDEF
25304 @findex gdb.SYMBOL_LOC_TYPEDEF
25305 @item gdb.SYMBOL_LOC_TYPEDEF
25306 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
25308 @findex SYMBOL_LOC_BLOCK
25309 @findex gdb.SYMBOL_LOC_BLOCK
25310 @item gdb.SYMBOL_LOC_BLOCK
25312 @findex SYMBOL_LOC_CONST_BYTES
25313 @findex gdb.SYMBOL_LOC_CONST_BYTES
25314 @item gdb.SYMBOL_LOC_CONST_BYTES
25315 Value is a byte-sequence.
25316 @findex SYMBOL_LOC_UNRESOLVED
25317 @findex gdb.SYMBOL_LOC_UNRESOLVED
25318 @item gdb.SYMBOL_LOC_UNRESOLVED
25319 Value is at a fixed address, but the address of the variable has to be
25320 determined from the minimal symbol table whenever the variable is
25322 @findex SYMBOL_LOC_OPTIMIZED_OUT
25323 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
25324 @item gdb.SYMBOL_LOC_OPTIMIZED_OUT
25325 The value does not actually exist in the program.
25326 @findex SYMBOL_LOC_COMPUTED
25327 @findex gdb.SYMBOL_LOC_COMPUTED
25328 @item gdb.SYMBOL_LOC_COMPUTED
25329 The value's address is a computed location.
25332 @node Symbol Tables In Python
25333 @subsubsection Symbol table representation in Python.
25335 @cindex symbol tables in python
25337 @tindex gdb.Symtab_and_line
25339 Access to symbol table data maintained by @value{GDBN} on the inferior
25340 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
25341 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
25342 from the @code{find_sal} method in @code{gdb.Frame} object.
25343 @xref{Frames In Python}.
25345 For more information on @value{GDBN}'s symbol table management, see
25346 @ref{Symbols, ,Examining the Symbol Table}, for more information.
25348 A @code{gdb.Symtab_and_line} object has the following attributes:
25351 @defvar Symtab_and_line.symtab
25352 The symbol table object (@code{gdb.Symtab}) for this frame.
25353 This attribute is not writable.
25356 @defvar Symtab_and_line.pc
25357 Indicates the start of the address range occupied by code for the
25358 current source line. This attribute is not writable.
25361 @defvar Symtab_and_line.last
25362 Indicates the end of the address range occupied by code for the current
25363 source line. This attribute is not writable.
25366 @defvar Symtab_and_line.line
25367 Indicates the current line number for this object. This
25368 attribute is not writable.
25372 A @code{gdb.Symtab_and_line} object has the following methods:
25375 @defun Symtab_and_line.is_valid ()
25376 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
25377 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
25378 invalid if the Symbol table and line object it refers to does not
25379 exist in @value{GDBN} any longer. All other
25380 @code{gdb.Symtab_and_line} methods will throw an exception if it is
25381 invalid at the time the method is called.
25385 A @code{gdb.Symtab} object has the following attributes:
25388 @defvar Symtab.filename
25389 The symbol table's source filename. This attribute is not writable.
25392 @defvar Symtab.objfile
25393 The symbol table's backing object file. @xref{Objfiles In Python}.
25394 This attribute is not writable.
25398 A @code{gdb.Symtab} object has the following methods:
25401 @defun Symtab.is_valid ()
25402 Returns @code{True} if the @code{gdb.Symtab} object is valid,
25403 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
25404 the symbol table it refers to does not exist in @value{GDBN} any
25405 longer. All other @code{gdb.Symtab} methods will throw an exception
25406 if it is invalid at the time the method is called.
25409 @defun Symtab.fullname ()
25410 Return the symbol table's source absolute file name.
25413 @defun Symtab.global_block ()
25414 Return the global block of the underlying symbol table.
25415 @xref{Blocks In Python}.
25418 @defun Symtab.static_block ()
25419 Return the static block of the underlying symbol table.
25420 @xref{Blocks In Python}.
25424 @node Breakpoints In Python
25425 @subsubsection Manipulating breakpoints using Python
25427 @cindex breakpoints in python
25428 @tindex gdb.Breakpoint
25430 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
25433 @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal@r{]]]})
25434 Create a new breakpoint. @var{spec} is a string naming the
25435 location of the breakpoint, or an expression that defines a
25436 watchpoint. The contents can be any location recognized by the
25437 @code{break} command, or in the case of a watchpoint, by the @code{watch}
25438 command. The optional @var{type} denotes the breakpoint to create
25439 from the types defined later in this chapter. This argument can be
25440 either: @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type}
25441 defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal} argument
25442 allows the breakpoint to become invisible to the user. The breakpoint
25443 will neither be reported when created, nor will it be listed in the
25444 output from @code{info breakpoints} (but will be listed with the
25445 @code{maint info breakpoints} command). The optional @var{wp_class}
25446 argument defines the class of watchpoint to create, if @var{type} is
25447 @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it is
25448 assumed to be a @code{gdb.WP_WRITE} class.
25451 @defun Breakpoint.stop (self)
25452 The @code{gdb.Breakpoint} class can be sub-classed and, in
25453 particular, you may choose to implement the @code{stop} method.
25454 If this method is defined as a sub-class of @code{gdb.Breakpoint},
25455 it will be called when the inferior reaches any location of a
25456 breakpoint which instantiates that sub-class. If the method returns
25457 @code{True}, the inferior will be stopped at the location of the
25458 breakpoint, otherwise the inferior will continue.
25460 If there are multiple breakpoints at the same location with a
25461 @code{stop} method, each one will be called regardless of the
25462 return status of the previous. This ensures that all @code{stop}
25463 methods have a chance to execute at that location. In this scenario
25464 if one of the methods returns @code{True} but the others return
25465 @code{False}, the inferior will still be stopped.
25467 You should not alter the execution state of the inferior (i.e.@:, step,
25468 next, etc.), alter the current frame context (i.e.@:, change the current
25469 active frame), or alter, add or delete any breakpoint. As a general
25470 rule, you should not alter any data within @value{GDBN} or the inferior
25473 Example @code{stop} implementation:
25476 class MyBreakpoint (gdb.Breakpoint):
25478 inf_val = gdb.parse_and_eval("foo")
25485 The available watchpoint types represented by constants are defined in the
25490 @findex gdb.WP_READ
25492 Read only watchpoint.
25495 @findex gdb.WP_WRITE
25497 Write only watchpoint.
25500 @findex gdb.WP_ACCESS
25501 @item gdb.WP_ACCESS
25502 Read/Write watchpoint.
25505 @defun Breakpoint.is_valid ()
25506 Return @code{True} if this @code{Breakpoint} object is valid,
25507 @code{False} otherwise. A @code{Breakpoint} object can become invalid
25508 if the user deletes the breakpoint. In this case, the object still
25509 exists, but the underlying breakpoint does not. In the cases of
25510 watchpoint scope, the watchpoint remains valid even if execution of the
25511 inferior leaves the scope of that watchpoint.
25514 @defun Breakpoint.delete
25515 Permanently deletes the @value{GDBN} breakpoint. This also
25516 invalidates the Python @code{Breakpoint} object. Any further access
25517 to this object's attributes or methods will raise an error.
25520 @defvar Breakpoint.enabled
25521 This attribute is @code{True} if the breakpoint is enabled, and
25522 @code{False} otherwise. This attribute is writable.
25525 @defvar Breakpoint.silent
25526 This attribute is @code{True} if the breakpoint is silent, and
25527 @code{False} otherwise. This attribute is writable.
25529 Note that a breakpoint can also be silent if it has commands and the
25530 first command is @code{silent}. This is not reported by the
25531 @code{silent} attribute.
25534 @defvar Breakpoint.thread
25535 If the breakpoint is thread-specific, this attribute holds the thread
25536 id. If the breakpoint is not thread-specific, this attribute is
25537 @code{None}. This attribute is writable.
25540 @defvar Breakpoint.task
25541 If the breakpoint is Ada task-specific, this attribute holds the Ada task
25542 id. If the breakpoint is not task-specific (or the underlying
25543 language is not Ada), this attribute is @code{None}. This attribute
25547 @defvar Breakpoint.ignore_count
25548 This attribute holds the ignore count for the breakpoint, an integer.
25549 This attribute is writable.
25552 @defvar Breakpoint.number
25553 This attribute holds the breakpoint's number --- the identifier used by
25554 the user to manipulate the breakpoint. This attribute is not writable.
25557 @defvar Breakpoint.type
25558 This attribute holds the breakpoint's type --- the identifier used to
25559 determine the actual breakpoint type or use-case. This attribute is not
25563 @defvar Breakpoint.visible
25564 This attribute tells whether the breakpoint is visible to the user
25565 when set, or when the @samp{info breakpoints} command is run. This
25566 attribute is not writable.
25569 The available types are represented by constants defined in the @code{gdb}
25573 @findex BP_BREAKPOINT
25574 @findex gdb.BP_BREAKPOINT
25575 @item gdb.BP_BREAKPOINT
25576 Normal code breakpoint.
25578 @findex BP_WATCHPOINT
25579 @findex gdb.BP_WATCHPOINT
25580 @item gdb.BP_WATCHPOINT
25581 Watchpoint breakpoint.
25583 @findex BP_HARDWARE_WATCHPOINT
25584 @findex gdb.BP_HARDWARE_WATCHPOINT
25585 @item gdb.BP_HARDWARE_WATCHPOINT
25586 Hardware assisted watchpoint.
25588 @findex BP_READ_WATCHPOINT
25589 @findex gdb.BP_READ_WATCHPOINT
25590 @item gdb.BP_READ_WATCHPOINT
25591 Hardware assisted read watchpoint.
25593 @findex BP_ACCESS_WATCHPOINT
25594 @findex gdb.BP_ACCESS_WATCHPOINT
25595 @item gdb.BP_ACCESS_WATCHPOINT
25596 Hardware assisted access watchpoint.
25599 @defvar Breakpoint.hit_count
25600 This attribute holds the hit count for the breakpoint, an integer.
25601 This attribute is writable, but currently it can only be set to zero.
25604 @defvar Breakpoint.location
25605 This attribute holds the location of the breakpoint, as specified by
25606 the user. It is a string. If the breakpoint does not have a location
25607 (that is, it is a watchpoint) the attribute's value is @code{None}. This
25608 attribute is not writable.
25611 @defvar Breakpoint.expression
25612 This attribute holds a breakpoint expression, as specified by
25613 the user. It is a string. If the breakpoint does not have an
25614 expression (the breakpoint is not a watchpoint) the attribute's value
25615 is @code{None}. This attribute is not writable.
25618 @defvar Breakpoint.condition
25619 This attribute holds the condition of the breakpoint, as specified by
25620 the user. It is a string. If there is no condition, this attribute's
25621 value is @code{None}. This attribute is writable.
25624 @defvar Breakpoint.commands
25625 This attribute holds the commands attached to the breakpoint. If
25626 there are commands, this attribute's value is a string holding all the
25627 commands, separated by newlines. If there are no commands, this
25628 attribute is @code{None}. This attribute is not writable.
25631 @node Finish Breakpoints in Python
25632 @subsubsection Finish Breakpoints
25634 @cindex python finish breakpoints
25635 @tindex gdb.FinishBreakpoint
25637 A finish breakpoint is a temporary breakpoint set at the return address of
25638 a frame, based on the @code{finish} command. @code{gdb.FinishBreakpoint}
25639 extends @code{gdb.Breakpoint}. The underlying breakpoint will be disabled
25640 and deleted when the execution will run out of the breakpoint scope (i.e.@:
25641 @code{Breakpoint.stop} or @code{FinishBreakpoint.out_of_scope} triggered).
25642 Finish breakpoints are thread specific and must be create with the right
25645 @defun FinishBreakpoint.__init__ (@r{[}frame@r{]} @r{[}, internal@r{]})
25646 Create a finish breakpoint at the return address of the @code{gdb.Frame}
25647 object @var{frame}. If @var{frame} is not provided, this defaults to the
25648 newest frame. The optional @var{internal} argument allows the breakpoint to
25649 become invisible to the user. @xref{Breakpoints In Python}, for further
25650 details about this argument.
25653 @defun FinishBreakpoint.out_of_scope (self)
25654 In some circumstances (e.g.@: @code{longjmp}, C@t{++} exceptions, @value{GDBN}
25655 @code{return} command, @dots{}), a function may not properly terminate, and
25656 thus never hit the finish breakpoint. When @value{GDBN} notices such a
25657 situation, the @code{out_of_scope} callback will be triggered.
25659 You may want to sub-class @code{gdb.FinishBreakpoint} and override this
25663 class MyFinishBreakpoint (gdb.FinishBreakpoint)
25665 print "normal finish"
25668 def out_of_scope ():
25669 print "abnormal finish"
25673 @defvar FinishBreakpoint.return_value
25674 When @value{GDBN} is stopped at a finish breakpoint and the frame
25675 used to build the @code{gdb.FinishBreakpoint} object had debug symbols, this
25676 attribute will contain a @code{gdb.Value} object corresponding to the return
25677 value of the function. The value will be @code{None} if the function return
25678 type is @code{void} or if the return value was not computable. This attribute
25682 @node Lazy Strings In Python
25683 @subsubsection Python representation of lazy strings.
25685 @cindex lazy strings in python
25686 @tindex gdb.LazyString
25688 A @dfn{lazy string} is a string whose contents is not retrieved or
25689 encoded until it is needed.
25691 A @code{gdb.LazyString} is represented in @value{GDBN} as an
25692 @code{address} that points to a region of memory, an @code{encoding}
25693 that will be used to encode that region of memory, and a @code{length}
25694 to delimit the region of memory that represents the string. The
25695 difference between a @code{gdb.LazyString} and a string wrapped within
25696 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
25697 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
25698 retrieved and encoded during printing, while a @code{gdb.Value}
25699 wrapping a string is immediately retrieved and encoded on creation.
25701 A @code{gdb.LazyString} object has the following functions:
25703 @defun LazyString.value ()
25704 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
25705 will point to the string in memory, but will lose all the delayed
25706 retrieval, encoding and handling that @value{GDBN} applies to a
25707 @code{gdb.LazyString}.
25710 @defvar LazyString.address
25711 This attribute holds the address of the string. This attribute is not
25715 @defvar LazyString.length
25716 This attribute holds the length of the string in characters. If the
25717 length is -1, then the string will be fetched and encoded up to the
25718 first null of appropriate width. This attribute is not writable.
25721 @defvar LazyString.encoding
25722 This attribute holds the encoding that will be applied to the string
25723 when the string is printed by @value{GDBN}. If the encoding is not
25724 set, or contains an empty string, then @value{GDBN} will select the
25725 most appropriate encoding when the string is printed. This attribute
25729 @defvar LazyString.type
25730 This attribute holds the type that is represented by the lazy string's
25731 type. For a lazy string this will always be a pointer type. To
25732 resolve this to the lazy string's character type, use the type's
25733 @code{target} method. @xref{Types In Python}. This attribute is not
25737 @node Python Auto-loading
25738 @subsection Python Auto-loading
25739 @cindex Python auto-loading
25741 When a new object file is read (for example, due to the @code{file}
25742 command, or because the inferior has loaded a shared library),
25743 @value{GDBN} will look for Python support scripts in several ways:
25744 @file{@var{objfile}-gdb.py} (@pxref{objfile-gdb.py file})
25745 and @code{.debug_gdb_scripts} section
25746 (@pxref{dotdebug_gdb_scripts section}).
25748 The auto-loading feature is useful for supplying application-specific
25749 debugging commands and scripts.
25751 Auto-loading can be enabled or disabled,
25752 and the list of auto-loaded scripts can be printed.
25755 @anchor{set auto-load python-scripts}
25756 @kindex set auto-load python-scripts
25757 @item set auto-load python-scripts [on|off]
25758 Enable or disable the auto-loading of Python scripts.
25760 @anchor{show auto-load python-scripts}
25761 @kindex show auto-load python-scripts
25762 @item show auto-load python-scripts
25763 Show whether auto-loading of Python scripts is enabled or disabled.
25765 @anchor{info auto-load python-scripts}
25766 @kindex info auto-load python-scripts
25767 @cindex print list of auto-loaded Python scripts
25768 @item info auto-load python-scripts [@var{regexp}]
25769 Print the list of all Python scripts that @value{GDBN} auto-loaded.
25771 Also printed is the list of Python scripts that were mentioned in
25772 the @code{.debug_gdb_scripts} section and were not found
25773 (@pxref{dotdebug_gdb_scripts section}).
25774 This is useful because their names are not printed when @value{GDBN}
25775 tries to load them and fails. There may be many of them, and printing
25776 an error message for each one is problematic.
25778 If @var{regexp} is supplied only Python scripts with matching names are printed.
25783 (gdb) info auto-load python-scripts
25785 Yes py-section-script.py
25786 full name: /tmp/py-section-script.py
25787 No my-foo-pretty-printers.py
25791 When reading an auto-loaded file, @value{GDBN} sets the
25792 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
25793 function (@pxref{Objfiles In Python}). This can be useful for
25794 registering objfile-specific pretty-printers.
25797 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
25798 * dotdebug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
25799 * Which flavor to choose?::
25802 @node objfile-gdb.py file
25803 @subsubsection The @file{@var{objfile}-gdb.py} file
25804 @cindex @file{@var{objfile}-gdb.py}
25806 When a new object file is read, @value{GDBN} looks for
25807 a file named @file{@var{objfile}-gdb.py} (we call it @var{script-name} below),
25808 where @var{objfile} is the object file's real name, formed by ensuring
25809 that the file name is absolute, following all symlinks, and resolving
25810 @code{.} and @code{..} components. If this file exists and is
25811 readable, @value{GDBN} will evaluate it as a Python script.
25813 If this file does not exist, then @value{GDBN} will look for
25814 @var{script-name} file in all of the directories as specified below.
25816 Note that loading of this script file also requires accordingly configured
25817 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25820 @anchor{set auto-load scripts-directory}
25821 @kindex set auto-load scripts-directory
25822 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
25823 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
25824 may be delimited by the host platform path separator in use
25825 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
25827 Each entry here needs to be covered also by the security setting
25828 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
25830 @anchor{with-auto-load-dir}
25831 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
25832 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
25833 configuration option @option{--with-auto-load-dir}.
25835 Any reference to @file{$debugdir} will get replaced by
25836 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
25837 reference to @file{$datadir} will get replaced by @var{data-directory} which is
25838 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
25839 @file{$datadir} must be placed as a directory component --- either alone or
25840 delimited by @file{/} or @file{\} directory separators, depending on the host
25843 The list of directories uses path separator (@samp{:} on GNU and Unix
25844 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
25845 to the @env{PATH} environment variable.
25847 @anchor{show auto-load scripts-directory}
25848 @kindex show auto-load scripts-directory
25849 @item show auto-load scripts-directory
25850 Show @value{GDBN} auto-loaded scripts location.
25853 @value{GDBN} does not track which files it has already auto-loaded this way.
25854 @value{GDBN} will load the associated script every time the corresponding
25855 @var{objfile} is opened.
25856 So your @file{-gdb.py} file should be careful to avoid errors if it
25857 is evaluated more than once.
25859 @node dotdebug_gdb_scripts section
25860 @subsubsection The @code{.debug_gdb_scripts} section
25861 @cindex @code{.debug_gdb_scripts} section
25863 For systems using file formats like ELF and COFF,
25864 when @value{GDBN} loads a new object file
25865 it will look for a special section named @samp{.debug_gdb_scripts}.
25866 If this section exists, its contents is a list of names of scripts to load.
25868 @value{GDBN} will look for each specified script file first in the
25869 current directory and then along the source search path
25870 (@pxref{Source Path, ,Specifying Source Directories}),
25871 except that @file{$cdir} is not searched, since the compilation
25872 directory is not relevant to scripts.
25874 Entries can be placed in section @code{.debug_gdb_scripts} with,
25875 for example, this GCC macro:
25878 /* Note: The "MS" section flags are to remove duplicates. */
25879 #define DEFINE_GDB_SCRIPT(script_name) \
25881 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
25883 .asciz \"" script_name "\"\n\
25889 Then one can reference the macro in a header or source file like this:
25892 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
25895 The script name may include directories if desired.
25897 Note that loading of this script file also requires accordingly configured
25898 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25900 If the macro is put in a header, any application or library
25901 using this header will get a reference to the specified script.
25903 @node Which flavor to choose?
25904 @subsubsection Which flavor to choose?
25906 Given the multiple ways of auto-loading Python scripts, it might not always
25907 be clear which one to choose. This section provides some guidance.
25909 Benefits of the @file{-gdb.py} way:
25913 Can be used with file formats that don't support multiple sections.
25916 Ease of finding scripts for public libraries.
25918 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
25919 in the source search path.
25920 For publicly installed libraries, e.g., @file{libstdc++}, there typically
25921 isn't a source directory in which to find the script.
25924 Doesn't require source code additions.
25927 Benefits of the @code{.debug_gdb_scripts} way:
25931 Works with static linking.
25933 Scripts for libraries done the @file{-gdb.py} way require an objfile to
25934 trigger their loading. When an application is statically linked the only
25935 objfile available is the executable, and it is cumbersome to attach all the
25936 scripts from all the input libraries to the executable's @file{-gdb.py} script.
25939 Works with classes that are entirely inlined.
25941 Some classes can be entirely inlined, and thus there may not be an associated
25942 shared library to attach a @file{-gdb.py} script to.
25945 Scripts needn't be copied out of the source tree.
25947 In some circumstances, apps can be built out of large collections of internal
25948 libraries, and the build infrastructure necessary to install the
25949 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
25950 cumbersome. It may be easier to specify the scripts in the
25951 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
25952 top of the source tree to the source search path.
25955 @node Python modules
25956 @subsection Python modules
25957 @cindex python modules
25959 @value{GDBN} comes with several modules to assist writing Python code.
25962 * gdb.printing:: Building and registering pretty-printers.
25963 * gdb.types:: Utilities for working with types.
25964 * gdb.prompt:: Utilities for prompt value substitution.
25968 @subsubsection gdb.printing
25969 @cindex gdb.printing
25971 This module provides a collection of utilities for working with
25975 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
25976 This class specifies the API that makes @samp{info pretty-printer},
25977 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
25978 Pretty-printers should generally inherit from this class.
25980 @item SubPrettyPrinter (@var{name})
25981 For printers that handle multiple types, this class specifies the
25982 corresponding API for the subprinters.
25984 @item RegexpCollectionPrettyPrinter (@var{name})
25985 Utility class for handling multiple printers, all recognized via
25986 regular expressions.
25987 @xref{Writing a Pretty-Printer}, for an example.
25989 @item FlagEnumerationPrinter (@var{name})
25990 A pretty-printer which handles printing of @code{enum} values. Unlike
25991 @value{GDBN}'s built-in @code{enum} printing, this printer attempts to
25992 work properly when there is some overlap between the enumeration
25993 constants. @var{name} is the name of the printer and also the name of
25994 the @code{enum} type to look up.
25996 @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False)
25997 Register @var{printer} with the pretty-printer list of @var{obj}.
25998 If @var{replace} is @code{True} then any existing copy of the printer
25999 is replaced. Otherwise a @code{RuntimeError} exception is raised
26000 if a printer with the same name already exists.
26004 @subsubsection gdb.types
26007 This module provides a collection of utilities for working with
26008 @code{gdb.Types} objects.
26011 @item get_basic_type (@var{type})
26012 Return @var{type} with const and volatile qualifiers stripped,
26013 and with typedefs and C@t{++} references converted to the underlying type.
26018 typedef const int const_int;
26020 const_int& foo_ref (foo);
26021 int main () @{ return 0; @}
26028 (gdb) python import gdb.types
26029 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
26030 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
26034 @item has_field (@var{type}, @var{field})
26035 Return @code{True} if @var{type}, assumed to be a type with fields
26036 (e.g., a structure or union), has field @var{field}.
26038 @item make_enum_dict (@var{enum_type})
26039 Return a Python @code{dictionary} type produced from @var{enum_type}.
26041 @item deep_items (@var{type})
26042 Returns a Python iterator similar to the standard
26043 @code{gdb.Type.iteritems} method, except that the iterator returned
26044 by @code{deep_items} will recursively traverse anonymous struct or
26045 union fields. For example:
26059 Then in @value{GDBN}:
26061 (@value{GDBP}) python import gdb.types
26062 (@value{GDBP}) python struct_a = gdb.lookup_type("struct A")
26063 (@value{GDBP}) python print struct_a.keys ()
26065 (@value{GDBP}) python print [k for k,v in gdb.types.deep_items(struct_a)]
26066 @{['a', 'b0', 'b1']@}
26072 @subsubsection gdb.prompt
26075 This module provides a method for prompt value-substitution.
26078 @item substitute_prompt (@var{string})
26079 Return @var{string} with escape sequences substituted by values. Some
26080 escape sequences take arguments. You can specify arguments inside
26081 ``@{@}'' immediately following the escape sequence.
26083 The escape sequences you can pass to this function are:
26087 Substitute a backslash.
26089 Substitute an ESC character.
26091 Substitute the selected frame; an argument names a frame parameter.
26093 Substitute a newline.
26095 Substitute a parameter's value; the argument names the parameter.
26097 Substitute a carriage return.
26099 Substitute the selected thread; an argument names a thread parameter.
26101 Substitute the version of GDB.
26103 Substitute the current working directory.
26105 Begin a sequence of non-printing characters. These sequences are
26106 typically used with the ESC character, and are not counted in the string
26107 length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a
26108 blue-colored ``(gdb)'' prompt where the length is five.
26110 End a sequence of non-printing characters.
26116 substitute_prompt (``frame: \f,
26117 print arguments: \p@{print frame-arguments@}'')
26120 @exdent will return the string:
26123 "frame: main, print arguments: scalars"
26128 @section Creating new spellings of existing commands
26129 @cindex aliases for commands
26131 It is often useful to define alternate spellings of existing commands.
26132 For example, if a new @value{GDBN} command defined in Python has
26133 a long name to type, it is handy to have an abbreviated version of it
26134 that involves less typing.
26136 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
26137 of the @samp{step} command even though it is otherwise an ambiguous
26138 abbreviation of other commands like @samp{set} and @samp{show}.
26140 Aliases are also used to provide shortened or more common versions
26141 of multi-word commands. For example, @value{GDBN} provides the
26142 @samp{tty} alias of the @samp{set inferior-tty} command.
26144 You can define a new alias with the @samp{alias} command.
26149 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
26153 @var{ALIAS} specifies the name of the new alias.
26154 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
26157 @var{COMMAND} specifies the name of an existing command
26158 that is being aliased.
26160 The @samp{-a} option specifies that the new alias is an abbreviation
26161 of the command. Abbreviations are not shown in command
26162 lists displayed by the @samp{help} command.
26164 The @samp{--} option specifies the end of options,
26165 and is useful when @var{ALIAS} begins with a dash.
26167 Here is a simple example showing how to make an abbreviation
26168 of a command so that there is less to type.
26169 Suppose you were tired of typing @samp{disas}, the current
26170 shortest unambiguous abbreviation of the @samp{disassemble} command
26171 and you wanted an even shorter version named @samp{di}.
26172 The following will accomplish this.
26175 (gdb) alias -a di = disas
26178 Note that aliases are different from user-defined commands.
26179 With a user-defined command, you also need to write documentation
26180 for it with the @samp{document} command.
26181 An alias automatically picks up the documentation of the existing command.
26183 Here is an example where we make @samp{elms} an abbreviation of
26184 @samp{elements} in the @samp{set print elements} command.
26185 This is to show that you can make an abbreviation of any part
26189 (gdb) alias -a set print elms = set print elements
26190 (gdb) alias -a show print elms = show print elements
26191 (gdb) set p elms 20
26193 Limit on string chars or array elements to print is 200.
26196 Note that if you are defining an alias of a @samp{set} command,
26197 and you want to have an alias for the corresponding @samp{show}
26198 command, then you need to define the latter separately.
26200 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
26201 @var{ALIAS}, just as they are normally.
26204 (gdb) alias -a set pr elms = set p ele
26207 Finally, here is an example showing the creation of a one word
26208 alias for a more complex command.
26209 This creates alias @samp{spe} of the command @samp{set print elements}.
26212 (gdb) alias spe = set print elements
26217 @chapter Command Interpreters
26218 @cindex command interpreters
26220 @value{GDBN} supports multiple command interpreters, and some command
26221 infrastructure to allow users or user interface writers to switch
26222 between interpreters or run commands in other interpreters.
26224 @value{GDBN} currently supports two command interpreters, the console
26225 interpreter (sometimes called the command-line interpreter or @sc{cli})
26226 and the machine interface interpreter (or @sc{gdb/mi}). This manual
26227 describes both of these interfaces in great detail.
26229 By default, @value{GDBN} will start with the console interpreter.
26230 However, the user may choose to start @value{GDBN} with another
26231 interpreter by specifying the @option{-i} or @option{--interpreter}
26232 startup options. Defined interpreters include:
26236 @cindex console interpreter
26237 The traditional console or command-line interpreter. This is the most often
26238 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
26239 @value{GDBN} will use this interpreter.
26242 @cindex mi interpreter
26243 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
26244 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
26245 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
26249 @cindex mi2 interpreter
26250 The current @sc{gdb/mi} interface.
26253 @cindex mi1 interpreter
26254 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
26258 @cindex invoke another interpreter
26259 The interpreter being used by @value{GDBN} may not be dynamically
26260 switched at runtime. Although possible, this could lead to a very
26261 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
26262 enters the command "interpreter-set console" in a console view,
26263 @value{GDBN} would switch to using the console interpreter, rendering
26264 the IDE inoperable!
26266 @kindex interpreter-exec
26267 Although you may only choose a single interpreter at startup, you may execute
26268 commands in any interpreter from the current interpreter using the appropriate
26269 command. If you are running the console interpreter, simply use the
26270 @code{interpreter-exec} command:
26273 interpreter-exec mi "-data-list-register-names"
26276 @sc{gdb/mi} has a similar command, although it is only available in versions of
26277 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
26280 @chapter @value{GDBN} Text User Interface
26282 @cindex Text User Interface
26285 * TUI Overview:: TUI overview
26286 * TUI Keys:: TUI key bindings
26287 * TUI Single Key Mode:: TUI single key mode
26288 * TUI Commands:: TUI-specific commands
26289 * TUI Configuration:: TUI configuration variables
26292 The @value{GDBN} Text User Interface (TUI) is a terminal
26293 interface which uses the @code{curses} library to show the source
26294 file, the assembly output, the program registers and @value{GDBN}
26295 commands in separate text windows. The TUI mode is supported only
26296 on platforms where a suitable version of the @code{curses} library
26299 The TUI mode is enabled by default when you invoke @value{GDBN} as
26300 @samp{@value{GDBP} -tui}.
26301 You can also switch in and out of TUI mode while @value{GDBN} runs by
26302 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
26303 @xref{TUI Keys, ,TUI Key Bindings}.
26306 @section TUI Overview
26308 In TUI mode, @value{GDBN} can display several text windows:
26312 This window is the @value{GDBN} command window with the @value{GDBN}
26313 prompt and the @value{GDBN} output. The @value{GDBN} input is still
26314 managed using readline.
26317 The source window shows the source file of the program. The current
26318 line and active breakpoints are displayed in this window.
26321 The assembly window shows the disassembly output of the program.
26324 This window shows the processor registers. Registers are highlighted
26325 when their values change.
26328 The source and assembly windows show the current program position
26329 by highlighting the current line and marking it with a @samp{>} marker.
26330 Breakpoints are indicated with two markers. The first marker
26331 indicates the breakpoint type:
26335 Breakpoint which was hit at least once.
26338 Breakpoint which was never hit.
26341 Hardware breakpoint which was hit at least once.
26344 Hardware breakpoint which was never hit.
26347 The second marker indicates whether the breakpoint is enabled or not:
26351 Breakpoint is enabled.
26354 Breakpoint is disabled.
26357 The source, assembly and register windows are updated when the current
26358 thread changes, when the frame changes, or when the program counter
26361 These windows are not all visible at the same time. The command
26362 window is always visible. The others can be arranged in several
26373 source and assembly,
26376 source and registers, or
26379 assembly and registers.
26382 A status line above the command window shows the following information:
26386 Indicates the current @value{GDBN} target.
26387 (@pxref{Targets, ,Specifying a Debugging Target}).
26390 Gives the current process or thread number.
26391 When no process is being debugged, this field is set to @code{No process}.
26394 Gives the current function name for the selected frame.
26395 The name is demangled if demangling is turned on (@pxref{Print Settings}).
26396 When there is no symbol corresponding to the current program counter,
26397 the string @code{??} is displayed.
26400 Indicates the current line number for the selected frame.
26401 When the current line number is not known, the string @code{??} is displayed.
26404 Indicates the current program counter address.
26408 @section TUI Key Bindings
26409 @cindex TUI key bindings
26411 The TUI installs several key bindings in the readline keymaps
26412 @ifset SYSTEM_READLINE
26413 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
26415 @ifclear SYSTEM_READLINE
26416 (@pxref{Command Line Editing}).
26418 The following key bindings are installed for both TUI mode and the
26419 @value{GDBN} standard mode.
26428 Enter or leave the TUI mode. When leaving the TUI mode,
26429 the curses window management stops and @value{GDBN} operates using
26430 its standard mode, writing on the terminal directly. When reentering
26431 the TUI mode, control is given back to the curses windows.
26432 The screen is then refreshed.
26436 Use a TUI layout with only one window. The layout will
26437 either be @samp{source} or @samp{assembly}. When the TUI mode
26438 is not active, it will switch to the TUI mode.
26440 Think of this key binding as the Emacs @kbd{C-x 1} binding.
26444 Use a TUI layout with at least two windows. When the current
26445 layout already has two windows, the next layout with two windows is used.
26446 When a new layout is chosen, one window will always be common to the
26447 previous layout and the new one.
26449 Think of it as the Emacs @kbd{C-x 2} binding.
26453 Change the active window. The TUI associates several key bindings
26454 (like scrolling and arrow keys) with the active window. This command
26455 gives the focus to the next TUI window.
26457 Think of it as the Emacs @kbd{C-x o} binding.
26461 Switch in and out of the TUI SingleKey mode that binds single
26462 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
26465 The following key bindings only work in the TUI mode:
26470 Scroll the active window one page up.
26474 Scroll the active window one page down.
26478 Scroll the active window one line up.
26482 Scroll the active window one line down.
26486 Scroll the active window one column left.
26490 Scroll the active window one column right.
26494 Refresh the screen.
26497 Because the arrow keys scroll the active window in the TUI mode, they
26498 are not available for their normal use by readline unless the command
26499 window has the focus. When another window is active, you must use
26500 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
26501 and @kbd{C-f} to control the command window.
26503 @node TUI Single Key Mode
26504 @section TUI Single Key Mode
26505 @cindex TUI single key mode
26507 The TUI also provides a @dfn{SingleKey} mode, which binds several
26508 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
26509 switch into this mode, where the following key bindings are used:
26512 @kindex c @r{(SingleKey TUI key)}
26516 @kindex d @r{(SingleKey TUI key)}
26520 @kindex f @r{(SingleKey TUI key)}
26524 @kindex n @r{(SingleKey TUI key)}
26528 @kindex q @r{(SingleKey TUI key)}
26530 exit the SingleKey mode.
26532 @kindex r @r{(SingleKey TUI key)}
26536 @kindex s @r{(SingleKey TUI key)}
26540 @kindex u @r{(SingleKey TUI key)}
26544 @kindex v @r{(SingleKey TUI key)}
26548 @kindex w @r{(SingleKey TUI key)}
26553 Other keys temporarily switch to the @value{GDBN} command prompt.
26554 The key that was pressed is inserted in the editing buffer so that
26555 it is possible to type most @value{GDBN} commands without interaction
26556 with the TUI SingleKey mode. Once the command is entered the TUI
26557 SingleKey mode is restored. The only way to permanently leave
26558 this mode is by typing @kbd{q} or @kbd{C-x s}.
26562 @section TUI-specific Commands
26563 @cindex TUI commands
26565 The TUI has specific commands to control the text windows.
26566 These commands are always available, even when @value{GDBN} is not in
26567 the TUI mode. When @value{GDBN} is in the standard mode, most
26568 of these commands will automatically switch to the TUI mode.
26570 Note that if @value{GDBN}'s @code{stdout} is not connected to a
26571 terminal, or @value{GDBN} has been started with the machine interface
26572 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
26573 these commands will fail with an error, because it would not be
26574 possible or desirable to enable curses window management.
26579 List and give the size of all displayed windows.
26583 Display the next layout.
26586 Display the previous layout.
26589 Display the source window only.
26592 Display the assembly window only.
26595 Display the source and assembly window.
26598 Display the register window together with the source or assembly window.
26602 Make the next window active for scrolling.
26605 Make the previous window active for scrolling.
26608 Make the source window active for scrolling.
26611 Make the assembly window active for scrolling.
26614 Make the register window active for scrolling.
26617 Make the command window active for scrolling.
26621 Refresh the screen. This is similar to typing @kbd{C-L}.
26623 @item tui reg float
26625 Show the floating point registers in the register window.
26627 @item tui reg general
26628 Show the general registers in the register window.
26631 Show the next register group. The list of register groups as well as
26632 their order is target specific. The predefined register groups are the
26633 following: @code{general}, @code{float}, @code{system}, @code{vector},
26634 @code{all}, @code{save}, @code{restore}.
26636 @item tui reg system
26637 Show the system registers in the register window.
26641 Update the source window and the current execution point.
26643 @item winheight @var{name} +@var{count}
26644 @itemx winheight @var{name} -@var{count}
26646 Change the height of the window @var{name} by @var{count}
26647 lines. Positive counts increase the height, while negative counts
26650 @item tabset @var{nchars}
26652 Set the width of tab stops to be @var{nchars} characters.
26655 @node TUI Configuration
26656 @section TUI Configuration Variables
26657 @cindex TUI configuration variables
26659 Several configuration variables control the appearance of TUI windows.
26662 @item set tui border-kind @var{kind}
26663 @kindex set tui border-kind
26664 Select the border appearance for the source, assembly and register windows.
26665 The possible values are the following:
26668 Use a space character to draw the border.
26671 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
26674 Use the Alternate Character Set to draw the border. The border is
26675 drawn using character line graphics if the terminal supports them.
26678 @item set tui border-mode @var{mode}
26679 @kindex set tui border-mode
26680 @itemx set tui active-border-mode @var{mode}
26681 @kindex set tui active-border-mode
26682 Select the display attributes for the borders of the inactive windows
26683 or the active window. The @var{mode} can be one of the following:
26686 Use normal attributes to display the border.
26692 Use reverse video mode.
26695 Use half bright mode.
26697 @item half-standout
26698 Use half bright and standout mode.
26701 Use extra bright or bold mode.
26703 @item bold-standout
26704 Use extra bright or bold and standout mode.
26709 @chapter Using @value{GDBN} under @sc{gnu} Emacs
26712 @cindex @sc{gnu} Emacs
26713 A special interface allows you to use @sc{gnu} Emacs to view (and
26714 edit) the source files for the program you are debugging with
26717 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
26718 executable file you want to debug as an argument. This command starts
26719 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
26720 created Emacs buffer.
26721 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
26723 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
26728 All ``terminal'' input and output goes through an Emacs buffer, called
26731 This applies both to @value{GDBN} commands and their output, and to the input
26732 and output done by the program you are debugging.
26734 This is useful because it means that you can copy the text of previous
26735 commands and input them again; you can even use parts of the output
26738 All the facilities of Emacs' Shell mode are available for interacting
26739 with your program. In particular, you can send signals the usual
26740 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
26744 @value{GDBN} displays source code through Emacs.
26746 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
26747 source file for that frame and puts an arrow (@samp{=>}) at the
26748 left margin of the current line. Emacs uses a separate buffer for
26749 source display, and splits the screen to show both your @value{GDBN} session
26752 Explicit @value{GDBN} @code{list} or search commands still produce output as
26753 usual, but you probably have no reason to use them from Emacs.
26756 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
26757 a graphical mode, enabled by default, which provides further buffers
26758 that can control the execution and describe the state of your program.
26759 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
26761 If you specify an absolute file name when prompted for the @kbd{M-x
26762 gdb} argument, then Emacs sets your current working directory to where
26763 your program resides. If you only specify the file name, then Emacs
26764 sets your current working directory to the directory associated
26765 with the previous buffer. In this case, @value{GDBN} may find your
26766 program by searching your environment's @code{PATH} variable, but on
26767 some operating systems it might not find the source. So, although the
26768 @value{GDBN} input and output session proceeds normally, the auxiliary
26769 buffer does not display the current source and line of execution.
26771 The initial working directory of @value{GDBN} is printed on the top
26772 line of the GUD buffer and this serves as a default for the commands
26773 that specify files for @value{GDBN} to operate on. @xref{Files,
26774 ,Commands to Specify Files}.
26776 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
26777 need to call @value{GDBN} by a different name (for example, if you
26778 keep several configurations around, with different names) you can
26779 customize the Emacs variable @code{gud-gdb-command-name} to run the
26782 In the GUD buffer, you can use these special Emacs commands in
26783 addition to the standard Shell mode commands:
26787 Describe the features of Emacs' GUD Mode.
26790 Execute to another source line, like the @value{GDBN} @code{step} command; also
26791 update the display window to show the current file and location.
26794 Execute to next source line in this function, skipping all function
26795 calls, like the @value{GDBN} @code{next} command. Then update the display window
26796 to show the current file and location.
26799 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
26800 display window accordingly.
26803 Execute until exit from the selected stack frame, like the @value{GDBN}
26804 @code{finish} command.
26807 Continue execution of your program, like the @value{GDBN} @code{continue}
26811 Go up the number of frames indicated by the numeric argument
26812 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
26813 like the @value{GDBN} @code{up} command.
26816 Go down the number of frames indicated by the numeric argument, like the
26817 @value{GDBN} @code{down} command.
26820 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
26821 tells @value{GDBN} to set a breakpoint on the source line point is on.
26823 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
26824 separate frame which shows a backtrace when the GUD buffer is current.
26825 Move point to any frame in the stack and type @key{RET} to make it
26826 become the current frame and display the associated source in the
26827 source buffer. Alternatively, click @kbd{Mouse-2} to make the
26828 selected frame become the current one. In graphical mode, the
26829 speedbar displays watch expressions.
26831 If you accidentally delete the source-display buffer, an easy way to get
26832 it back is to type the command @code{f} in the @value{GDBN} buffer, to
26833 request a frame display; when you run under Emacs, this recreates
26834 the source buffer if necessary to show you the context of the current
26837 The source files displayed in Emacs are in ordinary Emacs buffers
26838 which are visiting the source files in the usual way. You can edit
26839 the files with these buffers if you wish; but keep in mind that @value{GDBN}
26840 communicates with Emacs in terms of line numbers. If you add or
26841 delete lines from the text, the line numbers that @value{GDBN} knows cease
26842 to correspond properly with the code.
26844 A more detailed description of Emacs' interaction with @value{GDBN} is
26845 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
26848 @c The following dropped because Epoch is nonstandard. Reactivate
26849 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
26851 @kindex Emacs Epoch environment
26855 Version 18 of @sc{gnu} Emacs has a built-in window system
26856 called the @code{epoch}
26857 environment. Users of this environment can use a new command,
26858 @code{inspect} which performs identically to @code{print} except that
26859 each value is printed in its own window.
26864 @chapter The @sc{gdb/mi} Interface
26866 @unnumberedsec Function and Purpose
26868 @cindex @sc{gdb/mi}, its purpose
26869 @sc{gdb/mi} is a line based machine oriented text interface to
26870 @value{GDBN} and is activated by specifying using the
26871 @option{--interpreter} command line option (@pxref{Mode Options}). It
26872 is specifically intended to support the development of systems which
26873 use the debugger as just one small component of a larger system.
26875 This chapter is a specification of the @sc{gdb/mi} interface. It is written
26876 in the form of a reference manual.
26878 Note that @sc{gdb/mi} is still under construction, so some of the
26879 features described below are incomplete and subject to change
26880 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
26882 @unnumberedsec Notation and Terminology
26884 @cindex notational conventions, for @sc{gdb/mi}
26885 This chapter uses the following notation:
26889 @code{|} separates two alternatives.
26892 @code{[ @var{something} ]} indicates that @var{something} is optional:
26893 it may or may not be given.
26896 @code{( @var{group} )*} means that @var{group} inside the parentheses
26897 may repeat zero or more times.
26900 @code{( @var{group} )+} means that @var{group} inside the parentheses
26901 may repeat one or more times.
26904 @code{"@var{string}"} means a literal @var{string}.
26908 @heading Dependencies
26912 * GDB/MI General Design::
26913 * GDB/MI Command Syntax::
26914 * GDB/MI Compatibility with CLI::
26915 * GDB/MI Development and Front Ends::
26916 * GDB/MI Output Records::
26917 * GDB/MI Simple Examples::
26918 * GDB/MI Command Description Format::
26919 * GDB/MI Breakpoint Commands::
26920 * GDB/MI Program Context::
26921 * GDB/MI Thread Commands::
26922 * GDB/MI Ada Tasking Commands::
26923 * GDB/MI Program Execution::
26924 * GDB/MI Stack Manipulation::
26925 * GDB/MI Variable Objects::
26926 * GDB/MI Data Manipulation::
26927 * GDB/MI Tracepoint Commands::
26928 * GDB/MI Symbol Query::
26929 * GDB/MI File Commands::
26931 * GDB/MI Kod Commands::
26932 * GDB/MI Memory Overlay Commands::
26933 * GDB/MI Signal Handling Commands::
26935 * GDB/MI Target Manipulation::
26936 * GDB/MI File Transfer Commands::
26937 * GDB/MI Miscellaneous Commands::
26940 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26941 @node GDB/MI General Design
26942 @section @sc{gdb/mi} General Design
26943 @cindex GDB/MI General Design
26945 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
26946 parts---commands sent to @value{GDBN}, responses to those commands
26947 and notifications. Each command results in exactly one response,
26948 indicating either successful completion of the command, or an error.
26949 For the commands that do not resume the target, the response contains the
26950 requested information. For the commands that resume the target, the
26951 response only indicates whether the target was successfully resumed.
26952 Notifications is the mechanism for reporting changes in the state of the
26953 target, or in @value{GDBN} state, that cannot conveniently be associated with
26954 a command and reported as part of that command response.
26956 The important examples of notifications are:
26960 Exec notifications. These are used to report changes in
26961 target state---when a target is resumed, or stopped. It would not
26962 be feasible to include this information in response of resuming
26963 commands, because one resume commands can result in multiple events in
26964 different threads. Also, quite some time may pass before any event
26965 happens in the target, while a frontend needs to know whether the resuming
26966 command itself was successfully executed.
26969 Console output, and status notifications. Console output
26970 notifications are used to report output of CLI commands, as well as
26971 diagnostics for other commands. Status notifications are used to
26972 report the progress of a long-running operation. Naturally, including
26973 this information in command response would mean no output is produced
26974 until the command is finished, which is undesirable.
26977 General notifications. Commands may have various side effects on
26978 the @value{GDBN} or target state beyond their official purpose. For example,
26979 a command may change the selected thread. Although such changes can
26980 be included in command response, using notification allows for more
26981 orthogonal frontend design.
26985 There's no guarantee that whenever an MI command reports an error,
26986 @value{GDBN} or the target are in any specific state, and especially,
26987 the state is not reverted to the state before the MI command was
26988 processed. Therefore, whenever an MI command results in an error,
26989 we recommend that the frontend refreshes all the information shown in
26990 the user interface.
26994 * Context management::
26995 * Asynchronous and non-stop modes::
26999 @node Context management
27000 @subsection Context management
27002 In most cases when @value{GDBN} accesses the target, this access is
27003 done in context of a specific thread and frame (@pxref{Frames}).
27004 Often, even when accessing global data, the target requires that a thread
27005 be specified. The CLI interface maintains the selected thread and frame,
27006 and supplies them to target on each command. This is convenient,
27007 because a command line user would not want to specify that information
27008 explicitly on each command, and because user interacts with
27009 @value{GDBN} via a single terminal, so no confusion is possible as
27010 to what thread and frame are the current ones.
27012 In the case of MI, the concept of selected thread and frame is less
27013 useful. First, a frontend can easily remember this information
27014 itself. Second, a graphical frontend can have more than one window,
27015 each one used for debugging a different thread, and the frontend might
27016 want to access additional threads for internal purposes. This
27017 increases the risk that by relying on implicitly selected thread, the
27018 frontend may be operating on a wrong one. Therefore, each MI command
27019 should explicitly specify which thread and frame to operate on. To
27020 make it possible, each MI command accepts the @samp{--thread} and
27021 @samp{--frame} options, the value to each is @value{GDBN} identifier
27022 for thread and frame to operate on.
27024 Usually, each top-level window in a frontend allows the user to select
27025 a thread and a frame, and remembers the user selection for further
27026 operations. However, in some cases @value{GDBN} may suggest that the
27027 current thread be changed. For example, when stopping on a breakpoint
27028 it is reasonable to switch to the thread where breakpoint is hit. For
27029 another example, if the user issues the CLI @samp{thread} command via
27030 the frontend, it is desirable to change the frontend's selected thread to the
27031 one specified by user. @value{GDBN} communicates the suggestion to
27032 change current thread using the @samp{=thread-selected} notification.
27033 No such notification is available for the selected frame at the moment.
27035 Note that historically, MI shares the selected thread with CLI, so
27036 frontends used the @code{-thread-select} to execute commands in the
27037 right context. However, getting this to work right is cumbersome. The
27038 simplest way is for frontend to emit @code{-thread-select} command
27039 before every command. This doubles the number of commands that need
27040 to be sent. The alternative approach is to suppress @code{-thread-select}
27041 if the selected thread in @value{GDBN} is supposed to be identical to the
27042 thread the frontend wants to operate on. However, getting this
27043 optimization right can be tricky. In particular, if the frontend
27044 sends several commands to @value{GDBN}, and one of the commands changes the
27045 selected thread, then the behaviour of subsequent commands will
27046 change. So, a frontend should either wait for response from such
27047 problematic commands, or explicitly add @code{-thread-select} for
27048 all subsequent commands. No frontend is known to do this exactly
27049 right, so it is suggested to just always pass the @samp{--thread} and
27050 @samp{--frame} options.
27052 @node Asynchronous and non-stop modes
27053 @subsection Asynchronous command execution and non-stop mode
27055 On some targets, @value{GDBN} is capable of processing MI commands
27056 even while the target is running. This is called @dfn{asynchronous
27057 command execution} (@pxref{Background Execution}). The frontend may
27058 specify a preferrence for asynchronous execution using the
27059 @code{-gdb-set target-async 1} command, which should be emitted before
27060 either running the executable or attaching to the target. After the
27061 frontend has started the executable or attached to the target, it can
27062 find if asynchronous execution is enabled using the
27063 @code{-list-target-features} command.
27065 Even if @value{GDBN} can accept a command while target is running,
27066 many commands that access the target do not work when the target is
27067 running. Therefore, asynchronous command execution is most useful
27068 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
27069 it is possible to examine the state of one thread, while other threads
27072 When a given thread is running, MI commands that try to access the
27073 target in the context of that thread may not work, or may work only on
27074 some targets. In particular, commands that try to operate on thread's
27075 stack will not work, on any target. Commands that read memory, or
27076 modify breakpoints, may work or not work, depending on the target. Note
27077 that even commands that operate on global state, such as @code{print},
27078 @code{set}, and breakpoint commands, still access the target in the
27079 context of a specific thread, so frontend should try to find a
27080 stopped thread and perform the operation on that thread (using the
27081 @samp{--thread} option).
27083 Which commands will work in the context of a running thread is
27084 highly target dependent. However, the two commands
27085 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
27086 to find the state of a thread, will always work.
27088 @node Thread groups
27089 @subsection Thread groups
27090 @value{GDBN} may be used to debug several processes at the same time.
27091 On some platfroms, @value{GDBN} may support debugging of several
27092 hardware systems, each one having several cores with several different
27093 processes running on each core. This section describes the MI
27094 mechanism to support such debugging scenarios.
27096 The key observation is that regardless of the structure of the
27097 target, MI can have a global list of threads, because most commands that
27098 accept the @samp{--thread} option do not need to know what process that
27099 thread belongs to. Therefore, it is not necessary to introduce
27100 neither additional @samp{--process} option, nor an notion of the
27101 current process in the MI interface. The only strictly new feature
27102 that is required is the ability to find how the threads are grouped
27105 To allow the user to discover such grouping, and to support arbitrary
27106 hierarchy of machines/cores/processes, MI introduces the concept of a
27107 @dfn{thread group}. Thread group is a collection of threads and other
27108 thread groups. A thread group always has a string identifier, a type,
27109 and may have additional attributes specific to the type. A new
27110 command, @code{-list-thread-groups}, returns the list of top-level
27111 thread groups, which correspond to processes that @value{GDBN} is
27112 debugging at the moment. By passing an identifier of a thread group
27113 to the @code{-list-thread-groups} command, it is possible to obtain
27114 the members of specific thread group.
27116 To allow the user to easily discover processes, and other objects, he
27117 wishes to debug, a concept of @dfn{available thread group} is
27118 introduced. Available thread group is an thread group that
27119 @value{GDBN} is not debugging, but that can be attached to, using the
27120 @code{-target-attach} command. The list of available top-level thread
27121 groups can be obtained using @samp{-list-thread-groups --available}.
27122 In general, the content of a thread group may be only retrieved only
27123 after attaching to that thread group.
27125 Thread groups are related to inferiors (@pxref{Inferiors and
27126 Programs}). Each inferior corresponds to a thread group of a special
27127 type @samp{process}, and some additional operations are permitted on
27128 such thread groups.
27130 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27131 @node GDB/MI Command Syntax
27132 @section @sc{gdb/mi} Command Syntax
27135 * GDB/MI Input Syntax::
27136 * GDB/MI Output Syntax::
27139 @node GDB/MI Input Syntax
27140 @subsection @sc{gdb/mi} Input Syntax
27142 @cindex input syntax for @sc{gdb/mi}
27143 @cindex @sc{gdb/mi}, input syntax
27145 @item @var{command} @expansion{}
27146 @code{@var{cli-command} | @var{mi-command}}
27148 @item @var{cli-command} @expansion{}
27149 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
27150 @var{cli-command} is any existing @value{GDBN} CLI command.
27152 @item @var{mi-command} @expansion{}
27153 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
27154 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
27156 @item @var{token} @expansion{}
27157 "any sequence of digits"
27159 @item @var{option} @expansion{}
27160 @code{"-" @var{parameter} [ " " @var{parameter} ]}
27162 @item @var{parameter} @expansion{}
27163 @code{@var{non-blank-sequence} | @var{c-string}}
27165 @item @var{operation} @expansion{}
27166 @emph{any of the operations described in this chapter}
27168 @item @var{non-blank-sequence} @expansion{}
27169 @emph{anything, provided it doesn't contain special characters such as
27170 "-", @var{nl}, """ and of course " "}
27172 @item @var{c-string} @expansion{}
27173 @code{""" @var{seven-bit-iso-c-string-content} """}
27175 @item @var{nl} @expansion{}
27184 The CLI commands are still handled by the @sc{mi} interpreter; their
27185 output is described below.
27188 The @code{@var{token}}, when present, is passed back when the command
27192 Some @sc{mi} commands accept optional arguments as part of the parameter
27193 list. Each option is identified by a leading @samp{-} (dash) and may be
27194 followed by an optional argument parameter. Options occur first in the
27195 parameter list and can be delimited from normal parameters using
27196 @samp{--} (this is useful when some parameters begin with a dash).
27203 We want easy access to the existing CLI syntax (for debugging).
27206 We want it to be easy to spot a @sc{mi} operation.
27209 @node GDB/MI Output Syntax
27210 @subsection @sc{gdb/mi} Output Syntax
27212 @cindex output syntax of @sc{gdb/mi}
27213 @cindex @sc{gdb/mi}, output syntax
27214 The output from @sc{gdb/mi} consists of zero or more out-of-band records
27215 followed, optionally, by a single result record. This result record
27216 is for the most recent command. The sequence of output records is
27217 terminated by @samp{(gdb)}.
27219 If an input command was prefixed with a @code{@var{token}} then the
27220 corresponding output for that command will also be prefixed by that same
27224 @item @var{output} @expansion{}
27225 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
27227 @item @var{result-record} @expansion{}
27228 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
27230 @item @var{out-of-band-record} @expansion{}
27231 @code{@var{async-record} | @var{stream-record}}
27233 @item @var{async-record} @expansion{}
27234 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
27236 @item @var{exec-async-output} @expansion{}
27237 @code{[ @var{token} ] "*" @var{async-output}}
27239 @item @var{status-async-output} @expansion{}
27240 @code{[ @var{token} ] "+" @var{async-output}}
27242 @item @var{notify-async-output} @expansion{}
27243 @code{[ @var{token} ] "=" @var{async-output}}
27245 @item @var{async-output} @expansion{}
27246 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
27248 @item @var{result-class} @expansion{}
27249 @code{"done" | "running" | "connected" | "error" | "exit"}
27251 @item @var{async-class} @expansion{}
27252 @code{"stopped" | @var{others}} (where @var{others} will be added
27253 depending on the needs---this is still in development).
27255 @item @var{result} @expansion{}
27256 @code{ @var{variable} "=" @var{value}}
27258 @item @var{variable} @expansion{}
27259 @code{ @var{string} }
27261 @item @var{value} @expansion{}
27262 @code{ @var{const} | @var{tuple} | @var{list} }
27264 @item @var{const} @expansion{}
27265 @code{@var{c-string}}
27267 @item @var{tuple} @expansion{}
27268 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
27270 @item @var{list} @expansion{}
27271 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
27272 @var{result} ( "," @var{result} )* "]" }
27274 @item @var{stream-record} @expansion{}
27275 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
27277 @item @var{console-stream-output} @expansion{}
27278 @code{"~" @var{c-string}}
27280 @item @var{target-stream-output} @expansion{}
27281 @code{"@@" @var{c-string}}
27283 @item @var{log-stream-output} @expansion{}
27284 @code{"&" @var{c-string}}
27286 @item @var{nl} @expansion{}
27289 @item @var{token} @expansion{}
27290 @emph{any sequence of digits}.
27298 All output sequences end in a single line containing a period.
27301 The @code{@var{token}} is from the corresponding request. Note that
27302 for all async output, while the token is allowed by the grammar and
27303 may be output by future versions of @value{GDBN} for select async
27304 output messages, it is generally omitted. Frontends should treat
27305 all async output as reporting general changes in the state of the
27306 target and there should be no need to associate async output to any
27310 @cindex status output in @sc{gdb/mi}
27311 @var{status-async-output} contains on-going status information about the
27312 progress of a slow operation. It can be discarded. All status output is
27313 prefixed by @samp{+}.
27316 @cindex async output in @sc{gdb/mi}
27317 @var{exec-async-output} contains asynchronous state change on the target
27318 (stopped, started, disappeared). All async output is prefixed by
27322 @cindex notify output in @sc{gdb/mi}
27323 @var{notify-async-output} contains supplementary information that the
27324 client should handle (e.g., a new breakpoint information). All notify
27325 output is prefixed by @samp{=}.
27328 @cindex console output in @sc{gdb/mi}
27329 @var{console-stream-output} is output that should be displayed as is in the
27330 console. It is the textual response to a CLI command. All the console
27331 output is prefixed by @samp{~}.
27334 @cindex target output in @sc{gdb/mi}
27335 @var{target-stream-output} is the output produced by the target program.
27336 All the target output is prefixed by @samp{@@}.
27339 @cindex log output in @sc{gdb/mi}
27340 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
27341 instance messages that should be displayed as part of an error log. All
27342 the log output is prefixed by @samp{&}.
27345 @cindex list output in @sc{gdb/mi}
27346 New @sc{gdb/mi} commands should only output @var{lists} containing
27352 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
27353 details about the various output records.
27355 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27356 @node GDB/MI Compatibility with CLI
27357 @section @sc{gdb/mi} Compatibility with CLI
27359 @cindex compatibility, @sc{gdb/mi} and CLI
27360 @cindex @sc{gdb/mi}, compatibility with CLI
27362 For the developers convenience CLI commands can be entered directly,
27363 but there may be some unexpected behaviour. For example, commands
27364 that query the user will behave as if the user replied yes, breakpoint
27365 command lists are not executed and some CLI commands, such as
27366 @code{if}, @code{when} and @code{define}, prompt for further input with
27367 @samp{>}, which is not valid MI output.
27369 This feature may be removed at some stage in the future and it is
27370 recommended that front ends use the @code{-interpreter-exec} command
27371 (@pxref{-interpreter-exec}).
27373 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27374 @node GDB/MI Development and Front Ends
27375 @section @sc{gdb/mi} Development and Front Ends
27376 @cindex @sc{gdb/mi} development
27378 The application which takes the MI output and presents the state of the
27379 program being debugged to the user is called a @dfn{front end}.
27381 Although @sc{gdb/mi} is still incomplete, it is currently being used
27382 by a variety of front ends to @value{GDBN}. This makes it difficult
27383 to introduce new functionality without breaking existing usage. This
27384 section tries to minimize the problems by describing how the protocol
27387 Some changes in MI need not break a carefully designed front end, and
27388 for these the MI version will remain unchanged. The following is a
27389 list of changes that may occur within one level, so front ends should
27390 parse MI output in a way that can handle them:
27394 New MI commands may be added.
27397 New fields may be added to the output of any MI command.
27400 The range of values for fields with specified values, e.g.,
27401 @code{in_scope} (@pxref{-var-update}) may be extended.
27403 @c The format of field's content e.g type prefix, may change so parse it
27404 @c at your own risk. Yes, in general?
27406 @c The order of fields may change? Shouldn't really matter but it might
27407 @c resolve inconsistencies.
27410 If the changes are likely to break front ends, the MI version level
27411 will be increased by one. This will allow the front end to parse the
27412 output according to the MI version. Apart from mi0, new versions of
27413 @value{GDBN} will not support old versions of MI and it will be the
27414 responsibility of the front end to work with the new one.
27416 @c Starting with mi3, add a new command -mi-version that prints the MI
27419 The best way to avoid unexpected changes in MI that might break your front
27420 end is to make your project known to @value{GDBN} developers and
27421 follow development on @email{gdb@@sourceware.org} and
27422 @email{gdb-patches@@sourceware.org}.
27423 @cindex mailing lists
27425 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27426 @node GDB/MI Output Records
27427 @section @sc{gdb/mi} Output Records
27430 * GDB/MI Result Records::
27431 * GDB/MI Stream Records::
27432 * GDB/MI Async Records::
27433 * GDB/MI Frame Information::
27434 * GDB/MI Thread Information::
27435 * GDB/MI Ada Exception Information::
27438 @node GDB/MI Result Records
27439 @subsection @sc{gdb/mi} Result Records
27441 @cindex result records in @sc{gdb/mi}
27442 @cindex @sc{gdb/mi}, result records
27443 In addition to a number of out-of-band notifications, the response to a
27444 @sc{gdb/mi} command includes one of the following result indications:
27448 @item "^done" [ "," @var{results} ]
27449 The synchronous operation was successful, @code{@var{results}} are the return
27454 This result record is equivalent to @samp{^done}. Historically, it
27455 was output instead of @samp{^done} if the command has resumed the
27456 target. This behaviour is maintained for backward compatibility, but
27457 all frontends should treat @samp{^done} and @samp{^running}
27458 identically and rely on the @samp{*running} output record to determine
27459 which threads are resumed.
27463 @value{GDBN} has connected to a remote target.
27465 @item "^error" "," @var{c-string}
27467 The operation failed. The @code{@var{c-string}} contains the corresponding
27472 @value{GDBN} has terminated.
27476 @node GDB/MI Stream Records
27477 @subsection @sc{gdb/mi} Stream Records
27479 @cindex @sc{gdb/mi}, stream records
27480 @cindex stream records in @sc{gdb/mi}
27481 @value{GDBN} internally maintains a number of output streams: the console, the
27482 target, and the log. The output intended for each of these streams is
27483 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
27485 Each stream record begins with a unique @dfn{prefix character} which
27486 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
27487 Syntax}). In addition to the prefix, each stream record contains a
27488 @code{@var{string-output}}. This is either raw text (with an implicit new
27489 line) or a quoted C string (which does not contain an implicit newline).
27492 @item "~" @var{string-output}
27493 The console output stream contains text that should be displayed in the
27494 CLI console window. It contains the textual responses to CLI commands.
27496 @item "@@" @var{string-output}
27497 The target output stream contains any textual output from the running
27498 target. This is only present when GDB's event loop is truly
27499 asynchronous, which is currently only the case for remote targets.
27501 @item "&" @var{string-output}
27502 The log stream contains debugging messages being produced by @value{GDBN}'s
27506 @node GDB/MI Async Records
27507 @subsection @sc{gdb/mi} Async Records
27509 @cindex async records in @sc{gdb/mi}
27510 @cindex @sc{gdb/mi}, async records
27511 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
27512 additional changes that have occurred. Those changes can either be a
27513 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
27514 target activity (e.g., target stopped).
27516 The following is the list of possible async records:
27520 @item *running,thread-id="@var{thread}"
27521 The target is now running. The @var{thread} field tells which
27522 specific thread is now running, and can be @samp{all} if all threads
27523 are running. The frontend should assume that no interaction with a
27524 running thread is possible after this notification is produced.
27525 The frontend should not assume that this notification is output
27526 only once for any command. @value{GDBN} may emit this notification
27527 several times, either for different threads, because it cannot resume
27528 all threads together, or even for a single thread, if the thread must
27529 be stepped though some code before letting it run freely.
27531 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
27532 The target has stopped. The @var{reason} field can have one of the
27536 @item breakpoint-hit
27537 A breakpoint was reached.
27538 @item watchpoint-trigger
27539 A watchpoint was triggered.
27540 @item read-watchpoint-trigger
27541 A read watchpoint was triggered.
27542 @item access-watchpoint-trigger
27543 An access watchpoint was triggered.
27544 @item function-finished
27545 An -exec-finish or similar CLI command was accomplished.
27546 @item location-reached
27547 An -exec-until or similar CLI command was accomplished.
27548 @item watchpoint-scope
27549 A watchpoint has gone out of scope.
27550 @item end-stepping-range
27551 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
27552 similar CLI command was accomplished.
27553 @item exited-signalled
27554 The inferior exited because of a signal.
27556 The inferior exited.
27557 @item exited-normally
27558 The inferior exited normally.
27559 @item signal-received
27560 A signal was received by the inferior.
27562 The inferior has stopped due to a library being loaded or unloaded.
27563 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
27564 set or when a @code{catch load} or @code{catch unload} catchpoint is
27565 in use (@pxref{Set Catchpoints}).
27567 The inferior has forked. This is reported when @code{catch fork}
27568 (@pxref{Set Catchpoints}) has been used.
27570 The inferior has vforked. This is reported in when @code{catch vfork}
27571 (@pxref{Set Catchpoints}) has been used.
27572 @item syscall-entry
27573 The inferior entered a system call. This is reported when @code{catch
27574 syscall} (@pxref{Set Catchpoints}) has been used.
27575 @item syscall-entry
27576 The inferior returned from a system call. This is reported when
27577 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
27579 The inferior called @code{exec}. This is reported when @code{catch exec}
27580 (@pxref{Set Catchpoints}) has been used.
27583 The @var{id} field identifies the thread that directly caused the stop
27584 -- for example by hitting a breakpoint. Depending on whether all-stop
27585 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
27586 stop all threads, or only the thread that directly triggered the stop.
27587 If all threads are stopped, the @var{stopped} field will have the
27588 value of @code{"all"}. Otherwise, the value of the @var{stopped}
27589 field will be a list of thread identifiers. Presently, this list will
27590 always include a single thread, but frontend should be prepared to see
27591 several threads in the list. The @var{core} field reports the
27592 processor core on which the stop event has happened. This field may be absent
27593 if such information is not available.
27595 @item =thread-group-added,id="@var{id}"
27596 @itemx =thread-group-removed,id="@var{id}"
27597 A thread group was either added or removed. The @var{id} field
27598 contains the @value{GDBN} identifier of the thread group. When a thread
27599 group is added, it generally might not be associated with a running
27600 process. When a thread group is removed, its id becomes invalid and
27601 cannot be used in any way.
27603 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
27604 A thread group became associated with a running program,
27605 either because the program was just started or the thread group
27606 was attached to a program. The @var{id} field contains the
27607 @value{GDBN} identifier of the thread group. The @var{pid} field
27608 contains process identifier, specific to the operating system.
27610 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
27611 A thread group is no longer associated with a running program,
27612 either because the program has exited, or because it was detached
27613 from. The @var{id} field contains the @value{GDBN} identifier of the
27614 thread group. @var{code} is the exit code of the inferior; it exists
27615 only when the inferior exited with some code.
27617 @item =thread-created,id="@var{id}",group-id="@var{gid}"
27618 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
27619 A thread either was created, or has exited. The @var{id} field
27620 contains the @value{GDBN} identifier of the thread. The @var{gid}
27621 field identifies the thread group this thread belongs to.
27623 @item =thread-selected,id="@var{id}"
27624 Informs that the selected thread was changed as result of the last
27625 command. This notification is not emitted as result of @code{-thread-select}
27626 command but is emitted whenever an MI command that is not documented
27627 to change the selected thread actually changes it. In particular,
27628 invoking, directly or indirectly (via user-defined command), the CLI
27629 @code{thread} command, will generate this notification.
27631 We suggest that in response to this notification, front ends
27632 highlight the selected thread and cause subsequent commands to apply to
27635 @item =library-loaded,...
27636 Reports that a new library file was loaded by the program. This
27637 notification has 4 fields---@var{id}, @var{target-name},
27638 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
27639 opaque identifier of the library. For remote debugging case,
27640 @var{target-name} and @var{host-name} fields give the name of the
27641 library file on the target, and on the host respectively. For native
27642 debugging, both those fields have the same value. The
27643 @var{symbols-loaded} field is emitted only for backward compatibility
27644 and should not be relied on to convey any useful information. The
27645 @var{thread-group} field, if present, specifies the id of the thread
27646 group in whose context the library was loaded. If the field is
27647 absent, it means the library was loaded in the context of all present
27650 @item =library-unloaded,...
27651 Reports that a library was unloaded by the program. This notification
27652 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
27653 the same meaning as for the @code{=library-loaded} notification.
27654 The @var{thread-group} field, if present, specifies the id of the
27655 thread group in whose context the library was unloaded. If the field is
27656 absent, it means the library was unloaded in the context of all present
27659 @item =breakpoint-created,bkpt=@{...@}
27660 @itemx =breakpoint-modified,bkpt=@{...@}
27661 @itemx =breakpoint-deleted,id=@var{number}
27662 Reports that a breakpoint was created, modified, or deleted,
27663 respectively. Only user-visible breakpoints are reported to the MI
27666 The @var{bkpt} argument is of the same form as returned by the various
27667 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
27668 @var{number} is the ordinal number of the breakpoint.
27670 Note that if a breakpoint is emitted in the result record of a
27671 command, then it will not also be emitted in an async record.
27673 @item =cmd-param-changed,param=@var{param},value=@var{value}
27674 Reports that a parameter of the command @code{set @var{param}} is
27675 changed to @var{value}. In the multi-word @code{set} command,
27676 the @var{param} is the whole parameter list to @code{set} command.
27677 For example, In command @code{set check type on}, @var{param}
27678 is @code{check type} and @var{value} is @code{on}.
27681 @node GDB/MI Frame Information
27682 @subsection @sc{gdb/mi} Frame Information
27684 Response from many MI commands includes an information about stack
27685 frame. This information is a tuple that may have the following
27690 The level of the stack frame. The innermost frame has the level of
27691 zero. This field is always present.
27694 The name of the function corresponding to the frame. This field may
27695 be absent if @value{GDBN} is unable to determine the function name.
27698 The code address for the frame. This field is always present.
27701 The name of the source files that correspond to the frame's code
27702 address. This field may be absent.
27705 The source line corresponding to the frames' code address. This field
27709 The name of the binary file (either executable or shared library) the
27710 corresponds to the frame's code address. This field may be absent.
27714 @node GDB/MI Thread Information
27715 @subsection @sc{gdb/mi} Thread Information
27717 Whenever @value{GDBN} has to report an information about a thread, it
27718 uses a tuple with the following fields:
27722 The numeric id assigned to the thread by @value{GDBN}. This field is
27726 Target-specific string identifying the thread. This field is always present.
27729 Additional information about the thread provided by the target.
27730 It is supposed to be human-readable and not interpreted by the
27731 frontend. This field is optional.
27734 Either @samp{stopped} or @samp{running}, depending on whether the
27735 thread is presently running. This field is always present.
27738 The value of this field is an integer number of the processor core the
27739 thread was last seen on. This field is optional.
27742 @node GDB/MI Ada Exception Information
27743 @subsection @sc{gdb/mi} Ada Exception Information
27745 Whenever a @code{*stopped} record is emitted because the program
27746 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
27747 @value{GDBN} provides the name of the exception that was raised via
27748 the @code{exception-name} field.
27750 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27751 @node GDB/MI Simple Examples
27752 @section Simple Examples of @sc{gdb/mi} Interaction
27753 @cindex @sc{gdb/mi}, simple examples
27755 This subsection presents several simple examples of interaction using
27756 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
27757 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
27758 the output received from @sc{gdb/mi}.
27760 Note the line breaks shown in the examples are here only for
27761 readability, they don't appear in the real output.
27763 @subheading Setting a Breakpoint
27765 Setting a breakpoint generates synchronous output which contains detailed
27766 information of the breakpoint.
27769 -> -break-insert main
27770 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27771 enabled="y",addr="0x08048564",func="main",file="myprog.c",
27772 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
27776 @subheading Program Execution
27778 Program execution generates asynchronous records and MI gives the
27779 reason that execution stopped.
27785 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
27786 frame=@{addr="0x08048564",func="main",
27787 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
27788 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
27793 <- *stopped,reason="exited-normally"
27797 @subheading Quitting @value{GDBN}
27799 Quitting @value{GDBN} just prints the result class @samp{^exit}.
27807 Please note that @samp{^exit} is printed immediately, but it might
27808 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
27809 performs necessary cleanups, including killing programs being debugged
27810 or disconnecting from debug hardware, so the frontend should wait till
27811 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
27812 fails to exit in reasonable time.
27814 @subheading A Bad Command
27816 Here's what happens if you pass a non-existent command:
27820 <- ^error,msg="Undefined MI command: rubbish"
27825 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27826 @node GDB/MI Command Description Format
27827 @section @sc{gdb/mi} Command Description Format
27829 The remaining sections describe blocks of commands. Each block of
27830 commands is laid out in a fashion similar to this section.
27832 @subheading Motivation
27834 The motivation for this collection of commands.
27836 @subheading Introduction
27838 A brief introduction to this collection of commands as a whole.
27840 @subheading Commands
27842 For each command in the block, the following is described:
27844 @subsubheading Synopsis
27847 -command @var{args}@dots{}
27850 @subsubheading Result
27852 @subsubheading @value{GDBN} Command
27854 The corresponding @value{GDBN} CLI command(s), if any.
27856 @subsubheading Example
27858 Example(s) formatted for readability. Some of the described commands have
27859 not been implemented yet and these are labeled N.A.@: (not available).
27862 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27863 @node GDB/MI Breakpoint Commands
27864 @section @sc{gdb/mi} Breakpoint Commands
27866 @cindex breakpoint commands for @sc{gdb/mi}
27867 @cindex @sc{gdb/mi}, breakpoint commands
27868 This section documents @sc{gdb/mi} commands for manipulating
27871 @subheading The @code{-break-after} Command
27872 @findex -break-after
27874 @subsubheading Synopsis
27877 -break-after @var{number} @var{count}
27880 The breakpoint number @var{number} is not in effect until it has been
27881 hit @var{count} times. To see how this is reflected in the output of
27882 the @samp{-break-list} command, see the description of the
27883 @samp{-break-list} command below.
27885 @subsubheading @value{GDBN} Command
27887 The corresponding @value{GDBN} command is @samp{ignore}.
27889 @subsubheading Example
27894 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27895 enabled="y",addr="0x000100d0",func="main",file="hello.c",
27896 fullname="/home/foo/hello.c",line="5",times="0"@}
27903 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27904 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27905 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27906 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27907 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27908 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27909 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27910 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27911 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27912 line="5",times="0",ignore="3"@}]@}
27917 @subheading The @code{-break-catch} Command
27918 @findex -break-catch
27921 @subheading The @code{-break-commands} Command
27922 @findex -break-commands
27924 @subsubheading Synopsis
27927 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
27930 Specifies the CLI commands that should be executed when breakpoint
27931 @var{number} is hit. The parameters @var{command1} to @var{commandN}
27932 are the commands. If no command is specified, any previously-set
27933 commands are cleared. @xref{Break Commands}. Typical use of this
27934 functionality is tracing a program, that is, printing of values of
27935 some variables whenever breakpoint is hit and then continuing.
27937 @subsubheading @value{GDBN} Command
27939 The corresponding @value{GDBN} command is @samp{commands}.
27941 @subsubheading Example
27946 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27947 enabled="y",addr="0x000100d0",func="main",file="hello.c",
27948 fullname="/home/foo/hello.c",line="5",times="0"@}
27950 -break-commands 1 "print v" "continue"
27955 @subheading The @code{-break-condition} Command
27956 @findex -break-condition
27958 @subsubheading Synopsis
27961 -break-condition @var{number} @var{expr}
27964 Breakpoint @var{number} will stop the program only if the condition in
27965 @var{expr} is true. The condition becomes part of the
27966 @samp{-break-list} output (see the description of the @samp{-break-list}
27969 @subsubheading @value{GDBN} Command
27971 The corresponding @value{GDBN} command is @samp{condition}.
27973 @subsubheading Example
27977 -break-condition 1 1
27981 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27982 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27983 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27984 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27985 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27986 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27987 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27988 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27989 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27990 line="5",cond="1",times="0",ignore="3"@}]@}
27994 @subheading The @code{-break-delete} Command
27995 @findex -break-delete
27997 @subsubheading Synopsis
28000 -break-delete ( @var{breakpoint} )+
28003 Delete the breakpoint(s) whose number(s) are specified in the argument
28004 list. This is obviously reflected in the breakpoint list.
28006 @subsubheading @value{GDBN} Command
28008 The corresponding @value{GDBN} command is @samp{delete}.
28010 @subsubheading Example
28018 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
28019 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28020 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28021 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28022 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28023 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28024 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28029 @subheading The @code{-break-disable} Command
28030 @findex -break-disable
28032 @subsubheading Synopsis
28035 -break-disable ( @var{breakpoint} )+
28038 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
28039 break list is now set to @samp{n} for the named @var{breakpoint}(s).
28041 @subsubheading @value{GDBN} Command
28043 The corresponding @value{GDBN} command is @samp{disable}.
28045 @subsubheading Example
28053 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28054 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28055 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28056 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28057 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28058 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28059 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28060 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
28061 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28062 line="5",times="0"@}]@}
28066 @subheading The @code{-break-enable} Command
28067 @findex -break-enable
28069 @subsubheading Synopsis
28072 -break-enable ( @var{breakpoint} )+
28075 Enable (previously disabled) @var{breakpoint}(s).
28077 @subsubheading @value{GDBN} Command
28079 The corresponding @value{GDBN} command is @samp{enable}.
28081 @subsubheading Example
28089 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28090 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28091 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28092 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28093 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28094 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28095 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28096 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28097 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28098 line="5",times="0"@}]@}
28102 @subheading The @code{-break-info} Command
28103 @findex -break-info
28105 @subsubheading Synopsis
28108 -break-info @var{breakpoint}
28112 Get information about a single breakpoint.
28114 @subsubheading @value{GDBN} Command
28116 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
28118 @subsubheading Example
28121 @subheading The @code{-break-insert} Command
28122 @findex -break-insert
28124 @subsubheading Synopsis
28127 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
28128 [ -c @var{condition} ] [ -i @var{ignore-count} ]
28129 [ -p @var{thread-id} ] [ @var{location} ]
28133 If specified, @var{location}, can be one of:
28140 @item filename:linenum
28141 @item filename:function
28145 The possible optional parameters of this command are:
28149 Insert a temporary breakpoint.
28151 Insert a hardware breakpoint.
28153 If @var{location} cannot be parsed (for example if it
28154 refers to unknown files or functions), create a pending
28155 breakpoint. Without this flag, @value{GDBN} will report
28156 an error, and won't create a breakpoint, if @var{location}
28159 Create a disabled breakpoint.
28161 Create a tracepoint. @xref{Tracepoints}. When this parameter
28162 is used together with @samp{-h}, a fast tracepoint is created.
28163 @item -c @var{condition}
28164 Make the breakpoint conditional on @var{condition}.
28165 @item -i @var{ignore-count}
28166 Initialize the @var{ignore-count}.
28167 @item -p @var{thread-id}
28168 Restrict the breakpoint to the specified @var{thread-id}.
28171 @subsubheading Result
28173 The result is in the form:
28176 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
28177 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
28178 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
28179 times="@var{times}"@}
28183 where @var{number} is the @value{GDBN} number for this breakpoint,
28184 @var{funcname} is the name of the function where the breakpoint was
28185 inserted, @var{filename} is the name of the source file which contains
28186 this function, @var{lineno} is the source line number within that file
28187 and @var{times} the number of times that the breakpoint has been hit
28188 (always 0 for -break-insert but may be greater for -break-info or -break-list
28189 which use the same output).
28191 Note: this format is open to change.
28192 @c An out-of-band breakpoint instead of part of the result?
28194 @subsubheading @value{GDBN} Command
28196 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
28197 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
28199 @subsubheading Example
28204 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
28205 fullname="/home/foo/recursive2.c,line="4",times="0"@}
28207 -break-insert -t foo
28208 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
28209 fullname="/home/foo/recursive2.c,line="11",times="0"@}
28212 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28213 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28214 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28215 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28216 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28217 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28218 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28219 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28220 addr="0x0001072c", func="main",file="recursive2.c",
28221 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
28222 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
28223 addr="0x00010774",func="foo",file="recursive2.c",
28224 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
28226 @c -break-insert -r foo.*
28227 @c ~int foo(int, int);
28228 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
28229 @c "fullname="/home/foo/recursive2.c",line="11",times="0"@}
28233 @subheading The @code{-break-list} Command
28234 @findex -break-list
28236 @subsubheading Synopsis
28242 Displays the list of inserted breakpoints, showing the following fields:
28246 number of the breakpoint
28248 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
28250 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
28253 is the breakpoint enabled or no: @samp{y} or @samp{n}
28255 memory location at which the breakpoint is set
28257 logical location of the breakpoint, expressed by function name, file
28260 number of times the breakpoint has been hit
28263 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
28264 @code{body} field is an empty list.
28266 @subsubheading @value{GDBN} Command
28268 The corresponding @value{GDBN} command is @samp{info break}.
28270 @subsubheading Example
28275 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28276 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28277 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28278 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28279 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28280 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28281 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28282 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28283 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
28284 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28285 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
28286 line="13",times="0"@}]@}
28290 Here's an example of the result when there are no breakpoints:
28295 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
28296 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28297 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28298 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28299 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28300 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28301 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28306 @subheading The @code{-break-passcount} Command
28307 @findex -break-passcount
28309 @subsubheading Synopsis
28312 -break-passcount @var{tracepoint-number} @var{passcount}
28315 Set the passcount for tracepoint @var{tracepoint-number} to
28316 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
28317 is not a tracepoint, error is emitted. This corresponds to CLI
28318 command @samp{passcount}.
28320 @subheading The @code{-break-watch} Command
28321 @findex -break-watch
28323 @subsubheading Synopsis
28326 -break-watch [ -a | -r ]
28329 Create a watchpoint. With the @samp{-a} option it will create an
28330 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
28331 read from or on a write to the memory location. With the @samp{-r}
28332 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
28333 trigger only when the memory location is accessed for reading. Without
28334 either of the options, the watchpoint created is a regular watchpoint,
28335 i.e., it will trigger when the memory location is accessed for writing.
28336 @xref{Set Watchpoints, , Setting Watchpoints}.
28338 Note that @samp{-break-list} will report a single list of watchpoints and
28339 breakpoints inserted.
28341 @subsubheading @value{GDBN} Command
28343 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
28346 @subsubheading Example
28348 Setting a watchpoint on a variable in the @code{main} function:
28353 ^done,wpt=@{number="2",exp="x"@}
28358 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
28359 value=@{old="-268439212",new="55"@},
28360 frame=@{func="main",args=[],file="recursive2.c",
28361 fullname="/home/foo/bar/recursive2.c",line="5"@}
28365 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
28366 the program execution twice: first for the variable changing value, then
28367 for the watchpoint going out of scope.
28372 ^done,wpt=@{number="5",exp="C"@}
28377 *stopped,reason="watchpoint-trigger",
28378 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
28379 frame=@{func="callee4",args=[],
28380 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28381 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
28386 *stopped,reason="watchpoint-scope",wpnum="5",
28387 frame=@{func="callee3",args=[@{name="strarg",
28388 value="0x11940 \"A string argument.\""@}],
28389 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28390 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28394 Listing breakpoints and watchpoints, at different points in the program
28395 execution. Note that once the watchpoint goes out of scope, it is
28401 ^done,wpt=@{number="2",exp="C"@}
28404 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28405 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28406 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28407 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28408 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28409 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28410 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28411 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28412 addr="0x00010734",func="callee4",
28413 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28414 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
28415 bkpt=@{number="2",type="watchpoint",disp="keep",
28416 enabled="y",addr="",what="C",times="0"@}]@}
28421 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
28422 value=@{old="-276895068",new="3"@},
28423 frame=@{func="callee4",args=[],
28424 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28425 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
28428 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28429 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28430 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28431 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28432 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28433 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28434 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28435 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28436 addr="0x00010734",func="callee4",
28437 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28438 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
28439 bkpt=@{number="2",type="watchpoint",disp="keep",
28440 enabled="y",addr="",what="C",times="-5"@}]@}
28444 ^done,reason="watchpoint-scope",wpnum="2",
28445 frame=@{func="callee3",args=[@{name="strarg",
28446 value="0x11940 \"A string argument.\""@}],
28447 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28448 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28451 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28452 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28453 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28454 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28455 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28456 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28457 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28458 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28459 addr="0x00010734",func="callee4",
28460 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28461 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
28466 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28467 @node GDB/MI Program Context
28468 @section @sc{gdb/mi} Program Context
28470 @subheading The @code{-exec-arguments} Command
28471 @findex -exec-arguments
28474 @subsubheading Synopsis
28477 -exec-arguments @var{args}
28480 Set the inferior program arguments, to be used in the next
28483 @subsubheading @value{GDBN} Command
28485 The corresponding @value{GDBN} command is @samp{set args}.
28487 @subsubheading Example
28491 -exec-arguments -v word
28498 @subheading The @code{-exec-show-arguments} Command
28499 @findex -exec-show-arguments
28501 @subsubheading Synopsis
28504 -exec-show-arguments
28507 Print the arguments of the program.
28509 @subsubheading @value{GDBN} Command
28511 The corresponding @value{GDBN} command is @samp{show args}.
28513 @subsubheading Example
28518 @subheading The @code{-environment-cd} Command
28519 @findex -environment-cd
28521 @subsubheading Synopsis
28524 -environment-cd @var{pathdir}
28527 Set @value{GDBN}'s working directory.
28529 @subsubheading @value{GDBN} Command
28531 The corresponding @value{GDBN} command is @samp{cd}.
28533 @subsubheading Example
28537 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
28543 @subheading The @code{-environment-directory} Command
28544 @findex -environment-directory
28546 @subsubheading Synopsis
28549 -environment-directory [ -r ] [ @var{pathdir} ]+
28552 Add directories @var{pathdir} to beginning of search path for source files.
28553 If the @samp{-r} option is used, the search path is reset to the default
28554 search path. If directories @var{pathdir} are supplied in addition to the
28555 @samp{-r} option, the search path is first reset and then addition
28557 Multiple directories may be specified, separated by blanks. Specifying
28558 multiple directories in a single command
28559 results in the directories added to the beginning of the
28560 search path in the same order they were presented in the command.
28561 If blanks are needed as
28562 part of a directory name, double-quotes should be used around
28563 the name. In the command output, the path will show up separated
28564 by the system directory-separator character. The directory-separator
28565 character must not be used
28566 in any directory name.
28567 If no directories are specified, the current search path is displayed.
28569 @subsubheading @value{GDBN} Command
28571 The corresponding @value{GDBN} command is @samp{dir}.
28573 @subsubheading Example
28577 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
28578 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
28580 -environment-directory ""
28581 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
28583 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
28584 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
28586 -environment-directory -r
28587 ^done,source-path="$cdir:$cwd"
28592 @subheading The @code{-environment-path} Command
28593 @findex -environment-path
28595 @subsubheading Synopsis
28598 -environment-path [ -r ] [ @var{pathdir} ]+
28601 Add directories @var{pathdir} to beginning of search path for object files.
28602 If the @samp{-r} option is used, the search path is reset to the original
28603 search path that existed at gdb start-up. If directories @var{pathdir} are
28604 supplied in addition to the
28605 @samp{-r} option, the search path is first reset and then addition
28607 Multiple directories may be specified, separated by blanks. Specifying
28608 multiple directories in a single command
28609 results in the directories added to the beginning of the
28610 search path in the same order they were presented in the command.
28611 If blanks are needed as
28612 part of a directory name, double-quotes should be used around
28613 the name. In the command output, the path will show up separated
28614 by the system directory-separator character. The directory-separator
28615 character must not be used
28616 in any directory name.
28617 If no directories are specified, the current path is displayed.
28620 @subsubheading @value{GDBN} Command
28622 The corresponding @value{GDBN} command is @samp{path}.
28624 @subsubheading Example
28629 ^done,path="/usr/bin"
28631 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
28632 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
28634 -environment-path -r /usr/local/bin
28635 ^done,path="/usr/local/bin:/usr/bin"
28640 @subheading The @code{-environment-pwd} Command
28641 @findex -environment-pwd
28643 @subsubheading Synopsis
28649 Show the current working directory.
28651 @subsubheading @value{GDBN} Command
28653 The corresponding @value{GDBN} command is @samp{pwd}.
28655 @subsubheading Example
28660 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
28664 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28665 @node GDB/MI Thread Commands
28666 @section @sc{gdb/mi} Thread Commands
28669 @subheading The @code{-thread-info} Command
28670 @findex -thread-info
28672 @subsubheading Synopsis
28675 -thread-info [ @var{thread-id} ]
28678 Reports information about either a specific thread, if
28679 the @var{thread-id} parameter is present, or about all
28680 threads. When printing information about all threads,
28681 also reports the current thread.
28683 @subsubheading @value{GDBN} Command
28685 The @samp{info thread} command prints the same information
28688 @subsubheading Result
28690 The result is a list of threads. The following attributes are
28691 defined for a given thread:
28695 This field exists only for the current thread. It has the value @samp{*}.
28698 The identifier that @value{GDBN} uses to refer to the thread.
28701 The identifier that the target uses to refer to the thread.
28704 Extra information about the thread, in a target-specific format. This
28708 The name of the thread. If the user specified a name using the
28709 @code{thread name} command, then this name is given. Otherwise, if
28710 @value{GDBN} can extract the thread name from the target, then that
28711 name is given. If @value{GDBN} cannot find the thread name, then this
28715 The stack frame currently executing in the thread.
28718 The thread's state. The @samp{state} field may have the following
28723 The thread is stopped. Frame information is available for stopped
28727 The thread is running. There's no frame information for running
28733 If @value{GDBN} can find the CPU core on which this thread is running,
28734 then this field is the core identifier. This field is optional.
28738 @subsubheading Example
28743 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
28744 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
28745 args=[]@},state="running"@},
28746 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
28747 frame=@{level="0",addr="0x0804891f",func="foo",
28748 args=[@{name="i",value="10"@}],
28749 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
28750 state="running"@}],
28751 current-thread-id="1"
28755 @subheading The @code{-thread-list-ids} Command
28756 @findex -thread-list-ids
28758 @subsubheading Synopsis
28764 Produces a list of the currently known @value{GDBN} thread ids. At the
28765 end of the list it also prints the total number of such threads.
28767 This command is retained for historical reasons, the
28768 @code{-thread-info} command should be used instead.
28770 @subsubheading @value{GDBN} Command
28772 Part of @samp{info threads} supplies the same information.
28774 @subsubheading Example
28779 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
28780 current-thread-id="1",number-of-threads="3"
28785 @subheading The @code{-thread-select} Command
28786 @findex -thread-select
28788 @subsubheading Synopsis
28791 -thread-select @var{threadnum}
28794 Make @var{threadnum} the current thread. It prints the number of the new
28795 current thread, and the topmost frame for that thread.
28797 This command is deprecated in favor of explicitly using the
28798 @samp{--thread} option to each command.
28800 @subsubheading @value{GDBN} Command
28802 The corresponding @value{GDBN} command is @samp{thread}.
28804 @subsubheading Example
28811 *stopped,reason="end-stepping-range",thread-id="2",line="187",
28812 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
28816 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
28817 number-of-threads="3"
28820 ^done,new-thread-id="3",
28821 frame=@{level="0",func="vprintf",
28822 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
28823 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
28827 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28828 @node GDB/MI Ada Tasking Commands
28829 @section @sc{gdb/mi} Ada Tasking Commands
28831 @subheading The @code{-ada-task-info} Command
28832 @findex -ada-task-info
28834 @subsubheading Synopsis
28837 -ada-task-info [ @var{task-id} ]
28840 Reports information about either a specific Ada task, if the
28841 @var{task-id} parameter is present, or about all Ada tasks.
28843 @subsubheading @value{GDBN} Command
28845 The @samp{info tasks} command prints the same information
28846 about all Ada tasks (@pxref{Ada Tasks}).
28848 @subsubheading Result
28850 The result is a table of Ada tasks. The following columns are
28851 defined for each Ada task:
28855 This field exists only for the current thread. It has the value @samp{*}.
28858 The identifier that @value{GDBN} uses to refer to the Ada task.
28861 The identifier that the target uses to refer to the Ada task.
28864 The identifier of the thread corresponding to the Ada task.
28866 This field should always exist, as Ada tasks are always implemented
28867 on top of a thread. But if @value{GDBN} cannot find this corresponding
28868 thread for any reason, the field is omitted.
28871 This field exists only when the task was created by another task.
28872 In this case, it provides the ID of the parent task.
28875 The base priority of the task.
28878 The current state of the task. For a detailed description of the
28879 possible states, see @ref{Ada Tasks}.
28882 The name of the task.
28886 @subsubheading Example
28890 ^done,tasks=@{nr_rows="3",nr_cols="8",
28891 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
28892 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
28893 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
28894 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
28895 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
28896 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
28897 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
28898 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
28899 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
28900 state="Child Termination Wait",name="main_task"@}]@}
28904 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28905 @node GDB/MI Program Execution
28906 @section @sc{gdb/mi} Program Execution
28908 These are the asynchronous commands which generate the out-of-band
28909 record @samp{*stopped}. Currently @value{GDBN} only really executes
28910 asynchronously with remote targets and this interaction is mimicked in
28913 @subheading The @code{-exec-continue} Command
28914 @findex -exec-continue
28916 @subsubheading Synopsis
28919 -exec-continue [--reverse] [--all|--thread-group N]
28922 Resumes the execution of the inferior program, which will continue
28923 to execute until it reaches a debugger stop event. If the
28924 @samp{--reverse} option is specified, execution resumes in reverse until
28925 it reaches a stop event. Stop events may include
28928 breakpoints or watchpoints
28930 signals or exceptions
28932 the end of the process (or its beginning under @samp{--reverse})
28934 the end or beginning of a replay log if one is being used.
28936 In all-stop mode (@pxref{All-Stop
28937 Mode}), may resume only one thread, or all threads, depending on the
28938 value of the @samp{scheduler-locking} variable. If @samp{--all} is
28939 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
28940 ignored in all-stop mode. If the @samp{--thread-group} options is
28941 specified, then all threads in that thread group are resumed.
28943 @subsubheading @value{GDBN} Command
28945 The corresponding @value{GDBN} corresponding is @samp{continue}.
28947 @subsubheading Example
28954 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
28955 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
28961 @subheading The @code{-exec-finish} Command
28962 @findex -exec-finish
28964 @subsubheading Synopsis
28967 -exec-finish [--reverse]
28970 Resumes the execution of the inferior program until the current
28971 function is exited. Displays the results returned by the function.
28972 If the @samp{--reverse} option is specified, resumes the reverse
28973 execution of the inferior program until the point where current
28974 function was called.
28976 @subsubheading @value{GDBN} Command
28978 The corresponding @value{GDBN} command is @samp{finish}.
28980 @subsubheading Example
28982 Function returning @code{void}.
28989 *stopped,reason="function-finished",frame=@{func="main",args=[],
28990 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
28994 Function returning other than @code{void}. The name of the internal
28995 @value{GDBN} variable storing the result is printed, together with the
29002 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
29003 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
29004 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29005 gdb-result-var="$1",return-value="0"
29010 @subheading The @code{-exec-interrupt} Command
29011 @findex -exec-interrupt
29013 @subsubheading Synopsis
29016 -exec-interrupt [--all|--thread-group N]
29019 Interrupts the background execution of the target. Note how the token
29020 associated with the stop message is the one for the execution command
29021 that has been interrupted. The token for the interrupt itself only
29022 appears in the @samp{^done} output. If the user is trying to
29023 interrupt a non-running program, an error message will be printed.
29025 Note that when asynchronous execution is enabled, this command is
29026 asynchronous just like other execution commands. That is, first the
29027 @samp{^done} response will be printed, and the target stop will be
29028 reported after that using the @samp{*stopped} notification.
29030 In non-stop mode, only the context thread is interrupted by default.
29031 All threads (in all inferiors) will be interrupted if the
29032 @samp{--all} option is specified. If the @samp{--thread-group}
29033 option is specified, all threads in that group will be interrupted.
29035 @subsubheading @value{GDBN} Command
29037 The corresponding @value{GDBN} command is @samp{interrupt}.
29039 @subsubheading Example
29050 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
29051 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
29052 fullname="/home/foo/bar/try.c",line="13"@}
29057 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
29061 @subheading The @code{-exec-jump} Command
29064 @subsubheading Synopsis
29067 -exec-jump @var{location}
29070 Resumes execution of the inferior program at the location specified by
29071 parameter. @xref{Specify Location}, for a description of the
29072 different forms of @var{location}.
29074 @subsubheading @value{GDBN} Command
29076 The corresponding @value{GDBN} command is @samp{jump}.
29078 @subsubheading Example
29081 -exec-jump foo.c:10
29082 *running,thread-id="all"
29087 @subheading The @code{-exec-next} Command
29090 @subsubheading Synopsis
29093 -exec-next [--reverse]
29096 Resumes execution of the inferior program, stopping when the beginning
29097 of the next source line is reached.
29099 If the @samp{--reverse} option is specified, resumes reverse execution
29100 of the inferior program, stopping at the beginning of the previous
29101 source line. If you issue this command on the first line of a
29102 function, it will take you back to the caller of that function, to the
29103 source line where the function was called.
29106 @subsubheading @value{GDBN} Command
29108 The corresponding @value{GDBN} command is @samp{next}.
29110 @subsubheading Example
29116 *stopped,reason="end-stepping-range",line="8",file="hello.c"
29121 @subheading The @code{-exec-next-instruction} Command
29122 @findex -exec-next-instruction
29124 @subsubheading Synopsis
29127 -exec-next-instruction [--reverse]
29130 Executes one machine instruction. If the instruction is a function
29131 call, continues until the function returns. If the program stops at an
29132 instruction in the middle of a source line, the address will be
29135 If the @samp{--reverse} option is specified, resumes reverse execution
29136 of the inferior program, stopping at the previous instruction. If the
29137 previously executed instruction was a return from another function,
29138 it will continue to execute in reverse until the call to that function
29139 (from the current stack frame) is reached.
29141 @subsubheading @value{GDBN} Command
29143 The corresponding @value{GDBN} command is @samp{nexti}.
29145 @subsubheading Example
29149 -exec-next-instruction
29153 *stopped,reason="end-stepping-range",
29154 addr="0x000100d4",line="5",file="hello.c"
29159 @subheading The @code{-exec-return} Command
29160 @findex -exec-return
29162 @subsubheading Synopsis
29168 Makes current function return immediately. Doesn't execute the inferior.
29169 Displays the new current frame.
29171 @subsubheading @value{GDBN} Command
29173 The corresponding @value{GDBN} command is @samp{return}.
29175 @subsubheading Example
29179 200-break-insert callee4
29180 200^done,bkpt=@{number="1",addr="0x00010734",
29181 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
29186 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29187 frame=@{func="callee4",args=[],
29188 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29189 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
29195 111^done,frame=@{level="0",func="callee3",
29196 args=[@{name="strarg",
29197 value="0x11940 \"A string argument.\""@}],
29198 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29199 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
29204 @subheading The @code{-exec-run} Command
29207 @subsubheading Synopsis
29210 -exec-run [--all | --thread-group N]
29213 Starts execution of the inferior from the beginning. The inferior
29214 executes until either a breakpoint is encountered or the program
29215 exits. In the latter case the output will include an exit code, if
29216 the program has exited exceptionally.
29218 When no option is specified, the current inferior is started. If the
29219 @samp{--thread-group} option is specified, it should refer to a thread
29220 group of type @samp{process}, and that thread group will be started.
29221 If the @samp{--all} option is specified, then all inferiors will be started.
29223 @subsubheading @value{GDBN} Command
29225 The corresponding @value{GDBN} command is @samp{run}.
29227 @subsubheading Examples
29232 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
29237 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29238 frame=@{func="main",args=[],file="recursive2.c",
29239 fullname="/home/foo/bar/recursive2.c",line="4"@}
29244 Program exited normally:
29252 *stopped,reason="exited-normally"
29257 Program exited exceptionally:
29265 *stopped,reason="exited",exit-code="01"
29269 Another way the program can terminate is if it receives a signal such as
29270 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
29274 *stopped,reason="exited-signalled",signal-name="SIGINT",
29275 signal-meaning="Interrupt"
29279 @c @subheading -exec-signal
29282 @subheading The @code{-exec-step} Command
29285 @subsubheading Synopsis
29288 -exec-step [--reverse]
29291 Resumes execution of the inferior program, stopping when the beginning
29292 of the next source line is reached, if the next source line is not a
29293 function call. If it is, stop at the first instruction of the called
29294 function. If the @samp{--reverse} option is specified, resumes reverse
29295 execution of the inferior program, stopping at the beginning of the
29296 previously executed source line.
29298 @subsubheading @value{GDBN} Command
29300 The corresponding @value{GDBN} command is @samp{step}.
29302 @subsubheading Example
29304 Stepping into a function:
29310 *stopped,reason="end-stepping-range",
29311 frame=@{func="foo",args=[@{name="a",value="10"@},
29312 @{name="b",value="0"@}],file="recursive2.c",
29313 fullname="/home/foo/bar/recursive2.c",line="11"@}
29323 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
29328 @subheading The @code{-exec-step-instruction} Command
29329 @findex -exec-step-instruction
29331 @subsubheading Synopsis
29334 -exec-step-instruction [--reverse]
29337 Resumes the inferior which executes one machine instruction. If the
29338 @samp{--reverse} option is specified, resumes reverse execution of the
29339 inferior program, stopping at the previously executed instruction.
29340 The output, once @value{GDBN} has stopped, will vary depending on
29341 whether we have stopped in the middle of a source line or not. In the
29342 former case, the address at which the program stopped will be printed
29345 @subsubheading @value{GDBN} Command
29347 The corresponding @value{GDBN} command is @samp{stepi}.
29349 @subsubheading Example
29353 -exec-step-instruction
29357 *stopped,reason="end-stepping-range",
29358 frame=@{func="foo",args=[],file="try.c",
29359 fullname="/home/foo/bar/try.c",line="10"@}
29361 -exec-step-instruction
29365 *stopped,reason="end-stepping-range",
29366 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
29367 fullname="/home/foo/bar/try.c",line="10"@}
29372 @subheading The @code{-exec-until} Command
29373 @findex -exec-until
29375 @subsubheading Synopsis
29378 -exec-until [ @var{location} ]
29381 Executes the inferior until the @var{location} specified in the
29382 argument is reached. If there is no argument, the inferior executes
29383 until a source line greater than the current one is reached. The
29384 reason for stopping in this case will be @samp{location-reached}.
29386 @subsubheading @value{GDBN} Command
29388 The corresponding @value{GDBN} command is @samp{until}.
29390 @subsubheading Example
29394 -exec-until recursive2.c:6
29398 *stopped,reason="location-reached",frame=@{func="main",args=[],
29399 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
29404 @subheading -file-clear
29405 Is this going away????
29408 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29409 @node GDB/MI Stack Manipulation
29410 @section @sc{gdb/mi} Stack Manipulation Commands
29413 @subheading The @code{-stack-info-frame} Command
29414 @findex -stack-info-frame
29416 @subsubheading Synopsis
29422 Get info on the selected frame.
29424 @subsubheading @value{GDBN} Command
29426 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
29427 (without arguments).
29429 @subsubheading Example
29434 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
29435 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29436 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
29440 @subheading The @code{-stack-info-depth} Command
29441 @findex -stack-info-depth
29443 @subsubheading Synopsis
29446 -stack-info-depth [ @var{max-depth} ]
29449 Return the depth of the stack. If the integer argument @var{max-depth}
29450 is specified, do not count beyond @var{max-depth} frames.
29452 @subsubheading @value{GDBN} Command
29454 There's no equivalent @value{GDBN} command.
29456 @subsubheading Example
29458 For a stack with frame levels 0 through 11:
29465 -stack-info-depth 4
29468 -stack-info-depth 12
29471 -stack-info-depth 11
29474 -stack-info-depth 13
29479 @subheading The @code{-stack-list-arguments} Command
29480 @findex -stack-list-arguments
29482 @subsubheading Synopsis
29485 -stack-list-arguments @var{print-values}
29486 [ @var{low-frame} @var{high-frame} ]
29489 Display a list of the arguments for the frames between @var{low-frame}
29490 and @var{high-frame} (inclusive). If @var{low-frame} and
29491 @var{high-frame} are not provided, list the arguments for the whole
29492 call stack. If the two arguments are equal, show the single frame
29493 at the corresponding level. It is an error if @var{low-frame} is
29494 larger than the actual number of frames. On the other hand,
29495 @var{high-frame} may be larger than the actual number of frames, in
29496 which case only existing frames will be returned.
29498 If @var{print-values} is 0 or @code{--no-values}, print only the names of
29499 the variables; if it is 1 or @code{--all-values}, print also their
29500 values; and if it is 2 or @code{--simple-values}, print the name,
29501 type and value for simple data types, and the name and type for arrays,
29502 structures and unions.
29504 Use of this command to obtain arguments in a single frame is
29505 deprecated in favor of the @samp{-stack-list-variables} command.
29507 @subsubheading @value{GDBN} Command
29509 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
29510 @samp{gdb_get_args} command which partially overlaps with the
29511 functionality of @samp{-stack-list-arguments}.
29513 @subsubheading Example
29520 frame=@{level="0",addr="0x00010734",func="callee4",
29521 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29522 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
29523 frame=@{level="1",addr="0x0001076c",func="callee3",
29524 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29525 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
29526 frame=@{level="2",addr="0x0001078c",func="callee2",
29527 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29528 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
29529 frame=@{level="3",addr="0x000107b4",func="callee1",
29530 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29531 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
29532 frame=@{level="4",addr="0x000107e0",func="main",
29533 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29534 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
29536 -stack-list-arguments 0
29539 frame=@{level="0",args=[]@},
29540 frame=@{level="1",args=[name="strarg"]@},
29541 frame=@{level="2",args=[name="intarg",name="strarg"]@},
29542 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
29543 frame=@{level="4",args=[]@}]
29545 -stack-list-arguments 1
29548 frame=@{level="0",args=[]@},
29550 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
29551 frame=@{level="2",args=[
29552 @{name="intarg",value="2"@},
29553 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
29554 @{frame=@{level="3",args=[
29555 @{name="intarg",value="2"@},
29556 @{name="strarg",value="0x11940 \"A string argument.\""@},
29557 @{name="fltarg",value="3.5"@}]@},
29558 frame=@{level="4",args=[]@}]
29560 -stack-list-arguments 0 2 2
29561 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
29563 -stack-list-arguments 1 2 2
29564 ^done,stack-args=[frame=@{level="2",
29565 args=[@{name="intarg",value="2"@},
29566 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
29570 @c @subheading -stack-list-exception-handlers
29573 @subheading The @code{-stack-list-frames} Command
29574 @findex -stack-list-frames
29576 @subsubheading Synopsis
29579 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
29582 List the frames currently on the stack. For each frame it displays the
29587 The frame number, 0 being the topmost frame, i.e., the innermost function.
29589 The @code{$pc} value for that frame.
29593 File name of the source file where the function lives.
29594 @item @var{fullname}
29595 The full file name of the source file where the function lives.
29597 Line number corresponding to the @code{$pc}.
29599 The shared library where this function is defined. This is only given
29600 if the frame's function is not known.
29603 If invoked without arguments, this command prints a backtrace for the
29604 whole stack. If given two integer arguments, it shows the frames whose
29605 levels are between the two arguments (inclusive). If the two arguments
29606 are equal, it shows the single frame at the corresponding level. It is
29607 an error if @var{low-frame} is larger than the actual number of
29608 frames. On the other hand, @var{high-frame} may be larger than the
29609 actual number of frames, in which case only existing frames will be returned.
29611 @subsubheading @value{GDBN} Command
29613 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
29615 @subsubheading Example
29617 Full stack backtrace:
29623 [frame=@{level="0",addr="0x0001076c",func="foo",
29624 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
29625 frame=@{level="1",addr="0x000107a4",func="foo",
29626 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29627 frame=@{level="2",addr="0x000107a4",func="foo",
29628 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29629 frame=@{level="3",addr="0x000107a4",func="foo",
29630 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29631 frame=@{level="4",addr="0x000107a4",func="foo",
29632 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29633 frame=@{level="5",addr="0x000107a4",func="foo",
29634 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29635 frame=@{level="6",addr="0x000107a4",func="foo",
29636 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29637 frame=@{level="7",addr="0x000107a4",func="foo",
29638 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29639 frame=@{level="8",addr="0x000107a4",func="foo",
29640 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29641 frame=@{level="9",addr="0x000107a4",func="foo",
29642 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29643 frame=@{level="10",addr="0x000107a4",func="foo",
29644 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29645 frame=@{level="11",addr="0x00010738",func="main",
29646 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
29650 Show frames between @var{low_frame} and @var{high_frame}:
29654 -stack-list-frames 3 5
29656 [frame=@{level="3",addr="0x000107a4",func="foo",
29657 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29658 frame=@{level="4",addr="0x000107a4",func="foo",
29659 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29660 frame=@{level="5",addr="0x000107a4",func="foo",
29661 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
29665 Show a single frame:
29669 -stack-list-frames 3 3
29671 [frame=@{level="3",addr="0x000107a4",func="foo",
29672 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
29677 @subheading The @code{-stack-list-locals} Command
29678 @findex -stack-list-locals
29680 @subsubheading Synopsis
29683 -stack-list-locals @var{print-values}
29686 Display the local variable names for the selected frame. If
29687 @var{print-values} is 0 or @code{--no-values}, print only the names of
29688 the variables; if it is 1 or @code{--all-values}, print also their
29689 values; and if it is 2 or @code{--simple-values}, print the name,
29690 type and value for simple data types, and the name and type for arrays,
29691 structures and unions. In this last case, a frontend can immediately
29692 display the value of simple data types and create variable objects for
29693 other data types when the user wishes to explore their values in
29696 This command is deprecated in favor of the
29697 @samp{-stack-list-variables} command.
29699 @subsubheading @value{GDBN} Command
29701 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
29703 @subsubheading Example
29707 -stack-list-locals 0
29708 ^done,locals=[name="A",name="B",name="C"]
29710 -stack-list-locals --all-values
29711 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
29712 @{name="C",value="@{1, 2, 3@}"@}]
29713 -stack-list-locals --simple-values
29714 ^done,locals=[@{name="A",type="int",value="1"@},
29715 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
29719 @subheading The @code{-stack-list-variables} Command
29720 @findex -stack-list-variables
29722 @subsubheading Synopsis
29725 -stack-list-variables @var{print-values}
29728 Display the names of local variables and function arguments for the selected frame. If
29729 @var{print-values} is 0 or @code{--no-values}, print only the names of
29730 the variables; if it is 1 or @code{--all-values}, print also their
29731 values; and if it is 2 or @code{--simple-values}, print the name,
29732 type and value for simple data types, and the name and type for arrays,
29733 structures and unions.
29735 @subsubheading Example
29739 -stack-list-variables --thread 1 --frame 0 --all-values
29740 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
29745 @subheading The @code{-stack-select-frame} Command
29746 @findex -stack-select-frame
29748 @subsubheading Synopsis
29751 -stack-select-frame @var{framenum}
29754 Change the selected frame. Select a different frame @var{framenum} on
29757 This command in deprecated in favor of passing the @samp{--frame}
29758 option to every command.
29760 @subsubheading @value{GDBN} Command
29762 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
29763 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
29765 @subsubheading Example
29769 -stack-select-frame 2
29774 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29775 @node GDB/MI Variable Objects
29776 @section @sc{gdb/mi} Variable Objects
29780 @subheading Motivation for Variable Objects in @sc{gdb/mi}
29782 For the implementation of a variable debugger window (locals, watched
29783 expressions, etc.), we are proposing the adaptation of the existing code
29784 used by @code{Insight}.
29786 The two main reasons for that are:
29790 It has been proven in practice (it is already on its second generation).
29793 It will shorten development time (needless to say how important it is
29797 The original interface was designed to be used by Tcl code, so it was
29798 slightly changed so it could be used through @sc{gdb/mi}. This section
29799 describes the @sc{gdb/mi} operations that will be available and gives some
29800 hints about their use.
29802 @emph{Note}: In addition to the set of operations described here, we
29803 expect the @sc{gui} implementation of a variable window to require, at
29804 least, the following operations:
29807 @item @code{-gdb-show} @code{output-radix}
29808 @item @code{-stack-list-arguments}
29809 @item @code{-stack-list-locals}
29810 @item @code{-stack-select-frame}
29815 @subheading Introduction to Variable Objects
29817 @cindex variable objects in @sc{gdb/mi}
29819 Variable objects are "object-oriented" MI interface for examining and
29820 changing values of expressions. Unlike some other MI interfaces that
29821 work with expressions, variable objects are specifically designed for
29822 simple and efficient presentation in the frontend. A variable object
29823 is identified by string name. When a variable object is created, the
29824 frontend specifies the expression for that variable object. The
29825 expression can be a simple variable, or it can be an arbitrary complex
29826 expression, and can even involve CPU registers. After creating a
29827 variable object, the frontend can invoke other variable object
29828 operations---for example to obtain or change the value of a variable
29829 object, or to change display format.
29831 Variable objects have hierarchical tree structure. Any variable object
29832 that corresponds to a composite type, such as structure in C, has
29833 a number of child variable objects, for example corresponding to each
29834 element of a structure. A child variable object can itself have
29835 children, recursively. Recursion ends when we reach
29836 leaf variable objects, which always have built-in types. Child variable
29837 objects are created only by explicit request, so if a frontend
29838 is not interested in the children of a particular variable object, no
29839 child will be created.
29841 For a leaf variable object it is possible to obtain its value as a
29842 string, or set the value from a string. String value can be also
29843 obtained for a non-leaf variable object, but it's generally a string
29844 that only indicates the type of the object, and does not list its
29845 contents. Assignment to a non-leaf variable object is not allowed.
29847 A frontend does not need to read the values of all variable objects each time
29848 the program stops. Instead, MI provides an update command that lists all
29849 variable objects whose values has changed since the last update
29850 operation. This considerably reduces the amount of data that must
29851 be transferred to the frontend. As noted above, children variable
29852 objects are created on demand, and only leaf variable objects have a
29853 real value. As result, gdb will read target memory only for leaf
29854 variables that frontend has created.
29856 The automatic update is not always desirable. For example, a frontend
29857 might want to keep a value of some expression for future reference,
29858 and never update it. For another example, fetching memory is
29859 relatively slow for embedded targets, so a frontend might want
29860 to disable automatic update for the variables that are either not
29861 visible on the screen, or ``closed''. This is possible using so
29862 called ``frozen variable objects''. Such variable objects are never
29863 implicitly updated.
29865 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
29866 fixed variable object, the expression is parsed when the variable
29867 object is created, including associating identifiers to specific
29868 variables. The meaning of expression never changes. For a floating
29869 variable object the values of variables whose names appear in the
29870 expressions are re-evaluated every time in the context of the current
29871 frame. Consider this example:
29876 struct work_state state;
29883 If a fixed variable object for the @code{state} variable is created in
29884 this function, and we enter the recursive call, the variable
29885 object will report the value of @code{state} in the top-level
29886 @code{do_work} invocation. On the other hand, a floating variable
29887 object will report the value of @code{state} in the current frame.
29889 If an expression specified when creating a fixed variable object
29890 refers to a local variable, the variable object becomes bound to the
29891 thread and frame in which the variable object is created. When such
29892 variable object is updated, @value{GDBN} makes sure that the
29893 thread/frame combination the variable object is bound to still exists,
29894 and re-evaluates the variable object in context of that thread/frame.
29896 The following is the complete set of @sc{gdb/mi} operations defined to
29897 access this functionality:
29899 @multitable @columnfractions .4 .6
29900 @item @strong{Operation}
29901 @tab @strong{Description}
29903 @item @code{-enable-pretty-printing}
29904 @tab enable Python-based pretty-printing
29905 @item @code{-var-create}
29906 @tab create a variable object
29907 @item @code{-var-delete}
29908 @tab delete the variable object and/or its children
29909 @item @code{-var-set-format}
29910 @tab set the display format of this variable
29911 @item @code{-var-show-format}
29912 @tab show the display format of this variable
29913 @item @code{-var-info-num-children}
29914 @tab tells how many children this object has
29915 @item @code{-var-list-children}
29916 @tab return a list of the object's children
29917 @item @code{-var-info-type}
29918 @tab show the type of this variable object
29919 @item @code{-var-info-expression}
29920 @tab print parent-relative expression that this variable object represents
29921 @item @code{-var-info-path-expression}
29922 @tab print full expression that this variable object represents
29923 @item @code{-var-show-attributes}
29924 @tab is this variable editable? does it exist here?
29925 @item @code{-var-evaluate-expression}
29926 @tab get the value of this variable
29927 @item @code{-var-assign}
29928 @tab set the value of this variable
29929 @item @code{-var-update}
29930 @tab update the variable and its children
29931 @item @code{-var-set-frozen}
29932 @tab set frozeness attribute
29933 @item @code{-var-set-update-range}
29934 @tab set range of children to display on update
29937 In the next subsection we describe each operation in detail and suggest
29938 how it can be used.
29940 @subheading Description And Use of Operations on Variable Objects
29942 @subheading The @code{-enable-pretty-printing} Command
29943 @findex -enable-pretty-printing
29946 -enable-pretty-printing
29949 @value{GDBN} allows Python-based visualizers to affect the output of the
29950 MI variable object commands. However, because there was no way to
29951 implement this in a fully backward-compatible way, a front end must
29952 request that this functionality be enabled.
29954 Once enabled, this feature cannot be disabled.
29956 Note that if Python support has not been compiled into @value{GDBN},
29957 this command will still succeed (and do nothing).
29959 This feature is currently (as of @value{GDBN} 7.0) experimental, and
29960 may work differently in future versions of @value{GDBN}.
29962 @subheading The @code{-var-create} Command
29963 @findex -var-create
29965 @subsubheading Synopsis
29968 -var-create @{@var{name} | "-"@}
29969 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
29972 This operation creates a variable object, which allows the monitoring of
29973 a variable, the result of an expression, a memory cell or a CPU
29976 The @var{name} parameter is the string by which the object can be
29977 referenced. It must be unique. If @samp{-} is specified, the varobj
29978 system will generate a string ``varNNNNNN'' automatically. It will be
29979 unique provided that one does not specify @var{name} of that format.
29980 The command fails if a duplicate name is found.
29982 The frame under which the expression should be evaluated can be
29983 specified by @var{frame-addr}. A @samp{*} indicates that the current
29984 frame should be used. A @samp{@@} indicates that a floating variable
29985 object must be created.
29987 @var{expression} is any expression valid on the current language set (must not
29988 begin with a @samp{*}), or one of the following:
29992 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
29995 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
29998 @samp{$@var{regname}} --- a CPU register name
30001 @cindex dynamic varobj
30002 A varobj's contents may be provided by a Python-based pretty-printer. In this
30003 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
30004 have slightly different semantics in some cases. If the
30005 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
30006 will never create a dynamic varobj. This ensures backward
30007 compatibility for existing clients.
30009 @subsubheading Result
30011 This operation returns attributes of the newly-created varobj. These
30016 The name of the varobj.
30019 The number of children of the varobj. This number is not necessarily
30020 reliable for a dynamic varobj. Instead, you must examine the
30021 @samp{has_more} attribute.
30024 The varobj's scalar value. For a varobj whose type is some sort of
30025 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
30026 will not be interesting.
30029 The varobj's type. This is a string representation of the type, as
30030 would be printed by the @value{GDBN} CLI. If @samp{print object}
30031 (@pxref{Print Settings, set print object}) is set to @code{on}, the
30032 @emph{actual} (derived) type of the object is shown rather than the
30033 @emph{declared} one.
30036 If a variable object is bound to a specific thread, then this is the
30037 thread's identifier.
30040 For a dynamic varobj, this indicates whether there appear to be any
30041 children available. For a non-dynamic varobj, this will be 0.
30044 This attribute will be present and have the value @samp{1} if the
30045 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30046 then this attribute will not be present.
30049 A dynamic varobj can supply a display hint to the front end. The
30050 value comes directly from the Python pretty-printer object's
30051 @code{display_hint} method. @xref{Pretty Printing API}.
30054 Typical output will look like this:
30057 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
30058 has_more="@var{has_more}"
30062 @subheading The @code{-var-delete} Command
30063 @findex -var-delete
30065 @subsubheading Synopsis
30068 -var-delete [ -c ] @var{name}
30071 Deletes a previously created variable object and all of its children.
30072 With the @samp{-c} option, just deletes the children.
30074 Returns an error if the object @var{name} is not found.
30077 @subheading The @code{-var-set-format} Command
30078 @findex -var-set-format
30080 @subsubheading Synopsis
30083 -var-set-format @var{name} @var{format-spec}
30086 Sets the output format for the value of the object @var{name} to be
30089 @anchor{-var-set-format}
30090 The syntax for the @var{format-spec} is as follows:
30093 @var{format-spec} @expansion{}
30094 @{binary | decimal | hexadecimal | octal | natural@}
30097 The natural format is the default format choosen automatically
30098 based on the variable type (like decimal for an @code{int}, hex
30099 for pointers, etc.).
30101 For a variable with children, the format is set only on the
30102 variable itself, and the children are not affected.
30104 @subheading The @code{-var-show-format} Command
30105 @findex -var-show-format
30107 @subsubheading Synopsis
30110 -var-show-format @var{name}
30113 Returns the format used to display the value of the object @var{name}.
30116 @var{format} @expansion{}
30121 @subheading The @code{-var-info-num-children} Command
30122 @findex -var-info-num-children
30124 @subsubheading Synopsis
30127 -var-info-num-children @var{name}
30130 Returns the number of children of a variable object @var{name}:
30136 Note that this number is not completely reliable for a dynamic varobj.
30137 It will return the current number of children, but more children may
30141 @subheading The @code{-var-list-children} Command
30142 @findex -var-list-children
30144 @subsubheading Synopsis
30147 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
30149 @anchor{-var-list-children}
30151 Return a list of the children of the specified variable object and
30152 create variable objects for them, if they do not already exist. With
30153 a single argument or if @var{print-values} has a value of 0 or
30154 @code{--no-values}, print only the names of the variables; if
30155 @var{print-values} is 1 or @code{--all-values}, also print their
30156 values; and if it is 2 or @code{--simple-values} print the name and
30157 value for simple data types and just the name for arrays, structures
30160 @var{from} and @var{to}, if specified, indicate the range of children
30161 to report. If @var{from} or @var{to} is less than zero, the range is
30162 reset and all children will be reported. Otherwise, children starting
30163 at @var{from} (zero-based) and up to and excluding @var{to} will be
30166 If a child range is requested, it will only affect the current call to
30167 @code{-var-list-children}, but not future calls to @code{-var-update}.
30168 For this, you must instead use @code{-var-set-update-range}. The
30169 intent of this approach is to enable a front end to implement any
30170 update approach it likes; for example, scrolling a view may cause the
30171 front end to request more children with @code{-var-list-children}, and
30172 then the front end could call @code{-var-set-update-range} with a
30173 different range to ensure that future updates are restricted to just
30176 For each child the following results are returned:
30181 Name of the variable object created for this child.
30184 The expression to be shown to the user by the front end to designate this child.
30185 For example this may be the name of a structure member.
30187 For a dynamic varobj, this value cannot be used to form an
30188 expression. There is no way to do this at all with a dynamic varobj.
30190 For C/C@t{++} structures there are several pseudo children returned to
30191 designate access qualifiers. For these pseudo children @var{exp} is
30192 @samp{public}, @samp{private}, or @samp{protected}. In this case the
30193 type and value are not present.
30195 A dynamic varobj will not report the access qualifying
30196 pseudo-children, regardless of the language. This information is not
30197 available at all with a dynamic varobj.
30200 Number of children this child has. For a dynamic varobj, this will be
30204 The type of the child. If @samp{print object}
30205 (@pxref{Print Settings, set print object}) is set to @code{on}, the
30206 @emph{actual} (derived) type of the object is shown rather than the
30207 @emph{declared} one.
30210 If values were requested, this is the value.
30213 If this variable object is associated with a thread, this is the thread id.
30214 Otherwise this result is not present.
30217 If the variable object is frozen, this variable will be present with a value of 1.
30220 The result may have its own attributes:
30224 A dynamic varobj can supply a display hint to the front end. The
30225 value comes directly from the Python pretty-printer object's
30226 @code{display_hint} method. @xref{Pretty Printing API}.
30229 This is an integer attribute which is nonzero if there are children
30230 remaining after the end of the selected range.
30233 @subsubheading Example
30237 -var-list-children n
30238 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30239 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
30241 -var-list-children --all-values n
30242 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30243 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
30247 @subheading The @code{-var-info-type} Command
30248 @findex -var-info-type
30250 @subsubheading Synopsis
30253 -var-info-type @var{name}
30256 Returns the type of the specified variable @var{name}. The type is
30257 returned as a string in the same format as it is output by the
30261 type=@var{typename}
30265 @subheading The @code{-var-info-expression} Command
30266 @findex -var-info-expression
30268 @subsubheading Synopsis
30271 -var-info-expression @var{name}
30274 Returns a string that is suitable for presenting this
30275 variable object in user interface. The string is generally
30276 not valid expression in the current language, and cannot be evaluated.
30278 For example, if @code{a} is an array, and variable object
30279 @code{A} was created for @code{a}, then we'll get this output:
30282 (gdb) -var-info-expression A.1
30283 ^done,lang="C",exp="1"
30287 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
30289 Note that the output of the @code{-var-list-children} command also
30290 includes those expressions, so the @code{-var-info-expression} command
30293 @subheading The @code{-var-info-path-expression} Command
30294 @findex -var-info-path-expression
30296 @subsubheading Synopsis
30299 -var-info-path-expression @var{name}
30302 Returns an expression that can be evaluated in the current
30303 context and will yield the same value that a variable object has.
30304 Compare this with the @code{-var-info-expression} command, which
30305 result can be used only for UI presentation. Typical use of
30306 the @code{-var-info-path-expression} command is creating a
30307 watchpoint from a variable object.
30309 This command is currently not valid for children of a dynamic varobj,
30310 and will give an error when invoked on one.
30312 For example, suppose @code{C} is a C@t{++} class, derived from class
30313 @code{Base}, and that the @code{Base} class has a member called
30314 @code{m_size}. Assume a variable @code{c} is has the type of
30315 @code{C} and a variable object @code{C} was created for variable
30316 @code{c}. Then, we'll get this output:
30318 (gdb) -var-info-path-expression C.Base.public.m_size
30319 ^done,path_expr=((Base)c).m_size)
30322 @subheading The @code{-var-show-attributes} Command
30323 @findex -var-show-attributes
30325 @subsubheading Synopsis
30328 -var-show-attributes @var{name}
30331 List attributes of the specified variable object @var{name}:
30334 status=@var{attr} [ ( ,@var{attr} )* ]
30338 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
30340 @subheading The @code{-var-evaluate-expression} Command
30341 @findex -var-evaluate-expression
30343 @subsubheading Synopsis
30346 -var-evaluate-expression [-f @var{format-spec}] @var{name}
30349 Evaluates the expression that is represented by the specified variable
30350 object and returns its value as a string. The format of the string
30351 can be specified with the @samp{-f} option. The possible values of
30352 this option are the same as for @code{-var-set-format}
30353 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
30354 the current display format will be used. The current display format
30355 can be changed using the @code{-var-set-format} command.
30361 Note that one must invoke @code{-var-list-children} for a variable
30362 before the value of a child variable can be evaluated.
30364 @subheading The @code{-var-assign} Command
30365 @findex -var-assign
30367 @subsubheading Synopsis
30370 -var-assign @var{name} @var{expression}
30373 Assigns the value of @var{expression} to the variable object specified
30374 by @var{name}. The object must be @samp{editable}. If the variable's
30375 value is altered by the assign, the variable will show up in any
30376 subsequent @code{-var-update} list.
30378 @subsubheading Example
30386 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
30390 @subheading The @code{-var-update} Command
30391 @findex -var-update
30393 @subsubheading Synopsis
30396 -var-update [@var{print-values}] @{@var{name} | "*"@}
30399 Reevaluate the expressions corresponding to the variable object
30400 @var{name} and all its direct and indirect children, and return the
30401 list of variable objects whose values have changed; @var{name} must
30402 be a root variable object. Here, ``changed'' means that the result of
30403 @code{-var-evaluate-expression} before and after the
30404 @code{-var-update} is different. If @samp{*} is used as the variable
30405 object names, all existing variable objects are updated, except
30406 for frozen ones (@pxref{-var-set-frozen}). The option
30407 @var{print-values} determines whether both names and values, or just
30408 names are printed. The possible values of this option are the same
30409 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
30410 recommended to use the @samp{--all-values} option, to reduce the
30411 number of MI commands needed on each program stop.
30413 With the @samp{*} parameter, if a variable object is bound to a
30414 currently running thread, it will not be updated, without any
30417 If @code{-var-set-update-range} was previously used on a varobj, then
30418 only the selected range of children will be reported.
30420 @code{-var-update} reports all the changed varobjs in a tuple named
30423 Each item in the change list is itself a tuple holding:
30427 The name of the varobj.
30430 If values were requested for this update, then this field will be
30431 present and will hold the value of the varobj.
30434 @anchor{-var-update}
30435 This field is a string which may take one of three values:
30439 The variable object's current value is valid.
30442 The variable object does not currently hold a valid value but it may
30443 hold one in the future if its associated expression comes back into
30447 The variable object no longer holds a valid value.
30448 This can occur when the executable file being debugged has changed,
30449 either through recompilation or by using the @value{GDBN} @code{file}
30450 command. The front end should normally choose to delete these variable
30454 In the future new values may be added to this list so the front should
30455 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
30458 This is only present if the varobj is still valid. If the type
30459 changed, then this will be the string @samp{true}; otherwise it will
30462 When a varobj's type changes, its children are also likely to have
30463 become incorrect. Therefore, the varobj's children are automatically
30464 deleted when this attribute is @samp{true}. Also, the varobj's update
30465 range, when set using the @code{-var-set-update-range} command, is
30469 If the varobj's type changed, then this field will be present and will
30472 @item new_num_children
30473 For a dynamic varobj, if the number of children changed, or if the
30474 type changed, this will be the new number of children.
30476 The @samp{numchild} field in other varobj responses is generally not
30477 valid for a dynamic varobj -- it will show the number of children that
30478 @value{GDBN} knows about, but because dynamic varobjs lazily
30479 instantiate their children, this will not reflect the number of
30480 children which may be available.
30482 The @samp{new_num_children} attribute only reports changes to the
30483 number of children known by @value{GDBN}. This is the only way to
30484 detect whether an update has removed children (which necessarily can
30485 only happen at the end of the update range).
30488 The display hint, if any.
30491 This is an integer value, which will be 1 if there are more children
30492 available outside the varobj's update range.
30495 This attribute will be present and have the value @samp{1} if the
30496 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30497 then this attribute will not be present.
30500 If new children were added to a dynamic varobj within the selected
30501 update range (as set by @code{-var-set-update-range}), then they will
30502 be listed in this attribute.
30505 @subsubheading Example
30512 -var-update --all-values var1
30513 ^done,changelist=[@{name="var1",value="3",in_scope="true",
30514 type_changed="false"@}]
30518 @subheading The @code{-var-set-frozen} Command
30519 @findex -var-set-frozen
30520 @anchor{-var-set-frozen}
30522 @subsubheading Synopsis
30525 -var-set-frozen @var{name} @var{flag}
30528 Set the frozenness flag on the variable object @var{name}. The
30529 @var{flag} parameter should be either @samp{1} to make the variable
30530 frozen or @samp{0} to make it unfrozen. If a variable object is
30531 frozen, then neither itself, nor any of its children, are
30532 implicitly updated by @code{-var-update} of
30533 a parent variable or by @code{-var-update *}. Only
30534 @code{-var-update} of the variable itself will update its value and
30535 values of its children. After a variable object is unfrozen, it is
30536 implicitly updated by all subsequent @code{-var-update} operations.
30537 Unfreezing a variable does not update it, only subsequent
30538 @code{-var-update} does.
30540 @subsubheading Example
30544 -var-set-frozen V 1
30549 @subheading The @code{-var-set-update-range} command
30550 @findex -var-set-update-range
30551 @anchor{-var-set-update-range}
30553 @subsubheading Synopsis
30556 -var-set-update-range @var{name} @var{from} @var{to}
30559 Set the range of children to be returned by future invocations of
30560 @code{-var-update}.
30562 @var{from} and @var{to} indicate the range of children to report. If
30563 @var{from} or @var{to} is less than zero, the range is reset and all
30564 children will be reported. Otherwise, children starting at @var{from}
30565 (zero-based) and up to and excluding @var{to} will be reported.
30567 @subsubheading Example
30571 -var-set-update-range V 1 2
30575 @subheading The @code{-var-set-visualizer} command
30576 @findex -var-set-visualizer
30577 @anchor{-var-set-visualizer}
30579 @subsubheading Synopsis
30582 -var-set-visualizer @var{name} @var{visualizer}
30585 Set a visualizer for the variable object @var{name}.
30587 @var{visualizer} is the visualizer to use. The special value
30588 @samp{None} means to disable any visualizer in use.
30590 If not @samp{None}, @var{visualizer} must be a Python expression.
30591 This expression must evaluate to a callable object which accepts a
30592 single argument. @value{GDBN} will call this object with the value of
30593 the varobj @var{name} as an argument (this is done so that the same
30594 Python pretty-printing code can be used for both the CLI and MI).
30595 When called, this object must return an object which conforms to the
30596 pretty-printing interface (@pxref{Pretty Printing API}).
30598 The pre-defined function @code{gdb.default_visualizer} may be used to
30599 select a visualizer by following the built-in process
30600 (@pxref{Selecting Pretty-Printers}). This is done automatically when
30601 a varobj is created, and so ordinarily is not needed.
30603 This feature is only available if Python support is enabled. The MI
30604 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
30605 can be used to check this.
30607 @subsubheading Example
30609 Resetting the visualizer:
30613 -var-set-visualizer V None
30617 Reselecting the default (type-based) visualizer:
30621 -var-set-visualizer V gdb.default_visualizer
30625 Suppose @code{SomeClass} is a visualizer class. A lambda expression
30626 can be used to instantiate this class for a varobj:
30630 -var-set-visualizer V "lambda val: SomeClass()"
30634 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30635 @node GDB/MI Data Manipulation
30636 @section @sc{gdb/mi} Data Manipulation
30638 @cindex data manipulation, in @sc{gdb/mi}
30639 @cindex @sc{gdb/mi}, data manipulation
30640 This section describes the @sc{gdb/mi} commands that manipulate data:
30641 examine memory and registers, evaluate expressions, etc.
30643 @c REMOVED FROM THE INTERFACE.
30644 @c @subheading -data-assign
30645 @c Change the value of a program variable. Plenty of side effects.
30646 @c @subsubheading GDB Command
30648 @c @subsubheading Example
30651 @subheading The @code{-data-disassemble} Command
30652 @findex -data-disassemble
30654 @subsubheading Synopsis
30658 [ -s @var{start-addr} -e @var{end-addr} ]
30659 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
30667 @item @var{start-addr}
30668 is the beginning address (or @code{$pc})
30669 @item @var{end-addr}
30671 @item @var{filename}
30672 is the name of the file to disassemble
30673 @item @var{linenum}
30674 is the line number to disassemble around
30676 is the number of disassembly lines to be produced. If it is -1,
30677 the whole function will be disassembled, in case no @var{end-addr} is
30678 specified. If @var{end-addr} is specified as a non-zero value, and
30679 @var{lines} is lower than the number of disassembly lines between
30680 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
30681 displayed; if @var{lines} is higher than the number of lines between
30682 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
30685 is either 0 (meaning only disassembly), 1 (meaning mixed source and
30686 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
30687 mixed source and disassembly with raw opcodes).
30690 @subsubheading Result
30692 The output for each instruction is composed of four fields:
30701 Note that whatever included in the instruction field, is not manipulated
30702 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
30704 @subsubheading @value{GDBN} Command
30706 There's no direct mapping from this command to the CLI.
30708 @subsubheading Example
30710 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
30714 -data-disassemble -s $pc -e "$pc + 20" -- 0
30717 @{address="0x000107c0",func-name="main",offset="4",
30718 inst="mov 2, %o0"@},
30719 @{address="0x000107c4",func-name="main",offset="8",
30720 inst="sethi %hi(0x11800), %o2"@},
30721 @{address="0x000107c8",func-name="main",offset="12",
30722 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
30723 @{address="0x000107cc",func-name="main",offset="16",
30724 inst="sethi %hi(0x11800), %o2"@},
30725 @{address="0x000107d0",func-name="main",offset="20",
30726 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
30730 Disassemble the whole @code{main} function. Line 32 is part of
30734 -data-disassemble -f basics.c -l 32 -- 0
30736 @{address="0x000107bc",func-name="main",offset="0",
30737 inst="save %sp, -112, %sp"@},
30738 @{address="0x000107c0",func-name="main",offset="4",
30739 inst="mov 2, %o0"@},
30740 @{address="0x000107c4",func-name="main",offset="8",
30741 inst="sethi %hi(0x11800), %o2"@},
30743 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
30744 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
30748 Disassemble 3 instructions from the start of @code{main}:
30752 -data-disassemble -f basics.c -l 32 -n 3 -- 0
30754 @{address="0x000107bc",func-name="main",offset="0",
30755 inst="save %sp, -112, %sp"@},
30756 @{address="0x000107c0",func-name="main",offset="4",
30757 inst="mov 2, %o0"@},
30758 @{address="0x000107c4",func-name="main",offset="8",
30759 inst="sethi %hi(0x11800), %o2"@}]
30763 Disassemble 3 instructions from the start of @code{main} in mixed mode:
30767 -data-disassemble -f basics.c -l 32 -n 3 -- 1
30769 src_and_asm_line=@{line="31",
30770 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
30771 testsuite/gdb.mi/basics.c",line_asm_insn=[
30772 @{address="0x000107bc",func-name="main",offset="0",
30773 inst="save %sp, -112, %sp"@}]@},
30774 src_and_asm_line=@{line="32",
30775 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
30776 testsuite/gdb.mi/basics.c",line_asm_insn=[
30777 @{address="0x000107c0",func-name="main",offset="4",
30778 inst="mov 2, %o0"@},
30779 @{address="0x000107c4",func-name="main",offset="8",
30780 inst="sethi %hi(0x11800), %o2"@}]@}]
30785 @subheading The @code{-data-evaluate-expression} Command
30786 @findex -data-evaluate-expression
30788 @subsubheading Synopsis
30791 -data-evaluate-expression @var{expr}
30794 Evaluate @var{expr} as an expression. The expression could contain an
30795 inferior function call. The function call will execute synchronously.
30796 If the expression contains spaces, it must be enclosed in double quotes.
30798 @subsubheading @value{GDBN} Command
30800 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
30801 @samp{call}. In @code{gdbtk} only, there's a corresponding
30802 @samp{gdb_eval} command.
30804 @subsubheading Example
30806 In the following example, the numbers that precede the commands are the
30807 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
30808 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
30812 211-data-evaluate-expression A
30815 311-data-evaluate-expression &A
30816 311^done,value="0xefffeb7c"
30818 411-data-evaluate-expression A+3
30821 511-data-evaluate-expression "A + 3"
30827 @subheading The @code{-data-list-changed-registers} Command
30828 @findex -data-list-changed-registers
30830 @subsubheading Synopsis
30833 -data-list-changed-registers
30836 Display a list of the registers that have changed.
30838 @subsubheading @value{GDBN} Command
30840 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
30841 has the corresponding command @samp{gdb_changed_register_list}.
30843 @subsubheading Example
30845 On a PPC MBX board:
30853 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
30854 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
30857 -data-list-changed-registers
30858 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
30859 "10","11","13","14","15","16","17","18","19","20","21","22","23",
30860 "24","25","26","27","28","30","31","64","65","66","67","69"]
30865 @subheading The @code{-data-list-register-names} Command
30866 @findex -data-list-register-names
30868 @subsubheading Synopsis
30871 -data-list-register-names [ ( @var{regno} )+ ]
30874 Show a list of register names for the current target. If no arguments
30875 are given, it shows a list of the names of all the registers. If
30876 integer numbers are given as arguments, it will print a list of the
30877 names of the registers corresponding to the arguments. To ensure
30878 consistency between a register name and its number, the output list may
30879 include empty register names.
30881 @subsubheading @value{GDBN} Command
30883 @value{GDBN} does not have a command which corresponds to
30884 @samp{-data-list-register-names}. In @code{gdbtk} there is a
30885 corresponding command @samp{gdb_regnames}.
30887 @subsubheading Example
30889 For the PPC MBX board:
30892 -data-list-register-names
30893 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
30894 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
30895 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
30896 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
30897 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
30898 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
30899 "", "pc","ps","cr","lr","ctr","xer"]
30901 -data-list-register-names 1 2 3
30902 ^done,register-names=["r1","r2","r3"]
30906 @subheading The @code{-data-list-register-values} Command
30907 @findex -data-list-register-values
30909 @subsubheading Synopsis
30912 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
30915 Display the registers' contents. @var{fmt} is the format according to
30916 which the registers' contents are to be returned, followed by an optional
30917 list of numbers specifying the registers to display. A missing list of
30918 numbers indicates that the contents of all the registers must be returned.
30920 Allowed formats for @var{fmt} are:
30937 @subsubheading @value{GDBN} Command
30939 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
30940 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
30942 @subsubheading Example
30944 For a PPC MBX board (note: line breaks are for readability only, they
30945 don't appear in the actual output):
30949 -data-list-register-values r 64 65
30950 ^done,register-values=[@{number="64",value="0xfe00a300"@},
30951 @{number="65",value="0x00029002"@}]
30953 -data-list-register-values x
30954 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
30955 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
30956 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
30957 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
30958 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
30959 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
30960 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
30961 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
30962 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
30963 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
30964 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
30965 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
30966 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
30967 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
30968 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
30969 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
30970 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
30971 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
30972 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
30973 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
30974 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
30975 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
30976 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
30977 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
30978 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
30979 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
30980 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
30981 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
30982 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
30983 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
30984 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
30985 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
30986 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
30987 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
30988 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
30989 @{number="69",value="0x20002b03"@}]
30994 @subheading The @code{-data-read-memory} Command
30995 @findex -data-read-memory
30997 This command is deprecated, use @code{-data-read-memory-bytes} instead.
30999 @subsubheading Synopsis
31002 -data-read-memory [ -o @var{byte-offset} ]
31003 @var{address} @var{word-format} @var{word-size}
31004 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
31011 @item @var{address}
31012 An expression specifying the address of the first memory word to be
31013 read. Complex expressions containing embedded white space should be
31014 quoted using the C convention.
31016 @item @var{word-format}
31017 The format to be used to print the memory words. The notation is the
31018 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
31021 @item @var{word-size}
31022 The size of each memory word in bytes.
31024 @item @var{nr-rows}
31025 The number of rows in the output table.
31027 @item @var{nr-cols}
31028 The number of columns in the output table.
31031 If present, indicates that each row should include an @sc{ascii} dump. The
31032 value of @var{aschar} is used as a padding character when a byte is not a
31033 member of the printable @sc{ascii} character set (printable @sc{ascii}
31034 characters are those whose code is between 32 and 126, inclusively).
31036 @item @var{byte-offset}
31037 An offset to add to the @var{address} before fetching memory.
31040 This command displays memory contents as a table of @var{nr-rows} by
31041 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
31042 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
31043 (returned as @samp{total-bytes}). Should less than the requested number
31044 of bytes be returned by the target, the missing words are identified
31045 using @samp{N/A}. The number of bytes read from the target is returned
31046 in @samp{nr-bytes} and the starting address used to read memory in
31049 The address of the next/previous row or page is available in
31050 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
31053 @subsubheading @value{GDBN} Command
31055 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
31056 @samp{gdb_get_mem} memory read command.
31058 @subsubheading Example
31060 Read six bytes of memory starting at @code{bytes+6} but then offset by
31061 @code{-6} bytes. Format as three rows of two columns. One byte per
31062 word. Display each word in hex.
31066 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
31067 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
31068 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
31069 prev-page="0x0000138a",memory=[
31070 @{addr="0x00001390",data=["0x00","0x01"]@},
31071 @{addr="0x00001392",data=["0x02","0x03"]@},
31072 @{addr="0x00001394",data=["0x04","0x05"]@}]
31076 Read two bytes of memory starting at address @code{shorts + 64} and
31077 display as a single word formatted in decimal.
31081 5-data-read-memory shorts+64 d 2 1 1
31082 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
31083 next-row="0x00001512",prev-row="0x0000150e",
31084 next-page="0x00001512",prev-page="0x0000150e",memory=[
31085 @{addr="0x00001510",data=["128"]@}]
31089 Read thirty two bytes of memory starting at @code{bytes+16} and format
31090 as eight rows of four columns. Include a string encoding with @samp{x}
31091 used as the non-printable character.
31095 4-data-read-memory bytes+16 x 1 8 4 x
31096 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
31097 next-row="0x000013c0",prev-row="0x0000139c",
31098 next-page="0x000013c0",prev-page="0x00001380",memory=[
31099 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
31100 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
31101 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
31102 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
31103 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
31104 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
31105 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
31106 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
31110 @subheading The @code{-data-read-memory-bytes} Command
31111 @findex -data-read-memory-bytes
31113 @subsubheading Synopsis
31116 -data-read-memory-bytes [ -o @var{byte-offset} ]
31117 @var{address} @var{count}
31124 @item @var{address}
31125 An expression specifying the address of the first memory word to be
31126 read. Complex expressions containing embedded white space should be
31127 quoted using the C convention.
31130 The number of bytes to read. This should be an integer literal.
31132 @item @var{byte-offset}
31133 The offsets in bytes relative to @var{address} at which to start
31134 reading. This should be an integer literal. This option is provided
31135 so that a frontend is not required to first evaluate address and then
31136 perform address arithmetics itself.
31140 This command attempts to read all accessible memory regions in the
31141 specified range. First, all regions marked as unreadable in the memory
31142 map (if one is defined) will be skipped. @xref{Memory Region
31143 Attributes}. Second, @value{GDBN} will attempt to read the remaining
31144 regions. For each one, if reading full region results in an errors,
31145 @value{GDBN} will try to read a subset of the region.
31147 In general, every single byte in the region may be readable or not,
31148 and the only way to read every readable byte is to try a read at
31149 every address, which is not practical. Therefore, @value{GDBN} will
31150 attempt to read all accessible bytes at either beginning or the end
31151 of the region, using a binary division scheme. This heuristic works
31152 well for reading accross a memory map boundary. Note that if a region
31153 has a readable range that is neither at the beginning or the end,
31154 @value{GDBN} will not read it.
31156 The result record (@pxref{GDB/MI Result Records}) that is output of
31157 the command includes a field named @samp{memory} whose content is a
31158 list of tuples. Each tuple represent a successfully read memory block
31159 and has the following fields:
31163 The start address of the memory block, as hexadecimal literal.
31166 The end address of the memory block, as hexadecimal literal.
31169 The offset of the memory block, as hexadecimal literal, relative to
31170 the start address passed to @code{-data-read-memory-bytes}.
31173 The contents of the memory block, in hex.
31179 @subsubheading @value{GDBN} Command
31181 The corresponding @value{GDBN} command is @samp{x}.
31183 @subsubheading Example
31187 -data-read-memory-bytes &a 10
31188 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
31190 contents="01000000020000000300"@}]
31195 @subheading The @code{-data-write-memory-bytes} Command
31196 @findex -data-write-memory-bytes
31198 @subsubheading Synopsis
31201 -data-write-memory-bytes @var{address} @var{contents}
31208 @item @var{address}
31209 An expression specifying the address of the first memory word to be
31210 read. Complex expressions containing embedded white space should be
31211 quoted using the C convention.
31213 @item @var{contents}
31214 The hex-encoded bytes to write.
31218 @subsubheading @value{GDBN} Command
31220 There's no corresponding @value{GDBN} command.
31222 @subsubheading Example
31226 -data-write-memory-bytes &a "aabbccdd"
31232 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31233 @node GDB/MI Tracepoint Commands
31234 @section @sc{gdb/mi} Tracepoint Commands
31236 The commands defined in this section implement MI support for
31237 tracepoints. For detailed introduction, see @ref{Tracepoints}.
31239 @subheading The @code{-trace-find} Command
31240 @findex -trace-find
31242 @subsubheading Synopsis
31245 -trace-find @var{mode} [@var{parameters}@dots{}]
31248 Find a trace frame using criteria defined by @var{mode} and
31249 @var{parameters}. The following table lists permissible
31250 modes and their parameters. For details of operation, see @ref{tfind}.
31255 No parameters are required. Stops examining trace frames.
31258 An integer is required as parameter. Selects tracepoint frame with
31261 @item tracepoint-number
31262 An integer is required as parameter. Finds next
31263 trace frame that corresponds to tracepoint with the specified number.
31266 An address is required as parameter. Finds
31267 next trace frame that corresponds to any tracepoint at the specified
31270 @item pc-inside-range
31271 Two addresses are required as parameters. Finds next trace
31272 frame that corresponds to a tracepoint at an address inside the
31273 specified range. Both bounds are considered to be inside the range.
31275 @item pc-outside-range
31276 Two addresses are required as parameters. Finds
31277 next trace frame that corresponds to a tracepoint at an address outside
31278 the specified range. Both bounds are considered to be inside the range.
31281 Line specification is required as parameter. @xref{Specify Location}.
31282 Finds next trace frame that corresponds to a tracepoint at
31283 the specified location.
31287 If @samp{none} was passed as @var{mode}, the response does not
31288 have fields. Otherwise, the response may have the following fields:
31292 This field has either @samp{0} or @samp{1} as the value, depending
31293 on whether a matching tracepoint was found.
31296 The index of the found traceframe. This field is present iff
31297 the @samp{found} field has value of @samp{1}.
31300 The index of the found tracepoint. This field is present iff
31301 the @samp{found} field has value of @samp{1}.
31304 The information about the frame corresponding to the found trace
31305 frame. This field is present only if a trace frame was found.
31306 @xref{GDB/MI Frame Information}, for description of this field.
31310 @subsubheading @value{GDBN} Command
31312 The corresponding @value{GDBN} command is @samp{tfind}.
31314 @subheading -trace-define-variable
31315 @findex -trace-define-variable
31317 @subsubheading Synopsis
31320 -trace-define-variable @var{name} [ @var{value} ]
31323 Create trace variable @var{name} if it does not exist. If
31324 @var{value} is specified, sets the initial value of the specified
31325 trace variable to that value. Note that the @var{name} should start
31326 with the @samp{$} character.
31328 @subsubheading @value{GDBN} Command
31330 The corresponding @value{GDBN} command is @samp{tvariable}.
31332 @subheading -trace-list-variables
31333 @findex -trace-list-variables
31335 @subsubheading Synopsis
31338 -trace-list-variables
31341 Return a table of all defined trace variables. Each element of the
31342 table has the following fields:
31346 The name of the trace variable. This field is always present.
31349 The initial value. This is a 64-bit signed integer. This
31350 field is always present.
31353 The value the trace variable has at the moment. This is a 64-bit
31354 signed integer. This field is absent iff current value is
31355 not defined, for example if the trace was never run, or is
31360 @subsubheading @value{GDBN} Command
31362 The corresponding @value{GDBN} command is @samp{tvariables}.
31364 @subsubheading Example
31368 -trace-list-variables
31369 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
31370 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
31371 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
31372 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
31373 body=[variable=@{name="$trace_timestamp",initial="0"@}
31374 variable=@{name="$foo",initial="10",current="15"@}]@}
31378 @subheading -trace-save
31379 @findex -trace-save
31381 @subsubheading Synopsis
31384 -trace-save [-r ] @var{filename}
31387 Saves the collected trace data to @var{filename}. Without the
31388 @samp{-r} option, the data is downloaded from the target and saved
31389 in a local file. With the @samp{-r} option the target is asked
31390 to perform the save.
31392 @subsubheading @value{GDBN} Command
31394 The corresponding @value{GDBN} command is @samp{tsave}.
31397 @subheading -trace-start
31398 @findex -trace-start
31400 @subsubheading Synopsis
31406 Starts a tracing experiments. The result of this command does not
31409 @subsubheading @value{GDBN} Command
31411 The corresponding @value{GDBN} command is @samp{tstart}.
31413 @subheading -trace-status
31414 @findex -trace-status
31416 @subsubheading Synopsis
31422 Obtains the status of a tracing experiment. The result may include
31423 the following fields:
31428 May have a value of either @samp{0}, when no tracing operations are
31429 supported, @samp{1}, when all tracing operations are supported, or
31430 @samp{file} when examining trace file. In the latter case, examining
31431 of trace frame is possible but new tracing experiement cannot be
31432 started. This field is always present.
31435 May have a value of either @samp{0} or @samp{1} depending on whether
31436 tracing experiement is in progress on target. This field is present
31437 if @samp{supported} field is not @samp{0}.
31440 Report the reason why the tracing was stopped last time. This field
31441 may be absent iff tracing was never stopped on target yet. The
31442 value of @samp{request} means the tracing was stopped as result of
31443 the @code{-trace-stop} command. The value of @samp{overflow} means
31444 the tracing buffer is full. The value of @samp{disconnection} means
31445 tracing was automatically stopped when @value{GDBN} has disconnected.
31446 The value of @samp{passcount} means tracing was stopped when a
31447 tracepoint was passed a maximal number of times for that tracepoint.
31448 This field is present if @samp{supported} field is not @samp{0}.
31450 @item stopping-tracepoint
31451 The number of tracepoint whose passcount as exceeded. This field is
31452 present iff the @samp{stop-reason} field has the value of
31456 @itemx frames-created
31457 The @samp{frames} field is a count of the total number of trace frames
31458 in the trace buffer, while @samp{frames-created} is the total created
31459 during the run, including ones that were discarded, such as when a
31460 circular trace buffer filled up. Both fields are optional.
31464 These fields tell the current size of the tracing buffer and the
31465 remaining space. These fields are optional.
31468 The value of the circular trace buffer flag. @code{1} means that the
31469 trace buffer is circular and old trace frames will be discarded if
31470 necessary to make room, @code{0} means that the trace buffer is linear
31474 The value of the disconnected tracing flag. @code{1} means that
31475 tracing will continue after @value{GDBN} disconnects, @code{0} means
31476 that the trace run will stop.
31480 @subsubheading @value{GDBN} Command
31482 The corresponding @value{GDBN} command is @samp{tstatus}.
31484 @subheading -trace-stop
31485 @findex -trace-stop
31487 @subsubheading Synopsis
31493 Stops a tracing experiment. The result of this command has the same
31494 fields as @code{-trace-status}, except that the @samp{supported} and
31495 @samp{running} fields are not output.
31497 @subsubheading @value{GDBN} Command
31499 The corresponding @value{GDBN} command is @samp{tstop}.
31502 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31503 @node GDB/MI Symbol Query
31504 @section @sc{gdb/mi} Symbol Query Commands
31508 @subheading The @code{-symbol-info-address} Command
31509 @findex -symbol-info-address
31511 @subsubheading Synopsis
31514 -symbol-info-address @var{symbol}
31517 Describe where @var{symbol} is stored.
31519 @subsubheading @value{GDBN} Command
31521 The corresponding @value{GDBN} command is @samp{info address}.
31523 @subsubheading Example
31527 @subheading The @code{-symbol-info-file} Command
31528 @findex -symbol-info-file
31530 @subsubheading Synopsis
31536 Show the file for the symbol.
31538 @subsubheading @value{GDBN} Command
31540 There's no equivalent @value{GDBN} command. @code{gdbtk} has
31541 @samp{gdb_find_file}.
31543 @subsubheading Example
31547 @subheading The @code{-symbol-info-function} Command
31548 @findex -symbol-info-function
31550 @subsubheading Synopsis
31553 -symbol-info-function
31556 Show which function the symbol lives in.
31558 @subsubheading @value{GDBN} Command
31560 @samp{gdb_get_function} in @code{gdbtk}.
31562 @subsubheading Example
31566 @subheading The @code{-symbol-info-line} Command
31567 @findex -symbol-info-line
31569 @subsubheading Synopsis
31575 Show the core addresses of the code for a source line.
31577 @subsubheading @value{GDBN} Command
31579 The corresponding @value{GDBN} command is @samp{info line}.
31580 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
31582 @subsubheading Example
31586 @subheading The @code{-symbol-info-symbol} Command
31587 @findex -symbol-info-symbol
31589 @subsubheading Synopsis
31592 -symbol-info-symbol @var{addr}
31595 Describe what symbol is at location @var{addr}.
31597 @subsubheading @value{GDBN} Command
31599 The corresponding @value{GDBN} command is @samp{info symbol}.
31601 @subsubheading Example
31605 @subheading The @code{-symbol-list-functions} Command
31606 @findex -symbol-list-functions
31608 @subsubheading Synopsis
31611 -symbol-list-functions
31614 List the functions in the executable.
31616 @subsubheading @value{GDBN} Command
31618 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
31619 @samp{gdb_search} in @code{gdbtk}.
31621 @subsubheading Example
31626 @subheading The @code{-symbol-list-lines} Command
31627 @findex -symbol-list-lines
31629 @subsubheading Synopsis
31632 -symbol-list-lines @var{filename}
31635 Print the list of lines that contain code and their associated program
31636 addresses for the given source filename. The entries are sorted in
31637 ascending PC order.
31639 @subsubheading @value{GDBN} Command
31641 There is no corresponding @value{GDBN} command.
31643 @subsubheading Example
31646 -symbol-list-lines basics.c
31647 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
31653 @subheading The @code{-symbol-list-types} Command
31654 @findex -symbol-list-types
31656 @subsubheading Synopsis
31662 List all the type names.
31664 @subsubheading @value{GDBN} Command
31666 The corresponding commands are @samp{info types} in @value{GDBN},
31667 @samp{gdb_search} in @code{gdbtk}.
31669 @subsubheading Example
31673 @subheading The @code{-symbol-list-variables} Command
31674 @findex -symbol-list-variables
31676 @subsubheading Synopsis
31679 -symbol-list-variables
31682 List all the global and static variable names.
31684 @subsubheading @value{GDBN} Command
31686 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
31688 @subsubheading Example
31692 @subheading The @code{-symbol-locate} Command
31693 @findex -symbol-locate
31695 @subsubheading Synopsis
31701 @subsubheading @value{GDBN} Command
31703 @samp{gdb_loc} in @code{gdbtk}.
31705 @subsubheading Example
31709 @subheading The @code{-symbol-type} Command
31710 @findex -symbol-type
31712 @subsubheading Synopsis
31715 -symbol-type @var{variable}
31718 Show type of @var{variable}.
31720 @subsubheading @value{GDBN} Command
31722 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
31723 @samp{gdb_obj_variable}.
31725 @subsubheading Example
31730 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31731 @node GDB/MI File Commands
31732 @section @sc{gdb/mi} File Commands
31734 This section describes the GDB/MI commands to specify executable file names
31735 and to read in and obtain symbol table information.
31737 @subheading The @code{-file-exec-and-symbols} Command
31738 @findex -file-exec-and-symbols
31740 @subsubheading Synopsis
31743 -file-exec-and-symbols @var{file}
31746 Specify the executable file to be debugged. This file is the one from
31747 which the symbol table is also read. If no file is specified, the
31748 command clears the executable and symbol information. If breakpoints
31749 are set when using this command with no arguments, @value{GDBN} will produce
31750 error messages. Otherwise, no output is produced, except a completion
31753 @subsubheading @value{GDBN} Command
31755 The corresponding @value{GDBN} command is @samp{file}.
31757 @subsubheading Example
31761 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31767 @subheading The @code{-file-exec-file} Command
31768 @findex -file-exec-file
31770 @subsubheading Synopsis
31773 -file-exec-file @var{file}
31776 Specify the executable file to be debugged. Unlike
31777 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
31778 from this file. If used without argument, @value{GDBN} clears the information
31779 about the executable file. No output is produced, except a completion
31782 @subsubheading @value{GDBN} Command
31784 The corresponding @value{GDBN} command is @samp{exec-file}.
31786 @subsubheading Example
31790 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31797 @subheading The @code{-file-list-exec-sections} Command
31798 @findex -file-list-exec-sections
31800 @subsubheading Synopsis
31803 -file-list-exec-sections
31806 List the sections of the current executable file.
31808 @subsubheading @value{GDBN} Command
31810 The @value{GDBN} command @samp{info file} shows, among the rest, the same
31811 information as this command. @code{gdbtk} has a corresponding command
31812 @samp{gdb_load_info}.
31814 @subsubheading Example
31819 @subheading The @code{-file-list-exec-source-file} Command
31820 @findex -file-list-exec-source-file
31822 @subsubheading Synopsis
31825 -file-list-exec-source-file
31828 List the line number, the current source file, and the absolute path
31829 to the current source file for the current executable. The macro
31830 information field has a value of @samp{1} or @samp{0} depending on
31831 whether or not the file includes preprocessor macro information.
31833 @subsubheading @value{GDBN} Command
31835 The @value{GDBN} equivalent is @samp{info source}
31837 @subsubheading Example
31841 123-file-list-exec-source-file
31842 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
31847 @subheading The @code{-file-list-exec-source-files} Command
31848 @findex -file-list-exec-source-files
31850 @subsubheading Synopsis
31853 -file-list-exec-source-files
31856 List the source files for the current executable.
31858 It will always output the filename, but only when @value{GDBN} can find
31859 the absolute file name of a source file, will it output the fullname.
31861 @subsubheading @value{GDBN} Command
31863 The @value{GDBN} equivalent is @samp{info sources}.
31864 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
31866 @subsubheading Example
31869 -file-list-exec-source-files
31871 @{file=foo.c,fullname=/home/foo.c@},
31872 @{file=/home/bar.c,fullname=/home/bar.c@},
31873 @{file=gdb_could_not_find_fullpath.c@}]
31878 @subheading The @code{-file-list-shared-libraries} Command
31879 @findex -file-list-shared-libraries
31881 @subsubheading Synopsis
31884 -file-list-shared-libraries
31887 List the shared libraries in the program.
31889 @subsubheading @value{GDBN} Command
31891 The corresponding @value{GDBN} command is @samp{info shared}.
31893 @subsubheading Example
31897 @subheading The @code{-file-list-symbol-files} Command
31898 @findex -file-list-symbol-files
31900 @subsubheading Synopsis
31903 -file-list-symbol-files
31908 @subsubheading @value{GDBN} Command
31910 The corresponding @value{GDBN} command is @samp{info file} (part of it).
31912 @subsubheading Example
31917 @subheading The @code{-file-symbol-file} Command
31918 @findex -file-symbol-file
31920 @subsubheading Synopsis
31923 -file-symbol-file @var{file}
31926 Read symbol table info from the specified @var{file} argument. When
31927 used without arguments, clears @value{GDBN}'s symbol table info. No output is
31928 produced, except for a completion notification.
31930 @subsubheading @value{GDBN} Command
31932 The corresponding @value{GDBN} command is @samp{symbol-file}.
31934 @subsubheading Example
31938 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31944 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31945 @node GDB/MI Memory Overlay Commands
31946 @section @sc{gdb/mi} Memory Overlay Commands
31948 The memory overlay commands are not implemented.
31950 @c @subheading -overlay-auto
31952 @c @subheading -overlay-list-mapping-state
31954 @c @subheading -overlay-list-overlays
31956 @c @subheading -overlay-map
31958 @c @subheading -overlay-off
31960 @c @subheading -overlay-on
31962 @c @subheading -overlay-unmap
31964 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31965 @node GDB/MI Signal Handling Commands
31966 @section @sc{gdb/mi} Signal Handling Commands
31968 Signal handling commands are not implemented.
31970 @c @subheading -signal-handle
31972 @c @subheading -signal-list-handle-actions
31974 @c @subheading -signal-list-signal-types
31978 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31979 @node GDB/MI Target Manipulation
31980 @section @sc{gdb/mi} Target Manipulation Commands
31983 @subheading The @code{-target-attach} Command
31984 @findex -target-attach
31986 @subsubheading Synopsis
31989 -target-attach @var{pid} | @var{gid} | @var{file}
31992 Attach to a process @var{pid} or a file @var{file} outside of
31993 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
31994 group, the id previously returned by
31995 @samp{-list-thread-groups --available} must be used.
31997 @subsubheading @value{GDBN} Command
31999 The corresponding @value{GDBN} command is @samp{attach}.
32001 @subsubheading Example
32005 =thread-created,id="1"
32006 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
32012 @subheading The @code{-target-compare-sections} Command
32013 @findex -target-compare-sections
32015 @subsubheading Synopsis
32018 -target-compare-sections [ @var{section} ]
32021 Compare data of section @var{section} on target to the exec file.
32022 Without the argument, all sections are compared.
32024 @subsubheading @value{GDBN} Command
32026 The @value{GDBN} equivalent is @samp{compare-sections}.
32028 @subsubheading Example
32033 @subheading The @code{-target-detach} Command
32034 @findex -target-detach
32036 @subsubheading Synopsis
32039 -target-detach [ @var{pid} | @var{gid} ]
32042 Detach from the remote target which normally resumes its execution.
32043 If either @var{pid} or @var{gid} is specified, detaches from either
32044 the specified process, or specified thread group. There's no output.
32046 @subsubheading @value{GDBN} Command
32048 The corresponding @value{GDBN} command is @samp{detach}.
32050 @subsubheading Example
32060 @subheading The @code{-target-disconnect} Command
32061 @findex -target-disconnect
32063 @subsubheading Synopsis
32069 Disconnect from the remote target. There's no output and the target is
32070 generally not resumed.
32072 @subsubheading @value{GDBN} Command
32074 The corresponding @value{GDBN} command is @samp{disconnect}.
32076 @subsubheading Example
32086 @subheading The @code{-target-download} Command
32087 @findex -target-download
32089 @subsubheading Synopsis
32095 Loads the executable onto the remote target.
32096 It prints out an update message every half second, which includes the fields:
32100 The name of the section.
32102 The size of what has been sent so far for that section.
32104 The size of the section.
32106 The total size of what was sent so far (the current and the previous sections).
32108 The size of the overall executable to download.
32112 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
32113 @sc{gdb/mi} Output Syntax}).
32115 In addition, it prints the name and size of the sections, as they are
32116 downloaded. These messages include the following fields:
32120 The name of the section.
32122 The size of the section.
32124 The size of the overall executable to download.
32128 At the end, a summary is printed.
32130 @subsubheading @value{GDBN} Command
32132 The corresponding @value{GDBN} command is @samp{load}.
32134 @subsubheading Example
32136 Note: each status message appears on a single line. Here the messages
32137 have been broken down so that they can fit onto a page.
32142 +download,@{section=".text",section-size="6668",total-size="9880"@}
32143 +download,@{section=".text",section-sent="512",section-size="6668",
32144 total-sent="512",total-size="9880"@}
32145 +download,@{section=".text",section-sent="1024",section-size="6668",
32146 total-sent="1024",total-size="9880"@}
32147 +download,@{section=".text",section-sent="1536",section-size="6668",
32148 total-sent="1536",total-size="9880"@}
32149 +download,@{section=".text",section-sent="2048",section-size="6668",
32150 total-sent="2048",total-size="9880"@}
32151 +download,@{section=".text",section-sent="2560",section-size="6668",
32152 total-sent="2560",total-size="9880"@}
32153 +download,@{section=".text",section-sent="3072",section-size="6668",
32154 total-sent="3072",total-size="9880"@}
32155 +download,@{section=".text",section-sent="3584",section-size="6668",
32156 total-sent="3584",total-size="9880"@}
32157 +download,@{section=".text",section-sent="4096",section-size="6668",
32158 total-sent="4096",total-size="9880"@}
32159 +download,@{section=".text",section-sent="4608",section-size="6668",
32160 total-sent="4608",total-size="9880"@}
32161 +download,@{section=".text",section-sent="5120",section-size="6668",
32162 total-sent="5120",total-size="9880"@}
32163 +download,@{section=".text",section-sent="5632",section-size="6668",
32164 total-sent="5632",total-size="9880"@}
32165 +download,@{section=".text",section-sent="6144",section-size="6668",
32166 total-sent="6144",total-size="9880"@}
32167 +download,@{section=".text",section-sent="6656",section-size="6668",
32168 total-sent="6656",total-size="9880"@}
32169 +download,@{section=".init",section-size="28",total-size="9880"@}
32170 +download,@{section=".fini",section-size="28",total-size="9880"@}
32171 +download,@{section=".data",section-size="3156",total-size="9880"@}
32172 +download,@{section=".data",section-sent="512",section-size="3156",
32173 total-sent="7236",total-size="9880"@}
32174 +download,@{section=".data",section-sent="1024",section-size="3156",
32175 total-sent="7748",total-size="9880"@}
32176 +download,@{section=".data",section-sent="1536",section-size="3156",
32177 total-sent="8260",total-size="9880"@}
32178 +download,@{section=".data",section-sent="2048",section-size="3156",
32179 total-sent="8772",total-size="9880"@}
32180 +download,@{section=".data",section-sent="2560",section-size="3156",
32181 total-sent="9284",total-size="9880"@}
32182 +download,@{section=".data",section-sent="3072",section-size="3156",
32183 total-sent="9796",total-size="9880"@}
32184 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
32191 @subheading The @code{-target-exec-status} Command
32192 @findex -target-exec-status
32194 @subsubheading Synopsis
32197 -target-exec-status
32200 Provide information on the state of the target (whether it is running or
32201 not, for instance).
32203 @subsubheading @value{GDBN} Command
32205 There's no equivalent @value{GDBN} command.
32207 @subsubheading Example
32211 @subheading The @code{-target-list-available-targets} Command
32212 @findex -target-list-available-targets
32214 @subsubheading Synopsis
32217 -target-list-available-targets
32220 List the possible targets to connect to.
32222 @subsubheading @value{GDBN} Command
32224 The corresponding @value{GDBN} command is @samp{help target}.
32226 @subsubheading Example
32230 @subheading The @code{-target-list-current-targets} Command
32231 @findex -target-list-current-targets
32233 @subsubheading Synopsis
32236 -target-list-current-targets
32239 Describe the current target.
32241 @subsubheading @value{GDBN} Command
32243 The corresponding information is printed by @samp{info file} (among
32246 @subsubheading Example
32250 @subheading The @code{-target-list-parameters} Command
32251 @findex -target-list-parameters
32253 @subsubheading Synopsis
32256 -target-list-parameters
32262 @subsubheading @value{GDBN} Command
32266 @subsubheading Example
32270 @subheading The @code{-target-select} Command
32271 @findex -target-select
32273 @subsubheading Synopsis
32276 -target-select @var{type} @var{parameters @dots{}}
32279 Connect @value{GDBN} to the remote target. This command takes two args:
32283 The type of target, for instance @samp{remote}, etc.
32284 @item @var{parameters}
32285 Device names, host names and the like. @xref{Target Commands, ,
32286 Commands for Managing Targets}, for more details.
32289 The output is a connection notification, followed by the address at
32290 which the target program is, in the following form:
32293 ^connected,addr="@var{address}",func="@var{function name}",
32294 args=[@var{arg list}]
32297 @subsubheading @value{GDBN} Command
32299 The corresponding @value{GDBN} command is @samp{target}.
32301 @subsubheading Example
32305 -target-select remote /dev/ttya
32306 ^connected,addr="0xfe00a300",func="??",args=[]
32310 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32311 @node GDB/MI File Transfer Commands
32312 @section @sc{gdb/mi} File Transfer Commands
32315 @subheading The @code{-target-file-put} Command
32316 @findex -target-file-put
32318 @subsubheading Synopsis
32321 -target-file-put @var{hostfile} @var{targetfile}
32324 Copy file @var{hostfile} from the host system (the machine running
32325 @value{GDBN}) to @var{targetfile} on the target system.
32327 @subsubheading @value{GDBN} Command
32329 The corresponding @value{GDBN} command is @samp{remote put}.
32331 @subsubheading Example
32335 -target-file-put localfile remotefile
32341 @subheading The @code{-target-file-get} Command
32342 @findex -target-file-get
32344 @subsubheading Synopsis
32347 -target-file-get @var{targetfile} @var{hostfile}
32350 Copy file @var{targetfile} from the target system to @var{hostfile}
32351 on the host system.
32353 @subsubheading @value{GDBN} Command
32355 The corresponding @value{GDBN} command is @samp{remote get}.
32357 @subsubheading Example
32361 -target-file-get remotefile localfile
32367 @subheading The @code{-target-file-delete} Command
32368 @findex -target-file-delete
32370 @subsubheading Synopsis
32373 -target-file-delete @var{targetfile}
32376 Delete @var{targetfile} from the target system.
32378 @subsubheading @value{GDBN} Command
32380 The corresponding @value{GDBN} command is @samp{remote delete}.
32382 @subsubheading Example
32386 -target-file-delete remotefile
32392 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32393 @node GDB/MI Miscellaneous Commands
32394 @section Miscellaneous @sc{gdb/mi} Commands
32396 @c @subheading -gdb-complete
32398 @subheading The @code{-gdb-exit} Command
32401 @subsubheading Synopsis
32407 Exit @value{GDBN} immediately.
32409 @subsubheading @value{GDBN} Command
32411 Approximately corresponds to @samp{quit}.
32413 @subsubheading Example
32423 @subheading The @code{-exec-abort} Command
32424 @findex -exec-abort
32426 @subsubheading Synopsis
32432 Kill the inferior running program.
32434 @subsubheading @value{GDBN} Command
32436 The corresponding @value{GDBN} command is @samp{kill}.
32438 @subsubheading Example
32443 @subheading The @code{-gdb-set} Command
32446 @subsubheading Synopsis
32452 Set an internal @value{GDBN} variable.
32453 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
32455 @subsubheading @value{GDBN} Command
32457 The corresponding @value{GDBN} command is @samp{set}.
32459 @subsubheading Example
32469 @subheading The @code{-gdb-show} Command
32472 @subsubheading Synopsis
32478 Show the current value of a @value{GDBN} variable.
32480 @subsubheading @value{GDBN} Command
32482 The corresponding @value{GDBN} command is @samp{show}.
32484 @subsubheading Example
32493 @c @subheading -gdb-source
32496 @subheading The @code{-gdb-version} Command
32497 @findex -gdb-version
32499 @subsubheading Synopsis
32505 Show version information for @value{GDBN}. Used mostly in testing.
32507 @subsubheading @value{GDBN} Command
32509 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
32510 default shows this information when you start an interactive session.
32512 @subsubheading Example
32514 @c This example modifies the actual output from GDB to avoid overfull
32520 ~Copyright 2000 Free Software Foundation, Inc.
32521 ~GDB is free software, covered by the GNU General Public License, and
32522 ~you are welcome to change it and/or distribute copies of it under
32523 ~ certain conditions.
32524 ~Type "show copying" to see the conditions.
32525 ~There is absolutely no warranty for GDB. Type "show warranty" for
32527 ~This GDB was configured as
32528 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
32533 @subheading The @code{-list-features} Command
32534 @findex -list-features
32536 Returns a list of particular features of the MI protocol that
32537 this version of gdb implements. A feature can be a command,
32538 or a new field in an output of some command, or even an
32539 important bugfix. While a frontend can sometimes detect presence
32540 of a feature at runtime, it is easier to perform detection at debugger
32543 The command returns a list of strings, with each string naming an
32544 available feature. Each returned string is just a name, it does not
32545 have any internal structure. The list of possible feature names
32551 (gdb) -list-features
32552 ^done,result=["feature1","feature2"]
32555 The current list of features is:
32558 @item frozen-varobjs
32559 Indicates support for the @code{-var-set-frozen} command, as well
32560 as possible presense of the @code{frozen} field in the output
32561 of @code{-varobj-create}.
32562 @item pending-breakpoints
32563 Indicates support for the @option{-f} option to the @code{-break-insert}
32566 Indicates Python scripting support, Python-based
32567 pretty-printing commands, and possible presence of the
32568 @samp{display_hint} field in the output of @code{-var-list-children}
32570 Indicates support for the @code{-thread-info} command.
32571 @item data-read-memory-bytes
32572 Indicates support for the @code{-data-read-memory-bytes} and the
32573 @code{-data-write-memory-bytes} commands.
32574 @item breakpoint-notifications
32575 Indicates that changes to breakpoints and breakpoints created via the
32576 CLI will be announced via async records.
32577 @item ada-task-info
32578 Indicates support for the @code{-ada-task-info} command.
32581 @subheading The @code{-list-target-features} Command
32582 @findex -list-target-features
32584 Returns a list of particular features that are supported by the
32585 target. Those features affect the permitted MI commands, but
32586 unlike the features reported by the @code{-list-features} command, the
32587 features depend on which target GDB is using at the moment. Whenever
32588 a target can change, due to commands such as @code{-target-select},
32589 @code{-target-attach} or @code{-exec-run}, the list of target features
32590 may change, and the frontend should obtain it again.
32594 (gdb) -list-features
32595 ^done,result=["async"]
32598 The current list of features is:
32602 Indicates that the target is capable of asynchronous command
32603 execution, which means that @value{GDBN} will accept further commands
32604 while the target is running.
32607 Indicates that the target is capable of reverse execution.
32608 @xref{Reverse Execution}, for more information.
32612 @subheading The @code{-list-thread-groups} Command
32613 @findex -list-thread-groups
32615 @subheading Synopsis
32618 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
32621 Lists thread groups (@pxref{Thread groups}). When a single thread
32622 group is passed as the argument, lists the children of that group.
32623 When several thread group are passed, lists information about those
32624 thread groups. Without any parameters, lists information about all
32625 top-level thread groups.
32627 Normally, thread groups that are being debugged are reported.
32628 With the @samp{--available} option, @value{GDBN} reports thread groups
32629 available on the target.
32631 The output of this command may have either a @samp{threads} result or
32632 a @samp{groups} result. The @samp{thread} result has a list of tuples
32633 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
32634 Information}). The @samp{groups} result has a list of tuples as value,
32635 each tuple describing a thread group. If top-level groups are
32636 requested (that is, no parameter is passed), or when several groups
32637 are passed, the output always has a @samp{groups} result. The format
32638 of the @samp{group} result is described below.
32640 To reduce the number of roundtrips it's possible to list thread groups
32641 together with their children, by passing the @samp{--recurse} option
32642 and the recursion depth. Presently, only recursion depth of 1 is
32643 permitted. If this option is present, then every reported thread group
32644 will also include its children, either as @samp{group} or
32645 @samp{threads} field.
32647 In general, any combination of option and parameters is permitted, with
32648 the following caveats:
32652 When a single thread group is passed, the output will typically
32653 be the @samp{threads} result. Because threads may not contain
32654 anything, the @samp{recurse} option will be ignored.
32657 When the @samp{--available} option is passed, limited information may
32658 be available. In particular, the list of threads of a process might
32659 be inaccessible. Further, specifying specific thread groups might
32660 not give any performance advantage over listing all thread groups.
32661 The frontend should assume that @samp{-list-thread-groups --available}
32662 is always an expensive operation and cache the results.
32666 The @samp{groups} result is a list of tuples, where each tuple may
32667 have the following fields:
32671 Identifier of the thread group. This field is always present.
32672 The identifier is an opaque string; frontends should not try to
32673 convert it to an integer, even though it might look like one.
32676 The type of the thread group. At present, only @samp{process} is a
32680 The target-specific process identifier. This field is only present
32681 for thread groups of type @samp{process} and only if the process exists.
32684 The number of children this thread group has. This field may be
32685 absent for an available thread group.
32688 This field has a list of tuples as value, each tuple describing a
32689 thread. It may be present if the @samp{--recurse} option is
32690 specified, and it's actually possible to obtain the threads.
32693 This field is a list of integers, each identifying a core that one
32694 thread of the group is running on. This field may be absent if
32695 such information is not available.
32698 The name of the executable file that corresponds to this thread group.
32699 The field is only present for thread groups of type @samp{process},
32700 and only if there is a corresponding executable file.
32704 @subheading Example
32708 -list-thread-groups
32709 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
32710 -list-thread-groups 17
32711 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
32712 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
32713 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
32714 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
32715 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
32716 -list-thread-groups --available
32717 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
32718 -list-thread-groups --available --recurse 1
32719 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
32720 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
32721 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
32722 -list-thread-groups --available --recurse 1 17 18
32723 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
32724 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
32725 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
32728 @subheading The @code{-info-os} Command
32731 @subsubheading Synopsis
32734 -info-os [ @var{type} ]
32737 If no argument is supplied, the command returns a table of available
32738 operating-system-specific information types. If one of these types is
32739 supplied as an argument @var{type}, then the command returns a table
32740 of data of that type.
32742 The types of information available depend on the target operating
32745 @subsubheading @value{GDBN} Command
32747 The corresponding @value{GDBN} command is @samp{info os}.
32749 @subsubheading Example
32751 When run on a @sc{gnu}/Linux system, the output will look something
32757 ^done,OSDataTable=@{nr_rows="9",nr_cols="3",
32758 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
32759 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
32760 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
32761 body=[item=@{col0="processes",col1="Listing of all processes",
32762 col2="Processes"@},
32763 item=@{col0="procgroups",col1="Listing of all process groups",
32764 col2="Process groups"@},
32765 item=@{col0="threads",col1="Listing of all threads",
32767 item=@{col0="files",col1="Listing of all file descriptors",
32768 col2="File descriptors"@},
32769 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
32771 item=@{col0="shm",col1="Listing of all shared-memory regions",
32772 col2="Shared-memory regions"@},
32773 item=@{col0="semaphores",col1="Listing of all semaphores",
32774 col2="Semaphores"@},
32775 item=@{col0="msg",col1="Listing of all message queues",
32776 col2="Message queues"@},
32777 item=@{col0="modules",col1="Listing of all loaded kernel modules",
32778 col2="Kernel modules"@}]@}
32781 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
32782 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
32783 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
32784 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
32785 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
32786 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
32787 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
32788 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
32790 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
32791 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
32795 (Note that the MI output here includes a @code{"Title"} column that
32796 does not appear in command-line @code{info os}; this column is useful
32797 for MI clients that want to enumerate the types of data, such as in a
32798 popup menu, but is needless clutter on the command line, and
32799 @code{info os} omits it.)
32801 @subheading The @code{-add-inferior} Command
32802 @findex -add-inferior
32804 @subheading Synopsis
32810 Creates a new inferior (@pxref{Inferiors and Programs}). The created
32811 inferior is not associated with any executable. Such association may
32812 be established with the @samp{-file-exec-and-symbols} command
32813 (@pxref{GDB/MI File Commands}). The command response has a single
32814 field, @samp{thread-group}, whose value is the identifier of the
32815 thread group corresponding to the new inferior.
32817 @subheading Example
32822 ^done,thread-group="i3"
32825 @subheading The @code{-interpreter-exec} Command
32826 @findex -interpreter-exec
32828 @subheading Synopsis
32831 -interpreter-exec @var{interpreter} @var{command}
32833 @anchor{-interpreter-exec}
32835 Execute the specified @var{command} in the given @var{interpreter}.
32837 @subheading @value{GDBN} Command
32839 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
32841 @subheading Example
32845 -interpreter-exec console "break main"
32846 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
32847 &"During symbol reading, bad structure-type format.\n"
32848 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
32853 @subheading The @code{-inferior-tty-set} Command
32854 @findex -inferior-tty-set
32856 @subheading Synopsis
32859 -inferior-tty-set /dev/pts/1
32862 Set terminal for future runs of the program being debugged.
32864 @subheading @value{GDBN} Command
32866 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
32868 @subheading Example
32872 -inferior-tty-set /dev/pts/1
32877 @subheading The @code{-inferior-tty-show} Command
32878 @findex -inferior-tty-show
32880 @subheading Synopsis
32886 Show terminal for future runs of program being debugged.
32888 @subheading @value{GDBN} Command
32890 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
32892 @subheading Example
32896 -inferior-tty-set /dev/pts/1
32900 ^done,inferior_tty_terminal="/dev/pts/1"
32904 @subheading The @code{-enable-timings} Command
32905 @findex -enable-timings
32907 @subheading Synopsis
32910 -enable-timings [yes | no]
32913 Toggle the printing of the wallclock, user and system times for an MI
32914 command as a field in its output. This command is to help frontend
32915 developers optimize the performance of their code. No argument is
32916 equivalent to @samp{yes}.
32918 @subheading @value{GDBN} Command
32922 @subheading Example
32930 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
32931 addr="0x080484ed",func="main",file="myprog.c",
32932 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
32933 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
32941 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
32942 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
32943 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
32944 fullname="/home/nickrob/myprog.c",line="73"@}
32949 @chapter @value{GDBN} Annotations
32951 This chapter describes annotations in @value{GDBN}. Annotations were
32952 designed to interface @value{GDBN} to graphical user interfaces or other
32953 similar programs which want to interact with @value{GDBN} at a
32954 relatively high level.
32956 The annotation mechanism has largely been superseded by @sc{gdb/mi}
32960 This is Edition @value{EDITION}, @value{DATE}.
32964 * Annotations Overview:: What annotations are; the general syntax.
32965 * Server Prefix:: Issuing a command without affecting user state.
32966 * Prompting:: Annotations marking @value{GDBN}'s need for input.
32967 * Errors:: Annotations for error messages.
32968 * Invalidation:: Some annotations describe things now invalid.
32969 * Annotations for Running::
32970 Whether the program is running, how it stopped, etc.
32971 * Source Annotations:: Annotations describing source code.
32974 @node Annotations Overview
32975 @section What is an Annotation?
32976 @cindex annotations
32978 Annotations start with a newline character, two @samp{control-z}
32979 characters, and the name of the annotation. If there is no additional
32980 information associated with this annotation, the name of the annotation
32981 is followed immediately by a newline. If there is additional
32982 information, the name of the annotation is followed by a space, the
32983 additional information, and a newline. The additional information
32984 cannot contain newline characters.
32986 Any output not beginning with a newline and two @samp{control-z}
32987 characters denotes literal output from @value{GDBN}. Currently there is
32988 no need for @value{GDBN} to output a newline followed by two
32989 @samp{control-z} characters, but if there was such a need, the
32990 annotations could be extended with an @samp{escape} annotation which
32991 means those three characters as output.
32993 The annotation @var{level}, which is specified using the
32994 @option{--annotate} command line option (@pxref{Mode Options}), controls
32995 how much information @value{GDBN} prints together with its prompt,
32996 values of expressions, source lines, and other types of output. Level 0
32997 is for no annotations, level 1 is for use when @value{GDBN} is run as a
32998 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
32999 for programs that control @value{GDBN}, and level 2 annotations have
33000 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
33001 Interface, annotate, GDB's Obsolete Annotations}).
33004 @kindex set annotate
33005 @item set annotate @var{level}
33006 The @value{GDBN} command @code{set annotate} sets the level of
33007 annotations to the specified @var{level}.
33009 @item show annotate
33010 @kindex show annotate
33011 Show the current annotation level.
33014 This chapter describes level 3 annotations.
33016 A simple example of starting up @value{GDBN} with annotations is:
33019 $ @kbd{gdb --annotate=3}
33021 Copyright 2003 Free Software Foundation, Inc.
33022 GDB is free software, covered by the GNU General Public License,
33023 and you are welcome to change it and/or distribute copies of it
33024 under certain conditions.
33025 Type "show copying" to see the conditions.
33026 There is absolutely no warranty for GDB. Type "show warranty"
33028 This GDB was configured as "i386-pc-linux-gnu"
33039 Here @samp{quit} is input to @value{GDBN}; the rest is output from
33040 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
33041 denotes a @samp{control-z} character) are annotations; the rest is
33042 output from @value{GDBN}.
33044 @node Server Prefix
33045 @section The Server Prefix
33046 @cindex server prefix
33048 If you prefix a command with @samp{server } then it will not affect
33049 the command history, nor will it affect @value{GDBN}'s notion of which
33050 command to repeat if @key{RET} is pressed on a line by itself. This
33051 means that commands can be run behind a user's back by a front-end in
33052 a transparent manner.
33054 The @code{server } prefix does not affect the recording of values into
33055 the value history; to print a value without recording it into the
33056 value history, use the @code{output} command instead of the
33057 @code{print} command.
33059 Using this prefix also disables confirmation requests
33060 (@pxref{confirmation requests}).
33063 @section Annotation for @value{GDBN} Input
33065 @cindex annotations for prompts
33066 When @value{GDBN} prompts for input, it annotates this fact so it is possible
33067 to know when to send output, when the output from a given command is
33070 Different kinds of input each have a different @dfn{input type}. Each
33071 input type has three annotations: a @code{pre-} annotation, which
33072 denotes the beginning of any prompt which is being output, a plain
33073 annotation, which denotes the end of the prompt, and then a @code{post-}
33074 annotation which denotes the end of any echo which may (or may not) be
33075 associated with the input. For example, the @code{prompt} input type
33076 features the following annotations:
33084 The input types are
33087 @findex pre-prompt annotation
33088 @findex prompt annotation
33089 @findex post-prompt annotation
33091 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
33093 @findex pre-commands annotation
33094 @findex commands annotation
33095 @findex post-commands annotation
33097 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
33098 command. The annotations are repeated for each command which is input.
33100 @findex pre-overload-choice annotation
33101 @findex overload-choice annotation
33102 @findex post-overload-choice annotation
33103 @item overload-choice
33104 When @value{GDBN} wants the user to select between various overloaded functions.
33106 @findex pre-query annotation
33107 @findex query annotation
33108 @findex post-query annotation
33110 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
33112 @findex pre-prompt-for-continue annotation
33113 @findex prompt-for-continue annotation
33114 @findex post-prompt-for-continue annotation
33115 @item prompt-for-continue
33116 When @value{GDBN} is asking the user to press return to continue. Note: Don't
33117 expect this to work well; instead use @code{set height 0} to disable
33118 prompting. This is because the counting of lines is buggy in the
33119 presence of annotations.
33124 @cindex annotations for errors, warnings and interrupts
33126 @findex quit annotation
33131 This annotation occurs right before @value{GDBN} responds to an interrupt.
33133 @findex error annotation
33138 This annotation occurs right before @value{GDBN} responds to an error.
33140 Quit and error annotations indicate that any annotations which @value{GDBN} was
33141 in the middle of may end abruptly. For example, if a
33142 @code{value-history-begin} annotation is followed by a @code{error}, one
33143 cannot expect to receive the matching @code{value-history-end}. One
33144 cannot expect not to receive it either, however; an error annotation
33145 does not necessarily mean that @value{GDBN} is immediately returning all the way
33148 @findex error-begin annotation
33149 A quit or error annotation may be preceded by
33155 Any output between that and the quit or error annotation is the error
33158 Warning messages are not yet annotated.
33159 @c If we want to change that, need to fix warning(), type_error(),
33160 @c range_error(), and possibly other places.
33163 @section Invalidation Notices
33165 @cindex annotations for invalidation messages
33166 The following annotations say that certain pieces of state may have
33170 @findex frames-invalid annotation
33171 @item ^Z^Zframes-invalid
33173 The frames (for example, output from the @code{backtrace} command) may
33176 @findex breakpoints-invalid annotation
33177 @item ^Z^Zbreakpoints-invalid
33179 The breakpoints may have changed. For example, the user just added or
33180 deleted a breakpoint.
33183 @node Annotations for Running
33184 @section Running the Program
33185 @cindex annotations for running programs
33187 @findex starting annotation
33188 @findex stopping annotation
33189 When the program starts executing due to a @value{GDBN} command such as
33190 @code{step} or @code{continue},
33196 is output. When the program stops,
33202 is output. Before the @code{stopped} annotation, a variety of
33203 annotations describe how the program stopped.
33206 @findex exited annotation
33207 @item ^Z^Zexited @var{exit-status}
33208 The program exited, and @var{exit-status} is the exit status (zero for
33209 successful exit, otherwise nonzero).
33211 @findex signalled annotation
33212 @findex signal-name annotation
33213 @findex signal-name-end annotation
33214 @findex signal-string annotation
33215 @findex signal-string-end annotation
33216 @item ^Z^Zsignalled
33217 The program exited with a signal. After the @code{^Z^Zsignalled}, the
33218 annotation continues:
33224 ^Z^Zsignal-name-end
33228 ^Z^Zsignal-string-end
33233 where @var{name} is the name of the signal, such as @code{SIGILL} or
33234 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
33235 as @code{Illegal Instruction} or @code{Segmentation fault}.
33236 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
33237 user's benefit and have no particular format.
33239 @findex signal annotation
33241 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
33242 just saying that the program received the signal, not that it was
33243 terminated with it.
33245 @findex breakpoint annotation
33246 @item ^Z^Zbreakpoint @var{number}
33247 The program hit breakpoint number @var{number}.
33249 @findex watchpoint annotation
33250 @item ^Z^Zwatchpoint @var{number}
33251 The program hit watchpoint number @var{number}.
33254 @node Source Annotations
33255 @section Displaying Source
33256 @cindex annotations for source display
33258 @findex source annotation
33259 The following annotation is used instead of displaying source code:
33262 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
33265 where @var{filename} is an absolute file name indicating which source
33266 file, @var{line} is the line number within that file (where 1 is the
33267 first line in the file), @var{character} is the character position
33268 within the file (where 0 is the first character in the file) (for most
33269 debug formats this will necessarily point to the beginning of a line),
33270 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
33271 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
33272 @var{addr} is the address in the target program associated with the
33273 source which is being displayed. @var{addr} is in the form @samp{0x}
33274 followed by one or more lowercase hex digits (note that this does not
33275 depend on the language).
33277 @node JIT Interface
33278 @chapter JIT Compilation Interface
33279 @cindex just-in-time compilation
33280 @cindex JIT compilation interface
33282 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
33283 interface. A JIT compiler is a program or library that generates native
33284 executable code at runtime and executes it, usually in order to achieve good
33285 performance while maintaining platform independence.
33287 Programs that use JIT compilation are normally difficult to debug because
33288 portions of their code are generated at runtime, instead of being loaded from
33289 object files, which is where @value{GDBN} normally finds the program's symbols
33290 and debug information. In order to debug programs that use JIT compilation,
33291 @value{GDBN} has an interface that allows the program to register in-memory
33292 symbol files with @value{GDBN} at runtime.
33294 If you are using @value{GDBN} to debug a program that uses this interface, then
33295 it should work transparently so long as you have not stripped the binary. If
33296 you are developing a JIT compiler, then the interface is documented in the rest
33297 of this chapter. At this time, the only known client of this interface is the
33300 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
33301 JIT compiler communicates with @value{GDBN} by writing data into a global
33302 variable and calling a fuction at a well-known symbol. When @value{GDBN}
33303 attaches, it reads a linked list of symbol files from the global variable to
33304 find existing code, and puts a breakpoint in the function so that it can find
33305 out about additional code.
33308 * Declarations:: Relevant C struct declarations
33309 * Registering Code:: Steps to register code
33310 * Unregistering Code:: Steps to unregister code
33311 * Custom Debug Info:: Emit debug information in a custom format
33315 @section JIT Declarations
33317 These are the relevant struct declarations that a C program should include to
33318 implement the interface:
33328 struct jit_code_entry
33330 struct jit_code_entry *next_entry;
33331 struct jit_code_entry *prev_entry;
33332 const char *symfile_addr;
33333 uint64_t symfile_size;
33336 struct jit_descriptor
33339 /* This type should be jit_actions_t, but we use uint32_t
33340 to be explicit about the bitwidth. */
33341 uint32_t action_flag;
33342 struct jit_code_entry *relevant_entry;
33343 struct jit_code_entry *first_entry;
33346 /* GDB puts a breakpoint in this function. */
33347 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
33349 /* Make sure to specify the version statically, because the
33350 debugger may check the version before we can set it. */
33351 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
33354 If the JIT is multi-threaded, then it is important that the JIT synchronize any
33355 modifications to this global data properly, which can easily be done by putting
33356 a global mutex around modifications to these structures.
33358 @node Registering Code
33359 @section Registering Code
33361 To register code with @value{GDBN}, the JIT should follow this protocol:
33365 Generate an object file in memory with symbols and other desired debug
33366 information. The file must include the virtual addresses of the sections.
33369 Create a code entry for the file, which gives the start and size of the symbol
33373 Add it to the linked list in the JIT descriptor.
33376 Point the relevant_entry field of the descriptor at the entry.
33379 Set @code{action_flag} to @code{JIT_REGISTER} and call
33380 @code{__jit_debug_register_code}.
33383 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
33384 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
33385 new code. However, the linked list must still be maintained in order to allow
33386 @value{GDBN} to attach to a running process and still find the symbol files.
33388 @node Unregistering Code
33389 @section Unregistering Code
33391 If code is freed, then the JIT should use the following protocol:
33395 Remove the code entry corresponding to the code from the linked list.
33398 Point the @code{relevant_entry} field of the descriptor at the code entry.
33401 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
33402 @code{__jit_debug_register_code}.
33405 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
33406 and the JIT will leak the memory used for the associated symbol files.
33408 @node Custom Debug Info
33409 @section Custom Debug Info
33410 @cindex custom JIT debug info
33411 @cindex JIT debug info reader
33413 Generating debug information in platform-native file formats (like ELF
33414 or COFF) may be an overkill for JIT compilers; especially if all the
33415 debug info is used for is displaying a meaningful backtrace. The
33416 issue can be resolved by having the JIT writers decide on a debug info
33417 format and also provide a reader that parses the debug info generated
33418 by the JIT compiler. This section gives a brief overview on writing
33419 such a parser. More specific details can be found in the source file
33420 @file{gdb/jit-reader.in}, which is also installed as a header at
33421 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
33423 The reader is implemented as a shared object (so this functionality is
33424 not available on platforms which don't allow loading shared objects at
33425 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
33426 @code{jit-reader-unload} are provided, to be used to load and unload
33427 the readers from a preconfigured directory. Once loaded, the shared
33428 object is used the parse the debug information emitted by the JIT
33432 * Using JIT Debug Info Readers:: How to use supplied readers correctly
33433 * Writing JIT Debug Info Readers:: Creating a debug-info reader
33436 @node Using JIT Debug Info Readers
33437 @subsection Using JIT Debug Info Readers
33438 @kindex jit-reader-load
33439 @kindex jit-reader-unload
33441 Readers can be loaded and unloaded using the @code{jit-reader-load}
33442 and @code{jit-reader-unload} commands.
33445 @item jit-reader-load @var{reader-name}
33446 Load the JIT reader named @var{reader-name}. On a UNIX system, this
33447 will usually load @file{@var{libdir}/gdb/@var{reader-name}}, where
33448 @var{libdir} is the system library directory, usually
33449 @file{/usr/local/lib}. Only one reader can be active at a time;
33450 trying to load a second reader when one is already loaded will result
33451 in @value{GDBN} reporting an error. A new JIT reader can be loaded by
33452 first unloading the current one using @code{jit-reader-load} and then
33453 invoking @code{jit-reader-load}.
33455 @item jit-reader-unload
33456 Unload the currently loaded JIT reader.
33460 @node Writing JIT Debug Info Readers
33461 @subsection Writing JIT Debug Info Readers
33462 @cindex writing JIT debug info readers
33464 As mentioned, a reader is essentially a shared object conforming to a
33465 certain ABI. This ABI is described in @file{jit-reader.h}.
33467 @file{jit-reader.h} defines the structures, macros and functions
33468 required to write a reader. It is installed (along with
33469 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
33470 the system include directory.
33472 Readers need to be released under a GPL compatible license. A reader
33473 can be declared as released under such a license by placing the macro
33474 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
33476 The entry point for readers is the symbol @code{gdb_init_reader},
33477 which is expected to be a function with the prototype
33479 @findex gdb_init_reader
33481 extern struct gdb_reader_funcs *gdb_init_reader (void);
33484 @cindex @code{struct gdb_reader_funcs}
33486 @code{struct gdb_reader_funcs} contains a set of pointers to callback
33487 functions. These functions are executed to read the debug info
33488 generated by the JIT compiler (@code{read}), to unwind stack frames
33489 (@code{unwind}) and to create canonical frame IDs
33490 (@code{get_Frame_id}). It also has a callback that is called when the
33491 reader is being unloaded (@code{destroy}). The struct looks like this
33494 struct gdb_reader_funcs
33496 /* Must be set to GDB_READER_INTERFACE_VERSION. */
33497 int reader_version;
33499 /* For use by the reader. */
33502 gdb_read_debug_info *read;
33503 gdb_unwind_frame *unwind;
33504 gdb_get_frame_id *get_frame_id;
33505 gdb_destroy_reader *destroy;
33509 @cindex @code{struct gdb_symbol_callbacks}
33510 @cindex @code{struct gdb_unwind_callbacks}
33512 The callbacks are provided with another set of callbacks by
33513 @value{GDBN} to do their job. For @code{read}, these callbacks are
33514 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
33515 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
33516 @code{struct gdb_symbol_callbacks} has callbacks to create new object
33517 files and new symbol tables inside those object files. @code{struct
33518 gdb_unwind_callbacks} has callbacks to read registers off the current
33519 frame and to write out the values of the registers in the previous
33520 frame. Both have a callback (@code{target_read}) to read bytes off the
33521 target's address space.
33523 @node In-Process Agent
33524 @chapter In-Process Agent
33525 @cindex debugging agent
33526 The traditional debugging model is conceptually low-speed, but works fine,
33527 because most bugs can be reproduced in debugging-mode execution. However,
33528 as multi-core or many-core processors are becoming mainstream, and
33529 multi-threaded programs become more and more popular, there should be more
33530 and more bugs that only manifest themselves at normal-mode execution, for
33531 example, thread races, because debugger's interference with the program's
33532 timing may conceal the bugs. On the other hand, in some applications,
33533 it is not feasible for the debugger to interrupt the program's execution
33534 long enough for the developer to learn anything helpful about its behavior.
33535 If the program's correctness depends on its real-time behavior, delays
33536 introduced by a debugger might cause the program to fail, even when the
33537 code itself is correct. It is useful to be able to observe the program's
33538 behavior without interrupting it.
33540 Therefore, traditional debugging model is too intrusive to reproduce
33541 some bugs. In order to reduce the interference with the program, we can
33542 reduce the number of operations performed by debugger. The
33543 @dfn{In-Process Agent}, a shared library, is running within the same
33544 process with inferior, and is able to perform some debugging operations
33545 itself. As a result, debugger is only involved when necessary, and
33546 performance of debugging can be improved accordingly. Note that
33547 interference with program can be reduced but can't be removed completely,
33548 because the in-process agent will still stop or slow down the program.
33550 The in-process agent can interpret and execute Agent Expressions
33551 (@pxref{Agent Expressions}) during performing debugging operations. The
33552 agent expressions can be used for different purposes, such as collecting
33553 data in tracepoints, and condition evaluation in breakpoints.
33555 @anchor{Control Agent}
33556 You can control whether the in-process agent is used as an aid for
33557 debugging with the following commands:
33560 @kindex set agent on
33562 Causes the in-process agent to perform some operations on behalf of the
33563 debugger. Just which operations requested by the user will be done
33564 by the in-process agent depends on the its capabilities. For example,
33565 if you request to evaluate breakpoint conditions in the in-process agent,
33566 and the in-process agent has such capability as well, then breakpoint
33567 conditions will be evaluated in the in-process agent.
33569 @kindex set agent off
33570 @item set agent off
33571 Disables execution of debugging operations by the in-process agent. All
33572 of the operations will be performed by @value{GDBN}.
33576 Display the current setting of execution of debugging operations by
33577 the in-process agent.
33581 * In-Process Agent Protocol::
33584 @node In-Process Agent Protocol
33585 @section In-Process Agent Protocol
33586 @cindex in-process agent protocol
33588 The in-process agent is able to communicate with both @value{GDBN} and
33589 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
33590 used for communications between @value{GDBN} or GDBserver and the IPA.
33591 In general, @value{GDBN} or GDBserver sends commands
33592 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
33593 in-process agent replies back with the return result of the command, or
33594 some other information. The data sent to in-process agent is composed
33595 of primitive data types, such as 4-byte or 8-byte type, and composite
33596 types, which are called objects (@pxref{IPA Protocol Objects}).
33599 * IPA Protocol Objects::
33600 * IPA Protocol Commands::
33603 @node IPA Protocol Objects
33604 @subsection IPA Protocol Objects
33605 @cindex ipa protocol objects
33607 The commands sent to and results received from agent may contain some
33608 complex data types called @dfn{objects}.
33610 The in-process agent is running on the same machine with @value{GDBN}
33611 or GDBserver, so it doesn't have to handle as much differences between
33612 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
33613 However, there are still some differences of two ends in two processes:
33617 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
33618 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
33620 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
33621 GDBserver is compiled with one, and in-process agent is compiled with
33625 Here are the IPA Protocol Objects:
33629 agent expression object. It represents an agent expression
33630 (@pxref{Agent Expressions}).
33631 @anchor{agent expression object}
33633 tracepoint action object. It represents a tracepoint action
33634 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
33635 memory, static trace data and to evaluate expression.
33636 @anchor{tracepoint action object}
33638 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
33639 @anchor{tracepoint object}
33643 The following table describes important attributes of each IPA protocol
33646 @multitable @columnfractions .30 .20 .50
33647 @headitem Name @tab Size @tab Description
33648 @item @emph{agent expression object} @tab @tab
33649 @item length @tab 4 @tab length of bytes code
33650 @item byte code @tab @var{length} @tab contents of byte code
33651 @item @emph{tracepoint action for collecting memory} @tab @tab
33652 @item 'M' @tab 1 @tab type of tracepoint action
33653 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
33654 address of the lowest byte to collect, otherwise @var{addr} is the offset
33655 of @var{basereg} for memory collecting.
33656 @item len @tab 8 @tab length of memory for collecting
33657 @item basereg @tab 4 @tab the register number containing the starting
33658 memory address for collecting.
33659 @item @emph{tracepoint action for collecting registers} @tab @tab
33660 @item 'R' @tab 1 @tab type of tracepoint action
33661 @item @emph{tracepoint action for collecting static trace data} @tab @tab
33662 @item 'L' @tab 1 @tab type of tracepoint action
33663 @item @emph{tracepoint action for expression evaluation} @tab @tab
33664 @item 'X' @tab 1 @tab type of tracepoint action
33665 @item agent expression @tab length of @tab @ref{agent expression object}
33666 @item @emph{tracepoint object} @tab @tab
33667 @item number @tab 4 @tab number of tracepoint
33668 @item address @tab 8 @tab address of tracepoint inserted on
33669 @item type @tab 4 @tab type of tracepoint
33670 @item enabled @tab 1 @tab enable or disable of tracepoint
33671 @item step_count @tab 8 @tab step
33672 @item pass_count @tab 8 @tab pass
33673 @item numactions @tab 4 @tab number of tracepoint actions
33674 @item hit count @tab 8 @tab hit count
33675 @item trace frame usage @tab 8 @tab trace frame usage
33676 @item compiled_cond @tab 8 @tab compiled condition
33677 @item orig_size @tab 8 @tab orig size
33678 @item condition @tab 4 if condition is NULL otherwise length of
33679 @ref{agent expression object}
33680 @tab zero if condition is NULL, otherwise is
33681 @ref{agent expression object}
33682 @item actions @tab variable
33683 @tab numactions number of @ref{tracepoint action object}
33686 @node IPA Protocol Commands
33687 @subsection IPA Protocol Commands
33688 @cindex ipa protocol commands
33690 The spaces in each command are delimiters to ease reading this commands
33691 specification. They don't exist in real commands.
33695 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
33696 Installs a new fast tracepoint described by @var{tracepoint_object}
33697 (@pxref{tracepoint object}). @var{gdb_jump_pad_head}, 8-byte long, is the
33698 head of @dfn{jumppad}, which is used to jump to data collection routine
33703 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
33704 @var{target_address} is address of tracepoint in the inferior.
33705 @var{gdb_jump_pad_head} is updated head of jumppad. Both of
33706 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
33707 @var{fjump} contains a sequence of instructions jump to jumppad entry.
33708 @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
33715 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
33716 is about to kill inferiors.
33724 @item probe_marker_at:@var{address}
33725 Asks in-process agent to probe the marker at @var{address}.
33732 @item unprobe_marker_at:@var{address}
33733 Asks in-process agent to unprobe the marker at @var{address}.
33737 @chapter Reporting Bugs in @value{GDBN}
33738 @cindex bugs in @value{GDBN}
33739 @cindex reporting bugs in @value{GDBN}
33741 Your bug reports play an essential role in making @value{GDBN} reliable.
33743 Reporting a bug may help you by bringing a solution to your problem, or it
33744 may not. But in any case the principal function of a bug report is to help
33745 the entire community by making the next version of @value{GDBN} work better. Bug
33746 reports are your contribution to the maintenance of @value{GDBN}.
33748 In order for a bug report to serve its purpose, you must include the
33749 information that enables us to fix the bug.
33752 * Bug Criteria:: Have you found a bug?
33753 * Bug Reporting:: How to report bugs
33757 @section Have You Found a Bug?
33758 @cindex bug criteria
33760 If you are not sure whether you have found a bug, here are some guidelines:
33763 @cindex fatal signal
33764 @cindex debugger crash
33765 @cindex crash of debugger
33767 If the debugger gets a fatal signal, for any input whatever, that is a
33768 @value{GDBN} bug. Reliable debuggers never crash.
33770 @cindex error on valid input
33772 If @value{GDBN} produces an error message for valid input, that is a
33773 bug. (Note that if you're cross debugging, the problem may also be
33774 somewhere in the connection to the target.)
33776 @cindex invalid input
33778 If @value{GDBN} does not produce an error message for invalid input,
33779 that is a bug. However, you should note that your idea of
33780 ``invalid input'' might be our idea of ``an extension'' or ``support
33781 for traditional practice''.
33784 If you are an experienced user of debugging tools, your suggestions
33785 for improvement of @value{GDBN} are welcome in any case.
33788 @node Bug Reporting
33789 @section How to Report Bugs
33790 @cindex bug reports
33791 @cindex @value{GDBN} bugs, reporting
33793 A number of companies and individuals offer support for @sc{gnu} products.
33794 If you obtained @value{GDBN} from a support organization, we recommend you
33795 contact that organization first.
33797 You can find contact information for many support companies and
33798 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
33800 @c should add a web page ref...
33803 @ifset BUGURL_DEFAULT
33804 In any event, we also recommend that you submit bug reports for
33805 @value{GDBN}. The preferred method is to submit them directly using
33806 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
33807 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
33810 @strong{Do not send bug reports to @samp{info-gdb}, or to
33811 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
33812 not want to receive bug reports. Those that do have arranged to receive
33815 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
33816 serves as a repeater. The mailing list and the newsgroup carry exactly
33817 the same messages. Often people think of posting bug reports to the
33818 newsgroup instead of mailing them. This appears to work, but it has one
33819 problem which can be crucial: a newsgroup posting often lacks a mail
33820 path back to the sender. Thus, if we need to ask for more information,
33821 we may be unable to reach you. For this reason, it is better to send
33822 bug reports to the mailing list.
33824 @ifclear BUGURL_DEFAULT
33825 In any event, we also recommend that you submit bug reports for
33826 @value{GDBN} to @value{BUGURL}.
33830 The fundamental principle of reporting bugs usefully is this:
33831 @strong{report all the facts}. If you are not sure whether to state a
33832 fact or leave it out, state it!
33834 Often people omit facts because they think they know what causes the
33835 problem and assume that some details do not matter. Thus, you might
33836 assume that the name of the variable you use in an example does not matter.
33837 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
33838 stray memory reference which happens to fetch from the location where that
33839 name is stored in memory; perhaps, if the name were different, the contents
33840 of that location would fool the debugger into doing the right thing despite
33841 the bug. Play it safe and give a specific, complete example. That is the
33842 easiest thing for you to do, and the most helpful.
33844 Keep in mind that the purpose of a bug report is to enable us to fix the
33845 bug. It may be that the bug has been reported previously, but neither
33846 you nor we can know that unless your bug report is complete and
33849 Sometimes people give a few sketchy facts and ask, ``Does this ring a
33850 bell?'' Those bug reports are useless, and we urge everyone to
33851 @emph{refuse to respond to them} except to chide the sender to report
33854 To enable us to fix the bug, you should include all these things:
33858 The version of @value{GDBN}. @value{GDBN} announces it if you start
33859 with no arguments; you can also print it at any time using @code{show
33862 Without this, we will not know whether there is any point in looking for
33863 the bug in the current version of @value{GDBN}.
33866 The type of machine you are using, and the operating system name and
33870 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
33871 ``@value{GCC}--2.8.1''.
33874 What compiler (and its version) was used to compile the program you are
33875 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
33876 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
33877 to get this information; for other compilers, see the documentation for
33881 The command arguments you gave the compiler to compile your example and
33882 observe the bug. For example, did you use @samp{-O}? To guarantee
33883 you will not omit something important, list them all. A copy of the
33884 Makefile (or the output from make) is sufficient.
33886 If we were to try to guess the arguments, we would probably guess wrong
33887 and then we might not encounter the bug.
33890 A complete input script, and all necessary source files, that will
33894 A description of what behavior you observe that you believe is
33895 incorrect. For example, ``It gets a fatal signal.''
33897 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
33898 will certainly notice it. But if the bug is incorrect output, we might
33899 not notice unless it is glaringly wrong. You might as well not give us
33900 a chance to make a mistake.
33902 Even if the problem you experience is a fatal signal, you should still
33903 say so explicitly. Suppose something strange is going on, such as, your
33904 copy of @value{GDBN} is out of synch, or you have encountered a bug in
33905 the C library on your system. (This has happened!) Your copy might
33906 crash and ours would not. If you told us to expect a crash, then when
33907 ours fails to crash, we would know that the bug was not happening for
33908 us. If you had not told us to expect a crash, then we would not be able
33909 to draw any conclusion from our observations.
33912 @cindex recording a session script
33913 To collect all this information, you can use a session recording program
33914 such as @command{script}, which is available on many Unix systems.
33915 Just run your @value{GDBN} session inside @command{script} and then
33916 include the @file{typescript} file with your bug report.
33918 Another way to record a @value{GDBN} session is to run @value{GDBN}
33919 inside Emacs and then save the entire buffer to a file.
33922 If you wish to suggest changes to the @value{GDBN} source, send us context
33923 diffs. If you even discuss something in the @value{GDBN} source, refer to
33924 it by context, not by line number.
33926 The line numbers in our development sources will not match those in your
33927 sources. Your line numbers would convey no useful information to us.
33931 Here are some things that are not necessary:
33935 A description of the envelope of the bug.
33937 Often people who encounter a bug spend a lot of time investigating
33938 which changes to the input file will make the bug go away and which
33939 changes will not affect it.
33941 This is often time consuming and not very useful, because the way we
33942 will find the bug is by running a single example under the debugger
33943 with breakpoints, not by pure deduction from a series of examples.
33944 We recommend that you save your time for something else.
33946 Of course, if you can find a simpler example to report @emph{instead}
33947 of the original one, that is a convenience for us. Errors in the
33948 output will be easier to spot, running under the debugger will take
33949 less time, and so on.
33951 However, simplification is not vital; if you do not want to do this,
33952 report the bug anyway and send us the entire test case you used.
33955 A patch for the bug.
33957 A patch for the bug does help us if it is a good one. But do not omit
33958 the necessary information, such as the test case, on the assumption that
33959 a patch is all we need. We might see problems with your patch and decide
33960 to fix the problem another way, or we might not understand it at all.
33962 Sometimes with a program as complicated as @value{GDBN} it is very hard to
33963 construct an example that will make the program follow a certain path
33964 through the code. If you do not send us the example, we will not be able
33965 to construct one, so we will not be able to verify that the bug is fixed.
33967 And if we cannot understand what bug you are trying to fix, or why your
33968 patch should be an improvement, we will not install it. A test case will
33969 help us to understand.
33972 A guess about what the bug is or what it depends on.
33974 Such guesses are usually wrong. Even we cannot guess right about such
33975 things without first using the debugger to find the facts.
33978 @c The readline documentation is distributed with the readline code
33979 @c and consists of the two following files:
33982 @c Use -I with makeinfo to point to the appropriate directory,
33983 @c environment var TEXINPUTS with TeX.
33984 @ifclear SYSTEM_READLINE
33985 @include rluser.texi
33986 @include hsuser.texi
33990 @appendix In Memoriam
33992 The @value{GDBN} project mourns the loss of the following long-time
33997 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
33998 to Free Software in general. Outside of @value{GDBN}, he was known in
33999 the Amiga world for his series of Fish Disks, and the GeekGadget project.
34001 @item Michael Snyder
34002 Michael was one of the Global Maintainers of the @value{GDBN} project,
34003 with contributions recorded as early as 1996, until 2011. In addition
34004 to his day to day participation, he was a large driving force behind
34005 adding Reverse Debugging to @value{GDBN}.
34008 Beyond their technical contributions to the project, they were also
34009 enjoyable members of the Free Software Community. We will miss them.
34011 @node Formatting Documentation
34012 @appendix Formatting Documentation
34014 @cindex @value{GDBN} reference card
34015 @cindex reference card
34016 The @value{GDBN} 4 release includes an already-formatted reference card, ready
34017 for printing with PostScript or Ghostscript, in the @file{gdb}
34018 subdirectory of the main source directory@footnote{In
34019 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
34020 release.}. If you can use PostScript or Ghostscript with your printer,
34021 you can print the reference card immediately with @file{refcard.ps}.
34023 The release also includes the source for the reference card. You
34024 can format it, using @TeX{}, by typing:
34030 The @value{GDBN} reference card is designed to print in @dfn{landscape}
34031 mode on US ``letter'' size paper;
34032 that is, on a sheet 11 inches wide by 8.5 inches
34033 high. You will need to specify this form of printing as an option to
34034 your @sc{dvi} output program.
34036 @cindex documentation
34038 All the documentation for @value{GDBN} comes as part of the machine-readable
34039 distribution. The documentation is written in Texinfo format, which is
34040 a documentation system that uses a single source file to produce both
34041 on-line information and a printed manual. You can use one of the Info
34042 formatting commands to create the on-line version of the documentation
34043 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
34045 @value{GDBN} includes an already formatted copy of the on-line Info
34046 version of this manual in the @file{gdb} subdirectory. The main Info
34047 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
34048 subordinate files matching @samp{gdb.info*} in the same directory. If
34049 necessary, you can print out these files, or read them with any editor;
34050 but they are easier to read using the @code{info} subsystem in @sc{gnu}
34051 Emacs or the standalone @code{info} program, available as part of the
34052 @sc{gnu} Texinfo distribution.
34054 If you want to format these Info files yourself, you need one of the
34055 Info formatting programs, such as @code{texinfo-format-buffer} or
34058 If you have @code{makeinfo} installed, and are in the top level
34059 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
34060 version @value{GDBVN}), you can make the Info file by typing:
34067 If you want to typeset and print copies of this manual, you need @TeX{},
34068 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
34069 Texinfo definitions file.
34071 @TeX{} is a typesetting program; it does not print files directly, but
34072 produces output files called @sc{dvi} files. To print a typeset
34073 document, you need a program to print @sc{dvi} files. If your system
34074 has @TeX{} installed, chances are it has such a program. The precise
34075 command to use depends on your system; @kbd{lpr -d} is common; another
34076 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
34077 require a file name without any extension or a @samp{.dvi} extension.
34079 @TeX{} also requires a macro definitions file called
34080 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
34081 written in Texinfo format. On its own, @TeX{} cannot either read or
34082 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
34083 and is located in the @file{gdb-@var{version-number}/texinfo}
34086 If you have @TeX{} and a @sc{dvi} printer program installed, you can
34087 typeset and print this manual. First switch to the @file{gdb}
34088 subdirectory of the main source directory (for example, to
34089 @file{gdb-@value{GDBVN}/gdb}) and type:
34095 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
34097 @node Installing GDB
34098 @appendix Installing @value{GDBN}
34099 @cindex installation
34102 * Requirements:: Requirements for building @value{GDBN}
34103 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
34104 * Separate Objdir:: Compiling @value{GDBN} in another directory
34105 * Config Names:: Specifying names for hosts and targets
34106 * Configure Options:: Summary of options for configure
34107 * System-wide configuration:: Having a system-wide init file
34111 @section Requirements for Building @value{GDBN}
34112 @cindex building @value{GDBN}, requirements for
34114 Building @value{GDBN} requires various tools and packages to be available.
34115 Other packages will be used only if they are found.
34117 @heading Tools/Packages Necessary for Building @value{GDBN}
34119 @item ISO C90 compiler
34120 @value{GDBN} is written in ISO C90. It should be buildable with any
34121 working C90 compiler, e.g.@: GCC.
34125 @heading Tools/Packages Optional for Building @value{GDBN}
34129 @value{GDBN} can use the Expat XML parsing library. This library may be
34130 included with your operating system distribution; if it is not, you
34131 can get the latest version from @url{http://expat.sourceforge.net}.
34132 The @file{configure} script will search for this library in several
34133 standard locations; if it is installed in an unusual path, you can
34134 use the @option{--with-libexpat-prefix} option to specify its location.
34140 Remote protocol memory maps (@pxref{Memory Map Format})
34142 Target descriptions (@pxref{Target Descriptions})
34144 Remote shared library lists (@xref{Library List Format},
34145 or alternatively @pxref{Library List Format for SVR4 Targets})
34147 MS-Windows shared libraries (@pxref{Shared Libraries})
34149 Traceframe info (@pxref{Traceframe Info Format})
34153 @cindex compressed debug sections
34154 @value{GDBN} will use the @samp{zlib} library, if available, to read
34155 compressed debug sections. Some linkers, such as GNU gold, are capable
34156 of producing binaries with compressed debug sections. If @value{GDBN}
34157 is compiled with @samp{zlib}, it will be able to read the debug
34158 information in such binaries.
34160 The @samp{zlib} library is likely included with your operating system
34161 distribution; if it is not, you can get the latest version from
34162 @url{http://zlib.net}.
34165 @value{GDBN}'s features related to character sets (@pxref{Character
34166 Sets}) require a functioning @code{iconv} implementation. If you are
34167 on a GNU system, then this is provided by the GNU C Library. Some
34168 other systems also provide a working @code{iconv}.
34170 If @value{GDBN} is using the @code{iconv} program which is installed
34171 in a non-standard place, you will need to tell @value{GDBN} where to find it.
34172 This is done with @option{--with-iconv-bin} which specifies the
34173 directory that contains the @code{iconv} program.
34175 On systems without @code{iconv}, you can install GNU Libiconv. If you
34176 have previously installed Libiconv, you can use the
34177 @option{--with-libiconv-prefix} option to configure.
34179 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
34180 arrange to build Libiconv if a directory named @file{libiconv} appears
34181 in the top-most source directory. If Libiconv is built this way, and
34182 if the operating system does not provide a suitable @code{iconv}
34183 implementation, then the just-built library will automatically be used
34184 by @value{GDBN}. One easy way to set this up is to download GNU
34185 Libiconv, unpack it, and then rename the directory holding the
34186 Libiconv source code to @samp{libiconv}.
34189 @node Running Configure
34190 @section Invoking the @value{GDBN} @file{configure} Script
34191 @cindex configuring @value{GDBN}
34192 @value{GDBN} comes with a @file{configure} script that automates the process
34193 of preparing @value{GDBN} for installation; you can then use @code{make} to
34194 build the @code{gdb} program.
34196 @c irrelevant in info file; it's as current as the code it lives with.
34197 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
34198 look at the @file{README} file in the sources; we may have improved the
34199 installation procedures since publishing this manual.}
34202 The @value{GDBN} distribution includes all the source code you need for
34203 @value{GDBN} in a single directory, whose name is usually composed by
34204 appending the version number to @samp{gdb}.
34206 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
34207 @file{gdb-@value{GDBVN}} directory. That directory contains:
34210 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
34211 script for configuring @value{GDBN} and all its supporting libraries
34213 @item gdb-@value{GDBVN}/gdb
34214 the source specific to @value{GDBN} itself
34216 @item gdb-@value{GDBVN}/bfd
34217 source for the Binary File Descriptor library
34219 @item gdb-@value{GDBVN}/include
34220 @sc{gnu} include files
34222 @item gdb-@value{GDBVN}/libiberty
34223 source for the @samp{-liberty} free software library
34225 @item gdb-@value{GDBVN}/opcodes
34226 source for the library of opcode tables and disassemblers
34228 @item gdb-@value{GDBVN}/readline
34229 source for the @sc{gnu} command-line interface
34231 @item gdb-@value{GDBVN}/glob
34232 source for the @sc{gnu} filename pattern-matching subroutine
34234 @item gdb-@value{GDBVN}/mmalloc
34235 source for the @sc{gnu} memory-mapped malloc package
34238 The simplest way to configure and build @value{GDBN} is to run @file{configure}
34239 from the @file{gdb-@var{version-number}} source directory, which in
34240 this example is the @file{gdb-@value{GDBVN}} directory.
34242 First switch to the @file{gdb-@var{version-number}} source directory
34243 if you are not already in it; then run @file{configure}. Pass the
34244 identifier for the platform on which @value{GDBN} will run as an
34250 cd gdb-@value{GDBVN}
34251 ./configure @var{host}
34256 where @var{host} is an identifier such as @samp{sun4} or
34257 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
34258 (You can often leave off @var{host}; @file{configure} tries to guess the
34259 correct value by examining your system.)
34261 Running @samp{configure @var{host}} and then running @code{make} builds the
34262 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
34263 libraries, then @code{gdb} itself. The configured source files, and the
34264 binaries, are left in the corresponding source directories.
34267 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
34268 system does not recognize this automatically when you run a different
34269 shell, you may need to run @code{sh} on it explicitly:
34272 sh configure @var{host}
34275 If you run @file{configure} from a directory that contains source
34276 directories for multiple libraries or programs, such as the
34277 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
34279 creates configuration files for every directory level underneath (unless
34280 you tell it not to, with the @samp{--norecursion} option).
34282 You should run the @file{configure} script from the top directory in the
34283 source tree, the @file{gdb-@var{version-number}} directory. If you run
34284 @file{configure} from one of the subdirectories, you will configure only
34285 that subdirectory. That is usually not what you want. In particular,
34286 if you run the first @file{configure} from the @file{gdb} subdirectory
34287 of the @file{gdb-@var{version-number}} directory, you will omit the
34288 configuration of @file{bfd}, @file{readline}, and other sibling
34289 directories of the @file{gdb} subdirectory. This leads to build errors
34290 about missing include files such as @file{bfd/bfd.h}.
34292 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
34293 However, you should make sure that the shell on your path (named by
34294 the @samp{SHELL} environment variable) is publicly readable. Remember
34295 that @value{GDBN} uses the shell to start your program---some systems refuse to
34296 let @value{GDBN} debug child processes whose programs are not readable.
34298 @node Separate Objdir
34299 @section Compiling @value{GDBN} in Another Directory
34301 If you want to run @value{GDBN} versions for several host or target machines,
34302 you need a different @code{gdb} compiled for each combination of
34303 host and target. @file{configure} is designed to make this easy by
34304 allowing you to generate each configuration in a separate subdirectory,
34305 rather than in the source directory. If your @code{make} program
34306 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
34307 @code{make} in each of these directories builds the @code{gdb}
34308 program specified there.
34310 To build @code{gdb} in a separate directory, run @file{configure}
34311 with the @samp{--srcdir} option to specify where to find the source.
34312 (You also need to specify a path to find @file{configure}
34313 itself from your working directory. If the path to @file{configure}
34314 would be the same as the argument to @samp{--srcdir}, you can leave out
34315 the @samp{--srcdir} option; it is assumed.)
34317 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
34318 separate directory for a Sun 4 like this:
34322 cd gdb-@value{GDBVN}
34325 ../gdb-@value{GDBVN}/configure sun4
34330 When @file{configure} builds a configuration using a remote source
34331 directory, it creates a tree for the binaries with the same structure
34332 (and using the same names) as the tree under the source directory. In
34333 the example, you'd find the Sun 4 library @file{libiberty.a} in the
34334 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
34335 @file{gdb-sun4/gdb}.
34337 Make sure that your path to the @file{configure} script has just one
34338 instance of @file{gdb} in it. If your path to @file{configure} looks
34339 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
34340 one subdirectory of @value{GDBN}, not the whole package. This leads to
34341 build errors about missing include files such as @file{bfd/bfd.h}.
34343 One popular reason to build several @value{GDBN} configurations in separate
34344 directories is to configure @value{GDBN} for cross-compiling (where
34345 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
34346 programs that run on another machine---the @dfn{target}).
34347 You specify a cross-debugging target by
34348 giving the @samp{--target=@var{target}} option to @file{configure}.
34350 When you run @code{make} to build a program or library, you must run
34351 it in a configured directory---whatever directory you were in when you
34352 called @file{configure} (or one of its subdirectories).
34354 The @code{Makefile} that @file{configure} generates in each source
34355 directory also runs recursively. If you type @code{make} in a source
34356 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
34357 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
34358 will build all the required libraries, and then build GDB.
34360 When you have multiple hosts or targets configured in separate
34361 directories, you can run @code{make} on them in parallel (for example,
34362 if they are NFS-mounted on each of the hosts); they will not interfere
34366 @section Specifying Names for Hosts and Targets
34368 The specifications used for hosts and targets in the @file{configure}
34369 script are based on a three-part naming scheme, but some short predefined
34370 aliases are also supported. The full naming scheme encodes three pieces
34371 of information in the following pattern:
34374 @var{architecture}-@var{vendor}-@var{os}
34377 For example, you can use the alias @code{sun4} as a @var{host} argument,
34378 or as the value for @var{target} in a @code{--target=@var{target}}
34379 option. The equivalent full name is @samp{sparc-sun-sunos4}.
34381 The @file{configure} script accompanying @value{GDBN} does not provide
34382 any query facility to list all supported host and target names or
34383 aliases. @file{configure} calls the Bourne shell script
34384 @code{config.sub} to map abbreviations to full names; you can read the
34385 script, if you wish, or you can use it to test your guesses on
34386 abbreviations---for example:
34389 % sh config.sub i386-linux
34391 % sh config.sub alpha-linux
34392 alpha-unknown-linux-gnu
34393 % sh config.sub hp9k700
34395 % sh config.sub sun4
34396 sparc-sun-sunos4.1.1
34397 % sh config.sub sun3
34398 m68k-sun-sunos4.1.1
34399 % sh config.sub i986v
34400 Invalid configuration `i986v': machine `i986v' not recognized
34404 @code{config.sub} is also distributed in the @value{GDBN} source
34405 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
34407 @node Configure Options
34408 @section @file{configure} Options
34410 Here is a summary of the @file{configure} options and arguments that
34411 are most often useful for building @value{GDBN}. @file{configure} also has
34412 several other options not listed here. @inforef{What Configure
34413 Does,,configure.info}, for a full explanation of @file{configure}.
34416 configure @r{[}--help@r{]}
34417 @r{[}--prefix=@var{dir}@r{]}
34418 @r{[}--exec-prefix=@var{dir}@r{]}
34419 @r{[}--srcdir=@var{dirname}@r{]}
34420 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
34421 @r{[}--target=@var{target}@r{]}
34426 You may introduce options with a single @samp{-} rather than
34427 @samp{--} if you prefer; but you may abbreviate option names if you use
34432 Display a quick summary of how to invoke @file{configure}.
34434 @item --prefix=@var{dir}
34435 Configure the source to install programs and files under directory
34438 @item --exec-prefix=@var{dir}
34439 Configure the source to install programs under directory
34442 @c avoid splitting the warning from the explanation:
34444 @item --srcdir=@var{dirname}
34445 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
34446 @code{make} that implements the @code{VPATH} feature.}@*
34447 Use this option to make configurations in directories separate from the
34448 @value{GDBN} source directories. Among other things, you can use this to
34449 build (or maintain) several configurations simultaneously, in separate
34450 directories. @file{configure} writes configuration-specific files in
34451 the current directory, but arranges for them to use the source in the
34452 directory @var{dirname}. @file{configure} creates directories under
34453 the working directory in parallel to the source directories below
34456 @item --norecursion
34457 Configure only the directory level where @file{configure} is executed; do not
34458 propagate configuration to subdirectories.
34460 @item --target=@var{target}
34461 Configure @value{GDBN} for cross-debugging programs running on the specified
34462 @var{target}. Without this option, @value{GDBN} is configured to debug
34463 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
34465 There is no convenient way to generate a list of all available targets.
34467 @item @var{host} @dots{}
34468 Configure @value{GDBN} to run on the specified @var{host}.
34470 There is no convenient way to generate a list of all available hosts.
34473 There are many other options available as well, but they are generally
34474 needed for special purposes only.
34476 @node System-wide configuration
34477 @section System-wide configuration and settings
34478 @cindex system-wide init file
34480 @value{GDBN} can be configured to have a system-wide init file;
34481 this file will be read and executed at startup (@pxref{Startup, , What
34482 @value{GDBN} does during startup}).
34484 Here is the corresponding configure option:
34487 @item --with-system-gdbinit=@var{file}
34488 Specify that the default location of the system-wide init file is
34492 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
34493 it may be subject to relocation. Two possible cases:
34497 If the default location of this init file contains @file{$prefix},
34498 it will be subject to relocation. Suppose that the configure options
34499 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
34500 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
34501 init file is looked for as @file{$install/etc/gdbinit} instead of
34502 @file{$prefix/etc/gdbinit}.
34505 By contrast, if the default location does not contain the prefix,
34506 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
34507 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
34508 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
34509 wherever @value{GDBN} is installed.
34512 @node Maintenance Commands
34513 @appendix Maintenance Commands
34514 @cindex maintenance commands
34515 @cindex internal commands
34517 In addition to commands intended for @value{GDBN} users, @value{GDBN}
34518 includes a number of commands intended for @value{GDBN} developers,
34519 that are not documented elsewhere in this manual. These commands are
34520 provided here for reference. (For commands that turn on debugging
34521 messages, see @ref{Debugging Output}.)
34524 @kindex maint agent
34525 @kindex maint agent-eval
34526 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
34527 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
34528 Translate the given @var{expression} into remote agent bytecodes.
34529 This command is useful for debugging the Agent Expression mechanism
34530 (@pxref{Agent Expressions}). The @samp{agent} version produces an
34531 expression useful for data collection, such as by tracepoints, while
34532 @samp{maint agent-eval} produces an expression that evaluates directly
34533 to a result. For instance, a collection expression for @code{globa +
34534 globb} will include bytecodes to record four bytes of memory at each
34535 of the addresses of @code{globa} and @code{globb}, while discarding
34536 the result of the addition, while an evaluation expression will do the
34537 addition and return the sum.
34538 If @code{-at} is given, generate remote agent bytecode for @var{location}.
34539 If not, generate remote agent bytecode for current frame PC address.
34541 @kindex maint agent-printf
34542 @item maint agent-printf @var{format},@var{expr},...
34543 Translate the given format string and list of argument expressions
34544 into remote agent bytecodes and display them as a disassembled list.
34545 This command is useful for debugging the agent version of dynamic
34546 printf (@pxref{Dynamic Printf}.
34548 @kindex maint info breakpoints
34549 @item @anchor{maint info breakpoints}maint info breakpoints
34550 Using the same format as @samp{info breakpoints}, display both the
34551 breakpoints you've set explicitly, and those @value{GDBN} is using for
34552 internal purposes. Internal breakpoints are shown with negative
34553 breakpoint numbers. The type column identifies what kind of breakpoint
34558 Normal, explicitly set breakpoint.
34561 Normal, explicitly set watchpoint.
34564 Internal breakpoint, used to handle correctly stepping through
34565 @code{longjmp} calls.
34567 @item longjmp resume
34568 Internal breakpoint at the target of a @code{longjmp}.
34571 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
34574 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
34577 Shared library events.
34581 @kindex maint info bfds
34582 @item maint info bfds
34583 This prints information about each @code{bfd} object that is known to
34584 @value{GDBN}. @xref{Top, , BFD, bfd, The Binary File Descriptor Library}.
34586 @kindex set displaced-stepping
34587 @kindex show displaced-stepping
34588 @cindex displaced stepping support
34589 @cindex out-of-line single-stepping
34590 @item set displaced-stepping
34591 @itemx show displaced-stepping
34592 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
34593 if the target supports it. Displaced stepping is a way to single-step
34594 over breakpoints without removing them from the inferior, by executing
34595 an out-of-line copy of the instruction that was originally at the
34596 breakpoint location. It is also known as out-of-line single-stepping.
34599 @item set displaced-stepping on
34600 If the target architecture supports it, @value{GDBN} will use
34601 displaced stepping to step over breakpoints.
34603 @item set displaced-stepping off
34604 @value{GDBN} will not use displaced stepping to step over breakpoints,
34605 even if such is supported by the target architecture.
34607 @cindex non-stop mode, and @samp{set displaced-stepping}
34608 @item set displaced-stepping auto
34609 This is the default mode. @value{GDBN} will use displaced stepping
34610 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
34611 architecture supports displaced stepping.
34614 @kindex maint check-symtabs
34615 @item maint check-symtabs
34616 Check the consistency of psymtabs and symtabs.
34618 @kindex maint cplus first_component
34619 @item maint cplus first_component @var{name}
34620 Print the first C@t{++} class/namespace component of @var{name}.
34622 @kindex maint cplus namespace
34623 @item maint cplus namespace
34624 Print the list of possible C@t{++} namespaces.
34626 @kindex maint demangle
34627 @item maint demangle @var{name}
34628 Demangle a C@t{++} or Objective-C mangled @var{name}.
34630 @kindex maint deprecate
34631 @kindex maint undeprecate
34632 @cindex deprecated commands
34633 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
34634 @itemx maint undeprecate @var{command}
34635 Deprecate or undeprecate the named @var{command}. Deprecated commands
34636 cause @value{GDBN} to issue a warning when you use them. The optional
34637 argument @var{replacement} says which newer command should be used in
34638 favor of the deprecated one; if it is given, @value{GDBN} will mention
34639 the replacement as part of the warning.
34641 @kindex maint dump-me
34642 @item maint dump-me
34643 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
34644 Cause a fatal signal in the debugger and force it to dump its core.
34645 This is supported only on systems which support aborting a program
34646 with the @code{SIGQUIT} signal.
34648 @kindex maint internal-error
34649 @kindex maint internal-warning
34650 @item maint internal-error @r{[}@var{message-text}@r{]}
34651 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
34652 Cause @value{GDBN} to call the internal function @code{internal_error}
34653 or @code{internal_warning} and hence behave as though an internal error
34654 or internal warning has been detected. In addition to reporting the
34655 internal problem, these functions give the user the opportunity to
34656 either quit @value{GDBN} or create a core file of the current
34657 @value{GDBN} session.
34659 These commands take an optional parameter @var{message-text} that is
34660 used as the text of the error or warning message.
34662 Here's an example of using @code{internal-error}:
34665 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
34666 @dots{}/maint.c:121: internal-error: testing, 1, 2
34667 A problem internal to GDB has been detected. Further
34668 debugging may prove unreliable.
34669 Quit this debugging session? (y or n) @kbd{n}
34670 Create a core file? (y or n) @kbd{n}
34674 @cindex @value{GDBN} internal error
34675 @cindex internal errors, control of @value{GDBN} behavior
34677 @kindex maint set internal-error
34678 @kindex maint show internal-error
34679 @kindex maint set internal-warning
34680 @kindex maint show internal-warning
34681 @item maint set internal-error @var{action} [ask|yes|no]
34682 @itemx maint show internal-error @var{action}
34683 @itemx maint set internal-warning @var{action} [ask|yes|no]
34684 @itemx maint show internal-warning @var{action}
34685 When @value{GDBN} reports an internal problem (error or warning) it
34686 gives the user the opportunity to both quit @value{GDBN} and create a
34687 core file of the current @value{GDBN} session. These commands let you
34688 override the default behaviour for each particular @var{action},
34689 described in the table below.
34693 You can specify that @value{GDBN} should always (yes) or never (no)
34694 quit. The default is to ask the user what to do.
34697 You can specify that @value{GDBN} should always (yes) or never (no)
34698 create a core file. The default is to ask the user what to do.
34701 @kindex maint packet
34702 @item maint packet @var{text}
34703 If @value{GDBN} is talking to an inferior via the serial protocol,
34704 then this command sends the string @var{text} to the inferior, and
34705 displays the response packet. @value{GDBN} supplies the initial
34706 @samp{$} character, the terminating @samp{#} character, and the
34709 @kindex maint print architecture
34710 @item maint print architecture @r{[}@var{file}@r{]}
34711 Print the entire architecture configuration. The optional argument
34712 @var{file} names the file where the output goes.
34714 @kindex maint print c-tdesc
34715 @item maint print c-tdesc
34716 Print the current target description (@pxref{Target Descriptions}) as
34717 a C source file. The created source file can be used in @value{GDBN}
34718 when an XML parser is not available to parse the description.
34720 @kindex maint print dummy-frames
34721 @item maint print dummy-frames
34722 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
34725 (@value{GDBP}) @kbd{b add}
34727 (@value{GDBP}) @kbd{print add(2,3)}
34728 Breakpoint 2, add (a=2, b=3) at @dots{}
34730 The program being debugged stopped while in a function called from GDB.
34732 (@value{GDBP}) @kbd{maint print dummy-frames}
34733 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
34734 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
34735 call_lo=0x01014000 call_hi=0x01014001
34739 Takes an optional file parameter.
34741 @kindex maint print registers
34742 @kindex maint print raw-registers
34743 @kindex maint print cooked-registers
34744 @kindex maint print register-groups
34745 @kindex maint print remote-registers
34746 @item maint print registers @r{[}@var{file}@r{]}
34747 @itemx maint print raw-registers @r{[}@var{file}@r{]}
34748 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
34749 @itemx maint print register-groups @r{[}@var{file}@r{]}
34750 @itemx maint print remote-registers @r{[}@var{file}@r{]}
34751 Print @value{GDBN}'s internal register data structures.
34753 The command @code{maint print raw-registers} includes the contents of
34754 the raw register cache; the command @code{maint print
34755 cooked-registers} includes the (cooked) value of all registers,
34756 including registers which aren't available on the target nor visible
34757 to user; the command @code{maint print register-groups} includes the
34758 groups that each register is a member of; and the command @code{maint
34759 print remote-registers} includes the remote target's register numbers
34760 and offsets in the `G' packets. @xref{Registers,, Registers, gdbint,
34761 @value{GDBN} Internals}.
34763 These commands take an optional parameter, a file name to which to
34764 write the information.
34766 @kindex maint print reggroups
34767 @item maint print reggroups @r{[}@var{file}@r{]}
34768 Print @value{GDBN}'s internal register group data structures. The
34769 optional argument @var{file} tells to what file to write the
34772 The register groups info looks like this:
34775 (@value{GDBP}) @kbd{maint print reggroups}
34788 This command forces @value{GDBN} to flush its internal register cache.
34790 @kindex maint print objfiles
34791 @cindex info for known object files
34792 @item maint print objfiles
34793 Print a dump of all known object files. For each object file, this
34794 command prints its name, address in memory, and all of its psymtabs
34797 @kindex maint print section-scripts
34798 @cindex info for known .debug_gdb_scripts-loaded scripts
34799 @item maint print section-scripts [@var{regexp}]
34800 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
34801 If @var{regexp} is specified, only print scripts loaded by object files
34802 matching @var{regexp}.
34803 For each script, this command prints its name as specified in the objfile,
34804 and the full path if known.
34805 @xref{dotdebug_gdb_scripts section}.
34807 @kindex maint print statistics
34808 @cindex bcache statistics
34809 @item maint print statistics
34810 This command prints, for each object file in the program, various data
34811 about that object file followed by the byte cache (@dfn{bcache})
34812 statistics for the object file. The objfile data includes the number
34813 of minimal, partial, full, and stabs symbols, the number of types
34814 defined by the objfile, the number of as yet unexpanded psym tables,
34815 the number of line tables and string tables, and the amount of memory
34816 used by the various tables. The bcache statistics include the counts,
34817 sizes, and counts of duplicates of all and unique objects, max,
34818 average, and median entry size, total memory used and its overhead and
34819 savings, and various measures of the hash table size and chain
34822 @kindex maint print target-stack
34823 @cindex target stack description
34824 @item maint print target-stack
34825 A @dfn{target} is an interface between the debugger and a particular
34826 kind of file or process. Targets can be stacked in @dfn{strata},
34827 so that more than one target can potentially respond to a request.
34828 In particular, memory accesses will walk down the stack of targets
34829 until they find a target that is interested in handling that particular
34832 This command prints a short description of each layer that was pushed on
34833 the @dfn{target stack}, starting from the top layer down to the bottom one.
34835 @kindex maint print type
34836 @cindex type chain of a data type
34837 @item maint print type @var{expr}
34838 Print the type chain for a type specified by @var{expr}. The argument
34839 can be either a type name or a symbol. If it is a symbol, the type of
34840 that symbol is described. The type chain produced by this command is
34841 a recursive definition of the data type as stored in @value{GDBN}'s
34842 data structures, including its flags and contained types.
34844 @kindex maint set dwarf2 always-disassemble
34845 @kindex maint show dwarf2 always-disassemble
34846 @item maint set dwarf2 always-disassemble
34847 @item maint show dwarf2 always-disassemble
34848 Control the behavior of @code{info address} when using DWARF debugging
34851 The default is @code{off}, which means that @value{GDBN} should try to
34852 describe a variable's location in an easily readable format. When
34853 @code{on}, @value{GDBN} will instead display the DWARF location
34854 expression in an assembly-like format. Note that some locations are
34855 too complex for @value{GDBN} to describe simply; in this case you will
34856 always see the disassembly form.
34858 Here is an example of the resulting disassembly:
34861 (gdb) info addr argc
34862 Symbol "argc" is a complex DWARF expression:
34866 For more information on these expressions, see
34867 @uref{http://www.dwarfstd.org/, the DWARF standard}.
34869 @kindex maint set dwarf2 max-cache-age
34870 @kindex maint show dwarf2 max-cache-age
34871 @item maint set dwarf2 max-cache-age
34872 @itemx maint show dwarf2 max-cache-age
34873 Control the DWARF 2 compilation unit cache.
34875 @cindex DWARF 2 compilation units cache
34876 In object files with inter-compilation-unit references, such as those
34877 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
34878 reader needs to frequently refer to previously read compilation units.
34879 This setting controls how long a compilation unit will remain in the
34880 cache if it is not referenced. A higher limit means that cached
34881 compilation units will be stored in memory longer, and more total
34882 memory will be used. Setting it to zero disables caching, which will
34883 slow down @value{GDBN} startup, but reduce memory consumption.
34885 @kindex maint set profile
34886 @kindex maint show profile
34887 @cindex profiling GDB
34888 @item maint set profile
34889 @itemx maint show profile
34890 Control profiling of @value{GDBN}.
34892 Profiling will be disabled until you use the @samp{maint set profile}
34893 command to enable it. When you enable profiling, the system will begin
34894 collecting timing and execution count data; when you disable profiling or
34895 exit @value{GDBN}, the results will be written to a log file. Remember that
34896 if you use profiling, @value{GDBN} will overwrite the profiling log file
34897 (often called @file{gmon.out}). If you have a record of important profiling
34898 data in a @file{gmon.out} file, be sure to move it to a safe location.
34900 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
34901 compiled with the @samp{-pg} compiler option.
34903 @kindex maint set show-debug-regs
34904 @kindex maint show show-debug-regs
34905 @cindex hardware debug registers
34906 @item maint set show-debug-regs
34907 @itemx maint show show-debug-regs
34908 Control whether to show variables that mirror the hardware debug
34909 registers. Use @code{ON} to enable, @code{OFF} to disable. If
34910 enabled, the debug registers values are shown when @value{GDBN} inserts or
34911 removes a hardware breakpoint or watchpoint, and when the inferior
34912 triggers a hardware-assisted breakpoint or watchpoint.
34914 @kindex maint set show-all-tib
34915 @kindex maint show show-all-tib
34916 @item maint set show-all-tib
34917 @itemx maint show show-all-tib
34918 Control whether to show all non zero areas within a 1k block starting
34919 at thread local base, when using the @samp{info w32 thread-information-block}
34922 @kindex maint space
34923 @cindex memory used by commands
34925 Control whether to display memory usage for each command. If set to a
34926 nonzero value, @value{GDBN} will display how much memory each command
34927 took, following the command's own output. This can also be requested
34928 by invoking @value{GDBN} with the @option{--statistics} command-line
34929 switch (@pxref{Mode Options}).
34932 @cindex time of command execution
34934 Control whether to display the execution time of @value{GDBN} for each command.
34935 If set to a nonzero value, @value{GDBN} will display how much time it
34936 took to execute each command, following the command's own output.
34937 Both CPU time and wallclock time are printed.
34938 Printing both is useful when trying to determine whether the cost is
34939 CPU or, e.g., disk/network, latency.
34940 Note that the CPU time printed is for @value{GDBN} only, it does not include
34941 the execution time of the inferior because there's no mechanism currently
34942 to compute how much time was spent by @value{GDBN} and how much time was
34943 spent by the program been debugged.
34944 This can also be requested by invoking @value{GDBN} with the
34945 @option{--statistics} command-line switch (@pxref{Mode Options}).
34947 @kindex maint translate-address
34948 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
34949 Find the symbol stored at the location specified by the address
34950 @var{addr} and an optional section name @var{section}. If found,
34951 @value{GDBN} prints the name of the closest symbol and an offset from
34952 the symbol's location to the specified address. This is similar to
34953 the @code{info address} command (@pxref{Symbols}), except that this
34954 command also allows to find symbols in other sections.
34956 If section was not specified, the section in which the symbol was found
34957 is also printed. For dynamically linked executables, the name of
34958 executable or shared library containing the symbol is printed as well.
34962 The following command is useful for non-interactive invocations of
34963 @value{GDBN}, such as in the test suite.
34966 @item set watchdog @var{nsec}
34967 @kindex set watchdog
34968 @cindex watchdog timer
34969 @cindex timeout for commands
34970 Set the maximum number of seconds @value{GDBN} will wait for the
34971 target operation to finish. If this time expires, @value{GDBN}
34972 reports and error and the command is aborted.
34974 @item show watchdog
34975 Show the current setting of the target wait timeout.
34978 @node Remote Protocol
34979 @appendix @value{GDBN} Remote Serial Protocol
34984 * Stop Reply Packets::
34985 * General Query Packets::
34986 * Architecture-Specific Protocol Details::
34987 * Tracepoint Packets::
34988 * Host I/O Packets::
34990 * Notification Packets::
34991 * Remote Non-Stop::
34992 * Packet Acknowledgment::
34994 * File-I/O Remote Protocol Extension::
34995 * Library List Format::
34996 * Library List Format for SVR4 Targets::
34997 * Memory Map Format::
34998 * Thread List Format::
34999 * Traceframe Info Format::
35005 There may be occasions when you need to know something about the
35006 protocol---for example, if there is only one serial port to your target
35007 machine, you might want your program to do something special if it
35008 recognizes a packet meant for @value{GDBN}.
35010 In the examples below, @samp{->} and @samp{<-} are used to indicate
35011 transmitted and received data, respectively.
35013 @cindex protocol, @value{GDBN} remote serial
35014 @cindex serial protocol, @value{GDBN} remote
35015 @cindex remote serial protocol
35016 All @value{GDBN} commands and responses (other than acknowledgments
35017 and notifications, see @ref{Notification Packets}) are sent as a
35018 @var{packet}. A @var{packet} is introduced with the character
35019 @samp{$}, the actual @var{packet-data}, and the terminating character
35020 @samp{#} followed by a two-digit @var{checksum}:
35023 @code{$}@var{packet-data}@code{#}@var{checksum}
35027 @cindex checksum, for @value{GDBN} remote
35029 The two-digit @var{checksum} is computed as the modulo 256 sum of all
35030 characters between the leading @samp{$} and the trailing @samp{#} (an
35031 eight bit unsigned checksum).
35033 Implementors should note that prior to @value{GDBN} 5.0 the protocol
35034 specification also included an optional two-digit @var{sequence-id}:
35037 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
35040 @cindex sequence-id, for @value{GDBN} remote
35042 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
35043 has never output @var{sequence-id}s. Stubs that handle packets added
35044 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
35046 When either the host or the target machine receives a packet, the first
35047 response expected is an acknowledgment: either @samp{+} (to indicate
35048 the package was received correctly) or @samp{-} (to request
35052 -> @code{$}@var{packet-data}@code{#}@var{checksum}
35057 The @samp{+}/@samp{-} acknowledgments can be disabled
35058 once a connection is established.
35059 @xref{Packet Acknowledgment}, for details.
35061 The host (@value{GDBN}) sends @var{command}s, and the target (the
35062 debugging stub incorporated in your program) sends a @var{response}. In
35063 the case of step and continue @var{command}s, the response is only sent
35064 when the operation has completed, and the target has again stopped all
35065 threads in all attached processes. This is the default all-stop mode
35066 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
35067 execution mode; see @ref{Remote Non-Stop}, for details.
35069 @var{packet-data} consists of a sequence of characters with the
35070 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
35073 @cindex remote protocol, field separator
35074 Fields within the packet should be separated using @samp{,} @samp{;} or
35075 @samp{:}. Except where otherwise noted all numbers are represented in
35076 @sc{hex} with leading zeros suppressed.
35078 Implementors should note that prior to @value{GDBN} 5.0, the character
35079 @samp{:} could not appear as the third character in a packet (as it
35080 would potentially conflict with the @var{sequence-id}).
35082 @cindex remote protocol, binary data
35083 @anchor{Binary Data}
35084 Binary data in most packets is encoded either as two hexadecimal
35085 digits per byte of binary data. This allowed the traditional remote
35086 protocol to work over connections which were only seven-bit clean.
35087 Some packets designed more recently assume an eight-bit clean
35088 connection, and use a more efficient encoding to send and receive
35091 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
35092 as an escape character. Any escaped byte is transmitted as the escape
35093 character followed by the original character XORed with @code{0x20}.
35094 For example, the byte @code{0x7d} would be transmitted as the two
35095 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
35096 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
35097 @samp{@}}) must always be escaped. Responses sent by the stub
35098 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
35099 is not interpreted as the start of a run-length encoded sequence
35102 Response @var{data} can be run-length encoded to save space.
35103 Run-length encoding replaces runs of identical characters with one
35104 instance of the repeated character, followed by a @samp{*} and a
35105 repeat count. The repeat count is itself sent encoded, to avoid
35106 binary characters in @var{data}: a value of @var{n} is sent as
35107 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
35108 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
35109 code 32) for a repeat count of 3. (This is because run-length
35110 encoding starts to win for counts 3 or more.) Thus, for example,
35111 @samp{0* } is a run-length encoding of ``0000'': the space character
35112 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
35115 The printable characters @samp{#} and @samp{$} or with a numeric value
35116 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
35117 seven repeats (@samp{$}) can be expanded using a repeat count of only
35118 five (@samp{"}). For example, @samp{00000000} can be encoded as
35121 The error response returned for some packets includes a two character
35122 error number. That number is not well defined.
35124 @cindex empty response, for unsupported packets
35125 For any @var{command} not supported by the stub, an empty response
35126 (@samp{$#00}) should be returned. That way it is possible to extend the
35127 protocol. A newer @value{GDBN} can tell if a packet is supported based
35130 At a minimum, a stub is required to support the @samp{g} and @samp{G}
35131 commands for register access, and the @samp{m} and @samp{M} commands
35132 for memory access. Stubs that only control single-threaded targets
35133 can implement run control with the @samp{c} (continue), and @samp{s}
35134 (step) commands. Stubs that support multi-threading targets should
35135 support the @samp{vCont} command. All other commands are optional.
35140 The following table provides a complete list of all currently defined
35141 @var{command}s and their corresponding response @var{data}.
35142 @xref{File-I/O Remote Protocol Extension}, for details about the File
35143 I/O extension of the remote protocol.
35145 Each packet's description has a template showing the packet's overall
35146 syntax, followed by an explanation of the packet's meaning. We
35147 include spaces in some of the templates for clarity; these are not
35148 part of the packet's syntax. No @value{GDBN} packet uses spaces to
35149 separate its components. For example, a template like @samp{foo
35150 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
35151 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
35152 @var{baz}. @value{GDBN} does not transmit a space character between the
35153 @samp{foo} and the @var{bar}, or between the @var{bar} and the
35156 @cindex @var{thread-id}, in remote protocol
35157 @anchor{thread-id syntax}
35158 Several packets and replies include a @var{thread-id} field to identify
35159 a thread. Normally these are positive numbers with a target-specific
35160 interpretation, formatted as big-endian hex strings. A @var{thread-id}
35161 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
35164 In addition, the remote protocol supports a multiprocess feature in
35165 which the @var{thread-id} syntax is extended to optionally include both
35166 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
35167 The @var{pid} (process) and @var{tid} (thread) components each have the
35168 format described above: a positive number with target-specific
35169 interpretation formatted as a big-endian hex string, literal @samp{-1}
35170 to indicate all processes or threads (respectively), or @samp{0} to
35171 indicate an arbitrary process or thread. Specifying just a process, as
35172 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
35173 error to specify all processes but a specific thread, such as
35174 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
35175 for those packets and replies explicitly documented to include a process
35176 ID, rather than a @var{thread-id}.
35178 The multiprocess @var{thread-id} syntax extensions are only used if both
35179 @value{GDBN} and the stub report support for the @samp{multiprocess}
35180 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
35183 Note that all packet forms beginning with an upper- or lower-case
35184 letter, other than those described here, are reserved for future use.
35186 Here are the packet descriptions.
35191 @cindex @samp{!} packet
35192 @anchor{extended mode}
35193 Enable extended mode. In extended mode, the remote server is made
35194 persistent. The @samp{R} packet is used to restart the program being
35200 The remote target both supports and has enabled extended mode.
35204 @cindex @samp{?} packet
35205 Indicate the reason the target halted. The reply is the same as for
35206 step and continue. This packet has a special interpretation when the
35207 target is in non-stop mode; see @ref{Remote Non-Stop}.
35210 @xref{Stop Reply Packets}, for the reply specifications.
35212 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
35213 @cindex @samp{A} packet
35214 Initialized @code{argv[]} array passed into program. @var{arglen}
35215 specifies the number of bytes in the hex encoded byte stream
35216 @var{arg}. See @code{gdbserver} for more details.
35221 The arguments were set.
35227 @cindex @samp{b} packet
35228 (Don't use this packet; its behavior is not well-defined.)
35229 Change the serial line speed to @var{baud}.
35231 JTC: @emph{When does the transport layer state change? When it's
35232 received, or after the ACK is transmitted. In either case, there are
35233 problems if the command or the acknowledgment packet is dropped.}
35235 Stan: @emph{If people really wanted to add something like this, and get
35236 it working for the first time, they ought to modify ser-unix.c to send
35237 some kind of out-of-band message to a specially-setup stub and have the
35238 switch happen "in between" packets, so that from remote protocol's point
35239 of view, nothing actually happened.}
35241 @item B @var{addr},@var{mode}
35242 @cindex @samp{B} packet
35243 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
35244 breakpoint at @var{addr}.
35246 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
35247 (@pxref{insert breakpoint or watchpoint packet}).
35249 @cindex @samp{bc} packet
35252 Backward continue. Execute the target system in reverse. No parameter.
35253 @xref{Reverse Execution}, for more information.
35256 @xref{Stop Reply Packets}, for the reply specifications.
35258 @cindex @samp{bs} packet
35261 Backward single step. Execute one instruction in reverse. No parameter.
35262 @xref{Reverse Execution}, for more information.
35265 @xref{Stop Reply Packets}, for the reply specifications.
35267 @item c @r{[}@var{addr}@r{]}
35268 @cindex @samp{c} packet
35269 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
35270 resume at current address.
35272 This packet is deprecated for multi-threading support. @xref{vCont
35276 @xref{Stop Reply Packets}, for the reply specifications.
35278 @item C @var{sig}@r{[};@var{addr}@r{]}
35279 @cindex @samp{C} packet
35280 Continue with signal @var{sig} (hex signal number). If
35281 @samp{;@var{addr}} is omitted, resume at same address.
35283 This packet is deprecated for multi-threading support. @xref{vCont
35287 @xref{Stop Reply Packets}, for the reply specifications.
35290 @cindex @samp{d} packet
35293 Don't use this packet; instead, define a general set packet
35294 (@pxref{General Query Packets}).
35298 @cindex @samp{D} packet
35299 The first form of the packet is used to detach @value{GDBN} from the
35300 remote system. It is sent to the remote target
35301 before @value{GDBN} disconnects via the @code{detach} command.
35303 The second form, including a process ID, is used when multiprocess
35304 protocol extensions are enabled (@pxref{multiprocess extensions}), to
35305 detach only a specific process. The @var{pid} is specified as a
35306 big-endian hex string.
35316 @item F @var{RC},@var{EE},@var{CF};@var{XX}
35317 @cindex @samp{F} packet
35318 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
35319 This is part of the File-I/O protocol extension. @xref{File-I/O
35320 Remote Protocol Extension}, for the specification.
35323 @anchor{read registers packet}
35324 @cindex @samp{g} packet
35325 Read general registers.
35329 @item @var{XX@dots{}}
35330 Each byte of register data is described by two hex digits. The bytes
35331 with the register are transmitted in target byte order. The size of
35332 each register and their position within the @samp{g} packet are
35333 determined by the @value{GDBN} internal gdbarch functions
35334 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
35335 specification of several standard @samp{g} packets is specified below.
35337 When reading registers from a trace frame (@pxref{Analyze Collected
35338 Data,,Using the Collected Data}), the stub may also return a string of
35339 literal @samp{x}'s in place of the register data digits, to indicate
35340 that the corresponding register has not been collected, thus its value
35341 is unavailable. For example, for an architecture with 4 registers of
35342 4 bytes each, the following reply indicates to @value{GDBN} that
35343 registers 0 and 2 have not been collected, while registers 1 and 3
35344 have been collected, and both have zero value:
35348 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
35355 @item G @var{XX@dots{}}
35356 @cindex @samp{G} packet
35357 Write general registers. @xref{read registers packet}, for a
35358 description of the @var{XX@dots{}} data.
35368 @item H @var{op} @var{thread-id}
35369 @cindex @samp{H} packet
35370 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
35371 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
35372 it should be @samp{c} for step and continue operations (note that this
35373 is deprecated, supporting the @samp{vCont} command is a better
35374 option), @samp{g} for other operations. The thread designator
35375 @var{thread-id} has the format and interpretation described in
35376 @ref{thread-id syntax}.
35387 @c 'H': How restrictive (or permissive) is the thread model. If a
35388 @c thread is selected and stopped, are other threads allowed
35389 @c to continue to execute? As I mentioned above, I think the
35390 @c semantics of each command when a thread is selected must be
35391 @c described. For example:
35393 @c 'g': If the stub supports threads and a specific thread is
35394 @c selected, returns the register block from that thread;
35395 @c otherwise returns current registers.
35397 @c 'G' If the stub supports threads and a specific thread is
35398 @c selected, sets the registers of the register block of
35399 @c that thread; otherwise sets current registers.
35401 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
35402 @anchor{cycle step packet}
35403 @cindex @samp{i} packet
35404 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
35405 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
35406 step starting at that address.
35409 @cindex @samp{I} packet
35410 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
35414 @cindex @samp{k} packet
35417 FIXME: @emph{There is no description of how to operate when a specific
35418 thread context has been selected (i.e.@: does 'k' kill only that
35421 @item m @var{addr},@var{length}
35422 @cindex @samp{m} packet
35423 Read @var{length} bytes of memory starting at address @var{addr}.
35424 Note that @var{addr} may not be aligned to any particular boundary.
35426 The stub need not use any particular size or alignment when gathering
35427 data from memory for the response; even if @var{addr} is word-aligned
35428 and @var{length} is a multiple of the word size, the stub is free to
35429 use byte accesses, or not. For this reason, this packet may not be
35430 suitable for accessing memory-mapped I/O devices.
35431 @cindex alignment of remote memory accesses
35432 @cindex size of remote memory accesses
35433 @cindex memory, alignment and size of remote accesses
35437 @item @var{XX@dots{}}
35438 Memory contents; each byte is transmitted as a two-digit hexadecimal
35439 number. The reply may contain fewer bytes than requested if the
35440 server was able to read only part of the region of memory.
35445 @item M @var{addr},@var{length}:@var{XX@dots{}}
35446 @cindex @samp{M} packet
35447 Write @var{length} bytes of memory starting at address @var{addr}.
35448 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
35449 hexadecimal number.
35456 for an error (this includes the case where only part of the data was
35461 @cindex @samp{p} packet
35462 Read the value of register @var{n}; @var{n} is in hex.
35463 @xref{read registers packet}, for a description of how the returned
35464 register value is encoded.
35468 @item @var{XX@dots{}}
35469 the register's value
35473 Indicating an unrecognized @var{query}.
35476 @item P @var{n@dots{}}=@var{r@dots{}}
35477 @anchor{write register packet}
35478 @cindex @samp{P} packet
35479 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
35480 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
35481 digits for each byte in the register (target byte order).
35491 @item q @var{name} @var{params}@dots{}
35492 @itemx Q @var{name} @var{params}@dots{}
35493 @cindex @samp{q} packet
35494 @cindex @samp{Q} packet
35495 General query (@samp{q}) and set (@samp{Q}). These packets are
35496 described fully in @ref{General Query Packets}.
35499 @cindex @samp{r} packet
35500 Reset the entire system.
35502 Don't use this packet; use the @samp{R} packet instead.
35505 @cindex @samp{R} packet
35506 Restart the program being debugged. @var{XX}, while needed, is ignored.
35507 This packet is only available in extended mode (@pxref{extended mode}).
35509 The @samp{R} packet has no reply.
35511 @item s @r{[}@var{addr}@r{]}
35512 @cindex @samp{s} packet
35513 Single step. @var{addr} is the address at which to resume. If
35514 @var{addr} is omitted, resume at same address.
35516 This packet is deprecated for multi-threading support. @xref{vCont
35520 @xref{Stop Reply Packets}, for the reply specifications.
35522 @item S @var{sig}@r{[};@var{addr}@r{]}
35523 @anchor{step with signal packet}
35524 @cindex @samp{S} packet
35525 Step with signal. This is analogous to the @samp{C} packet, but
35526 requests a single-step, rather than a normal resumption of execution.
35528 This packet is deprecated for multi-threading support. @xref{vCont
35532 @xref{Stop Reply Packets}, for the reply specifications.
35534 @item t @var{addr}:@var{PP},@var{MM}
35535 @cindex @samp{t} packet
35536 Search backwards starting at address @var{addr} for a match with pattern
35537 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
35538 @var{addr} must be at least 3 digits.
35540 @item T @var{thread-id}
35541 @cindex @samp{T} packet
35542 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
35547 thread is still alive
35553 Packets starting with @samp{v} are identified by a multi-letter name,
35554 up to the first @samp{;} or @samp{?} (or the end of the packet).
35556 @item vAttach;@var{pid}
35557 @cindex @samp{vAttach} packet
35558 Attach to a new process with the specified process ID @var{pid}.
35559 The process ID is a
35560 hexadecimal integer identifying the process. In all-stop mode, all
35561 threads in the attached process are stopped; in non-stop mode, it may be
35562 attached without being stopped if that is supported by the target.
35564 @c In non-stop mode, on a successful vAttach, the stub should set the
35565 @c current thread to a thread of the newly-attached process. After
35566 @c attaching, GDB queries for the attached process's thread ID with qC.
35567 @c Also note that, from a user perspective, whether or not the
35568 @c target is stopped on attach in non-stop mode depends on whether you
35569 @c use the foreground or background version of the attach command, not
35570 @c on what vAttach does; GDB does the right thing with respect to either
35571 @c stopping or restarting threads.
35573 This packet is only available in extended mode (@pxref{extended mode}).
35579 @item @r{Any stop packet}
35580 for success in all-stop mode (@pxref{Stop Reply Packets})
35582 for success in non-stop mode (@pxref{Remote Non-Stop})
35585 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
35586 @cindex @samp{vCont} packet
35587 @anchor{vCont packet}
35588 Resume the inferior, specifying different actions for each thread.
35589 If an action is specified with no @var{thread-id}, then it is applied to any
35590 threads that don't have a specific action specified; if no default action is
35591 specified then other threads should remain stopped in all-stop mode and
35592 in their current state in non-stop mode.
35593 Specifying multiple
35594 default actions is an error; specifying no actions is also an error.
35595 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
35597 Currently supported actions are:
35603 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
35607 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
35612 The optional argument @var{addr} normally associated with the
35613 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
35614 not supported in @samp{vCont}.
35616 The @samp{t} action is only relevant in non-stop mode
35617 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
35618 A stop reply should be generated for any affected thread not already stopped.
35619 When a thread is stopped by means of a @samp{t} action,
35620 the corresponding stop reply should indicate that the thread has stopped with
35621 signal @samp{0}, regardless of whether the target uses some other signal
35622 as an implementation detail.
35624 The stub must support @samp{vCont} if it reports support for
35625 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
35626 this case @samp{vCont} actions can be specified to apply to all threads
35627 in a process by using the @samp{p@var{pid}.-1} form of the
35631 @xref{Stop Reply Packets}, for the reply specifications.
35634 @cindex @samp{vCont?} packet
35635 Request a list of actions supported by the @samp{vCont} packet.
35639 @item vCont@r{[};@var{action}@dots{}@r{]}
35640 The @samp{vCont} packet is supported. Each @var{action} is a supported
35641 command in the @samp{vCont} packet.
35643 The @samp{vCont} packet is not supported.
35646 @item vFile:@var{operation}:@var{parameter}@dots{}
35647 @cindex @samp{vFile} packet
35648 Perform a file operation on the target system. For details,
35649 see @ref{Host I/O Packets}.
35651 @item vFlashErase:@var{addr},@var{length}
35652 @cindex @samp{vFlashErase} packet
35653 Direct the stub to erase @var{length} bytes of flash starting at
35654 @var{addr}. The region may enclose any number of flash blocks, but
35655 its start and end must fall on block boundaries, as indicated by the
35656 flash block size appearing in the memory map (@pxref{Memory Map
35657 Format}). @value{GDBN} groups flash memory programming operations
35658 together, and sends a @samp{vFlashDone} request after each group; the
35659 stub is allowed to delay erase operation until the @samp{vFlashDone}
35660 packet is received.
35670 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
35671 @cindex @samp{vFlashWrite} packet
35672 Direct the stub to write data to flash address @var{addr}. The data
35673 is passed in binary form using the same encoding as for the @samp{X}
35674 packet (@pxref{Binary Data}). The memory ranges specified by
35675 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
35676 not overlap, and must appear in order of increasing addresses
35677 (although @samp{vFlashErase} packets for higher addresses may already
35678 have been received; the ordering is guaranteed only between
35679 @samp{vFlashWrite} packets). If a packet writes to an address that was
35680 neither erased by a preceding @samp{vFlashErase} packet nor by some other
35681 target-specific method, the results are unpredictable.
35689 for vFlashWrite addressing non-flash memory
35695 @cindex @samp{vFlashDone} packet
35696 Indicate to the stub that flash programming operation is finished.
35697 The stub is permitted to delay or batch the effects of a group of
35698 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
35699 @samp{vFlashDone} packet is received. The contents of the affected
35700 regions of flash memory are unpredictable until the @samp{vFlashDone}
35701 request is completed.
35703 @item vKill;@var{pid}
35704 @cindex @samp{vKill} packet
35705 Kill the process with the specified process ID. @var{pid} is a
35706 hexadecimal integer identifying the process. This packet is used in
35707 preference to @samp{k} when multiprocess protocol extensions are
35708 supported; see @ref{multiprocess extensions}.
35718 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
35719 @cindex @samp{vRun} packet
35720 Run the program @var{filename}, passing it each @var{argument} on its
35721 command line. The file and arguments are hex-encoded strings. If
35722 @var{filename} is an empty string, the stub may use a default program
35723 (e.g.@: the last program run). The program is created in the stopped
35726 @c FIXME: What about non-stop mode?
35728 This packet is only available in extended mode (@pxref{extended mode}).
35734 @item @r{Any stop packet}
35735 for success (@pxref{Stop Reply Packets})
35739 @anchor{vStopped packet}
35740 @cindex @samp{vStopped} packet
35742 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
35743 reply and prompt for the stub to report another one.
35747 @item @r{Any stop packet}
35748 if there is another unreported stop event (@pxref{Stop Reply Packets})
35750 if there are no unreported stop events
35753 @item X @var{addr},@var{length}:@var{XX@dots{}}
35755 @cindex @samp{X} packet
35756 Write data to memory, where the data is transmitted in binary.
35757 @var{addr} is address, @var{length} is number of bytes,
35758 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
35768 @item z @var{type},@var{addr},@var{kind}
35769 @itemx Z @var{type},@var{addr},@var{kind}
35770 @anchor{insert breakpoint or watchpoint packet}
35771 @cindex @samp{z} packet
35772 @cindex @samp{Z} packets
35773 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
35774 watchpoint starting at address @var{address} of kind @var{kind}.
35776 Each breakpoint and watchpoint packet @var{type} is documented
35779 @emph{Implementation notes: A remote target shall return an empty string
35780 for an unrecognized breakpoint or watchpoint packet @var{type}. A
35781 remote target shall support either both or neither of a given
35782 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
35783 avoid potential problems with duplicate packets, the operations should
35784 be implemented in an idempotent way.}
35786 @item z0,@var{addr},@var{kind}
35787 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
35788 @cindex @samp{z0} packet
35789 @cindex @samp{Z0} packet
35790 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
35791 @var{addr} of type @var{kind}.
35793 A memory breakpoint is implemented by replacing the instruction at
35794 @var{addr} with a software breakpoint or trap instruction. The
35795 @var{kind} is target-specific and typically indicates the size of
35796 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
35797 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
35798 architectures have additional meanings for @var{kind};
35799 @var{cond_list} is an optional list of conditional expressions in bytecode
35800 form that should be evaluated on the target's side. These are the
35801 conditions that should be taken into consideration when deciding if
35802 the breakpoint trigger should be reported back to @var{GDBN}.
35804 The @var{cond_list} parameter is comprised of a series of expressions,
35805 concatenated without separators. Each expression has the following form:
35809 @item X @var{len},@var{expr}
35810 @var{len} is the length of the bytecode expression and @var{expr} is the
35811 actual conditional expression in bytecode form.
35815 The optional @var{cmd_list} parameter introduces commands that may be
35816 run on the target, rather than being reported back to @value{GDBN}.
35817 The parameter starts with a numeric flag @var{persist}; if the flag is
35818 nonzero, then the breakpoint may remain active and the commands
35819 continue to be run even when @value{GDBN} disconnects from the target.
35820 Following this flag is a series of expressions concatenated with no
35821 separators. Each expression has the following form:
35825 @item X @var{len},@var{expr}
35826 @var{len} is the length of the bytecode expression and @var{expr} is the
35827 actual conditional expression in bytecode form.
35831 see @ref{Architecture-Specific Protocol Details}.
35833 @emph{Implementation note: It is possible for a target to copy or move
35834 code that contains memory breakpoints (e.g., when implementing
35835 overlays). The behavior of this packet, in the presence of such a
35836 target, is not defined.}
35848 @item z1,@var{addr},@var{kind}
35849 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
35850 @cindex @samp{z1} packet
35851 @cindex @samp{Z1} packet
35852 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
35853 address @var{addr}.
35855 A hardware breakpoint is implemented using a mechanism that is not
35856 dependant on being able to modify the target's memory. @var{kind}
35857 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
35859 @emph{Implementation note: A hardware breakpoint is not affected by code
35872 @item z2,@var{addr},@var{kind}
35873 @itemx Z2,@var{addr},@var{kind}
35874 @cindex @samp{z2} packet
35875 @cindex @samp{Z2} packet
35876 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
35877 @var{kind} is interpreted as the number of bytes to watch.
35889 @item z3,@var{addr},@var{kind}
35890 @itemx Z3,@var{addr},@var{kind}
35891 @cindex @samp{z3} packet
35892 @cindex @samp{Z3} packet
35893 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
35894 @var{kind} is interpreted as the number of bytes to watch.
35906 @item z4,@var{addr},@var{kind}
35907 @itemx Z4,@var{addr},@var{kind}
35908 @cindex @samp{z4} packet
35909 @cindex @samp{Z4} packet
35910 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
35911 @var{kind} is interpreted as the number of bytes to watch.
35925 @node Stop Reply Packets
35926 @section Stop Reply Packets
35927 @cindex stop reply packets
35929 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
35930 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
35931 receive any of the below as a reply. Except for @samp{?}
35932 and @samp{vStopped}, that reply is only returned
35933 when the target halts. In the below the exact meaning of @dfn{signal
35934 number} is defined by the header @file{include/gdb/signals.h} in the
35935 @value{GDBN} source code.
35937 As in the description of request packets, we include spaces in the
35938 reply templates for clarity; these are not part of the reply packet's
35939 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
35945 The program received signal number @var{AA} (a two-digit hexadecimal
35946 number). This is equivalent to a @samp{T} response with no
35947 @var{n}:@var{r} pairs.
35949 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
35950 @cindex @samp{T} packet reply
35951 The program received signal number @var{AA} (a two-digit hexadecimal
35952 number). This is equivalent to an @samp{S} response, except that the
35953 @samp{@var{n}:@var{r}} pairs can carry values of important registers
35954 and other information directly in the stop reply packet, reducing
35955 round-trip latency. Single-step and breakpoint traps are reported
35956 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
35960 If @var{n} is a hexadecimal number, it is a register number, and the
35961 corresponding @var{r} gives that register's value. @var{r} is a
35962 series of bytes in target byte order, with each byte given by a
35963 two-digit hex number.
35966 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
35967 the stopped thread, as specified in @ref{thread-id syntax}.
35970 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
35971 the core on which the stop event was detected.
35974 If @var{n} is a recognized @dfn{stop reason}, it describes a more
35975 specific event that stopped the target. The currently defined stop
35976 reasons are listed below. @var{aa} should be @samp{05}, the trap
35977 signal. At most one stop reason should be present.
35980 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
35981 and go on to the next; this allows us to extend the protocol in the
35985 The currently defined stop reasons are:
35991 The packet indicates a watchpoint hit, and @var{r} is the data address, in
35994 @cindex shared library events, remote reply
35996 The packet indicates that the loaded libraries have changed.
35997 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
35998 list of loaded libraries. @var{r} is ignored.
36000 @cindex replay log events, remote reply
36002 The packet indicates that the target cannot continue replaying
36003 logged execution events, because it has reached the end (or the
36004 beginning when executing backward) of the log. The value of @var{r}
36005 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
36006 for more information.
36010 @itemx W @var{AA} ; process:@var{pid}
36011 The process exited, and @var{AA} is the exit status. This is only
36012 applicable to certain targets.
36014 The second form of the response, including the process ID of the exited
36015 process, can be used only when @value{GDBN} has reported support for
36016 multiprocess protocol extensions; see @ref{multiprocess extensions}.
36017 The @var{pid} is formatted as a big-endian hex string.
36020 @itemx X @var{AA} ; process:@var{pid}
36021 The process terminated with signal @var{AA}.
36023 The second form of the response, including the process ID of the
36024 terminated process, can be used only when @value{GDBN} has reported
36025 support for multiprocess protocol extensions; see @ref{multiprocess
36026 extensions}. The @var{pid} is formatted as a big-endian hex string.
36028 @item O @var{XX}@dots{}
36029 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
36030 written as the program's console output. This can happen at any time
36031 while the program is running and the debugger should continue to wait
36032 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
36034 @item F @var{call-id},@var{parameter}@dots{}
36035 @var{call-id} is the identifier which says which host system call should
36036 be called. This is just the name of the function. Translation into the
36037 correct system call is only applicable as it's defined in @value{GDBN}.
36038 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
36041 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
36042 this very system call.
36044 The target replies with this packet when it expects @value{GDBN} to
36045 call a host system call on behalf of the target. @value{GDBN} replies
36046 with an appropriate @samp{F} packet and keeps up waiting for the next
36047 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
36048 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
36049 Protocol Extension}, for more details.
36053 @node General Query Packets
36054 @section General Query Packets
36055 @cindex remote query requests
36057 Packets starting with @samp{q} are @dfn{general query packets};
36058 packets starting with @samp{Q} are @dfn{general set packets}. General
36059 query and set packets are a semi-unified form for retrieving and
36060 sending information to and from the stub.
36062 The initial letter of a query or set packet is followed by a name
36063 indicating what sort of thing the packet applies to. For example,
36064 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
36065 definitions with the stub. These packet names follow some
36070 The name must not contain commas, colons or semicolons.
36072 Most @value{GDBN} query and set packets have a leading upper case
36075 The names of custom vendor packets should use a company prefix, in
36076 lower case, followed by a period. For example, packets designed at
36077 the Acme Corporation might begin with @samp{qacme.foo} (for querying
36078 foos) or @samp{Qacme.bar} (for setting bars).
36081 The name of a query or set packet should be separated from any
36082 parameters by a @samp{:}; the parameters themselves should be
36083 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
36084 full packet name, and check for a separator or the end of the packet,
36085 in case two packet names share a common prefix. New packets should not begin
36086 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
36087 packets predate these conventions, and have arguments without any terminator
36088 for the packet name; we suspect they are in widespread use in places that
36089 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
36090 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
36093 Like the descriptions of the other packets, each description here
36094 has a template showing the packet's overall syntax, followed by an
36095 explanation of the packet's meaning. We include spaces in some of the
36096 templates for clarity; these are not part of the packet's syntax. No
36097 @value{GDBN} packet uses spaces to separate its components.
36099 Here are the currently defined query and set packets:
36105 Turn on or off the agent as a helper to perform some debugging operations
36106 delegated from @value{GDBN} (@pxref{Control Agent}).
36108 @item QAllow:@var{op}:@var{val}@dots{}
36109 @cindex @samp{QAllow} packet
36110 Specify which operations @value{GDBN} expects to request of the
36111 target, as a semicolon-separated list of operation name and value
36112 pairs. Possible values for @var{op} include @samp{WriteReg},
36113 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
36114 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
36115 indicating that @value{GDBN} will not request the operation, or 1,
36116 indicating that it may. (The target can then use this to set up its
36117 own internals optimally, for instance if the debugger never expects to
36118 insert breakpoints, it may not need to install its own trap handler.)
36121 @cindex current thread, remote request
36122 @cindex @samp{qC} packet
36123 Return the current thread ID.
36127 @item QC @var{thread-id}
36128 Where @var{thread-id} is a thread ID as documented in
36129 @ref{thread-id syntax}.
36130 @item @r{(anything else)}
36131 Any other reply implies the old thread ID.
36134 @item qCRC:@var{addr},@var{length}
36135 @cindex CRC of memory block, remote request
36136 @cindex @samp{qCRC} packet
36137 Compute the CRC checksum of a block of memory using CRC-32 defined in
36138 IEEE 802.3. The CRC is computed byte at a time, taking the most
36139 significant bit of each byte first. The initial pattern code
36140 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
36142 @emph{Note:} This is the same CRC used in validating separate debug
36143 files (@pxref{Separate Debug Files, , Debugging Information in Separate
36144 Files}). However the algorithm is slightly different. When validating
36145 separate debug files, the CRC is computed taking the @emph{least}
36146 significant bit of each byte first, and the final result is inverted to
36147 detect trailing zeros.
36152 An error (such as memory fault)
36153 @item C @var{crc32}
36154 The specified memory region's checksum is @var{crc32}.
36157 @item QDisableRandomization:@var{value}
36158 @cindex disable address space randomization, remote request
36159 @cindex @samp{QDisableRandomization} packet
36160 Some target operating systems will randomize the virtual address space
36161 of the inferior process as a security feature, but provide a feature
36162 to disable such randomization, e.g.@: to allow for a more deterministic
36163 debugging experience. On such systems, this packet with a @var{value}
36164 of 1 directs the target to disable address space randomization for
36165 processes subsequently started via @samp{vRun} packets, while a packet
36166 with a @var{value} of 0 tells the target to enable address space
36169 This packet is only available in extended mode (@pxref{extended mode}).
36174 The request succeeded.
36177 An error occurred. @var{nn} are hex digits.
36180 An empty reply indicates that @samp{QDisableRandomization} is not supported
36184 This packet is not probed by default; the remote stub must request it,
36185 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36186 This should only be done on targets that actually support disabling
36187 address space randomization.
36190 @itemx qsThreadInfo
36191 @cindex list active threads, remote request
36192 @cindex @samp{qfThreadInfo} packet
36193 @cindex @samp{qsThreadInfo} packet
36194 Obtain a list of all active thread IDs from the target (OS). Since there
36195 may be too many active threads to fit into one reply packet, this query
36196 works iteratively: it may require more than one query/reply sequence to
36197 obtain the entire list of threads. The first query of the sequence will
36198 be the @samp{qfThreadInfo} query; subsequent queries in the
36199 sequence will be the @samp{qsThreadInfo} query.
36201 NOTE: This packet replaces the @samp{qL} query (see below).
36205 @item m @var{thread-id}
36207 @item m @var{thread-id},@var{thread-id}@dots{}
36208 a comma-separated list of thread IDs
36210 (lower case letter @samp{L}) denotes end of list.
36213 In response to each query, the target will reply with a list of one or
36214 more thread IDs, separated by commas.
36215 @value{GDBN} will respond to each reply with a request for more thread
36216 ids (using the @samp{qs} form of the query), until the target responds
36217 with @samp{l} (lower-case ell, for @dfn{last}).
36218 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
36221 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
36222 @cindex get thread-local storage address, remote request
36223 @cindex @samp{qGetTLSAddr} packet
36224 Fetch the address associated with thread local storage specified
36225 by @var{thread-id}, @var{offset}, and @var{lm}.
36227 @var{thread-id} is the thread ID associated with the
36228 thread for which to fetch the TLS address. @xref{thread-id syntax}.
36230 @var{offset} is the (big endian, hex encoded) offset associated with the
36231 thread local variable. (This offset is obtained from the debug
36232 information associated with the variable.)
36234 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
36235 load module associated with the thread local storage. For example,
36236 a @sc{gnu}/Linux system will pass the link map address of the shared
36237 object associated with the thread local storage under consideration.
36238 Other operating environments may choose to represent the load module
36239 differently, so the precise meaning of this parameter will vary.
36243 @item @var{XX}@dots{}
36244 Hex encoded (big endian) bytes representing the address of the thread
36245 local storage requested.
36248 An error occurred. @var{nn} are hex digits.
36251 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
36254 @item qGetTIBAddr:@var{thread-id}
36255 @cindex get thread information block address
36256 @cindex @samp{qGetTIBAddr} packet
36257 Fetch address of the Windows OS specific Thread Information Block.
36259 @var{thread-id} is the thread ID associated with the thread.
36263 @item @var{XX}@dots{}
36264 Hex encoded (big endian) bytes representing the linear address of the
36265 thread information block.
36268 An error occured. This means that either the thread was not found, or the
36269 address could not be retrieved.
36272 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
36275 @item qL @var{startflag} @var{threadcount} @var{nextthread}
36276 Obtain thread information from RTOS. Where: @var{startflag} (one hex
36277 digit) is one to indicate the first query and zero to indicate a
36278 subsequent query; @var{threadcount} (two hex digits) is the maximum
36279 number of threads the response packet can contain; and @var{nextthread}
36280 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
36281 returned in the response as @var{argthread}.
36283 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
36287 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
36288 Where: @var{count} (two hex digits) is the number of threads being
36289 returned; @var{done} (one hex digit) is zero to indicate more threads
36290 and one indicates no further threads; @var{argthreadid} (eight hex
36291 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
36292 is a sequence of thread IDs from the target. @var{threadid} (eight hex
36293 digits). See @code{remote.c:parse_threadlist_response()}.
36297 @cindex section offsets, remote request
36298 @cindex @samp{qOffsets} packet
36299 Get section offsets that the target used when relocating the downloaded
36304 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
36305 Relocate the @code{Text} section by @var{xxx} from its original address.
36306 Relocate the @code{Data} section by @var{yyy} from its original address.
36307 If the object file format provides segment information (e.g.@: @sc{elf}
36308 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
36309 segments by the supplied offsets.
36311 @emph{Note: while a @code{Bss} offset may be included in the response,
36312 @value{GDBN} ignores this and instead applies the @code{Data} offset
36313 to the @code{Bss} section.}
36315 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
36316 Relocate the first segment of the object file, which conventionally
36317 contains program code, to a starting address of @var{xxx}. If
36318 @samp{DataSeg} is specified, relocate the second segment, which
36319 conventionally contains modifiable data, to a starting address of
36320 @var{yyy}. @value{GDBN} will report an error if the object file
36321 does not contain segment information, or does not contain at least
36322 as many segments as mentioned in the reply. Extra segments are
36323 kept at fixed offsets relative to the last relocated segment.
36326 @item qP @var{mode} @var{thread-id}
36327 @cindex thread information, remote request
36328 @cindex @samp{qP} packet
36329 Returns information on @var{thread-id}. Where: @var{mode} is a hex
36330 encoded 32 bit mode; @var{thread-id} is a thread ID
36331 (@pxref{thread-id syntax}).
36333 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
36336 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
36340 @cindex non-stop mode, remote request
36341 @cindex @samp{QNonStop} packet
36343 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
36344 @xref{Remote Non-Stop}, for more information.
36349 The request succeeded.
36352 An error occurred. @var{nn} are hex digits.
36355 An empty reply indicates that @samp{QNonStop} is not supported by
36359 This packet is not probed by default; the remote stub must request it,
36360 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36361 Use of this packet is controlled by the @code{set non-stop} command;
36362 @pxref{Non-Stop Mode}.
36364 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
36365 @cindex pass signals to inferior, remote request
36366 @cindex @samp{QPassSignals} packet
36367 @anchor{QPassSignals}
36368 Each listed @var{signal} should be passed directly to the inferior process.
36369 Signals are numbered identically to continue packets and stop replies
36370 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
36371 strictly greater than the previous item. These signals do not need to stop
36372 the inferior, or be reported to @value{GDBN}. All other signals should be
36373 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
36374 combine; any earlier @samp{QPassSignals} list is completely replaced by the
36375 new list. This packet improves performance when using @samp{handle
36376 @var{signal} nostop noprint pass}.
36381 The request succeeded.
36384 An error occurred. @var{nn} are hex digits.
36387 An empty reply indicates that @samp{QPassSignals} is not supported by
36391 Use of this packet is controlled by the @code{set remote pass-signals}
36392 command (@pxref{Remote Configuration, set remote pass-signals}).
36393 This packet is not probed by default; the remote stub must request it,
36394 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36396 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
36397 @cindex signals the inferior may see, remote request
36398 @cindex @samp{QProgramSignals} packet
36399 @anchor{QProgramSignals}
36400 Each listed @var{signal} may be delivered to the inferior process.
36401 Others should be silently discarded.
36403 In some cases, the remote stub may need to decide whether to deliver a
36404 signal to the program or not without @value{GDBN} involvement. One
36405 example of that is while detaching --- the program's threads may have
36406 stopped for signals that haven't yet had a chance of being reported to
36407 @value{GDBN}, and so the remote stub can use the signal list specified
36408 by this packet to know whether to deliver or ignore those pending
36411 This does not influence whether to deliver a signal as requested by a
36412 resumption packet (@pxref{vCont packet}).
36414 Signals are numbered identically to continue packets and stop replies
36415 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
36416 strictly greater than the previous item. Multiple
36417 @samp{QProgramSignals} packets do not combine; any earlier
36418 @samp{QProgramSignals} list is completely replaced by the new list.
36423 The request succeeded.
36426 An error occurred. @var{nn} are hex digits.
36429 An empty reply indicates that @samp{QProgramSignals} is not supported
36433 Use of this packet is controlled by the @code{set remote program-signals}
36434 command (@pxref{Remote Configuration, set remote program-signals}).
36435 This packet is not probed by default; the remote stub must request it,
36436 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36438 @item qRcmd,@var{command}
36439 @cindex execute remote command, remote request
36440 @cindex @samp{qRcmd} packet
36441 @var{command} (hex encoded) is passed to the local interpreter for
36442 execution. Invalid commands should be reported using the output
36443 string. Before the final result packet, the target may also respond
36444 with a number of intermediate @samp{O@var{output}} console output
36445 packets. @emph{Implementors should note that providing access to a
36446 stubs's interpreter may have security implications}.
36451 A command response with no output.
36453 A command response with the hex encoded output string @var{OUTPUT}.
36455 Indicate a badly formed request.
36457 An empty reply indicates that @samp{qRcmd} is not recognized.
36460 (Note that the @code{qRcmd} packet's name is separated from the
36461 command by a @samp{,}, not a @samp{:}, contrary to the naming
36462 conventions above. Please don't use this packet as a model for new
36465 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
36466 @cindex searching memory, in remote debugging
36467 @cindex @samp{qSearch:memory} packet
36468 @anchor{qSearch memory}
36469 Search @var{length} bytes at @var{address} for @var{search-pattern}.
36470 @var{address} and @var{length} are encoded in hex.
36471 @var{search-pattern} is a sequence of bytes, hex encoded.
36476 The pattern was not found.
36478 The pattern was found at @var{address}.
36480 A badly formed request or an error was encountered while searching memory.
36482 An empty reply indicates that @samp{qSearch:memory} is not recognized.
36485 @item QStartNoAckMode
36486 @cindex @samp{QStartNoAckMode} packet
36487 @anchor{QStartNoAckMode}
36488 Request that the remote stub disable the normal @samp{+}/@samp{-}
36489 protocol acknowledgments (@pxref{Packet Acknowledgment}).
36494 The stub has switched to no-acknowledgment mode.
36495 @value{GDBN} acknowledges this reponse,
36496 but neither the stub nor @value{GDBN} shall send or expect further
36497 @samp{+}/@samp{-} acknowledgments in the current connection.
36499 An empty reply indicates that the stub does not support no-acknowledgment mode.
36502 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
36503 @cindex supported packets, remote query
36504 @cindex features of the remote protocol
36505 @cindex @samp{qSupported} packet
36506 @anchor{qSupported}
36507 Tell the remote stub about features supported by @value{GDBN}, and
36508 query the stub for features it supports. This packet allows
36509 @value{GDBN} and the remote stub to take advantage of each others'
36510 features. @samp{qSupported} also consolidates multiple feature probes
36511 at startup, to improve @value{GDBN} performance---a single larger
36512 packet performs better than multiple smaller probe packets on
36513 high-latency links. Some features may enable behavior which must not
36514 be on by default, e.g.@: because it would confuse older clients or
36515 stubs. Other features may describe packets which could be
36516 automatically probed for, but are not. These features must be
36517 reported before @value{GDBN} will use them. This ``default
36518 unsupported'' behavior is not appropriate for all packets, but it
36519 helps to keep the initial connection time under control with new
36520 versions of @value{GDBN} which support increasing numbers of packets.
36524 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
36525 The stub supports or does not support each returned @var{stubfeature},
36526 depending on the form of each @var{stubfeature} (see below for the
36529 An empty reply indicates that @samp{qSupported} is not recognized,
36530 or that no features needed to be reported to @value{GDBN}.
36533 The allowed forms for each feature (either a @var{gdbfeature} in the
36534 @samp{qSupported} packet, or a @var{stubfeature} in the response)
36538 @item @var{name}=@var{value}
36539 The remote protocol feature @var{name} is supported, and associated
36540 with the specified @var{value}. The format of @var{value} depends
36541 on the feature, but it must not include a semicolon.
36543 The remote protocol feature @var{name} is supported, and does not
36544 need an associated value.
36546 The remote protocol feature @var{name} is not supported.
36548 The remote protocol feature @var{name} may be supported, and
36549 @value{GDBN} should auto-detect support in some other way when it is
36550 needed. This form will not be used for @var{gdbfeature} notifications,
36551 but may be used for @var{stubfeature} responses.
36554 Whenever the stub receives a @samp{qSupported} request, the
36555 supplied set of @value{GDBN} features should override any previous
36556 request. This allows @value{GDBN} to put the stub in a known
36557 state, even if the stub had previously been communicating with
36558 a different version of @value{GDBN}.
36560 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
36565 This feature indicates whether @value{GDBN} supports multiprocess
36566 extensions to the remote protocol. @value{GDBN} does not use such
36567 extensions unless the stub also reports that it supports them by
36568 including @samp{multiprocess+} in its @samp{qSupported} reply.
36569 @xref{multiprocess extensions}, for details.
36572 This feature indicates that @value{GDBN} supports the XML target
36573 description. If the stub sees @samp{xmlRegisters=} with target
36574 specific strings separated by a comma, it will report register
36578 This feature indicates whether @value{GDBN} supports the
36579 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
36580 instruction reply packet}).
36583 Stubs should ignore any unknown values for
36584 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
36585 packet supports receiving packets of unlimited length (earlier
36586 versions of @value{GDBN} may reject overly long responses). Additional values
36587 for @var{gdbfeature} may be defined in the future to let the stub take
36588 advantage of new features in @value{GDBN}, e.g.@: incompatible
36589 improvements in the remote protocol---the @samp{multiprocess} feature is
36590 an example of such a feature. The stub's reply should be independent
36591 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
36592 describes all the features it supports, and then the stub replies with
36593 all the features it supports.
36595 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
36596 responses, as long as each response uses one of the standard forms.
36598 Some features are flags. A stub which supports a flag feature
36599 should respond with a @samp{+} form response. Other features
36600 require values, and the stub should respond with an @samp{=}
36603 Each feature has a default value, which @value{GDBN} will use if
36604 @samp{qSupported} is not available or if the feature is not mentioned
36605 in the @samp{qSupported} response. The default values are fixed; a
36606 stub is free to omit any feature responses that match the defaults.
36608 Not all features can be probed, but for those which can, the probing
36609 mechanism is useful: in some cases, a stub's internal
36610 architecture may not allow the protocol layer to know some information
36611 about the underlying target in advance. This is especially common in
36612 stubs which may be configured for multiple targets.
36614 These are the currently defined stub features and their properties:
36616 @multitable @columnfractions 0.35 0.2 0.12 0.2
36617 @c NOTE: The first row should be @headitem, but we do not yet require
36618 @c a new enough version of Texinfo (4.7) to use @headitem.
36620 @tab Value Required
36624 @item @samp{PacketSize}
36629 @item @samp{qXfer:auxv:read}
36634 @item @samp{qXfer:features:read}
36639 @item @samp{qXfer:libraries:read}
36644 @item @samp{qXfer:memory-map:read}
36649 @item @samp{qXfer:sdata:read}
36654 @item @samp{qXfer:spu:read}
36659 @item @samp{qXfer:spu:write}
36664 @item @samp{qXfer:siginfo:read}
36669 @item @samp{qXfer:siginfo:write}
36674 @item @samp{qXfer:threads:read}
36679 @item @samp{qXfer:traceframe-info:read}
36684 @item @samp{qXfer:uib:read}
36689 @item @samp{qXfer:fdpic:read}
36694 @item @samp{QNonStop}
36699 @item @samp{QPassSignals}
36704 @item @samp{QStartNoAckMode}
36709 @item @samp{multiprocess}
36714 @item @samp{ConditionalBreakpoints}
36719 @item @samp{ConditionalTracepoints}
36724 @item @samp{ReverseContinue}
36729 @item @samp{ReverseStep}
36734 @item @samp{TracepointSource}
36739 @item @samp{QAgent}
36744 @item @samp{QAllow}
36749 @item @samp{QDisableRandomization}
36754 @item @samp{EnableDisableTracepoints}
36759 @item @samp{tracenz}
36764 @item @samp{BreakpointCommands}
36771 These are the currently defined stub features, in more detail:
36774 @cindex packet size, remote protocol
36775 @item PacketSize=@var{bytes}
36776 The remote stub can accept packets up to at least @var{bytes} in
36777 length. @value{GDBN} will send packets up to this size for bulk
36778 transfers, and will never send larger packets. This is a limit on the
36779 data characters in the packet, including the frame and checksum.
36780 There is no trailing NUL byte in a remote protocol packet; if the stub
36781 stores packets in a NUL-terminated format, it should allow an extra
36782 byte in its buffer for the NUL. If this stub feature is not supported,
36783 @value{GDBN} guesses based on the size of the @samp{g} packet response.
36785 @item qXfer:auxv:read
36786 The remote stub understands the @samp{qXfer:auxv:read} packet
36787 (@pxref{qXfer auxiliary vector read}).
36789 @item qXfer:features:read
36790 The remote stub understands the @samp{qXfer:features:read} packet
36791 (@pxref{qXfer target description read}).
36793 @item qXfer:libraries:read
36794 The remote stub understands the @samp{qXfer:libraries:read} packet
36795 (@pxref{qXfer library list read}).
36797 @item qXfer:libraries-svr4:read
36798 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
36799 (@pxref{qXfer svr4 library list read}).
36801 @item qXfer:memory-map:read
36802 The remote stub understands the @samp{qXfer:memory-map:read} packet
36803 (@pxref{qXfer memory map read}).
36805 @item qXfer:sdata:read
36806 The remote stub understands the @samp{qXfer:sdata:read} packet
36807 (@pxref{qXfer sdata read}).
36809 @item qXfer:spu:read
36810 The remote stub understands the @samp{qXfer:spu:read} packet
36811 (@pxref{qXfer spu read}).
36813 @item qXfer:spu:write
36814 The remote stub understands the @samp{qXfer:spu:write} packet
36815 (@pxref{qXfer spu write}).
36817 @item qXfer:siginfo:read
36818 The remote stub understands the @samp{qXfer:siginfo:read} packet
36819 (@pxref{qXfer siginfo read}).
36821 @item qXfer:siginfo:write
36822 The remote stub understands the @samp{qXfer:siginfo:write} packet
36823 (@pxref{qXfer siginfo write}).
36825 @item qXfer:threads:read
36826 The remote stub understands the @samp{qXfer:threads:read} packet
36827 (@pxref{qXfer threads read}).
36829 @item qXfer:traceframe-info:read
36830 The remote stub understands the @samp{qXfer:traceframe-info:read}
36831 packet (@pxref{qXfer traceframe info read}).
36833 @item qXfer:uib:read
36834 The remote stub understands the @samp{qXfer:uib:read}
36835 packet (@pxref{qXfer unwind info block}).
36837 @item qXfer:fdpic:read
36838 The remote stub understands the @samp{qXfer:fdpic:read}
36839 packet (@pxref{qXfer fdpic loadmap read}).
36842 The remote stub understands the @samp{QNonStop} packet
36843 (@pxref{QNonStop}).
36846 The remote stub understands the @samp{QPassSignals} packet
36847 (@pxref{QPassSignals}).
36849 @item QStartNoAckMode
36850 The remote stub understands the @samp{QStartNoAckMode} packet and
36851 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
36854 @anchor{multiprocess extensions}
36855 @cindex multiprocess extensions, in remote protocol
36856 The remote stub understands the multiprocess extensions to the remote
36857 protocol syntax. The multiprocess extensions affect the syntax of
36858 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
36859 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
36860 replies. Note that reporting this feature indicates support for the
36861 syntactic extensions only, not that the stub necessarily supports
36862 debugging of more than one process at a time. The stub must not use
36863 multiprocess extensions in packet replies unless @value{GDBN} has also
36864 indicated it supports them in its @samp{qSupported} request.
36866 @item qXfer:osdata:read
36867 The remote stub understands the @samp{qXfer:osdata:read} packet
36868 ((@pxref{qXfer osdata read}).
36870 @item ConditionalBreakpoints
36871 The target accepts and implements evaluation of conditional expressions
36872 defined for breakpoints. The target will only report breakpoint triggers
36873 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
36875 @item ConditionalTracepoints
36876 The remote stub accepts and implements conditional expressions defined
36877 for tracepoints (@pxref{Tracepoint Conditions}).
36879 @item ReverseContinue
36880 The remote stub accepts and implements the reverse continue packet
36884 The remote stub accepts and implements the reverse step packet
36887 @item TracepointSource
36888 The remote stub understands the @samp{QTDPsrc} packet that supplies
36889 the source form of tracepoint definitions.
36892 The remote stub understands the @samp{QAgent} packet.
36895 The remote stub understands the @samp{QAllow} packet.
36897 @item QDisableRandomization
36898 The remote stub understands the @samp{QDisableRandomization} packet.
36900 @item StaticTracepoint
36901 @cindex static tracepoints, in remote protocol
36902 The remote stub supports static tracepoints.
36904 @item InstallInTrace
36905 @anchor{install tracepoint in tracing}
36906 The remote stub supports installing tracepoint in tracing.
36908 @item EnableDisableTracepoints
36909 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
36910 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
36911 to be enabled and disabled while a trace experiment is running.
36914 @cindex string tracing, in remote protocol
36915 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
36916 See @ref{Bytecode Descriptions} for details about the bytecode.
36918 @item BreakpointCommands
36919 @cindex breakpoint commands, in remote protocol
36920 The remote stub supports running a breakpoint's command list itself,
36921 rather than reporting the hit to @value{GDBN}.
36926 @cindex symbol lookup, remote request
36927 @cindex @samp{qSymbol} packet
36928 Notify the target that @value{GDBN} is prepared to serve symbol lookup
36929 requests. Accept requests from the target for the values of symbols.
36934 The target does not need to look up any (more) symbols.
36935 @item qSymbol:@var{sym_name}
36936 The target requests the value of symbol @var{sym_name} (hex encoded).
36937 @value{GDBN} may provide the value by using the
36938 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
36942 @item qSymbol:@var{sym_value}:@var{sym_name}
36943 Set the value of @var{sym_name} to @var{sym_value}.
36945 @var{sym_name} (hex encoded) is the name of a symbol whose value the
36946 target has previously requested.
36948 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
36949 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
36955 The target does not need to look up any (more) symbols.
36956 @item qSymbol:@var{sym_name}
36957 The target requests the value of a new symbol @var{sym_name} (hex
36958 encoded). @value{GDBN} will continue to supply the values of symbols
36959 (if available), until the target ceases to request them.
36964 @item QTDisconnected
36971 @itemx qTMinFTPILen
36973 @xref{Tracepoint Packets}.
36975 @item qThreadExtraInfo,@var{thread-id}
36976 @cindex thread attributes info, remote request
36977 @cindex @samp{qThreadExtraInfo} packet
36978 Obtain a printable string description of a thread's attributes from
36979 the target OS. @var{thread-id} is a thread ID;
36980 see @ref{thread-id syntax}. This
36981 string may contain anything that the target OS thinks is interesting
36982 for @value{GDBN} to tell the user about the thread. The string is
36983 displayed in @value{GDBN}'s @code{info threads} display. Some
36984 examples of possible thread extra info strings are @samp{Runnable}, or
36985 @samp{Blocked on Mutex}.
36989 @item @var{XX}@dots{}
36990 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
36991 comprising the printable string containing the extra information about
36992 the thread's attributes.
36995 (Note that the @code{qThreadExtraInfo} packet's name is separated from
36996 the command by a @samp{,}, not a @samp{:}, contrary to the naming
36997 conventions above. Please don't use this packet as a model for new
37016 @xref{Tracepoint Packets}.
37018 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
37019 @cindex read special object, remote request
37020 @cindex @samp{qXfer} packet
37021 @anchor{qXfer read}
37022 Read uninterpreted bytes from the target's special data area
37023 identified by the keyword @var{object}. Request @var{length} bytes
37024 starting at @var{offset} bytes into the data. The content and
37025 encoding of @var{annex} is specific to @var{object}; it can supply
37026 additional details about what data to access.
37028 Here are the specific requests of this form defined so far. All
37029 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
37030 formats, listed below.
37033 @item qXfer:auxv:read::@var{offset},@var{length}
37034 @anchor{qXfer auxiliary vector read}
37035 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
37036 auxiliary vector}. Note @var{annex} must be empty.
37038 This packet is not probed by default; the remote stub must request it,
37039 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37041 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
37042 @anchor{qXfer target description read}
37043 Access the @dfn{target description}. @xref{Target Descriptions}. The
37044 annex specifies which XML document to access. The main description is
37045 always loaded from the @samp{target.xml} annex.
37047 This packet is not probed by default; the remote stub must request it,
37048 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37050 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
37051 @anchor{qXfer library list read}
37052 Access the target's list of loaded libraries. @xref{Library List Format}.
37053 The annex part of the generic @samp{qXfer} packet must be empty
37054 (@pxref{qXfer read}).
37056 Targets which maintain a list of libraries in the program's memory do
37057 not need to implement this packet; it is designed for platforms where
37058 the operating system manages the list of loaded libraries.
37060 This packet is not probed by default; the remote stub must request it,
37061 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37063 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
37064 @anchor{qXfer svr4 library list read}
37065 Access the target's list of loaded libraries when the target is an SVR4
37066 platform. @xref{Library List Format for SVR4 Targets}. The annex part
37067 of the generic @samp{qXfer} packet must be empty (@pxref{qXfer read}).
37069 This packet is optional for better performance on SVR4 targets.
37070 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
37072 This packet is not probed by default; the remote stub must request it,
37073 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37075 @item qXfer:memory-map:read::@var{offset},@var{length}
37076 @anchor{qXfer memory map read}
37077 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
37078 annex part of the generic @samp{qXfer} packet must be empty
37079 (@pxref{qXfer read}).
37081 This packet is not probed by default; the remote stub must request it,
37082 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37084 @item qXfer:sdata:read::@var{offset},@var{length}
37085 @anchor{qXfer sdata read}
37087 Read contents of the extra collected static tracepoint marker
37088 information. The annex part of the generic @samp{qXfer} packet must
37089 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
37092 This packet is not probed by default; the remote stub must request it,
37093 by supplying an appropriate @samp{qSupported} response
37094 (@pxref{qSupported}).
37096 @item qXfer:siginfo:read::@var{offset},@var{length}
37097 @anchor{qXfer siginfo read}
37098 Read contents of the extra signal information on the target
37099 system. The annex part of the generic @samp{qXfer} packet must be
37100 empty (@pxref{qXfer read}).
37102 This packet is not probed by default; the remote stub must request it,
37103 by supplying an appropriate @samp{qSupported} response
37104 (@pxref{qSupported}).
37106 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
37107 @anchor{qXfer spu read}
37108 Read contents of an @code{spufs} file on the target system. The
37109 annex specifies which file to read; it must be of the form
37110 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
37111 in the target process, and @var{name} identifes the @code{spufs} file
37112 in that context to be accessed.
37114 This packet is not probed by default; the remote stub must request it,
37115 by supplying an appropriate @samp{qSupported} response
37116 (@pxref{qSupported}).
37118 @item qXfer:threads:read::@var{offset},@var{length}
37119 @anchor{qXfer threads read}
37120 Access the list of threads on target. @xref{Thread List Format}. The
37121 annex part of the generic @samp{qXfer} packet must be empty
37122 (@pxref{qXfer read}).
37124 This packet is not probed by default; the remote stub must request it,
37125 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37127 @item qXfer:traceframe-info:read::@var{offset},@var{length}
37128 @anchor{qXfer traceframe info read}
37130 Return a description of the current traceframe's contents.
37131 @xref{Traceframe Info Format}. The annex part of the generic
37132 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
37134 This packet is not probed by default; the remote stub must request it,
37135 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37137 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
37138 @anchor{qXfer unwind info block}
37140 Return the unwind information block for @var{pc}. This packet is used
37141 on OpenVMS/ia64 to ask the kernel unwind information.
37143 This packet is not probed by default.
37145 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
37146 @anchor{qXfer fdpic loadmap read}
37147 Read contents of @code{loadmap}s on the target system. The
37148 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
37149 executable @code{loadmap} or interpreter @code{loadmap} to read.
37151 This packet is not probed by default; the remote stub must request it,
37152 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37154 @item qXfer:osdata:read::@var{offset},@var{length}
37155 @anchor{qXfer osdata read}
37156 Access the target's @dfn{operating system information}.
37157 @xref{Operating System Information}.
37164 Data @var{data} (@pxref{Binary Data}) has been read from the
37165 target. There may be more data at a higher address (although
37166 it is permitted to return @samp{m} even for the last valid
37167 block of data, as long as at least one byte of data was read).
37168 @var{data} may have fewer bytes than the @var{length} in the
37172 Data @var{data} (@pxref{Binary Data}) has been read from the target.
37173 There is no more data to be read. @var{data} may have fewer bytes
37174 than the @var{length} in the request.
37177 The @var{offset} in the request is at the end of the data.
37178 There is no more data to be read.
37181 The request was malformed, or @var{annex} was invalid.
37184 The offset was invalid, or there was an error encountered reading the data.
37185 @var{nn} is a hex-encoded @code{errno} value.
37188 An empty reply indicates the @var{object} string was not recognized by
37189 the stub, or that the object does not support reading.
37192 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
37193 @cindex write data into object, remote request
37194 @anchor{qXfer write}
37195 Write uninterpreted bytes into the target's special data area
37196 identified by the keyword @var{object}, starting at @var{offset} bytes
37197 into the data. @var{data}@dots{} is the binary-encoded data
37198 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
37199 is specific to @var{object}; it can supply additional details about what data
37202 Here are the specific requests of this form defined so far. All
37203 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
37204 formats, listed below.
37207 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
37208 @anchor{qXfer siginfo write}
37209 Write @var{data} to the extra signal information on the target system.
37210 The annex part of the generic @samp{qXfer} packet must be
37211 empty (@pxref{qXfer write}).
37213 This packet is not probed by default; the remote stub must request it,
37214 by supplying an appropriate @samp{qSupported} response
37215 (@pxref{qSupported}).
37217 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
37218 @anchor{qXfer spu write}
37219 Write @var{data} to an @code{spufs} file on the target system. The
37220 annex specifies which file to write; it must be of the form
37221 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
37222 in the target process, and @var{name} identifes the @code{spufs} file
37223 in that context to be accessed.
37225 This packet is not probed by default; the remote stub must request it,
37226 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37232 @var{nn} (hex encoded) is the number of bytes written.
37233 This may be fewer bytes than supplied in the request.
37236 The request was malformed, or @var{annex} was invalid.
37239 The offset was invalid, or there was an error encountered writing the data.
37240 @var{nn} is a hex-encoded @code{errno} value.
37243 An empty reply indicates the @var{object} string was not
37244 recognized by the stub, or that the object does not support writing.
37247 @item qXfer:@var{object}:@var{operation}:@dots{}
37248 Requests of this form may be added in the future. When a stub does
37249 not recognize the @var{object} keyword, or its support for
37250 @var{object} does not recognize the @var{operation} keyword, the stub
37251 must respond with an empty packet.
37253 @item qAttached:@var{pid}
37254 @cindex query attached, remote request
37255 @cindex @samp{qAttached} packet
37256 Return an indication of whether the remote server attached to an
37257 existing process or created a new process. When the multiprocess
37258 protocol extensions are supported (@pxref{multiprocess extensions}),
37259 @var{pid} is an integer in hexadecimal format identifying the target
37260 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
37261 the query packet will be simplified as @samp{qAttached}.
37263 This query is used, for example, to know whether the remote process
37264 should be detached or killed when a @value{GDBN} session is ended with
37265 the @code{quit} command.
37270 The remote server attached to an existing process.
37272 The remote server created a new process.
37274 A badly formed request or an error was encountered.
37279 @node Architecture-Specific Protocol Details
37280 @section Architecture-Specific Protocol Details
37282 This section describes how the remote protocol is applied to specific
37283 target architectures. Also see @ref{Standard Target Features}, for
37284 details of XML target descriptions for each architecture.
37287 * ARM-Specific Protocol Details::
37288 * MIPS-Specific Protocol Details::
37291 @node ARM-Specific Protocol Details
37292 @subsection @acronym{ARM}-specific Protocol Details
37295 * ARM Breakpoint Kinds::
37298 @node ARM Breakpoint Kinds
37299 @subsubsection @acronym{ARM} Breakpoint Kinds
37300 @cindex breakpoint kinds, @acronym{ARM}
37302 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
37307 16-bit Thumb mode breakpoint.
37310 32-bit Thumb mode (Thumb-2) breakpoint.
37313 32-bit @acronym{ARM} mode breakpoint.
37317 @node MIPS-Specific Protocol Details
37318 @subsection @acronym{MIPS}-specific Protocol Details
37321 * MIPS Register packet Format::
37322 * MIPS Breakpoint Kinds::
37325 @node MIPS Register packet Format
37326 @subsubsection @acronym{MIPS} Register Packet Format
37327 @cindex register packet format, @acronym{MIPS}
37329 The following @code{g}/@code{G} packets have previously been defined.
37330 In the below, some thirty-two bit registers are transferred as
37331 sixty-four bits. Those registers should be zero/sign extended (which?)
37332 to fill the space allocated. Register bytes are transferred in target
37333 byte order. The two nibbles within a register byte are transferred
37334 most-significant -- least-significant.
37339 All registers are transferred as thirty-two bit quantities in the order:
37340 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
37341 registers; fsr; fir; fp.
37344 All registers are transferred as sixty-four bit quantities (including
37345 thirty-two bit registers such as @code{sr}). The ordering is the same
37350 @node MIPS Breakpoint Kinds
37351 @subsubsection @acronym{MIPS} Breakpoint Kinds
37352 @cindex breakpoint kinds, @acronym{MIPS}
37354 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
37359 16-bit @acronym{MIPS16} mode breakpoint.
37362 16-bit @acronym{microMIPS} mode breakpoint.
37365 32-bit standard @acronym{MIPS} mode breakpoint.
37368 32-bit @acronym{microMIPS} mode breakpoint.
37372 @node Tracepoint Packets
37373 @section Tracepoint Packets
37374 @cindex tracepoint packets
37375 @cindex packets, tracepoint
37377 Here we describe the packets @value{GDBN} uses to implement
37378 tracepoints (@pxref{Tracepoints}).
37382 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
37383 @cindex @samp{QTDP} packet
37384 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
37385 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
37386 the tracepoint is disabled. @var{step} is the tracepoint's step
37387 count, and @var{pass} is its pass count. If an @samp{F} is present,
37388 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
37389 the number of bytes that the target should copy elsewhere to make room
37390 for the tracepoint. If an @samp{X} is present, it introduces a
37391 tracepoint condition, which consists of a hexadecimal length, followed
37392 by a comma and hex-encoded bytes, in a manner similar to action
37393 encodings as described below. If the trailing @samp{-} is present,
37394 further @samp{QTDP} packets will follow to specify this tracepoint's
37400 The packet was understood and carried out.
37402 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
37404 The packet was not recognized.
37407 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
37408 Define actions to be taken when a tracepoint is hit. @var{n} and
37409 @var{addr} must be the same as in the initial @samp{QTDP} packet for
37410 this tracepoint. This packet may only be sent immediately after
37411 another @samp{QTDP} packet that ended with a @samp{-}. If the
37412 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
37413 specifying more actions for this tracepoint.
37415 In the series of action packets for a given tracepoint, at most one
37416 can have an @samp{S} before its first @var{action}. If such a packet
37417 is sent, it and the following packets define ``while-stepping''
37418 actions. Any prior packets define ordinary actions --- that is, those
37419 taken when the tracepoint is first hit. If no action packet has an
37420 @samp{S}, then all the packets in the series specify ordinary
37421 tracepoint actions.
37423 The @samp{@var{action}@dots{}} portion of the packet is a series of
37424 actions, concatenated without separators. Each action has one of the
37430 Collect the registers whose bits are set in @var{mask}. @var{mask} is
37431 a hexadecimal number whose @var{i}'th bit is set if register number
37432 @var{i} should be collected. (The least significant bit is numbered
37433 zero.) Note that @var{mask} may be any number of digits long; it may
37434 not fit in a 32-bit word.
37436 @item M @var{basereg},@var{offset},@var{len}
37437 Collect @var{len} bytes of memory starting at the address in register
37438 number @var{basereg}, plus @var{offset}. If @var{basereg} is
37439 @samp{-1}, then the range has a fixed address: @var{offset} is the
37440 address of the lowest byte to collect. The @var{basereg},
37441 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
37442 values (the @samp{-1} value for @var{basereg} is a special case).
37444 @item X @var{len},@var{expr}
37445 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
37446 it directs. @var{expr} is an agent expression, as described in
37447 @ref{Agent Expressions}. Each byte of the expression is encoded as a
37448 two-digit hex number in the packet; @var{len} is the number of bytes
37449 in the expression (and thus one-half the number of hex digits in the
37454 Any number of actions may be packed together in a single @samp{QTDP}
37455 packet, as long as the packet does not exceed the maximum packet
37456 length (400 bytes, for many stubs). There may be only one @samp{R}
37457 action per tracepoint, and it must precede any @samp{M} or @samp{X}
37458 actions. Any registers referred to by @samp{M} and @samp{X} actions
37459 must be collected by a preceding @samp{R} action. (The
37460 ``while-stepping'' actions are treated as if they were attached to a
37461 separate tracepoint, as far as these restrictions are concerned.)
37466 The packet was understood and carried out.
37468 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
37470 The packet was not recognized.
37473 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
37474 @cindex @samp{QTDPsrc} packet
37475 Specify a source string of tracepoint @var{n} at address @var{addr}.
37476 This is useful to get accurate reproduction of the tracepoints
37477 originally downloaded at the beginning of the trace run. @var{type}
37478 is the name of the tracepoint part, such as @samp{cond} for the
37479 tracepoint's conditional expression (see below for a list of types), while
37480 @var{bytes} is the string, encoded in hexadecimal.
37482 @var{start} is the offset of the @var{bytes} within the overall source
37483 string, while @var{slen} is the total length of the source string.
37484 This is intended for handling source strings that are longer than will
37485 fit in a single packet.
37486 @c Add detailed example when this info is moved into a dedicated
37487 @c tracepoint descriptions section.
37489 The available string types are @samp{at} for the location,
37490 @samp{cond} for the conditional, and @samp{cmd} for an action command.
37491 @value{GDBN} sends a separate packet for each command in the action
37492 list, in the same order in which the commands are stored in the list.
37494 The target does not need to do anything with source strings except
37495 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
37498 Although this packet is optional, and @value{GDBN} will only send it
37499 if the target replies with @samp{TracepointSource} @xref{General
37500 Query Packets}, it makes both disconnected tracing and trace files
37501 much easier to use. Otherwise the user must be careful that the
37502 tracepoints in effect while looking at trace frames are identical to
37503 the ones in effect during the trace run; even a small discrepancy
37504 could cause @samp{tdump} not to work, or a particular trace frame not
37507 @item QTDV:@var{n}:@var{value}
37508 @cindex define trace state variable, remote request
37509 @cindex @samp{QTDV} packet
37510 Create a new trace state variable, number @var{n}, with an initial
37511 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
37512 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
37513 the option of not using this packet for initial values of zero; the
37514 target should simply create the trace state variables as they are
37515 mentioned in expressions.
37517 @item QTFrame:@var{n}
37518 @cindex @samp{QTFrame} packet
37519 Select the @var{n}'th tracepoint frame from the buffer, and use the
37520 register and memory contents recorded there to answer subsequent
37521 request packets from @value{GDBN}.
37523 A successful reply from the stub indicates that the stub has found the
37524 requested frame. The response is a series of parts, concatenated
37525 without separators, describing the frame we selected. Each part has
37526 one of the following forms:
37530 The selected frame is number @var{n} in the trace frame buffer;
37531 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
37532 was no frame matching the criteria in the request packet.
37535 The selected trace frame records a hit of tracepoint number @var{t};
37536 @var{t} is a hexadecimal number.
37540 @item QTFrame:pc:@var{addr}
37541 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37542 currently selected frame whose PC is @var{addr};
37543 @var{addr} is a hexadecimal number.
37545 @item QTFrame:tdp:@var{t}
37546 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37547 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
37548 is a hexadecimal number.
37550 @item QTFrame:range:@var{start}:@var{end}
37551 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37552 currently selected frame whose PC is between @var{start} (inclusive)
37553 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
37556 @item QTFrame:outside:@var{start}:@var{end}
37557 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
37558 frame @emph{outside} the given range of addresses (exclusive).
37561 @cindex @samp{qTMinFTPILen} packet
37562 This packet requests the minimum length of instruction at which a fast
37563 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
37564 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
37565 it depends on the target system being able to create trampolines in
37566 the first 64K of memory, which might or might not be possible for that
37567 system. So the reply to this packet will be 4 if it is able to
37574 The minimum instruction length is currently unknown.
37576 The minimum instruction length is @var{length}, where @var{length} is greater
37577 or equal to 1. @var{length} is a hexadecimal number. A reply of 1 means
37578 that a fast tracepoint may be placed on any instruction regardless of size.
37580 An error has occurred.
37582 An empty reply indicates that the request is not supported by the stub.
37586 @cindex @samp{QTStart} packet
37587 Begin the tracepoint experiment. Begin collecting data from
37588 tracepoint hits in the trace frame buffer. This packet supports the
37589 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
37590 instruction reply packet}).
37593 @cindex @samp{QTStop} packet
37594 End the tracepoint experiment. Stop collecting trace frames.
37596 @item QTEnable:@var{n}:@var{addr}
37598 @cindex @samp{QTEnable} packet
37599 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
37600 experiment. If the tracepoint was previously disabled, then collection
37601 of data from it will resume.
37603 @item QTDisable:@var{n}:@var{addr}
37605 @cindex @samp{QTDisable} packet
37606 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
37607 experiment. No more data will be collected from the tracepoint unless
37608 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
37611 @cindex @samp{QTinit} packet
37612 Clear the table of tracepoints, and empty the trace frame buffer.
37614 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
37615 @cindex @samp{QTro} packet
37616 Establish the given ranges of memory as ``transparent''. The stub
37617 will answer requests for these ranges from memory's current contents,
37618 if they were not collected as part of the tracepoint hit.
37620 @value{GDBN} uses this to mark read-only regions of memory, like those
37621 containing program code. Since these areas never change, they should
37622 still have the same contents they did when the tracepoint was hit, so
37623 there's no reason for the stub to refuse to provide their contents.
37625 @item QTDisconnected:@var{value}
37626 @cindex @samp{QTDisconnected} packet
37627 Set the choice to what to do with the tracing run when @value{GDBN}
37628 disconnects from the target. A @var{value} of 1 directs the target to
37629 continue the tracing run, while 0 tells the target to stop tracing if
37630 @value{GDBN} is no longer in the picture.
37633 @cindex @samp{qTStatus} packet
37634 Ask the stub if there is a trace experiment running right now.
37636 The reply has the form:
37640 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
37641 @var{running} is a single digit @code{1} if the trace is presently
37642 running, or @code{0} if not. It is followed by semicolon-separated
37643 optional fields that an agent may use to report additional status.
37647 If the trace is not running, the agent may report any of several
37648 explanations as one of the optional fields:
37653 No trace has been run yet.
37655 @item tstop[:@var{text}]:0
37656 The trace was stopped by a user-originated stop command. The optional
37657 @var{text} field is a user-supplied string supplied as part of the
37658 stop command (for instance, an explanation of why the trace was
37659 stopped manually). It is hex-encoded.
37662 The trace stopped because the trace buffer filled up.
37664 @item tdisconnected:0
37665 The trace stopped because @value{GDBN} disconnected from the target.
37667 @item tpasscount:@var{tpnum}
37668 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
37670 @item terror:@var{text}:@var{tpnum}
37671 The trace stopped because tracepoint @var{tpnum} had an error. The
37672 string @var{text} is available to describe the nature of the error
37673 (for instance, a divide by zero in the condition expression).
37674 @var{text} is hex encoded.
37677 The trace stopped for some other reason.
37681 Additional optional fields supply statistical and other information.
37682 Although not required, they are extremely useful for users monitoring
37683 the progress of a trace run. If a trace has stopped, and these
37684 numbers are reported, they must reflect the state of the just-stopped
37689 @item tframes:@var{n}
37690 The number of trace frames in the buffer.
37692 @item tcreated:@var{n}
37693 The total number of trace frames created during the run. This may
37694 be larger than the trace frame count, if the buffer is circular.
37696 @item tsize:@var{n}
37697 The total size of the trace buffer, in bytes.
37699 @item tfree:@var{n}
37700 The number of bytes still unused in the buffer.
37702 @item circular:@var{n}
37703 The value of the circular trace buffer flag. @code{1} means that the
37704 trace buffer is circular and old trace frames will be discarded if
37705 necessary to make room, @code{0} means that the trace buffer is linear
37708 @item disconn:@var{n}
37709 The value of the disconnected tracing flag. @code{1} means that
37710 tracing will continue after @value{GDBN} disconnects, @code{0} means
37711 that the trace run will stop.
37715 @item qTP:@var{tp}:@var{addr}
37716 @cindex tracepoint status, remote request
37717 @cindex @samp{qTP} packet
37718 Ask the stub for the current state of tracepoint number @var{tp} at
37719 address @var{addr}.
37723 @item V@var{hits}:@var{usage}
37724 The tracepoint has been hit @var{hits} times so far during the trace
37725 run, and accounts for @var{usage} in the trace buffer. Note that
37726 @code{while-stepping} steps are not counted as separate hits, but the
37727 steps' space consumption is added into the usage number.
37731 @item qTV:@var{var}
37732 @cindex trace state variable value, remote request
37733 @cindex @samp{qTV} packet
37734 Ask the stub for the value of the trace state variable number @var{var}.
37739 The value of the variable is @var{value}. This will be the current
37740 value of the variable if the user is examining a running target, or a
37741 saved value if the variable was collected in the trace frame that the
37742 user is looking at. Note that multiple requests may result in
37743 different reply values, such as when requesting values while the
37744 program is running.
37747 The value of the variable is unknown. This would occur, for example,
37748 if the user is examining a trace frame in which the requested variable
37753 @cindex @samp{qTfP} packet
37755 @cindex @samp{qTsP} packet
37756 These packets request data about tracepoints that are being used by
37757 the target. @value{GDBN} sends @code{qTfP} to get the first piece
37758 of data, and multiple @code{qTsP} to get additional pieces. Replies
37759 to these packets generally take the form of the @code{QTDP} packets
37760 that define tracepoints. (FIXME add detailed syntax)
37763 @cindex @samp{qTfV} packet
37765 @cindex @samp{qTsV} packet
37766 These packets request data about trace state variables that are on the
37767 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
37768 and multiple @code{qTsV} to get additional variables. Replies to
37769 these packets follow the syntax of the @code{QTDV} packets that define
37770 trace state variables.
37776 @cindex @samp{qTfSTM} packet
37777 @cindex @samp{qTsSTM} packet
37778 These packets request data about static tracepoint markers that exist
37779 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
37780 first piece of data, and multiple @code{qTsSTM} to get additional
37781 pieces. Replies to these packets take the following form:
37785 @item m @var{address}:@var{id}:@var{extra}
37787 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
37788 a comma-separated list of markers
37790 (lower case letter @samp{L}) denotes end of list.
37792 An error occurred. @var{nn} are hex digits.
37794 An empty reply indicates that the request is not supported by the
37798 @var{address} is encoded in hex.
37799 @var{id} and @var{extra} are strings encoded in hex.
37801 In response to each query, the target will reply with a list of one or
37802 more markers, separated by commas. @value{GDBN} will respond to each
37803 reply with a request for more markers (using the @samp{qs} form of the
37804 query), until the target responds with @samp{l} (lower-case ell, for
37807 @item qTSTMat:@var{address}
37809 @cindex @samp{qTSTMat} packet
37810 This packets requests data about static tracepoint markers in the
37811 target program at @var{address}. Replies to this packet follow the
37812 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
37813 tracepoint markers.
37815 @item QTSave:@var{filename}
37816 @cindex @samp{QTSave} packet
37817 This packet directs the target to save trace data to the file name
37818 @var{filename} in the target's filesystem. @var{filename} is encoded
37819 as a hex string; the interpretation of the file name (relative vs
37820 absolute, wild cards, etc) is up to the target.
37822 @item qTBuffer:@var{offset},@var{len}
37823 @cindex @samp{qTBuffer} packet
37824 Return up to @var{len} bytes of the current contents of trace buffer,
37825 starting at @var{offset}. The trace buffer is treated as if it were
37826 a contiguous collection of traceframes, as per the trace file format.
37827 The reply consists as many hex-encoded bytes as the target can deliver
37828 in a packet; it is not an error to return fewer than were asked for.
37829 A reply consisting of just @code{l} indicates that no bytes are
37832 @item QTBuffer:circular:@var{value}
37833 This packet directs the target to use a circular trace buffer if
37834 @var{value} is 1, or a linear buffer if the value is 0.
37836 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
37837 @cindex @samp{QTNotes} packet
37838 This packet adds optional textual notes to the trace run. Allowable
37839 types include @code{user}, @code{notes}, and @code{tstop}, the
37840 @var{text} fields are arbitrary strings, hex-encoded.
37844 @subsection Relocate instruction reply packet
37845 When installing fast tracepoints in memory, the target may need to
37846 relocate the instruction currently at the tracepoint address to a
37847 different address in memory. For most instructions, a simple copy is
37848 enough, but, for example, call instructions that implicitly push the
37849 return address on the stack, and relative branches or other
37850 PC-relative instructions require offset adjustment, so that the effect
37851 of executing the instruction at a different address is the same as if
37852 it had executed in the original location.
37854 In response to several of the tracepoint packets, the target may also
37855 respond with a number of intermediate @samp{qRelocInsn} request
37856 packets before the final result packet, to have @value{GDBN} handle
37857 this relocation operation. If a packet supports this mechanism, its
37858 documentation will explicitly say so. See for example the above
37859 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
37860 format of the request is:
37863 @item qRelocInsn:@var{from};@var{to}
37865 This requests @value{GDBN} to copy instruction at address @var{from}
37866 to address @var{to}, possibly adjusted so that executing the
37867 instruction at @var{to} has the same effect as executing it at
37868 @var{from}. @value{GDBN} writes the adjusted instruction to target
37869 memory starting at @var{to}.
37874 @item qRelocInsn:@var{adjusted_size}
37875 Informs the stub the relocation is complete. @var{adjusted_size} is
37876 the length in bytes of resulting relocated instruction sequence.
37878 A badly formed request was detected, or an error was encountered while
37879 relocating the instruction.
37882 @node Host I/O Packets
37883 @section Host I/O Packets
37884 @cindex Host I/O, remote protocol
37885 @cindex file transfer, remote protocol
37887 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
37888 operations on the far side of a remote link. For example, Host I/O is
37889 used to upload and download files to a remote target with its own
37890 filesystem. Host I/O uses the same constant values and data structure
37891 layout as the target-initiated File-I/O protocol. However, the
37892 Host I/O packets are structured differently. The target-initiated
37893 protocol relies on target memory to store parameters and buffers.
37894 Host I/O requests are initiated by @value{GDBN}, and the
37895 target's memory is not involved. @xref{File-I/O Remote Protocol
37896 Extension}, for more details on the target-initiated protocol.
37898 The Host I/O request packets all encode a single operation along with
37899 its arguments. They have this format:
37903 @item vFile:@var{operation}: @var{parameter}@dots{}
37904 @var{operation} is the name of the particular request; the target
37905 should compare the entire packet name up to the second colon when checking
37906 for a supported operation. The format of @var{parameter} depends on
37907 the operation. Numbers are always passed in hexadecimal. Negative
37908 numbers have an explicit minus sign (i.e.@: two's complement is not
37909 used). Strings (e.g.@: filenames) are encoded as a series of
37910 hexadecimal bytes. The last argument to a system call may be a
37911 buffer of escaped binary data (@pxref{Binary Data}).
37915 The valid responses to Host I/O packets are:
37919 @item F @var{result} [, @var{errno}] [; @var{attachment}]
37920 @var{result} is the integer value returned by this operation, usually
37921 non-negative for success and -1 for errors. If an error has occured,
37922 @var{errno} will be included in the result. @var{errno} will have a
37923 value defined by the File-I/O protocol (@pxref{Errno Values}). For
37924 operations which return data, @var{attachment} supplies the data as a
37925 binary buffer. Binary buffers in response packets are escaped in the
37926 normal way (@pxref{Binary Data}). See the individual packet
37927 documentation for the interpretation of @var{result} and
37931 An empty response indicates that this operation is not recognized.
37935 These are the supported Host I/O operations:
37938 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
37939 Open a file at @var{pathname} and return a file descriptor for it, or
37940 return -1 if an error occurs. @var{pathname} is a string,
37941 @var{flags} is an integer indicating a mask of open flags
37942 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
37943 of mode bits to use if the file is created (@pxref{mode_t Values}).
37944 @xref{open}, for details of the open flags and mode values.
37946 @item vFile:close: @var{fd}
37947 Close the open file corresponding to @var{fd} and return 0, or
37948 -1 if an error occurs.
37950 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
37951 Read data from the open file corresponding to @var{fd}. Up to
37952 @var{count} bytes will be read from the file, starting at @var{offset}
37953 relative to the start of the file. The target may read fewer bytes;
37954 common reasons include packet size limits and an end-of-file
37955 condition. The number of bytes read is returned. Zero should only be
37956 returned for a successful read at the end of the file, or if
37957 @var{count} was zero.
37959 The data read should be returned as a binary attachment on success.
37960 If zero bytes were read, the response should include an empty binary
37961 attachment (i.e.@: a trailing semicolon). The return value is the
37962 number of target bytes read; the binary attachment may be longer if
37963 some characters were escaped.
37965 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
37966 Write @var{data} (a binary buffer) to the open file corresponding
37967 to @var{fd}. Start the write at @var{offset} from the start of the
37968 file. Unlike many @code{write} system calls, there is no
37969 separate @var{count} argument; the length of @var{data} in the
37970 packet is used. @samp{vFile:write} returns the number of bytes written,
37971 which may be shorter than the length of @var{data}, or -1 if an
37974 @item vFile:unlink: @var{pathname}
37975 Delete the file at @var{pathname} on the target. Return 0,
37976 or -1 if an error occurs. @var{pathname} is a string.
37978 @item vFile:readlink: @var{filename}
37979 Read value of symbolic link @var{filename} on the target. Return
37980 the number of bytes read, or -1 if an error occurs.
37982 The data read should be returned as a binary attachment on success.
37983 If zero bytes were read, the response should include an empty binary
37984 attachment (i.e.@: a trailing semicolon). The return value is the
37985 number of target bytes read; the binary attachment may be longer if
37986 some characters were escaped.
37991 @section Interrupts
37992 @cindex interrupts (remote protocol)
37994 When a program on the remote target is running, @value{GDBN} may
37995 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
37996 a @code{BREAK} followed by @code{g},
37997 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
37999 The precise meaning of @code{BREAK} is defined by the transport
38000 mechanism and may, in fact, be undefined. @value{GDBN} does not
38001 currently define a @code{BREAK} mechanism for any of the network
38002 interfaces except for TCP, in which case @value{GDBN} sends the
38003 @code{telnet} BREAK sequence.
38005 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
38006 transport mechanisms. It is represented by sending the single byte
38007 @code{0x03} without any of the usual packet overhead described in
38008 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
38009 transmitted as part of a packet, it is considered to be packet data
38010 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
38011 (@pxref{X packet}), used for binary downloads, may include an unescaped
38012 @code{0x03} as part of its packet.
38014 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
38015 When Linux kernel receives this sequence from serial port,
38016 it stops execution and connects to gdb.
38018 Stubs are not required to recognize these interrupt mechanisms and the
38019 precise meaning associated with receipt of the interrupt is
38020 implementation defined. If the target supports debugging of multiple
38021 threads and/or processes, it should attempt to interrupt all
38022 currently-executing threads and processes.
38023 If the stub is successful at interrupting the
38024 running program, it should send one of the stop
38025 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
38026 of successfully stopping the program in all-stop mode, and a stop reply
38027 for each stopped thread in non-stop mode.
38028 Interrupts received while the
38029 program is stopped are discarded.
38031 @node Notification Packets
38032 @section Notification Packets
38033 @cindex notification packets
38034 @cindex packets, notification
38036 The @value{GDBN} remote serial protocol includes @dfn{notifications},
38037 packets that require no acknowledgment. Both the GDB and the stub
38038 may send notifications (although the only notifications defined at
38039 present are sent by the stub). Notifications carry information
38040 without incurring the round-trip latency of an acknowledgment, and so
38041 are useful for low-impact communications where occasional packet loss
38044 A notification packet has the form @samp{% @var{data} #
38045 @var{checksum}}, where @var{data} is the content of the notification,
38046 and @var{checksum} is a checksum of @var{data}, computed and formatted
38047 as for ordinary @value{GDBN} packets. A notification's @var{data}
38048 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
38049 receiving a notification, the recipient sends no @samp{+} or @samp{-}
38050 to acknowledge the notification's receipt or to report its corruption.
38052 Every notification's @var{data} begins with a name, which contains no
38053 colon characters, followed by a colon character.
38055 Recipients should silently ignore corrupted notifications and
38056 notifications they do not understand. Recipients should restart
38057 timeout periods on receipt of a well-formed notification, whether or
38058 not they understand it.
38060 Senders should only send the notifications described here when this
38061 protocol description specifies that they are permitted. In the
38062 future, we may extend the protocol to permit existing notifications in
38063 new contexts; this rule helps older senders avoid confusing newer
38066 (Older versions of @value{GDBN} ignore bytes received until they see
38067 the @samp{$} byte that begins an ordinary packet, so new stubs may
38068 transmit notifications without fear of confusing older clients. There
38069 are no notifications defined for @value{GDBN} to send at the moment, but we
38070 assume that most older stubs would ignore them, as well.)
38072 The following notification packets from the stub to @value{GDBN} are
38076 @item Stop: @var{reply}
38077 Report an asynchronous stop event in non-stop mode.
38078 The @var{reply} has the form of a stop reply, as
38079 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
38080 for information on how these notifications are acknowledged by
38084 @node Remote Non-Stop
38085 @section Remote Protocol Support for Non-Stop Mode
38087 @value{GDBN}'s remote protocol supports non-stop debugging of
38088 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
38089 supports non-stop mode, it should report that to @value{GDBN} by including
38090 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
38092 @value{GDBN} typically sends a @samp{QNonStop} packet only when
38093 establishing a new connection with the stub. Entering non-stop mode
38094 does not alter the state of any currently-running threads, but targets
38095 must stop all threads in any already-attached processes when entering
38096 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
38097 probe the target state after a mode change.
38099 In non-stop mode, when an attached process encounters an event that
38100 would otherwise be reported with a stop reply, it uses the
38101 asynchronous notification mechanism (@pxref{Notification Packets}) to
38102 inform @value{GDBN}. In contrast to all-stop mode, where all threads
38103 in all processes are stopped when a stop reply is sent, in non-stop
38104 mode only the thread reporting the stop event is stopped. That is,
38105 when reporting a @samp{S} or @samp{T} response to indicate completion
38106 of a step operation, hitting a breakpoint, or a fault, only the
38107 affected thread is stopped; any other still-running threads continue
38108 to run. When reporting a @samp{W} or @samp{X} response, all running
38109 threads belonging to other attached processes continue to run.
38111 Only one stop reply notification at a time may be pending; if
38112 additional stop events occur before @value{GDBN} has acknowledged the
38113 previous notification, they must be queued by the stub for later
38114 synchronous transmission in response to @samp{vStopped} packets from
38115 @value{GDBN}. Because the notification mechanism is unreliable,
38116 the stub is permitted to resend a stop reply notification
38117 if it believes @value{GDBN} may not have received it. @value{GDBN}
38118 ignores additional stop reply notifications received before it has
38119 finished processing a previous notification and the stub has completed
38120 sending any queued stop events.
38122 Otherwise, @value{GDBN} must be prepared to receive a stop reply
38123 notification at any time. Specifically, they may appear when
38124 @value{GDBN} is not otherwise reading input from the stub, or when
38125 @value{GDBN} is expecting to read a normal synchronous response or a
38126 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
38127 Notification packets are distinct from any other communication from
38128 the stub so there is no ambiguity.
38130 After receiving a stop reply notification, @value{GDBN} shall
38131 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
38132 as a regular, synchronous request to the stub. Such acknowledgment
38133 is not required to happen immediately, as @value{GDBN} is permitted to
38134 send other, unrelated packets to the stub first, which the stub should
38137 Upon receiving a @samp{vStopped} packet, if the stub has other queued
38138 stop events to report to @value{GDBN}, it shall respond by sending a
38139 normal stop reply response. @value{GDBN} shall then send another
38140 @samp{vStopped} packet to solicit further responses; again, it is
38141 permitted to send other, unrelated packets as well which the stub
38142 should process normally.
38144 If the stub receives a @samp{vStopped} packet and there are no
38145 additional stop events to report, the stub shall return an @samp{OK}
38146 response. At this point, if further stop events occur, the stub shall
38147 send a new stop reply notification, @value{GDBN} shall accept the
38148 notification, and the process shall be repeated.
38150 In non-stop mode, the target shall respond to the @samp{?} packet as
38151 follows. First, any incomplete stop reply notification/@samp{vStopped}
38152 sequence in progress is abandoned. The target must begin a new
38153 sequence reporting stop events for all stopped threads, whether or not
38154 it has previously reported those events to @value{GDBN}. The first
38155 stop reply is sent as a synchronous reply to the @samp{?} packet, and
38156 subsequent stop replies are sent as responses to @samp{vStopped} packets
38157 using the mechanism described above. The target must not send
38158 asynchronous stop reply notifications until the sequence is complete.
38159 If all threads are running when the target receives the @samp{?} packet,
38160 or if the target is not attached to any process, it shall respond
38163 @node Packet Acknowledgment
38164 @section Packet Acknowledgment
38166 @cindex acknowledgment, for @value{GDBN} remote
38167 @cindex packet acknowledgment, for @value{GDBN} remote
38168 By default, when either the host or the target machine receives a packet,
38169 the first response expected is an acknowledgment: either @samp{+} (to indicate
38170 the package was received correctly) or @samp{-} (to request retransmission).
38171 This mechanism allows the @value{GDBN} remote protocol to operate over
38172 unreliable transport mechanisms, such as a serial line.
38174 In cases where the transport mechanism is itself reliable (such as a pipe or
38175 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
38176 It may be desirable to disable them in that case to reduce communication
38177 overhead, or for other reasons. This can be accomplished by means of the
38178 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
38180 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
38181 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
38182 and response format still includes the normal checksum, as described in
38183 @ref{Overview}, but the checksum may be ignored by the receiver.
38185 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
38186 no-acknowledgment mode, it should report that to @value{GDBN}
38187 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
38188 @pxref{qSupported}.
38189 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
38190 disabled via the @code{set remote noack-packet off} command
38191 (@pxref{Remote Configuration}),
38192 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
38193 Only then may the stub actually turn off packet acknowledgments.
38194 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
38195 response, which can be safely ignored by the stub.
38197 Note that @code{set remote noack-packet} command only affects negotiation
38198 between @value{GDBN} and the stub when subsequent connections are made;
38199 it does not affect the protocol acknowledgment state for any current
38201 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
38202 new connection is established,
38203 there is also no protocol request to re-enable the acknowledgments
38204 for the current connection, once disabled.
38209 Example sequence of a target being re-started. Notice how the restart
38210 does not get any direct output:
38215 @emph{target restarts}
38218 <- @code{T001:1234123412341234}
38222 Example sequence of a target being stepped by a single instruction:
38225 -> @code{G1445@dots{}}
38230 <- @code{T001:1234123412341234}
38234 <- @code{1455@dots{}}
38238 @node File-I/O Remote Protocol Extension
38239 @section File-I/O Remote Protocol Extension
38240 @cindex File-I/O remote protocol extension
38243 * File-I/O Overview::
38244 * Protocol Basics::
38245 * The F Request Packet::
38246 * The F Reply Packet::
38247 * The Ctrl-C Message::
38249 * List of Supported Calls::
38250 * Protocol-specific Representation of Datatypes::
38252 * File-I/O Examples::
38255 @node File-I/O Overview
38256 @subsection File-I/O Overview
38257 @cindex file-i/o overview
38259 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
38260 target to use the host's file system and console I/O to perform various
38261 system calls. System calls on the target system are translated into a
38262 remote protocol packet to the host system, which then performs the needed
38263 actions and returns a response packet to the target system.
38264 This simulates file system operations even on targets that lack file systems.
38266 The protocol is defined to be independent of both the host and target systems.
38267 It uses its own internal representation of datatypes and values. Both
38268 @value{GDBN} and the target's @value{GDBN} stub are responsible for
38269 translating the system-dependent value representations into the internal
38270 protocol representations when data is transmitted.
38272 The communication is synchronous. A system call is possible only when
38273 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
38274 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
38275 the target is stopped to allow deterministic access to the target's
38276 memory. Therefore File-I/O is not interruptible by target signals. On
38277 the other hand, it is possible to interrupt File-I/O by a user interrupt
38278 (@samp{Ctrl-C}) within @value{GDBN}.
38280 The target's request to perform a host system call does not finish
38281 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
38282 after finishing the system call, the target returns to continuing the
38283 previous activity (continue, step). No additional continue or step
38284 request from @value{GDBN} is required.
38287 (@value{GDBP}) continue
38288 <- target requests 'system call X'
38289 target is stopped, @value{GDBN} executes system call
38290 -> @value{GDBN} returns result
38291 ... target continues, @value{GDBN} returns to wait for the target
38292 <- target hits breakpoint and sends a Txx packet
38295 The protocol only supports I/O on the console and to regular files on
38296 the host file system. Character or block special devices, pipes,
38297 named pipes, sockets or any other communication method on the host
38298 system are not supported by this protocol.
38300 File I/O is not supported in non-stop mode.
38302 @node Protocol Basics
38303 @subsection Protocol Basics
38304 @cindex protocol basics, file-i/o
38306 The File-I/O protocol uses the @code{F} packet as the request as well
38307 as reply packet. Since a File-I/O system call can only occur when
38308 @value{GDBN} is waiting for a response from the continuing or stepping target,
38309 the File-I/O request is a reply that @value{GDBN} has to expect as a result
38310 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
38311 This @code{F} packet contains all information needed to allow @value{GDBN}
38312 to call the appropriate host system call:
38316 A unique identifier for the requested system call.
38319 All parameters to the system call. Pointers are given as addresses
38320 in the target memory address space. Pointers to strings are given as
38321 pointer/length pair. Numerical values are given as they are.
38322 Numerical control flags are given in a protocol-specific representation.
38326 At this point, @value{GDBN} has to perform the following actions.
38330 If the parameters include pointer values to data needed as input to a
38331 system call, @value{GDBN} requests this data from the target with a
38332 standard @code{m} packet request. This additional communication has to be
38333 expected by the target implementation and is handled as any other @code{m}
38337 @value{GDBN} translates all value from protocol representation to host
38338 representation as needed. Datatypes are coerced into the host types.
38341 @value{GDBN} calls the system call.
38344 It then coerces datatypes back to protocol representation.
38347 If the system call is expected to return data in buffer space specified
38348 by pointer parameters to the call, the data is transmitted to the
38349 target using a @code{M} or @code{X} packet. This packet has to be expected
38350 by the target implementation and is handled as any other @code{M} or @code{X}
38355 Eventually @value{GDBN} replies with another @code{F} packet which contains all
38356 necessary information for the target to continue. This at least contains
38363 @code{errno}, if has been changed by the system call.
38370 After having done the needed type and value coercion, the target continues
38371 the latest continue or step action.
38373 @node The F Request Packet
38374 @subsection The @code{F} Request Packet
38375 @cindex file-i/o request packet
38376 @cindex @code{F} request packet
38378 The @code{F} request packet has the following format:
38381 @item F@var{call-id},@var{parameter@dots{}}
38383 @var{call-id} is the identifier to indicate the host system call to be called.
38384 This is just the name of the function.
38386 @var{parameter@dots{}} are the parameters to the system call.
38387 Parameters are hexadecimal integer values, either the actual values in case
38388 of scalar datatypes, pointers to target buffer space in case of compound
38389 datatypes and unspecified memory areas, or pointer/length pairs in case
38390 of string parameters. These are appended to the @var{call-id} as a
38391 comma-delimited list. All values are transmitted in ASCII
38392 string representation, pointer/length pairs separated by a slash.
38398 @node The F Reply Packet
38399 @subsection The @code{F} Reply Packet
38400 @cindex file-i/o reply packet
38401 @cindex @code{F} reply packet
38403 The @code{F} reply packet has the following format:
38407 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
38409 @var{retcode} is the return code of the system call as hexadecimal value.
38411 @var{errno} is the @code{errno} set by the call, in protocol-specific
38413 This parameter can be omitted if the call was successful.
38415 @var{Ctrl-C flag} is only sent if the user requested a break. In this
38416 case, @var{errno} must be sent as well, even if the call was successful.
38417 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
38424 or, if the call was interrupted before the host call has been performed:
38431 assuming 4 is the protocol-specific representation of @code{EINTR}.
38436 @node The Ctrl-C Message
38437 @subsection The @samp{Ctrl-C} Message
38438 @cindex ctrl-c message, in file-i/o protocol
38440 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
38441 reply packet (@pxref{The F Reply Packet}),
38442 the target should behave as if it had
38443 gotten a break message. The meaning for the target is ``system call
38444 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
38445 (as with a break message) and return to @value{GDBN} with a @code{T02}
38448 It's important for the target to know in which
38449 state the system call was interrupted. There are two possible cases:
38453 The system call hasn't been performed on the host yet.
38456 The system call on the host has been finished.
38460 These two states can be distinguished by the target by the value of the
38461 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
38462 call hasn't been performed. This is equivalent to the @code{EINTR} handling
38463 on POSIX systems. In any other case, the target may presume that the
38464 system call has been finished --- successfully or not --- and should behave
38465 as if the break message arrived right after the system call.
38467 @value{GDBN} must behave reliably. If the system call has not been called
38468 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
38469 @code{errno} in the packet. If the system call on the host has been finished
38470 before the user requests a break, the full action must be finished by
38471 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
38472 The @code{F} packet may only be sent when either nothing has happened
38473 or the full action has been completed.
38476 @subsection Console I/O
38477 @cindex console i/o as part of file-i/o
38479 By default and if not explicitly closed by the target system, the file
38480 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
38481 on the @value{GDBN} console is handled as any other file output operation
38482 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
38483 by @value{GDBN} so that after the target read request from file descriptor
38484 0 all following typing is buffered until either one of the following
38489 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
38491 system call is treated as finished.
38494 The user presses @key{RET}. This is treated as end of input with a trailing
38498 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
38499 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
38503 If the user has typed more characters than fit in the buffer given to
38504 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
38505 either another @code{read(0, @dots{})} is requested by the target, or debugging
38506 is stopped at the user's request.
38509 @node List of Supported Calls
38510 @subsection List of Supported Calls
38511 @cindex list of supported file-i/o calls
38528 @unnumberedsubsubsec open
38529 @cindex open, file-i/o system call
38534 int open(const char *pathname, int flags);
38535 int open(const char *pathname, int flags, mode_t mode);
38539 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
38542 @var{flags} is the bitwise @code{OR} of the following values:
38546 If the file does not exist it will be created. The host
38547 rules apply as far as file ownership and time stamps
38551 When used with @code{O_CREAT}, if the file already exists it is
38552 an error and open() fails.
38555 If the file already exists and the open mode allows
38556 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
38557 truncated to zero length.
38560 The file is opened in append mode.
38563 The file is opened for reading only.
38566 The file is opened for writing only.
38569 The file is opened for reading and writing.
38573 Other bits are silently ignored.
38577 @var{mode} is the bitwise @code{OR} of the following values:
38581 User has read permission.
38584 User has write permission.
38587 Group has read permission.
38590 Group has write permission.
38593 Others have read permission.
38596 Others have write permission.
38600 Other bits are silently ignored.
38603 @item Return value:
38604 @code{open} returns the new file descriptor or -1 if an error
38611 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
38614 @var{pathname} refers to a directory.
38617 The requested access is not allowed.
38620 @var{pathname} was too long.
38623 A directory component in @var{pathname} does not exist.
38626 @var{pathname} refers to a device, pipe, named pipe or socket.
38629 @var{pathname} refers to a file on a read-only filesystem and
38630 write access was requested.
38633 @var{pathname} is an invalid pointer value.
38636 No space on device to create the file.
38639 The process already has the maximum number of files open.
38642 The limit on the total number of files open on the system
38646 The call was interrupted by the user.
38652 @unnumberedsubsubsec close
38653 @cindex close, file-i/o system call
38662 @samp{Fclose,@var{fd}}
38664 @item Return value:
38665 @code{close} returns zero on success, or -1 if an error occurred.
38671 @var{fd} isn't a valid open file descriptor.
38674 The call was interrupted by the user.
38680 @unnumberedsubsubsec read
38681 @cindex read, file-i/o system call
38686 int read(int fd, void *buf, unsigned int count);
38690 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
38692 @item Return value:
38693 On success, the number of bytes read is returned.
38694 Zero indicates end of file. If count is zero, read
38695 returns zero as well. On error, -1 is returned.
38701 @var{fd} is not a valid file descriptor or is not open for
38705 @var{bufptr} is an invalid pointer value.
38708 The call was interrupted by the user.
38714 @unnumberedsubsubsec write
38715 @cindex write, file-i/o system call
38720 int write(int fd, const void *buf, unsigned int count);
38724 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
38726 @item Return value:
38727 On success, the number of bytes written are returned.
38728 Zero indicates nothing was written. On error, -1
38735 @var{fd} is not a valid file descriptor or is not open for
38739 @var{bufptr} is an invalid pointer value.
38742 An attempt was made to write a file that exceeds the
38743 host-specific maximum file size allowed.
38746 No space on device to write the data.
38749 The call was interrupted by the user.
38755 @unnumberedsubsubsec lseek
38756 @cindex lseek, file-i/o system call
38761 long lseek (int fd, long offset, int flag);
38765 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
38767 @var{flag} is one of:
38771 The offset is set to @var{offset} bytes.
38774 The offset is set to its current location plus @var{offset}
38778 The offset is set to the size of the file plus @var{offset}
38782 @item Return value:
38783 On success, the resulting unsigned offset in bytes from
38784 the beginning of the file is returned. Otherwise, a
38785 value of -1 is returned.
38791 @var{fd} is not a valid open file descriptor.
38794 @var{fd} is associated with the @value{GDBN} console.
38797 @var{flag} is not a proper value.
38800 The call was interrupted by the user.
38806 @unnumberedsubsubsec rename
38807 @cindex rename, file-i/o system call
38812 int rename(const char *oldpath, const char *newpath);
38816 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
38818 @item Return value:
38819 On success, zero is returned. On error, -1 is returned.
38825 @var{newpath} is an existing directory, but @var{oldpath} is not a
38829 @var{newpath} is a non-empty directory.
38832 @var{oldpath} or @var{newpath} is a directory that is in use by some
38836 An attempt was made to make a directory a subdirectory
38840 A component used as a directory in @var{oldpath} or new
38841 path is not a directory. Or @var{oldpath} is a directory
38842 and @var{newpath} exists but is not a directory.
38845 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
38848 No access to the file or the path of the file.
38852 @var{oldpath} or @var{newpath} was too long.
38855 A directory component in @var{oldpath} or @var{newpath} does not exist.
38858 The file is on a read-only filesystem.
38861 The device containing the file has no room for the new
38865 The call was interrupted by the user.
38871 @unnumberedsubsubsec unlink
38872 @cindex unlink, file-i/o system call
38877 int unlink(const char *pathname);
38881 @samp{Funlink,@var{pathnameptr}/@var{len}}
38883 @item Return value:
38884 On success, zero is returned. On error, -1 is returned.
38890 No access to the file or the path of the file.
38893 The system does not allow unlinking of directories.
38896 The file @var{pathname} cannot be unlinked because it's
38897 being used by another process.
38900 @var{pathnameptr} is an invalid pointer value.
38903 @var{pathname} was too long.
38906 A directory component in @var{pathname} does not exist.
38909 A component of the path is not a directory.
38912 The file is on a read-only filesystem.
38915 The call was interrupted by the user.
38921 @unnumberedsubsubsec stat/fstat
38922 @cindex fstat, file-i/o system call
38923 @cindex stat, file-i/o system call
38928 int stat(const char *pathname, struct stat *buf);
38929 int fstat(int fd, struct stat *buf);
38933 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
38934 @samp{Ffstat,@var{fd},@var{bufptr}}
38936 @item Return value:
38937 On success, zero is returned. On error, -1 is returned.
38943 @var{fd} is not a valid open file.
38946 A directory component in @var{pathname} does not exist or the
38947 path is an empty string.
38950 A component of the path is not a directory.
38953 @var{pathnameptr} is an invalid pointer value.
38956 No access to the file or the path of the file.
38959 @var{pathname} was too long.
38962 The call was interrupted by the user.
38968 @unnumberedsubsubsec gettimeofday
38969 @cindex gettimeofday, file-i/o system call
38974 int gettimeofday(struct timeval *tv, void *tz);
38978 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
38980 @item Return value:
38981 On success, 0 is returned, -1 otherwise.
38987 @var{tz} is a non-NULL pointer.
38990 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
38996 @unnumberedsubsubsec isatty
38997 @cindex isatty, file-i/o system call
39002 int isatty(int fd);
39006 @samp{Fisatty,@var{fd}}
39008 @item Return value:
39009 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
39015 The call was interrupted by the user.
39020 Note that the @code{isatty} call is treated as a special case: it returns
39021 1 to the target if the file descriptor is attached
39022 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
39023 would require implementing @code{ioctl} and would be more complex than
39028 @unnumberedsubsubsec system
39029 @cindex system, file-i/o system call
39034 int system(const char *command);
39038 @samp{Fsystem,@var{commandptr}/@var{len}}
39040 @item Return value:
39041 If @var{len} is zero, the return value indicates whether a shell is
39042 available. A zero return value indicates a shell is not available.
39043 For non-zero @var{len}, the value returned is -1 on error and the
39044 return status of the command otherwise. Only the exit status of the
39045 command is returned, which is extracted from the host's @code{system}
39046 return value by calling @code{WEXITSTATUS(retval)}. In case
39047 @file{/bin/sh} could not be executed, 127 is returned.
39053 The call was interrupted by the user.
39058 @value{GDBN} takes over the full task of calling the necessary host calls
39059 to perform the @code{system} call. The return value of @code{system} on
39060 the host is simplified before it's returned
39061 to the target. Any termination signal information from the child process
39062 is discarded, and the return value consists
39063 entirely of the exit status of the called command.
39065 Due to security concerns, the @code{system} call is by default refused
39066 by @value{GDBN}. The user has to allow this call explicitly with the
39067 @code{set remote system-call-allowed 1} command.
39070 @item set remote system-call-allowed
39071 @kindex set remote system-call-allowed
39072 Control whether to allow the @code{system} calls in the File I/O
39073 protocol for the remote target. The default is zero (disabled).
39075 @item show remote system-call-allowed
39076 @kindex show remote system-call-allowed
39077 Show whether the @code{system} calls are allowed in the File I/O
39081 @node Protocol-specific Representation of Datatypes
39082 @subsection Protocol-specific Representation of Datatypes
39083 @cindex protocol-specific representation of datatypes, in file-i/o protocol
39086 * Integral Datatypes::
39088 * Memory Transfer::
39093 @node Integral Datatypes
39094 @unnumberedsubsubsec Integral Datatypes
39095 @cindex integral datatypes, in file-i/o protocol
39097 The integral datatypes used in the system calls are @code{int},
39098 @code{unsigned int}, @code{long}, @code{unsigned long},
39099 @code{mode_t}, and @code{time_t}.
39101 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
39102 implemented as 32 bit values in this protocol.
39104 @code{long} and @code{unsigned long} are implemented as 64 bit types.
39106 @xref{Limits}, for corresponding MIN and MAX values (similar to those
39107 in @file{limits.h}) to allow range checking on host and target.
39109 @code{time_t} datatypes are defined as seconds since the Epoch.
39111 All integral datatypes transferred as part of a memory read or write of a
39112 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
39115 @node Pointer Values
39116 @unnumberedsubsubsec Pointer Values
39117 @cindex pointer values, in file-i/o protocol
39119 Pointers to target data are transmitted as they are. An exception
39120 is made for pointers to buffers for which the length isn't
39121 transmitted as part of the function call, namely strings. Strings
39122 are transmitted as a pointer/length pair, both as hex values, e.g.@:
39129 which is a pointer to data of length 18 bytes at position 0x1aaf.
39130 The length is defined as the full string length in bytes, including
39131 the trailing null byte. For example, the string @code{"hello world"}
39132 at address 0x123456 is transmitted as
39138 @node Memory Transfer
39139 @unnumberedsubsubsec Memory Transfer
39140 @cindex memory transfer, in file-i/o protocol
39142 Structured data which is transferred using a memory read or write (for
39143 example, a @code{struct stat}) is expected to be in a protocol-specific format
39144 with all scalar multibyte datatypes being big endian. Translation to
39145 this representation needs to be done both by the target before the @code{F}
39146 packet is sent, and by @value{GDBN} before
39147 it transfers memory to the target. Transferred pointers to structured
39148 data should point to the already-coerced data at any time.
39152 @unnumberedsubsubsec struct stat
39153 @cindex struct stat, in file-i/o protocol
39155 The buffer of type @code{struct stat} used by the target and @value{GDBN}
39156 is defined as follows:
39160 unsigned int st_dev; /* device */
39161 unsigned int st_ino; /* inode */
39162 mode_t st_mode; /* protection */
39163 unsigned int st_nlink; /* number of hard links */
39164 unsigned int st_uid; /* user ID of owner */
39165 unsigned int st_gid; /* group ID of owner */
39166 unsigned int st_rdev; /* device type (if inode device) */
39167 unsigned long st_size; /* total size, in bytes */
39168 unsigned long st_blksize; /* blocksize for filesystem I/O */
39169 unsigned long st_blocks; /* number of blocks allocated */
39170 time_t st_atime; /* time of last access */
39171 time_t st_mtime; /* time of last modification */
39172 time_t st_ctime; /* time of last change */
39176 The integral datatypes conform to the definitions given in the
39177 appropriate section (see @ref{Integral Datatypes}, for details) so this
39178 structure is of size 64 bytes.
39180 The values of several fields have a restricted meaning and/or
39186 A value of 0 represents a file, 1 the console.
39189 No valid meaning for the target. Transmitted unchanged.
39192 Valid mode bits are described in @ref{Constants}. Any other
39193 bits have currently no meaning for the target.
39198 No valid meaning for the target. Transmitted unchanged.
39203 These values have a host and file system dependent
39204 accuracy. Especially on Windows hosts, the file system may not
39205 support exact timing values.
39208 The target gets a @code{struct stat} of the above representation and is
39209 responsible for coercing it to the target representation before
39212 Note that due to size differences between the host, target, and protocol
39213 representations of @code{struct stat} members, these members could eventually
39214 get truncated on the target.
39216 @node struct timeval
39217 @unnumberedsubsubsec struct timeval
39218 @cindex struct timeval, in file-i/o protocol
39220 The buffer of type @code{struct timeval} used by the File-I/O protocol
39221 is defined as follows:
39225 time_t tv_sec; /* second */
39226 long tv_usec; /* microsecond */
39230 The integral datatypes conform to the definitions given in the
39231 appropriate section (see @ref{Integral Datatypes}, for details) so this
39232 structure is of size 8 bytes.
39235 @subsection Constants
39236 @cindex constants, in file-i/o protocol
39238 The following values are used for the constants inside of the
39239 protocol. @value{GDBN} and target are responsible for translating these
39240 values before and after the call as needed.
39251 @unnumberedsubsubsec Open Flags
39252 @cindex open flags, in file-i/o protocol
39254 All values are given in hexadecimal representation.
39266 @node mode_t Values
39267 @unnumberedsubsubsec mode_t Values
39268 @cindex mode_t values, in file-i/o protocol
39270 All values are given in octal representation.
39287 @unnumberedsubsubsec Errno Values
39288 @cindex errno values, in file-i/o protocol
39290 All values are given in decimal representation.
39315 @code{EUNKNOWN} is used as a fallback error value if a host system returns
39316 any error value not in the list of supported error numbers.
39319 @unnumberedsubsubsec Lseek Flags
39320 @cindex lseek flags, in file-i/o protocol
39329 @unnumberedsubsubsec Limits
39330 @cindex limits, in file-i/o protocol
39332 All values are given in decimal representation.
39335 INT_MIN -2147483648
39337 UINT_MAX 4294967295
39338 LONG_MIN -9223372036854775808
39339 LONG_MAX 9223372036854775807
39340 ULONG_MAX 18446744073709551615
39343 @node File-I/O Examples
39344 @subsection File-I/O Examples
39345 @cindex file-i/o examples
39347 Example sequence of a write call, file descriptor 3, buffer is at target
39348 address 0x1234, 6 bytes should be written:
39351 <- @code{Fwrite,3,1234,6}
39352 @emph{request memory read from target}
39355 @emph{return "6 bytes written"}
39359 Example sequence of a read call, file descriptor 3, buffer is at target
39360 address 0x1234, 6 bytes should be read:
39363 <- @code{Fread,3,1234,6}
39364 @emph{request memory write to target}
39365 -> @code{X1234,6:XXXXXX}
39366 @emph{return "6 bytes read"}
39370 Example sequence of a read call, call fails on the host due to invalid
39371 file descriptor (@code{EBADF}):
39374 <- @code{Fread,3,1234,6}
39378 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
39382 <- @code{Fread,3,1234,6}
39387 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
39391 <- @code{Fread,3,1234,6}
39392 -> @code{X1234,6:XXXXXX}
39396 @node Library List Format
39397 @section Library List Format
39398 @cindex library list format, remote protocol
39400 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
39401 same process as your application to manage libraries. In this case,
39402 @value{GDBN} can use the loader's symbol table and normal memory
39403 operations to maintain a list of shared libraries. On other
39404 platforms, the operating system manages loaded libraries.
39405 @value{GDBN} can not retrieve the list of currently loaded libraries
39406 through memory operations, so it uses the @samp{qXfer:libraries:read}
39407 packet (@pxref{qXfer library list read}) instead. The remote stub
39408 queries the target's operating system and reports which libraries
39411 The @samp{qXfer:libraries:read} packet returns an XML document which
39412 lists loaded libraries and their offsets. Each library has an
39413 associated name and one or more segment or section base addresses,
39414 which report where the library was loaded in memory.
39416 For the common case of libraries that are fully linked binaries, the
39417 library should have a list of segments. If the target supports
39418 dynamic linking of a relocatable object file, its library XML element
39419 should instead include a list of allocated sections. The segment or
39420 section bases are start addresses, not relocation offsets; they do not
39421 depend on the library's link-time base addresses.
39423 @value{GDBN} must be linked with the Expat library to support XML
39424 library lists. @xref{Expat}.
39426 A simple memory map, with one loaded library relocated by a single
39427 offset, looks like this:
39431 <library name="/lib/libc.so.6">
39432 <segment address="0x10000000"/>
39437 Another simple memory map, with one loaded library with three
39438 allocated sections (.text, .data, .bss), looks like this:
39442 <library name="sharedlib.o">
39443 <section address="0x10000000"/>
39444 <section address="0x20000000"/>
39445 <section address="0x30000000"/>
39450 The format of a library list is described by this DTD:
39453 <!-- library-list: Root element with versioning -->
39454 <!ELEMENT library-list (library)*>
39455 <!ATTLIST library-list version CDATA #FIXED "1.0">
39456 <!ELEMENT library (segment*, section*)>
39457 <!ATTLIST library name CDATA #REQUIRED>
39458 <!ELEMENT segment EMPTY>
39459 <!ATTLIST segment address CDATA #REQUIRED>
39460 <!ELEMENT section EMPTY>
39461 <!ATTLIST section address CDATA #REQUIRED>
39464 In addition, segments and section descriptors cannot be mixed within a
39465 single library element, and you must supply at least one segment or
39466 section for each library.
39468 @node Library List Format for SVR4 Targets
39469 @section Library List Format for SVR4 Targets
39470 @cindex library list format, remote protocol
39472 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
39473 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
39474 shared libraries. Still a special library list provided by this packet is
39475 more efficient for the @value{GDBN} remote protocol.
39477 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
39478 loaded libraries and their SVR4 linker parameters. For each library on SVR4
39479 target, the following parameters are reported:
39483 @code{name}, the absolute file name from the @code{l_name} field of
39484 @code{struct link_map}.
39486 @code{lm} with address of @code{struct link_map} used for TLS
39487 (Thread Local Storage) access.
39489 @code{l_addr}, the displacement as read from the field @code{l_addr} of
39490 @code{struct link_map}. For prelinked libraries this is not an absolute
39491 memory address. It is a displacement of absolute memory address against
39492 address the file was prelinked to during the library load.
39494 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
39497 Additionally the single @code{main-lm} attribute specifies address of
39498 @code{struct link_map} used for the main executable. This parameter is used
39499 for TLS access and its presence is optional.
39501 @value{GDBN} must be linked with the Expat library to support XML
39502 SVR4 library lists. @xref{Expat}.
39504 A simple memory map, with two loaded libraries (which do not use prelink),
39508 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
39509 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
39511 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
39513 </library-list-svr>
39516 The format of an SVR4 library list is described by this DTD:
39519 <!-- library-list-svr4: Root element with versioning -->
39520 <!ELEMENT library-list-svr4 (library)*>
39521 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
39522 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
39523 <!ELEMENT library EMPTY>
39524 <!ATTLIST library name CDATA #REQUIRED>
39525 <!ATTLIST library lm CDATA #REQUIRED>
39526 <!ATTLIST library l_addr CDATA #REQUIRED>
39527 <!ATTLIST library l_ld CDATA #REQUIRED>
39530 @node Memory Map Format
39531 @section Memory Map Format
39532 @cindex memory map format
39534 To be able to write into flash memory, @value{GDBN} needs to obtain a
39535 memory map from the target. This section describes the format of the
39538 The memory map is obtained using the @samp{qXfer:memory-map:read}
39539 (@pxref{qXfer memory map read}) packet and is an XML document that
39540 lists memory regions.
39542 @value{GDBN} must be linked with the Expat library to support XML
39543 memory maps. @xref{Expat}.
39545 The top-level structure of the document is shown below:
39548 <?xml version="1.0"?>
39549 <!DOCTYPE memory-map
39550 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
39551 "http://sourceware.org/gdb/gdb-memory-map.dtd">
39557 Each region can be either:
39562 A region of RAM starting at @var{addr} and extending for @var{length}
39566 <memory type="ram" start="@var{addr}" length="@var{length}"/>
39571 A region of read-only memory:
39574 <memory type="rom" start="@var{addr}" length="@var{length}"/>
39579 A region of flash memory, with erasure blocks @var{blocksize}
39583 <memory type="flash" start="@var{addr}" length="@var{length}">
39584 <property name="blocksize">@var{blocksize}</property>
39590 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
39591 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
39592 packets to write to addresses in such ranges.
39594 The formal DTD for memory map format is given below:
39597 <!-- ................................................... -->
39598 <!-- Memory Map XML DTD ................................ -->
39599 <!-- File: memory-map.dtd .............................. -->
39600 <!-- .................................... .............. -->
39601 <!-- memory-map.dtd -->
39602 <!-- memory-map: Root element with versioning -->
39603 <!ELEMENT memory-map (memory | property)>
39604 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
39605 <!ELEMENT memory (property)>
39606 <!-- memory: Specifies a memory region,
39607 and its type, or device. -->
39608 <!ATTLIST memory type CDATA #REQUIRED
39609 start CDATA #REQUIRED
39610 length CDATA #REQUIRED
39611 device CDATA #IMPLIED>
39612 <!-- property: Generic attribute tag -->
39613 <!ELEMENT property (#PCDATA | property)*>
39614 <!ATTLIST property name CDATA #REQUIRED>
39617 @node Thread List Format
39618 @section Thread List Format
39619 @cindex thread list format
39621 To efficiently update the list of threads and their attributes,
39622 @value{GDBN} issues the @samp{qXfer:threads:read} packet
39623 (@pxref{qXfer threads read}) and obtains the XML document with
39624 the following structure:
39627 <?xml version="1.0"?>
39629 <thread id="id" core="0">
39630 ... description ...
39635 Each @samp{thread} element must have the @samp{id} attribute that
39636 identifies the thread (@pxref{thread-id syntax}). The
39637 @samp{core} attribute, if present, specifies which processor core
39638 the thread was last executing on. The content of the of @samp{thread}
39639 element is interpreted as human-readable auxilliary information.
39641 @node Traceframe Info Format
39642 @section Traceframe Info Format
39643 @cindex traceframe info format
39645 To be able to know which objects in the inferior can be examined when
39646 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
39647 memory ranges, registers and trace state variables that have been
39648 collected in a traceframe.
39650 This list is obtained using the @samp{qXfer:traceframe-info:read}
39651 (@pxref{qXfer traceframe info read}) packet and is an XML document.
39653 @value{GDBN} must be linked with the Expat library to support XML
39654 traceframe info discovery. @xref{Expat}.
39656 The top-level structure of the document is shown below:
39659 <?xml version="1.0"?>
39660 <!DOCTYPE traceframe-info
39661 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
39662 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
39668 Each traceframe block can be either:
39673 A region of collected memory starting at @var{addr} and extending for
39674 @var{length} bytes from there:
39677 <memory start="@var{addr}" length="@var{length}"/>
39682 The formal DTD for the traceframe info format is given below:
39685 <!ELEMENT traceframe-info (memory)* >
39686 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
39688 <!ELEMENT memory EMPTY>
39689 <!ATTLIST memory start CDATA #REQUIRED
39690 length CDATA #REQUIRED>
39693 @include agentexpr.texi
39695 @node Target Descriptions
39696 @appendix Target Descriptions
39697 @cindex target descriptions
39699 One of the challenges of using @value{GDBN} to debug embedded systems
39700 is that there are so many minor variants of each processor
39701 architecture in use. It is common practice for vendors to start with
39702 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
39703 and then make changes to adapt it to a particular market niche. Some
39704 architectures have hundreds of variants, available from dozens of
39705 vendors. This leads to a number of problems:
39709 With so many different customized processors, it is difficult for
39710 the @value{GDBN} maintainers to keep up with the changes.
39712 Since individual variants may have short lifetimes or limited
39713 audiences, it may not be worthwhile to carry information about every
39714 variant in the @value{GDBN} source tree.
39716 When @value{GDBN} does support the architecture of the embedded system
39717 at hand, the task of finding the correct architecture name to give the
39718 @command{set architecture} command can be error-prone.
39721 To address these problems, the @value{GDBN} remote protocol allows a
39722 target system to not only identify itself to @value{GDBN}, but to
39723 actually describe its own features. This lets @value{GDBN} support
39724 processor variants it has never seen before --- to the extent that the
39725 descriptions are accurate, and that @value{GDBN} understands them.
39727 @value{GDBN} must be linked with the Expat library to support XML
39728 target descriptions. @xref{Expat}.
39731 * Retrieving Descriptions:: How descriptions are fetched from a target.
39732 * Target Description Format:: The contents of a target description.
39733 * Predefined Target Types:: Standard types available for target
39735 * Standard Target Features:: Features @value{GDBN} knows about.
39738 @node Retrieving Descriptions
39739 @section Retrieving Descriptions
39741 Target descriptions can be read from the target automatically, or
39742 specified by the user manually. The default behavior is to read the
39743 description from the target. @value{GDBN} retrieves it via the remote
39744 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
39745 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
39746 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
39747 XML document, of the form described in @ref{Target Description
39750 Alternatively, you can specify a file to read for the target description.
39751 If a file is set, the target will not be queried. The commands to
39752 specify a file are:
39755 @cindex set tdesc filename
39756 @item set tdesc filename @var{path}
39757 Read the target description from @var{path}.
39759 @cindex unset tdesc filename
39760 @item unset tdesc filename
39761 Do not read the XML target description from a file. @value{GDBN}
39762 will use the description supplied by the current target.
39764 @cindex show tdesc filename
39765 @item show tdesc filename
39766 Show the filename to read for a target description, if any.
39770 @node Target Description Format
39771 @section Target Description Format
39772 @cindex target descriptions, XML format
39774 A target description annex is an @uref{http://www.w3.org/XML/, XML}
39775 document which complies with the Document Type Definition provided in
39776 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
39777 means you can use generally available tools like @command{xmllint} to
39778 check that your feature descriptions are well-formed and valid.
39779 However, to help people unfamiliar with XML write descriptions for
39780 their targets, we also describe the grammar here.
39782 Target descriptions can identify the architecture of the remote target
39783 and (for some architectures) provide information about custom register
39784 sets. They can also identify the OS ABI of the remote target.
39785 @value{GDBN} can use this information to autoconfigure for your
39786 target, or to warn you if you connect to an unsupported target.
39788 Here is a simple target description:
39791 <target version="1.0">
39792 <architecture>i386:x86-64</architecture>
39797 This minimal description only says that the target uses
39798 the x86-64 architecture.
39800 A target description has the following overall form, with [ ] marking
39801 optional elements and @dots{} marking repeatable elements. The elements
39802 are explained further below.
39805 <?xml version="1.0"?>
39806 <!DOCTYPE target SYSTEM "gdb-target.dtd">
39807 <target version="1.0">
39808 @r{[}@var{architecture}@r{]}
39809 @r{[}@var{osabi}@r{]}
39810 @r{[}@var{compatible}@r{]}
39811 @r{[}@var{feature}@dots{}@r{]}
39816 The description is generally insensitive to whitespace and line
39817 breaks, under the usual common-sense rules. The XML version
39818 declaration and document type declaration can generally be omitted
39819 (@value{GDBN} does not require them), but specifying them may be
39820 useful for XML validation tools. The @samp{version} attribute for
39821 @samp{<target>} may also be omitted, but we recommend
39822 including it; if future versions of @value{GDBN} use an incompatible
39823 revision of @file{gdb-target.dtd}, they will detect and report
39824 the version mismatch.
39826 @subsection Inclusion
39827 @cindex target descriptions, inclusion
39830 @cindex <xi:include>
39833 It can sometimes be valuable to split a target description up into
39834 several different annexes, either for organizational purposes, or to
39835 share files between different possible target descriptions. You can
39836 divide a description into multiple files by replacing any element of
39837 the target description with an inclusion directive of the form:
39840 <xi:include href="@var{document}"/>
39844 When @value{GDBN} encounters an element of this form, it will retrieve
39845 the named XML @var{document}, and replace the inclusion directive with
39846 the contents of that document. If the current description was read
39847 using @samp{qXfer}, then so will be the included document;
39848 @var{document} will be interpreted as the name of an annex. If the
39849 current description was read from a file, @value{GDBN} will look for
39850 @var{document} as a file in the same directory where it found the
39851 original description.
39853 @subsection Architecture
39854 @cindex <architecture>
39856 An @samp{<architecture>} element has this form:
39859 <architecture>@var{arch}</architecture>
39862 @var{arch} is one of the architectures from the set accepted by
39863 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
39866 @cindex @code{<osabi>}
39868 This optional field was introduced in @value{GDBN} version 7.0.
39869 Previous versions of @value{GDBN} ignore it.
39871 An @samp{<osabi>} element has this form:
39874 <osabi>@var{abi-name}</osabi>
39877 @var{abi-name} is an OS ABI name from the same selection accepted by
39878 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
39880 @subsection Compatible Architecture
39881 @cindex @code{<compatible>}
39883 This optional field was introduced in @value{GDBN} version 7.0.
39884 Previous versions of @value{GDBN} ignore it.
39886 A @samp{<compatible>} element has this form:
39889 <compatible>@var{arch}</compatible>
39892 @var{arch} is one of the architectures from the set accepted by
39893 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
39895 A @samp{<compatible>} element is used to specify that the target
39896 is able to run binaries in some other than the main target architecture
39897 given by the @samp{<architecture>} element. For example, on the
39898 Cell Broadband Engine, the main architecture is @code{powerpc:common}
39899 or @code{powerpc:common64}, but the system is able to run binaries
39900 in the @code{spu} architecture as well. The way to describe this
39901 capability with @samp{<compatible>} is as follows:
39904 <architecture>powerpc:common</architecture>
39905 <compatible>spu</compatible>
39908 @subsection Features
39911 Each @samp{<feature>} describes some logical portion of the target
39912 system. Features are currently used to describe available CPU
39913 registers and the types of their contents. A @samp{<feature>} element
39917 <feature name="@var{name}">
39918 @r{[}@var{type}@dots{}@r{]}
39924 Each feature's name should be unique within the description. The name
39925 of a feature does not matter unless @value{GDBN} has some special
39926 knowledge of the contents of that feature; if it does, the feature
39927 should have its standard name. @xref{Standard Target Features}.
39931 Any register's value is a collection of bits which @value{GDBN} must
39932 interpret. The default interpretation is a two's complement integer,
39933 but other types can be requested by name in the register description.
39934 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
39935 Target Types}), and the description can define additional composite types.
39937 Each type element must have an @samp{id} attribute, which gives
39938 a unique (within the containing @samp{<feature>}) name to the type.
39939 Types must be defined before they are used.
39942 Some targets offer vector registers, which can be treated as arrays
39943 of scalar elements. These types are written as @samp{<vector>} elements,
39944 specifying the array element type, @var{type}, and the number of elements,
39948 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
39952 If a register's value is usefully viewed in multiple ways, define it
39953 with a union type containing the useful representations. The
39954 @samp{<union>} element contains one or more @samp{<field>} elements,
39955 each of which has a @var{name} and a @var{type}:
39958 <union id="@var{id}">
39959 <field name="@var{name}" type="@var{type}"/>
39965 If a register's value is composed from several separate values, define
39966 it with a structure type. There are two forms of the @samp{<struct>}
39967 element; a @samp{<struct>} element must either contain only bitfields
39968 or contain no bitfields. If the structure contains only bitfields,
39969 its total size in bytes must be specified, each bitfield must have an
39970 explicit start and end, and bitfields are automatically assigned an
39971 integer type. The field's @var{start} should be less than or
39972 equal to its @var{end}, and zero represents the least significant bit.
39975 <struct id="@var{id}" size="@var{size}">
39976 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
39981 If the structure contains no bitfields, then each field has an
39982 explicit type, and no implicit padding is added.
39985 <struct id="@var{id}">
39986 <field name="@var{name}" type="@var{type}"/>
39992 If a register's value is a series of single-bit flags, define it with
39993 a flags type. The @samp{<flags>} element has an explicit @var{size}
39994 and contains one or more @samp{<field>} elements. Each field has a
39995 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
39999 <flags id="@var{id}" size="@var{size}">
40000 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
40005 @subsection Registers
40008 Each register is represented as an element with this form:
40011 <reg name="@var{name}"
40012 bitsize="@var{size}"
40013 @r{[}regnum="@var{num}"@r{]}
40014 @r{[}save-restore="@var{save-restore}"@r{]}
40015 @r{[}type="@var{type}"@r{]}
40016 @r{[}group="@var{group}"@r{]}/>
40020 The components are as follows:
40025 The register's name; it must be unique within the target description.
40028 The register's size, in bits.
40031 The register's number. If omitted, a register's number is one greater
40032 than that of the previous register (either in the current feature or in
40033 a preceding feature); the first register in the target description
40034 defaults to zero. This register number is used to read or write
40035 the register; e.g.@: it is used in the remote @code{p} and @code{P}
40036 packets, and registers appear in the @code{g} and @code{G} packets
40037 in order of increasing register number.
40040 Whether the register should be preserved across inferior function
40041 calls; this must be either @code{yes} or @code{no}. The default is
40042 @code{yes}, which is appropriate for most registers except for
40043 some system control registers; this is not related to the target's
40047 The type of the register. @var{type} may be a predefined type, a type
40048 defined in the current feature, or one of the special types @code{int}
40049 and @code{float}. @code{int} is an integer type of the correct size
40050 for @var{bitsize}, and @code{float} is a floating point type (in the
40051 architecture's normal floating point format) of the correct size for
40052 @var{bitsize}. The default is @code{int}.
40055 The register group to which this register belongs. @var{group} must
40056 be either @code{general}, @code{float}, or @code{vector}. If no
40057 @var{group} is specified, @value{GDBN} will not display the register
40058 in @code{info registers}.
40062 @node Predefined Target Types
40063 @section Predefined Target Types
40064 @cindex target descriptions, predefined types
40066 Type definitions in the self-description can build up composite types
40067 from basic building blocks, but can not define fundamental types. Instead,
40068 standard identifiers are provided by @value{GDBN} for the fundamental
40069 types. The currently supported types are:
40078 Signed integer types holding the specified number of bits.
40085 Unsigned integer types holding the specified number of bits.
40089 Pointers to unspecified code and data. The program counter and
40090 any dedicated return address register may be marked as code
40091 pointers; printing a code pointer converts it into a symbolic
40092 address. The stack pointer and any dedicated address registers
40093 may be marked as data pointers.
40096 Single precision IEEE floating point.
40099 Double precision IEEE floating point.
40102 The 12-byte extended precision format used by ARM FPA registers.
40105 The 10-byte extended precision format used by x87 registers.
40108 32bit @sc{eflags} register used by x86.
40111 32bit @sc{mxcsr} register used by x86.
40115 @node Standard Target Features
40116 @section Standard Target Features
40117 @cindex target descriptions, standard features
40119 A target description must contain either no registers or all the
40120 target's registers. If the description contains no registers, then
40121 @value{GDBN} will assume a default register layout, selected based on
40122 the architecture. If the description contains any registers, the
40123 default layout will not be used; the standard registers must be
40124 described in the target description, in such a way that @value{GDBN}
40125 can recognize them.
40127 This is accomplished by giving specific names to feature elements
40128 which contain standard registers. @value{GDBN} will look for features
40129 with those names and verify that they contain the expected registers;
40130 if any known feature is missing required registers, or if any required
40131 feature is missing, @value{GDBN} will reject the target
40132 description. You can add additional registers to any of the
40133 standard features --- @value{GDBN} will display them just as if
40134 they were added to an unrecognized feature.
40136 This section lists the known features and their expected contents.
40137 Sample XML documents for these features are included in the
40138 @value{GDBN} source tree, in the directory @file{gdb/features}.
40140 Names recognized by @value{GDBN} should include the name of the
40141 company or organization which selected the name, and the overall
40142 architecture to which the feature applies; so e.g.@: the feature
40143 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
40145 The names of registers are not case sensitive for the purpose
40146 of recognizing standard features, but @value{GDBN} will only display
40147 registers using the capitalization used in the description.
40154 * PowerPC Features::
40160 @subsection ARM Features
40161 @cindex target descriptions, ARM features
40163 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
40165 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
40166 @samp{lr}, @samp{pc}, and @samp{cpsr}.
40168 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
40169 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
40170 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
40173 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
40174 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
40176 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
40177 it should contain at least registers @samp{wR0} through @samp{wR15} and
40178 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
40179 @samp{wCSSF}, and @samp{wCASF} registers are optional.
40181 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
40182 should contain at least registers @samp{d0} through @samp{d15}. If
40183 they are present, @samp{d16} through @samp{d31} should also be included.
40184 @value{GDBN} will synthesize the single-precision registers from
40185 halves of the double-precision registers.
40187 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
40188 need to contain registers; it instructs @value{GDBN} to display the
40189 VFP double-precision registers as vectors and to synthesize the
40190 quad-precision registers from pairs of double-precision registers.
40191 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
40192 be present and include 32 double-precision registers.
40194 @node i386 Features
40195 @subsection i386 Features
40196 @cindex target descriptions, i386 features
40198 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
40199 targets. It should describe the following registers:
40203 @samp{eax} through @samp{edi} plus @samp{eip} for i386
40205 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
40207 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
40208 @samp{fs}, @samp{gs}
40210 @samp{st0} through @samp{st7}
40212 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
40213 @samp{foseg}, @samp{fooff} and @samp{fop}
40216 The register sets may be different, depending on the target.
40218 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
40219 describe registers:
40223 @samp{xmm0} through @samp{xmm7} for i386
40225 @samp{xmm0} through @samp{xmm15} for amd64
40230 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
40231 @samp{org.gnu.gdb.i386.sse} feature. It should
40232 describe the upper 128 bits of @sc{ymm} registers:
40236 @samp{ymm0h} through @samp{ymm7h} for i386
40238 @samp{ymm0h} through @samp{ymm15h} for amd64
40241 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
40242 describe a single register, @samp{orig_eax}.
40244 @node MIPS Features
40245 @subsection @acronym{MIPS} Features
40246 @cindex target descriptions, @acronym{MIPS} features
40248 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
40249 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
40250 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
40253 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
40254 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
40255 registers. They may be 32-bit or 64-bit depending on the target.
40257 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
40258 it may be optional in a future version of @value{GDBN}. It should
40259 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
40260 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
40262 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
40263 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
40264 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
40265 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
40267 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
40268 contain a single register, @samp{restart}, which is used by the
40269 Linux kernel to control restartable syscalls.
40271 @node M68K Features
40272 @subsection M68K Features
40273 @cindex target descriptions, M68K features
40276 @item @samp{org.gnu.gdb.m68k.core}
40277 @itemx @samp{org.gnu.gdb.coldfire.core}
40278 @itemx @samp{org.gnu.gdb.fido.core}
40279 One of those features must be always present.
40280 The feature that is present determines which flavor of m68k is
40281 used. The feature that is present should contain registers
40282 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
40283 @samp{sp}, @samp{ps} and @samp{pc}.
40285 @item @samp{org.gnu.gdb.coldfire.fp}
40286 This feature is optional. If present, it should contain registers
40287 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
40291 @node PowerPC Features
40292 @subsection PowerPC Features
40293 @cindex target descriptions, PowerPC features
40295 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
40296 targets. It should contain registers @samp{r0} through @samp{r31},
40297 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
40298 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
40300 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
40301 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
40303 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
40304 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
40307 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
40308 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
40309 will combine these registers with the floating point registers
40310 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
40311 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
40312 through @samp{vs63}, the set of vector registers for POWER7.
40314 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
40315 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
40316 @samp{spefscr}. SPE targets should provide 32-bit registers in
40317 @samp{org.gnu.gdb.power.core} and provide the upper halves in
40318 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
40319 these to present registers @samp{ev0} through @samp{ev31} to the
40322 @node TIC6x Features
40323 @subsection TMS320C6x Features
40324 @cindex target descriptions, TIC6x features
40325 @cindex target descriptions, TMS320C6x features
40326 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
40327 targets. It should contain registers @samp{A0} through @samp{A15},
40328 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
40330 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
40331 contain registers @samp{A16} through @samp{A31} and @samp{B16}
40332 through @samp{B31}.
40334 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
40335 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
40337 @node Operating System Information
40338 @appendix Operating System Information
40339 @cindex operating system information
40345 Users of @value{GDBN} often wish to obtain information about the state of
40346 the operating system running on the target---for example the list of
40347 processes, or the list of open files. This section describes the
40348 mechanism that makes it possible. This mechanism is similar to the
40349 target features mechanism (@pxref{Target Descriptions}), but focuses
40350 on a different aspect of target.
40352 Operating system information is retrived from the target via the
40353 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
40354 read}). The object name in the request should be @samp{osdata}, and
40355 the @var{annex} identifies the data to be fetched.
40358 @appendixsection Process list
40359 @cindex operating system information, process list
40361 When requesting the process list, the @var{annex} field in the
40362 @samp{qXfer} request should be @samp{processes}. The returned data is
40363 an XML document. The formal syntax of this document is defined in
40364 @file{gdb/features/osdata.dtd}.
40366 An example document is:
40369 <?xml version="1.0"?>
40370 <!DOCTYPE target SYSTEM "osdata.dtd">
40371 <osdata type="processes">
40373 <column name="pid">1</column>
40374 <column name="user">root</column>
40375 <column name="command">/sbin/init</column>
40376 <column name="cores">1,2,3</column>
40381 Each item should include a column whose name is @samp{pid}. The value
40382 of that column should identify the process on the target. The
40383 @samp{user} and @samp{command} columns are optional, and will be
40384 displayed by @value{GDBN}. The @samp{cores} column, if present,
40385 should contain a comma-separated list of cores that this process
40386 is running on. Target may provide additional columns,
40387 which @value{GDBN} currently ignores.
40389 @node Trace File Format
40390 @appendix Trace File Format
40391 @cindex trace file format
40393 The trace file comes in three parts: a header, a textual description
40394 section, and a trace frame section with binary data.
40396 The header has the form @code{\x7fTRACE0\n}. The first byte is
40397 @code{0x7f} so as to indicate that the file contains binary data,
40398 while the @code{0} is a version number that may have different values
40401 The description section consists of multiple lines of @sc{ascii} text
40402 separated by newline characters (@code{0xa}). The lines may include a
40403 variety of optional descriptive or context-setting information, such
40404 as tracepoint definitions or register set size. @value{GDBN} will
40405 ignore any line that it does not recognize. An empty line marks the end
40408 @c FIXME add some specific types of data
40410 The trace frame section consists of a number of consecutive frames.
40411 Each frame begins with a two-byte tracepoint number, followed by a
40412 four-byte size giving the amount of data in the frame. The data in
40413 the frame consists of a number of blocks, each introduced by a
40414 character indicating its type (at least register, memory, and trace
40415 state variable). The data in this section is raw binary, not a
40416 hexadecimal or other encoding; its endianness matches the target's
40419 @c FIXME bi-arch may require endianness/arch info in description section
40422 @item R @var{bytes}
40423 Register block. The number and ordering of bytes matches that of a
40424 @code{g} packet in the remote protocol. Note that these are the
40425 actual bytes, in target order and @value{GDBN} register order, not a
40426 hexadecimal encoding.
40428 @item M @var{address} @var{length} @var{bytes}...
40429 Memory block. This is a contiguous block of memory, at the 8-byte
40430 address @var{address}, with a 2-byte length @var{length}, followed by
40431 @var{length} bytes.
40433 @item V @var{number} @var{value}
40434 Trace state variable block. This records the 8-byte signed value
40435 @var{value} of trace state variable numbered @var{number}.
40439 Future enhancements of the trace file format may include additional types
40442 @node Index Section Format
40443 @appendix @code{.gdb_index} section format
40444 @cindex .gdb_index section format
40445 @cindex index section format
40447 This section documents the index section that is created by @code{save
40448 gdb-index} (@pxref{Index Files}). The index section is
40449 DWARF-specific; some knowledge of DWARF is assumed in this
40452 The mapped index file format is designed to be directly
40453 @code{mmap}able on any architecture. In most cases, a datum is
40454 represented using a little-endian 32-bit integer value, called an
40455 @code{offset_type}. Big endian machines must byte-swap the values
40456 before using them. Exceptions to this rule are noted. The data is
40457 laid out such that alignment is always respected.
40459 A mapped index consists of several areas, laid out in order.
40463 The file header. This is a sequence of values, of @code{offset_type}
40464 unless otherwise noted:
40468 The version number, currently 7. Versions 1, 2 and 3 are obsolete.
40469 Version 4 uses a different hashing function from versions 5 and 6.
40470 Version 6 includes symbols for inlined functions, whereas versions 4
40471 and 5 do not. Version 7 adds attributes to the CU indices in the
40472 symbol table. @value{GDBN} will only read version 4, 5, or 6 indices
40473 by specifying @code{set use-deprecated-index-sections on}.
40476 The offset, from the start of the file, of the CU list.
40479 The offset, from the start of the file, of the types CU list. Note
40480 that this area can be empty, in which case this offset will be equal
40481 to the next offset.
40484 The offset, from the start of the file, of the address area.
40487 The offset, from the start of the file, of the symbol table.
40490 The offset, from the start of the file, of the constant pool.
40494 The CU list. This is a sequence of pairs of 64-bit little-endian
40495 values, sorted by the CU offset. The first element in each pair is
40496 the offset of a CU in the @code{.debug_info} section. The second
40497 element in each pair is the length of that CU. References to a CU
40498 elsewhere in the map are done using a CU index, which is just the
40499 0-based index into this table. Note that if there are type CUs, then
40500 conceptually CUs and type CUs form a single list for the purposes of
40504 The types CU list. This is a sequence of triplets of 64-bit
40505 little-endian values. In a triplet, the first value is the CU offset,
40506 the second value is the type offset in the CU, and the third value is
40507 the type signature. The types CU list is not sorted.
40510 The address area. The address area consists of a sequence of address
40511 entries. Each address entry has three elements:
40515 The low address. This is a 64-bit little-endian value.
40518 The high address. This is a 64-bit little-endian value. Like
40519 @code{DW_AT_high_pc}, the value is one byte beyond the end.
40522 The CU index. This is an @code{offset_type} value.
40526 The symbol table. This is an open-addressed hash table. The size of
40527 the hash table is always a power of 2.
40529 Each slot in the hash table consists of a pair of @code{offset_type}
40530 values. The first value is the offset of the symbol's name in the
40531 constant pool. The second value is the offset of the CU vector in the
40534 If both values are 0, then this slot in the hash table is empty. This
40535 is ok because while 0 is a valid constant pool index, it cannot be a
40536 valid index for both a string and a CU vector.
40538 The hash value for a table entry is computed by applying an
40539 iterative hash function to the symbol's name. Starting with an
40540 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
40541 the string is incorporated into the hash using the formula depending on the
40546 The formula is @code{r = r * 67 + c - 113}.
40548 @item Versions 5 to 7
40549 The formula is @code{r = r * 67 + tolower (c) - 113}.
40552 The terminating @samp{\0} is not incorporated into the hash.
40554 The step size used in the hash table is computed via
40555 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
40556 value, and @samp{size} is the size of the hash table. The step size
40557 is used to find the next candidate slot when handling a hash
40560 The names of C@t{++} symbols in the hash table are canonicalized. We
40561 don't currently have a simple description of the canonicalization
40562 algorithm; if you intend to create new index sections, you must read
40566 The constant pool. This is simply a bunch of bytes. It is organized
40567 so that alignment is correct: CU vectors are stored first, followed by
40570 A CU vector in the constant pool is a sequence of @code{offset_type}
40571 values. The first value is the number of CU indices in the vector.
40572 Each subsequent value is the index and symbol attributes of a CU in
40573 the CU list. This element in the hash table is used to indicate which
40574 CUs define the symbol and how the symbol is used.
40575 See below for the format of each CU index+attributes entry.
40577 A string in the constant pool is zero-terminated.
40580 Attributes were added to CU index values in @code{.gdb_index} version 7.
40581 If a symbol has multiple uses within a CU then there is one
40582 CU index+attributes value for each use.
40584 The format of each CU index+attributes entry is as follows
40590 This is the index of the CU in the CU list.
40592 These bits are reserved for future purposes and must be zero.
40594 The kind of the symbol in the CU.
40598 This value is reserved and should not be used.
40599 By reserving zero the full @code{offset_type} value is backwards compatible
40600 with previous versions of the index.
40602 The symbol is a type.
40604 The symbol is a variable or an enum value.
40606 The symbol is a function.
40608 Any other kind of symbol.
40610 These values are reserved.
40614 This bit is zero if the value is global and one if it is static.
40616 The determination of whether a symbol is global or static is complicated.
40617 The authorative reference is the file @file{dwarf2read.c} in
40618 @value{GDBN} sources.
40622 This pseudo-code describes the computation of a symbol's kind and
40623 global/static attributes in the index.
40626 is_external = get_attribute (die, DW_AT_external);
40627 language = get_attribute (cu_die, DW_AT_language);
40630 case DW_TAG_typedef:
40631 case DW_TAG_base_type:
40632 case DW_TAG_subrange_type:
40636 case DW_TAG_enumerator:
40638 is_static = (language != CPLUS && language != JAVA);
40640 case DW_TAG_subprogram:
40642 is_static = ! (is_external || language == ADA);
40644 case DW_TAG_constant:
40646 is_static = ! is_external;
40648 case DW_TAG_variable:
40650 is_static = ! is_external;
40652 case DW_TAG_namespace:
40656 case DW_TAG_class_type:
40657 case DW_TAG_interface_type:
40658 case DW_TAG_structure_type:
40659 case DW_TAG_union_type:
40660 case DW_TAG_enumeration_type:
40662 is_static = (language != CPLUS && language != JAVA);
40671 @node GNU Free Documentation License
40672 @appendix GNU Free Documentation License
40675 @node Concept Index
40676 @unnumbered Concept Index
40680 @node Command and Variable Index
40681 @unnumbered Command, Variable, and Function Index
40686 % I think something like @@colophon should be in texinfo. In the
40688 \long\def\colophon{\hbox to0pt{}\vfill
40689 \centerline{The body of this manual is set in}
40690 \centerline{\fontname\tenrm,}
40691 \centerline{with headings in {\bf\fontname\tenbf}}
40692 \centerline{and examples in {\tt\fontname\tentt}.}
40693 \centerline{{\it\fontname\tenit\/},}
40694 \centerline{{\bf\fontname\tenbf}, and}
40695 \centerline{{\sl\fontname\tensl\/}}
40696 \centerline{are used for emphasis.}\vfill}
40698 % Blame: doc@@cygnus.com, 1991.