1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-2014 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.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
23 @c To avoid file-name clashes between index.html and Index.html, when
24 @c the manual is produced on a Posix host and then moved to a
25 @c case-insensitive filesystem (e.g., MS-Windows), we separate the
26 @c indices into two: Concept Index and all the rest.
30 @c readline appendices use @vindex, @findex and @ftable,
31 @c annotate.texi and gdbmi use @findex.
34 @c !!set GDB manual's edition---not the same as GDB version!
35 @c This is updated by GNU Press.
38 @c !!set GDB edit command default editor
41 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
43 @c This is a dir.info fragment to support semi-automated addition of
44 @c manuals to an info tree.
45 @dircategory Software development
47 * Gdb: (gdb). The GNU debugger.
48 * gdbserver: (gdb) Server. The GNU debugging server.
52 @c man begin COPYRIGHT
53 Copyright @copyright{} 1988-2014 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.''
69 This file documents the @sc{gnu} debugger @value{GDBN}.
71 This is the @value{EDITION} Edition, of @cite{Debugging with
72 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
73 @ifset VERSION_PACKAGE
74 @value{VERSION_PACKAGE}
76 Version @value{GDBVN}.
82 @title Debugging with @value{GDBN}
83 @subtitle The @sc{gnu} Source-Level Debugger
85 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
86 @ifset VERSION_PACKAGE
88 @subtitle @value{VERSION_PACKAGE}
90 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
94 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
95 \hfill {\it Debugging with @value{GDBN}}\par
96 \hfill \TeX{}info \texinfoversion\par
100 @vskip 0pt plus 1filll
101 Published by the Free Software Foundation @*
102 51 Franklin Street, Fifth Floor,
103 Boston, MA 02110-1301, USA@*
104 ISBN 978-0-9831592-3-0 @*
111 @node Top, Summary, (dir), (dir)
113 @top Debugging with @value{GDBN}
115 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
117 This is the @value{EDITION} Edition, for @value{GDBN}
118 @ifset VERSION_PACKAGE
119 @value{VERSION_PACKAGE}
121 Version @value{GDBVN}.
123 Copyright (C) 1988-2014 Free Software Foundation, Inc.
125 This edition of the GDB manual is dedicated to the memory of Fred
126 Fish. Fred was a long-standing contributor to GDB and to Free
127 software in general. We will miss him.
130 * Summary:: Summary of @value{GDBN}
131 * Sample Session:: A sample @value{GDBN} session
133 * Invocation:: Getting in and out of @value{GDBN}
134 * Commands:: @value{GDBN} commands
135 * Running:: Running programs under @value{GDBN}
136 * Stopping:: Stopping and continuing
137 * Reverse Execution:: Running programs backward
138 * Process Record and Replay:: Recording inferior's execution and replaying it
139 * Stack:: Examining the stack
140 * Source:: Examining source files
141 * Data:: Examining data
142 * Optimized Code:: Debugging optimized code
143 * Macros:: Preprocessor Macros
144 * Tracepoints:: Debugging remote targets non-intrusively
145 * Overlays:: Debugging programs that use overlays
147 * Languages:: Using @value{GDBN} with different languages
149 * Symbols:: Examining the symbol table
150 * Altering:: Altering execution
151 * GDB Files:: @value{GDBN} files
152 * Targets:: Specifying a debugging target
153 * Remote Debugging:: Debugging remote programs
154 * Configurations:: Configuration-specific information
155 * Controlling GDB:: Controlling @value{GDBN}
156 * Extending GDB:: Extending @value{GDBN}
157 * Interpreters:: Command Interpreters
158 * TUI:: @value{GDBN} Text User Interface
159 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
160 * GDB/MI:: @value{GDBN}'s Machine Interface.
161 * Annotations:: @value{GDBN}'s annotation interface.
162 * JIT Interface:: Using the JIT debugging interface.
163 * In-Process Agent:: In-Process Agent
165 * GDB Bugs:: Reporting bugs in @value{GDBN}
167 @ifset SYSTEM_READLINE
168 * Command Line Editing: (rluserman). Command Line Editing
169 * Using History Interactively: (history). Using History Interactively
171 @ifclear SYSTEM_READLINE
172 * Command Line Editing:: Command Line Editing
173 * Using History Interactively:: Using History Interactively
175 * In Memoriam:: In Memoriam
176 * Formatting Documentation:: How to format and print @value{GDBN} documentation
177 * Installing GDB:: Installing GDB
178 * Maintenance Commands:: Maintenance Commands
179 * Remote Protocol:: GDB Remote Serial Protocol
180 * Agent Expressions:: The GDB Agent Expression Mechanism
181 * Target Descriptions:: How targets can describe themselves to
183 * Operating System Information:: Getting additional information from
185 * Trace File Format:: GDB trace file format
186 * Index Section Format:: .gdb_index section format
187 * Man Pages:: Manual pages
188 * Copying:: GNU General Public License says
189 how you can copy and share GDB
190 * GNU Free Documentation License:: The license for this documentation
191 * Concept Index:: Index of @value{GDBN} concepts
192 * Command and Variable Index:: Index of @value{GDBN} commands, variables,
193 functions, and Python data types
201 @unnumbered Summary of @value{GDBN}
203 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
204 going on ``inside'' another program while it executes---or what another
205 program was doing at the moment it crashed.
207 @value{GDBN} can do four main kinds of things (plus other things in support of
208 these) to help you catch bugs in the act:
212 Start your program, specifying anything that might affect its behavior.
215 Make your program stop on specified conditions.
218 Examine what has happened, when your program has stopped.
221 Change things in your program, so you can experiment with correcting the
222 effects of one bug and go on to learn about another.
225 You can use @value{GDBN} to debug programs written in C and C@t{++}.
226 For more information, see @ref{Supported Languages,,Supported Languages}.
227 For more information, see @ref{C,,C and C++}.
229 Support for D is partial. For information on D, see
233 Support for Modula-2 is partial. For information on Modula-2, see
234 @ref{Modula-2,,Modula-2}.
236 Support for OpenCL C is partial. For information on OpenCL C, see
237 @ref{OpenCL C,,OpenCL C}.
240 Debugging Pascal programs which use sets, subranges, file variables, or
241 nested functions does not currently work. @value{GDBN} does not support
242 entering expressions, printing values, or similar features using Pascal
246 @value{GDBN} can be used to debug programs written in Fortran, although
247 it may be necessary to refer to some variables with a trailing
250 @value{GDBN} can be used to debug programs written in Objective-C,
251 using either the Apple/NeXT or the GNU Objective-C runtime.
254 * Free Software:: Freely redistributable software
255 * Free Documentation:: Free Software Needs Free Documentation
256 * Contributors:: Contributors to GDB
260 @unnumberedsec Free Software
262 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
263 General Public License
264 (GPL). The GPL gives you the freedom to copy or adapt a licensed
265 program---but every person getting a copy also gets with it the
266 freedom to modify that copy (which means that they must get access to
267 the source code), and the freedom to distribute further copies.
268 Typical software companies use copyrights to limit your freedoms; the
269 Free Software Foundation uses the GPL to preserve these freedoms.
271 Fundamentally, the General Public License is a license which says that
272 you have these freedoms and that you cannot take these freedoms away
275 @node Free Documentation
276 @unnumberedsec Free Software Needs Free Documentation
278 The biggest deficiency in the free software community today is not in
279 the software---it is the lack of good free documentation that we can
280 include with the free software. Many of our most important
281 programs do not come with free reference manuals and free introductory
282 texts. Documentation is an essential part of any software package;
283 when an important free software package does not come with a free
284 manual and a free tutorial, that is a major gap. We have many such
287 Consider Perl, for instance. The tutorial manuals that people
288 normally use are non-free. How did this come about? Because the
289 authors of those manuals published them with restrictive terms---no
290 copying, no modification, source files not available---which exclude
291 them from the free software world.
293 That wasn't the first time this sort of thing happened, and it was far
294 from the last. Many times we have heard a GNU user eagerly describe a
295 manual that he is writing, his intended contribution to the community,
296 only to learn that he had ruined everything by signing a publication
297 contract to make it non-free.
299 Free documentation, like free software, is a matter of freedom, not
300 price. The problem with the non-free manual is not that publishers
301 charge a price for printed copies---that in itself is fine. (The Free
302 Software Foundation sells printed copies of manuals, too.) The
303 problem is the restrictions on the use of the manual. Free manuals
304 are available in source code form, and give you permission to copy and
305 modify. Non-free manuals do not allow this.
307 The criteria of freedom for a free manual are roughly the same as for
308 free software. Redistribution (including the normal kinds of
309 commercial redistribution) must be permitted, so that the manual can
310 accompany every copy of the program, both on-line and on paper.
312 Permission for modification of the technical content is crucial too.
313 When people modify the software, adding or changing features, if they
314 are conscientious they will change the manual too---so they can
315 provide accurate and clear documentation for the modified program. A
316 manual that leaves you no choice but to write a new manual to document
317 a changed version of the program is not really available to our
320 Some kinds of limits on the way modification is handled are
321 acceptable. For example, requirements to preserve the original
322 author's copyright notice, the distribution terms, or the list of
323 authors, are ok. It is also no problem to require modified versions
324 to include notice that they were modified. Even entire sections that
325 may not be deleted or changed are acceptable, as long as they deal
326 with nontechnical topics (like this one). These kinds of restrictions
327 are acceptable because they don't obstruct the community's normal use
330 However, it must be possible to modify all the @emph{technical}
331 content of the manual, and then distribute the result in all the usual
332 media, through all the usual channels. Otherwise, the restrictions
333 obstruct the use of the manual, it is not free, and we need another
334 manual to replace it.
336 Please spread the word about this issue. Our community continues to
337 lose manuals to proprietary publishing. If we spread the word that
338 free software needs free reference manuals and free tutorials, perhaps
339 the next person who wants to contribute by writing documentation will
340 realize, before it is too late, that only free manuals contribute to
341 the free software community.
343 If you are writing documentation, please insist on publishing it under
344 the GNU Free Documentation License or another free documentation
345 license. Remember that this decision requires your approval---you
346 don't have to let the publisher decide. Some commercial publishers
347 will use a free license if you insist, but they will not propose the
348 option; it is up to you to raise the issue and say firmly that this is
349 what you want. If the publisher you are dealing with refuses, please
350 try other publishers. If you're not sure whether a proposed license
351 is free, write to @email{licensing@@gnu.org}.
353 You can encourage commercial publishers to sell more free, copylefted
354 manuals and tutorials by buying them, and particularly by buying
355 copies from the publishers that paid for their writing or for major
356 improvements. Meanwhile, try to avoid buying non-free documentation
357 at all. Check the distribution terms of a manual before you buy it,
358 and insist that whoever seeks your business must respect your freedom.
359 Check the history of the book, and try to reward the publishers that
360 have paid or pay the authors to work on it.
362 The Free Software Foundation maintains a list of free documentation
363 published by other publishers, at
364 @url{http://www.fsf.org/doc/other-free-books.html}.
367 @unnumberedsec Contributors to @value{GDBN}
369 Richard Stallman was the original author of @value{GDBN}, and of many
370 other @sc{gnu} programs. Many others have contributed to its
371 development. This section attempts to credit major contributors. One
372 of the virtues of free software is that everyone is free to contribute
373 to it; with regret, we cannot actually acknowledge everyone here. The
374 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
375 blow-by-blow account.
377 Changes much prior to version 2.0 are lost in the mists of time.
380 @emph{Plea:} Additions to this section are particularly welcome. If you
381 or your friends (or enemies, to be evenhanded) have been unfairly
382 omitted from this list, we would like to add your names!
385 So that they may not regard their many labors as thankless, we
386 particularly thank those who shepherded @value{GDBN} through major
388 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
389 Jim Blandy (release 4.18);
390 Jason Molenda (release 4.17);
391 Stan Shebs (release 4.14);
392 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
393 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
394 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
395 Jim Kingdon (releases 3.5, 3.4, and 3.3);
396 and Randy Smith (releases 3.2, 3.1, and 3.0).
398 Richard Stallman, assisted at various times by Peter TerMaat, Chris
399 Hanson, and Richard Mlynarik, handled releases through 2.8.
401 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
402 in @value{GDBN}, with significant additional contributions from Per
403 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
404 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
405 much general update work leading to release 3.0).
407 @value{GDBN} uses the BFD subroutine library to examine multiple
408 object-file formats; BFD was a joint project of David V.
409 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
411 David Johnson wrote the original COFF support; Pace Willison did
412 the original support for encapsulated COFF.
414 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
416 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
417 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
419 Jean-Daniel Fekete contributed Sun 386i support.
420 Chris Hanson improved the HP9000 support.
421 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
422 David Johnson contributed Encore Umax support.
423 Jyrki Kuoppala contributed Altos 3068 support.
424 Jeff Law contributed HP PA and SOM support.
425 Keith Packard contributed NS32K support.
426 Doug Rabson contributed Acorn Risc Machine support.
427 Bob Rusk contributed Harris Nighthawk CX-UX support.
428 Chris Smith contributed Convex support (and Fortran debugging).
429 Jonathan Stone contributed Pyramid support.
430 Michael Tiemann contributed SPARC support.
431 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
432 Pace Willison contributed Intel 386 support.
433 Jay Vosburgh contributed Symmetry support.
434 Marko Mlinar contributed OpenRISC 1000 support.
436 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
438 Rich Schaefer and Peter Schauer helped with support of SunOS shared
441 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
442 about several machine instruction sets.
444 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
445 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
446 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
447 and RDI targets, respectively.
449 Brian Fox is the author of the readline libraries providing
450 command-line editing and command history.
452 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
453 Modula-2 support, and contributed the Languages chapter of this manual.
455 Fred Fish wrote most of the support for Unix System Vr4.
456 He also enhanced the command-completion support to cover C@t{++} overloaded
459 Hitachi America (now Renesas America), Ltd. sponsored the support for
460 H8/300, H8/500, and Super-H processors.
462 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
464 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
467 Toshiba sponsored the support for the TX39 Mips processor.
469 Matsushita sponsored the support for the MN10200 and MN10300 processors.
471 Fujitsu sponsored the support for SPARClite and FR30 processors.
473 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
476 Michael Snyder added support for tracepoints.
478 Stu Grossman wrote gdbserver.
480 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
481 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
483 The following people at the Hewlett-Packard Company contributed
484 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
485 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
486 compiler, and the Text User Interface (nee Terminal User Interface):
487 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
488 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
489 provided HP-specific information in this manual.
491 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
492 Robert Hoehne made significant contributions to the DJGPP port.
494 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
495 development since 1991. Cygnus engineers who have worked on @value{GDBN}
496 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
497 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
498 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
499 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
500 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
501 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
502 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
503 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
504 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
505 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
506 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
507 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
508 Zuhn have made contributions both large and small.
510 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
511 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
513 Jim Blandy added support for preprocessor macros, while working for Red
516 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
517 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
518 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
519 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
520 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
521 with the migration of old architectures to this new framework.
523 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
524 unwinder framework, this consisting of a fresh new design featuring
525 frame IDs, independent frame sniffers, and the sentinel frame. Mark
526 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
527 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
528 trad unwinders. The architecture-specific changes, each involving a
529 complete rewrite of the architecture's frame code, were carried out by
530 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
531 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
532 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
533 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
536 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
537 Tensilica, Inc.@: contributed support for Xtensa processors. Others
538 who have worked on the Xtensa port of @value{GDBN} in the past include
539 Steve Tjiang, John Newlin, and Scott Foehner.
541 Michael Eager and staff of Xilinx, Inc., contributed support for the
542 Xilinx MicroBlaze architecture.
545 @chapter A Sample @value{GDBN} Session
547 You can use this manual at your leisure to read all about @value{GDBN}.
548 However, a handful of commands are enough to get started using the
549 debugger. This chapter illustrates those commands.
552 In this sample session, we emphasize user input like this: @b{input},
553 to make it easier to pick out from the surrounding output.
556 @c FIXME: this example may not be appropriate for some configs, where
557 @c FIXME...primary interest is in remote use.
559 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
560 processor) exhibits the following bug: sometimes, when we change its
561 quote strings from the default, the commands used to capture one macro
562 definition within another stop working. In the following short @code{m4}
563 session, we define a macro @code{foo} which expands to @code{0000}; we
564 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
565 same thing. However, when we change the open quote string to
566 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
567 procedure fails to define a new synonym @code{baz}:
576 @b{define(bar,defn(`foo'))}
580 @b{changequote(<QUOTE>,<UNQUOTE>)}
582 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
585 m4: End of input: 0: fatal error: EOF in string
589 Let us use @value{GDBN} to try to see what is going on.
592 $ @b{@value{GDBP} m4}
593 @c FIXME: this falsifies the exact text played out, to permit smallbook
594 @c FIXME... format to come out better.
595 @value{GDBN} is free software and you are welcome to distribute copies
596 of it under certain conditions; type "show copying" to see
598 There is absolutely no warranty for @value{GDBN}; type "show warranty"
601 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
606 @value{GDBN} reads only enough symbol data to know where to find the
607 rest when needed; as a result, the first prompt comes up very quickly.
608 We now tell @value{GDBN} to use a narrower display width than usual, so
609 that examples fit in this manual.
612 (@value{GDBP}) @b{set width 70}
616 We need to see how the @code{m4} built-in @code{changequote} works.
617 Having looked at the source, we know the relevant subroutine is
618 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
619 @code{break} command.
622 (@value{GDBP}) @b{break m4_changequote}
623 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
627 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
628 control; as long as control does not reach the @code{m4_changequote}
629 subroutine, the program runs as usual:
632 (@value{GDBP}) @b{run}
633 Starting program: /work/Editorial/gdb/gnu/m4/m4
641 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
642 suspends execution of @code{m4}, displaying information about the
643 context where it stops.
646 @b{changequote(<QUOTE>,<UNQUOTE>)}
648 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
650 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
654 Now we use the command @code{n} (@code{next}) to advance execution to
655 the next line of the current function.
659 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
664 @code{set_quotes} looks like a promising subroutine. We can go into it
665 by using the command @code{s} (@code{step}) instead of @code{next}.
666 @code{step} goes to the next line to be executed in @emph{any}
667 subroutine, so it steps into @code{set_quotes}.
671 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
673 530 if (lquote != def_lquote)
677 The display that shows the subroutine where @code{m4} is now
678 suspended (and its arguments) is called a stack frame display. It
679 shows a summary of the stack. We can use the @code{backtrace}
680 command (which can also be spelled @code{bt}), to see where we are
681 in the stack as a whole: the @code{backtrace} command displays a
682 stack frame for each active subroutine.
685 (@value{GDBP}) @b{bt}
686 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
688 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
690 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
691 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
693 #4 0x79dc in expand_input () at macro.c:40
694 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
698 We step through a few more lines to see what happens. The first two
699 times, we can use @samp{s}; the next two times we use @code{n} to avoid
700 falling into the @code{xstrdup} subroutine.
704 0x3b5c 532 if (rquote != def_rquote)
706 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
707 def_lquote : xstrdup(lq);
709 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
712 538 len_lquote = strlen(rquote);
716 The last line displayed looks a little odd; we can examine the variables
717 @code{lquote} and @code{rquote} to see if they are in fact the new left
718 and right quotes we specified. We use the command @code{p}
719 (@code{print}) to see their values.
722 (@value{GDBP}) @b{p lquote}
723 $1 = 0x35d40 "<QUOTE>"
724 (@value{GDBP}) @b{p rquote}
725 $2 = 0x35d50 "<UNQUOTE>"
729 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
730 To look at some context, we can display ten lines of source
731 surrounding the current line with the @code{l} (@code{list}) command.
737 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
739 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
742 538 len_lquote = strlen(rquote);
743 539 len_rquote = strlen(lquote);
750 Let us step past the two lines that set @code{len_lquote} and
751 @code{len_rquote}, and then examine the values of those variables.
755 539 len_rquote = strlen(lquote);
758 (@value{GDBP}) @b{p len_lquote}
760 (@value{GDBP}) @b{p len_rquote}
765 That certainly looks wrong, assuming @code{len_lquote} and
766 @code{len_rquote} are meant to be the lengths of @code{lquote} and
767 @code{rquote} respectively. We can set them to better values using
768 the @code{p} command, since it can print the value of
769 any expression---and that expression can include subroutine calls and
773 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
775 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
780 Is that enough to fix the problem of using the new quotes with the
781 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
782 executing with the @code{c} (@code{continue}) command, and then try the
783 example that caused trouble initially:
789 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
796 Success! The new quotes now work just as well as the default ones. The
797 problem seems to have been just the two typos defining the wrong
798 lengths. We allow @code{m4} exit by giving it an EOF as input:
802 Program exited normally.
806 The message @samp{Program exited normally.} is from @value{GDBN}; it
807 indicates @code{m4} has finished executing. We can end our @value{GDBN}
808 session with the @value{GDBN} @code{quit} command.
811 (@value{GDBP}) @b{quit}
815 @chapter Getting In and Out of @value{GDBN}
817 This chapter discusses how to start @value{GDBN}, and how to get out of it.
821 type @samp{@value{GDBP}} to start @value{GDBN}.
823 type @kbd{quit} or @kbd{Ctrl-d} to exit.
827 * Invoking GDB:: How to start @value{GDBN}
828 * Quitting GDB:: How to quit @value{GDBN}
829 * Shell Commands:: How to use shell commands inside @value{GDBN}
830 * Logging Output:: How to log @value{GDBN}'s output to a file
834 @section Invoking @value{GDBN}
836 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
837 @value{GDBN} reads commands from the terminal until you tell it to exit.
839 You can also run @code{@value{GDBP}} with a variety of arguments and options,
840 to specify more of your debugging environment at the outset.
842 The command-line options described here are designed
843 to cover a variety of situations; in some environments, some of these
844 options may effectively be unavailable.
846 The most usual way to start @value{GDBN} is with one argument,
847 specifying an executable program:
850 @value{GDBP} @var{program}
854 You can also start with both an executable program and a core file
858 @value{GDBP} @var{program} @var{core}
861 You can, instead, specify a process ID as a second argument, if you want
862 to debug a running process:
865 @value{GDBP} @var{program} 1234
869 would attach @value{GDBN} to process @code{1234} (unless you also have a file
870 named @file{1234}; @value{GDBN} does check for a core file first).
872 Taking advantage of the second command-line argument requires a fairly
873 complete operating system; when you use @value{GDBN} as a remote
874 debugger attached to a bare board, there may not be any notion of
875 ``process'', and there is often no way to get a core dump. @value{GDBN}
876 will warn you if it is unable to attach or to read core dumps.
878 You can optionally have @code{@value{GDBP}} pass any arguments after the
879 executable file to the inferior using @code{--args}. This option stops
882 @value{GDBP} --args gcc -O2 -c foo.c
884 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
885 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
887 You can run @code{@value{GDBP}} without printing the front material, which describes
888 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
895 You can further control how @value{GDBN} starts up by using command-line
896 options. @value{GDBN} itself can remind you of the options available.
906 to display all available options and briefly describe their use
907 (@samp{@value{GDBP} -h} is a shorter equivalent).
909 All options and command line arguments you give are processed
910 in sequential order. The order makes a difference when the
911 @samp{-x} option is used.
915 * File Options:: Choosing files
916 * Mode Options:: Choosing modes
917 * Startup:: What @value{GDBN} does during startup
921 @subsection Choosing Files
923 When @value{GDBN} starts, it reads any arguments other than options as
924 specifying an executable file and core file (or process ID). This is
925 the same as if the arguments were specified by the @samp{-se} and
926 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
927 first argument that does not have an associated option flag as
928 equivalent to the @samp{-se} option followed by that argument; and the
929 second argument that does not have an associated option flag, if any, as
930 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
931 If the second argument begins with a decimal digit, @value{GDBN} will
932 first attempt to attach to it as a process, and if that fails, attempt
933 to open it as a corefile. If you have a corefile whose name begins with
934 a digit, you can prevent @value{GDBN} from treating it as a pid by
935 prefixing it with @file{./}, e.g.@: @file{./12345}.
937 If @value{GDBN} has not been configured to included core file support,
938 such as for most embedded targets, then it will complain about a second
939 argument and ignore it.
941 Many options have both long and short forms; both are shown in the
942 following list. @value{GDBN} also recognizes the long forms if you truncate
943 them, so long as enough of the option is present to be unambiguous.
944 (If you prefer, you can flag option arguments with @samp{--} rather
945 than @samp{-}, though we illustrate the more usual convention.)
947 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
948 @c way, both those who look for -foo and --foo in the index, will find
952 @item -symbols @var{file}
954 @cindex @code{--symbols}
956 Read symbol table from file @var{file}.
958 @item -exec @var{file}
960 @cindex @code{--exec}
962 Use file @var{file} as the executable file to execute when appropriate,
963 and for examining pure data in conjunction with a core dump.
967 Read symbol table from file @var{file} and use it as the executable
970 @item -core @var{file}
972 @cindex @code{--core}
974 Use file @var{file} as a core dump to examine.
976 @item -pid @var{number}
977 @itemx -p @var{number}
980 Connect to process ID @var{number}, as with the @code{attach} command.
982 @item -command @var{file}
984 @cindex @code{--command}
986 Execute commands from file @var{file}. The contents of this file is
987 evaluated exactly as the @code{source} command would.
988 @xref{Command Files,, Command files}.
990 @item -eval-command @var{command}
991 @itemx -ex @var{command}
992 @cindex @code{--eval-command}
994 Execute a single @value{GDBN} command.
996 This option may be used multiple times to call multiple commands. It may
997 also be interleaved with @samp{-command} as required.
1000 @value{GDBP} -ex 'target sim' -ex 'load' \
1001 -x setbreakpoints -ex 'run' a.out
1004 @item -init-command @var{file}
1005 @itemx -ix @var{file}
1006 @cindex @code{--init-command}
1008 Execute commands from file @var{file} before loading the inferior (but
1009 after loading gdbinit files).
1012 @item -init-eval-command @var{command}
1013 @itemx -iex @var{command}
1014 @cindex @code{--init-eval-command}
1016 Execute a single @value{GDBN} command before loading the inferior (but
1017 after loading gdbinit files).
1020 @item -directory @var{directory}
1021 @itemx -d @var{directory}
1022 @cindex @code{--directory}
1024 Add @var{directory} to the path to search for source and script files.
1028 @cindex @code{--readnow}
1030 Read each symbol file's entire symbol table immediately, rather than
1031 the default, which is to read it incrementally as it is needed.
1032 This makes startup slower, but makes future operations faster.
1037 @subsection Choosing Modes
1039 You can run @value{GDBN} in various alternative modes---for example, in
1040 batch mode or quiet mode.
1048 Do not execute commands found in any initialization file.
1049 There are three init files, loaded in the following order:
1052 @item @file{system.gdbinit}
1053 This is the system-wide init file.
1054 Its location is specified with the @code{--with-system-gdbinit}
1055 configure option (@pxref{System-wide configuration}).
1056 It is loaded first when @value{GDBN} starts, before command line options
1057 have been processed.
1058 @item @file{~/.gdbinit}
1059 This is the init file in your home directory.
1060 It is loaded next, after @file{system.gdbinit}, and before
1061 command options have been processed.
1062 @item @file{./.gdbinit}
1063 This is the init file in the current directory.
1064 It is loaded last, after command line options other than @code{-x} and
1065 @code{-ex} have been processed. Command line options @code{-x} and
1066 @code{-ex} are processed last, after @file{./.gdbinit} has been loaded.
1069 For further documentation on startup processing, @xref{Startup}.
1070 For documentation on how to write command files,
1071 @xref{Command Files,,Command Files}.
1076 Do not execute commands found in @file{~/.gdbinit}, the init file
1077 in your home directory.
1083 @cindex @code{--quiet}
1084 @cindex @code{--silent}
1086 ``Quiet''. Do not print the introductory and copyright messages. These
1087 messages are also suppressed in batch mode.
1090 @cindex @code{--batch}
1091 Run in batch mode. Exit with status @code{0} after processing all the
1092 command files specified with @samp{-x} (and all commands from
1093 initialization files, if not inhibited with @samp{-n}). Exit with
1094 nonzero status if an error occurs in executing the @value{GDBN} commands
1095 in the command files. Batch mode also disables pagination, sets unlimited
1096 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1097 off} were in effect (@pxref{Messages/Warnings}).
1099 Batch mode may be useful for running @value{GDBN} as a filter, for
1100 example to download and run a program on another computer; in order to
1101 make this more useful, the message
1104 Program exited normally.
1108 (which is ordinarily issued whenever a program running under
1109 @value{GDBN} control terminates) is not issued when running in batch
1113 @cindex @code{--batch-silent}
1114 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1115 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1116 unaffected). This is much quieter than @samp{-silent} and would be useless
1117 for an interactive session.
1119 This is particularly useful when using targets that give @samp{Loading section}
1120 messages, for example.
1122 Note that targets that give their output via @value{GDBN}, as opposed to
1123 writing directly to @code{stdout}, will also be made silent.
1125 @item -return-child-result
1126 @cindex @code{--return-child-result}
1127 The return code from @value{GDBN} will be the return code from the child
1128 process (the process being debugged), with the following exceptions:
1132 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1133 internal error. In this case the exit code is the same as it would have been
1134 without @samp{-return-child-result}.
1136 The user quits with an explicit value. E.g., @samp{quit 1}.
1138 The child process never runs, or is not allowed to terminate, in which case
1139 the exit code will be -1.
1142 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1143 when @value{GDBN} is being used as a remote program loader or simulator
1148 @cindex @code{--nowindows}
1150 ``No windows''. If @value{GDBN} comes with a graphical user interface
1151 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1152 interface. If no GUI is available, this option has no effect.
1156 @cindex @code{--windows}
1158 If @value{GDBN} includes a GUI, then this option requires it to be
1161 @item -cd @var{directory}
1163 Run @value{GDBN} using @var{directory} as its working directory,
1164 instead of the current directory.
1166 @item -data-directory @var{directory}
1167 @cindex @code{--data-directory}
1168 Run @value{GDBN} using @var{directory} as its data directory.
1169 The data directory is where @value{GDBN} searches for its
1170 auxiliary files. @xref{Data Files}.
1174 @cindex @code{--fullname}
1176 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1177 subprocess. It tells @value{GDBN} to output the full file name and line
1178 number in a standard, recognizable fashion each time a stack frame is
1179 displayed (which includes each time your program stops). This
1180 recognizable format looks like two @samp{\032} characters, followed by
1181 the file name, line number and character position separated by colons,
1182 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1183 @samp{\032} characters as a signal to display the source code for the
1186 @item -annotate @var{level}
1187 @cindex @code{--annotate}
1188 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1189 effect is identical to using @samp{set annotate @var{level}}
1190 (@pxref{Annotations}). The annotation @var{level} controls how much
1191 information @value{GDBN} prints together with its prompt, values of
1192 expressions, source lines, and other types of output. Level 0 is the
1193 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1194 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1195 that control @value{GDBN}, and level 2 has been deprecated.
1197 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1201 @cindex @code{--args}
1202 Change interpretation of command line so that arguments following the
1203 executable file are passed as command line arguments to the inferior.
1204 This option stops option processing.
1206 @item -baud @var{bps}
1208 @cindex @code{--baud}
1210 Set the line speed (baud rate or bits per second) of any serial
1211 interface used by @value{GDBN} for remote debugging.
1213 @item -l @var{timeout}
1215 Set the timeout (in seconds) of any communication used by @value{GDBN}
1216 for remote debugging.
1218 @item -tty @var{device}
1219 @itemx -t @var{device}
1220 @cindex @code{--tty}
1222 Run using @var{device} for your program's standard input and output.
1223 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1225 @c resolve the situation of these eventually
1227 @cindex @code{--tui}
1228 Activate the @dfn{Text User Interface} when starting. The Text User
1229 Interface manages several text windows on the terminal, showing
1230 source, assembly, registers and @value{GDBN} command outputs
1231 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1232 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1233 Using @value{GDBN} under @sc{gnu} Emacs}).
1236 @c @cindex @code{--xdb}
1237 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1238 @c For information, see the file @file{xdb_trans.html}, which is usually
1239 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1242 @item -interpreter @var{interp}
1243 @cindex @code{--interpreter}
1244 Use the interpreter @var{interp} for interface with the controlling
1245 program or device. This option is meant to be set by programs which
1246 communicate with @value{GDBN} using it as a back end.
1247 @xref{Interpreters, , Command Interpreters}.
1249 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1250 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1251 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1252 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1253 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1254 @sc{gdb/mi} interfaces are no longer supported.
1257 @cindex @code{--write}
1258 Open the executable and core files for both reading and writing. This
1259 is equivalent to the @samp{set write on} command inside @value{GDBN}
1263 @cindex @code{--statistics}
1264 This option causes @value{GDBN} to print statistics about time and
1265 memory usage after it completes each command and returns to the prompt.
1268 @cindex @code{--version}
1269 This option causes @value{GDBN} to print its version number and
1270 no-warranty blurb, and exit.
1272 @item -configuration
1273 @cindex @code{--configuration}
1274 This option causes @value{GDBN} to print details about its build-time
1275 configuration parameters, and then exit. These details can be
1276 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1281 @subsection What @value{GDBN} Does During Startup
1282 @cindex @value{GDBN} startup
1284 Here's the description of what @value{GDBN} does during session startup:
1288 Sets up the command interpreter as specified by the command line
1289 (@pxref{Mode Options, interpreter}).
1293 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1294 used when building @value{GDBN}; @pxref{System-wide configuration,
1295 ,System-wide configuration and settings}) and executes all the commands in
1298 @anchor{Home Directory Init File}
1300 Reads the init file (if any) in your home directory@footnote{On
1301 DOS/Windows systems, the home directory is the one pointed to by the
1302 @code{HOME} environment variable.} and executes all the commands in
1305 @anchor{Option -init-eval-command}
1307 Executes commands and command files specified by the @samp{-iex} and
1308 @samp{-ix} options in their specified order. Usually you should use the
1309 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1310 settings before @value{GDBN} init files get executed and before inferior
1314 Processes command line options and operands.
1316 @anchor{Init File in the Current Directory during Startup}
1318 Reads and executes the commands from init file (if any) in the current
1319 working directory as long as @samp{set auto-load local-gdbinit} is set to
1320 @samp{on} (@pxref{Init File in the Current Directory}).
1321 This is only done if the current directory is
1322 different from your home directory. Thus, you can have more than one
1323 init file, one generic in your home directory, and another, specific
1324 to the program you are debugging, in the directory where you invoke
1328 If the command line specified a program to debug, or a process to
1329 attach to, or a core file, @value{GDBN} loads any auto-loaded
1330 scripts provided for the program or for its loaded shared libraries.
1331 @xref{Auto-loading}.
1333 If you wish to disable the auto-loading during startup,
1334 you must do something like the following:
1337 $ gdb -iex "set auto-load python-scripts off" myprogram
1340 Option @samp{-ex} does not work because the auto-loading is then turned
1344 Executes commands and command files specified by the @samp{-ex} and
1345 @samp{-x} options in their specified order. @xref{Command Files}, for
1346 more details about @value{GDBN} command files.
1349 Reads the command history recorded in the @dfn{history file}.
1350 @xref{Command History}, for more details about the command history and the
1351 files where @value{GDBN} records it.
1354 Init files use the same syntax as @dfn{command files} (@pxref{Command
1355 Files}) and are processed by @value{GDBN} in the same way. The init
1356 file in your home directory can set options (such as @samp{set
1357 complaints}) that affect subsequent processing of command line options
1358 and operands. Init files are not executed if you use the @samp{-nx}
1359 option (@pxref{Mode Options, ,Choosing Modes}).
1361 To display the list of init files loaded by gdb at startup, you
1362 can use @kbd{gdb --help}.
1364 @cindex init file name
1365 @cindex @file{.gdbinit}
1366 @cindex @file{gdb.ini}
1367 The @value{GDBN} init files are normally called @file{.gdbinit}.
1368 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1369 the limitations of file names imposed by DOS filesystems. The Windows
1370 port of @value{GDBN} uses the standard name, but if it finds a
1371 @file{gdb.ini} file in your home directory, it warns you about that
1372 and suggests to rename the file to the standard name.
1376 @section Quitting @value{GDBN}
1377 @cindex exiting @value{GDBN}
1378 @cindex leaving @value{GDBN}
1381 @kindex quit @r{[}@var{expression}@r{]}
1382 @kindex q @r{(@code{quit})}
1383 @item quit @r{[}@var{expression}@r{]}
1385 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1386 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1387 do not supply @var{expression}, @value{GDBN} will terminate normally;
1388 otherwise it will terminate using the result of @var{expression} as the
1393 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1394 terminates the action of any @value{GDBN} command that is in progress and
1395 returns to @value{GDBN} command level. It is safe to type the interrupt
1396 character at any time because @value{GDBN} does not allow it to take effect
1397 until a time when it is safe.
1399 If you have been using @value{GDBN} to control an attached process or
1400 device, you can release it with the @code{detach} command
1401 (@pxref{Attach, ,Debugging an Already-running Process}).
1403 @node Shell Commands
1404 @section Shell Commands
1406 If you need to execute occasional shell commands during your
1407 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1408 just use the @code{shell} command.
1413 @cindex shell escape
1414 @item shell @var{command-string}
1415 @itemx !@var{command-string}
1416 Invoke a standard shell to execute @var{command-string}.
1417 Note that no space is needed between @code{!} and @var{command-string}.
1418 If it exists, the environment variable @code{SHELL} determines which
1419 shell to run. Otherwise @value{GDBN} uses the default shell
1420 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1423 The utility @code{make} is often needed in development environments.
1424 You do not have to use the @code{shell} command for this purpose in
1429 @cindex calling make
1430 @item make @var{make-args}
1431 Execute the @code{make} program with the specified
1432 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1435 @node Logging Output
1436 @section Logging Output
1437 @cindex logging @value{GDBN} output
1438 @cindex save @value{GDBN} output to a file
1440 You may want to save the output of @value{GDBN} commands to a file.
1441 There are several commands to control @value{GDBN}'s logging.
1445 @item set logging on
1447 @item set logging off
1449 @cindex logging file name
1450 @item set logging file @var{file}
1451 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1452 @item set logging overwrite [on|off]
1453 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1454 you want @code{set logging on} to overwrite the logfile instead.
1455 @item set logging redirect [on|off]
1456 By default, @value{GDBN} output will go to both the terminal and the logfile.
1457 Set @code{redirect} if you want output to go only to the log file.
1458 @kindex show logging
1460 Show the current values of the logging settings.
1464 @chapter @value{GDBN} Commands
1466 You can abbreviate a @value{GDBN} command to the first few letters of the command
1467 name, if that abbreviation is unambiguous; and you can repeat certain
1468 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1469 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1470 show you the alternatives available, if there is more than one possibility).
1473 * Command Syntax:: How to give commands to @value{GDBN}
1474 * Completion:: Command completion
1475 * Help:: How to ask @value{GDBN} for help
1478 @node Command Syntax
1479 @section Command Syntax
1481 A @value{GDBN} command is a single line of input. There is no limit on
1482 how long it can be. It starts with a command name, which is followed by
1483 arguments whose meaning depends on the command name. For example, the
1484 command @code{step} accepts an argument which is the number of times to
1485 step, as in @samp{step 5}. You can also use the @code{step} command
1486 with no arguments. Some commands do not allow any arguments.
1488 @cindex abbreviation
1489 @value{GDBN} command names may always be truncated if that abbreviation is
1490 unambiguous. Other possible command abbreviations are listed in the
1491 documentation for individual commands. In some cases, even ambiguous
1492 abbreviations are allowed; for example, @code{s} is specially defined as
1493 equivalent to @code{step} even though there are other commands whose
1494 names start with @code{s}. You can test abbreviations by using them as
1495 arguments to the @code{help} command.
1497 @cindex repeating commands
1498 @kindex RET @r{(repeat last command)}
1499 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1500 repeat the previous command. Certain commands (for example, @code{run})
1501 will not repeat this way; these are commands whose unintentional
1502 repetition might cause trouble and which you are unlikely to want to
1503 repeat. User-defined commands can disable this feature; see
1504 @ref{Define, dont-repeat}.
1506 The @code{list} and @code{x} commands, when you repeat them with
1507 @key{RET}, construct new arguments rather than repeating
1508 exactly as typed. This permits easy scanning of source or memory.
1510 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1511 output, in a way similar to the common utility @code{more}
1512 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1513 @key{RET} too many in this situation, @value{GDBN} disables command
1514 repetition after any command that generates this sort of display.
1516 @kindex # @r{(a comment)}
1518 Any text from a @kbd{#} to the end of the line is a comment; it does
1519 nothing. This is useful mainly in command files (@pxref{Command
1520 Files,,Command Files}).
1522 @cindex repeating command sequences
1523 @kindex Ctrl-o @r{(operate-and-get-next)}
1524 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1525 commands. This command accepts the current line, like @key{RET}, and
1526 then fetches the next line relative to the current line from the history
1530 @section Command Completion
1533 @cindex word completion
1534 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1535 only one possibility; it can also show you what the valid possibilities
1536 are for the next word in a command, at any time. This works for @value{GDBN}
1537 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1539 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1540 of a word. If there is only one possibility, @value{GDBN} fills in the
1541 word, and waits for you to finish the command (or press @key{RET} to
1542 enter it). For example, if you type
1544 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1545 @c complete accuracy in these examples; space introduced for clarity.
1546 @c If texinfo enhancements make it unnecessary, it would be nice to
1547 @c replace " @key" by "@key" in the following...
1549 (@value{GDBP}) info bre @key{TAB}
1553 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1554 the only @code{info} subcommand beginning with @samp{bre}:
1557 (@value{GDBP}) info breakpoints
1561 You can either press @key{RET} at this point, to run the @code{info
1562 breakpoints} command, or backspace and enter something else, if
1563 @samp{breakpoints} does not look like the command you expected. (If you
1564 were sure you wanted @code{info breakpoints} in the first place, you
1565 might as well just type @key{RET} immediately after @samp{info bre},
1566 to exploit command abbreviations rather than command completion).
1568 If there is more than one possibility for the next word when you press
1569 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1570 characters and try again, or just press @key{TAB} a second time;
1571 @value{GDBN} displays all the possible completions for that word. For
1572 example, you might want to set a breakpoint on a subroutine whose name
1573 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1574 just sounds the bell. Typing @key{TAB} again displays all the
1575 function names in your program that begin with those characters, for
1579 (@value{GDBP}) b make_ @key{TAB}
1580 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1581 make_a_section_from_file make_environ
1582 make_abs_section make_function_type
1583 make_blockvector make_pointer_type
1584 make_cleanup make_reference_type
1585 make_command make_symbol_completion_list
1586 (@value{GDBP}) b make_
1590 After displaying the available possibilities, @value{GDBN} copies your
1591 partial input (@samp{b make_} in the example) so you can finish the
1594 If you just want to see the list of alternatives in the first place, you
1595 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1596 means @kbd{@key{META} ?}. You can type this either by holding down a
1597 key designated as the @key{META} shift on your keyboard (if there is
1598 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1600 @cindex quotes in commands
1601 @cindex completion of quoted strings
1602 Sometimes the string you need, while logically a ``word'', may contain
1603 parentheses or other characters that @value{GDBN} normally excludes from
1604 its notion of a word. To permit word completion to work in this
1605 situation, you may enclose words in @code{'} (single quote marks) in
1606 @value{GDBN} commands.
1608 The most likely situation where you might need this is in typing the
1609 name of a C@t{++} function. This is because C@t{++} allows function
1610 overloading (multiple definitions of the same function, distinguished
1611 by argument type). For example, when you want to set a breakpoint you
1612 may need to distinguish whether you mean the version of @code{name}
1613 that takes an @code{int} parameter, @code{name(int)}, or the version
1614 that takes a @code{float} parameter, @code{name(float)}. To use the
1615 word-completion facilities in this situation, type a single quote
1616 @code{'} at the beginning of the function name. This alerts
1617 @value{GDBN} that it may need to consider more information than usual
1618 when you press @key{TAB} or @kbd{M-?} to request word completion:
1621 (@value{GDBP}) b 'bubble( @kbd{M-?}
1622 bubble(double,double) bubble(int,int)
1623 (@value{GDBP}) b 'bubble(
1626 In some cases, @value{GDBN} can tell that completing a name requires using
1627 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1628 completing as much as it can) if you do not type the quote in the first
1632 (@value{GDBP}) b bub @key{TAB}
1633 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1634 (@value{GDBP}) b 'bubble(
1638 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1639 you have not yet started typing the argument list when you ask for
1640 completion on an overloaded symbol.
1642 For more information about overloaded functions, see @ref{C Plus Plus
1643 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1644 overload-resolution off} to disable overload resolution;
1645 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1647 @cindex completion of structure field names
1648 @cindex structure field name completion
1649 @cindex completion of union field names
1650 @cindex union field name completion
1651 When completing in an expression which looks up a field in a
1652 structure, @value{GDBN} also tries@footnote{The completer can be
1653 confused by certain kinds of invalid expressions. Also, it only
1654 examines the static type of the expression, not the dynamic type.} to
1655 limit completions to the field names available in the type of the
1659 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1660 magic to_fputs to_rewind
1661 to_data to_isatty to_write
1662 to_delete to_put to_write_async_safe
1667 This is because the @code{gdb_stdout} is a variable of the type
1668 @code{struct ui_file} that is defined in @value{GDBN} sources as
1675 ui_file_flush_ftype *to_flush;
1676 ui_file_write_ftype *to_write;
1677 ui_file_write_async_safe_ftype *to_write_async_safe;
1678 ui_file_fputs_ftype *to_fputs;
1679 ui_file_read_ftype *to_read;
1680 ui_file_delete_ftype *to_delete;
1681 ui_file_isatty_ftype *to_isatty;
1682 ui_file_rewind_ftype *to_rewind;
1683 ui_file_put_ftype *to_put;
1690 @section Getting Help
1691 @cindex online documentation
1694 You can always ask @value{GDBN} itself for information on its commands,
1695 using the command @code{help}.
1698 @kindex h @r{(@code{help})}
1701 You can use @code{help} (abbreviated @code{h}) with no arguments to
1702 display a short list of named classes of commands:
1706 List of classes of commands:
1708 aliases -- Aliases of other commands
1709 breakpoints -- Making program stop at certain points
1710 data -- Examining data
1711 files -- Specifying and examining files
1712 internals -- Maintenance commands
1713 obscure -- Obscure features
1714 running -- Running the program
1715 stack -- Examining the stack
1716 status -- Status inquiries
1717 support -- Support facilities
1718 tracepoints -- Tracing of program execution without
1719 stopping the program
1720 user-defined -- User-defined commands
1722 Type "help" followed by a class name for a list of
1723 commands in that class.
1724 Type "help" followed by command name for full
1726 Command name abbreviations are allowed if unambiguous.
1729 @c the above line break eliminates huge line overfull...
1731 @item help @var{class}
1732 Using one of the general help classes as an argument, you can get a
1733 list of the individual commands in that class. For example, here is the
1734 help display for the class @code{status}:
1737 (@value{GDBP}) help status
1742 @c Line break in "show" line falsifies real output, but needed
1743 @c to fit in smallbook page size.
1744 info -- Generic command for showing things
1745 about the program being debugged
1746 show -- Generic command for showing things
1749 Type "help" followed by command name for full
1751 Command name abbreviations are allowed if unambiguous.
1755 @item help @var{command}
1756 With a command name as @code{help} argument, @value{GDBN} displays a
1757 short paragraph on how to use that command.
1760 @item apropos @var{args}
1761 The @code{apropos} command searches through all of the @value{GDBN}
1762 commands, and their documentation, for the regular expression specified in
1763 @var{args}. It prints out all matches found. For example:
1774 alias -- Define a new command that is an alias of an existing command
1775 aliases -- Aliases of other commands
1776 d -- Delete some breakpoints or auto-display expressions
1777 del -- Delete some breakpoints or auto-display expressions
1778 delete -- Delete some breakpoints or auto-display expressions
1783 @item complete @var{args}
1784 The @code{complete @var{args}} command lists all the possible completions
1785 for the beginning of a command. Use @var{args} to specify the beginning of the
1786 command you want completed. For example:
1792 @noindent results in:
1803 @noindent This is intended for use by @sc{gnu} Emacs.
1806 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1807 and @code{show} to inquire about the state of your program, or the state
1808 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1809 manual introduces each of them in the appropriate context. The listings
1810 under @code{info} and under @code{show} in the Command, Variable, and
1811 Function Index point to all the sub-commands. @xref{Command and Variable
1817 @kindex i @r{(@code{info})}
1819 This command (abbreviated @code{i}) is for describing the state of your
1820 program. For example, you can show the arguments passed to a function
1821 with @code{info args}, list the registers currently in use with @code{info
1822 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1823 You can get a complete list of the @code{info} sub-commands with
1824 @w{@code{help info}}.
1828 You can assign the result of an expression to an environment variable with
1829 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1830 @code{set prompt $}.
1834 In contrast to @code{info}, @code{show} is for describing the state of
1835 @value{GDBN} itself.
1836 You can change most of the things you can @code{show}, by using the
1837 related command @code{set}; for example, you can control what number
1838 system is used for displays with @code{set radix}, or simply inquire
1839 which is currently in use with @code{show radix}.
1842 To display all the settable parameters and their current
1843 values, you can use @code{show} with no arguments; you may also use
1844 @code{info set}. Both commands produce the same display.
1845 @c FIXME: "info set" violates the rule that "info" is for state of
1846 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1847 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1851 Here are several miscellaneous @code{show} subcommands, all of which are
1852 exceptional in lacking corresponding @code{set} commands:
1855 @kindex show version
1856 @cindex @value{GDBN} version number
1858 Show what version of @value{GDBN} is running. You should include this
1859 information in @value{GDBN} bug-reports. If multiple versions of
1860 @value{GDBN} are in use at your site, you may need to determine which
1861 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1862 commands are introduced, and old ones may wither away. Also, many
1863 system vendors ship variant versions of @value{GDBN}, and there are
1864 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1865 The version number is the same as the one announced when you start
1868 @kindex show copying
1869 @kindex info copying
1870 @cindex display @value{GDBN} copyright
1873 Display information about permission for copying @value{GDBN}.
1875 @kindex show warranty
1876 @kindex info warranty
1878 @itemx info warranty
1879 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1880 if your version of @value{GDBN} comes with one.
1882 @kindex show configuration
1883 @item show configuration
1884 Display detailed information about the way @value{GDBN} was configured
1885 when it was built. This displays the optional arguments passed to the
1886 @file{configure} script and also configuration parameters detected
1887 automatically by @command{configure}. When reporting a @value{GDBN}
1888 bug (@pxref{GDB Bugs}), it is important to include this information in
1894 @chapter Running Programs Under @value{GDBN}
1896 When you run a program under @value{GDBN}, you must first generate
1897 debugging information when you compile it.
1899 You may start @value{GDBN} with its arguments, if any, in an environment
1900 of your choice. If you are doing native debugging, you may redirect
1901 your program's input and output, debug an already running process, or
1902 kill a child process.
1905 * Compilation:: Compiling for debugging
1906 * Starting:: Starting your program
1907 * Arguments:: Your program's arguments
1908 * Environment:: Your program's environment
1910 * Working Directory:: Your program's working directory
1911 * Input/Output:: Your program's input and output
1912 * Attach:: Debugging an already-running process
1913 * Kill Process:: Killing the child process
1915 * Inferiors and Programs:: Debugging multiple inferiors and programs
1916 * Threads:: Debugging programs with multiple threads
1917 * Forks:: Debugging forks
1918 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1922 @section Compiling for Debugging
1924 In order to debug a program effectively, you need to generate
1925 debugging information when you compile it. This debugging information
1926 is stored in the object file; it describes the data type of each
1927 variable or function and the correspondence between source line numbers
1928 and addresses in the executable code.
1930 To request debugging information, specify the @samp{-g} option when you run
1933 Programs that are to be shipped to your customers are compiled with
1934 optimizations, using the @samp{-O} compiler option. However, some
1935 compilers are unable to handle the @samp{-g} and @samp{-O} options
1936 together. Using those compilers, you cannot generate optimized
1937 executables containing debugging information.
1939 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1940 without @samp{-O}, making it possible to debug optimized code. We
1941 recommend that you @emph{always} use @samp{-g} whenever you compile a
1942 program. You may think your program is correct, but there is no sense
1943 in pushing your luck. For more information, see @ref{Optimized Code}.
1945 Older versions of the @sc{gnu} C compiler permitted a variant option
1946 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1947 format; if your @sc{gnu} C compiler has this option, do not use it.
1949 @value{GDBN} knows about preprocessor macros and can show you their
1950 expansion (@pxref{Macros}). Most compilers do not include information
1951 about preprocessor macros in the debugging information if you specify
1952 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
1953 the @sc{gnu} C compiler, provides macro information if you are using
1954 the DWARF debugging format, and specify the option @option{-g3}.
1956 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
1957 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
1958 information on @value{NGCC} options affecting debug information.
1960 You will have the best debugging experience if you use the latest
1961 version of the DWARF debugging format that your compiler supports.
1962 DWARF is currently the most expressive and best supported debugging
1963 format in @value{GDBN}.
1967 @section Starting your Program
1973 @kindex r @r{(@code{run})}
1976 Use the @code{run} command to start your program under @value{GDBN}.
1977 You must first specify the program name (except on VxWorks) with an
1978 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1979 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1980 (@pxref{Files, ,Commands to Specify Files}).
1984 If you are running your program in an execution environment that
1985 supports processes, @code{run} creates an inferior process and makes
1986 that process run your program. In some environments without processes,
1987 @code{run} jumps to the start of your program. Other targets,
1988 like @samp{remote}, are always running. If you get an error
1989 message like this one:
1992 The "remote" target does not support "run".
1993 Try "help target" or "continue".
1997 then use @code{continue} to run your program. You may need @code{load}
1998 first (@pxref{load}).
2000 The execution of a program is affected by certain information it
2001 receives from its superior. @value{GDBN} provides ways to specify this
2002 information, which you must do @emph{before} starting your program. (You
2003 can change it after starting your program, but such changes only affect
2004 your program the next time you start it.) This information may be
2005 divided into four categories:
2008 @item The @emph{arguments.}
2009 Specify the arguments to give your program as the arguments of the
2010 @code{run} command. If a shell is available on your target, the shell
2011 is used to pass the arguments, so that you may use normal conventions
2012 (such as wildcard expansion or variable substitution) in describing
2014 In Unix systems, you can control which shell is used with the
2015 @code{SHELL} environment variable. If you do not define @code{SHELL},
2016 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2017 use of any shell with the @code{set startup-with-shell} command (see
2020 @item The @emph{environment.}
2021 Your program normally inherits its environment from @value{GDBN}, but you can
2022 use the @value{GDBN} commands @code{set environment} and @code{unset
2023 environment} to change parts of the environment that affect
2024 your program. @xref{Environment, ,Your Program's Environment}.
2026 @item The @emph{working directory.}
2027 Your program inherits its working directory from @value{GDBN}. You can set
2028 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
2029 @xref{Working Directory, ,Your Program's Working Directory}.
2031 @item The @emph{standard input and output.}
2032 Your program normally uses the same device for standard input and
2033 standard output as @value{GDBN} is using. You can redirect input and output
2034 in the @code{run} command line, or you can use the @code{tty} command to
2035 set a different device for your program.
2036 @xref{Input/Output, ,Your Program's Input and Output}.
2039 @emph{Warning:} While input and output redirection work, you cannot use
2040 pipes to pass the output of the program you are debugging to another
2041 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2045 When you issue the @code{run} command, your program begins to execute
2046 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2047 of how to arrange for your program to stop. Once your program has
2048 stopped, you may call functions in your program, using the @code{print}
2049 or @code{call} commands. @xref{Data, ,Examining Data}.
2051 If the modification time of your symbol file has changed since the last
2052 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2053 table, and reads it again. When it does this, @value{GDBN} tries to retain
2054 your current breakpoints.
2059 @cindex run to main procedure
2060 The name of the main procedure can vary from language to language.
2061 With C or C@t{++}, the main procedure name is always @code{main}, but
2062 other languages such as Ada do not require a specific name for their
2063 main procedure. The debugger provides a convenient way to start the
2064 execution of the program and to stop at the beginning of the main
2065 procedure, depending on the language used.
2067 The @samp{start} command does the equivalent of setting a temporary
2068 breakpoint at the beginning of the main procedure and then invoking
2069 the @samp{run} command.
2071 @cindex elaboration phase
2072 Some programs contain an @dfn{elaboration} phase where some startup code is
2073 executed before the main procedure is called. This depends on the
2074 languages used to write your program. In C@t{++}, for instance,
2075 constructors for static and global objects are executed before
2076 @code{main} is called. It is therefore possible that the debugger stops
2077 before reaching the main procedure. However, the temporary breakpoint
2078 will remain to halt execution.
2080 Specify the arguments to give to your program as arguments to the
2081 @samp{start} command. These arguments will be given verbatim to the
2082 underlying @samp{run} command. Note that the same arguments will be
2083 reused if no argument is provided during subsequent calls to
2084 @samp{start} or @samp{run}.
2086 It is sometimes necessary to debug the program during elaboration. In
2087 these cases, using the @code{start} command would stop the execution of
2088 your program too late, as the program would have already completed the
2089 elaboration phase. Under these circumstances, insert breakpoints in your
2090 elaboration code before running your program.
2092 @anchor{set exec-wrapper}
2093 @kindex set exec-wrapper
2094 @item set exec-wrapper @var{wrapper}
2095 @itemx show exec-wrapper
2096 @itemx unset exec-wrapper
2097 When @samp{exec-wrapper} is set, the specified wrapper is used to
2098 launch programs for debugging. @value{GDBN} starts your program
2099 with a shell command of the form @kbd{exec @var{wrapper}
2100 @var{program}}. Quoting is added to @var{program} and its
2101 arguments, but not to @var{wrapper}, so you should add quotes if
2102 appropriate for your shell. The wrapper runs until it executes
2103 your program, and then @value{GDBN} takes control.
2105 You can use any program that eventually calls @code{execve} with
2106 its arguments as a wrapper. Several standard Unix utilities do
2107 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2108 with @code{exec "$@@"} will also work.
2110 For example, you can use @code{env} to pass an environment variable to
2111 the debugged program, without setting the variable in your shell's
2115 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2119 This command is available when debugging locally on most targets, excluding
2120 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2122 @kindex set startup-with-shell
2123 @item set startup-with-shell
2124 @itemx set startup-with-shell on
2125 @itemx set startup-with-shell off
2126 @itemx show set startup-with-shell
2127 On Unix systems, by default, if a shell is available on your target,
2128 @value{GDBN}) uses it to start your program. Arguments of the
2129 @code{run} command are passed to the shell, which does variable
2130 substitution, expands wildcard characters and performs redirection of
2131 I/O. In some circumstances, it may be useful to disable such use of a
2132 shell, for example, when debugging the shell itself or diagnosing
2133 startup failures such as:
2137 Starting program: ./a.out
2138 During startup program terminated with signal SIGSEGV, Segmentation fault.
2142 which indicates the shell or the wrapper specified with
2143 @samp{exec-wrapper} crashed, not your program. Most often, this is
2144 caused by something odd in your shell's non-interactive mode
2145 initialization file---such as @file{.cshrc} for C-shell,
2146 $@file{.zshenv} for the Z shell, or the file specified in the
2147 @samp{BASH_ENV} environment variable for BASH.
2149 @kindex set disable-randomization
2150 @item set disable-randomization
2151 @itemx set disable-randomization on
2152 This option (enabled by default in @value{GDBN}) will turn off the native
2153 randomization of the virtual address space of the started program. This option
2154 is useful for multiple debugging sessions to make the execution better
2155 reproducible and memory addresses reusable across debugging sessions.
2157 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2158 On @sc{gnu}/Linux you can get the same behavior using
2161 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2164 @item set disable-randomization off
2165 Leave the behavior of the started executable unchanged. Some bugs rear their
2166 ugly heads only when the program is loaded at certain addresses. If your bug
2167 disappears when you run the program under @value{GDBN}, that might be because
2168 @value{GDBN} by default disables the address randomization on platforms, such
2169 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2170 disable-randomization off} to try to reproduce such elusive bugs.
2172 On targets where it is available, virtual address space randomization
2173 protects the programs against certain kinds of security attacks. In these
2174 cases the attacker needs to know the exact location of a concrete executable
2175 code. Randomizing its location makes it impossible to inject jumps misusing
2176 a code at its expected addresses.
2178 Prelinking shared libraries provides a startup performance advantage but it
2179 makes addresses in these libraries predictable for privileged processes by
2180 having just unprivileged access at the target system. Reading the shared
2181 library binary gives enough information for assembling the malicious code
2182 misusing it. Still even a prelinked shared library can get loaded at a new
2183 random address just requiring the regular relocation process during the
2184 startup. Shared libraries not already prelinked are always loaded at
2185 a randomly chosen address.
2187 Position independent executables (PIE) contain position independent code
2188 similar to the shared libraries and therefore such executables get loaded at
2189 a randomly chosen address upon startup. PIE executables always load even
2190 already prelinked shared libraries at a random address. You can build such
2191 executable using @command{gcc -fPIE -pie}.
2193 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2194 (as long as the randomization is enabled).
2196 @item show disable-randomization
2197 Show the current setting of the explicit disable of the native randomization of
2198 the virtual address space of the started program.
2203 @section Your Program's Arguments
2205 @cindex arguments (to your program)
2206 The arguments to your program can be specified by the arguments of the
2208 They are passed to a shell, which expands wildcard characters and
2209 performs redirection of I/O, and thence to your program. Your
2210 @code{SHELL} environment variable (if it exists) specifies what shell
2211 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2212 the default shell (@file{/bin/sh} on Unix).
2214 On non-Unix systems, the program is usually invoked directly by
2215 @value{GDBN}, which emulates I/O redirection via the appropriate system
2216 calls, and the wildcard characters are expanded by the startup code of
2217 the program, not by the shell.
2219 @code{run} with no arguments uses the same arguments used by the previous
2220 @code{run}, or those set by the @code{set args} command.
2225 Specify the arguments to be used the next time your program is run. If
2226 @code{set args} has no arguments, @code{run} executes your program
2227 with no arguments. Once you have run your program with arguments,
2228 using @code{set args} before the next @code{run} is the only way to run
2229 it again without arguments.
2233 Show the arguments to give your program when it is started.
2237 @section Your Program's Environment
2239 @cindex environment (of your program)
2240 The @dfn{environment} consists of a set of environment variables and
2241 their values. Environment variables conventionally record such things as
2242 your user name, your home directory, your terminal type, and your search
2243 path for programs to run. Usually you set up environment variables with
2244 the shell and they are inherited by all the other programs you run. When
2245 debugging, it can be useful to try running your program with a modified
2246 environment without having to start @value{GDBN} over again.
2250 @item path @var{directory}
2251 Add @var{directory} to the front of the @code{PATH} environment variable
2252 (the search path for executables) that will be passed to your program.
2253 The value of @code{PATH} used by @value{GDBN} does not change.
2254 You may specify several directory names, separated by whitespace or by a
2255 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2256 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2257 is moved to the front, so it is searched sooner.
2259 You can use the string @samp{$cwd} to refer to whatever is the current
2260 working directory at the time @value{GDBN} searches the path. If you
2261 use @samp{.} instead, it refers to the directory where you executed the
2262 @code{path} command. @value{GDBN} replaces @samp{.} in the
2263 @var{directory} argument (with the current path) before adding
2264 @var{directory} to the search path.
2265 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2266 @c document that, since repeating it would be a no-op.
2270 Display the list of search paths for executables (the @code{PATH}
2271 environment variable).
2273 @kindex show environment
2274 @item show environment @r{[}@var{varname}@r{]}
2275 Print the value of environment variable @var{varname} to be given to
2276 your program when it starts. If you do not supply @var{varname},
2277 print the names and values of all environment variables to be given to
2278 your program. You can abbreviate @code{environment} as @code{env}.
2280 @kindex set environment
2281 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2282 Set environment variable @var{varname} to @var{value}. The value
2283 changes for your program (and the shell @value{GDBN} uses to launch
2284 it), not for @value{GDBN} itself. @var{value} may be any string; the
2285 values of environment variables are just strings, and any
2286 interpretation is supplied by your program itself. The @var{value}
2287 parameter is optional; if it is eliminated, the variable is set to a
2289 @c "any string" here does not include leading, trailing
2290 @c blanks. Gnu asks: does anyone care?
2292 For example, this command:
2299 tells the debugged program, when subsequently run, that its user is named
2300 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2301 are not actually required.)
2303 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2304 which also inherits the environment set with @code{set environment}.
2305 If necessary, you can avoid that by using the @samp{env} program as a
2306 wrapper instead of using @code{set environment}. @xref{set
2307 exec-wrapper}, for an example doing just that.
2309 @kindex unset environment
2310 @item unset environment @var{varname}
2311 Remove variable @var{varname} from the environment to be passed to your
2312 program. This is different from @samp{set env @var{varname} =};
2313 @code{unset environment} removes the variable from the environment,
2314 rather than assigning it an empty value.
2317 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2318 the shell indicated by your @code{SHELL} environment variable if it
2319 exists (or @code{/bin/sh} if not). If your @code{SHELL} variable
2320 names a shell that runs an initialization file when started
2321 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2322 for the Z shell, or the file specified in the @samp{BASH_ENV}
2323 environment variable for BASH---any variables you set in that file
2324 affect your program. You may wish to move setting of environment
2325 variables to files that are only run when you sign on, such as
2326 @file{.login} or @file{.profile}.
2328 @node Working Directory
2329 @section Your Program's Working Directory
2331 @cindex working directory (of your program)
2332 Each time you start your program with @code{run}, it inherits its
2333 working directory from the current working directory of @value{GDBN}.
2334 The @value{GDBN} working directory is initially whatever it inherited
2335 from its parent process (typically the shell), but you can specify a new
2336 working directory in @value{GDBN} with the @code{cd} command.
2338 The @value{GDBN} working directory also serves as a default for the commands
2339 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2344 @cindex change working directory
2345 @item cd @r{[}@var{directory}@r{]}
2346 Set the @value{GDBN} working directory to @var{directory}. If not
2347 given, @var{directory} uses @file{'~'}.
2351 Print the @value{GDBN} working directory.
2354 It is generally impossible to find the current working directory of
2355 the process being debugged (since a program can change its directory
2356 during its run). If you work on a system where @value{GDBN} is
2357 configured with the @file{/proc} support, you can use the @code{info
2358 proc} command (@pxref{SVR4 Process Information}) to find out the
2359 current working directory of the debuggee.
2362 @section Your Program's Input and Output
2367 By default, the program you run under @value{GDBN} does input and output to
2368 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2369 to its own terminal modes to interact with you, but it records the terminal
2370 modes your program was using and switches back to them when you continue
2371 running your program.
2374 @kindex info terminal
2376 Displays information recorded by @value{GDBN} about the terminal modes your
2380 You can redirect your program's input and/or output using shell
2381 redirection with the @code{run} command. For example,
2388 starts your program, diverting its output to the file @file{outfile}.
2391 @cindex controlling terminal
2392 Another way to specify where your program should do input and output is
2393 with the @code{tty} command. This command accepts a file name as
2394 argument, and causes this file to be the default for future @code{run}
2395 commands. It also resets the controlling terminal for the child
2396 process, for future @code{run} commands. For example,
2403 directs that processes started with subsequent @code{run} commands
2404 default to do input and output on the terminal @file{/dev/ttyb} and have
2405 that as their controlling terminal.
2407 An explicit redirection in @code{run} overrides the @code{tty} command's
2408 effect on the input/output device, but not its effect on the controlling
2411 When you use the @code{tty} command or redirect input in the @code{run}
2412 command, only the input @emph{for your program} is affected. The input
2413 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2414 for @code{set inferior-tty}.
2416 @cindex inferior tty
2417 @cindex set inferior controlling terminal
2418 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2419 display the name of the terminal that will be used for future runs of your
2423 @item set inferior-tty /dev/ttyb
2424 @kindex set inferior-tty
2425 Set the tty for the program being debugged to /dev/ttyb.
2427 @item show inferior-tty
2428 @kindex show inferior-tty
2429 Show the current tty for the program being debugged.
2433 @section Debugging an Already-running Process
2438 @item attach @var{process-id}
2439 This command attaches to a running process---one that was started
2440 outside @value{GDBN}. (@code{info files} shows your active
2441 targets.) The command takes as argument a process ID. The usual way to
2442 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2443 or with the @samp{jobs -l} shell command.
2445 @code{attach} does not repeat if you press @key{RET} a second time after
2446 executing the command.
2449 To use @code{attach}, your program must be running in an environment
2450 which supports processes; for example, @code{attach} does not work for
2451 programs on bare-board targets that lack an operating system. You must
2452 also have permission to send the process a signal.
2454 When you use @code{attach}, the debugger finds the program running in
2455 the process first by looking in the current working directory, then (if
2456 the program is not found) by using the source file search path
2457 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2458 the @code{file} command to load the program. @xref{Files, ,Commands to
2461 The first thing @value{GDBN} does after arranging to debug the specified
2462 process is to stop it. You can examine and modify an attached process
2463 with all the @value{GDBN} commands that are ordinarily available when
2464 you start processes with @code{run}. You can insert breakpoints; you
2465 can step and continue; you can modify storage. If you would rather the
2466 process continue running, you may use the @code{continue} command after
2467 attaching @value{GDBN} to the process.
2472 When you have finished debugging the attached process, you can use the
2473 @code{detach} command to release it from @value{GDBN} control. Detaching
2474 the process continues its execution. After the @code{detach} command,
2475 that process and @value{GDBN} become completely independent once more, and you
2476 are ready to @code{attach} another process or start one with @code{run}.
2477 @code{detach} does not repeat if you press @key{RET} again after
2478 executing the command.
2481 If you exit @value{GDBN} while you have an attached process, you detach
2482 that process. If you use the @code{run} command, you kill that process.
2483 By default, @value{GDBN} asks for confirmation if you try to do either of these
2484 things; you can control whether or not you need to confirm by using the
2485 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2489 @section Killing the Child Process
2494 Kill the child process in which your program is running under @value{GDBN}.
2497 This command is useful if you wish to debug a core dump instead of a
2498 running process. @value{GDBN} ignores any core dump file while your program
2501 On some operating systems, a program cannot be executed outside @value{GDBN}
2502 while you have breakpoints set on it inside @value{GDBN}. You can use the
2503 @code{kill} command in this situation to permit running your program
2504 outside the debugger.
2506 The @code{kill} command is also useful if you wish to recompile and
2507 relink your program, since on many systems it is impossible to modify an
2508 executable file while it is running in a process. In this case, when you
2509 next type @code{run}, @value{GDBN} notices that the file has changed, and
2510 reads the symbol table again (while trying to preserve your current
2511 breakpoint settings).
2513 @node Inferiors and Programs
2514 @section Debugging Multiple Inferiors and Programs
2516 @value{GDBN} lets you run and debug multiple programs in a single
2517 session. In addition, @value{GDBN} on some systems may let you run
2518 several programs simultaneously (otherwise you have to exit from one
2519 before starting another). In the most general case, you can have
2520 multiple threads of execution in each of multiple processes, launched
2521 from multiple executables.
2524 @value{GDBN} represents the state of each program execution with an
2525 object called an @dfn{inferior}. An inferior typically corresponds to
2526 a process, but is more general and applies also to targets that do not
2527 have processes. Inferiors may be created before a process runs, and
2528 may be retained after a process exits. Inferiors have unique
2529 identifiers that are different from process ids. Usually each
2530 inferior will also have its own distinct address space, although some
2531 embedded targets may have several inferiors running in different parts
2532 of a single address space. Each inferior may in turn have multiple
2533 threads running in it.
2535 To find out what inferiors exist at any moment, use @w{@code{info
2539 @kindex info inferiors
2540 @item info inferiors
2541 Print a list of all inferiors currently being managed by @value{GDBN}.
2543 @value{GDBN} displays for each inferior (in this order):
2547 the inferior number assigned by @value{GDBN}
2550 the target system's inferior identifier
2553 the name of the executable the inferior is running.
2558 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2559 indicates the current inferior.
2563 @c end table here to get a little more width for example
2566 (@value{GDBP}) info inferiors
2567 Num Description Executable
2568 2 process 2307 hello
2569 * 1 process 3401 goodbye
2572 To switch focus between inferiors, use the @code{inferior} command:
2575 @kindex inferior @var{infno}
2576 @item inferior @var{infno}
2577 Make inferior number @var{infno} the current inferior. The argument
2578 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2579 in the first field of the @samp{info inferiors} display.
2583 You can get multiple executables into a debugging session via the
2584 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2585 systems @value{GDBN} can add inferiors to the debug session
2586 automatically by following calls to @code{fork} and @code{exec}. To
2587 remove inferiors from the debugging session use the
2588 @w{@code{remove-inferiors}} command.
2591 @kindex add-inferior
2592 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2593 Adds @var{n} inferiors to be run using @var{executable} as the
2594 executable. @var{n} defaults to 1. If no executable is specified,
2595 the inferiors begins empty, with no program. You can still assign or
2596 change the program assigned to the inferior at any time by using the
2597 @code{file} command with the executable name as its argument.
2599 @kindex clone-inferior
2600 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2601 Adds @var{n} inferiors ready to execute the same program as inferior
2602 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2603 number of the current inferior. This is a convenient command when you
2604 want to run another instance of the inferior you are debugging.
2607 (@value{GDBP}) info inferiors
2608 Num Description Executable
2609 * 1 process 29964 helloworld
2610 (@value{GDBP}) clone-inferior
2613 (@value{GDBP}) info inferiors
2614 Num Description Executable
2616 * 1 process 29964 helloworld
2619 You can now simply switch focus to inferior 2 and run it.
2621 @kindex remove-inferiors
2622 @item remove-inferiors @var{infno}@dots{}
2623 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2624 possible to remove an inferior that is running with this command. For
2625 those, use the @code{kill} or @code{detach} command first.
2629 To quit debugging one of the running inferiors that is not the current
2630 inferior, you can either detach from it by using the @w{@code{detach
2631 inferior}} command (allowing it to run independently), or kill it
2632 using the @w{@code{kill inferiors}} command:
2635 @kindex detach inferiors @var{infno}@dots{}
2636 @item detach inferior @var{infno}@dots{}
2637 Detach from the inferior or inferiors identified by @value{GDBN}
2638 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2639 still stays on the list of inferiors shown by @code{info inferiors},
2640 but its Description will show @samp{<null>}.
2642 @kindex kill inferiors @var{infno}@dots{}
2643 @item kill inferiors @var{infno}@dots{}
2644 Kill the inferior or inferiors identified by @value{GDBN} inferior
2645 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2646 stays on the list of inferiors shown by @code{info inferiors}, but its
2647 Description will show @samp{<null>}.
2650 After the successful completion of a command such as @code{detach},
2651 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2652 a normal process exit, the inferior is still valid and listed with
2653 @code{info inferiors}, ready to be restarted.
2656 To be notified when inferiors are started or exit under @value{GDBN}'s
2657 control use @w{@code{set print inferior-events}}:
2660 @kindex set print inferior-events
2661 @cindex print messages on inferior start and exit
2662 @item set print inferior-events
2663 @itemx set print inferior-events on
2664 @itemx set print inferior-events off
2665 The @code{set print inferior-events} command allows you to enable or
2666 disable printing of messages when @value{GDBN} notices that new
2667 inferiors have started or that inferiors have exited or have been
2668 detached. By default, these messages will not be printed.
2670 @kindex show print inferior-events
2671 @item show print inferior-events
2672 Show whether messages will be printed when @value{GDBN} detects that
2673 inferiors have started, exited or have been detached.
2676 Many commands will work the same with multiple programs as with a
2677 single program: e.g., @code{print myglobal} will simply display the
2678 value of @code{myglobal} in the current inferior.
2681 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2682 get more info about the relationship of inferiors, programs, address
2683 spaces in a debug session. You can do that with the @w{@code{maint
2684 info program-spaces}} command.
2687 @kindex maint info program-spaces
2688 @item maint info program-spaces
2689 Print a list of all program spaces currently being managed by
2692 @value{GDBN} displays for each program space (in this order):
2696 the program space number assigned by @value{GDBN}
2699 the name of the executable loaded into the program space, with e.g.,
2700 the @code{file} command.
2705 An asterisk @samp{*} preceding the @value{GDBN} program space number
2706 indicates the current program space.
2708 In addition, below each program space line, @value{GDBN} prints extra
2709 information that isn't suitable to display in tabular form. For
2710 example, the list of inferiors bound to the program space.
2713 (@value{GDBP}) maint info program-spaces
2716 Bound inferiors: ID 1 (process 21561)
2720 Here we can see that no inferior is running the program @code{hello},
2721 while @code{process 21561} is running the program @code{goodbye}. On
2722 some targets, it is possible that multiple inferiors are bound to the
2723 same program space. The most common example is that of debugging both
2724 the parent and child processes of a @code{vfork} call. For example,
2727 (@value{GDBP}) maint info program-spaces
2730 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2733 Here, both inferior 2 and inferior 1 are running in the same program
2734 space as a result of inferior 1 having executed a @code{vfork} call.
2738 @section Debugging Programs with Multiple Threads
2740 @cindex threads of execution
2741 @cindex multiple threads
2742 @cindex switching threads
2743 In some operating systems, such as HP-UX and Solaris, a single program
2744 may have more than one @dfn{thread} of execution. The precise semantics
2745 of threads differ from one operating system to another, but in general
2746 the threads of a single program are akin to multiple processes---except
2747 that they share one address space (that is, they can all examine and
2748 modify the same variables). On the other hand, each thread has its own
2749 registers and execution stack, and perhaps private memory.
2751 @value{GDBN} provides these facilities for debugging multi-thread
2755 @item automatic notification of new threads
2756 @item @samp{thread @var{threadno}}, a command to switch among threads
2757 @item @samp{info threads}, a command to inquire about existing threads
2758 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2759 a command to apply a command to a list of threads
2760 @item thread-specific breakpoints
2761 @item @samp{set print thread-events}, which controls printing of
2762 messages on thread start and exit.
2763 @item @samp{set libthread-db-search-path @var{path}}, which lets
2764 the user specify which @code{libthread_db} to use if the default choice
2765 isn't compatible with the program.
2769 @emph{Warning:} These facilities are not yet available on every
2770 @value{GDBN} configuration where the operating system supports threads.
2771 If your @value{GDBN} does not support threads, these commands have no
2772 effect. For example, a system without thread support shows no output
2773 from @samp{info threads}, and always rejects the @code{thread} command,
2777 (@value{GDBP}) info threads
2778 (@value{GDBP}) thread 1
2779 Thread ID 1 not known. Use the "info threads" command to
2780 see the IDs of currently known threads.
2782 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2783 @c doesn't support threads"?
2786 @cindex focus of debugging
2787 @cindex current thread
2788 The @value{GDBN} thread debugging facility allows you to observe all
2789 threads while your program runs---but whenever @value{GDBN} takes
2790 control, one thread in particular is always the focus of debugging.
2791 This thread is called the @dfn{current thread}. Debugging commands show
2792 program information from the perspective of the current thread.
2794 @cindex @code{New} @var{systag} message
2795 @cindex thread identifier (system)
2796 @c FIXME-implementors!! It would be more helpful if the [New...] message
2797 @c included GDB's numeric thread handle, so you could just go to that
2798 @c thread without first checking `info threads'.
2799 Whenever @value{GDBN} detects a new thread in your program, it displays
2800 the target system's identification for the thread with a message in the
2801 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2802 whose form varies depending on the particular system. For example, on
2803 @sc{gnu}/Linux, you might see
2806 [New Thread 0x41e02940 (LWP 25582)]
2810 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2811 the @var{systag} is simply something like @samp{process 368}, with no
2814 @c FIXME!! (1) Does the [New...] message appear even for the very first
2815 @c thread of a program, or does it only appear for the
2816 @c second---i.e.@: when it becomes obvious we have a multithread
2818 @c (2) *Is* there necessarily a first thread always? Or do some
2819 @c multithread systems permit starting a program with multiple
2820 @c threads ab initio?
2822 @cindex thread number
2823 @cindex thread identifier (GDB)
2824 For debugging purposes, @value{GDBN} associates its own thread
2825 number---always a single integer---with each thread in your program.
2828 @kindex info threads
2829 @item info threads @r{[}@var{id}@dots{}@r{]}
2830 Display a summary of all threads currently in your program. Optional
2831 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2832 means to print information only about the specified thread or threads.
2833 @value{GDBN} displays for each thread (in this order):
2837 the thread number assigned by @value{GDBN}
2840 the target system's thread identifier (@var{systag})
2843 the thread's name, if one is known. A thread can either be named by
2844 the user (see @code{thread name}, below), or, in some cases, by the
2848 the current stack frame summary for that thread
2852 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2853 indicates the current thread.
2857 @c end table here to get a little more width for example
2860 (@value{GDBP}) info threads
2862 3 process 35 thread 27 0x34e5 in sigpause ()
2863 2 process 35 thread 23 0x34e5 in sigpause ()
2864 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2868 On Solaris, you can display more information about user threads with a
2869 Solaris-specific command:
2872 @item maint info sol-threads
2873 @kindex maint info sol-threads
2874 @cindex thread info (Solaris)
2875 Display info on Solaris user threads.
2879 @kindex thread @var{threadno}
2880 @item thread @var{threadno}
2881 Make thread number @var{threadno} the current thread. The command
2882 argument @var{threadno} is the internal @value{GDBN} thread number, as
2883 shown in the first field of the @samp{info threads} display.
2884 @value{GDBN} responds by displaying the system identifier of the thread
2885 you selected, and its current stack frame summary:
2888 (@value{GDBP}) thread 2
2889 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2890 #0 some_function (ignore=0x0) at example.c:8
2891 8 printf ("hello\n");
2895 As with the @samp{[New @dots{}]} message, the form of the text after
2896 @samp{Switching to} depends on your system's conventions for identifying
2899 @vindex $_thread@r{, convenience variable}
2900 The debugger convenience variable @samp{$_thread} contains the number
2901 of the current thread. You may find this useful in writing breakpoint
2902 conditional expressions, command scripts, and so forth. See
2903 @xref{Convenience Vars,, Convenience Variables}, for general
2904 information on convenience variables.
2906 @kindex thread apply
2907 @cindex apply command to several threads
2908 @item thread apply [@var{threadno} | all] @var{command}
2909 The @code{thread apply} command allows you to apply the named
2910 @var{command} to one or more threads. Specify the numbers of the
2911 threads that you want affected with the command argument
2912 @var{threadno}. It can be a single thread number, one of the numbers
2913 shown in the first field of the @samp{info threads} display; or it
2914 could be a range of thread numbers, as in @code{2-4}. To apply a
2915 command to all threads, type @kbd{thread apply all @var{command}}.
2918 @cindex name a thread
2919 @item thread name [@var{name}]
2920 This command assigns a name to the current thread. If no argument is
2921 given, any existing user-specified name is removed. The thread name
2922 appears in the @samp{info threads} display.
2924 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
2925 determine the name of the thread as given by the OS. On these
2926 systems, a name specified with @samp{thread name} will override the
2927 system-give name, and removing the user-specified name will cause
2928 @value{GDBN} to once again display the system-specified name.
2931 @cindex search for a thread
2932 @item thread find [@var{regexp}]
2933 Search for and display thread ids whose name or @var{systag}
2934 matches the supplied regular expression.
2936 As well as being the complement to the @samp{thread name} command,
2937 this command also allows you to identify a thread by its target
2938 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
2942 (@value{GDBN}) thread find 26688
2943 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
2944 (@value{GDBN}) info thread 4
2946 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
2949 @kindex set print thread-events
2950 @cindex print messages on thread start and exit
2951 @item set print thread-events
2952 @itemx set print thread-events on
2953 @itemx set print thread-events off
2954 The @code{set print thread-events} command allows you to enable or
2955 disable printing of messages when @value{GDBN} notices that new threads have
2956 started or that threads have exited. By default, these messages will
2957 be printed if detection of these events is supported by the target.
2958 Note that these messages cannot be disabled on all targets.
2960 @kindex show print thread-events
2961 @item show print thread-events
2962 Show whether messages will be printed when @value{GDBN} detects that threads
2963 have started and exited.
2966 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2967 more information about how @value{GDBN} behaves when you stop and start
2968 programs with multiple threads.
2970 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2971 watchpoints in programs with multiple threads.
2973 @anchor{set libthread-db-search-path}
2975 @kindex set libthread-db-search-path
2976 @cindex search path for @code{libthread_db}
2977 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2978 If this variable is set, @var{path} is a colon-separated list of
2979 directories @value{GDBN} will use to search for @code{libthread_db}.
2980 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2981 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
2982 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
2985 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2986 @code{libthread_db} library to obtain information about threads in the
2987 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2988 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
2989 specific thread debugging library loading is enabled
2990 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
2992 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
2993 refers to the default system directories that are
2994 normally searched for loading shared libraries. The @samp{$sdir} entry
2995 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
2996 (@pxref{libthread_db.so.1 file}).
2998 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
2999 refers to the directory from which @code{libpthread}
3000 was loaded in the inferior process.
3002 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3003 @value{GDBN} attempts to initialize it with the current inferior process.
3004 If this initialization fails (which could happen because of a version
3005 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3006 will unload @code{libthread_db}, and continue with the next directory.
3007 If none of @code{libthread_db} libraries initialize successfully,
3008 @value{GDBN} will issue a warning and thread debugging will be disabled.
3010 Setting @code{libthread-db-search-path} is currently implemented
3011 only on some platforms.
3013 @kindex show libthread-db-search-path
3014 @item show libthread-db-search-path
3015 Display current libthread_db search path.
3017 @kindex set debug libthread-db
3018 @kindex show debug libthread-db
3019 @cindex debugging @code{libthread_db}
3020 @item set debug libthread-db
3021 @itemx show debug libthread-db
3022 Turns on or off display of @code{libthread_db}-related events.
3023 Use @code{1} to enable, @code{0} to disable.
3027 @section Debugging Forks
3029 @cindex fork, debugging programs which call
3030 @cindex multiple processes
3031 @cindex processes, multiple
3032 On most systems, @value{GDBN} has no special support for debugging
3033 programs which create additional processes using the @code{fork}
3034 function. When a program forks, @value{GDBN} will continue to debug the
3035 parent process and the child process will run unimpeded. If you have
3036 set a breakpoint in any code which the child then executes, the child
3037 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3038 will cause it to terminate.
3040 However, if you want to debug the child process there is a workaround
3041 which isn't too painful. Put a call to @code{sleep} in the code which
3042 the child process executes after the fork. It may be useful to sleep
3043 only if a certain environment variable is set, or a certain file exists,
3044 so that the delay need not occur when you don't want to run @value{GDBN}
3045 on the child. While the child is sleeping, use the @code{ps} program to
3046 get its process ID. Then tell @value{GDBN} (a new invocation of
3047 @value{GDBN} if you are also debugging the parent process) to attach to
3048 the child process (@pxref{Attach}). From that point on you can debug
3049 the child process just like any other process which you attached to.
3051 On some systems, @value{GDBN} provides support for debugging programs that
3052 create additional processes using the @code{fork} or @code{vfork} functions.
3053 Currently, the only platforms with this feature are HP-UX (11.x and later
3054 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
3056 By default, when a program forks, @value{GDBN} will continue to debug
3057 the parent process and the child process will run unimpeded.
3059 If you want to follow the child process instead of the parent process,
3060 use the command @w{@code{set follow-fork-mode}}.
3063 @kindex set follow-fork-mode
3064 @item set follow-fork-mode @var{mode}
3065 Set the debugger response to a program call of @code{fork} or
3066 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3067 process. The @var{mode} argument can be:
3071 The original process is debugged after a fork. The child process runs
3072 unimpeded. This is the default.
3075 The new process is debugged after a fork. The parent process runs
3080 @kindex show follow-fork-mode
3081 @item show follow-fork-mode
3082 Display the current debugger response to a @code{fork} or @code{vfork} call.
3085 @cindex debugging multiple processes
3086 On Linux, if you want to debug both the parent and child processes, use the
3087 command @w{@code{set detach-on-fork}}.
3090 @kindex set detach-on-fork
3091 @item set detach-on-fork @var{mode}
3092 Tells gdb whether to detach one of the processes after a fork, or
3093 retain debugger control over them both.
3097 The child process (or parent process, depending on the value of
3098 @code{follow-fork-mode}) will be detached and allowed to run
3099 independently. This is the default.
3102 Both processes will be held under the control of @value{GDBN}.
3103 One process (child or parent, depending on the value of
3104 @code{follow-fork-mode}) is debugged as usual, while the other
3109 @kindex show detach-on-fork
3110 @item show detach-on-fork
3111 Show whether detach-on-fork mode is on/off.
3114 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3115 will retain control of all forked processes (including nested forks).
3116 You can list the forked processes under the control of @value{GDBN} by
3117 using the @w{@code{info inferiors}} command, and switch from one fork
3118 to another by using the @code{inferior} command (@pxref{Inferiors and
3119 Programs, ,Debugging Multiple Inferiors and Programs}).
3121 To quit debugging one of the forked processes, you can either detach
3122 from it by using the @w{@code{detach inferiors}} command (allowing it
3123 to run independently), or kill it using the @w{@code{kill inferiors}}
3124 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3127 If you ask to debug a child process and a @code{vfork} is followed by an
3128 @code{exec}, @value{GDBN} executes the new target up to the first
3129 breakpoint in the new target. If you have a breakpoint set on
3130 @code{main} in your original program, the breakpoint will also be set on
3131 the child process's @code{main}.
3133 On some systems, when a child process is spawned by @code{vfork}, you
3134 cannot debug the child or parent until an @code{exec} call completes.
3136 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3137 call executes, the new target restarts. To restart the parent
3138 process, use the @code{file} command with the parent executable name
3139 as its argument. By default, after an @code{exec} call executes,
3140 @value{GDBN} discards the symbols of the previous executable image.
3141 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3145 @kindex set follow-exec-mode
3146 @item set follow-exec-mode @var{mode}
3148 Set debugger response to a program call of @code{exec}. An
3149 @code{exec} call replaces the program image of a process.
3151 @code{follow-exec-mode} can be:
3155 @value{GDBN} creates a new inferior and rebinds the process to this
3156 new inferior. The program the process was running before the
3157 @code{exec} call can be restarted afterwards by restarting the
3163 (@value{GDBP}) info inferiors
3165 Id Description Executable
3168 process 12020 is executing new program: prog2
3169 Program exited normally.
3170 (@value{GDBP}) info inferiors
3171 Id Description Executable
3177 @value{GDBN} keeps the process bound to the same inferior. The new
3178 executable image replaces the previous executable loaded in the
3179 inferior. Restarting the inferior after the @code{exec} call, with
3180 e.g., the @code{run} command, restarts the executable the process was
3181 running after the @code{exec} call. This is the default mode.
3186 (@value{GDBP}) info inferiors
3187 Id Description Executable
3190 process 12020 is executing new program: prog2
3191 Program exited normally.
3192 (@value{GDBP}) info inferiors
3193 Id Description Executable
3200 You can use the @code{catch} command to make @value{GDBN} stop whenever
3201 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3202 Catchpoints, ,Setting Catchpoints}.
3204 @node Checkpoint/Restart
3205 @section Setting a @emph{Bookmark} to Return to Later
3210 @cindex snapshot of a process
3211 @cindex rewind program state
3213 On certain operating systems@footnote{Currently, only
3214 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3215 program's state, called a @dfn{checkpoint}, and come back to it
3218 Returning to a checkpoint effectively undoes everything that has
3219 happened in the program since the @code{checkpoint} was saved. This
3220 includes changes in memory, registers, and even (within some limits)
3221 system state. Effectively, it is like going back in time to the
3222 moment when the checkpoint was saved.
3224 Thus, if you're stepping thru a program and you think you're
3225 getting close to the point where things go wrong, you can save
3226 a checkpoint. Then, if you accidentally go too far and miss
3227 the critical statement, instead of having to restart your program
3228 from the beginning, you can just go back to the checkpoint and
3229 start again from there.
3231 This can be especially useful if it takes a lot of time or
3232 steps to reach the point where you think the bug occurs.
3234 To use the @code{checkpoint}/@code{restart} method of debugging:
3239 Save a snapshot of the debugged program's current execution state.
3240 The @code{checkpoint} command takes no arguments, but each checkpoint
3241 is assigned a small integer id, similar to a breakpoint id.
3243 @kindex info checkpoints
3244 @item info checkpoints
3245 List the checkpoints that have been saved in the current debugging
3246 session. For each checkpoint, the following information will be
3253 @item Source line, or label
3256 @kindex restart @var{checkpoint-id}
3257 @item restart @var{checkpoint-id}
3258 Restore the program state that was saved as checkpoint number
3259 @var{checkpoint-id}. All program variables, registers, stack frames
3260 etc.@: will be returned to the values that they had when the checkpoint
3261 was saved. In essence, gdb will ``wind back the clock'' to the point
3262 in time when the checkpoint was saved.
3264 Note that breakpoints, @value{GDBN} variables, command history etc.
3265 are not affected by restoring a checkpoint. In general, a checkpoint
3266 only restores things that reside in the program being debugged, not in
3269 @kindex delete checkpoint @var{checkpoint-id}
3270 @item delete checkpoint @var{checkpoint-id}
3271 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3275 Returning to a previously saved checkpoint will restore the user state
3276 of the program being debugged, plus a significant subset of the system
3277 (OS) state, including file pointers. It won't ``un-write'' data from
3278 a file, but it will rewind the file pointer to the previous location,
3279 so that the previously written data can be overwritten. For files
3280 opened in read mode, the pointer will also be restored so that the
3281 previously read data can be read again.
3283 Of course, characters that have been sent to a printer (or other
3284 external device) cannot be ``snatched back'', and characters received
3285 from eg.@: a serial device can be removed from internal program buffers,
3286 but they cannot be ``pushed back'' into the serial pipeline, ready to
3287 be received again. Similarly, the actual contents of files that have
3288 been changed cannot be restored (at this time).
3290 However, within those constraints, you actually can ``rewind'' your
3291 program to a previously saved point in time, and begin debugging it
3292 again --- and you can change the course of events so as to debug a
3293 different execution path this time.
3295 @cindex checkpoints and process id
3296 Finally, there is one bit of internal program state that will be
3297 different when you return to a checkpoint --- the program's process
3298 id. Each checkpoint will have a unique process id (or @var{pid}),
3299 and each will be different from the program's original @var{pid}.
3300 If your program has saved a local copy of its process id, this could
3301 potentially pose a problem.
3303 @subsection A Non-obvious Benefit of Using Checkpoints
3305 On some systems such as @sc{gnu}/Linux, address space randomization
3306 is performed on new processes for security reasons. This makes it
3307 difficult or impossible to set a breakpoint, or watchpoint, on an
3308 absolute address if you have to restart the program, since the
3309 absolute location of a symbol will change from one execution to the
3312 A checkpoint, however, is an @emph{identical} copy of a process.
3313 Therefore if you create a checkpoint at (eg.@:) the start of main,
3314 and simply return to that checkpoint instead of restarting the
3315 process, you can avoid the effects of address randomization and
3316 your symbols will all stay in the same place.
3319 @chapter Stopping and Continuing
3321 The principal purposes of using a debugger are so that you can stop your
3322 program before it terminates; or so that, if your program runs into
3323 trouble, you can investigate and find out why.
3325 Inside @value{GDBN}, your program may stop for any of several reasons,
3326 such as a signal, a breakpoint, or reaching a new line after a
3327 @value{GDBN} command such as @code{step}. You may then examine and
3328 change variables, set new breakpoints or remove old ones, and then
3329 continue execution. Usually, the messages shown by @value{GDBN} provide
3330 ample explanation of the status of your program---but you can also
3331 explicitly request this information at any time.
3334 @kindex info program
3336 Display information about the status of your program: whether it is
3337 running or not, what process it is, and why it stopped.
3341 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3342 * Continuing and Stepping:: Resuming execution
3343 * Skipping Over Functions and Files::
3344 Skipping over functions and files
3346 * Thread Stops:: Stopping and starting multi-thread programs
3350 @section Breakpoints, Watchpoints, and Catchpoints
3353 A @dfn{breakpoint} makes your program stop whenever a certain point in
3354 the program is reached. For each breakpoint, you can add conditions to
3355 control in finer detail whether your program stops. You can set
3356 breakpoints with the @code{break} command and its variants (@pxref{Set
3357 Breaks, ,Setting Breakpoints}), to specify the place where your program
3358 should stop by line number, function name or exact address in the
3361 On some systems, you can set breakpoints in shared libraries before
3362 the executable is run. There is a minor limitation on HP-UX systems:
3363 you must wait until the executable is run in order to set breakpoints
3364 in shared library routines that are not called directly by the program
3365 (for example, routines that are arguments in a @code{pthread_create}
3369 @cindex data breakpoints
3370 @cindex memory tracing
3371 @cindex breakpoint on memory address
3372 @cindex breakpoint on variable modification
3373 A @dfn{watchpoint} is a special breakpoint that stops your program
3374 when the value of an expression changes. The expression may be a value
3375 of a variable, or it could involve values of one or more variables
3376 combined by operators, such as @samp{a + b}. This is sometimes called
3377 @dfn{data breakpoints}. You must use a different command to set
3378 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3379 from that, you can manage a watchpoint like any other breakpoint: you
3380 enable, disable, and delete both breakpoints and watchpoints using the
3383 You can arrange to have values from your program displayed automatically
3384 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3388 @cindex breakpoint on events
3389 A @dfn{catchpoint} is another special breakpoint that stops your program
3390 when a certain kind of event occurs, such as the throwing of a C@t{++}
3391 exception or the loading of a library. As with watchpoints, you use a
3392 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3393 Catchpoints}), but aside from that, you can manage a catchpoint like any
3394 other breakpoint. (To stop when your program receives a signal, use the
3395 @code{handle} command; see @ref{Signals, ,Signals}.)
3397 @cindex breakpoint numbers
3398 @cindex numbers for breakpoints
3399 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3400 catchpoint when you create it; these numbers are successive integers
3401 starting with one. In many of the commands for controlling various
3402 features of breakpoints you use the breakpoint number to say which
3403 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3404 @dfn{disabled}; if disabled, it has no effect on your program until you
3407 @cindex breakpoint ranges
3408 @cindex ranges of breakpoints
3409 Some @value{GDBN} commands accept a range of breakpoints on which to
3410 operate. A breakpoint range is either a single breakpoint number, like
3411 @samp{5}, or two such numbers, in increasing order, separated by a
3412 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3413 all breakpoints in that range are operated on.
3416 * Set Breaks:: Setting breakpoints
3417 * Set Watchpoints:: Setting watchpoints
3418 * Set Catchpoints:: Setting catchpoints
3419 * Delete Breaks:: Deleting breakpoints
3420 * Disabling:: Disabling breakpoints
3421 * Conditions:: Break conditions
3422 * Break Commands:: Breakpoint command lists
3423 * Dynamic Printf:: Dynamic printf
3424 * Save Breakpoints:: How to save breakpoints in a file
3425 * Static Probe Points:: Listing static probe points
3426 * Error in Breakpoints:: ``Cannot insert breakpoints''
3427 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3431 @subsection Setting Breakpoints
3433 @c FIXME LMB what does GDB do if no code on line of breakpt?
3434 @c consider in particular declaration with/without initialization.
3436 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3439 @kindex b @r{(@code{break})}
3440 @vindex $bpnum@r{, convenience variable}
3441 @cindex latest breakpoint
3442 Breakpoints are set with the @code{break} command (abbreviated
3443 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3444 number of the breakpoint you've set most recently; see @ref{Convenience
3445 Vars,, Convenience Variables}, for a discussion of what you can do with
3446 convenience variables.
3449 @item break @var{location}
3450 Set a breakpoint at the given @var{location}, which can specify a
3451 function name, a line number, or an address of an instruction.
3452 (@xref{Specify Location}, for a list of all the possible ways to
3453 specify a @var{location}.) The breakpoint will stop your program just
3454 before it executes any of the code in the specified @var{location}.
3456 When using source languages that permit overloading of symbols, such as
3457 C@t{++}, a function name may refer to more than one possible place to break.
3458 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3461 It is also possible to insert a breakpoint that will stop the program
3462 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3463 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3466 When called without any arguments, @code{break} sets a breakpoint at
3467 the next instruction to be executed in the selected stack frame
3468 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3469 innermost, this makes your program stop as soon as control
3470 returns to that frame. This is similar to the effect of a
3471 @code{finish} command in the frame inside the selected frame---except
3472 that @code{finish} does not leave an active breakpoint. If you use
3473 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3474 the next time it reaches the current location; this may be useful
3477 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3478 least one instruction has been executed. If it did not do this, you
3479 would be unable to proceed past a breakpoint without first disabling the
3480 breakpoint. This rule applies whether or not the breakpoint already
3481 existed when your program stopped.
3483 @item break @dots{} if @var{cond}
3484 Set a breakpoint with condition @var{cond}; evaluate the expression
3485 @var{cond} each time the breakpoint is reached, and stop only if the
3486 value is nonzero---that is, if @var{cond} evaluates as true.
3487 @samp{@dots{}} stands for one of the possible arguments described
3488 above (or no argument) specifying where to break. @xref{Conditions,
3489 ,Break Conditions}, for more information on breakpoint conditions.
3492 @item tbreak @var{args}
3493 Set a breakpoint enabled only for one stop. @var{args} are the
3494 same as for the @code{break} command, and the breakpoint is set in the same
3495 way, but the breakpoint is automatically deleted after the first time your
3496 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3499 @cindex hardware breakpoints
3500 @item hbreak @var{args}
3501 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3502 @code{break} command and the breakpoint is set in the same way, but the
3503 breakpoint requires hardware support and some target hardware may not
3504 have this support. The main purpose of this is EPROM/ROM code
3505 debugging, so you can set a breakpoint at an instruction without
3506 changing the instruction. This can be used with the new trap-generation
3507 provided by SPARClite DSU and most x86-based targets. These targets
3508 will generate traps when a program accesses some data or instruction
3509 address that is assigned to the debug registers. However the hardware
3510 breakpoint registers can take a limited number of breakpoints. For
3511 example, on the DSU, only two data breakpoints can be set at a time, and
3512 @value{GDBN} will reject this command if more than two are used. Delete
3513 or disable unused hardware breakpoints before setting new ones
3514 (@pxref{Disabling, ,Disabling Breakpoints}).
3515 @xref{Conditions, ,Break Conditions}.
3516 For remote targets, you can restrict the number of hardware
3517 breakpoints @value{GDBN} will use, see @ref{set remote
3518 hardware-breakpoint-limit}.
3521 @item thbreak @var{args}
3522 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3523 are the same as for the @code{hbreak} command and the breakpoint is set in
3524 the same way. However, like the @code{tbreak} command,
3525 the breakpoint is automatically deleted after the
3526 first time your program stops there. Also, like the @code{hbreak}
3527 command, the breakpoint requires hardware support and some target hardware
3528 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3529 See also @ref{Conditions, ,Break Conditions}.
3532 @cindex regular expression
3533 @cindex breakpoints at functions matching a regexp
3534 @cindex set breakpoints in many functions
3535 @item rbreak @var{regex}
3536 Set breakpoints on all functions matching the regular expression
3537 @var{regex}. This command sets an unconditional breakpoint on all
3538 matches, printing a list of all breakpoints it set. Once these
3539 breakpoints are set, they are treated just like the breakpoints set with
3540 the @code{break} command. You can delete them, disable them, or make
3541 them conditional the same way as any other breakpoint.
3543 The syntax of the regular expression is the standard one used with tools
3544 like @file{grep}. Note that this is different from the syntax used by
3545 shells, so for instance @code{foo*} matches all functions that include
3546 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3547 @code{.*} leading and trailing the regular expression you supply, so to
3548 match only functions that begin with @code{foo}, use @code{^foo}.
3550 @cindex non-member C@t{++} functions, set breakpoint in
3551 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3552 breakpoints on overloaded functions that are not members of any special
3555 @cindex set breakpoints on all functions
3556 The @code{rbreak} command can be used to set breakpoints in
3557 @strong{all} the functions in a program, like this:
3560 (@value{GDBP}) rbreak .
3563 @item rbreak @var{file}:@var{regex}
3564 If @code{rbreak} is called with a filename qualification, it limits
3565 the search for functions matching the given regular expression to the
3566 specified @var{file}. This can be used, for example, to set breakpoints on
3567 every function in a given file:
3570 (@value{GDBP}) rbreak file.c:.
3573 The colon separating the filename qualifier from the regex may
3574 optionally be surrounded by spaces.
3576 @kindex info breakpoints
3577 @cindex @code{$_} and @code{info breakpoints}
3578 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3579 @itemx info break @r{[}@var{n}@dots{}@r{]}
3580 Print a table of all breakpoints, watchpoints, and catchpoints set and
3581 not deleted. Optional argument @var{n} means print information only
3582 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3583 For each breakpoint, following columns are printed:
3586 @item Breakpoint Numbers
3588 Breakpoint, watchpoint, or catchpoint.
3590 Whether the breakpoint is marked to be disabled or deleted when hit.
3591 @item Enabled or Disabled
3592 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3593 that are not enabled.
3595 Where the breakpoint is in your program, as a memory address. For a
3596 pending breakpoint whose address is not yet known, this field will
3597 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3598 library that has the symbol or line referred by breakpoint is loaded.
3599 See below for details. A breakpoint with several locations will
3600 have @samp{<MULTIPLE>} in this field---see below for details.
3602 Where the breakpoint is in the source for your program, as a file and
3603 line number. For a pending breakpoint, the original string passed to
3604 the breakpoint command will be listed as it cannot be resolved until
3605 the appropriate shared library is loaded in the future.
3609 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3610 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3611 @value{GDBN} on the host's side. If it is ``target'', then the condition
3612 is evaluated by the target. The @code{info break} command shows
3613 the condition on the line following the affected breakpoint, together with
3614 its condition evaluation mode in between parentheses.
3616 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3617 allowed to have a condition specified for it. The condition is not parsed for
3618 validity until a shared library is loaded that allows the pending
3619 breakpoint to resolve to a valid location.
3622 @code{info break} with a breakpoint
3623 number @var{n} as argument lists only that breakpoint. The
3624 convenience variable @code{$_} and the default examining-address for
3625 the @code{x} command are set to the address of the last breakpoint
3626 listed (@pxref{Memory, ,Examining Memory}).
3629 @code{info break} displays a count of the number of times the breakpoint
3630 has been hit. This is especially useful in conjunction with the
3631 @code{ignore} command. You can ignore a large number of breakpoint
3632 hits, look at the breakpoint info to see how many times the breakpoint
3633 was hit, and then run again, ignoring one less than that number. This
3634 will get you quickly to the last hit of that breakpoint.
3637 For a breakpoints with an enable count (xref) greater than 1,
3638 @code{info break} also displays that count.
3642 @value{GDBN} allows you to set any number of breakpoints at the same place in
3643 your program. There is nothing silly or meaningless about this. When
3644 the breakpoints are conditional, this is even useful
3645 (@pxref{Conditions, ,Break Conditions}).
3647 @cindex multiple locations, breakpoints
3648 @cindex breakpoints, multiple locations
3649 It is possible that a breakpoint corresponds to several locations
3650 in your program. Examples of this situation are:
3654 Multiple functions in the program may have the same name.
3657 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3658 instances of the function body, used in different cases.
3661 For a C@t{++} template function, a given line in the function can
3662 correspond to any number of instantiations.
3665 For an inlined function, a given source line can correspond to
3666 several places where that function is inlined.
3669 In all those cases, @value{GDBN} will insert a breakpoint at all
3670 the relevant locations.
3672 A breakpoint with multiple locations is displayed in the breakpoint
3673 table using several rows---one header row, followed by one row for
3674 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3675 address column. The rows for individual locations contain the actual
3676 addresses for locations, and show the functions to which those
3677 locations belong. The number column for a location is of the form
3678 @var{breakpoint-number}.@var{location-number}.
3683 Num Type Disp Enb Address What
3684 1 breakpoint keep y <MULTIPLE>
3686 breakpoint already hit 1 time
3687 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3688 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3691 Each location can be individually enabled or disabled by passing
3692 @var{breakpoint-number}.@var{location-number} as argument to the
3693 @code{enable} and @code{disable} commands. Note that you cannot
3694 delete the individual locations from the list, you can only delete the
3695 entire list of locations that belong to their parent breakpoint (with
3696 the @kbd{delete @var{num}} command, where @var{num} is the number of
3697 the parent breakpoint, 1 in the above example). Disabling or enabling
3698 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3699 that belong to that breakpoint.
3701 @cindex pending breakpoints
3702 It's quite common to have a breakpoint inside a shared library.
3703 Shared libraries can be loaded and unloaded explicitly,
3704 and possibly repeatedly, as the program is executed. To support
3705 this use case, @value{GDBN} updates breakpoint locations whenever
3706 any shared library is loaded or unloaded. Typically, you would
3707 set a breakpoint in a shared library at the beginning of your
3708 debugging session, when the library is not loaded, and when the
3709 symbols from the library are not available. When you try to set
3710 breakpoint, @value{GDBN} will ask you if you want to set
3711 a so called @dfn{pending breakpoint}---breakpoint whose address
3712 is not yet resolved.
3714 After the program is run, whenever a new shared library is loaded,
3715 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3716 shared library contains the symbol or line referred to by some
3717 pending breakpoint, that breakpoint is resolved and becomes an
3718 ordinary breakpoint. When a library is unloaded, all breakpoints
3719 that refer to its symbols or source lines become pending again.
3721 This logic works for breakpoints with multiple locations, too. For
3722 example, if you have a breakpoint in a C@t{++} template function, and
3723 a newly loaded shared library has an instantiation of that template,
3724 a new location is added to the list of locations for the breakpoint.
3726 Except for having unresolved address, pending breakpoints do not
3727 differ from regular breakpoints. You can set conditions or commands,
3728 enable and disable them and perform other breakpoint operations.
3730 @value{GDBN} provides some additional commands for controlling what
3731 happens when the @samp{break} command cannot resolve breakpoint
3732 address specification to an address:
3734 @kindex set breakpoint pending
3735 @kindex show breakpoint pending
3737 @item set breakpoint pending auto
3738 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3739 location, it queries you whether a pending breakpoint should be created.
3741 @item set breakpoint pending on
3742 This indicates that an unrecognized breakpoint location should automatically
3743 result in a pending breakpoint being created.
3745 @item set breakpoint pending off
3746 This indicates that pending breakpoints are not to be created. Any
3747 unrecognized breakpoint location results in an error. This setting does
3748 not affect any pending breakpoints previously created.
3750 @item show breakpoint pending
3751 Show the current behavior setting for creating pending breakpoints.
3754 The settings above only affect the @code{break} command and its
3755 variants. Once breakpoint is set, it will be automatically updated
3756 as shared libraries are loaded and unloaded.
3758 @cindex automatic hardware breakpoints
3759 For some targets, @value{GDBN} can automatically decide if hardware or
3760 software breakpoints should be used, depending on whether the
3761 breakpoint address is read-only or read-write. This applies to
3762 breakpoints set with the @code{break} command as well as to internal
3763 breakpoints set by commands like @code{next} and @code{finish}. For
3764 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3767 You can control this automatic behaviour with the following commands::
3769 @kindex set breakpoint auto-hw
3770 @kindex show breakpoint auto-hw
3772 @item set breakpoint auto-hw on
3773 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3774 will try to use the target memory map to decide if software or hardware
3775 breakpoint must be used.
3777 @item set breakpoint auto-hw off
3778 This indicates @value{GDBN} should not automatically select breakpoint
3779 type. If the target provides a memory map, @value{GDBN} will warn when
3780 trying to set software breakpoint at a read-only address.
3783 @value{GDBN} normally implements breakpoints by replacing the program code
3784 at the breakpoint address with a special instruction, which, when
3785 executed, given control to the debugger. By default, the program
3786 code is so modified only when the program is resumed. As soon as
3787 the program stops, @value{GDBN} restores the original instructions. This
3788 behaviour guards against leaving breakpoints inserted in the
3789 target should gdb abrubptly disconnect. However, with slow remote
3790 targets, inserting and removing breakpoint can reduce the performance.
3791 This behavior can be controlled with the following commands::
3793 @kindex set breakpoint always-inserted
3794 @kindex show breakpoint always-inserted
3796 @item set breakpoint always-inserted off
3797 All breakpoints, including newly added by the user, are inserted in
3798 the target only when the target is resumed. All breakpoints are
3799 removed from the target when it stops.
3801 @item set breakpoint always-inserted on
3802 Causes all breakpoints to be inserted in the target at all times. If
3803 the user adds a new breakpoint, or changes an existing breakpoint, the
3804 breakpoints in the target are updated immediately. A breakpoint is
3805 removed from the target only when breakpoint itself is removed.
3807 @cindex non-stop mode, and @code{breakpoint always-inserted}
3808 @item set breakpoint always-inserted auto
3809 This is the default mode. If @value{GDBN} is controlling the inferior
3810 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3811 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3812 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3813 @code{breakpoint always-inserted} mode is off.
3816 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3817 when a breakpoint breaks. If the condition is true, then the process being
3818 debugged stops, otherwise the process is resumed.
3820 If the target supports evaluating conditions on its end, @value{GDBN} may
3821 download the breakpoint, together with its conditions, to it.
3823 This feature can be controlled via the following commands:
3825 @kindex set breakpoint condition-evaluation
3826 @kindex show breakpoint condition-evaluation
3828 @item set breakpoint condition-evaluation host
3829 This option commands @value{GDBN} to evaluate the breakpoint
3830 conditions on the host's side. Unconditional breakpoints are sent to
3831 the target which in turn receives the triggers and reports them back to GDB
3832 for condition evaluation. This is the standard evaluation mode.
3834 @item set breakpoint condition-evaluation target
3835 This option commands @value{GDBN} to download breakpoint conditions
3836 to the target at the moment of their insertion. The target
3837 is responsible for evaluating the conditional expression and reporting
3838 breakpoint stop events back to @value{GDBN} whenever the condition
3839 is true. Due to limitations of target-side evaluation, some conditions
3840 cannot be evaluated there, e.g., conditions that depend on local data
3841 that is only known to the host. Examples include
3842 conditional expressions involving convenience variables, complex types
3843 that cannot be handled by the agent expression parser and expressions
3844 that are too long to be sent over to the target, specially when the
3845 target is a remote system. In these cases, the conditions will be
3846 evaluated by @value{GDBN}.
3848 @item set breakpoint condition-evaluation auto
3849 This is the default mode. If the target supports evaluating breakpoint
3850 conditions on its end, @value{GDBN} will download breakpoint conditions to
3851 the target (limitations mentioned previously apply). If the target does
3852 not support breakpoint condition evaluation, then @value{GDBN} will fallback
3853 to evaluating all these conditions on the host's side.
3857 @cindex negative breakpoint numbers
3858 @cindex internal @value{GDBN} breakpoints
3859 @value{GDBN} itself sometimes sets breakpoints in your program for
3860 special purposes, such as proper handling of @code{longjmp} (in C
3861 programs). These internal breakpoints are assigned negative numbers,
3862 starting with @code{-1}; @samp{info breakpoints} does not display them.
3863 You can see these breakpoints with the @value{GDBN} maintenance command
3864 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3867 @node Set Watchpoints
3868 @subsection Setting Watchpoints
3870 @cindex setting watchpoints
3871 You can use a watchpoint to stop execution whenever the value of an
3872 expression changes, without having to predict a particular place where
3873 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3874 The expression may be as simple as the value of a single variable, or
3875 as complex as many variables combined by operators. Examples include:
3879 A reference to the value of a single variable.
3882 An address cast to an appropriate data type. For example,
3883 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3884 address (assuming an @code{int} occupies 4 bytes).
3887 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3888 expression can use any operators valid in the program's native
3889 language (@pxref{Languages}).
3892 You can set a watchpoint on an expression even if the expression can
3893 not be evaluated yet. For instance, you can set a watchpoint on
3894 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3895 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3896 the expression produces a valid value. If the expression becomes
3897 valid in some other way than changing a variable (e.g.@: if the memory
3898 pointed to by @samp{*global_ptr} becomes readable as the result of a
3899 @code{malloc} call), @value{GDBN} may not stop until the next time
3900 the expression changes.
3902 @cindex software watchpoints
3903 @cindex hardware watchpoints
3904 Depending on your system, watchpoints may be implemented in software or
3905 hardware. @value{GDBN} does software watchpointing by single-stepping your
3906 program and testing the variable's value each time, which is hundreds of
3907 times slower than normal execution. (But this may still be worth it, to
3908 catch errors where you have no clue what part of your program is the
3911 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3912 x86-based targets, @value{GDBN} includes support for hardware
3913 watchpoints, which do not slow down the running of your program.
3917 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3918 Set a watchpoint for an expression. @value{GDBN} will break when the
3919 expression @var{expr} is written into by the program and its value
3920 changes. The simplest (and the most popular) use of this command is
3921 to watch the value of a single variable:
3924 (@value{GDBP}) watch foo
3927 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3928 argument, @value{GDBN} breaks only when the thread identified by
3929 @var{threadnum} changes the value of @var{expr}. If any other threads
3930 change the value of @var{expr}, @value{GDBN} will not break. Note
3931 that watchpoints restricted to a single thread in this way only work
3932 with Hardware Watchpoints.
3934 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3935 (see below). The @code{-location} argument tells @value{GDBN} to
3936 instead watch the memory referred to by @var{expr}. In this case,
3937 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3938 and watch the memory at that address. The type of the result is used
3939 to determine the size of the watched memory. If the expression's
3940 result does not have an address, then @value{GDBN} will print an
3943 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
3944 of masked watchpoints, if the current architecture supports this
3945 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
3946 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
3947 to an address to watch. The mask specifies that some bits of an address
3948 (the bits which are reset in the mask) should be ignored when matching
3949 the address accessed by the inferior against the watchpoint address.
3950 Thus, a masked watchpoint watches many addresses simultaneously---those
3951 addresses whose unmasked bits are identical to the unmasked bits in the
3952 watchpoint address. The @code{mask} argument implies @code{-location}.
3956 (@value{GDBP}) watch foo mask 0xffff00ff
3957 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
3961 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3962 Set a watchpoint that will break when the value of @var{expr} is read
3966 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3967 Set a watchpoint that will break when @var{expr} is either read from
3968 or written into by the program.
3970 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
3971 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
3972 This command prints a list of watchpoints, using the same format as
3973 @code{info break} (@pxref{Set Breaks}).
3976 If you watch for a change in a numerically entered address you need to
3977 dereference it, as the address itself is just a constant number which will
3978 never change. @value{GDBN} refuses to create a watchpoint that watches
3979 a never-changing value:
3982 (@value{GDBP}) watch 0x600850
3983 Cannot watch constant value 0x600850.
3984 (@value{GDBP}) watch *(int *) 0x600850
3985 Watchpoint 1: *(int *) 6293584
3988 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3989 watchpoints execute very quickly, and the debugger reports a change in
3990 value at the exact instruction where the change occurs. If @value{GDBN}
3991 cannot set a hardware watchpoint, it sets a software watchpoint, which
3992 executes more slowly and reports the change in value at the next
3993 @emph{statement}, not the instruction, after the change occurs.
3995 @cindex use only software watchpoints
3996 You can force @value{GDBN} to use only software watchpoints with the
3997 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3998 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3999 the underlying system supports them. (Note that hardware-assisted
4000 watchpoints that were set @emph{before} setting
4001 @code{can-use-hw-watchpoints} to zero will still use the hardware
4002 mechanism of watching expression values.)
4005 @item set can-use-hw-watchpoints
4006 @kindex set can-use-hw-watchpoints
4007 Set whether or not to use hardware watchpoints.
4009 @item show can-use-hw-watchpoints
4010 @kindex show can-use-hw-watchpoints
4011 Show the current mode of using hardware watchpoints.
4014 For remote targets, you can restrict the number of hardware
4015 watchpoints @value{GDBN} will use, see @ref{set remote
4016 hardware-breakpoint-limit}.
4018 When you issue the @code{watch} command, @value{GDBN} reports
4021 Hardware watchpoint @var{num}: @var{expr}
4025 if it was able to set a hardware watchpoint.
4027 Currently, the @code{awatch} and @code{rwatch} commands can only set
4028 hardware watchpoints, because accesses to data that don't change the
4029 value of the watched expression cannot be detected without examining
4030 every instruction as it is being executed, and @value{GDBN} does not do
4031 that currently. If @value{GDBN} finds that it is unable to set a
4032 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4033 will print a message like this:
4036 Expression cannot be implemented with read/access watchpoint.
4039 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4040 data type of the watched expression is wider than what a hardware
4041 watchpoint on the target machine can handle. For example, some systems
4042 can only watch regions that are up to 4 bytes wide; on such systems you
4043 cannot set hardware watchpoints for an expression that yields a
4044 double-precision floating-point number (which is typically 8 bytes
4045 wide). As a work-around, it might be possible to break the large region
4046 into a series of smaller ones and watch them with separate watchpoints.
4048 If you set too many hardware watchpoints, @value{GDBN} might be unable
4049 to insert all of them when you resume the execution of your program.
4050 Since the precise number of active watchpoints is unknown until such
4051 time as the program is about to be resumed, @value{GDBN} might not be
4052 able to warn you about this when you set the watchpoints, and the
4053 warning will be printed only when the program is resumed:
4056 Hardware watchpoint @var{num}: Could not insert watchpoint
4060 If this happens, delete or disable some of the watchpoints.
4062 Watching complex expressions that reference many variables can also
4063 exhaust the resources available for hardware-assisted watchpoints.
4064 That's because @value{GDBN} needs to watch every variable in the
4065 expression with separately allocated resources.
4067 If you call a function interactively using @code{print} or @code{call},
4068 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4069 kind of breakpoint or the call completes.
4071 @value{GDBN} automatically deletes watchpoints that watch local
4072 (automatic) variables, or expressions that involve such variables, when
4073 they go out of scope, that is, when the execution leaves the block in
4074 which these variables were defined. In particular, when the program
4075 being debugged terminates, @emph{all} local variables go out of scope,
4076 and so only watchpoints that watch global variables remain set. If you
4077 rerun the program, you will need to set all such watchpoints again. One
4078 way of doing that would be to set a code breakpoint at the entry to the
4079 @code{main} function and when it breaks, set all the watchpoints.
4081 @cindex watchpoints and threads
4082 @cindex threads and watchpoints
4083 In multi-threaded programs, watchpoints will detect changes to the
4084 watched expression from every thread.
4087 @emph{Warning:} In multi-threaded programs, software watchpoints
4088 have only limited usefulness. If @value{GDBN} creates a software
4089 watchpoint, it can only watch the value of an expression @emph{in a
4090 single thread}. If you are confident that the expression can only
4091 change due to the current thread's activity (and if you are also
4092 confident that no other thread can become current), then you can use
4093 software watchpoints as usual. However, @value{GDBN} may not notice
4094 when a non-current thread's activity changes the expression. (Hardware
4095 watchpoints, in contrast, watch an expression in all threads.)
4098 @xref{set remote hardware-watchpoint-limit}.
4100 @node Set Catchpoints
4101 @subsection Setting Catchpoints
4102 @cindex catchpoints, setting
4103 @cindex exception handlers
4104 @cindex event handling
4106 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4107 kinds of program events, such as C@t{++} exceptions or the loading of a
4108 shared library. Use the @code{catch} command to set a catchpoint.
4112 @item catch @var{event}
4113 Stop when @var{event} occurs. @var{event} can be any of the following:
4116 @item throw @r{[}@var{regexp}@r{]}
4117 @itemx rethrow @r{[}@var{regexp}@r{]}
4118 @itemx catch @r{[}@var{regexp}@r{]}
4120 @kindex catch rethrow
4122 @cindex stop on C@t{++} exceptions
4123 The throwing, re-throwing, or catching of a C@t{++} exception.
4125 If @var{regexp} is given, then only exceptions whose type matches the
4126 regular expression will be caught.
4128 @vindex $_exception@r{, convenience variable}
4129 The convenience variable @code{$_exception} is available at an
4130 exception-related catchpoint, on some systems. This holds the
4131 exception being thrown.
4133 There are currently some limitations to C@t{++} exception handling in
4138 The support for these commands is system-dependent. Currently, only
4139 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4143 The regular expression feature and the @code{$_exception} convenience
4144 variable rely on the presence of some SDT probes in @code{libstdc++}.
4145 If these probes are not present, then these features cannot be used.
4146 These probes were first available in the GCC 4.8 release, but whether
4147 or not they are available in your GCC also depends on how it was
4151 The @code{$_exception} convenience variable is only valid at the
4152 instruction at which an exception-related catchpoint is set.
4155 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4156 location in the system library which implements runtime exception
4157 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4158 (@pxref{Selection}) to get to your code.
4161 If you call a function interactively, @value{GDBN} normally returns
4162 control to you when the function has finished executing. If the call
4163 raises an exception, however, the call may bypass the mechanism that
4164 returns control to you and cause your program either to abort or to
4165 simply continue running until it hits a breakpoint, catches a signal
4166 that @value{GDBN} is listening for, or exits. This is the case even if
4167 you set a catchpoint for the exception; catchpoints on exceptions are
4168 disabled within interactive calls. @xref{Calling}, for information on
4169 controlling this with @code{set unwind-on-terminating-exception}.
4172 You cannot raise an exception interactively.
4175 You cannot install an exception handler interactively.
4179 @kindex catch exception
4180 @cindex Ada exception catching
4181 @cindex catch Ada exceptions
4182 An Ada exception being raised. If an exception name is specified
4183 at the end of the command (eg @code{catch exception Program_Error}),
4184 the debugger will stop only when this specific exception is raised.
4185 Otherwise, the debugger stops execution when any Ada exception is raised.
4187 When inserting an exception catchpoint on a user-defined exception whose
4188 name is identical to one of the exceptions defined by the language, the
4189 fully qualified name must be used as the exception name. Otherwise,
4190 @value{GDBN} will assume that it should stop on the pre-defined exception
4191 rather than the user-defined one. For instance, assuming an exception
4192 called @code{Constraint_Error} is defined in package @code{Pck}, then
4193 the command to use to catch such exceptions is @kbd{catch exception
4194 Pck.Constraint_Error}.
4196 @item exception unhandled
4197 @kindex catch exception unhandled
4198 An exception that was raised but is not handled by the program.
4201 @kindex catch assert
4202 A failed Ada assertion.
4206 @cindex break on fork/exec
4207 A call to @code{exec}. This is currently only available for HP-UX
4211 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
4212 @kindex catch syscall
4213 @cindex break on a system call.
4214 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4215 syscall is a mechanism for application programs to request a service
4216 from the operating system (OS) or one of the OS system services.
4217 @value{GDBN} can catch some or all of the syscalls issued by the
4218 debuggee, and show the related information for each syscall. If no
4219 argument is specified, calls to and returns from all system calls
4222 @var{name} can be any system call name that is valid for the
4223 underlying OS. Just what syscalls are valid depends on the OS. On
4224 GNU and Unix systems, you can find the full list of valid syscall
4225 names on @file{/usr/include/asm/unistd.h}.
4227 @c For MS-Windows, the syscall names and the corresponding numbers
4228 @c can be found, e.g., on this URL:
4229 @c http://www.metasploit.com/users/opcode/syscalls.html
4230 @c but we don't support Windows syscalls yet.
4232 Normally, @value{GDBN} knows in advance which syscalls are valid for
4233 each OS, so you can use the @value{GDBN} command-line completion
4234 facilities (@pxref{Completion,, command completion}) to list the
4237 You may also specify the system call numerically. A syscall's
4238 number is the value passed to the OS's syscall dispatcher to
4239 identify the requested service. When you specify the syscall by its
4240 name, @value{GDBN} uses its database of syscalls to convert the name
4241 into the corresponding numeric code, but using the number directly
4242 may be useful if @value{GDBN}'s database does not have the complete
4243 list of syscalls on your system (e.g., because @value{GDBN} lags
4244 behind the OS upgrades).
4246 The example below illustrates how this command works if you don't provide
4250 (@value{GDBP}) catch syscall
4251 Catchpoint 1 (syscall)
4253 Starting program: /tmp/catch-syscall
4255 Catchpoint 1 (call to syscall 'close'), \
4256 0xffffe424 in __kernel_vsyscall ()
4260 Catchpoint 1 (returned from syscall 'close'), \
4261 0xffffe424 in __kernel_vsyscall ()
4265 Here is an example of catching a system call by name:
4268 (@value{GDBP}) catch syscall chroot
4269 Catchpoint 1 (syscall 'chroot' [61])
4271 Starting program: /tmp/catch-syscall
4273 Catchpoint 1 (call to syscall 'chroot'), \
4274 0xffffe424 in __kernel_vsyscall ()
4278 Catchpoint 1 (returned from syscall 'chroot'), \
4279 0xffffe424 in __kernel_vsyscall ()
4283 An example of specifying a system call numerically. In the case
4284 below, the syscall number has a corresponding entry in the XML
4285 file, so @value{GDBN} finds its name and prints it:
4288 (@value{GDBP}) catch syscall 252
4289 Catchpoint 1 (syscall(s) 'exit_group')
4291 Starting program: /tmp/catch-syscall
4293 Catchpoint 1 (call to syscall 'exit_group'), \
4294 0xffffe424 in __kernel_vsyscall ()
4298 Program exited normally.
4302 However, there can be situations when there is no corresponding name
4303 in XML file for that syscall number. In this case, @value{GDBN} prints
4304 a warning message saying that it was not able to find the syscall name,
4305 but the catchpoint will be set anyway. See the example below:
4308 (@value{GDBP}) catch syscall 764
4309 warning: The number '764' does not represent a known syscall.
4310 Catchpoint 2 (syscall 764)
4314 If you configure @value{GDBN} using the @samp{--without-expat} option,
4315 it will not be able to display syscall names. Also, if your
4316 architecture does not have an XML file describing its system calls,
4317 you will not be able to see the syscall names. It is important to
4318 notice that these two features are used for accessing the syscall
4319 name database. In either case, you will see a warning like this:
4322 (@value{GDBP}) catch syscall
4323 warning: Could not open "syscalls/i386-linux.xml"
4324 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4325 GDB will not be able to display syscall names.
4326 Catchpoint 1 (syscall)
4330 Of course, the file name will change depending on your architecture and system.
4332 Still using the example above, you can also try to catch a syscall by its
4333 number. In this case, you would see something like:
4336 (@value{GDBP}) catch syscall 252
4337 Catchpoint 1 (syscall(s) 252)
4340 Again, in this case @value{GDBN} would not be able to display syscall's names.
4344 A call to @code{fork}. This is currently only available for HP-UX
4349 A call to @code{vfork}. This is currently only available for HP-UX
4352 @item load @r{[}regexp@r{]}
4353 @itemx unload @r{[}regexp@r{]}
4355 @kindex catch unload
4356 The loading or unloading of a shared library. If @var{regexp} is
4357 given, then the catchpoint will stop only if the regular expression
4358 matches one of the affected libraries.
4360 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4361 @kindex catch signal
4362 The delivery of a signal.
4364 With no arguments, this catchpoint will catch any signal that is not
4365 used internally by @value{GDBN}, specifically, all signals except
4366 @samp{SIGTRAP} and @samp{SIGINT}.
4368 With the argument @samp{all}, all signals, including those used by
4369 @value{GDBN}, will be caught. This argument cannot be used with other
4372 Otherwise, the arguments are a list of signal names as given to
4373 @code{handle} (@pxref{Signals}). Only signals specified in this list
4376 One reason that @code{catch signal} can be more useful than
4377 @code{handle} is that you can attach commands and conditions to the
4380 When a signal is caught by a catchpoint, the signal's @code{stop} and
4381 @code{print} settings, as specified by @code{handle}, are ignored.
4382 However, whether the signal is still delivered to the inferior depends
4383 on the @code{pass} setting; this can be changed in the catchpoint's
4388 @item tcatch @var{event}
4390 Set a catchpoint that is enabled only for one stop. The catchpoint is
4391 automatically deleted after the first time the event is caught.
4395 Use the @code{info break} command to list the current catchpoints.
4399 @subsection Deleting Breakpoints
4401 @cindex clearing breakpoints, watchpoints, catchpoints
4402 @cindex deleting breakpoints, watchpoints, catchpoints
4403 It is often necessary to eliminate a breakpoint, watchpoint, or
4404 catchpoint once it has done its job and you no longer want your program
4405 to stop there. This is called @dfn{deleting} the breakpoint. A
4406 breakpoint that has been deleted no longer exists; it is forgotten.
4408 With the @code{clear} command you can delete breakpoints according to
4409 where they are in your program. With the @code{delete} command you can
4410 delete individual breakpoints, watchpoints, or catchpoints by specifying
4411 their breakpoint numbers.
4413 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4414 automatically ignores breakpoints on the first instruction to be executed
4415 when you continue execution without changing the execution address.
4420 Delete any breakpoints at the next instruction to be executed in the
4421 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4422 the innermost frame is selected, this is a good way to delete a
4423 breakpoint where your program just stopped.
4425 @item clear @var{location}
4426 Delete any breakpoints set at the specified @var{location}.
4427 @xref{Specify Location}, for the various forms of @var{location}; the
4428 most useful ones are listed below:
4431 @item clear @var{function}
4432 @itemx clear @var{filename}:@var{function}
4433 Delete any breakpoints set at entry to the named @var{function}.
4435 @item clear @var{linenum}
4436 @itemx clear @var{filename}:@var{linenum}
4437 Delete any breakpoints set at or within the code of the specified
4438 @var{linenum} of the specified @var{filename}.
4441 @cindex delete breakpoints
4443 @kindex d @r{(@code{delete})}
4444 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4445 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4446 ranges specified as arguments. If no argument is specified, delete all
4447 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4448 confirm off}). You can abbreviate this command as @code{d}.
4452 @subsection Disabling Breakpoints
4454 @cindex enable/disable a breakpoint
4455 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4456 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4457 it had been deleted, but remembers the information on the breakpoint so
4458 that you can @dfn{enable} it again later.
4460 You disable and enable breakpoints, watchpoints, and catchpoints with
4461 the @code{enable} and @code{disable} commands, optionally specifying
4462 one or more breakpoint numbers as arguments. Use @code{info break} to
4463 print a list of all breakpoints, watchpoints, and catchpoints if you
4464 do not know which numbers to use.
4466 Disabling and enabling a breakpoint that has multiple locations
4467 affects all of its locations.
4469 A breakpoint, watchpoint, or catchpoint can have any of several
4470 different states of enablement:
4474 Enabled. The breakpoint stops your program. A breakpoint set
4475 with the @code{break} command starts out in this state.
4477 Disabled. The breakpoint has no effect on your program.
4479 Enabled once. The breakpoint stops your program, but then becomes
4482 Enabled for a count. The breakpoint stops your program for the next
4483 N times, then becomes disabled.
4485 Enabled for deletion. The breakpoint stops your program, but
4486 immediately after it does so it is deleted permanently. A breakpoint
4487 set with the @code{tbreak} command starts out in this state.
4490 You can use the following commands to enable or disable breakpoints,
4491 watchpoints, and catchpoints:
4495 @kindex dis @r{(@code{disable})}
4496 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4497 Disable the specified breakpoints---or all breakpoints, if none are
4498 listed. A disabled breakpoint has no effect but is not forgotten. All
4499 options such as ignore-counts, conditions and commands are remembered in
4500 case the breakpoint is enabled again later. You may abbreviate
4501 @code{disable} as @code{dis}.
4504 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4505 Enable the specified breakpoints (or all defined breakpoints). They
4506 become effective once again in stopping your program.
4508 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4509 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4510 of these breakpoints immediately after stopping your program.
4512 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4513 Enable the specified breakpoints temporarily. @value{GDBN} records
4514 @var{count} with each of the specified breakpoints, and decrements a
4515 breakpoint's count when it is hit. When any count reaches 0,
4516 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4517 count (@pxref{Conditions, ,Break Conditions}), that will be
4518 decremented to 0 before @var{count} is affected.
4520 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4521 Enable the specified breakpoints to work once, then die. @value{GDBN}
4522 deletes any of these breakpoints as soon as your program stops there.
4523 Breakpoints set by the @code{tbreak} command start out in this state.
4526 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4527 @c confusing: tbreak is also initially enabled.
4528 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4529 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4530 subsequently, they become disabled or enabled only when you use one of
4531 the commands above. (The command @code{until} can set and delete a
4532 breakpoint of its own, but it does not change the state of your other
4533 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4537 @subsection Break Conditions
4538 @cindex conditional breakpoints
4539 @cindex breakpoint conditions
4541 @c FIXME what is scope of break condition expr? Context where wanted?
4542 @c in particular for a watchpoint?
4543 The simplest sort of breakpoint breaks every time your program reaches a
4544 specified place. You can also specify a @dfn{condition} for a
4545 breakpoint. A condition is just a Boolean expression in your
4546 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4547 a condition evaluates the expression each time your program reaches it,
4548 and your program stops only if the condition is @emph{true}.
4550 This is the converse of using assertions for program validation; in that
4551 situation, you want to stop when the assertion is violated---that is,
4552 when the condition is false. In C, if you want to test an assertion expressed
4553 by the condition @var{assert}, you should set the condition
4554 @samp{! @var{assert}} on the appropriate breakpoint.
4556 Conditions are also accepted for watchpoints; you may not need them,
4557 since a watchpoint is inspecting the value of an expression anyhow---but
4558 it might be simpler, say, to just set a watchpoint on a variable name,
4559 and specify a condition that tests whether the new value is an interesting
4562 Break conditions can have side effects, and may even call functions in
4563 your program. This can be useful, for example, to activate functions
4564 that log program progress, or to use your own print functions to
4565 format special data structures. The effects are completely predictable
4566 unless there is another enabled breakpoint at the same address. (In
4567 that case, @value{GDBN} might see the other breakpoint first and stop your
4568 program without checking the condition of this one.) Note that
4569 breakpoint commands are usually more convenient and flexible than break
4571 purpose of performing side effects when a breakpoint is reached
4572 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4574 Breakpoint conditions can also be evaluated on the target's side if
4575 the target supports it. Instead of evaluating the conditions locally,
4576 @value{GDBN} encodes the expression into an agent expression
4577 (@pxref{Agent Expressions}) suitable for execution on the target,
4578 independently of @value{GDBN}. Global variables become raw memory
4579 locations, locals become stack accesses, and so forth.
4581 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4582 when its condition evaluates to true. This mechanism may provide faster
4583 response times depending on the performance characteristics of the target
4584 since it does not need to keep @value{GDBN} informed about
4585 every breakpoint trigger, even those with false conditions.
4587 Break conditions can be specified when a breakpoint is set, by using
4588 @samp{if} in the arguments to the @code{break} command. @xref{Set
4589 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4590 with the @code{condition} command.
4592 You can also use the @code{if} keyword with the @code{watch} command.
4593 The @code{catch} command does not recognize the @code{if} keyword;
4594 @code{condition} is the only way to impose a further condition on a
4599 @item condition @var{bnum} @var{expression}
4600 Specify @var{expression} as the break condition for breakpoint,
4601 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4602 breakpoint @var{bnum} stops your program only if the value of
4603 @var{expression} is true (nonzero, in C). When you use
4604 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4605 syntactic correctness, and to determine whether symbols in it have
4606 referents in the context of your breakpoint. If @var{expression} uses
4607 symbols not referenced in the context of the breakpoint, @value{GDBN}
4608 prints an error message:
4611 No symbol "foo" in current context.
4616 not actually evaluate @var{expression} at the time the @code{condition}
4617 command (or a command that sets a breakpoint with a condition, like
4618 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4620 @item condition @var{bnum}
4621 Remove the condition from breakpoint number @var{bnum}. It becomes
4622 an ordinary unconditional breakpoint.
4625 @cindex ignore count (of breakpoint)
4626 A special case of a breakpoint condition is to stop only when the
4627 breakpoint has been reached a certain number of times. This is so
4628 useful that there is a special way to do it, using the @dfn{ignore
4629 count} of the breakpoint. Every breakpoint has an ignore count, which
4630 is an integer. Most of the time, the ignore count is zero, and
4631 therefore has no effect. But if your program reaches a breakpoint whose
4632 ignore count is positive, then instead of stopping, it just decrements
4633 the ignore count by one and continues. As a result, if the ignore count
4634 value is @var{n}, the breakpoint does not stop the next @var{n} times
4635 your program reaches it.
4639 @item ignore @var{bnum} @var{count}
4640 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4641 The next @var{count} times the breakpoint is reached, your program's
4642 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4645 To make the breakpoint stop the next time it is reached, specify
4648 When you use @code{continue} to resume execution of your program from a
4649 breakpoint, you can specify an ignore count directly as an argument to
4650 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4651 Stepping,,Continuing and Stepping}.
4653 If a breakpoint has a positive ignore count and a condition, the
4654 condition is not checked. Once the ignore count reaches zero,
4655 @value{GDBN} resumes checking the condition.
4657 You could achieve the effect of the ignore count with a condition such
4658 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4659 is decremented each time. @xref{Convenience Vars, ,Convenience
4663 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4666 @node Break Commands
4667 @subsection Breakpoint Command Lists
4669 @cindex breakpoint commands
4670 You can give any breakpoint (or watchpoint or catchpoint) a series of
4671 commands to execute when your program stops due to that breakpoint. For
4672 example, you might want to print the values of certain expressions, or
4673 enable other breakpoints.
4677 @kindex end@r{ (breakpoint commands)}
4678 @item commands @r{[}@var{range}@dots{}@r{]}
4679 @itemx @dots{} @var{command-list} @dots{}
4681 Specify a list of commands for the given breakpoints. The commands
4682 themselves appear on the following lines. Type a line containing just
4683 @code{end} to terminate the commands.
4685 To remove all commands from a breakpoint, type @code{commands} and
4686 follow it immediately with @code{end}; that is, give no commands.
4688 With no argument, @code{commands} refers to the last breakpoint,
4689 watchpoint, or catchpoint set (not to the breakpoint most recently
4690 encountered). If the most recent breakpoints were set with a single
4691 command, then the @code{commands} will apply to all the breakpoints
4692 set by that command. This applies to breakpoints set by
4693 @code{rbreak}, and also applies when a single @code{break} command
4694 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4698 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4699 disabled within a @var{command-list}.
4701 You can use breakpoint commands to start your program up again. Simply
4702 use the @code{continue} command, or @code{step}, or any other command
4703 that resumes execution.
4705 Any other commands in the command list, after a command that resumes
4706 execution, are ignored. This is because any time you resume execution
4707 (even with a simple @code{next} or @code{step}), you may encounter
4708 another breakpoint---which could have its own command list, leading to
4709 ambiguities about which list to execute.
4712 If the first command you specify in a command list is @code{silent}, the
4713 usual message about stopping at a breakpoint is not printed. This may
4714 be desirable for breakpoints that are to print a specific message and
4715 then continue. If none of the remaining commands print anything, you
4716 see no sign that the breakpoint was reached. @code{silent} is
4717 meaningful only at the beginning of a breakpoint command list.
4719 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4720 print precisely controlled output, and are often useful in silent
4721 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4723 For example, here is how you could use breakpoint commands to print the
4724 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4730 printf "x is %d\n",x
4735 One application for breakpoint commands is to compensate for one bug so
4736 you can test for another. Put a breakpoint just after the erroneous line
4737 of code, give it a condition to detect the case in which something
4738 erroneous has been done, and give it commands to assign correct values
4739 to any variables that need them. End with the @code{continue} command
4740 so that your program does not stop, and start with the @code{silent}
4741 command so that no output is produced. Here is an example:
4752 @node Dynamic Printf
4753 @subsection Dynamic Printf
4755 @cindex dynamic printf
4757 The dynamic printf command @code{dprintf} combines a breakpoint with
4758 formatted printing of your program's data to give you the effect of
4759 inserting @code{printf} calls into your program on-the-fly, without
4760 having to recompile it.
4762 In its most basic form, the output goes to the GDB console. However,
4763 you can set the variable @code{dprintf-style} for alternate handling.
4764 For instance, you can ask to format the output by calling your
4765 program's @code{printf} function. This has the advantage that the
4766 characters go to the program's output device, so they can recorded in
4767 redirects to files and so forth.
4769 If you are doing remote debugging with a stub or agent, you can also
4770 ask to have the printf handled by the remote agent. In addition to
4771 ensuring that the output goes to the remote program's device along
4772 with any other output the program might produce, you can also ask that
4773 the dprintf remain active even after disconnecting from the remote
4774 target. Using the stub/agent is also more efficient, as it can do
4775 everything without needing to communicate with @value{GDBN}.
4779 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
4780 Whenever execution reaches @var{location}, print the values of one or
4781 more @var{expressions} under the control of the string @var{template}.
4782 To print several values, separate them with commas.
4784 @item set dprintf-style @var{style}
4785 Set the dprintf output to be handled in one of several different
4786 styles enumerated below. A change of style affects all existing
4787 dynamic printfs immediately. (If you need individual control over the
4788 print commands, simply define normal breakpoints with
4789 explicitly-supplied command lists.)
4792 @kindex dprintf-style gdb
4793 Handle the output using the @value{GDBN} @code{printf} command.
4796 @kindex dprintf-style call
4797 Handle the output by calling a function in your program (normally
4801 @kindex dprintf-style agent
4802 Have the remote debugging agent (such as @code{gdbserver}) handle
4803 the output itself. This style is only available for agents that
4804 support running commands on the target.
4806 @item set dprintf-function @var{function}
4807 Set the function to call if the dprintf style is @code{call}. By
4808 default its value is @code{printf}. You may set it to any expression.
4809 that @value{GDBN} can evaluate to a function, as per the @code{call}
4812 @item set dprintf-channel @var{channel}
4813 Set a ``channel'' for dprintf. If set to a non-empty value,
4814 @value{GDBN} will evaluate it as an expression and pass the result as
4815 a first argument to the @code{dprintf-function}, in the manner of
4816 @code{fprintf} and similar functions. Otherwise, the dprintf format
4817 string will be the first argument, in the manner of @code{printf}.
4819 As an example, if you wanted @code{dprintf} output to go to a logfile
4820 that is a standard I/O stream assigned to the variable @code{mylog},
4821 you could do the following:
4824 (gdb) set dprintf-style call
4825 (gdb) set dprintf-function fprintf
4826 (gdb) set dprintf-channel mylog
4827 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
4828 Dprintf 1 at 0x123456: file main.c, line 25.
4830 1 dprintf keep y 0x00123456 in main at main.c:25
4831 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
4836 Note that the @code{info break} displays the dynamic printf commands
4837 as normal breakpoint commands; you can thus easily see the effect of
4838 the variable settings.
4840 @item set disconnected-dprintf on
4841 @itemx set disconnected-dprintf off
4842 @kindex set disconnected-dprintf
4843 Choose whether @code{dprintf} commands should continue to run if
4844 @value{GDBN} has disconnected from the target. This only applies
4845 if the @code{dprintf-style} is @code{agent}.
4847 @item show disconnected-dprintf off
4848 @kindex show disconnected-dprintf
4849 Show the current choice for disconnected @code{dprintf}.
4853 @value{GDBN} does not check the validity of function and channel,
4854 relying on you to supply values that are meaningful for the contexts
4855 in which they are being used. For instance, the function and channel
4856 may be the values of local variables, but if that is the case, then
4857 all enabled dynamic prints must be at locations within the scope of
4858 those locals. If evaluation fails, @value{GDBN} will report an error.
4860 @node Save Breakpoints
4861 @subsection How to save breakpoints to a file
4863 To save breakpoint definitions to a file use the @w{@code{save
4864 breakpoints}} command.
4867 @kindex save breakpoints
4868 @cindex save breakpoints to a file for future sessions
4869 @item save breakpoints [@var{filename}]
4870 This command saves all current breakpoint definitions together with
4871 their commands and ignore counts, into a file @file{@var{filename}}
4872 suitable for use in a later debugging session. This includes all
4873 types of breakpoints (breakpoints, watchpoints, catchpoints,
4874 tracepoints). To read the saved breakpoint definitions, use the
4875 @code{source} command (@pxref{Command Files}). Note that watchpoints
4876 with expressions involving local variables may fail to be recreated
4877 because it may not be possible to access the context where the
4878 watchpoint is valid anymore. Because the saved breakpoint definitions
4879 are simply a sequence of @value{GDBN} commands that recreate the
4880 breakpoints, you can edit the file in your favorite editing program,
4881 and remove the breakpoint definitions you're not interested in, or
4882 that can no longer be recreated.
4885 @node Static Probe Points
4886 @subsection Static Probe Points
4888 @cindex static probe point, SystemTap
4889 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
4890 for Statically Defined Tracing, and the probes are designed to have a tiny
4891 runtime code and data footprint, and no dynamic relocations. They are
4892 usable from assembly, C and C@t{++} languages. See
4893 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
4894 for a good reference on how the @acronym{SDT} probes are implemented.
4896 Currently, @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
4897 @acronym{SDT} probes are supported on ELF-compatible systems. See
4898 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
4899 for more information on how to add @code{SystemTap} @acronym{SDT} probes
4900 in your applications.
4902 @cindex semaphores on static probe points
4903 Some probes have an associated semaphore variable; for instance, this
4904 happens automatically if you defined your probe using a DTrace-style
4905 @file{.d} file. If your probe has a semaphore, @value{GDBN} will
4906 automatically enable it when you specify a breakpoint using the
4907 @samp{-probe-stap} notation. But, if you put a breakpoint at a probe's
4908 location by some other method (e.g., @code{break file:line}), then
4909 @value{GDBN} will not automatically set the semaphore.
4911 You can examine the available static static probes using @code{info
4912 probes}, with optional arguments:
4916 @item info probes stap @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
4917 If given, @var{provider} is a regular expression used to match against provider
4918 names when selecting which probes to list. If omitted, probes by all
4919 probes from all providers are listed.
4921 If given, @var{name} is a regular expression to match against probe names
4922 when selecting which probes to list. If omitted, probe names are not
4923 considered when deciding whether to display them.
4925 If given, @var{objfile} is a regular expression used to select which
4926 object files (executable or shared libraries) to examine. If not
4927 given, all object files are considered.
4929 @item info probes all
4930 List the available static probes, from all types.
4933 @vindex $_probe_arg@r{, convenience variable}
4934 A probe may specify up to twelve arguments. These are available at the
4935 point at which the probe is defined---that is, when the current PC is
4936 at the probe's location. The arguments are available using the
4937 convenience variables (@pxref{Convenience Vars})
4938 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. Each probe argument is
4939 an integer of the appropriate size; types are not preserved. The
4940 convenience variable @code{$_probe_argc} holds the number of arguments
4941 at the current probe point.
4943 These variables are always available, but attempts to access them at
4944 any location other than a probe point will cause @value{GDBN} to give
4948 @c @ifclear BARETARGET
4949 @node Error in Breakpoints
4950 @subsection ``Cannot insert breakpoints''
4952 If you request too many active hardware-assisted breakpoints and
4953 watchpoints, you will see this error message:
4955 @c FIXME: the precise wording of this message may change; the relevant
4956 @c source change is not committed yet (Sep 3, 1999).
4958 Stopped; cannot insert breakpoints.
4959 You may have requested too many hardware breakpoints and watchpoints.
4963 This message is printed when you attempt to resume the program, since
4964 only then @value{GDBN} knows exactly how many hardware breakpoints and
4965 watchpoints it needs to insert.
4967 When this message is printed, you need to disable or remove some of the
4968 hardware-assisted breakpoints and watchpoints, and then continue.
4970 @node Breakpoint-related Warnings
4971 @subsection ``Breakpoint address adjusted...''
4972 @cindex breakpoint address adjusted
4974 Some processor architectures place constraints on the addresses at
4975 which breakpoints may be placed. For architectures thus constrained,
4976 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4977 with the constraints dictated by the architecture.
4979 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4980 a VLIW architecture in which a number of RISC-like instructions may be
4981 bundled together for parallel execution. The FR-V architecture
4982 constrains the location of a breakpoint instruction within such a
4983 bundle to the instruction with the lowest address. @value{GDBN}
4984 honors this constraint by adjusting a breakpoint's address to the
4985 first in the bundle.
4987 It is not uncommon for optimized code to have bundles which contain
4988 instructions from different source statements, thus it may happen that
4989 a breakpoint's address will be adjusted from one source statement to
4990 another. Since this adjustment may significantly alter @value{GDBN}'s
4991 breakpoint related behavior from what the user expects, a warning is
4992 printed when the breakpoint is first set and also when the breakpoint
4995 A warning like the one below is printed when setting a breakpoint
4996 that's been subject to address adjustment:
4999 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5002 Such warnings are printed both for user settable and @value{GDBN}'s
5003 internal breakpoints. If you see one of these warnings, you should
5004 verify that a breakpoint set at the adjusted address will have the
5005 desired affect. If not, the breakpoint in question may be removed and
5006 other breakpoints may be set which will have the desired behavior.
5007 E.g., it may be sufficient to place the breakpoint at a later
5008 instruction. A conditional breakpoint may also be useful in some
5009 cases to prevent the breakpoint from triggering too often.
5011 @value{GDBN} will also issue a warning when stopping at one of these
5012 adjusted breakpoints:
5015 warning: Breakpoint 1 address previously adjusted from 0x00010414
5019 When this warning is encountered, it may be too late to take remedial
5020 action except in cases where the breakpoint is hit earlier or more
5021 frequently than expected.
5023 @node Continuing and Stepping
5024 @section Continuing and Stepping
5028 @cindex resuming execution
5029 @dfn{Continuing} means resuming program execution until your program
5030 completes normally. In contrast, @dfn{stepping} means executing just
5031 one more ``step'' of your program, where ``step'' may mean either one
5032 line of source code, or one machine instruction (depending on what
5033 particular command you use). Either when continuing or when stepping,
5034 your program may stop even sooner, due to a breakpoint or a signal. (If
5035 it stops due to a signal, you may want to use @code{handle}, or use
5036 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
5040 @kindex c @r{(@code{continue})}
5041 @kindex fg @r{(resume foreground execution)}
5042 @item continue @r{[}@var{ignore-count}@r{]}
5043 @itemx c @r{[}@var{ignore-count}@r{]}
5044 @itemx fg @r{[}@var{ignore-count}@r{]}
5045 Resume program execution, at the address where your program last stopped;
5046 any breakpoints set at that address are bypassed. The optional argument
5047 @var{ignore-count} allows you to specify a further number of times to
5048 ignore a breakpoint at this location; its effect is like that of
5049 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5051 The argument @var{ignore-count} is meaningful only when your program
5052 stopped due to a breakpoint. At other times, the argument to
5053 @code{continue} is ignored.
5055 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5056 debugged program is deemed to be the foreground program) are provided
5057 purely for convenience, and have exactly the same behavior as
5061 To resume execution at a different place, you can use @code{return}
5062 (@pxref{Returning, ,Returning from a Function}) to go back to the
5063 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5064 Different Address}) to go to an arbitrary location in your program.
5066 A typical technique for using stepping is to set a breakpoint
5067 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5068 beginning of the function or the section of your program where a problem
5069 is believed to lie, run your program until it stops at that breakpoint,
5070 and then step through the suspect area, examining the variables that are
5071 interesting, until you see the problem happen.
5075 @kindex s @r{(@code{step})}
5077 Continue running your program until control reaches a different source
5078 line, then stop it and return control to @value{GDBN}. This command is
5079 abbreviated @code{s}.
5082 @c "without debugging information" is imprecise; actually "without line
5083 @c numbers in the debugging information". (gcc -g1 has debugging info but
5084 @c not line numbers). But it seems complex to try to make that
5085 @c distinction here.
5086 @emph{Warning:} If you use the @code{step} command while control is
5087 within a function that was compiled without debugging information,
5088 execution proceeds until control reaches a function that does have
5089 debugging information. Likewise, it will not step into a function which
5090 is compiled without debugging information. To step through functions
5091 without debugging information, use the @code{stepi} command, described
5095 The @code{step} command only stops at the first instruction of a source
5096 line. This prevents the multiple stops that could otherwise occur in
5097 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5098 to stop if a function that has debugging information is called within
5099 the line. In other words, @code{step} @emph{steps inside} any functions
5100 called within the line.
5102 Also, the @code{step} command only enters a function if there is line
5103 number information for the function. Otherwise it acts like the
5104 @code{next} command. This avoids problems when using @code{cc -gl}
5105 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5106 was any debugging information about the routine.
5108 @item step @var{count}
5109 Continue running as in @code{step}, but do so @var{count} times. If a
5110 breakpoint is reached, or a signal not related to stepping occurs before
5111 @var{count} steps, stepping stops right away.
5114 @kindex n @r{(@code{next})}
5115 @item next @r{[}@var{count}@r{]}
5116 Continue to the next source line in the current (innermost) stack frame.
5117 This is similar to @code{step}, but function calls that appear within
5118 the line of code are executed without stopping. Execution stops when
5119 control reaches a different line of code at the original stack level
5120 that was executing when you gave the @code{next} command. This command
5121 is abbreviated @code{n}.
5123 An argument @var{count} is a repeat count, as for @code{step}.
5126 @c FIX ME!! Do we delete this, or is there a way it fits in with
5127 @c the following paragraph? --- Vctoria
5129 @c @code{next} within a function that lacks debugging information acts like
5130 @c @code{step}, but any function calls appearing within the code of the
5131 @c function are executed without stopping.
5133 The @code{next} command only stops at the first instruction of a
5134 source line. This prevents multiple stops that could otherwise occur in
5135 @code{switch} statements, @code{for} loops, etc.
5137 @kindex set step-mode
5139 @cindex functions without line info, and stepping
5140 @cindex stepping into functions with no line info
5141 @itemx set step-mode on
5142 The @code{set step-mode on} command causes the @code{step} command to
5143 stop at the first instruction of a function which contains no debug line
5144 information rather than stepping over it.
5146 This is useful in cases where you may be interested in inspecting the
5147 machine instructions of a function which has no symbolic info and do not
5148 want @value{GDBN} to automatically skip over this function.
5150 @item set step-mode off
5151 Causes the @code{step} command to step over any functions which contains no
5152 debug information. This is the default.
5154 @item show step-mode
5155 Show whether @value{GDBN} will stop in or step over functions without
5156 source line debug information.
5159 @kindex fin @r{(@code{finish})}
5161 Continue running until just after function in the selected stack frame
5162 returns. Print the returned value (if any). This command can be
5163 abbreviated as @code{fin}.
5165 Contrast this with the @code{return} command (@pxref{Returning,
5166 ,Returning from a Function}).
5169 @kindex u @r{(@code{until})}
5170 @cindex run until specified location
5173 Continue running until a source line past the current line, in the
5174 current stack frame, is reached. This command is used to avoid single
5175 stepping through a loop more than once. It is like the @code{next}
5176 command, except that when @code{until} encounters a jump, it
5177 automatically continues execution until the program counter is greater
5178 than the address of the jump.
5180 This means that when you reach the end of a loop after single stepping
5181 though it, @code{until} makes your program continue execution until it
5182 exits the loop. In contrast, a @code{next} command at the end of a loop
5183 simply steps back to the beginning of the loop, which forces you to step
5184 through the next iteration.
5186 @code{until} always stops your program if it attempts to exit the current
5189 @code{until} may produce somewhat counterintuitive results if the order
5190 of machine code does not match the order of the source lines. For
5191 example, in the following excerpt from a debugging session, the @code{f}
5192 (@code{frame}) command shows that execution is stopped at line
5193 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5197 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5199 (@value{GDBP}) until
5200 195 for ( ; argc > 0; NEXTARG) @{
5203 This happened because, for execution efficiency, the compiler had
5204 generated code for the loop closure test at the end, rather than the
5205 start, of the loop---even though the test in a C @code{for}-loop is
5206 written before the body of the loop. The @code{until} command appeared
5207 to step back to the beginning of the loop when it advanced to this
5208 expression; however, it has not really gone to an earlier
5209 statement---not in terms of the actual machine code.
5211 @code{until} with no argument works by means of single
5212 instruction stepping, and hence is slower than @code{until} with an
5215 @item until @var{location}
5216 @itemx u @var{location}
5217 Continue running your program until either the specified location is
5218 reached, or the current stack frame returns. @var{location} is any of
5219 the forms described in @ref{Specify Location}.
5220 This form of the command uses temporary breakpoints, and
5221 hence is quicker than @code{until} without an argument. The specified
5222 location is actually reached only if it is in the current frame. This
5223 implies that @code{until} can be used to skip over recursive function
5224 invocations. For instance in the code below, if the current location is
5225 line @code{96}, issuing @code{until 99} will execute the program up to
5226 line @code{99} in the same invocation of factorial, i.e., after the inner
5227 invocations have returned.
5230 94 int factorial (int value)
5232 96 if (value > 1) @{
5233 97 value *= factorial (value - 1);
5240 @kindex advance @var{location}
5241 @item advance @var{location}
5242 Continue running the program up to the given @var{location}. An argument is
5243 required, which should be of one of the forms described in
5244 @ref{Specify Location}.
5245 Execution will also stop upon exit from the current stack
5246 frame. This command is similar to @code{until}, but @code{advance} will
5247 not skip over recursive function calls, and the target location doesn't
5248 have to be in the same frame as the current one.
5252 @kindex si @r{(@code{stepi})}
5254 @itemx stepi @var{arg}
5256 Execute one machine instruction, then stop and return to the debugger.
5258 It is often useful to do @samp{display/i $pc} when stepping by machine
5259 instructions. This makes @value{GDBN} automatically display the next
5260 instruction to be executed, each time your program stops. @xref{Auto
5261 Display,, Automatic Display}.
5263 An argument is a repeat count, as in @code{step}.
5267 @kindex ni @r{(@code{nexti})}
5269 @itemx nexti @var{arg}
5271 Execute one machine instruction, but if it is a function call,
5272 proceed until the function returns.
5274 An argument is a repeat count, as in @code{next}.
5278 @anchor{range stepping}
5279 @cindex range stepping
5280 @cindex target-assisted range stepping
5281 By default, and if available, @value{GDBN} makes use of
5282 target-assisted @dfn{range stepping}. In other words, whenever you
5283 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5284 tells the target to step the corresponding range of instruction
5285 addresses instead of issuing multiple single-steps. This speeds up
5286 line stepping, particularly for remote targets. Ideally, there should
5287 be no reason you would want to turn range stepping off. However, it's
5288 possible that a bug in the debug info, a bug in the remote stub (for
5289 remote targets), or even a bug in @value{GDBN} could make line
5290 stepping behave incorrectly when target-assisted range stepping is
5291 enabled. You can use the following command to turn off range stepping
5295 @kindex set range-stepping
5296 @kindex show range-stepping
5297 @item set range-stepping
5298 @itemx show range-stepping
5299 Control whether range stepping is enabled.
5301 If @code{on}, and the target supports it, @value{GDBN} tells the
5302 target to step a range of addresses itself, instead of issuing
5303 multiple single-steps. If @code{off}, @value{GDBN} always issues
5304 single-steps, even if range stepping is supported by the target. The
5305 default is @code{on}.
5309 @node Skipping Over Functions and Files
5310 @section Skipping Over Functions and Files
5311 @cindex skipping over functions and files
5313 The program you are debugging may contain some functions which are
5314 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
5315 skip a function or all functions in a file when stepping.
5317 For example, consider the following C function:
5328 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5329 are not interested in stepping through @code{boring}. If you run @code{step}
5330 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5331 step over both @code{foo} and @code{boring}!
5333 One solution is to @code{step} into @code{boring} and use the @code{finish}
5334 command to immediately exit it. But this can become tedious if @code{boring}
5335 is called from many places.
5337 A more flexible solution is to execute @kbd{skip boring}. This instructs
5338 @value{GDBN} never to step into @code{boring}. Now when you execute
5339 @code{step} at line 103, you'll step over @code{boring} and directly into
5342 You can also instruct @value{GDBN} to skip all functions in a file, with, for
5343 example, @code{skip file boring.c}.
5346 @kindex skip function
5347 @item skip @r{[}@var{linespec}@r{]}
5348 @itemx skip function @r{[}@var{linespec}@r{]}
5349 After running this command, the function named by @var{linespec} or the
5350 function containing the line named by @var{linespec} will be skipped over when
5351 stepping. @xref{Specify Location}.
5353 If you do not specify @var{linespec}, the function you're currently debugging
5356 (If you have a function called @code{file} that you want to skip, use
5357 @kbd{skip function file}.)
5360 @item skip file @r{[}@var{filename}@r{]}
5361 After running this command, any function whose source lives in @var{filename}
5362 will be skipped over when stepping.
5364 If you do not specify @var{filename}, functions whose source lives in the file
5365 you're currently debugging will be skipped.
5368 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5369 These are the commands for managing your list of skips:
5373 @item info skip @r{[}@var{range}@r{]}
5374 Print details about the specified skip(s). If @var{range} is not specified,
5375 print a table with details about all functions and files marked for skipping.
5376 @code{info skip} prints the following information about each skip:
5380 A number identifying this skip.
5382 The type of this skip, either @samp{function} or @samp{file}.
5383 @item Enabled or Disabled
5384 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
5386 For function skips, this column indicates the address in memory of the function
5387 being skipped. If you've set a function skip on a function which has not yet
5388 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
5389 which has the function is loaded, @code{info skip} will show the function's
5392 For file skips, this field contains the filename being skipped. For functions
5393 skips, this field contains the function name and its line number in the file
5394 where it is defined.
5398 @item skip delete @r{[}@var{range}@r{]}
5399 Delete the specified skip(s). If @var{range} is not specified, delete all
5403 @item skip enable @r{[}@var{range}@r{]}
5404 Enable the specified skip(s). If @var{range} is not specified, enable all
5407 @kindex skip disable
5408 @item skip disable @r{[}@var{range}@r{]}
5409 Disable the specified skip(s). If @var{range} is not specified, disable all
5418 A signal is an asynchronous event that can happen in a program. The
5419 operating system defines the possible kinds of signals, and gives each
5420 kind a name and a number. For example, in Unix @code{SIGINT} is the
5421 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5422 @code{SIGSEGV} is the signal a program gets from referencing a place in
5423 memory far away from all the areas in use; @code{SIGALRM} occurs when
5424 the alarm clock timer goes off (which happens only if your program has
5425 requested an alarm).
5427 @cindex fatal signals
5428 Some signals, including @code{SIGALRM}, are a normal part of the
5429 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5430 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5431 program has not specified in advance some other way to handle the signal.
5432 @code{SIGINT} does not indicate an error in your program, but it is normally
5433 fatal so it can carry out the purpose of the interrupt: to kill the program.
5435 @value{GDBN} has the ability to detect any occurrence of a signal in your
5436 program. You can tell @value{GDBN} in advance what to do for each kind of
5439 @cindex handling signals
5440 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5441 @code{SIGALRM} be silently passed to your program
5442 (so as not to interfere with their role in the program's functioning)
5443 but to stop your program immediately whenever an error signal happens.
5444 You can change these settings with the @code{handle} command.
5447 @kindex info signals
5451 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5452 handle each one. You can use this to see the signal numbers of all
5453 the defined types of signals.
5455 @item info signals @var{sig}
5456 Similar, but print information only about the specified signal number.
5458 @code{info handle} is an alias for @code{info signals}.
5460 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5461 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5462 for details about this command.
5465 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5466 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
5467 can be the number of a signal or its name (with or without the
5468 @samp{SIG} at the beginning); a list of signal numbers of the form
5469 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5470 known signals. Optional arguments @var{keywords}, described below,
5471 say what change to make.
5475 The keywords allowed by the @code{handle} command can be abbreviated.
5476 Their full names are:
5480 @value{GDBN} should not stop your program when this signal happens. It may
5481 still print a message telling you that the signal has come in.
5484 @value{GDBN} should stop your program when this signal happens. This implies
5485 the @code{print} keyword as well.
5488 @value{GDBN} should print a message when this signal happens.
5491 @value{GDBN} should not mention the occurrence of the signal at all. This
5492 implies the @code{nostop} keyword as well.
5496 @value{GDBN} should allow your program to see this signal; your program
5497 can handle the signal, or else it may terminate if the signal is fatal
5498 and not handled. @code{pass} and @code{noignore} are synonyms.
5502 @value{GDBN} should not allow your program to see this signal.
5503 @code{nopass} and @code{ignore} are synonyms.
5507 When a signal stops your program, the signal is not visible to the
5509 continue. Your program sees the signal then, if @code{pass} is in
5510 effect for the signal in question @emph{at that time}. In other words,
5511 after @value{GDBN} reports a signal, you can use the @code{handle}
5512 command with @code{pass} or @code{nopass} to control whether your
5513 program sees that signal when you continue.
5515 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5516 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5517 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5520 You can also use the @code{signal} command to prevent your program from
5521 seeing a signal, or cause it to see a signal it normally would not see,
5522 or to give it any signal at any time. For example, if your program stopped
5523 due to some sort of memory reference error, you might store correct
5524 values into the erroneous variables and continue, hoping to see more
5525 execution; but your program would probably terminate immediately as
5526 a result of the fatal signal once it saw the signal. To prevent this,
5527 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5530 @cindex extra signal information
5531 @anchor{extra signal information}
5533 On some targets, @value{GDBN} can inspect extra signal information
5534 associated with the intercepted signal, before it is actually
5535 delivered to the program being debugged. This information is exported
5536 by the convenience variable @code{$_siginfo}, and consists of data
5537 that is passed by the kernel to the signal handler at the time of the
5538 receipt of a signal. The data type of the information itself is
5539 target dependent. You can see the data type using the @code{ptype
5540 $_siginfo} command. On Unix systems, it typically corresponds to the
5541 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5544 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5545 referenced address that raised a segmentation fault.
5549 (@value{GDBP}) continue
5550 Program received signal SIGSEGV, Segmentation fault.
5551 0x0000000000400766 in main ()
5553 (@value{GDBP}) ptype $_siginfo
5560 struct @{...@} _kill;
5561 struct @{...@} _timer;
5563 struct @{...@} _sigchld;
5564 struct @{...@} _sigfault;
5565 struct @{...@} _sigpoll;
5568 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5572 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5573 $1 = (void *) 0x7ffff7ff7000
5577 Depending on target support, @code{$_siginfo} may also be writable.
5580 @section Stopping and Starting Multi-thread Programs
5582 @cindex stopped threads
5583 @cindex threads, stopped
5585 @cindex continuing threads
5586 @cindex threads, continuing
5588 @value{GDBN} supports debugging programs with multiple threads
5589 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5590 are two modes of controlling execution of your program within the
5591 debugger. In the default mode, referred to as @dfn{all-stop mode},
5592 when any thread in your program stops (for example, at a breakpoint
5593 or while being stepped), all other threads in the program are also stopped by
5594 @value{GDBN}. On some targets, @value{GDBN} also supports
5595 @dfn{non-stop mode}, in which other threads can continue to run freely while
5596 you examine the stopped thread in the debugger.
5599 * All-Stop Mode:: All threads stop when GDB takes control
5600 * Non-Stop Mode:: Other threads continue to execute
5601 * Background Execution:: Running your program asynchronously
5602 * Thread-Specific Breakpoints:: Controlling breakpoints
5603 * Interrupted System Calls:: GDB may interfere with system calls
5604 * Observer Mode:: GDB does not alter program behavior
5608 @subsection All-Stop Mode
5610 @cindex all-stop mode
5612 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5613 @emph{all} threads of execution stop, not just the current thread. This
5614 allows you to examine the overall state of the program, including
5615 switching between threads, without worrying that things may change
5618 Conversely, whenever you restart the program, @emph{all} threads start
5619 executing. @emph{This is true even when single-stepping} with commands
5620 like @code{step} or @code{next}.
5622 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5623 Since thread scheduling is up to your debugging target's operating
5624 system (not controlled by @value{GDBN}), other threads may
5625 execute more than one statement while the current thread completes a
5626 single step. Moreover, in general other threads stop in the middle of a
5627 statement, rather than at a clean statement boundary, when the program
5630 You might even find your program stopped in another thread after
5631 continuing or even single-stepping. This happens whenever some other
5632 thread runs into a breakpoint, a signal, or an exception before the
5633 first thread completes whatever you requested.
5635 @cindex automatic thread selection
5636 @cindex switching threads automatically
5637 @cindex threads, automatic switching
5638 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5639 signal, it automatically selects the thread where that breakpoint or
5640 signal happened. @value{GDBN} alerts you to the context switch with a
5641 message such as @samp{[Switching to Thread @var{n}]} to identify the
5644 On some OSes, you can modify @value{GDBN}'s default behavior by
5645 locking the OS scheduler to allow only a single thread to run.
5648 @item set scheduler-locking @var{mode}
5649 @cindex scheduler locking mode
5650 @cindex lock scheduler
5651 Set the scheduler locking mode. If it is @code{off}, then there is no
5652 locking and any thread may run at any time. If @code{on}, then only the
5653 current thread may run when the inferior is resumed. The @code{step}
5654 mode optimizes for single-stepping; it prevents other threads
5655 from preempting the current thread while you are stepping, so that
5656 the focus of debugging does not change unexpectedly.
5657 Other threads only rarely (or never) get a chance to run
5658 when you step. They are more likely to run when you @samp{next} over a
5659 function call, and they are completely free to run when you use commands
5660 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5661 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5662 the current thread away from the thread that you are debugging.
5664 @item show scheduler-locking
5665 Display the current scheduler locking mode.
5668 @cindex resume threads of multiple processes simultaneously
5669 By default, when you issue one of the execution commands such as
5670 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5671 threads of the current inferior to run. For example, if @value{GDBN}
5672 is attached to two inferiors, each with two threads, the
5673 @code{continue} command resumes only the two threads of the current
5674 inferior. This is useful, for example, when you debug a program that
5675 forks and you want to hold the parent stopped (so that, for instance,
5676 it doesn't run to exit), while you debug the child. In other
5677 situations, you may not be interested in inspecting the current state
5678 of any of the processes @value{GDBN} is attached to, and you may want
5679 to resume them all until some breakpoint is hit. In the latter case,
5680 you can instruct @value{GDBN} to allow all threads of all the
5681 inferiors to run with the @w{@code{set schedule-multiple}} command.
5684 @kindex set schedule-multiple
5685 @item set schedule-multiple
5686 Set the mode for allowing threads of multiple processes to be resumed
5687 when an execution command is issued. When @code{on}, all threads of
5688 all processes are allowed to run. When @code{off}, only the threads
5689 of the current process are resumed. The default is @code{off}. The
5690 @code{scheduler-locking} mode takes precedence when set to @code{on},
5691 or while you are stepping and set to @code{step}.
5693 @item show schedule-multiple
5694 Display the current mode for resuming the execution of threads of
5699 @subsection Non-Stop Mode
5701 @cindex non-stop mode
5703 @c This section is really only a place-holder, and needs to be expanded
5704 @c with more details.
5706 For some multi-threaded targets, @value{GDBN} supports an optional
5707 mode of operation in which you can examine stopped program threads in
5708 the debugger while other threads continue to execute freely. This
5709 minimizes intrusion when debugging live systems, such as programs
5710 where some threads have real-time constraints or must continue to
5711 respond to external events. This is referred to as @dfn{non-stop} mode.
5713 In non-stop mode, when a thread stops to report a debugging event,
5714 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5715 threads as well, in contrast to the all-stop mode behavior. Additionally,
5716 execution commands such as @code{continue} and @code{step} apply by default
5717 only to the current thread in non-stop mode, rather than all threads as
5718 in all-stop mode. This allows you to control threads explicitly in
5719 ways that are not possible in all-stop mode --- for example, stepping
5720 one thread while allowing others to run freely, stepping
5721 one thread while holding all others stopped, or stepping several threads
5722 independently and simultaneously.
5724 To enter non-stop mode, use this sequence of commands before you run
5725 or attach to your program:
5728 # Enable the async interface.
5731 # If using the CLI, pagination breaks non-stop.
5734 # Finally, turn it on!
5738 You can use these commands to manipulate the non-stop mode setting:
5741 @kindex set non-stop
5742 @item set non-stop on
5743 Enable selection of non-stop mode.
5744 @item set non-stop off
5745 Disable selection of non-stop mode.
5746 @kindex show non-stop
5748 Show the current non-stop enablement setting.
5751 Note these commands only reflect whether non-stop mode is enabled,
5752 not whether the currently-executing program is being run in non-stop mode.
5753 In particular, the @code{set non-stop} preference is only consulted when
5754 @value{GDBN} starts or connects to the target program, and it is generally
5755 not possible to switch modes once debugging has started. Furthermore,
5756 since not all targets support non-stop mode, even when you have enabled
5757 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5760 In non-stop mode, all execution commands apply only to the current thread
5761 by default. That is, @code{continue} only continues one thread.
5762 To continue all threads, issue @code{continue -a} or @code{c -a}.
5764 You can use @value{GDBN}'s background execution commands
5765 (@pxref{Background Execution}) to run some threads in the background
5766 while you continue to examine or step others from @value{GDBN}.
5767 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5768 always executed asynchronously in non-stop mode.
5770 Suspending execution is done with the @code{interrupt} command when
5771 running in the background, or @kbd{Ctrl-c} during foreground execution.
5772 In all-stop mode, this stops the whole process;
5773 but in non-stop mode the interrupt applies only to the current thread.
5774 To stop the whole program, use @code{interrupt -a}.
5776 Other execution commands do not currently support the @code{-a} option.
5778 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5779 that thread current, as it does in all-stop mode. This is because the
5780 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5781 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5782 changed to a different thread just as you entered a command to operate on the
5783 previously current thread.
5785 @node Background Execution
5786 @subsection Background Execution
5788 @cindex foreground execution
5789 @cindex background execution
5790 @cindex asynchronous execution
5791 @cindex execution, foreground, background and asynchronous
5793 @value{GDBN}'s execution commands have two variants: the normal
5794 foreground (synchronous) behavior, and a background
5795 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5796 the program to report that some thread has stopped before prompting for
5797 another command. In background execution, @value{GDBN} immediately gives
5798 a command prompt so that you can issue other commands while your program runs.
5800 You need to explicitly enable asynchronous mode before you can use
5801 background execution commands. You can use these commands to
5802 manipulate the asynchronous mode setting:
5805 @kindex set target-async
5806 @item set target-async on
5807 Enable asynchronous mode.
5808 @item set target-async off
5809 Disable asynchronous mode.
5810 @kindex show target-async
5811 @item show target-async
5812 Show the current target-async setting.
5815 If the target doesn't support async mode, @value{GDBN} issues an error
5816 message if you attempt to use the background execution commands.
5818 To specify background execution, add a @code{&} to the command. For example,
5819 the background form of the @code{continue} command is @code{continue&}, or
5820 just @code{c&}. The execution commands that accept background execution
5826 @xref{Starting, , Starting your Program}.
5830 @xref{Attach, , Debugging an Already-running Process}.
5834 @xref{Continuing and Stepping, step}.
5838 @xref{Continuing and Stepping, stepi}.
5842 @xref{Continuing and Stepping, next}.
5846 @xref{Continuing and Stepping, nexti}.
5850 @xref{Continuing and Stepping, continue}.
5854 @xref{Continuing and Stepping, finish}.
5858 @xref{Continuing and Stepping, until}.
5862 Background execution is especially useful in conjunction with non-stop
5863 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5864 However, you can also use these commands in the normal all-stop mode with
5865 the restriction that you cannot issue another execution command until the
5866 previous one finishes. Examples of commands that are valid in all-stop
5867 mode while the program is running include @code{help} and @code{info break}.
5869 You can interrupt your program while it is running in the background by
5870 using the @code{interrupt} command.
5877 Suspend execution of the running program. In all-stop mode,
5878 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5879 only the current thread. To stop the whole program in non-stop mode,
5880 use @code{interrupt -a}.
5883 @node Thread-Specific Breakpoints
5884 @subsection Thread-Specific Breakpoints
5886 When your program has multiple threads (@pxref{Threads,, Debugging
5887 Programs with Multiple Threads}), you can choose whether to set
5888 breakpoints on all threads, or on a particular thread.
5891 @cindex breakpoints and threads
5892 @cindex thread breakpoints
5893 @kindex break @dots{} thread @var{threadno}
5894 @item break @var{linespec} thread @var{threadno}
5895 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5896 @var{linespec} specifies source lines; there are several ways of
5897 writing them (@pxref{Specify Location}), but the effect is always to
5898 specify some source line.
5900 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5901 to specify that you only want @value{GDBN} to stop the program when a
5902 particular thread reaches this breakpoint. @var{threadno} is one of the
5903 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5904 column of the @samp{info threads} display.
5906 If you do not specify @samp{thread @var{threadno}} when you set a
5907 breakpoint, the breakpoint applies to @emph{all} threads of your
5910 You can use the @code{thread} qualifier on conditional breakpoints as
5911 well; in this case, place @samp{thread @var{threadno}} before or
5912 after the breakpoint condition, like this:
5915 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5920 Thread-specific breakpoints are automatically deleted when
5921 @value{GDBN} detects the corresponding thread is no longer in the
5922 thread list. For example:
5926 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
5929 There are several ways for a thread to disappear, such as a regular
5930 thread exit, but also when you detach from the process with the
5931 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
5932 Process}), or if @value{GDBN} loses the remote connection
5933 (@pxref{Remote Debugging}), etc. Note that with some targets,
5934 @value{GDBN} is only able to detect a thread has exited when the user
5935 explictly asks for the thread list with the @code{info threads}
5938 @node Interrupted System Calls
5939 @subsection Interrupted System Calls
5941 @cindex thread breakpoints and system calls
5942 @cindex system calls and thread breakpoints
5943 @cindex premature return from system calls
5944 There is an unfortunate side effect when using @value{GDBN} to debug
5945 multi-threaded programs. If one thread stops for a
5946 breakpoint, or for some other reason, and another thread is blocked in a
5947 system call, then the system call may return prematurely. This is a
5948 consequence of the interaction between multiple threads and the signals
5949 that @value{GDBN} uses to implement breakpoints and other events that
5952 To handle this problem, your program should check the return value of
5953 each system call and react appropriately. This is good programming
5956 For example, do not write code like this:
5962 The call to @code{sleep} will return early if a different thread stops
5963 at a breakpoint or for some other reason.
5965 Instead, write this:
5970 unslept = sleep (unslept);
5973 A system call is allowed to return early, so the system is still
5974 conforming to its specification. But @value{GDBN} does cause your
5975 multi-threaded program to behave differently than it would without
5978 Also, @value{GDBN} uses internal breakpoints in the thread library to
5979 monitor certain events such as thread creation and thread destruction.
5980 When such an event happens, a system call in another thread may return
5981 prematurely, even though your program does not appear to stop.
5984 @subsection Observer Mode
5986 If you want to build on non-stop mode and observe program behavior
5987 without any chance of disruption by @value{GDBN}, you can set
5988 variables to disable all of the debugger's attempts to modify state,
5989 whether by writing memory, inserting breakpoints, etc. These operate
5990 at a low level, intercepting operations from all commands.
5992 When all of these are set to @code{off}, then @value{GDBN} is said to
5993 be @dfn{observer mode}. As a convenience, the variable
5994 @code{observer} can be set to disable these, plus enable non-stop
5997 Note that @value{GDBN} will not prevent you from making nonsensical
5998 combinations of these settings. For instance, if you have enabled
5999 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6000 then breakpoints that work by writing trap instructions into the code
6001 stream will still not be able to be placed.
6006 @item set observer on
6007 @itemx set observer off
6008 When set to @code{on}, this disables all the permission variables
6009 below (except for @code{insert-fast-tracepoints}), plus enables
6010 non-stop debugging. Setting this to @code{off} switches back to
6011 normal debugging, though remaining in non-stop mode.
6014 Show whether observer mode is on or off.
6016 @kindex may-write-registers
6017 @item set may-write-registers on
6018 @itemx set may-write-registers off
6019 This controls whether @value{GDBN} will attempt to alter the values of
6020 registers, such as with assignment expressions in @code{print}, or the
6021 @code{jump} command. It defaults to @code{on}.
6023 @item show may-write-registers
6024 Show the current permission to write registers.
6026 @kindex may-write-memory
6027 @item set may-write-memory on
6028 @itemx set may-write-memory off
6029 This controls whether @value{GDBN} will attempt to alter the contents
6030 of memory, such as with assignment expressions in @code{print}. It
6031 defaults to @code{on}.
6033 @item show may-write-memory
6034 Show the current permission to write memory.
6036 @kindex may-insert-breakpoints
6037 @item set may-insert-breakpoints on
6038 @itemx set may-insert-breakpoints off
6039 This controls whether @value{GDBN} will attempt to insert breakpoints.
6040 This affects all breakpoints, including internal breakpoints defined
6041 by @value{GDBN}. It defaults to @code{on}.
6043 @item show may-insert-breakpoints
6044 Show the current permission to insert breakpoints.
6046 @kindex may-insert-tracepoints
6047 @item set may-insert-tracepoints on
6048 @itemx set may-insert-tracepoints off
6049 This controls whether @value{GDBN} will attempt to insert (regular)
6050 tracepoints at the beginning of a tracing experiment. It affects only
6051 non-fast tracepoints, fast tracepoints being under the control of
6052 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6054 @item show may-insert-tracepoints
6055 Show the current permission to insert tracepoints.
6057 @kindex may-insert-fast-tracepoints
6058 @item set may-insert-fast-tracepoints on
6059 @itemx set may-insert-fast-tracepoints off
6060 This controls whether @value{GDBN} will attempt to insert fast
6061 tracepoints at the beginning of a tracing experiment. It affects only
6062 fast tracepoints, regular (non-fast) tracepoints being under the
6063 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6065 @item show may-insert-fast-tracepoints
6066 Show the current permission to insert fast tracepoints.
6068 @kindex may-interrupt
6069 @item set may-interrupt on
6070 @itemx set may-interrupt off
6071 This controls whether @value{GDBN} will attempt to interrupt or stop
6072 program execution. When this variable is @code{off}, the
6073 @code{interrupt} command will have no effect, nor will
6074 @kbd{Ctrl-c}. It defaults to @code{on}.
6076 @item show may-interrupt
6077 Show the current permission to interrupt or stop the program.
6081 @node Reverse Execution
6082 @chapter Running programs backward
6083 @cindex reverse execution
6084 @cindex running programs backward
6086 When you are debugging a program, it is not unusual to realize that
6087 you have gone too far, and some event of interest has already happened.
6088 If the target environment supports it, @value{GDBN} can allow you to
6089 ``rewind'' the program by running it backward.
6091 A target environment that supports reverse execution should be able
6092 to ``undo'' the changes in machine state that have taken place as the
6093 program was executing normally. Variables, registers etc.@: should
6094 revert to their previous values. Obviously this requires a great
6095 deal of sophistication on the part of the target environment; not
6096 all target environments can support reverse execution.
6098 When a program is executed in reverse, the instructions that
6099 have most recently been executed are ``un-executed'', in reverse
6100 order. The program counter runs backward, following the previous
6101 thread of execution in reverse. As each instruction is ``un-executed'',
6102 the values of memory and/or registers that were changed by that
6103 instruction are reverted to their previous states. After executing
6104 a piece of source code in reverse, all side effects of that code
6105 should be ``undone'', and all variables should be returned to their
6106 prior values@footnote{
6107 Note that some side effects are easier to undo than others. For instance,
6108 memory and registers are relatively easy, but device I/O is hard. Some
6109 targets may be able undo things like device I/O, and some may not.
6111 The contract between @value{GDBN} and the reverse executing target
6112 requires only that the target do something reasonable when
6113 @value{GDBN} tells it to execute backwards, and then report the
6114 results back to @value{GDBN}. Whatever the target reports back to
6115 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6116 assumes that the memory and registers that the target reports are in a
6117 consistant state, but @value{GDBN} accepts whatever it is given.
6120 If you are debugging in a target environment that supports
6121 reverse execution, @value{GDBN} provides the following commands.
6124 @kindex reverse-continue
6125 @kindex rc @r{(@code{reverse-continue})}
6126 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6127 @itemx rc @r{[}@var{ignore-count}@r{]}
6128 Beginning at the point where your program last stopped, start executing
6129 in reverse. Reverse execution will stop for breakpoints and synchronous
6130 exceptions (signals), just like normal execution. Behavior of
6131 asynchronous signals depends on the target environment.
6133 @kindex reverse-step
6134 @kindex rs @r{(@code{step})}
6135 @item reverse-step @r{[}@var{count}@r{]}
6136 Run the program backward until control reaches the start of a
6137 different source line; then stop it, and return control to @value{GDBN}.
6139 Like the @code{step} command, @code{reverse-step} will only stop
6140 at the beginning of a source line. It ``un-executes'' the previously
6141 executed source line. If the previous source line included calls to
6142 debuggable functions, @code{reverse-step} will step (backward) into
6143 the called function, stopping at the beginning of the @emph{last}
6144 statement in the called function (typically a return statement).
6146 Also, as with the @code{step} command, if non-debuggable functions are
6147 called, @code{reverse-step} will run thru them backward without stopping.
6149 @kindex reverse-stepi
6150 @kindex rsi @r{(@code{reverse-stepi})}
6151 @item reverse-stepi @r{[}@var{count}@r{]}
6152 Reverse-execute one machine instruction. Note that the instruction
6153 to be reverse-executed is @emph{not} the one pointed to by the program
6154 counter, but the instruction executed prior to that one. For instance,
6155 if the last instruction was a jump, @code{reverse-stepi} will take you
6156 back from the destination of the jump to the jump instruction itself.
6158 @kindex reverse-next
6159 @kindex rn @r{(@code{reverse-next})}
6160 @item reverse-next @r{[}@var{count}@r{]}
6161 Run backward to the beginning of the previous line executed in
6162 the current (innermost) stack frame. If the line contains function
6163 calls, they will be ``un-executed'' without stopping. Starting from
6164 the first line of a function, @code{reverse-next} will take you back
6165 to the caller of that function, @emph{before} the function was called,
6166 just as the normal @code{next} command would take you from the last
6167 line of a function back to its return to its caller
6168 @footnote{Unless the code is too heavily optimized.}.
6170 @kindex reverse-nexti
6171 @kindex rni @r{(@code{reverse-nexti})}
6172 @item reverse-nexti @r{[}@var{count}@r{]}
6173 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6174 in reverse, except that called functions are ``un-executed'' atomically.
6175 That is, if the previously executed instruction was a return from
6176 another function, @code{reverse-nexti} will continue to execute
6177 in reverse until the call to that function (from the current stack
6180 @kindex reverse-finish
6181 @item reverse-finish
6182 Just as the @code{finish} command takes you to the point where the
6183 current function returns, @code{reverse-finish} takes you to the point
6184 where it was called. Instead of ending up at the end of the current
6185 function invocation, you end up at the beginning.
6187 @kindex set exec-direction
6188 @item set exec-direction
6189 Set the direction of target execution.
6190 @item set exec-direction reverse
6191 @cindex execute forward or backward in time
6192 @value{GDBN} will perform all execution commands in reverse, until the
6193 exec-direction mode is changed to ``forward''. Affected commands include
6194 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6195 command cannot be used in reverse mode.
6196 @item set exec-direction forward
6197 @value{GDBN} will perform all execution commands in the normal fashion.
6198 This is the default.
6202 @node Process Record and Replay
6203 @chapter Recording Inferior's Execution and Replaying It
6204 @cindex process record and replay
6205 @cindex recording inferior's execution and replaying it
6207 On some platforms, @value{GDBN} provides a special @dfn{process record
6208 and replay} target that can record a log of the process execution, and
6209 replay it later with both forward and reverse execution commands.
6212 When this target is in use, if the execution log includes the record
6213 for the next instruction, @value{GDBN} will debug in @dfn{replay
6214 mode}. In the replay mode, the inferior does not really execute code
6215 instructions. Instead, all the events that normally happen during
6216 code execution are taken from the execution log. While code is not
6217 really executed in replay mode, the values of registers (including the
6218 program counter register) and the memory of the inferior are still
6219 changed as they normally would. Their contents are taken from the
6223 If the record for the next instruction is not in the execution log,
6224 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6225 inferior executes normally, and @value{GDBN} records the execution log
6228 The process record and replay target supports reverse execution
6229 (@pxref{Reverse Execution}), even if the platform on which the
6230 inferior runs does not. However, the reverse execution is limited in
6231 this case by the range of the instructions recorded in the execution
6232 log. In other words, reverse execution on platforms that don't
6233 support it directly can only be done in the replay mode.
6235 When debugging in the reverse direction, @value{GDBN} will work in
6236 replay mode as long as the execution log includes the record for the
6237 previous instruction; otherwise, it will work in record mode, if the
6238 platform supports reverse execution, or stop if not.
6240 For architecture environments that support process record and replay,
6241 @value{GDBN} provides the following commands:
6244 @kindex target record
6245 @kindex target record-full
6246 @kindex target record-btrace
6249 @kindex record btrace
6253 @item record @var{method}
6254 This command starts the process record and replay target. The
6255 recording method can be specified as parameter. Without a parameter
6256 the command uses the @code{full} recording method. The following
6257 recording methods are available:
6261 Full record/replay recording using @value{GDBN}'s software record and
6262 replay implementation. This method allows replaying and reverse
6266 Hardware-supported instruction recording. This method does not record
6267 data. Further, the data is collected in a ring buffer so old data will
6268 be overwritten when the buffer is full. It allows limited replay and
6271 This recording method may not be available on all processors.
6274 The process record and replay target can only debug a process that is
6275 already running. Therefore, you need first to start the process with
6276 the @kbd{run} or @kbd{start} commands, and then start the recording
6277 with the @kbd{record @var{method}} command.
6279 Both @code{record @var{method}} and @code{rec @var{method}} are
6280 aliases of @code{target record-@var{method}}.
6282 @cindex displaced stepping, and process record and replay
6283 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6284 will be automatically disabled when process record and replay target
6285 is started. That's because the process record and replay target
6286 doesn't support displaced stepping.
6288 @cindex non-stop mode, and process record and replay
6289 @cindex asynchronous execution, and process record and replay
6290 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6291 the asynchronous execution mode (@pxref{Background Execution}), not
6292 all recording methods are available. The @code{full} recording method
6293 does not support these two modes.
6298 Stop the process record and replay target. When process record and
6299 replay target stops, the entire execution log will be deleted and the
6300 inferior will either be terminated, or will remain in its final state.
6302 When you stop the process record and replay target in record mode (at
6303 the end of the execution log), the inferior will be stopped at the
6304 next instruction that would have been recorded. In other words, if
6305 you record for a while and then stop recording, the inferior process
6306 will be left in the same state as if the recording never happened.
6308 On the other hand, if the process record and replay target is stopped
6309 while in replay mode (that is, not at the end of the execution log,
6310 but at some earlier point), the inferior process will become ``live''
6311 at that earlier state, and it will then be possible to continue the
6312 usual ``live'' debugging of the process from that state.
6314 When the inferior process exits, or @value{GDBN} detaches from it,
6315 process record and replay target will automatically stop itself.
6319 Go to a specific location in the execution log. There are several
6320 ways to specify the location to go to:
6323 @item record goto begin
6324 @itemx record goto start
6325 Go to the beginning of the execution log.
6327 @item record goto end
6328 Go to the end of the execution log.
6330 @item record goto @var{n}
6331 Go to instruction number @var{n} in the execution log.
6335 @item record save @var{filename}
6336 Save the execution log to a file @file{@var{filename}}.
6337 Default filename is @file{gdb_record.@var{process_id}}, where
6338 @var{process_id} is the process ID of the inferior.
6340 This command may not be available for all recording methods.
6342 @kindex record restore
6343 @item record restore @var{filename}
6344 Restore the execution log from a file @file{@var{filename}}.
6345 File must have been created with @code{record save}.
6347 @kindex set record full
6348 @item set record full insn-number-max @var{limit}
6349 @itemx set record full insn-number-max unlimited
6350 Set the limit of instructions to be recorded for the @code{full}
6351 recording method. Default value is 200000.
6353 If @var{limit} is a positive number, then @value{GDBN} will start
6354 deleting instructions from the log once the number of the record
6355 instructions becomes greater than @var{limit}. For every new recorded
6356 instruction, @value{GDBN} will delete the earliest recorded
6357 instruction to keep the number of recorded instructions at the limit.
6358 (Since deleting recorded instructions loses information, @value{GDBN}
6359 lets you control what happens when the limit is reached, by means of
6360 the @code{stop-at-limit} option, described below.)
6362 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6363 delete recorded instructions from the execution log. The number of
6364 recorded instructions is limited only by the available memory.
6366 @kindex show record full
6367 @item show record full insn-number-max
6368 Show the limit of instructions to be recorded with the @code{full}
6371 @item set record full stop-at-limit
6372 Control the behavior of the @code{full} recording method when the
6373 number of recorded instructions reaches the limit. If ON (the
6374 default), @value{GDBN} will stop when the limit is reached for the
6375 first time and ask you whether you want to stop the inferior or
6376 continue running it and recording the execution log. If you decide
6377 to continue recording, each new recorded instruction will cause the
6378 oldest one to be deleted.
6380 If this option is OFF, @value{GDBN} will automatically delete the
6381 oldest record to make room for each new one, without asking.
6383 @item show record full stop-at-limit
6384 Show the current setting of @code{stop-at-limit}.
6386 @item set record full memory-query
6387 Control the behavior when @value{GDBN} is unable to record memory
6388 changes caused by an instruction for the @code{full} recording method.
6389 If ON, @value{GDBN} will query whether to stop the inferior in that
6392 If this option is OFF (the default), @value{GDBN} will automatically
6393 ignore the effect of such instructions on memory. Later, when
6394 @value{GDBN} replays this execution log, it will mark the log of this
6395 instruction as not accessible, and it will not affect the replay
6398 @item show record full memory-query
6399 Show the current setting of @code{memory-query}.
6403 Show various statistics about the recording depending on the recording
6408 For the @code{full} recording method, it shows the state of process
6409 record and its in-memory execution log buffer, including:
6413 Whether in record mode or replay mode.
6415 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6417 Highest recorded instruction number.
6419 Current instruction about to be replayed (if in replay mode).
6421 Number of instructions contained in the execution log.
6423 Maximum number of instructions that may be contained in the execution log.
6427 For the @code{btrace} recording method, it shows the number of
6428 instructions that have been recorded and the number of blocks of
6429 sequential control-flow that is formed by the recorded instructions.
6432 @kindex record delete
6435 When record target runs in replay mode (``in the past''), delete the
6436 subsequent execution log and begin to record a new execution log starting
6437 from the current address. This means you will abandon the previously
6438 recorded ``future'' and begin recording a new ``future''.
6440 @kindex record instruction-history
6441 @kindex rec instruction-history
6442 @item record instruction-history
6443 Disassembles instructions from the recorded execution log. By
6444 default, ten instructions are disassembled. This can be changed using
6445 the @code{set record instruction-history-size} command. Instructions
6446 are printed in execution order. There are several ways to specify
6447 what part of the execution log to disassemble:
6450 @item record instruction-history @var{insn}
6451 Disassembles ten instructions starting from instruction number
6454 @item record instruction-history @var{insn}, +/-@var{n}
6455 Disassembles @var{n} instructions around instruction number
6456 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
6457 @var{n} instructions after instruction number @var{insn}. If
6458 @var{n} is preceded with @code{-}, disassembles @var{n}
6459 instructions before instruction number @var{insn}.
6461 @item record instruction-history
6462 Disassembles ten more instructions after the last disassembly.
6464 @item record instruction-history -
6465 Disassembles ten more instructions before the last disassembly.
6467 @item record instruction-history @var{begin} @var{end}
6468 Disassembles instructions beginning with instruction number
6469 @var{begin} until instruction number @var{end}. The instruction
6470 number @var{end} is included.
6473 This command may not be available for all recording methods.
6476 @item set record instruction-history-size @var{size}
6477 @itemx set record instruction-history-size unlimited
6478 Define how many instructions to disassemble in the @code{record
6479 instruction-history} command. The default value is 10.
6480 A @var{size} of @code{unlimited} means unlimited instructions.
6483 @item show record instruction-history-size
6484 Show how many instructions to disassemble in the @code{record
6485 instruction-history} command.
6487 @kindex record function-call-history
6488 @kindex rec function-call-history
6489 @item record function-call-history
6490 Prints the execution history at function granularity. It prints one
6491 line for each sequence of instructions that belong to the same
6492 function giving the name of that function, the source lines
6493 for this instruction sequence (if the @code{/l} modifier is
6494 specified), and the instructions numbers that form the sequence (if
6495 the @code{/i} modifier is specified). The function names are indented
6496 to reflect the call stack depth if the @code{/c} modifier is
6497 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
6501 (@value{GDBP}) @b{list 1, 10}
6512 (@value{GDBP}) @b{record function-call-history /ilc}
6513 1 bar inst 1,4 at foo.c:6,8
6514 2 foo inst 5,10 at foo.c:2,3
6515 3 bar inst 11,13 at foo.c:9,10
6518 By default, ten lines are printed. This can be changed using the
6519 @code{set record function-call-history-size} command. Functions are
6520 printed in execution order. There are several ways to specify what
6524 @item record function-call-history @var{func}
6525 Prints ten functions starting from function number @var{func}.
6527 @item record function-call-history @var{func}, +/-@var{n}
6528 Prints @var{n} functions around function number @var{func}. If
6529 @var{n} is preceded with @code{+}, prints @var{n} functions after
6530 function number @var{func}. If @var{n} is preceded with @code{-},
6531 prints @var{n} functions before function number @var{func}.
6533 @item record function-call-history
6534 Prints ten more functions after the last ten-line print.
6536 @item record function-call-history -
6537 Prints ten more functions before the last ten-line print.
6539 @item record function-call-history @var{begin} @var{end}
6540 Prints functions beginning with function number @var{begin} until
6541 function number @var{end}. The function number @var{end} is included.
6544 This command may not be available for all recording methods.
6546 @item set record function-call-history-size @var{size}
6547 @itemx set record function-call-history-size unlimited
6548 Define how many lines to print in the
6549 @code{record function-call-history} command. The default value is 10.
6550 A size of @code{unlimited} means unlimited lines.
6552 @item show record function-call-history-size
6553 Show how many lines to print in the
6554 @code{record function-call-history} command.
6559 @chapter Examining the Stack
6561 When your program has stopped, the first thing you need to know is where it
6562 stopped and how it got there.
6565 Each time your program performs a function call, information about the call
6567 That information includes the location of the call in your program,
6568 the arguments of the call,
6569 and the local variables of the function being called.
6570 The information is saved in a block of data called a @dfn{stack frame}.
6571 The stack frames are allocated in a region of memory called the @dfn{call
6574 When your program stops, the @value{GDBN} commands for examining the
6575 stack allow you to see all of this information.
6577 @cindex selected frame
6578 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6579 @value{GDBN} commands refer implicitly to the selected frame. In
6580 particular, whenever you ask @value{GDBN} for the value of a variable in
6581 your program, the value is found in the selected frame. There are
6582 special @value{GDBN} commands to select whichever frame you are
6583 interested in. @xref{Selection, ,Selecting a Frame}.
6585 When your program stops, @value{GDBN} automatically selects the
6586 currently executing frame and describes it briefly, similar to the
6587 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6590 * Frames:: Stack frames
6591 * Backtrace:: Backtraces
6592 * Frame Filter Management:: Managing frame filters
6593 * Selection:: Selecting a frame
6594 * Frame Info:: Information on a frame
6599 @section Stack Frames
6601 @cindex frame, definition
6603 The call stack is divided up into contiguous pieces called @dfn{stack
6604 frames}, or @dfn{frames} for short; each frame is the data associated
6605 with one call to one function. The frame contains the arguments given
6606 to the function, the function's local variables, and the address at
6607 which the function is executing.
6609 @cindex initial frame
6610 @cindex outermost frame
6611 @cindex innermost frame
6612 When your program is started, the stack has only one frame, that of the
6613 function @code{main}. This is called the @dfn{initial} frame or the
6614 @dfn{outermost} frame. Each time a function is called, a new frame is
6615 made. Each time a function returns, the frame for that function invocation
6616 is eliminated. If a function is recursive, there can be many frames for
6617 the same function. The frame for the function in which execution is
6618 actually occurring is called the @dfn{innermost} frame. This is the most
6619 recently created of all the stack frames that still exist.
6621 @cindex frame pointer
6622 Inside your program, stack frames are identified by their addresses. A
6623 stack frame consists of many bytes, each of which has its own address; each
6624 kind of computer has a convention for choosing one byte whose
6625 address serves as the address of the frame. Usually this address is kept
6626 in a register called the @dfn{frame pointer register}
6627 (@pxref{Registers, $fp}) while execution is going on in that frame.
6629 @cindex frame number
6630 @value{GDBN} assigns numbers to all existing stack frames, starting with
6631 zero for the innermost frame, one for the frame that called it,
6632 and so on upward. These numbers do not really exist in your program;
6633 they are assigned by @value{GDBN} to give you a way of designating stack
6634 frames in @value{GDBN} commands.
6636 @c The -fomit-frame-pointer below perennially causes hbox overflow
6637 @c underflow problems.
6638 @cindex frameless execution
6639 Some compilers provide a way to compile functions so that they operate
6640 without stack frames. (For example, the @value{NGCC} option
6642 @samp{-fomit-frame-pointer}
6644 generates functions without a frame.)
6645 This is occasionally done with heavily used library functions to save
6646 the frame setup time. @value{GDBN} has limited facilities for dealing
6647 with these function invocations. If the innermost function invocation
6648 has no stack frame, @value{GDBN} nevertheless regards it as though
6649 it had a separate frame, which is numbered zero as usual, allowing
6650 correct tracing of the function call chain. However, @value{GDBN} has
6651 no provision for frameless functions elsewhere in the stack.
6654 @kindex frame@r{, command}
6655 @cindex current stack frame
6656 @item frame @var{args}
6657 The @code{frame} command allows you to move from one stack frame to another,
6658 and to print the stack frame you select. @var{args} may be either the
6659 address of the frame or the stack frame number. Without an argument,
6660 @code{frame} prints the current stack frame.
6662 @kindex select-frame
6663 @cindex selecting frame silently
6665 The @code{select-frame} command allows you to move from one stack frame
6666 to another without printing the frame. This is the silent version of
6674 @cindex call stack traces
6675 A backtrace is a summary of how your program got where it is. It shows one
6676 line per frame, for many frames, starting with the currently executing
6677 frame (frame zero), followed by its caller (frame one), and on up the
6680 @anchor{backtrace-command}
6683 @kindex bt @r{(@code{backtrace})}
6686 Print a backtrace of the entire stack: one line per frame for all
6687 frames in the stack.
6689 You can stop the backtrace at any time by typing the system interrupt
6690 character, normally @kbd{Ctrl-c}.
6692 @item backtrace @var{n}
6694 Similar, but print only the innermost @var{n} frames.
6696 @item backtrace -@var{n}
6698 Similar, but print only the outermost @var{n} frames.
6700 @item backtrace full
6702 @itemx bt full @var{n}
6703 @itemx bt full -@var{n}
6704 Print the values of the local variables also. @var{n} specifies the
6705 number of frames to print, as described above.
6707 @item backtrace no-filters
6708 @itemx bt no-filters
6709 @itemx bt no-filters @var{n}
6710 @itemx bt no-filters -@var{n}
6711 @itemx bt no-filters full
6712 @itemx bt no-filters full @var{n}
6713 @itemx bt no-filters full -@var{n}
6714 Do not run Python frame filters on this backtrace. @xref{Frame
6715 Filter API}, for more information. Additionally use @ref{disable
6716 frame-filter all} to turn off all frame filters. This is only
6717 relevant when @value{GDBN} has been configured with @code{Python}
6723 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6724 are additional aliases for @code{backtrace}.
6726 @cindex multiple threads, backtrace
6727 In a multi-threaded program, @value{GDBN} by default shows the
6728 backtrace only for the current thread. To display the backtrace for
6729 several or all of the threads, use the command @code{thread apply}
6730 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6731 apply all backtrace}, @value{GDBN} will display the backtrace for all
6732 the threads; this is handy when you debug a core dump of a
6733 multi-threaded program.
6735 Each line in the backtrace shows the frame number and the function name.
6736 The program counter value is also shown---unless you use @code{set
6737 print address off}. The backtrace also shows the source file name and
6738 line number, as well as the arguments to the function. The program
6739 counter value is omitted if it is at the beginning of the code for that
6742 Here is an example of a backtrace. It was made with the command
6743 @samp{bt 3}, so it shows the innermost three frames.
6747 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6749 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
6750 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
6752 (More stack frames follow...)
6757 The display for frame zero does not begin with a program counter
6758 value, indicating that your program has stopped at the beginning of the
6759 code for line @code{993} of @code{builtin.c}.
6762 The value of parameter @code{data} in frame 1 has been replaced by
6763 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
6764 only if it is a scalar (integer, pointer, enumeration, etc). See command
6765 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
6766 on how to configure the way function parameter values are printed.
6768 @cindex optimized out, in backtrace
6769 @cindex function call arguments, optimized out
6770 If your program was compiled with optimizations, some compilers will
6771 optimize away arguments passed to functions if those arguments are
6772 never used after the call. Such optimizations generate code that
6773 passes arguments through registers, but doesn't store those arguments
6774 in the stack frame. @value{GDBN} has no way of displaying such
6775 arguments in stack frames other than the innermost one. Here's what
6776 such a backtrace might look like:
6780 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6782 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6783 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6785 (More stack frames follow...)
6790 The values of arguments that were not saved in their stack frames are
6791 shown as @samp{<optimized out>}.
6793 If you need to display the values of such optimized-out arguments,
6794 either deduce that from other variables whose values depend on the one
6795 you are interested in, or recompile without optimizations.
6797 @cindex backtrace beyond @code{main} function
6798 @cindex program entry point
6799 @cindex startup code, and backtrace
6800 Most programs have a standard user entry point---a place where system
6801 libraries and startup code transition into user code. For C this is
6802 @code{main}@footnote{
6803 Note that embedded programs (the so-called ``free-standing''
6804 environment) are not required to have a @code{main} function as the
6805 entry point. They could even have multiple entry points.}.
6806 When @value{GDBN} finds the entry function in a backtrace
6807 it will terminate the backtrace, to avoid tracing into highly
6808 system-specific (and generally uninteresting) code.
6810 If you need to examine the startup code, or limit the number of levels
6811 in a backtrace, you can change this behavior:
6814 @item set backtrace past-main
6815 @itemx set backtrace past-main on
6816 @kindex set backtrace
6817 Backtraces will continue past the user entry point.
6819 @item set backtrace past-main off
6820 Backtraces will stop when they encounter the user entry point. This is the
6823 @item show backtrace past-main
6824 @kindex show backtrace
6825 Display the current user entry point backtrace policy.
6827 @item set backtrace past-entry
6828 @itemx set backtrace past-entry on
6829 Backtraces will continue past the internal entry point of an application.
6830 This entry point is encoded by the linker when the application is built,
6831 and is likely before the user entry point @code{main} (or equivalent) is called.
6833 @item set backtrace past-entry off
6834 Backtraces will stop when they encounter the internal entry point of an
6835 application. This is the default.
6837 @item show backtrace past-entry
6838 Display the current internal entry point backtrace policy.
6840 @item set backtrace limit @var{n}
6841 @itemx set backtrace limit 0
6842 @itemx set backtrace limit unlimited
6843 @cindex backtrace limit
6844 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
6845 or zero means unlimited levels.
6847 @item show backtrace limit
6848 Display the current limit on backtrace levels.
6851 You can control how file names are displayed.
6854 @item set filename-display
6855 @itemx set filename-display relative
6856 @cindex filename-display
6857 Display file names relative to the compilation directory. This is the default.
6859 @item set filename-display basename
6860 Display only basename of a filename.
6862 @item set filename-display absolute
6863 Display an absolute filename.
6865 @item show filename-display
6866 Show the current way to display filenames.
6869 @node Frame Filter Management
6870 @section Management of Frame Filters.
6871 @cindex managing frame filters
6873 Frame filters are Python based utilities to manage and decorate the
6874 output of frames. @xref{Frame Filter API}, for further information.
6876 Managing frame filters is performed by several commands available
6877 within @value{GDBN}, detailed here.
6880 @kindex info frame-filter
6881 @item info frame-filter
6882 Print a list of installed frame filters from all dictionaries, showing
6883 their name, priority and enabled status.
6885 @kindex disable frame-filter
6886 @anchor{disable frame-filter all}
6887 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
6888 Disable a frame filter in the dictionary matching
6889 @var{filter-dictionary}, or @code{all}, and @var{filter-name}.
6890 @var{filter-dictionary} may be @code{all}, @code{global},
6891 @code{progspace} or the name of the object file where the frame filter
6892 dictionary resides. When @code{all} is specified, all frame filters
6893 across all dictionaries are disabled. @var{filter-name} is the name
6894 of the frame filter and is used when @code{all} is not the option for
6895 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
6896 may be enabled again later.
6898 @kindex enable frame-filter
6899 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
6900 Enable a frame filter in the dictionary matching
6901 @var{filter-dictionary}, or @code{all}, and @var{filter-name}.
6902 @var{filter-dictionary} may be @code{all}, @code{global},
6903 @code{progspace} or the name of the object file where the frame filter
6904 dictionary resides. When @code{all} is specified, all frame filters across
6905 all dictionaries are enabled. @var{filter-name} is the name of the frame
6906 filter and is used when @code{all} is not the option for
6907 @var{filter-dictionary}.
6912 (gdb) info frame-filter
6914 global frame-filters:
6915 Priority Enabled Name
6916 1000 No PrimaryFunctionFilter
6919 progspace /build/test frame-filters:
6920 Priority Enabled Name
6921 100 Yes ProgspaceFilter
6923 objfile /build/test frame-filters:
6924 Priority Enabled Name
6925 999 Yes BuildProgra Filter
6927 (gdb) disable frame-filter /build/test BuildProgramFilter
6928 (gdb) info frame-filter
6930 global frame-filters:
6931 Priority Enabled Name
6932 1000 No PrimaryFunctionFilter
6935 progspace /build/test frame-filters:
6936 Priority Enabled Name
6937 100 Yes ProgspaceFilter
6939 objfile /build/test frame-filters:
6940 Priority Enabled Name
6941 999 No BuildProgramFilter
6943 (gdb) enable frame-filter global PrimaryFunctionFilter
6944 (gdb) info frame-filter
6946 global frame-filters:
6947 Priority Enabled Name
6948 1000 Yes PrimaryFunctionFilter
6951 progspace /build/test frame-filters:
6952 Priority Enabled Name
6953 100 Yes ProgspaceFilter
6955 objfile /build/test frame-filters:
6956 Priority Enabled Name
6957 999 No BuildProgramFilter
6960 @kindex set frame-filter priority
6961 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
6962 Set the @var{priority} of a frame filter in the dictionary matching
6963 @var{filter-dictionary}, and the frame filter name matching
6964 @var{filter-name}. @var{filter-dictionary} may be @code{global},
6965 @code{progspace} or the name of the object file where the frame filter
6966 dictionary resides. @var{priority} is an integer.
6968 @kindex show frame-filter priority
6969 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
6970 Show the @var{priority} of a frame filter in the dictionary matching
6971 @var{filter-dictionary}, and the frame filter name matching
6972 @var{filter-name}. @var{filter-dictionary} may be @code{global},
6973 @code{progspace} or the name of the object file where the frame filter
6979 (gdb) info frame-filter
6981 global frame-filters:
6982 Priority Enabled Name
6983 1000 Yes PrimaryFunctionFilter
6986 progspace /build/test frame-filters:
6987 Priority Enabled Name
6988 100 Yes ProgspaceFilter
6990 objfile /build/test frame-filters:
6991 Priority Enabled Name
6992 999 No BuildProgramFilter
6994 (gdb) set frame-filter priority global Reverse 50
6995 (gdb) info frame-filter
6997 global frame-filters:
6998 Priority Enabled Name
6999 1000 Yes PrimaryFunctionFilter
7002 progspace /build/test frame-filters:
7003 Priority Enabled Name
7004 100 Yes ProgspaceFilter
7006 objfile /build/test frame-filters:
7007 Priority Enabled Name
7008 999 No BuildProgramFilter
7013 @section Selecting a Frame
7015 Most commands for examining the stack and other data in your program work on
7016 whichever stack frame is selected at the moment. Here are the commands for
7017 selecting a stack frame; all of them finish by printing a brief description
7018 of the stack frame just selected.
7021 @kindex frame@r{, selecting}
7022 @kindex f @r{(@code{frame})}
7025 Select frame number @var{n}. Recall that frame zero is the innermost
7026 (currently executing) frame, frame one is the frame that called the
7027 innermost one, and so on. The highest-numbered frame is the one for
7030 @item frame @var{addr}
7032 Select the frame at address @var{addr}. This is useful mainly if the
7033 chaining of stack frames has been damaged by a bug, making it
7034 impossible for @value{GDBN} to assign numbers properly to all frames. In
7035 addition, this can be useful when your program has multiple stacks and
7036 switches between them.
7038 On the SPARC architecture, @code{frame} needs two addresses to
7039 select an arbitrary frame: a frame pointer and a stack pointer.
7041 On the @acronym{MIPS} and Alpha architecture, it needs two addresses: a stack
7042 pointer and a program counter.
7044 On the 29k architecture, it needs three addresses: a register stack
7045 pointer, a program counter, and a memory stack pointer.
7049 Move @var{n} frames up the stack. For positive numbers @var{n}, this
7050 advances toward the outermost frame, to higher frame numbers, to frames
7051 that have existed longer. @var{n} defaults to one.
7054 @kindex do @r{(@code{down})}
7056 Move @var{n} frames down the stack. For positive numbers @var{n}, this
7057 advances toward the innermost frame, to lower frame numbers, to frames
7058 that were created more recently. @var{n} defaults to one. You may
7059 abbreviate @code{down} as @code{do}.
7062 All of these commands end by printing two lines of output describing the
7063 frame. The first line shows the frame number, the function name, the
7064 arguments, and the source file and line number of execution in that
7065 frame. The second line shows the text of that source line.
7073 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7075 10 read_input_file (argv[i]);
7079 After such a printout, the @code{list} command with no arguments
7080 prints ten lines centered on the point of execution in the frame.
7081 You can also edit the program at the point of execution with your favorite
7082 editing program by typing @code{edit}.
7083 @xref{List, ,Printing Source Lines},
7087 @kindex down-silently
7089 @item up-silently @var{n}
7090 @itemx down-silently @var{n}
7091 These two commands are variants of @code{up} and @code{down},
7092 respectively; they differ in that they do their work silently, without
7093 causing display of the new frame. They are intended primarily for use
7094 in @value{GDBN} command scripts, where the output might be unnecessary and
7099 @section Information About a Frame
7101 There are several other commands to print information about the selected
7107 When used without any argument, this command does not change which
7108 frame is selected, but prints a brief description of the currently
7109 selected stack frame. It can be abbreviated @code{f}. With an
7110 argument, this command is used to select a stack frame.
7111 @xref{Selection, ,Selecting a Frame}.
7114 @kindex info f @r{(@code{info frame})}
7117 This command prints a verbose description of the selected stack frame,
7122 the address of the frame
7124 the address of the next frame down (called by this frame)
7126 the address of the next frame up (caller of this frame)
7128 the language in which the source code corresponding to this frame is written
7130 the address of the frame's arguments
7132 the address of the frame's local variables
7134 the program counter saved in it (the address of execution in the caller frame)
7136 which registers were saved in the frame
7139 @noindent The verbose description is useful when
7140 something has gone wrong that has made the stack format fail to fit
7141 the usual conventions.
7143 @item info frame @var{addr}
7144 @itemx info f @var{addr}
7145 Print a verbose description of the frame at address @var{addr}, without
7146 selecting that frame. The selected frame remains unchanged by this
7147 command. This requires the same kind of address (more than one for some
7148 architectures) that you specify in the @code{frame} command.
7149 @xref{Selection, ,Selecting a Frame}.
7153 Print the arguments of the selected frame, each on a separate line.
7157 Print the local variables of the selected frame, each on a separate
7158 line. These are all variables (declared either static or automatic)
7159 accessible at the point of execution of the selected frame.
7165 @chapter Examining Source Files
7167 @value{GDBN} can print parts of your program's source, since the debugging
7168 information recorded in the program tells @value{GDBN} what source files were
7169 used to build it. When your program stops, @value{GDBN} spontaneously prints
7170 the line where it stopped. Likewise, when you select a stack frame
7171 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
7172 execution in that frame has stopped. You can print other portions of
7173 source files by explicit command.
7175 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
7176 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
7177 @value{GDBN} under @sc{gnu} Emacs}.
7180 * List:: Printing source lines
7181 * Specify Location:: How to specify code locations
7182 * Edit:: Editing source files
7183 * Search:: Searching source files
7184 * Source Path:: Specifying source directories
7185 * Machine Code:: Source and machine code
7189 @section Printing Source Lines
7192 @kindex l @r{(@code{list})}
7193 To print lines from a source file, use the @code{list} command
7194 (abbreviated @code{l}). By default, ten lines are printed.
7195 There are several ways to specify what part of the file you want to
7196 print; see @ref{Specify Location}, for the full list.
7198 Here are the forms of the @code{list} command most commonly used:
7201 @item list @var{linenum}
7202 Print lines centered around line number @var{linenum} in the
7203 current source file.
7205 @item list @var{function}
7206 Print lines centered around the beginning of function
7210 Print more lines. If the last lines printed were printed with a
7211 @code{list} command, this prints lines following the last lines
7212 printed; however, if the last line printed was a solitary line printed
7213 as part of displaying a stack frame (@pxref{Stack, ,Examining the
7214 Stack}), this prints lines centered around that line.
7217 Print lines just before the lines last printed.
7220 @cindex @code{list}, how many lines to display
7221 By default, @value{GDBN} prints ten source lines with any of these forms of
7222 the @code{list} command. You can change this using @code{set listsize}:
7225 @kindex set listsize
7226 @item set listsize @var{count}
7227 @itemx set listsize unlimited
7228 Make the @code{list} command display @var{count} source lines (unless
7229 the @code{list} argument explicitly specifies some other number).
7230 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
7232 @kindex show listsize
7234 Display the number of lines that @code{list} prints.
7237 Repeating a @code{list} command with @key{RET} discards the argument,
7238 so it is equivalent to typing just @code{list}. This is more useful
7239 than listing the same lines again. An exception is made for an
7240 argument of @samp{-}; that argument is preserved in repetition so that
7241 each repetition moves up in the source file.
7243 In general, the @code{list} command expects you to supply zero, one or two
7244 @dfn{linespecs}. Linespecs specify source lines; there are several ways
7245 of writing them (@pxref{Specify Location}), but the effect is always
7246 to specify some source line.
7248 Here is a complete description of the possible arguments for @code{list}:
7251 @item list @var{linespec}
7252 Print lines centered around the line specified by @var{linespec}.
7254 @item list @var{first},@var{last}
7255 Print lines from @var{first} to @var{last}. Both arguments are
7256 linespecs. When a @code{list} command has two linespecs, and the
7257 source file of the second linespec is omitted, this refers to
7258 the same source file as the first linespec.
7260 @item list ,@var{last}
7261 Print lines ending with @var{last}.
7263 @item list @var{first},
7264 Print lines starting with @var{first}.
7267 Print lines just after the lines last printed.
7270 Print lines just before the lines last printed.
7273 As described in the preceding table.
7276 @node Specify Location
7277 @section Specifying a Location
7278 @cindex specifying location
7281 Several @value{GDBN} commands accept arguments that specify a location
7282 of your program's code. Since @value{GDBN} is a source-level
7283 debugger, a location usually specifies some line in the source code;
7284 for that reason, locations are also known as @dfn{linespecs}.
7286 Here are all the different ways of specifying a code location that
7287 @value{GDBN} understands:
7291 Specifies the line number @var{linenum} of the current source file.
7294 @itemx +@var{offset}
7295 Specifies the line @var{offset} lines before or after the @dfn{current
7296 line}. For the @code{list} command, the current line is the last one
7297 printed; for the breakpoint commands, this is the line at which
7298 execution stopped in the currently selected @dfn{stack frame}
7299 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7300 used as the second of the two linespecs in a @code{list} command,
7301 this specifies the line @var{offset} lines up or down from the first
7304 @item @var{filename}:@var{linenum}
7305 Specifies the line @var{linenum} in the source file @var{filename}.
7306 If @var{filename} is a relative file name, then it will match any
7307 source file name with the same trailing components. For example, if
7308 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7309 name of @file{/build/trunk/gcc/expr.c}, but not
7310 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7312 @item @var{function}
7313 Specifies the line that begins the body of the function @var{function}.
7314 For example, in C, this is the line with the open brace.
7316 @item @var{function}:@var{label}
7317 Specifies the line where @var{label} appears in @var{function}.
7319 @item @var{filename}:@var{function}
7320 Specifies the line that begins the body of the function @var{function}
7321 in the file @var{filename}. You only need the file name with a
7322 function name to avoid ambiguity when there are identically named
7323 functions in different source files.
7326 Specifies the line at which the label named @var{label} appears.
7327 @value{GDBN} searches for the label in the function corresponding to
7328 the currently selected stack frame. If there is no current selected
7329 stack frame (for instance, if the inferior is not running), then
7330 @value{GDBN} will not search for a label.
7332 @item *@var{address}
7333 Specifies the program address @var{address}. For line-oriented
7334 commands, such as @code{list} and @code{edit}, this specifies a source
7335 line that contains @var{address}. For @code{break} and other
7336 breakpoint oriented commands, this can be used to set breakpoints in
7337 parts of your program which do not have debugging information or
7340 Here @var{address} may be any expression valid in the current working
7341 language (@pxref{Languages, working language}) that specifies a code
7342 address. In addition, as a convenience, @value{GDBN} extends the
7343 semantics of expressions used in locations to cover the situations
7344 that frequently happen during debugging. Here are the various forms
7348 @item @var{expression}
7349 Any expression valid in the current working language.
7351 @item @var{funcaddr}
7352 An address of a function or procedure derived from its name. In C,
7353 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
7354 simply the function's name @var{function} (and actually a special case
7355 of a valid expression). In Pascal and Modula-2, this is
7356 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
7357 (although the Pascal form also works).
7359 This form specifies the address of the function's first instruction,
7360 before the stack frame and arguments have been set up.
7362 @item '@var{filename}'::@var{funcaddr}
7363 Like @var{funcaddr} above, but also specifies the name of the source
7364 file explicitly. This is useful if the name of the function does not
7365 specify the function unambiguously, e.g., if there are several
7366 functions with identical names in different source files.
7369 @cindex breakpoint at static probe point
7370 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7371 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7372 applications to embed static probes. @xref{Static Probe Points}, for more
7373 information on finding and using static probes. This form of linespec
7374 specifies the location of such a static probe.
7376 If @var{objfile} is given, only probes coming from that shared library
7377 or executable matching @var{objfile} as a regular expression are considered.
7378 If @var{provider} is given, then only probes from that provider are considered.
7379 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7380 each one of those probes.
7386 @section Editing Source Files
7387 @cindex editing source files
7390 @kindex e @r{(@code{edit})}
7391 To edit the lines in a source file, use the @code{edit} command.
7392 The editing program of your choice
7393 is invoked with the current line set to
7394 the active line in the program.
7395 Alternatively, there are several ways to specify what part of the file you
7396 want to print if you want to see other parts of the program:
7399 @item edit @var{location}
7400 Edit the source file specified by @code{location}. Editing starts at
7401 that @var{location}, e.g., at the specified source line of the
7402 specified file. @xref{Specify Location}, for all the possible forms
7403 of the @var{location} argument; here are the forms of the @code{edit}
7404 command most commonly used:
7407 @item edit @var{number}
7408 Edit the current source file with @var{number} as the active line number.
7410 @item edit @var{function}
7411 Edit the file containing @var{function} at the beginning of its definition.
7416 @subsection Choosing your Editor
7417 You can customize @value{GDBN} to use any editor you want
7419 The only restriction is that your editor (say @code{ex}), recognizes the
7420 following command-line syntax:
7422 ex +@var{number} file
7424 The optional numeric value +@var{number} specifies the number of the line in
7425 the file where to start editing.}.
7426 By default, it is @file{@value{EDITOR}}, but you can change this
7427 by setting the environment variable @code{EDITOR} before using
7428 @value{GDBN}. For example, to configure @value{GDBN} to use the
7429 @code{vi} editor, you could use these commands with the @code{sh} shell:
7435 or in the @code{csh} shell,
7437 setenv EDITOR /usr/bin/vi
7442 @section Searching Source Files
7443 @cindex searching source files
7445 There are two commands for searching through the current source file for a
7450 @kindex forward-search
7451 @kindex fo @r{(@code{forward-search})}
7452 @item forward-search @var{regexp}
7453 @itemx search @var{regexp}
7454 The command @samp{forward-search @var{regexp}} checks each line,
7455 starting with the one following the last line listed, for a match for
7456 @var{regexp}. It lists the line that is found. You can use the
7457 synonym @samp{search @var{regexp}} or abbreviate the command name as
7460 @kindex reverse-search
7461 @item reverse-search @var{regexp}
7462 The command @samp{reverse-search @var{regexp}} checks each line, starting
7463 with the one before the last line listed and going backward, for a match
7464 for @var{regexp}. It lists the line that is found. You can abbreviate
7465 this command as @code{rev}.
7469 @section Specifying Source Directories
7472 @cindex directories for source files
7473 Executable programs sometimes do not record the directories of the source
7474 files from which they were compiled, just the names. Even when they do,
7475 the directories could be moved between the compilation and your debugging
7476 session. @value{GDBN} has a list of directories to search for source files;
7477 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
7478 it tries all the directories in the list, in the order they are present
7479 in the list, until it finds a file with the desired name.
7481 For example, suppose an executable references the file
7482 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
7483 @file{/mnt/cross}. The file is first looked up literally; if this
7484 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
7485 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
7486 message is printed. @value{GDBN} does not look up the parts of the
7487 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
7488 Likewise, the subdirectories of the source path are not searched: if
7489 the source path is @file{/mnt/cross}, and the binary refers to
7490 @file{foo.c}, @value{GDBN} would not find it under
7491 @file{/mnt/cross/usr/src/foo-1.0/lib}.
7493 Plain file names, relative file names with leading directories, file
7494 names containing dots, etc.@: are all treated as described above; for
7495 instance, if the source path is @file{/mnt/cross}, and the source file
7496 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
7497 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
7498 that---@file{/mnt/cross/foo.c}.
7500 Note that the executable search path is @emph{not} used to locate the
7503 Whenever you reset or rearrange the source path, @value{GDBN} clears out
7504 any information it has cached about where source files are found and where
7505 each line is in the file.
7509 When you start @value{GDBN}, its source path includes only @samp{cdir}
7510 and @samp{cwd}, in that order.
7511 To add other directories, use the @code{directory} command.
7513 The search path is used to find both program source files and @value{GDBN}
7514 script files (read using the @samp{-command} option and @samp{source} command).
7516 In addition to the source path, @value{GDBN} provides a set of commands
7517 that manage a list of source path substitution rules. A @dfn{substitution
7518 rule} specifies how to rewrite source directories stored in the program's
7519 debug information in case the sources were moved to a different
7520 directory between compilation and debugging. A rule is made of
7521 two strings, the first specifying what needs to be rewritten in
7522 the path, and the second specifying how it should be rewritten.
7523 In @ref{set substitute-path}, we name these two parts @var{from} and
7524 @var{to} respectively. @value{GDBN} does a simple string replacement
7525 of @var{from} with @var{to} at the start of the directory part of the
7526 source file name, and uses that result instead of the original file
7527 name to look up the sources.
7529 Using the previous example, suppose the @file{foo-1.0} tree has been
7530 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
7531 @value{GDBN} to replace @file{/usr/src} in all source path names with
7532 @file{/mnt/cross}. The first lookup will then be
7533 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
7534 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
7535 substitution rule, use the @code{set substitute-path} command
7536 (@pxref{set substitute-path}).
7538 To avoid unexpected substitution results, a rule is applied only if the
7539 @var{from} part of the directory name ends at a directory separator.
7540 For instance, a rule substituting @file{/usr/source} into
7541 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
7542 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
7543 is applied only at the beginning of the directory name, this rule will
7544 not be applied to @file{/root/usr/source/baz.c} either.
7546 In many cases, you can achieve the same result using the @code{directory}
7547 command. However, @code{set substitute-path} can be more efficient in
7548 the case where the sources are organized in a complex tree with multiple
7549 subdirectories. With the @code{directory} command, you need to add each
7550 subdirectory of your project. If you moved the entire tree while
7551 preserving its internal organization, then @code{set substitute-path}
7552 allows you to direct the debugger to all the sources with one single
7555 @code{set substitute-path} is also more than just a shortcut command.
7556 The source path is only used if the file at the original location no
7557 longer exists. On the other hand, @code{set substitute-path} modifies
7558 the debugger behavior to look at the rewritten location instead. So, if
7559 for any reason a source file that is not relevant to your executable is
7560 located at the original location, a substitution rule is the only
7561 method available to point @value{GDBN} at the new location.
7563 @cindex @samp{--with-relocated-sources}
7564 @cindex default source path substitution
7565 You can configure a default source path substitution rule by
7566 configuring @value{GDBN} with the
7567 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
7568 should be the name of a directory under @value{GDBN}'s configured
7569 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
7570 directory names in debug information under @var{dir} will be adjusted
7571 automatically if the installed @value{GDBN} is moved to a new
7572 location. This is useful if @value{GDBN}, libraries or executables
7573 with debug information and corresponding source code are being moved
7577 @item directory @var{dirname} @dots{}
7578 @item dir @var{dirname} @dots{}
7579 Add directory @var{dirname} to the front of the source path. Several
7580 directory names may be given to this command, separated by @samp{:}
7581 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
7582 part of absolute file names) or
7583 whitespace. You may specify a directory that is already in the source
7584 path; this moves it forward, so @value{GDBN} searches it sooner.
7588 @vindex $cdir@r{, convenience variable}
7589 @vindex $cwd@r{, convenience variable}
7590 @cindex compilation directory
7591 @cindex current directory
7592 @cindex working directory
7593 @cindex directory, current
7594 @cindex directory, compilation
7595 You can use the string @samp{$cdir} to refer to the compilation
7596 directory (if one is recorded), and @samp{$cwd} to refer to the current
7597 working directory. @samp{$cwd} is not the same as @samp{.}---the former
7598 tracks the current working directory as it changes during your @value{GDBN}
7599 session, while the latter is immediately expanded to the current
7600 directory at the time you add an entry to the source path.
7603 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
7605 @c RET-repeat for @code{directory} is explicitly disabled, but since
7606 @c repeating it would be a no-op we do not say that. (thanks to RMS)
7608 @item set directories @var{path-list}
7609 @kindex set directories
7610 Set the source path to @var{path-list}.
7611 @samp{$cdir:$cwd} are added if missing.
7613 @item show directories
7614 @kindex show directories
7615 Print the source path: show which directories it contains.
7617 @anchor{set substitute-path}
7618 @item set substitute-path @var{from} @var{to}
7619 @kindex set substitute-path
7620 Define a source path substitution rule, and add it at the end of the
7621 current list of existing substitution rules. If a rule with the same
7622 @var{from} was already defined, then the old rule is also deleted.
7624 For example, if the file @file{/foo/bar/baz.c} was moved to
7625 @file{/mnt/cross/baz.c}, then the command
7628 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
7632 will tell @value{GDBN} to replace @samp{/usr/src} with
7633 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
7634 @file{baz.c} even though it was moved.
7636 In the case when more than one substitution rule have been defined,
7637 the rules are evaluated one by one in the order where they have been
7638 defined. The first one matching, if any, is selected to perform
7641 For instance, if we had entered the following commands:
7644 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
7645 (@value{GDBP}) set substitute-path /usr/src /mnt/src
7649 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
7650 @file{/mnt/include/defs.h} by using the first rule. However, it would
7651 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
7652 @file{/mnt/src/lib/foo.c}.
7655 @item unset substitute-path [path]
7656 @kindex unset substitute-path
7657 If a path is specified, search the current list of substitution rules
7658 for a rule that would rewrite that path. Delete that rule if found.
7659 A warning is emitted by the debugger if no rule could be found.
7661 If no path is specified, then all substitution rules are deleted.
7663 @item show substitute-path [path]
7664 @kindex show substitute-path
7665 If a path is specified, then print the source path substitution rule
7666 which would rewrite that path, if any.
7668 If no path is specified, then print all existing source path substitution
7673 If your source path is cluttered with directories that are no longer of
7674 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
7675 versions of source. You can correct the situation as follows:
7679 Use @code{directory} with no argument to reset the source path to its default value.
7682 Use @code{directory} with suitable arguments to reinstall the
7683 directories you want in the source path. You can add all the
7684 directories in one command.
7688 @section Source and Machine Code
7689 @cindex source line and its code address
7691 You can use the command @code{info line} to map source lines to program
7692 addresses (and vice versa), and the command @code{disassemble} to display
7693 a range of addresses as machine instructions. You can use the command
7694 @code{set disassemble-next-line} to set whether to disassemble next
7695 source line when execution stops. When run under @sc{gnu} Emacs
7696 mode, the @code{info line} command causes the arrow to point to the
7697 line specified. Also, @code{info line} prints addresses in symbolic form as
7702 @item info line @var{linespec}
7703 Print the starting and ending addresses of the compiled code for
7704 source line @var{linespec}. You can specify source lines in any of
7705 the ways documented in @ref{Specify Location}.
7708 For example, we can use @code{info line} to discover the location of
7709 the object code for the first line of function
7710 @code{m4_changequote}:
7712 @c FIXME: I think this example should also show the addresses in
7713 @c symbolic form, as they usually would be displayed.
7715 (@value{GDBP}) info line m4_changequote
7716 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
7720 @cindex code address and its source line
7721 We can also inquire (using @code{*@var{addr}} as the form for
7722 @var{linespec}) what source line covers a particular address:
7724 (@value{GDBP}) info line *0x63ff
7725 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
7728 @cindex @code{$_} and @code{info line}
7729 @cindex @code{x} command, default address
7730 @kindex x@r{(examine), and} info line
7731 After @code{info line}, the default address for the @code{x} command
7732 is changed to the starting address of the line, so that @samp{x/i} is
7733 sufficient to begin examining the machine code (@pxref{Memory,
7734 ,Examining Memory}). Also, this address is saved as the value of the
7735 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
7740 @cindex assembly instructions
7741 @cindex instructions, assembly
7742 @cindex machine instructions
7743 @cindex listing machine instructions
7745 @itemx disassemble /m
7746 @itemx disassemble /r
7747 This specialized command dumps a range of memory as machine
7748 instructions. It can also print mixed source+disassembly by specifying
7749 the @code{/m} modifier and print the raw instructions in hex as well as
7750 in symbolic form by specifying the @code{/r}.
7751 The default memory range is the function surrounding the
7752 program counter of the selected frame. A single argument to this
7753 command is a program counter value; @value{GDBN} dumps the function
7754 surrounding this value. When two arguments are given, they should
7755 be separated by a comma, possibly surrounded by whitespace. The
7756 arguments specify a range of addresses to dump, in one of two forms:
7759 @item @var{start},@var{end}
7760 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
7761 @item @var{start},+@var{length}
7762 the addresses from @var{start} (inclusive) to
7763 @code{@var{start}+@var{length}} (exclusive).
7767 When 2 arguments are specified, the name of the function is also
7768 printed (since there could be several functions in the given range).
7770 The argument(s) can be any expression yielding a numeric value, such as
7771 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
7773 If the range of memory being disassembled contains current program counter,
7774 the instruction at that location is shown with a @code{=>} marker.
7777 The following example shows the disassembly of a range of addresses of
7778 HP PA-RISC 2.0 code:
7781 (@value{GDBP}) disas 0x32c4, 0x32e4
7782 Dump of assembler code from 0x32c4 to 0x32e4:
7783 0x32c4 <main+204>: addil 0,dp
7784 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
7785 0x32cc <main+212>: ldil 0x3000,r31
7786 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
7787 0x32d4 <main+220>: ldo 0(r31),rp
7788 0x32d8 <main+224>: addil -0x800,dp
7789 0x32dc <main+228>: ldo 0x588(r1),r26
7790 0x32e0 <main+232>: ldil 0x3000,r31
7791 End of assembler dump.
7794 Here is an example showing mixed source+assembly for Intel x86, when the
7795 program is stopped just after function prologue:
7798 (@value{GDBP}) disas /m main
7799 Dump of assembler code for function main:
7801 0x08048330 <+0>: push %ebp
7802 0x08048331 <+1>: mov %esp,%ebp
7803 0x08048333 <+3>: sub $0x8,%esp
7804 0x08048336 <+6>: and $0xfffffff0,%esp
7805 0x08048339 <+9>: sub $0x10,%esp
7807 6 printf ("Hello.\n");
7808 => 0x0804833c <+12>: movl $0x8048440,(%esp)
7809 0x08048343 <+19>: call 0x8048284 <puts@@plt>
7813 0x08048348 <+24>: mov $0x0,%eax
7814 0x0804834d <+29>: leave
7815 0x0804834e <+30>: ret
7817 End of assembler dump.
7820 Here is another example showing raw instructions in hex for AMD x86-64,
7823 (gdb) disas /r 0x400281,+10
7824 Dump of assembler code from 0x400281 to 0x40028b:
7825 0x0000000000400281: 38 36 cmp %dh,(%rsi)
7826 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
7827 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
7828 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
7829 End of assembler dump.
7832 Addresses cannot be specified as a linespec (@pxref{Specify Location}).
7833 So, for example, if you want to disassemble function @code{bar}
7834 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
7835 and not @samp{disassemble foo.c:bar}.
7837 Some architectures have more than one commonly-used set of instruction
7838 mnemonics or other syntax.
7840 For programs that were dynamically linked and use shared libraries,
7841 instructions that call functions or branch to locations in the shared
7842 libraries might show a seemingly bogus location---it's actually a
7843 location of the relocation table. On some architectures, @value{GDBN}
7844 might be able to resolve these to actual function names.
7847 @kindex set disassembly-flavor
7848 @cindex Intel disassembly flavor
7849 @cindex AT&T disassembly flavor
7850 @item set disassembly-flavor @var{instruction-set}
7851 Select the instruction set to use when disassembling the
7852 program via the @code{disassemble} or @code{x/i} commands.
7854 Currently this command is only defined for the Intel x86 family. You
7855 can set @var{instruction-set} to either @code{intel} or @code{att}.
7856 The default is @code{att}, the AT&T flavor used by default by Unix
7857 assemblers for x86-based targets.
7859 @kindex show disassembly-flavor
7860 @item show disassembly-flavor
7861 Show the current setting of the disassembly flavor.
7865 @kindex set disassemble-next-line
7866 @kindex show disassemble-next-line
7867 @item set disassemble-next-line
7868 @itemx show disassemble-next-line
7869 Control whether or not @value{GDBN} will disassemble the next source
7870 line or instruction when execution stops. If ON, @value{GDBN} will
7871 display disassembly of the next source line when execution of the
7872 program being debugged stops. This is @emph{in addition} to
7873 displaying the source line itself, which @value{GDBN} always does if
7874 possible. If the next source line cannot be displayed for some reason
7875 (e.g., if @value{GDBN} cannot find the source file, or there's no line
7876 info in the debug info), @value{GDBN} will display disassembly of the
7877 next @emph{instruction} instead of showing the next source line. If
7878 AUTO, @value{GDBN} will display disassembly of next instruction only
7879 if the source line cannot be displayed. This setting causes
7880 @value{GDBN} to display some feedback when you step through a function
7881 with no line info or whose source file is unavailable. The default is
7882 OFF, which means never display the disassembly of the next line or
7888 @chapter Examining Data
7890 @cindex printing data
7891 @cindex examining data
7894 The usual way to examine data in your program is with the @code{print}
7895 command (abbreviated @code{p}), or its synonym @code{inspect}. It
7896 evaluates and prints the value of an expression of the language your
7897 program is written in (@pxref{Languages, ,Using @value{GDBN} with
7898 Different Languages}). It may also print the expression using a
7899 Python-based pretty-printer (@pxref{Pretty Printing}).
7902 @item print @var{expr}
7903 @itemx print /@var{f} @var{expr}
7904 @var{expr} is an expression (in the source language). By default the
7905 value of @var{expr} is printed in a format appropriate to its data type;
7906 you can choose a different format by specifying @samp{/@var{f}}, where
7907 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
7911 @itemx print /@var{f}
7912 @cindex reprint the last value
7913 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
7914 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
7915 conveniently inspect the same value in an alternative format.
7918 A more low-level way of examining data is with the @code{x} command.
7919 It examines data in memory at a specified address and prints it in a
7920 specified format. @xref{Memory, ,Examining Memory}.
7922 If you are interested in information about types, or about how the
7923 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
7924 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
7927 @cindex exploring hierarchical data structures
7929 Another way of examining values of expressions and type information is
7930 through the Python extension command @code{explore} (available only if
7931 the @value{GDBN} build is configured with @code{--with-python}). It
7932 offers an interactive way to start at the highest level (or, the most
7933 abstract level) of the data type of an expression (or, the data type
7934 itself) and explore all the way down to leaf scalar values/fields
7935 embedded in the higher level data types.
7938 @item explore @var{arg}
7939 @var{arg} is either an expression (in the source language), or a type
7940 visible in the current context of the program being debugged.
7943 The working of the @code{explore} command can be illustrated with an
7944 example. If a data type @code{struct ComplexStruct} is defined in your
7954 struct ComplexStruct
7956 struct SimpleStruct *ss_p;
7962 followed by variable declarations as
7965 struct SimpleStruct ss = @{ 10, 1.11 @};
7966 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
7970 then, the value of the variable @code{cs} can be explored using the
7971 @code{explore} command as follows.
7975 The value of `cs' is a struct/class of type `struct ComplexStruct' with
7976 the following fields:
7978 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
7979 arr = <Enter 1 to explore this field of type `int [10]'>
7981 Enter the field number of choice:
7985 Since the fields of @code{cs} are not scalar values, you are being
7986 prompted to chose the field you want to explore. Let's say you choose
7987 the field @code{ss_p} by entering @code{0}. Then, since this field is a
7988 pointer, you will be asked if it is pointing to a single value. From
7989 the declaration of @code{cs} above, it is indeed pointing to a single
7990 value, hence you enter @code{y}. If you enter @code{n}, then you will
7991 be asked if it were pointing to an array of values, in which case this
7992 field will be explored as if it were an array.
7995 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
7996 Continue exploring it as a pointer to a single value [y/n]: y
7997 The value of `*(cs.ss_p)' is a struct/class of type `struct
7998 SimpleStruct' with the following fields:
8000 i = 10 .. (Value of type `int')
8001 d = 1.1100000000000001 .. (Value of type `double')
8003 Press enter to return to parent value:
8007 If the field @code{arr} of @code{cs} was chosen for exploration by
8008 entering @code{1} earlier, then since it is as array, you will be
8009 prompted to enter the index of the element in the array that you want
8013 `cs.arr' is an array of `int'.
8014 Enter the index of the element you want to explore in `cs.arr': 5
8016 `(cs.arr)[5]' is a scalar value of type `int'.
8020 Press enter to return to parent value:
8023 In general, at any stage of exploration, you can go deeper towards the
8024 leaf values by responding to the prompts appropriately, or hit the
8025 return key to return to the enclosing data structure (the @i{higher}
8026 level data structure).
8028 Similar to exploring values, you can use the @code{explore} command to
8029 explore types. Instead of specifying a value (which is typically a
8030 variable name or an expression valid in the current context of the
8031 program being debugged), you specify a type name. If you consider the
8032 same example as above, your can explore the type
8033 @code{struct ComplexStruct} by passing the argument
8034 @code{struct ComplexStruct} to the @code{explore} command.
8037 (gdb) explore struct ComplexStruct
8041 By responding to the prompts appropriately in the subsequent interactive
8042 session, you can explore the type @code{struct ComplexStruct} in a
8043 manner similar to how the value @code{cs} was explored in the above
8046 The @code{explore} command also has two sub-commands,
8047 @code{explore value} and @code{explore type}. The former sub-command is
8048 a way to explicitly specify that value exploration of the argument is
8049 being invoked, while the latter is a way to explicitly specify that type
8050 exploration of the argument is being invoked.
8053 @item explore value @var{expr}
8054 @cindex explore value
8055 This sub-command of @code{explore} explores the value of the
8056 expression @var{expr} (if @var{expr} is an expression valid in the
8057 current context of the program being debugged). The behavior of this
8058 command is identical to that of the behavior of the @code{explore}
8059 command being passed the argument @var{expr}.
8061 @item explore type @var{arg}
8062 @cindex explore type
8063 This sub-command of @code{explore} explores the type of @var{arg} (if
8064 @var{arg} is a type visible in the current context of program being
8065 debugged), or the type of the value/expression @var{arg} (if @var{arg}
8066 is an expression valid in the current context of the program being
8067 debugged). If @var{arg} is a type, then the behavior of this command is
8068 identical to that of the @code{explore} command being passed the
8069 argument @var{arg}. If @var{arg} is an expression, then the behavior of
8070 this command will be identical to that of the @code{explore} command
8071 being passed the type of @var{arg} as the argument.
8075 * Expressions:: Expressions
8076 * Ambiguous Expressions:: Ambiguous Expressions
8077 * Variables:: Program variables
8078 * Arrays:: Artificial arrays
8079 * Output Formats:: Output formats
8080 * Memory:: Examining memory
8081 * Auto Display:: Automatic display
8082 * Print Settings:: Print settings
8083 * Pretty Printing:: Python pretty printing
8084 * Value History:: Value history
8085 * Convenience Vars:: Convenience variables
8086 * Convenience Funs:: Convenience functions
8087 * Registers:: Registers
8088 * Floating Point Hardware:: Floating point hardware
8089 * Vector Unit:: Vector Unit
8090 * OS Information:: Auxiliary data provided by operating system
8091 * Memory Region Attributes:: Memory region attributes
8092 * Dump/Restore Files:: Copy between memory and a file
8093 * Core File Generation:: Cause a program dump its core
8094 * Character Sets:: Debugging programs that use a different
8095 character set than GDB does
8096 * Caching Target Data:: Data caching for targets
8097 * Searching Memory:: Searching memory for a sequence of bytes
8101 @section Expressions
8104 @code{print} and many other @value{GDBN} commands accept an expression and
8105 compute its value. Any kind of constant, variable or operator defined
8106 by the programming language you are using is valid in an expression in
8107 @value{GDBN}. This includes conditional expressions, function calls,
8108 casts, and string constants. It also includes preprocessor macros, if
8109 you compiled your program to include this information; see
8112 @cindex arrays in expressions
8113 @value{GDBN} supports array constants in expressions input by
8114 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
8115 you can use the command @code{print @{1, 2, 3@}} to create an array
8116 of three integers. If you pass an array to a function or assign it
8117 to a program variable, @value{GDBN} copies the array to memory that
8118 is @code{malloc}ed in the target program.
8120 Because C is so widespread, most of the expressions shown in examples in
8121 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
8122 Languages}, for information on how to use expressions in other
8125 In this section, we discuss operators that you can use in @value{GDBN}
8126 expressions regardless of your programming language.
8128 @cindex casts, in expressions
8129 Casts are supported in all languages, not just in C, because it is so
8130 useful to cast a number into a pointer in order to examine a structure
8131 at that address in memory.
8132 @c FIXME: casts supported---Mod2 true?
8134 @value{GDBN} supports these operators, in addition to those common
8135 to programming languages:
8139 @samp{@@} is a binary operator for treating parts of memory as arrays.
8140 @xref{Arrays, ,Artificial Arrays}, for more information.
8143 @samp{::} allows you to specify a variable in terms of the file or
8144 function where it is defined. @xref{Variables, ,Program Variables}.
8146 @cindex @{@var{type}@}
8147 @cindex type casting memory
8148 @cindex memory, viewing as typed object
8149 @cindex casts, to view memory
8150 @item @{@var{type}@} @var{addr}
8151 Refers to an object of type @var{type} stored at address @var{addr} in
8152 memory. @var{addr} may be any expression whose value is an integer or
8153 pointer (but parentheses are required around binary operators, just as in
8154 a cast). This construct is allowed regardless of what kind of data is
8155 normally supposed to reside at @var{addr}.
8158 @node Ambiguous Expressions
8159 @section Ambiguous Expressions
8160 @cindex ambiguous expressions
8162 Expressions can sometimes contain some ambiguous elements. For instance,
8163 some programming languages (notably Ada, C@t{++} and Objective-C) permit
8164 a single function name to be defined several times, for application in
8165 different contexts. This is called @dfn{overloading}. Another example
8166 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
8167 templates and is typically instantiated several times, resulting in
8168 the same function name being defined in different contexts.
8170 In some cases and depending on the language, it is possible to adjust
8171 the expression to remove the ambiguity. For instance in C@t{++}, you
8172 can specify the signature of the function you want to break on, as in
8173 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
8174 qualified name of your function often makes the expression unambiguous
8177 When an ambiguity that needs to be resolved is detected, the debugger
8178 has the capability to display a menu of numbered choices for each
8179 possibility, and then waits for the selection with the prompt @samp{>}.
8180 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
8181 aborts the current command. If the command in which the expression was
8182 used allows more than one choice to be selected, the next option in the
8183 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
8186 For example, the following session excerpt shows an attempt to set a
8187 breakpoint at the overloaded symbol @code{String::after}.
8188 We choose three particular definitions of that function name:
8190 @c FIXME! This is likely to change to show arg type lists, at least
8193 (@value{GDBP}) b String::after
8196 [2] file:String.cc; line number:867
8197 [3] file:String.cc; line number:860
8198 [4] file:String.cc; line number:875
8199 [5] file:String.cc; line number:853
8200 [6] file:String.cc; line number:846
8201 [7] file:String.cc; line number:735
8203 Breakpoint 1 at 0xb26c: file String.cc, line 867.
8204 Breakpoint 2 at 0xb344: file String.cc, line 875.
8205 Breakpoint 3 at 0xafcc: file String.cc, line 846.
8206 Multiple breakpoints were set.
8207 Use the "delete" command to delete unwanted
8214 @kindex set multiple-symbols
8215 @item set multiple-symbols @var{mode}
8216 @cindex multiple-symbols menu
8218 This option allows you to adjust the debugger behavior when an expression
8221 By default, @var{mode} is set to @code{all}. If the command with which
8222 the expression is used allows more than one choice, then @value{GDBN}
8223 automatically selects all possible choices. For instance, inserting
8224 a breakpoint on a function using an ambiguous name results in a breakpoint
8225 inserted on each possible match. However, if a unique choice must be made,
8226 then @value{GDBN} uses the menu to help you disambiguate the expression.
8227 For instance, printing the address of an overloaded function will result
8228 in the use of the menu.
8230 When @var{mode} is set to @code{ask}, the debugger always uses the menu
8231 when an ambiguity is detected.
8233 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
8234 an error due to the ambiguity and the command is aborted.
8236 @kindex show multiple-symbols
8237 @item show multiple-symbols
8238 Show the current value of the @code{multiple-symbols} setting.
8242 @section Program Variables
8244 The most common kind of expression to use is the name of a variable
8247 Variables in expressions are understood in the selected stack frame
8248 (@pxref{Selection, ,Selecting a Frame}); they must be either:
8252 global (or file-static)
8259 visible according to the scope rules of the
8260 programming language from the point of execution in that frame
8263 @noindent This means that in the function
8278 you can examine and use the variable @code{a} whenever your program is
8279 executing within the function @code{foo}, but you can only use or
8280 examine the variable @code{b} while your program is executing inside
8281 the block where @code{b} is declared.
8283 @cindex variable name conflict
8284 There is an exception: you can refer to a variable or function whose
8285 scope is a single source file even if the current execution point is not
8286 in this file. But it is possible to have more than one such variable or
8287 function with the same name (in different source files). If that
8288 happens, referring to that name has unpredictable effects. If you wish,
8289 you can specify a static variable in a particular function or file by
8290 using the colon-colon (@code{::}) notation:
8292 @cindex colon-colon, context for variables/functions
8294 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
8295 @cindex @code{::}, context for variables/functions
8298 @var{file}::@var{variable}
8299 @var{function}::@var{variable}
8303 Here @var{file} or @var{function} is the name of the context for the
8304 static @var{variable}. In the case of file names, you can use quotes to
8305 make sure @value{GDBN} parses the file name as a single word---for example,
8306 to print a global value of @code{x} defined in @file{f2.c}:
8309 (@value{GDBP}) p 'f2.c'::x
8312 The @code{::} notation is normally used for referring to
8313 static variables, since you typically disambiguate uses of local variables
8314 in functions by selecting the appropriate frame and using the
8315 simple name of the variable. However, you may also use this notation
8316 to refer to local variables in frames enclosing the selected frame:
8325 process (a); /* Stop here */
8336 For example, if there is a breakpoint at the commented line,
8337 here is what you might see
8338 when the program stops after executing the call @code{bar(0)}:
8343 (@value{GDBP}) p bar::a
8346 #2 0x080483d0 in foo (a=5) at foobar.c:12
8349 (@value{GDBP}) p bar::a
8353 @cindex C@t{++} scope resolution
8354 These uses of @samp{::} are very rarely in conflict with the very
8355 similar use of the same notation in C@t{++}. When they are in
8356 conflict, the C@t{++} meaning takes precedence; however, this can be
8357 overridden by quoting the file or function name with single quotes.
8359 For example, suppose the program is stopped in a method of a class
8360 that has a field named @code{includefile}, and there is also an
8361 include file named @file{includefile} that defines a variable,
8365 (@value{GDBP}) p includefile
8367 (@value{GDBP}) p includefile::some_global
8368 A syntax error in expression, near `'.
8369 (@value{GDBP}) p 'includefile'::some_global
8373 @cindex wrong values
8374 @cindex variable values, wrong
8375 @cindex function entry/exit, wrong values of variables
8376 @cindex optimized code, wrong values of variables
8378 @emph{Warning:} Occasionally, a local variable may appear to have the
8379 wrong value at certain points in a function---just after entry to a new
8380 scope, and just before exit.
8382 You may see this problem when you are stepping by machine instructions.
8383 This is because, on most machines, it takes more than one instruction to
8384 set up a stack frame (including local variable definitions); if you are
8385 stepping by machine instructions, variables may appear to have the wrong
8386 values until the stack frame is completely built. On exit, it usually
8387 also takes more than one machine instruction to destroy a stack frame;
8388 after you begin stepping through that group of instructions, local
8389 variable definitions may be gone.
8391 This may also happen when the compiler does significant optimizations.
8392 To be sure of always seeing accurate values, turn off all optimization
8395 @cindex ``No symbol "foo" in current context''
8396 Another possible effect of compiler optimizations is to optimize
8397 unused variables out of existence, or assign variables to registers (as
8398 opposed to memory addresses). Depending on the support for such cases
8399 offered by the debug info format used by the compiler, @value{GDBN}
8400 might not be able to display values for such local variables. If that
8401 happens, @value{GDBN} will print a message like this:
8404 No symbol "foo" in current context.
8407 To solve such problems, either recompile without optimizations, or use a
8408 different debug info format, if the compiler supports several such
8409 formats. @xref{Compilation}, for more information on choosing compiler
8410 options. @xref{C, ,C and C@t{++}}, for more information about debug
8411 info formats that are best suited to C@t{++} programs.
8413 If you ask to print an object whose contents are unknown to
8414 @value{GDBN}, e.g., because its data type is not completely specified
8415 by the debug information, @value{GDBN} will say @samp{<incomplete
8416 type>}. @xref{Symbols, incomplete type}, for more about this.
8418 If you append @kbd{@@entry} string to a function parameter name you get its
8419 value at the time the function got called. If the value is not available an
8420 error message is printed. Entry values are available only with some compilers.
8421 Entry values are normally also printed at the function parameter list according
8422 to @ref{set print entry-values}.
8425 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
8431 (gdb) print i@@entry
8435 Strings are identified as arrays of @code{char} values without specified
8436 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
8437 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
8438 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
8439 defines literal string type @code{"char"} as @code{char} without a sign.
8444 signed char var1[] = "A";
8447 You get during debugging
8452 $2 = @{65 'A', 0 '\0'@}
8456 @section Artificial Arrays
8458 @cindex artificial array
8460 @kindex @@@r{, referencing memory as an array}
8461 It is often useful to print out several successive objects of the
8462 same type in memory; a section of an array, or an array of
8463 dynamically determined size for which only a pointer exists in the
8466 You can do this by referring to a contiguous span of memory as an
8467 @dfn{artificial array}, using the binary operator @samp{@@}. The left
8468 operand of @samp{@@} should be the first element of the desired array
8469 and be an individual object. The right operand should be the desired length
8470 of the array. The result is an array value whose elements are all of
8471 the type of the left argument. The first element is actually the left
8472 argument; the second element comes from bytes of memory immediately
8473 following those that hold the first element, and so on. Here is an
8474 example. If a program says
8477 int *array = (int *) malloc (len * sizeof (int));
8481 you can print the contents of @code{array} with
8487 The left operand of @samp{@@} must reside in memory. Array values made
8488 with @samp{@@} in this way behave just like other arrays in terms of
8489 subscripting, and are coerced to pointers when used in expressions.
8490 Artificial arrays most often appear in expressions via the value history
8491 (@pxref{Value History, ,Value History}), after printing one out.
8493 Another way to create an artificial array is to use a cast.
8494 This re-interprets a value as if it were an array.
8495 The value need not be in memory:
8497 (@value{GDBP}) p/x (short[2])0x12345678
8498 $1 = @{0x1234, 0x5678@}
8501 As a convenience, if you leave the array length out (as in
8502 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
8503 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
8505 (@value{GDBP}) p/x (short[])0x12345678
8506 $2 = @{0x1234, 0x5678@}
8509 Sometimes the artificial array mechanism is not quite enough; in
8510 moderately complex data structures, the elements of interest may not
8511 actually be adjacent---for example, if you are interested in the values
8512 of pointers in an array. One useful work-around in this situation is
8513 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
8514 Variables}) as a counter in an expression that prints the first
8515 interesting value, and then repeat that expression via @key{RET}. For
8516 instance, suppose you have an array @code{dtab} of pointers to
8517 structures, and you are interested in the values of a field @code{fv}
8518 in each structure. Here is an example of what you might type:
8528 @node Output Formats
8529 @section Output Formats
8531 @cindex formatted output
8532 @cindex output formats
8533 By default, @value{GDBN} prints a value according to its data type. Sometimes
8534 this is not what you want. For example, you might want to print a number
8535 in hex, or a pointer in decimal. Or you might want to view data in memory
8536 at a certain address as a character string or as an instruction. To do
8537 these things, specify an @dfn{output format} when you print a value.
8539 The simplest use of output formats is to say how to print a value
8540 already computed. This is done by starting the arguments of the
8541 @code{print} command with a slash and a format letter. The format
8542 letters supported are:
8546 Regard the bits of the value as an integer, and print the integer in
8550 Print as integer in signed decimal.
8553 Print as integer in unsigned decimal.
8556 Print as integer in octal.
8559 Print as integer in binary. The letter @samp{t} stands for ``two''.
8560 @footnote{@samp{b} cannot be used because these format letters are also
8561 used with the @code{x} command, where @samp{b} stands for ``byte'';
8562 see @ref{Memory,,Examining Memory}.}
8565 @cindex unknown address, locating
8566 @cindex locate address
8567 Print as an address, both absolute in hexadecimal and as an offset from
8568 the nearest preceding symbol. You can use this format used to discover
8569 where (in what function) an unknown address is located:
8572 (@value{GDBP}) p/a 0x54320
8573 $3 = 0x54320 <_initialize_vx+396>
8577 The command @code{info symbol 0x54320} yields similar results.
8578 @xref{Symbols, info symbol}.
8581 Regard as an integer and print it as a character constant. This
8582 prints both the numerical value and its character representation. The
8583 character representation is replaced with the octal escape @samp{\nnn}
8584 for characters outside the 7-bit @sc{ascii} range.
8586 Without this format, @value{GDBN} displays @code{char},
8587 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
8588 constants. Single-byte members of vectors are displayed as integer
8592 Regard the bits of the value as a floating point number and print
8593 using typical floating point syntax.
8596 @cindex printing strings
8597 @cindex printing byte arrays
8598 Regard as a string, if possible. With this format, pointers to single-byte
8599 data are displayed as null-terminated strings and arrays of single-byte data
8600 are displayed as fixed-length strings. Other values are displayed in their
8603 Without this format, @value{GDBN} displays pointers to and arrays of
8604 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
8605 strings. Single-byte members of a vector are displayed as an integer
8609 Like @samp{x} formatting, the value is treated as an integer and
8610 printed as hexadecimal, but leading zeros are printed to pad the value
8611 to the size of the integer type.
8614 @cindex raw printing
8615 Print using the @samp{raw} formatting. By default, @value{GDBN} will
8616 use a Python-based pretty-printer, if one is available (@pxref{Pretty
8617 Printing}). This typically results in a higher-level display of the
8618 value's contents. The @samp{r} format bypasses any Python
8619 pretty-printer which might exist.
8622 For example, to print the program counter in hex (@pxref{Registers}), type
8629 Note that no space is required before the slash; this is because command
8630 names in @value{GDBN} cannot contain a slash.
8632 To reprint the last value in the value history with a different format,
8633 you can use the @code{print} command with just a format and no
8634 expression. For example, @samp{p/x} reprints the last value in hex.
8637 @section Examining Memory
8639 You can use the command @code{x} (for ``examine'') to examine memory in
8640 any of several formats, independently of your program's data types.
8642 @cindex examining memory
8644 @kindex x @r{(examine memory)}
8645 @item x/@var{nfu} @var{addr}
8648 Use the @code{x} command to examine memory.
8651 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
8652 much memory to display and how to format it; @var{addr} is an
8653 expression giving the address where you want to start displaying memory.
8654 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
8655 Several commands set convenient defaults for @var{addr}.
8658 @item @var{n}, the repeat count
8659 The repeat count is a decimal integer; the default is 1. It specifies
8660 how much memory (counting by units @var{u}) to display.
8661 @c This really is **decimal**; unaffected by 'set radix' as of GDB
8664 @item @var{f}, the display format
8665 The display format is one of the formats used by @code{print}
8666 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
8667 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
8668 The default is @samp{x} (hexadecimal) initially. The default changes
8669 each time you use either @code{x} or @code{print}.
8671 @item @var{u}, the unit size
8672 The unit size is any of
8678 Halfwords (two bytes).
8680 Words (four bytes). This is the initial default.
8682 Giant words (eight bytes).
8685 Each time you specify a unit size with @code{x}, that size becomes the
8686 default unit the next time you use @code{x}. For the @samp{i} format,
8687 the unit size is ignored and is normally not written. For the @samp{s} format,
8688 the unit size defaults to @samp{b}, unless it is explicitly given.
8689 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
8690 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
8691 Note that the results depend on the programming language of the
8692 current compilation unit. If the language is C, the @samp{s}
8693 modifier will use the UTF-16 encoding while @samp{w} will use
8694 UTF-32. The encoding is set by the programming language and cannot
8697 @item @var{addr}, starting display address
8698 @var{addr} is the address where you want @value{GDBN} to begin displaying
8699 memory. The expression need not have a pointer value (though it may);
8700 it is always interpreted as an integer address of a byte of memory.
8701 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
8702 @var{addr} is usually just after the last address examined---but several
8703 other commands also set the default address: @code{info breakpoints} (to
8704 the address of the last breakpoint listed), @code{info line} (to the
8705 starting address of a line), and @code{print} (if you use it to display
8706 a value from memory).
8709 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
8710 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
8711 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
8712 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
8713 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
8715 Since the letters indicating unit sizes are all distinct from the
8716 letters specifying output formats, you do not have to remember whether
8717 unit size or format comes first; either order works. The output
8718 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
8719 (However, the count @var{n} must come first; @samp{wx4} does not work.)
8721 Even though the unit size @var{u} is ignored for the formats @samp{s}
8722 and @samp{i}, you might still want to use a count @var{n}; for example,
8723 @samp{3i} specifies that you want to see three machine instructions,
8724 including any operands. For convenience, especially when used with
8725 the @code{display} command, the @samp{i} format also prints branch delay
8726 slot instructions, if any, beyond the count specified, which immediately
8727 follow the last instruction that is within the count. The command
8728 @code{disassemble} gives an alternative way of inspecting machine
8729 instructions; see @ref{Machine Code,,Source and Machine Code}.
8731 All the defaults for the arguments to @code{x} are designed to make it
8732 easy to continue scanning memory with minimal specifications each time
8733 you use @code{x}. For example, after you have inspected three machine
8734 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
8735 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
8736 the repeat count @var{n} is used again; the other arguments default as
8737 for successive uses of @code{x}.
8739 When examining machine instructions, the instruction at current program
8740 counter is shown with a @code{=>} marker. For example:
8743 (@value{GDBP}) x/5i $pc-6
8744 0x804837f <main+11>: mov %esp,%ebp
8745 0x8048381 <main+13>: push %ecx
8746 0x8048382 <main+14>: sub $0x4,%esp
8747 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
8748 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
8751 @cindex @code{$_}, @code{$__}, and value history
8752 The addresses and contents printed by the @code{x} command are not saved
8753 in the value history because there is often too much of them and they
8754 would get in the way. Instead, @value{GDBN} makes these values available for
8755 subsequent use in expressions as values of the convenience variables
8756 @code{$_} and @code{$__}. After an @code{x} command, the last address
8757 examined is available for use in expressions in the convenience variable
8758 @code{$_}. The contents of that address, as examined, are available in
8759 the convenience variable @code{$__}.
8761 If the @code{x} command has a repeat count, the address and contents saved
8762 are from the last memory unit printed; this is not the same as the last
8763 address printed if several units were printed on the last line of output.
8765 @cindex remote memory comparison
8766 @cindex verify remote memory image
8767 When you are debugging a program running on a remote target machine
8768 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
8769 remote machine's memory against the executable file you downloaded to
8770 the target. The @code{compare-sections} command is provided for such
8774 @kindex compare-sections
8775 @item compare-sections @r{[}@var{section-name}@r{]}
8776 Compare the data of a loadable section @var{section-name} in the
8777 executable file of the program being debugged with the same section in
8778 the remote machine's memory, and report any mismatches. With no
8779 arguments, compares all loadable sections. This command's
8780 availability depends on the target's support for the @code{"qCRC"}
8785 @section Automatic Display
8786 @cindex automatic display
8787 @cindex display of expressions
8789 If you find that you want to print the value of an expression frequently
8790 (to see how it changes), you might want to add it to the @dfn{automatic
8791 display list} so that @value{GDBN} prints its value each time your program stops.
8792 Each expression added to the list is given a number to identify it;
8793 to remove an expression from the list, you specify that number.
8794 The automatic display looks like this:
8798 3: bar[5] = (struct hack *) 0x3804
8802 This display shows item numbers, expressions and their current values. As with
8803 displays you request manually using @code{x} or @code{print}, you can
8804 specify the output format you prefer; in fact, @code{display} decides
8805 whether to use @code{print} or @code{x} depending your format
8806 specification---it uses @code{x} if you specify either the @samp{i}
8807 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
8811 @item display @var{expr}
8812 Add the expression @var{expr} to the list of expressions to display
8813 each time your program stops. @xref{Expressions, ,Expressions}.
8815 @code{display} does not repeat if you press @key{RET} again after using it.
8817 @item display/@var{fmt} @var{expr}
8818 For @var{fmt} specifying only a display format and not a size or
8819 count, add the expression @var{expr} to the auto-display list but
8820 arrange to display it each time in the specified format @var{fmt}.
8821 @xref{Output Formats,,Output Formats}.
8823 @item display/@var{fmt} @var{addr}
8824 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
8825 number of units, add the expression @var{addr} as a memory address to
8826 be examined each time your program stops. Examining means in effect
8827 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
8830 For example, @samp{display/i $pc} can be helpful, to see the machine
8831 instruction about to be executed each time execution stops (@samp{$pc}
8832 is a common name for the program counter; @pxref{Registers, ,Registers}).
8835 @kindex delete display
8837 @item undisplay @var{dnums}@dots{}
8838 @itemx delete display @var{dnums}@dots{}
8839 Remove items from the list of expressions to display. Specify the
8840 numbers of the displays that you want affected with the command
8841 argument @var{dnums}. It can be a single display number, one of the
8842 numbers shown in the first field of the @samp{info display} display;
8843 or it could be a range of display numbers, as in @code{2-4}.
8845 @code{undisplay} does not repeat if you press @key{RET} after using it.
8846 (Otherwise you would just get the error @samp{No display number @dots{}}.)
8848 @kindex disable display
8849 @item disable display @var{dnums}@dots{}
8850 Disable the display of item numbers @var{dnums}. A disabled display
8851 item is not printed automatically, but is not forgotten. It may be
8852 enabled again later. Specify the numbers of the displays that you
8853 want affected with the command argument @var{dnums}. It can be a
8854 single display number, one of the numbers shown in the first field of
8855 the @samp{info display} display; or it could be a range of display
8856 numbers, as in @code{2-4}.
8858 @kindex enable display
8859 @item enable display @var{dnums}@dots{}
8860 Enable display of item numbers @var{dnums}. It becomes effective once
8861 again in auto display of its expression, until you specify otherwise.
8862 Specify the numbers of the displays that you want affected with the
8863 command argument @var{dnums}. It can be a single display number, one
8864 of the numbers shown in the first field of the @samp{info display}
8865 display; or it could be a range of display numbers, as in @code{2-4}.
8868 Display the current values of the expressions on the list, just as is
8869 done when your program stops.
8871 @kindex info display
8873 Print the list of expressions previously set up to display
8874 automatically, each one with its item number, but without showing the
8875 values. This includes disabled expressions, which are marked as such.
8876 It also includes expressions which would not be displayed right now
8877 because they refer to automatic variables not currently available.
8880 @cindex display disabled out of scope
8881 If a display expression refers to local variables, then it does not make
8882 sense outside the lexical context for which it was set up. Such an
8883 expression is disabled when execution enters a context where one of its
8884 variables is not defined. For example, if you give the command
8885 @code{display last_char} while inside a function with an argument
8886 @code{last_char}, @value{GDBN} displays this argument while your program
8887 continues to stop inside that function. When it stops elsewhere---where
8888 there is no variable @code{last_char}---the display is disabled
8889 automatically. The next time your program stops where @code{last_char}
8890 is meaningful, you can enable the display expression once again.
8892 @node Print Settings
8893 @section Print Settings
8895 @cindex format options
8896 @cindex print settings
8897 @value{GDBN} provides the following ways to control how arrays, structures,
8898 and symbols are printed.
8901 These settings are useful for debugging programs in any language:
8905 @item set print address
8906 @itemx set print address on
8907 @cindex print/don't print memory addresses
8908 @value{GDBN} prints memory addresses showing the location of stack
8909 traces, structure values, pointer values, breakpoints, and so forth,
8910 even when it also displays the contents of those addresses. The default
8911 is @code{on}. For example, this is what a stack frame display looks like with
8912 @code{set print address on}:
8917 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
8919 530 if (lquote != def_lquote)
8923 @item set print address off
8924 Do not print addresses when displaying their contents. For example,
8925 this is the same stack frame displayed with @code{set print address off}:
8929 (@value{GDBP}) set print addr off
8931 #0 set_quotes (lq="<<", rq=">>") at input.c:530
8932 530 if (lquote != def_lquote)
8936 You can use @samp{set print address off} to eliminate all machine
8937 dependent displays from the @value{GDBN} interface. For example, with
8938 @code{print address off}, you should get the same text for backtraces on
8939 all machines---whether or not they involve pointer arguments.
8942 @item show print address
8943 Show whether or not addresses are to be printed.
8946 When @value{GDBN} prints a symbolic address, it normally prints the
8947 closest earlier symbol plus an offset. If that symbol does not uniquely
8948 identify the address (for example, it is a name whose scope is a single
8949 source file), you may need to clarify. One way to do this is with
8950 @code{info line}, for example @samp{info line *0x4537}. Alternately,
8951 you can set @value{GDBN} to print the source file and line number when
8952 it prints a symbolic address:
8955 @item set print symbol-filename on
8956 @cindex source file and line of a symbol
8957 @cindex symbol, source file and line
8958 Tell @value{GDBN} to print the source file name and line number of a
8959 symbol in the symbolic form of an address.
8961 @item set print symbol-filename off
8962 Do not print source file name and line number of a symbol. This is the
8965 @item show print symbol-filename
8966 Show whether or not @value{GDBN} will print the source file name and
8967 line number of a symbol in the symbolic form of an address.
8970 Another situation where it is helpful to show symbol filenames and line
8971 numbers is when disassembling code; @value{GDBN} shows you the line
8972 number and source file that corresponds to each instruction.
8974 Also, you may wish to see the symbolic form only if the address being
8975 printed is reasonably close to the closest earlier symbol:
8978 @item set print max-symbolic-offset @var{max-offset}
8979 @itemx set print max-symbolic-offset unlimited
8980 @cindex maximum value for offset of closest symbol
8981 Tell @value{GDBN} to only display the symbolic form of an address if the
8982 offset between the closest earlier symbol and the address is less than
8983 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
8984 to always print the symbolic form of an address if any symbol precedes
8985 it. Zero is equivalent to @code{unlimited}.
8987 @item show print max-symbolic-offset
8988 Ask how large the maximum offset is that @value{GDBN} prints in a
8992 @cindex wild pointer, interpreting
8993 @cindex pointer, finding referent
8994 If you have a pointer and you are not sure where it points, try
8995 @samp{set print symbol-filename on}. Then you can determine the name
8996 and source file location of the variable where it points, using
8997 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
8998 For example, here @value{GDBN} shows that a variable @code{ptt} points
8999 at another variable @code{t}, defined in @file{hi2.c}:
9002 (@value{GDBP}) set print symbol-filename on
9003 (@value{GDBP}) p/a ptt
9004 $4 = 0xe008 <t in hi2.c>
9008 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
9009 does not show the symbol name and filename of the referent, even with
9010 the appropriate @code{set print} options turned on.
9013 You can also enable @samp{/a}-like formatting all the time using
9014 @samp{set print symbol on}:
9017 @item set print symbol on
9018 Tell @value{GDBN} to print the symbol corresponding to an address, if
9021 @item set print symbol off
9022 Tell @value{GDBN} not to print the symbol corresponding to an
9023 address. In this mode, @value{GDBN} will still print the symbol
9024 corresponding to pointers to functions. This is the default.
9026 @item show print symbol
9027 Show whether @value{GDBN} will display the symbol corresponding to an
9031 Other settings control how different kinds of objects are printed:
9034 @item set print array
9035 @itemx set print array on
9036 @cindex pretty print arrays
9037 Pretty print arrays. This format is more convenient to read,
9038 but uses more space. The default is off.
9040 @item set print array off
9041 Return to compressed format for arrays.
9043 @item show print array
9044 Show whether compressed or pretty format is selected for displaying
9047 @cindex print array indexes
9048 @item set print array-indexes
9049 @itemx set print array-indexes on
9050 Print the index of each element when displaying arrays. May be more
9051 convenient to locate a given element in the array or quickly find the
9052 index of a given element in that printed array. The default is off.
9054 @item set print array-indexes off
9055 Stop printing element indexes when displaying arrays.
9057 @item show print array-indexes
9058 Show whether the index of each element is printed when displaying
9061 @item set print elements @var{number-of-elements}
9062 @itemx set print elements unlimited
9063 @cindex number of array elements to print
9064 @cindex limit on number of printed array elements
9065 Set a limit on how many elements of an array @value{GDBN} will print.
9066 If @value{GDBN} is printing a large array, it stops printing after it has
9067 printed the number of elements set by the @code{set print elements} command.
9068 This limit also applies to the display of strings.
9069 When @value{GDBN} starts, this limit is set to 200.
9070 Setting @var{number-of-elements} to @code{unlimited} or zero means
9071 that the number of elements to print is unlimited.
9073 @item show print elements
9074 Display the number of elements of a large array that @value{GDBN} will print.
9075 If the number is 0, then the printing is unlimited.
9077 @item set print frame-arguments @var{value}
9078 @kindex set print frame-arguments
9079 @cindex printing frame argument values
9080 @cindex print all frame argument values
9081 @cindex print frame argument values for scalars only
9082 @cindex do not print frame argument values
9083 This command allows to control how the values of arguments are printed
9084 when the debugger prints a frame (@pxref{Frames}). The possible
9089 The values of all arguments are printed.
9092 Print the value of an argument only if it is a scalar. The value of more
9093 complex arguments such as arrays, structures, unions, etc, is replaced
9094 by @code{@dots{}}. This is the default. Here is an example where
9095 only scalar arguments are shown:
9098 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
9103 None of the argument values are printed. Instead, the value of each argument
9104 is replaced by @code{@dots{}}. In this case, the example above now becomes:
9107 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
9112 By default, only scalar arguments are printed. This command can be used
9113 to configure the debugger to print the value of all arguments, regardless
9114 of their type. However, it is often advantageous to not print the value
9115 of more complex parameters. For instance, it reduces the amount of
9116 information printed in each frame, making the backtrace more readable.
9117 Also, it improves performance when displaying Ada frames, because
9118 the computation of large arguments can sometimes be CPU-intensive,
9119 especially in large applications. Setting @code{print frame-arguments}
9120 to @code{scalars} (the default) or @code{none} avoids this computation,
9121 thus speeding up the display of each Ada frame.
9123 @item show print frame-arguments
9124 Show how the value of arguments should be displayed when printing a frame.
9126 @item set print raw frame-arguments on
9127 Print frame arguments in raw, non pretty-printed, form.
9129 @item set print raw frame-arguments off
9130 Print frame arguments in pretty-printed form, if there is a pretty-printer
9131 for the value (@pxref{Pretty Printing}),
9132 otherwise print the value in raw form.
9133 This is the default.
9135 @item show print raw frame-arguments
9136 Show whether to print frame arguments in raw form.
9138 @anchor{set print entry-values}
9139 @item set print entry-values @var{value}
9140 @kindex set print entry-values
9141 Set printing of frame argument values at function entry. In some cases
9142 @value{GDBN} can determine the value of function argument which was passed by
9143 the function caller, even if the value was modified inside the called function
9144 and therefore is different. With optimized code, the current value could be
9145 unavailable, but the entry value may still be known.
9147 The default value is @code{default} (see below for its description). Older
9148 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
9149 this feature will behave in the @code{default} setting the same way as with the
9152 This functionality is currently supported only by DWARF 2 debugging format and
9153 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9154 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9157 The @var{value} parameter can be one of the following:
9161 Print only actual parameter values, never print values from function entry
9165 #0 different (val=6)
9166 #0 lost (val=<optimized out>)
9168 #0 invalid (val=<optimized out>)
9172 Print only parameter values from function entry point. The actual parameter
9173 values are never printed.
9175 #0 equal (val@@entry=5)
9176 #0 different (val@@entry=5)
9177 #0 lost (val@@entry=5)
9178 #0 born (val@@entry=<optimized out>)
9179 #0 invalid (val@@entry=<optimized out>)
9183 Print only parameter values from function entry point. If value from function
9184 entry point is not known while the actual value is known, print the actual
9185 value for such parameter.
9187 #0 equal (val@@entry=5)
9188 #0 different (val@@entry=5)
9189 #0 lost (val@@entry=5)
9191 #0 invalid (val@@entry=<optimized out>)
9195 Print actual parameter values. If actual parameter value is not known while
9196 value from function entry point is known, print the entry point value for such
9200 #0 different (val=6)
9201 #0 lost (val@@entry=5)
9203 #0 invalid (val=<optimized out>)
9207 Always print both the actual parameter value and its value from function entry
9208 point, even if values of one or both are not available due to compiler
9211 #0 equal (val=5, val@@entry=5)
9212 #0 different (val=6, val@@entry=5)
9213 #0 lost (val=<optimized out>, val@@entry=5)
9214 #0 born (val=10, val@@entry=<optimized out>)
9215 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
9219 Print the actual parameter value if it is known and also its value from
9220 function entry point if it is known. If neither is known, print for the actual
9221 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
9222 values are known and identical, print the shortened
9223 @code{param=param@@entry=VALUE} notation.
9225 #0 equal (val=val@@entry=5)
9226 #0 different (val=6, val@@entry=5)
9227 #0 lost (val@@entry=5)
9229 #0 invalid (val=<optimized out>)
9233 Always print the actual parameter value. Print also its value from function
9234 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
9235 if both values are known and identical, print the shortened
9236 @code{param=param@@entry=VALUE} notation.
9238 #0 equal (val=val@@entry=5)
9239 #0 different (val=6, val@@entry=5)
9240 #0 lost (val=<optimized out>, val@@entry=5)
9242 #0 invalid (val=<optimized out>)
9246 For analysis messages on possible failures of frame argument values at function
9247 entry resolution see @ref{set debug entry-values}.
9249 @item show print entry-values
9250 Show the method being used for printing of frame argument values at function
9253 @item set print repeats @var{number-of-repeats}
9254 @itemx set print repeats unlimited
9255 @cindex repeated array elements
9256 Set the threshold for suppressing display of repeated array
9257 elements. When the number of consecutive identical elements of an
9258 array exceeds the threshold, @value{GDBN} prints the string
9259 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
9260 identical repetitions, instead of displaying the identical elements
9261 themselves. Setting the threshold to @code{unlimited} or zero will
9262 cause all elements to be individually printed. The default threshold
9265 @item show print repeats
9266 Display the current threshold for printing repeated identical
9269 @item set print null-stop
9270 @cindex @sc{null} elements in arrays
9271 Cause @value{GDBN} to stop printing the characters of an array when the first
9272 @sc{null} is encountered. This is useful when large arrays actually
9273 contain only short strings.
9276 @item show print null-stop
9277 Show whether @value{GDBN} stops printing an array on the first
9278 @sc{null} character.
9280 @item set print pretty on
9281 @cindex print structures in indented form
9282 @cindex indentation in structure display
9283 Cause @value{GDBN} to print structures in an indented format with one member
9284 per line, like this:
9299 @item set print pretty off
9300 Cause @value{GDBN} to print structures in a compact format, like this:
9304 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
9305 meat = 0x54 "Pork"@}
9310 This is the default format.
9312 @item show print pretty
9313 Show which format @value{GDBN} is using to print structures.
9315 @item set print sevenbit-strings on
9316 @cindex eight-bit characters in strings
9317 @cindex octal escapes in strings
9318 Print using only seven-bit characters; if this option is set,
9319 @value{GDBN} displays any eight-bit characters (in strings or
9320 character values) using the notation @code{\}@var{nnn}. This setting is
9321 best if you are working in English (@sc{ascii}) and you use the
9322 high-order bit of characters as a marker or ``meta'' bit.
9324 @item set print sevenbit-strings off
9325 Print full eight-bit characters. This allows the use of more
9326 international character sets, and is the default.
9328 @item show print sevenbit-strings
9329 Show whether or not @value{GDBN} is printing only seven-bit characters.
9331 @item set print union on
9332 @cindex unions in structures, printing
9333 Tell @value{GDBN} to print unions which are contained in structures
9334 and other unions. This is the default setting.
9336 @item set print union off
9337 Tell @value{GDBN} not to print unions which are contained in
9338 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
9341 @item show print union
9342 Ask @value{GDBN} whether or not it will print unions which are contained in
9343 structures and other unions.
9345 For example, given the declarations
9348 typedef enum @{Tree, Bug@} Species;
9349 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
9350 typedef enum @{Caterpillar, Cocoon, Butterfly@}
9361 struct thing foo = @{Tree, @{Acorn@}@};
9365 with @code{set print union on} in effect @samp{p foo} would print
9368 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
9372 and with @code{set print union off} in effect it would print
9375 $1 = @{it = Tree, form = @{...@}@}
9379 @code{set print union} affects programs written in C-like languages
9385 These settings are of interest when debugging C@t{++} programs:
9388 @cindex demangling C@t{++} names
9389 @item set print demangle
9390 @itemx set print demangle on
9391 Print C@t{++} names in their source form rather than in the encoded
9392 (``mangled'') form passed to the assembler and linker for type-safe
9393 linkage. The default is on.
9395 @item show print demangle
9396 Show whether C@t{++} names are printed in mangled or demangled form.
9398 @item set print asm-demangle
9399 @itemx set print asm-demangle on
9400 Print C@t{++} names in their source form rather than their mangled form, even
9401 in assembler code printouts such as instruction disassemblies.
9404 @item show print asm-demangle
9405 Show whether C@t{++} names in assembly listings are printed in mangled
9408 @cindex C@t{++} symbol decoding style
9409 @cindex symbol decoding style, C@t{++}
9410 @kindex set demangle-style
9411 @item set demangle-style @var{style}
9412 Choose among several encoding schemes used by different compilers to
9413 represent C@t{++} names. The choices for @var{style} are currently:
9417 Allow @value{GDBN} to choose a decoding style by inspecting your program.
9418 This is the default.
9421 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
9424 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
9427 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
9430 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
9431 @strong{Warning:} this setting alone is not sufficient to allow
9432 debugging @code{cfront}-generated executables. @value{GDBN} would
9433 require further enhancement to permit that.
9436 If you omit @var{style}, you will see a list of possible formats.
9438 @item show demangle-style
9439 Display the encoding style currently in use for decoding C@t{++} symbols.
9441 @item set print object
9442 @itemx set print object on
9443 @cindex derived type of an object, printing
9444 @cindex display derived types
9445 When displaying a pointer to an object, identify the @emph{actual}
9446 (derived) type of the object rather than the @emph{declared} type, using
9447 the virtual function table. Note that the virtual function table is
9448 required---this feature can only work for objects that have run-time
9449 type identification; a single virtual method in the object's declared
9450 type is sufficient. Note that this setting is also taken into account when
9451 working with variable objects via MI (@pxref{GDB/MI}).
9453 @item set print object off
9454 Display only the declared type of objects, without reference to the
9455 virtual function table. This is the default setting.
9457 @item show print object
9458 Show whether actual, or declared, object types are displayed.
9460 @item set print static-members
9461 @itemx set print static-members on
9462 @cindex static members of C@t{++} objects
9463 Print static members when displaying a C@t{++} object. The default is on.
9465 @item set print static-members off
9466 Do not print static members when displaying a C@t{++} object.
9468 @item show print static-members
9469 Show whether C@t{++} static members are printed or not.
9471 @item set print pascal_static-members
9472 @itemx set print pascal_static-members on
9473 @cindex static members of Pascal objects
9474 @cindex Pascal objects, static members display
9475 Print static members when displaying a Pascal object. The default is on.
9477 @item set print pascal_static-members off
9478 Do not print static members when displaying a Pascal object.
9480 @item show print pascal_static-members
9481 Show whether Pascal static members are printed or not.
9483 @c These don't work with HP ANSI C++ yet.
9484 @item set print vtbl
9485 @itemx set print vtbl on
9486 @cindex pretty print C@t{++} virtual function tables
9487 @cindex virtual functions (C@t{++}) display
9488 @cindex VTBL display
9489 Pretty print C@t{++} virtual function tables. The default is off.
9490 (The @code{vtbl} commands do not work on programs compiled with the HP
9491 ANSI C@t{++} compiler (@code{aCC}).)
9493 @item set print vtbl off
9494 Do not pretty print C@t{++} virtual function tables.
9496 @item show print vtbl
9497 Show whether C@t{++} virtual function tables are pretty printed, or not.
9500 @node Pretty Printing
9501 @section Pretty Printing
9503 @value{GDBN} provides a mechanism to allow pretty-printing of values using
9504 Python code. It greatly simplifies the display of complex objects. This
9505 mechanism works for both MI and the CLI.
9508 * Pretty-Printer Introduction:: Introduction to pretty-printers
9509 * Pretty-Printer Example:: An example pretty-printer
9510 * Pretty-Printer Commands:: Pretty-printer commands
9513 @node Pretty-Printer Introduction
9514 @subsection Pretty-Printer Introduction
9516 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
9517 registered for the value. If there is then @value{GDBN} invokes the
9518 pretty-printer to print the value. Otherwise the value is printed normally.
9520 Pretty-printers are normally named. This makes them easy to manage.
9521 The @samp{info pretty-printer} command will list all the installed
9522 pretty-printers with their names.
9523 If a pretty-printer can handle multiple data types, then its
9524 @dfn{subprinters} are the printers for the individual data types.
9525 Each such subprinter has its own name.
9526 The format of the name is @var{printer-name};@var{subprinter-name}.
9528 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
9529 Typically they are automatically loaded and registered when the corresponding
9530 debug information is loaded, thus making them available without having to
9531 do anything special.
9533 There are three places where a pretty-printer can be registered.
9537 Pretty-printers registered globally are available when debugging
9541 Pretty-printers registered with a program space are available only
9542 when debugging that program.
9543 @xref{Progspaces In Python}, for more details on program spaces in Python.
9546 Pretty-printers registered with an objfile are loaded and unloaded
9547 with the corresponding objfile (e.g., shared library).
9548 @xref{Objfiles In Python}, for more details on objfiles in Python.
9551 @xref{Selecting Pretty-Printers}, for further information on how
9552 pretty-printers are selected,
9554 @xref{Writing a Pretty-Printer}, for implementing pretty printers
9557 @node Pretty-Printer Example
9558 @subsection Pretty-Printer Example
9560 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
9563 (@value{GDBP}) print s
9565 static npos = 4294967295,
9567 <std::allocator<char>> = @{
9568 <__gnu_cxx::new_allocator<char>> = @{
9569 <No data fields>@}, <No data fields>
9571 members of std::basic_string<char, std::char_traits<char>,
9572 std::allocator<char> >::_Alloc_hider:
9573 _M_p = 0x804a014 "abcd"
9578 With a pretty-printer for @code{std::string} only the contents are printed:
9581 (@value{GDBP}) print s
9585 @node Pretty-Printer Commands
9586 @subsection Pretty-Printer Commands
9587 @cindex pretty-printer commands
9590 @kindex info pretty-printer
9591 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9592 Print the list of installed pretty-printers.
9593 This includes disabled pretty-printers, which are marked as such.
9595 @var{object-regexp} is a regular expression matching the objects
9596 whose pretty-printers to list.
9597 Objects can be @code{global}, the program space's file
9598 (@pxref{Progspaces In Python}),
9599 and the object files within that program space (@pxref{Objfiles In Python}).
9600 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
9601 looks up a printer from these three objects.
9603 @var{name-regexp} is a regular expression matching the name of the printers
9606 @kindex disable pretty-printer
9607 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9608 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9609 A disabled pretty-printer is not forgotten, it may be enabled again later.
9611 @kindex enable pretty-printer
9612 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9613 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9618 Suppose we have three pretty-printers installed: one from library1.so
9619 named @code{foo} that prints objects of type @code{foo}, and
9620 another from library2.so named @code{bar} that prints two types of objects,
9621 @code{bar1} and @code{bar2}.
9624 (gdb) info pretty-printer
9631 (gdb) info pretty-printer library2
9636 (gdb) disable pretty-printer library1
9638 2 of 3 printers enabled
9639 (gdb) info pretty-printer
9646 (gdb) disable pretty-printer library2 bar:bar1
9648 1 of 3 printers enabled
9649 (gdb) info pretty-printer library2
9656 (gdb) disable pretty-printer library2 bar
9658 0 of 3 printers enabled
9659 (gdb) info pretty-printer library2
9668 Note that for @code{bar} the entire printer can be disabled,
9669 as can each individual subprinter.
9672 @section Value History
9674 @cindex value history
9675 @cindex history of values printed by @value{GDBN}
9676 Values printed by the @code{print} command are saved in the @value{GDBN}
9677 @dfn{value history}. This allows you to refer to them in other expressions.
9678 Values are kept until the symbol table is re-read or discarded
9679 (for example with the @code{file} or @code{symbol-file} commands).
9680 When the symbol table changes, the value history is discarded,
9681 since the values may contain pointers back to the types defined in the
9686 @cindex history number
9687 The values printed are given @dfn{history numbers} by which you can
9688 refer to them. These are successive integers starting with one.
9689 @code{print} shows you the history number assigned to a value by
9690 printing @samp{$@var{num} = } before the value; here @var{num} is the
9693 To refer to any previous value, use @samp{$} followed by the value's
9694 history number. The way @code{print} labels its output is designed to
9695 remind you of this. Just @code{$} refers to the most recent value in
9696 the history, and @code{$$} refers to the value before that.
9697 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
9698 is the value just prior to @code{$$}, @code{$$1} is equivalent to
9699 @code{$$}, and @code{$$0} is equivalent to @code{$}.
9701 For example, suppose you have just printed a pointer to a structure and
9702 want to see the contents of the structure. It suffices to type
9708 If you have a chain of structures where the component @code{next} points
9709 to the next one, you can print the contents of the next one with this:
9716 You can print successive links in the chain by repeating this
9717 command---which you can do by just typing @key{RET}.
9719 Note that the history records values, not expressions. If the value of
9720 @code{x} is 4 and you type these commands:
9728 then the value recorded in the value history by the @code{print} command
9729 remains 4 even though the value of @code{x} has changed.
9734 Print the last ten values in the value history, with their item numbers.
9735 This is like @samp{p@ $$9} repeated ten times, except that @code{show
9736 values} does not change the history.
9738 @item show values @var{n}
9739 Print ten history values centered on history item number @var{n}.
9742 Print ten history values just after the values last printed. If no more
9743 values are available, @code{show values +} produces no display.
9746 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
9747 same effect as @samp{show values +}.
9749 @node Convenience Vars
9750 @section Convenience Variables
9752 @cindex convenience variables
9753 @cindex user-defined variables
9754 @value{GDBN} provides @dfn{convenience variables} that you can use within
9755 @value{GDBN} to hold on to a value and refer to it later. These variables
9756 exist entirely within @value{GDBN}; they are not part of your program, and
9757 setting a convenience variable has no direct effect on further execution
9758 of your program. That is why you can use them freely.
9760 Convenience variables are prefixed with @samp{$}. Any name preceded by
9761 @samp{$} can be used for a convenience variable, unless it is one of
9762 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
9763 (Value history references, in contrast, are @emph{numbers} preceded
9764 by @samp{$}. @xref{Value History, ,Value History}.)
9766 You can save a value in a convenience variable with an assignment
9767 expression, just as you would set a variable in your program.
9771 set $foo = *object_ptr
9775 would save in @code{$foo} the value contained in the object pointed to by
9778 Using a convenience variable for the first time creates it, but its
9779 value is @code{void} until you assign a new value. You can alter the
9780 value with another assignment at any time.
9782 Convenience variables have no fixed types. You can assign a convenience
9783 variable any type of value, including structures and arrays, even if
9784 that variable already has a value of a different type. The convenience
9785 variable, when used as an expression, has the type of its current value.
9788 @kindex show convenience
9789 @cindex show all user variables and functions
9790 @item show convenience
9791 Print a list of convenience variables used so far, and their values,
9792 as well as a list of the convenience functions.
9793 Abbreviated @code{show conv}.
9795 @kindex init-if-undefined
9796 @cindex convenience variables, initializing
9797 @item init-if-undefined $@var{variable} = @var{expression}
9798 Set a convenience variable if it has not already been set. This is useful
9799 for user-defined commands that keep some state. It is similar, in concept,
9800 to using local static variables with initializers in C (except that
9801 convenience variables are global). It can also be used to allow users to
9802 override default values used in a command script.
9804 If the variable is already defined then the expression is not evaluated so
9805 any side-effects do not occur.
9808 One of the ways to use a convenience variable is as a counter to be
9809 incremented or a pointer to be advanced. For example, to print
9810 a field from successive elements of an array of structures:
9814 print bar[$i++]->contents
9818 Repeat that command by typing @key{RET}.
9820 Some convenience variables are created automatically by @value{GDBN} and given
9821 values likely to be useful.
9824 @vindex $_@r{, convenience variable}
9826 The variable @code{$_} is automatically set by the @code{x} command to
9827 the last address examined (@pxref{Memory, ,Examining Memory}). Other
9828 commands which provide a default address for @code{x} to examine also
9829 set @code{$_} to that address; these commands include @code{info line}
9830 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
9831 except when set by the @code{x} command, in which case it is a pointer
9832 to the type of @code{$__}.
9834 @vindex $__@r{, convenience variable}
9836 The variable @code{$__} is automatically set by the @code{x} command
9837 to the value found in the last address examined. Its type is chosen
9838 to match the format in which the data was printed.
9841 @vindex $_exitcode@r{, convenience variable}
9842 When the program being debugged terminates normally, @value{GDBN}
9843 automatically sets this variable to the exit code of the program, and
9844 resets @code{$_exitsignal} to @code{void}.
9847 @vindex $_exitsignal@r{, convenience variable}
9848 When the program being debugged dies due to an uncaught signal,
9849 @value{GDBN} automatically sets this variable to that signal's number,
9850 and resets @code{$_exitcode} to @code{void}.
9852 To distinguish between whether the program being debugged has exited
9853 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
9854 @code{$_exitsignal} is not @code{void}), the convenience function
9855 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
9856 Functions}). For example, considering the following source code:
9862 main (int argc, char *argv[])
9869 A valid way of telling whether the program being debugged has exited
9870 or signalled would be:
9873 (@value{GDBP}) define has_exited_or_signalled
9874 Type commands for definition of ``has_exited_or_signalled''.
9875 End with a line saying just ``end''.
9876 >if $_isvoid ($_exitsignal)
9877 >echo The program has exited\n
9879 >echo The program has signalled\n
9885 Program terminated with signal SIGALRM, Alarm clock.
9886 The program no longer exists.
9887 (@value{GDBP}) has_exited_or_signalled
9888 The program has signalled
9891 As can be seen, @value{GDBN} correctly informs that the program being
9892 debugged has signalled, since it calls @code{raise} and raises a
9893 @code{SIGALRM} signal. If the program being debugged had not called
9894 @code{raise}, then @value{GDBN} would report a normal exit:
9897 (@value{GDBP}) has_exited_or_signalled
9898 The program has exited
9902 The variable @code{$_exception} is set to the exception object being
9903 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
9906 @itemx $_probe_arg0@dots{}$_probe_arg11
9907 Arguments to a static probe. @xref{Static Probe Points}.
9910 @vindex $_sdata@r{, inspect, convenience variable}
9911 The variable @code{$_sdata} contains extra collected static tracepoint
9912 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
9913 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
9914 if extra static tracepoint data has not been collected.
9917 @vindex $_siginfo@r{, convenience variable}
9918 The variable @code{$_siginfo} contains extra signal information
9919 (@pxref{extra signal information}). Note that @code{$_siginfo}
9920 could be empty, if the application has not yet received any signals.
9921 For example, it will be empty before you execute the @code{run} command.
9924 @vindex $_tlb@r{, convenience variable}
9925 The variable @code{$_tlb} is automatically set when debugging
9926 applications running on MS-Windows in native mode or connected to
9927 gdbserver that supports the @code{qGetTIBAddr} request.
9928 @xref{General Query Packets}.
9929 This variable contains the address of the thread information block.
9933 On HP-UX systems, if you refer to a function or variable name that
9934 begins with a dollar sign, @value{GDBN} searches for a user or system
9935 name first, before it searches for a convenience variable.
9937 @node Convenience Funs
9938 @section Convenience Functions
9940 @cindex convenience functions
9941 @value{GDBN} also supplies some @dfn{convenience functions}. These
9942 have a syntax similar to convenience variables. A convenience
9943 function can be used in an expression just like an ordinary function;
9944 however, a convenience function is implemented internally to
9947 These functions do not require @value{GDBN} to be configured with
9948 @code{Python} support, which means that they are always available.
9952 @item $_isvoid (@var{expr})
9953 @findex $_isvoid@r{, convenience function}
9954 Return one if the expression @var{expr} is @code{void}. Otherwise it
9957 A @code{void} expression is an expression where the type of the result
9958 is @code{void}. For example, you can examine a convenience variable
9959 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
9963 (@value{GDBP}) print $_exitcode
9965 (@value{GDBP}) print $_isvoid ($_exitcode)
9968 Starting program: ./a.out
9969 [Inferior 1 (process 29572) exited normally]
9970 (@value{GDBP}) print $_exitcode
9972 (@value{GDBP}) print $_isvoid ($_exitcode)
9976 In the example above, we used @code{$_isvoid} to check whether
9977 @code{$_exitcode} is @code{void} before and after the execution of the
9978 program being debugged. Before the execution there is no exit code to
9979 be examined, therefore @code{$_exitcode} is @code{void}. After the
9980 execution the program being debugged returned zero, therefore
9981 @code{$_exitcode} is zero, which means that it is not @code{void}
9984 The @code{void} expression can also be a call of a function from the
9985 program being debugged. For example, given the following function:
9994 The result of calling it inside @value{GDBN} is @code{void}:
9997 (@value{GDBP}) print foo ()
9999 (@value{GDBP}) print $_isvoid (foo ())
10001 (@value{GDBP}) set $v = foo ()
10002 (@value{GDBP}) print $v
10004 (@value{GDBP}) print $_isvoid ($v)
10010 These functions require @value{GDBN} to be configured with
10011 @code{Python} support.
10015 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
10016 @findex $_memeq@r{, convenience function}
10017 Returns one if the @var{length} bytes at the addresses given by
10018 @var{buf1} and @var{buf2} are equal.
10019 Otherwise it returns zero.
10021 @item $_regex(@var{str}, @var{regex})
10022 @findex $_regex@r{, convenience function}
10023 Returns one if the string @var{str} matches the regular expression
10024 @var{regex}. Otherwise it returns zero.
10025 The syntax of the regular expression is that specified by @code{Python}'s
10026 regular expression support.
10028 @item $_streq(@var{str1}, @var{str2})
10029 @findex $_streq@r{, convenience function}
10030 Returns one if the strings @var{str1} and @var{str2} are equal.
10031 Otherwise it returns zero.
10033 @item $_strlen(@var{str})
10034 @findex $_strlen@r{, convenience function}
10035 Returns the length of string @var{str}.
10039 @value{GDBN} provides the ability to list and get help on
10040 convenience functions.
10043 @item help function
10044 @kindex help function
10045 @cindex show all convenience functions
10046 Print a list of all convenience functions.
10053 You can refer to machine register contents, in expressions, as variables
10054 with names starting with @samp{$}. The names of registers are different
10055 for each machine; use @code{info registers} to see the names used on
10059 @kindex info registers
10060 @item info registers
10061 Print the names and values of all registers except floating-point
10062 and vector registers (in the selected stack frame).
10064 @kindex info all-registers
10065 @cindex floating point registers
10066 @item info all-registers
10067 Print the names and values of all registers, including floating-point
10068 and vector registers (in the selected stack frame).
10070 @item info registers @var{regname} @dots{}
10071 Print the @dfn{relativized} value of each specified register @var{regname}.
10072 As discussed in detail below, register values are normally relative to
10073 the selected stack frame. @var{regname} may be any register name valid on
10074 the machine you are using, with or without the initial @samp{$}.
10077 @cindex stack pointer register
10078 @cindex program counter register
10079 @cindex process status register
10080 @cindex frame pointer register
10081 @cindex standard registers
10082 @value{GDBN} has four ``standard'' register names that are available (in
10083 expressions) on most machines---whenever they do not conflict with an
10084 architecture's canonical mnemonics for registers. The register names
10085 @code{$pc} and @code{$sp} are used for the program counter register and
10086 the stack pointer. @code{$fp} is used for a register that contains a
10087 pointer to the current stack frame, and @code{$ps} is used for a
10088 register that contains the processor status. For example,
10089 you could print the program counter in hex with
10096 or print the instruction to be executed next with
10103 or add four to the stack pointer@footnote{This is a way of removing
10104 one word from the stack, on machines where stacks grow downward in
10105 memory (most machines, nowadays). This assumes that the innermost
10106 stack frame is selected; setting @code{$sp} is not allowed when other
10107 stack frames are selected. To pop entire frames off the stack,
10108 regardless of machine architecture, use @code{return};
10109 see @ref{Returning, ,Returning from a Function}.} with
10115 Whenever possible, these four standard register names are available on
10116 your machine even though the machine has different canonical mnemonics,
10117 so long as there is no conflict. The @code{info registers} command
10118 shows the canonical names. For example, on the SPARC, @code{info
10119 registers} displays the processor status register as @code{$psr} but you
10120 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
10121 is an alias for the @sc{eflags} register.
10123 @value{GDBN} always considers the contents of an ordinary register as an
10124 integer when the register is examined in this way. Some machines have
10125 special registers which can hold nothing but floating point; these
10126 registers are considered to have floating point values. There is no way
10127 to refer to the contents of an ordinary register as floating point value
10128 (although you can @emph{print} it as a floating point value with
10129 @samp{print/f $@var{regname}}).
10131 Some registers have distinct ``raw'' and ``virtual'' data formats. This
10132 means that the data format in which the register contents are saved by
10133 the operating system is not the same one that your program normally
10134 sees. For example, the registers of the 68881 floating point
10135 coprocessor are always saved in ``extended'' (raw) format, but all C
10136 programs expect to work with ``double'' (virtual) format. In such
10137 cases, @value{GDBN} normally works with the virtual format only (the format
10138 that makes sense for your program), but the @code{info registers} command
10139 prints the data in both formats.
10141 @cindex SSE registers (x86)
10142 @cindex MMX registers (x86)
10143 Some machines have special registers whose contents can be interpreted
10144 in several different ways. For example, modern x86-based machines
10145 have SSE and MMX registers that can hold several values packed
10146 together in several different formats. @value{GDBN} refers to such
10147 registers in @code{struct} notation:
10150 (@value{GDBP}) print $xmm1
10152 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
10153 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
10154 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
10155 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
10156 v4_int32 = @{0, 20657912, 11, 13@},
10157 v2_int64 = @{88725056443645952, 55834574859@},
10158 uint128 = 0x0000000d0000000b013b36f800000000
10163 To set values of such registers, you need to tell @value{GDBN} which
10164 view of the register you wish to change, as if you were assigning
10165 value to a @code{struct} member:
10168 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
10171 Normally, register values are relative to the selected stack frame
10172 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
10173 value that the register would contain if all stack frames farther in
10174 were exited and their saved registers restored. In order to see the
10175 true contents of hardware registers, you must select the innermost
10176 frame (with @samp{frame 0}).
10178 @cindex caller-saved registers
10179 @cindex call-clobbered registers
10180 @cindex volatile registers
10181 @cindex <not saved> values
10182 Usually ABIs reserve some registers as not needed to be saved by the
10183 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
10184 registers). It may therefore not be possible for @value{GDBN} to know
10185 the value a register had before the call (in other words, in the outer
10186 frame), if the register value has since been changed by the callee.
10187 @value{GDBN} tries to deduce where the inner frame saved
10188 (``callee-saved'') registers, from the debug info, unwind info, or the
10189 machine code generated by your compiler. If some register is not
10190 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
10191 its own knowledge of the ABI, or because the debug/unwind info
10192 explicitly says the register's value is undefined), @value{GDBN}
10193 displays @w{@samp{<not saved>}} as the register's value. With targets
10194 that @value{GDBN} has no knowledge of the register saving convention,
10195 if a register was not saved by the callee, then its value and location
10196 in the outer frame are assumed to be the same of the inner frame.
10197 This is usually harmless, because if the register is call-clobbered,
10198 the caller either does not care what is in the register after the
10199 call, or has code to restore the value that it does care about. Note,
10200 however, that if you change such a register in the outer frame, you
10201 may also be affecting the inner frame. Also, the more ``outer'' the
10202 frame is you're looking at, the more likely a call-clobbered
10203 register's value is to be wrong, in the sense that it doesn't actually
10204 represent the value the register had just before the call.
10206 @node Floating Point Hardware
10207 @section Floating Point Hardware
10208 @cindex floating point
10210 Depending on the configuration, @value{GDBN} may be able to give
10211 you more information about the status of the floating point hardware.
10216 Display hardware-dependent information about the floating
10217 point unit. The exact contents and layout vary depending on the
10218 floating point chip. Currently, @samp{info float} is supported on
10219 the ARM and x86 machines.
10223 @section Vector Unit
10224 @cindex vector unit
10226 Depending on the configuration, @value{GDBN} may be able to give you
10227 more information about the status of the vector unit.
10230 @kindex info vector
10232 Display information about the vector unit. The exact contents and
10233 layout vary depending on the hardware.
10236 @node OS Information
10237 @section Operating System Auxiliary Information
10238 @cindex OS information
10240 @value{GDBN} provides interfaces to useful OS facilities that can help
10241 you debug your program.
10243 @cindex auxiliary vector
10244 @cindex vector, auxiliary
10245 Some operating systems supply an @dfn{auxiliary vector} to programs at
10246 startup. This is akin to the arguments and environment that you
10247 specify for a program, but contains a system-dependent variety of
10248 binary values that tell system libraries important details about the
10249 hardware, operating system, and process. Each value's purpose is
10250 identified by an integer tag; the meanings are well-known but system-specific.
10251 Depending on the configuration and operating system facilities,
10252 @value{GDBN} may be able to show you this information. For remote
10253 targets, this functionality may further depend on the remote stub's
10254 support of the @samp{qXfer:auxv:read} packet, see
10255 @ref{qXfer auxiliary vector read}.
10260 Display the auxiliary vector of the inferior, which can be either a
10261 live process or a core dump file. @value{GDBN} prints each tag value
10262 numerically, and also shows names and text descriptions for recognized
10263 tags. Some values in the vector are numbers, some bit masks, and some
10264 pointers to strings or other data. @value{GDBN} displays each value in the
10265 most appropriate form for a recognized tag, and in hexadecimal for
10266 an unrecognized tag.
10269 On some targets, @value{GDBN} can access operating system-specific
10270 information and show it to you. The types of information available
10271 will differ depending on the type of operating system running on the
10272 target. The mechanism used to fetch the data is described in
10273 @ref{Operating System Information}. For remote targets, this
10274 functionality depends on the remote stub's support of the
10275 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
10279 @item info os @var{infotype}
10281 Display OS information of the requested type.
10283 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
10285 @anchor{linux info os infotypes}
10287 @kindex info os processes
10289 Display the list of processes on the target. For each process,
10290 @value{GDBN} prints the process identifier, the name of the user, the
10291 command corresponding to the process, and the list of processor cores
10292 that the process is currently running on. (To understand what these
10293 properties mean, for this and the following info types, please consult
10294 the general @sc{gnu}/Linux documentation.)
10296 @kindex info os procgroups
10298 Display the list of process groups on the target. For each process,
10299 @value{GDBN} prints the identifier of the process group that it belongs
10300 to, the command corresponding to the process group leader, the process
10301 identifier, and the command line of the process. The list is sorted
10302 first by the process group identifier, then by the process identifier,
10303 so that processes belonging to the same process group are grouped together
10304 and the process group leader is listed first.
10306 @kindex info os threads
10308 Display the list of threads running on the target. For each thread,
10309 @value{GDBN} prints the identifier of the process that the thread
10310 belongs to, the command of the process, the thread identifier, and the
10311 processor core that it is currently running on. The main thread of a
10312 process is not listed.
10314 @kindex info os files
10316 Display the list of open file descriptors on the target. For each
10317 file descriptor, @value{GDBN} prints the identifier of the process
10318 owning the descriptor, the command of the owning process, the value
10319 of the descriptor, and the target of the descriptor.
10321 @kindex info os sockets
10323 Display the list of Internet-domain sockets on the target. For each
10324 socket, @value{GDBN} prints the address and port of the local and
10325 remote endpoints, the current state of the connection, the creator of
10326 the socket, the IP address family of the socket, and the type of the
10329 @kindex info os shm
10331 Display the list of all System V shared-memory regions on the target.
10332 For each shared-memory region, @value{GDBN} prints the region key,
10333 the shared-memory identifier, the access permissions, the size of the
10334 region, the process that created the region, the process that last
10335 attached to or detached from the region, the current number of live
10336 attaches to the region, and the times at which the region was last
10337 attached to, detach from, and changed.
10339 @kindex info os semaphores
10341 Display the list of all System V semaphore sets on the target. For each
10342 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
10343 set identifier, the access permissions, the number of semaphores in the
10344 set, the user and group of the owner and creator of the semaphore set,
10345 and the times at which the semaphore set was operated upon and changed.
10347 @kindex info os msg
10349 Display the list of all System V message queues on the target. For each
10350 message queue, @value{GDBN} prints the message queue key, the message
10351 queue identifier, the access permissions, the current number of bytes
10352 on the queue, the current number of messages on the queue, the processes
10353 that last sent and received a message on the queue, the user and group
10354 of the owner and creator of the message queue, the times at which a
10355 message was last sent and received on the queue, and the time at which
10356 the message queue was last changed.
10358 @kindex info os modules
10360 Display the list of all loaded kernel modules on the target. For each
10361 module, @value{GDBN} prints the module name, the size of the module in
10362 bytes, the number of times the module is used, the dependencies of the
10363 module, the status of the module, and the address of the loaded module
10368 If @var{infotype} is omitted, then list the possible values for
10369 @var{infotype} and the kind of OS information available for each
10370 @var{infotype}. If the target does not return a list of possible
10371 types, this command will report an error.
10374 @node Memory Region Attributes
10375 @section Memory Region Attributes
10376 @cindex memory region attributes
10378 @dfn{Memory region attributes} allow you to describe special handling
10379 required by regions of your target's memory. @value{GDBN} uses
10380 attributes to determine whether to allow certain types of memory
10381 accesses; whether to use specific width accesses; and whether to cache
10382 target memory. By default the description of memory regions is
10383 fetched from the target (if the current target supports this), but the
10384 user can override the fetched regions.
10386 Defined memory regions can be individually enabled and disabled. When a
10387 memory region is disabled, @value{GDBN} uses the default attributes when
10388 accessing memory in that region. Similarly, if no memory regions have
10389 been defined, @value{GDBN} uses the default attributes when accessing
10392 When a memory region is defined, it is given a number to identify it;
10393 to enable, disable, or remove a memory region, you specify that number.
10397 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
10398 Define a memory region bounded by @var{lower} and @var{upper} with
10399 attributes @var{attributes}@dots{}, and add it to the list of regions
10400 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
10401 case: it is treated as the target's maximum memory address.
10402 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
10405 Discard any user changes to the memory regions and use target-supplied
10406 regions, if available, or no regions if the target does not support.
10409 @item delete mem @var{nums}@dots{}
10410 Remove memory regions @var{nums}@dots{} from the list of regions
10411 monitored by @value{GDBN}.
10413 @kindex disable mem
10414 @item disable mem @var{nums}@dots{}
10415 Disable monitoring of memory regions @var{nums}@dots{}.
10416 A disabled memory region is not forgotten.
10417 It may be enabled again later.
10420 @item enable mem @var{nums}@dots{}
10421 Enable monitoring of memory regions @var{nums}@dots{}.
10425 Print a table of all defined memory regions, with the following columns
10429 @item Memory Region Number
10430 @item Enabled or Disabled.
10431 Enabled memory regions are marked with @samp{y}.
10432 Disabled memory regions are marked with @samp{n}.
10435 The address defining the inclusive lower bound of the memory region.
10438 The address defining the exclusive upper bound of the memory region.
10441 The list of attributes set for this memory region.
10446 @subsection Attributes
10448 @subsubsection Memory Access Mode
10449 The access mode attributes set whether @value{GDBN} may make read or
10450 write accesses to a memory region.
10452 While these attributes prevent @value{GDBN} from performing invalid
10453 memory accesses, they do nothing to prevent the target system, I/O DMA,
10454 etc.@: from accessing memory.
10458 Memory is read only.
10460 Memory is write only.
10462 Memory is read/write. This is the default.
10465 @subsubsection Memory Access Size
10466 The access size attribute tells @value{GDBN} to use specific sized
10467 accesses in the memory region. Often memory mapped device registers
10468 require specific sized accesses. If no access size attribute is
10469 specified, @value{GDBN} may use accesses of any size.
10473 Use 8 bit memory accesses.
10475 Use 16 bit memory accesses.
10477 Use 32 bit memory accesses.
10479 Use 64 bit memory accesses.
10482 @c @subsubsection Hardware/Software Breakpoints
10483 @c The hardware/software breakpoint attributes set whether @value{GDBN}
10484 @c will use hardware or software breakpoints for the internal breakpoints
10485 @c used by the step, next, finish, until, etc. commands.
10489 @c Always use hardware breakpoints
10490 @c @item swbreak (default)
10493 @subsubsection Data Cache
10494 The data cache attributes set whether @value{GDBN} will cache target
10495 memory. While this generally improves performance by reducing debug
10496 protocol overhead, it can lead to incorrect results because @value{GDBN}
10497 does not know about volatile variables or memory mapped device
10502 Enable @value{GDBN} to cache target memory.
10504 Disable @value{GDBN} from caching target memory. This is the default.
10507 @subsection Memory Access Checking
10508 @value{GDBN} can be instructed to refuse accesses to memory that is
10509 not explicitly described. This can be useful if accessing such
10510 regions has undesired effects for a specific target, or to provide
10511 better error checking. The following commands control this behaviour.
10514 @kindex set mem inaccessible-by-default
10515 @item set mem inaccessible-by-default [on|off]
10516 If @code{on} is specified, make @value{GDBN} treat memory not
10517 explicitly described by the memory ranges as non-existent and refuse accesses
10518 to such memory. The checks are only performed if there's at least one
10519 memory range defined. If @code{off} is specified, make @value{GDBN}
10520 treat the memory not explicitly described by the memory ranges as RAM.
10521 The default value is @code{on}.
10522 @kindex show mem inaccessible-by-default
10523 @item show mem inaccessible-by-default
10524 Show the current handling of accesses to unknown memory.
10528 @c @subsubsection Memory Write Verification
10529 @c The memory write verification attributes set whether @value{GDBN}
10530 @c will re-reads data after each write to verify the write was successful.
10534 @c @item noverify (default)
10537 @node Dump/Restore Files
10538 @section Copy Between Memory and a File
10539 @cindex dump/restore files
10540 @cindex append data to a file
10541 @cindex dump data to a file
10542 @cindex restore data from a file
10544 You can use the commands @code{dump}, @code{append}, and
10545 @code{restore} to copy data between target memory and a file. The
10546 @code{dump} and @code{append} commands write data to a file, and the
10547 @code{restore} command reads data from a file back into the inferior's
10548 memory. Files may be in binary, Motorola S-record, Intel hex, or
10549 Tektronix Hex format; however, @value{GDBN} can only append to binary
10555 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10556 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
10557 Dump the contents of memory from @var{start_addr} to @var{end_addr},
10558 or the value of @var{expr}, to @var{filename} in the given format.
10560 The @var{format} parameter may be any one of:
10567 Motorola S-record format.
10569 Tektronix Hex format.
10572 @value{GDBN} uses the same definitions of these formats as the
10573 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
10574 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
10578 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10579 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
10580 Append the contents of memory from @var{start_addr} to @var{end_addr},
10581 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
10582 (@value{GDBN} can only append data to files in raw binary form.)
10585 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
10586 Restore the contents of file @var{filename} into memory. The
10587 @code{restore} command can automatically recognize any known @sc{bfd}
10588 file format, except for raw binary. To restore a raw binary file you
10589 must specify the optional keyword @code{binary} after the filename.
10591 If @var{bias} is non-zero, its value will be added to the addresses
10592 contained in the file. Binary files always start at address zero, so
10593 they will be restored at address @var{bias}. Other bfd files have
10594 a built-in location; they will be restored at offset @var{bias}
10595 from that location.
10597 If @var{start} and/or @var{end} are non-zero, then only data between
10598 file offset @var{start} and file offset @var{end} will be restored.
10599 These offsets are relative to the addresses in the file, before
10600 the @var{bias} argument is applied.
10604 @node Core File Generation
10605 @section How to Produce a Core File from Your Program
10606 @cindex dump core from inferior
10608 A @dfn{core file} or @dfn{core dump} is a file that records the memory
10609 image of a running process and its process status (register values
10610 etc.). Its primary use is post-mortem debugging of a program that
10611 crashed while it ran outside a debugger. A program that crashes
10612 automatically produces a core file, unless this feature is disabled by
10613 the user. @xref{Files}, for information on invoking @value{GDBN} in
10614 the post-mortem debugging mode.
10616 Occasionally, you may wish to produce a core file of the program you
10617 are debugging in order to preserve a snapshot of its state.
10618 @value{GDBN} has a special command for that.
10622 @kindex generate-core-file
10623 @item generate-core-file [@var{file}]
10624 @itemx gcore [@var{file}]
10625 Produce a core dump of the inferior process. The optional argument
10626 @var{file} specifies the file name where to put the core dump. If not
10627 specified, the file name defaults to @file{core.@var{pid}}, where
10628 @var{pid} is the inferior process ID.
10630 Note that this command is implemented only for some systems (as of
10631 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
10634 @node Character Sets
10635 @section Character Sets
10636 @cindex character sets
10638 @cindex translating between character sets
10639 @cindex host character set
10640 @cindex target character set
10642 If the program you are debugging uses a different character set to
10643 represent characters and strings than the one @value{GDBN} uses itself,
10644 @value{GDBN} can automatically translate between the character sets for
10645 you. The character set @value{GDBN} uses we call the @dfn{host
10646 character set}; the one the inferior program uses we call the
10647 @dfn{target character set}.
10649 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
10650 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
10651 remote protocol (@pxref{Remote Debugging}) to debug a program
10652 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
10653 then the host character set is Latin-1, and the target character set is
10654 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
10655 target-charset EBCDIC-US}, then @value{GDBN} translates between
10656 @sc{ebcdic} and Latin 1 as you print character or string values, or use
10657 character and string literals in expressions.
10659 @value{GDBN} has no way to automatically recognize which character set
10660 the inferior program uses; you must tell it, using the @code{set
10661 target-charset} command, described below.
10663 Here are the commands for controlling @value{GDBN}'s character set
10667 @item set target-charset @var{charset}
10668 @kindex set target-charset
10669 Set the current target character set to @var{charset}. To display the
10670 list of supported target character sets, type
10671 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
10673 @item set host-charset @var{charset}
10674 @kindex set host-charset
10675 Set the current host character set to @var{charset}.
10677 By default, @value{GDBN} uses a host character set appropriate to the
10678 system it is running on; you can override that default using the
10679 @code{set host-charset} command. On some systems, @value{GDBN} cannot
10680 automatically determine the appropriate host character set. In this
10681 case, @value{GDBN} uses @samp{UTF-8}.
10683 @value{GDBN} can only use certain character sets as its host character
10684 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
10685 @value{GDBN} will list the host character sets it supports.
10687 @item set charset @var{charset}
10688 @kindex set charset
10689 Set the current host and target character sets to @var{charset}. As
10690 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
10691 @value{GDBN} will list the names of the character sets that can be used
10692 for both host and target.
10695 @kindex show charset
10696 Show the names of the current host and target character sets.
10698 @item show host-charset
10699 @kindex show host-charset
10700 Show the name of the current host character set.
10702 @item show target-charset
10703 @kindex show target-charset
10704 Show the name of the current target character set.
10706 @item set target-wide-charset @var{charset}
10707 @kindex set target-wide-charset
10708 Set the current target's wide character set to @var{charset}. This is
10709 the character set used by the target's @code{wchar_t} type. To
10710 display the list of supported wide character sets, type
10711 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
10713 @item show target-wide-charset
10714 @kindex show target-wide-charset
10715 Show the name of the current target's wide character set.
10718 Here is an example of @value{GDBN}'s character set support in action.
10719 Assume that the following source code has been placed in the file
10720 @file{charset-test.c}:
10726 = @{72, 101, 108, 108, 111, 44, 32, 119,
10727 111, 114, 108, 100, 33, 10, 0@};
10728 char ibm1047_hello[]
10729 = @{200, 133, 147, 147, 150, 107, 64, 166,
10730 150, 153, 147, 132, 90, 37, 0@};
10734 printf ("Hello, world!\n");
10738 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
10739 containing the string @samp{Hello, world!} followed by a newline,
10740 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
10742 We compile the program, and invoke the debugger on it:
10745 $ gcc -g charset-test.c -o charset-test
10746 $ gdb -nw charset-test
10747 GNU gdb 2001-12-19-cvs
10748 Copyright 2001 Free Software Foundation, Inc.
10753 We can use the @code{show charset} command to see what character sets
10754 @value{GDBN} is currently using to interpret and display characters and
10758 (@value{GDBP}) show charset
10759 The current host and target character set is `ISO-8859-1'.
10763 For the sake of printing this manual, let's use @sc{ascii} as our
10764 initial character set:
10766 (@value{GDBP}) set charset ASCII
10767 (@value{GDBP}) show charset
10768 The current host and target character set is `ASCII'.
10772 Let's assume that @sc{ascii} is indeed the correct character set for our
10773 host system --- in other words, let's assume that if @value{GDBN} prints
10774 characters using the @sc{ascii} character set, our terminal will display
10775 them properly. Since our current target character set is also
10776 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
10779 (@value{GDBP}) print ascii_hello
10780 $1 = 0x401698 "Hello, world!\n"
10781 (@value{GDBP}) print ascii_hello[0]
10786 @value{GDBN} uses the target character set for character and string
10787 literals you use in expressions:
10790 (@value{GDBP}) print '+'
10795 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
10798 @value{GDBN} relies on the user to tell it which character set the
10799 target program uses. If we print @code{ibm1047_hello} while our target
10800 character set is still @sc{ascii}, we get jibberish:
10803 (@value{GDBP}) print ibm1047_hello
10804 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
10805 (@value{GDBP}) print ibm1047_hello[0]
10810 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
10811 @value{GDBN} tells us the character sets it supports:
10814 (@value{GDBP}) set target-charset
10815 ASCII EBCDIC-US IBM1047 ISO-8859-1
10816 (@value{GDBP}) set target-charset
10819 We can select @sc{ibm1047} as our target character set, and examine the
10820 program's strings again. Now the @sc{ascii} string is wrong, but
10821 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
10822 target character set, @sc{ibm1047}, to the host character set,
10823 @sc{ascii}, and they display correctly:
10826 (@value{GDBP}) set target-charset IBM1047
10827 (@value{GDBP}) show charset
10828 The current host character set is `ASCII'.
10829 The current target character set is `IBM1047'.
10830 (@value{GDBP}) print ascii_hello
10831 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
10832 (@value{GDBP}) print ascii_hello[0]
10834 (@value{GDBP}) print ibm1047_hello
10835 $8 = 0x4016a8 "Hello, world!\n"
10836 (@value{GDBP}) print ibm1047_hello[0]
10841 As above, @value{GDBN} uses the target character set for character and
10842 string literals you use in expressions:
10845 (@value{GDBP}) print '+'
10850 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
10853 @node Caching Target Data
10854 @section Caching Data of Targets
10855 @cindex caching data of targets
10857 @value{GDBN} caches data exchanged between the debugger and a target.
10858 Each cache is associated with the address space of the inferior.
10859 @xref{Inferiors and Programs}, about inferior and address space.
10860 Such caching generally improves performance in remote debugging
10861 (@pxref{Remote Debugging}), because it reduces the overhead of the
10862 remote protocol by bundling memory reads and writes into large chunks.
10863 Unfortunately, simply caching everything would lead to incorrect results,
10864 since @value{GDBN} does not necessarily know anything about volatile
10865 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
10866 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
10868 Therefore, by default, @value{GDBN} only caches data
10869 known to be on the stack@footnote{In non-stop mode, it is moderately
10870 rare for a running thread to modify the stack of a stopped thread
10871 in a way that would interfere with a backtrace, and caching of
10872 stack reads provides a significant speed up of remote backtraces.} or
10873 in the code segment.
10874 Other regions of memory can be explicitly marked as
10875 cacheable; @pxref{Memory Region Attributes}.
10878 @kindex set remotecache
10879 @item set remotecache on
10880 @itemx set remotecache off
10881 This option no longer does anything; it exists for compatibility
10884 @kindex show remotecache
10885 @item show remotecache
10886 Show the current state of the obsolete remotecache flag.
10888 @kindex set stack-cache
10889 @item set stack-cache on
10890 @itemx set stack-cache off
10891 Enable or disable caching of stack accesses. When @code{on}, use
10892 caching. By default, this option is @code{on}.
10894 @kindex show stack-cache
10895 @item show stack-cache
10896 Show the current state of data caching for memory accesses.
10898 @kindex set code-cache
10899 @item set code-cache on
10900 @itemx set code-cache off
10901 Enable or disable caching of code segment accesses. When @code{on},
10902 use caching. By default, this option is @code{on}. This improves
10903 performance of disassembly in remote debugging.
10905 @kindex show code-cache
10906 @item show code-cache
10907 Show the current state of target memory cache for code segment
10910 @kindex info dcache
10911 @item info dcache @r{[}line@r{]}
10912 Print the information about the performance of data cache of the
10913 current inferior's address space. The information displayed
10914 includes the dcache width and depth, and for each cache line, its
10915 number, address, and how many times it was referenced. This
10916 command is useful for debugging the data cache operation.
10918 If a line number is specified, the contents of that line will be
10921 @item set dcache size @var{size}
10922 @cindex dcache size
10923 @kindex set dcache size
10924 Set maximum number of entries in dcache (dcache depth above).
10926 @item set dcache line-size @var{line-size}
10927 @cindex dcache line-size
10928 @kindex set dcache line-size
10929 Set number of bytes each dcache entry caches (dcache width above).
10930 Must be a power of 2.
10932 @item show dcache size
10933 @kindex show dcache size
10934 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
10936 @item show dcache line-size
10937 @kindex show dcache line-size
10938 Show default size of dcache lines.
10942 @node Searching Memory
10943 @section Search Memory
10944 @cindex searching memory
10946 Memory can be searched for a particular sequence of bytes with the
10947 @code{find} command.
10951 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10952 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10953 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
10954 etc. The search begins at address @var{start_addr} and continues for either
10955 @var{len} bytes or through to @var{end_addr} inclusive.
10958 @var{s} and @var{n} are optional parameters.
10959 They may be specified in either order, apart or together.
10962 @item @var{s}, search query size
10963 The size of each search query value.
10969 halfwords (two bytes)
10973 giant words (eight bytes)
10976 All values are interpreted in the current language.
10977 This means, for example, that if the current source language is C/C@t{++}
10978 then searching for the string ``hello'' includes the trailing '\0'.
10980 If the value size is not specified, it is taken from the
10981 value's type in the current language.
10982 This is useful when one wants to specify the search
10983 pattern as a mixture of types.
10984 Note that this means, for example, that in the case of C-like languages
10985 a search for an untyped 0x42 will search for @samp{(int) 0x42}
10986 which is typically four bytes.
10988 @item @var{n}, maximum number of finds
10989 The maximum number of matches to print. The default is to print all finds.
10992 You can use strings as search values. Quote them with double-quotes
10994 The string value is copied into the search pattern byte by byte,
10995 regardless of the endianness of the target and the size specification.
10997 The address of each match found is printed as well as a count of the
10998 number of matches found.
11000 The address of the last value found is stored in convenience variable
11002 A count of the number of matches is stored in @samp{$numfound}.
11004 For example, if stopped at the @code{printf} in this function:
11010 static char hello[] = "hello-hello";
11011 static struct @{ char c; short s; int i; @}
11012 __attribute__ ((packed)) mixed
11013 = @{ 'c', 0x1234, 0x87654321 @};
11014 printf ("%s\n", hello);
11019 you get during debugging:
11022 (gdb) find &hello[0], +sizeof(hello), "hello"
11023 0x804956d <hello.1620+6>
11025 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
11026 0x8049567 <hello.1620>
11027 0x804956d <hello.1620+6>
11029 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
11030 0x8049567 <hello.1620>
11032 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
11033 0x8049560 <mixed.1625>
11035 (gdb) print $numfound
11038 $2 = (void *) 0x8049560
11041 @node Optimized Code
11042 @chapter Debugging Optimized Code
11043 @cindex optimized code, debugging
11044 @cindex debugging optimized code
11046 Almost all compilers support optimization. With optimization
11047 disabled, the compiler generates assembly code that corresponds
11048 directly to your source code, in a simplistic way. As the compiler
11049 applies more powerful optimizations, the generated assembly code
11050 diverges from your original source code. With help from debugging
11051 information generated by the compiler, @value{GDBN} can map from
11052 the running program back to constructs from your original source.
11054 @value{GDBN} is more accurate with optimization disabled. If you
11055 can recompile without optimization, it is easier to follow the
11056 progress of your program during debugging. But, there are many cases
11057 where you may need to debug an optimized version.
11059 When you debug a program compiled with @samp{-g -O}, remember that the
11060 optimizer has rearranged your code; the debugger shows you what is
11061 really there. Do not be too surprised when the execution path does not
11062 exactly match your source file! An extreme example: if you define a
11063 variable, but never use it, @value{GDBN} never sees that
11064 variable---because the compiler optimizes it out of existence.
11066 Some things do not work as well with @samp{-g -O} as with just
11067 @samp{-g}, particularly on machines with instruction scheduling. If in
11068 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
11069 please report it to us as a bug (including a test case!).
11070 @xref{Variables}, for more information about debugging optimized code.
11073 * Inline Functions:: How @value{GDBN} presents inlining
11074 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
11077 @node Inline Functions
11078 @section Inline Functions
11079 @cindex inline functions, debugging
11081 @dfn{Inlining} is an optimization that inserts a copy of the function
11082 body directly at each call site, instead of jumping to a shared
11083 routine. @value{GDBN} displays inlined functions just like
11084 non-inlined functions. They appear in backtraces. You can view their
11085 arguments and local variables, step into them with @code{step}, skip
11086 them with @code{next}, and escape from them with @code{finish}.
11087 You can check whether a function was inlined by using the
11088 @code{info frame} command.
11090 For @value{GDBN} to support inlined functions, the compiler must
11091 record information about inlining in the debug information ---
11092 @value{NGCC} using the @sc{dwarf 2} format does this, and several
11093 other compilers do also. @value{GDBN} only supports inlined functions
11094 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
11095 do not emit two required attributes (@samp{DW_AT_call_file} and
11096 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
11097 function calls with earlier versions of @value{NGCC}. It instead
11098 displays the arguments and local variables of inlined functions as
11099 local variables in the caller.
11101 The body of an inlined function is directly included at its call site;
11102 unlike a non-inlined function, there are no instructions devoted to
11103 the call. @value{GDBN} still pretends that the call site and the
11104 start of the inlined function are different instructions. Stepping to
11105 the call site shows the call site, and then stepping again shows
11106 the first line of the inlined function, even though no additional
11107 instructions are executed.
11109 This makes source-level debugging much clearer; you can see both the
11110 context of the call and then the effect of the call. Only stepping by
11111 a single instruction using @code{stepi} or @code{nexti} does not do
11112 this; single instruction steps always show the inlined body.
11114 There are some ways that @value{GDBN} does not pretend that inlined
11115 function calls are the same as normal calls:
11119 Setting breakpoints at the call site of an inlined function may not
11120 work, because the call site does not contain any code. @value{GDBN}
11121 may incorrectly move the breakpoint to the next line of the enclosing
11122 function, after the call. This limitation will be removed in a future
11123 version of @value{GDBN}; until then, set a breakpoint on an earlier line
11124 or inside the inlined function instead.
11127 @value{GDBN} cannot locate the return value of inlined calls after
11128 using the @code{finish} command. This is a limitation of compiler-generated
11129 debugging information; after @code{finish}, you can step to the next line
11130 and print a variable where your program stored the return value.
11134 @node Tail Call Frames
11135 @section Tail Call Frames
11136 @cindex tail call frames, debugging
11138 Function @code{B} can call function @code{C} in its very last statement. In
11139 unoptimized compilation the call of @code{C} is immediately followed by return
11140 instruction at the end of @code{B} code. Optimizing compiler may replace the
11141 call and return in function @code{B} into one jump to function @code{C}
11142 instead. Such use of a jump instruction is called @dfn{tail call}.
11144 During execution of function @code{C}, there will be no indication in the
11145 function call stack frames that it was tail-called from @code{B}. If function
11146 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
11147 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
11148 some cases @value{GDBN} can determine that @code{C} was tail-called from
11149 @code{B}, and it will then create fictitious call frame for that, with the
11150 return address set up as if @code{B} called @code{C} normally.
11152 This functionality is currently supported only by DWARF 2 debugging format and
11153 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
11154 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
11157 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
11158 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
11162 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
11164 Stack level 1, frame at 0x7fffffffda30:
11165 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
11166 tail call frame, caller of frame at 0x7fffffffda30
11167 source language c++.
11168 Arglist at unknown address.
11169 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
11172 The detection of all the possible code path executions can find them ambiguous.
11173 There is no execution history stored (possible @ref{Reverse Execution} is never
11174 used for this purpose) and the last known caller could have reached the known
11175 callee by multiple different jump sequences. In such case @value{GDBN} still
11176 tries to show at least all the unambiguous top tail callers and all the
11177 unambiguous bottom tail calees, if any.
11180 @anchor{set debug entry-values}
11181 @item set debug entry-values
11182 @kindex set debug entry-values
11183 When set to on, enables printing of analysis messages for both frame argument
11184 values at function entry and tail calls. It will show all the possible valid
11185 tail calls code paths it has considered. It will also print the intersection
11186 of them with the final unambiguous (possibly partial or even empty) code path
11189 @item show debug entry-values
11190 @kindex show debug entry-values
11191 Show the current state of analysis messages printing for both frame argument
11192 values at function entry and tail calls.
11195 The analysis messages for tail calls can for example show why the virtual tail
11196 call frame for function @code{c} has not been recognized (due to the indirect
11197 reference by variable @code{x}):
11200 static void __attribute__((noinline, noclone)) c (void);
11201 void (*x) (void) = c;
11202 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11203 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
11204 int main (void) @{ x (); return 0; @}
11206 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
11207 DW_TAG_GNU_call_site 0x40039a in main
11209 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11212 #1 0x000000000040039a in main () at t.c:5
11215 Another possibility is an ambiguous virtual tail call frames resolution:
11219 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
11220 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
11221 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
11222 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
11223 static void __attribute__((noinline, noclone)) b (void)
11224 @{ if (i) c (); else e (); @}
11225 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
11226 int main (void) @{ a (); return 0; @}
11228 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
11229 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
11230 tailcall: reduced: 0x4004d2(a) |
11233 #1 0x00000000004004d2 in a () at t.c:8
11234 #2 0x0000000000400395 in main () at t.c:9
11237 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
11238 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
11240 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
11241 @ifset HAVE_MAKEINFO_CLICK
11242 @set ARROW @click{}
11243 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
11244 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
11246 @ifclear HAVE_MAKEINFO_CLICK
11248 @set CALLSEQ1B @value{CALLSEQ1A}
11249 @set CALLSEQ2B @value{CALLSEQ2A}
11252 Frames #0 and #2 are real, #1 is a virtual tail call frame.
11253 The code can have possible execution paths @value{CALLSEQ1B} or
11254 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
11256 @code{initial:} state shows some random possible calling sequence @value{GDBN}
11257 has found. It then finds another possible calling sequcen - that one is
11258 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
11259 printed as the @code{reduced:} calling sequence. That one could have many
11260 futher @code{compare:} and @code{reduced:} statements as long as there remain
11261 any non-ambiguous sequence entries.
11263 For the frame of function @code{b} in both cases there are different possible
11264 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
11265 also ambigous. The only non-ambiguous frame is the one for function @code{a},
11266 therefore this one is displayed to the user while the ambiguous frames are
11269 There can be also reasons why printing of frame argument values at function
11274 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
11275 static void __attribute__((noinline, noclone)) a (int i);
11276 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
11277 static void __attribute__((noinline, noclone)) a (int i)
11278 @{ if (i) b (i - 1); else c (0); @}
11279 int main (void) @{ a (5); return 0; @}
11282 #0 c (i=i@@entry=0) at t.c:2
11283 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
11284 function "a" at 0x400420 can call itself via tail calls
11285 i=<optimized out>) at t.c:6
11286 #2 0x000000000040036e in main () at t.c:7
11289 @value{GDBN} cannot find out from the inferior state if and how many times did
11290 function @code{a} call itself (via function @code{b}) as these calls would be
11291 tail calls. Such tail calls would modify thue @code{i} variable, therefore
11292 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
11293 prints @code{<optimized out>} instead.
11296 @chapter C Preprocessor Macros
11298 Some languages, such as C and C@t{++}, provide a way to define and invoke
11299 ``preprocessor macros'' which expand into strings of tokens.
11300 @value{GDBN} can evaluate expressions containing macro invocations, show
11301 the result of macro expansion, and show a macro's definition, including
11302 where it was defined.
11304 You may need to compile your program specially to provide @value{GDBN}
11305 with information about preprocessor macros. Most compilers do not
11306 include macros in their debugging information, even when you compile
11307 with the @option{-g} flag. @xref{Compilation}.
11309 A program may define a macro at one point, remove that definition later,
11310 and then provide a different definition after that. Thus, at different
11311 points in the program, a macro may have different definitions, or have
11312 no definition at all. If there is a current stack frame, @value{GDBN}
11313 uses the macros in scope at that frame's source code line. Otherwise,
11314 @value{GDBN} uses the macros in scope at the current listing location;
11317 Whenever @value{GDBN} evaluates an expression, it always expands any
11318 macro invocations present in the expression. @value{GDBN} also provides
11319 the following commands for working with macros explicitly.
11323 @kindex macro expand
11324 @cindex macro expansion, showing the results of preprocessor
11325 @cindex preprocessor macro expansion, showing the results of
11326 @cindex expanding preprocessor macros
11327 @item macro expand @var{expression}
11328 @itemx macro exp @var{expression}
11329 Show the results of expanding all preprocessor macro invocations in
11330 @var{expression}. Since @value{GDBN} simply expands macros, but does
11331 not parse the result, @var{expression} need not be a valid expression;
11332 it can be any string of tokens.
11335 @item macro expand-once @var{expression}
11336 @itemx macro exp1 @var{expression}
11337 @cindex expand macro once
11338 @i{(This command is not yet implemented.)} Show the results of
11339 expanding those preprocessor macro invocations that appear explicitly in
11340 @var{expression}. Macro invocations appearing in that expansion are
11341 left unchanged. This command allows you to see the effect of a
11342 particular macro more clearly, without being confused by further
11343 expansions. Since @value{GDBN} simply expands macros, but does not
11344 parse the result, @var{expression} need not be a valid expression; it
11345 can be any string of tokens.
11348 @cindex macro definition, showing
11349 @cindex definition of a macro, showing
11350 @cindex macros, from debug info
11351 @item info macro [-a|-all] [--] @var{macro}
11352 Show the current definition or all definitions of the named @var{macro},
11353 and describe the source location or compiler command-line where that
11354 definition was established. The optional double dash is to signify the end of
11355 argument processing and the beginning of @var{macro} for non C-like macros where
11356 the macro may begin with a hyphen.
11358 @kindex info macros
11359 @item info macros @var{linespec}
11360 Show all macro definitions that are in effect at the location specified
11361 by @var{linespec}, and describe the source location or compiler
11362 command-line where those definitions were established.
11364 @kindex macro define
11365 @cindex user-defined macros
11366 @cindex defining macros interactively
11367 @cindex macros, user-defined
11368 @item macro define @var{macro} @var{replacement-list}
11369 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
11370 Introduce a definition for a preprocessor macro named @var{macro},
11371 invocations of which are replaced by the tokens given in
11372 @var{replacement-list}. The first form of this command defines an
11373 ``object-like'' macro, which takes no arguments; the second form
11374 defines a ``function-like'' macro, which takes the arguments given in
11377 A definition introduced by this command is in scope in every
11378 expression evaluated in @value{GDBN}, until it is removed with the
11379 @code{macro undef} command, described below. The definition overrides
11380 all definitions for @var{macro} present in the program being debugged,
11381 as well as any previous user-supplied definition.
11383 @kindex macro undef
11384 @item macro undef @var{macro}
11385 Remove any user-supplied definition for the macro named @var{macro}.
11386 This command only affects definitions provided with the @code{macro
11387 define} command, described above; it cannot remove definitions present
11388 in the program being debugged.
11392 List all the macros defined using the @code{macro define} command.
11395 @cindex macros, example of debugging with
11396 Here is a transcript showing the above commands in action. First, we
11397 show our source files:
11402 #include "sample.h"
11405 #define ADD(x) (M + x)
11410 printf ("Hello, world!\n");
11412 printf ("We're so creative.\n");
11414 printf ("Goodbye, world!\n");
11421 Now, we compile the program using the @sc{gnu} C compiler,
11422 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
11423 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
11424 and @option{-gdwarf-4}; we recommend always choosing the most recent
11425 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
11426 includes information about preprocessor macros in the debugging
11430 $ gcc -gdwarf-2 -g3 sample.c -o sample
11434 Now, we start @value{GDBN} on our sample program:
11438 GNU gdb 2002-05-06-cvs
11439 Copyright 2002 Free Software Foundation, Inc.
11440 GDB is free software, @dots{}
11444 We can expand macros and examine their definitions, even when the
11445 program is not running. @value{GDBN} uses the current listing position
11446 to decide which macro definitions are in scope:
11449 (@value{GDBP}) list main
11452 5 #define ADD(x) (M + x)
11457 10 printf ("Hello, world!\n");
11459 12 printf ("We're so creative.\n");
11460 (@value{GDBP}) info macro ADD
11461 Defined at /home/jimb/gdb/macros/play/sample.c:5
11462 #define ADD(x) (M + x)
11463 (@value{GDBP}) info macro Q
11464 Defined at /home/jimb/gdb/macros/play/sample.h:1
11465 included at /home/jimb/gdb/macros/play/sample.c:2
11467 (@value{GDBP}) macro expand ADD(1)
11468 expands to: (42 + 1)
11469 (@value{GDBP}) macro expand-once ADD(1)
11470 expands to: once (M + 1)
11474 In the example above, note that @code{macro expand-once} expands only
11475 the macro invocation explicit in the original text --- the invocation of
11476 @code{ADD} --- but does not expand the invocation of the macro @code{M},
11477 which was introduced by @code{ADD}.
11479 Once the program is running, @value{GDBN} uses the macro definitions in
11480 force at the source line of the current stack frame:
11483 (@value{GDBP}) break main
11484 Breakpoint 1 at 0x8048370: file sample.c, line 10.
11486 Starting program: /home/jimb/gdb/macros/play/sample
11488 Breakpoint 1, main () at sample.c:10
11489 10 printf ("Hello, world!\n");
11493 At line 10, the definition of the macro @code{N} at line 9 is in force:
11496 (@value{GDBP}) info macro N
11497 Defined at /home/jimb/gdb/macros/play/sample.c:9
11499 (@value{GDBP}) macro expand N Q M
11500 expands to: 28 < 42
11501 (@value{GDBP}) print N Q M
11506 As we step over directives that remove @code{N}'s definition, and then
11507 give it a new definition, @value{GDBN} finds the definition (or lack
11508 thereof) in force at each point:
11511 (@value{GDBP}) next
11513 12 printf ("We're so creative.\n");
11514 (@value{GDBP}) info macro N
11515 The symbol `N' has no definition as a C/C++ preprocessor macro
11516 at /home/jimb/gdb/macros/play/sample.c:12
11517 (@value{GDBP}) next
11519 14 printf ("Goodbye, world!\n");
11520 (@value{GDBP}) info macro N
11521 Defined at /home/jimb/gdb/macros/play/sample.c:13
11523 (@value{GDBP}) macro expand N Q M
11524 expands to: 1729 < 42
11525 (@value{GDBP}) print N Q M
11530 In addition to source files, macros can be defined on the compilation command
11531 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
11532 such a way, @value{GDBN} displays the location of their definition as line zero
11533 of the source file submitted to the compiler.
11536 (@value{GDBP}) info macro __STDC__
11537 Defined at /home/jimb/gdb/macros/play/sample.c:0
11544 @chapter Tracepoints
11545 @c This chapter is based on the documentation written by Michael
11546 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
11548 @cindex tracepoints
11549 In some applications, it is not feasible for the debugger to interrupt
11550 the program's execution long enough for the developer to learn
11551 anything helpful about its behavior. If the program's correctness
11552 depends on its real-time behavior, delays introduced by a debugger
11553 might cause the program to change its behavior drastically, or perhaps
11554 fail, even when the code itself is correct. It is useful to be able
11555 to observe the program's behavior without interrupting it.
11557 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
11558 specify locations in the program, called @dfn{tracepoints}, and
11559 arbitrary expressions to evaluate when those tracepoints are reached.
11560 Later, using the @code{tfind} command, you can examine the values
11561 those expressions had when the program hit the tracepoints. The
11562 expressions may also denote objects in memory---structures or arrays,
11563 for example---whose values @value{GDBN} should record; while visiting
11564 a particular tracepoint, you may inspect those objects as if they were
11565 in memory at that moment. However, because @value{GDBN} records these
11566 values without interacting with you, it can do so quickly and
11567 unobtrusively, hopefully not disturbing the program's behavior.
11569 The tracepoint facility is currently available only for remote
11570 targets. @xref{Targets}. In addition, your remote target must know
11571 how to collect trace data. This functionality is implemented in the
11572 remote stub; however, none of the stubs distributed with @value{GDBN}
11573 support tracepoints as of this writing. The format of the remote
11574 packets used to implement tracepoints are described in @ref{Tracepoint
11577 It is also possible to get trace data from a file, in a manner reminiscent
11578 of corefiles; you specify the filename, and use @code{tfind} to search
11579 through the file. @xref{Trace Files}, for more details.
11581 This chapter describes the tracepoint commands and features.
11584 * Set Tracepoints::
11585 * Analyze Collected Data::
11586 * Tracepoint Variables::
11590 @node Set Tracepoints
11591 @section Commands to Set Tracepoints
11593 Before running such a @dfn{trace experiment}, an arbitrary number of
11594 tracepoints can be set. A tracepoint is actually a special type of
11595 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
11596 standard breakpoint commands. For instance, as with breakpoints,
11597 tracepoint numbers are successive integers starting from one, and many
11598 of the commands associated with tracepoints take the tracepoint number
11599 as their argument, to identify which tracepoint to work on.
11601 For each tracepoint, you can specify, in advance, some arbitrary set
11602 of data that you want the target to collect in the trace buffer when
11603 it hits that tracepoint. The collected data can include registers,
11604 local variables, or global data. Later, you can use @value{GDBN}
11605 commands to examine the values these data had at the time the
11606 tracepoint was hit.
11608 Tracepoints do not support every breakpoint feature. Ignore counts on
11609 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
11610 commands when they are hit. Tracepoints may not be thread-specific
11613 @cindex fast tracepoints
11614 Some targets may support @dfn{fast tracepoints}, which are inserted in
11615 a different way (such as with a jump instead of a trap), that is
11616 faster but possibly restricted in where they may be installed.
11618 @cindex static tracepoints
11619 @cindex markers, static tracepoints
11620 @cindex probing markers, static tracepoints
11621 Regular and fast tracepoints are dynamic tracing facilities, meaning
11622 that they can be used to insert tracepoints at (almost) any location
11623 in the target. Some targets may also support controlling @dfn{static
11624 tracepoints} from @value{GDBN}. With static tracing, a set of
11625 instrumentation points, also known as @dfn{markers}, are embedded in
11626 the target program, and can be activated or deactivated by name or
11627 address. These are usually placed at locations which facilitate
11628 investigating what the target is actually doing. @value{GDBN}'s
11629 support for static tracing includes being able to list instrumentation
11630 points, and attach them with @value{GDBN} defined high level
11631 tracepoints that expose the whole range of convenience of
11632 @value{GDBN}'s tracepoints support. Namely, support for collecting
11633 registers values and values of global or local (to the instrumentation
11634 point) variables; tracepoint conditions and trace state variables.
11635 The act of installing a @value{GDBN} static tracepoint on an
11636 instrumentation point, or marker, is referred to as @dfn{probing} a
11637 static tracepoint marker.
11639 @code{gdbserver} supports tracepoints on some target systems.
11640 @xref{Server,,Tracepoints support in @code{gdbserver}}.
11642 This section describes commands to set tracepoints and associated
11643 conditions and actions.
11646 * Create and Delete Tracepoints::
11647 * Enable and Disable Tracepoints::
11648 * Tracepoint Passcounts::
11649 * Tracepoint Conditions::
11650 * Trace State Variables::
11651 * Tracepoint Actions::
11652 * Listing Tracepoints::
11653 * Listing Static Tracepoint Markers::
11654 * Starting and Stopping Trace Experiments::
11655 * Tracepoint Restrictions::
11658 @node Create and Delete Tracepoints
11659 @subsection Create and Delete Tracepoints
11662 @cindex set tracepoint
11664 @item trace @var{location}
11665 The @code{trace} command is very similar to the @code{break} command.
11666 Its argument @var{location} can be a source line, a function name, or
11667 an address in the target program. @xref{Specify Location}. The
11668 @code{trace} command defines a tracepoint, which is a point in the
11669 target program where the debugger will briefly stop, collect some
11670 data, and then allow the program to continue. Setting a tracepoint or
11671 changing its actions takes effect immediately if the remote stub
11672 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
11674 If remote stub doesn't support the @samp{InstallInTrace} feature, all
11675 these changes don't take effect until the next @code{tstart}
11676 command, and once a trace experiment is running, further changes will
11677 not have any effect until the next trace experiment starts. In addition,
11678 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
11679 address is not yet resolved. (This is similar to pending breakpoints.)
11680 Pending tracepoints are not downloaded to the target and not installed
11681 until they are resolved. The resolution of pending tracepoints requires
11682 @value{GDBN} support---when debugging with the remote target, and
11683 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
11684 tracing}), pending tracepoints can not be resolved (and downloaded to
11685 the remote stub) while @value{GDBN} is disconnected.
11687 Here are some examples of using the @code{trace} command:
11690 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
11692 (@value{GDBP}) @b{trace +2} // 2 lines forward
11694 (@value{GDBP}) @b{trace my_function} // first source line of function
11696 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
11698 (@value{GDBP}) @b{trace *0x2117c4} // an address
11702 You can abbreviate @code{trace} as @code{tr}.
11704 @item trace @var{location} if @var{cond}
11705 Set a tracepoint with condition @var{cond}; evaluate the expression
11706 @var{cond} each time the tracepoint is reached, and collect data only
11707 if the value is nonzero---that is, if @var{cond} evaluates as true.
11708 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
11709 information on tracepoint conditions.
11711 @item ftrace @var{location} [ if @var{cond} ]
11712 @cindex set fast tracepoint
11713 @cindex fast tracepoints, setting
11715 The @code{ftrace} command sets a fast tracepoint. For targets that
11716 support them, fast tracepoints will use a more efficient but possibly
11717 less general technique to trigger data collection, such as a jump
11718 instruction instead of a trap, or some sort of hardware support. It
11719 may not be possible to create a fast tracepoint at the desired
11720 location, in which case the command will exit with an explanatory
11723 @value{GDBN} handles arguments to @code{ftrace} exactly as for
11726 On 32-bit x86-architecture systems, fast tracepoints normally need to
11727 be placed at an instruction that is 5 bytes or longer, but can be
11728 placed at 4-byte instructions if the low 64K of memory of the target
11729 program is available to install trampolines. Some Unix-type systems,
11730 such as @sc{gnu}/Linux, exclude low addresses from the program's
11731 address space; but for instance with the Linux kernel it is possible
11732 to let @value{GDBN} use this area by doing a @command{sysctl} command
11733 to set the @code{mmap_min_addr} kernel parameter, as in
11736 sudo sysctl -w vm.mmap_min_addr=32768
11740 which sets the low address to 32K, which leaves plenty of room for
11741 trampolines. The minimum address should be set to a page boundary.
11743 @item strace @var{location} [ if @var{cond} ]
11744 @cindex set static tracepoint
11745 @cindex static tracepoints, setting
11746 @cindex probe static tracepoint marker
11748 The @code{strace} command sets a static tracepoint. For targets that
11749 support it, setting a static tracepoint probes a static
11750 instrumentation point, or marker, found at @var{location}. It may not
11751 be possible to set a static tracepoint at the desired location, in
11752 which case the command will exit with an explanatory message.
11754 @value{GDBN} handles arguments to @code{strace} exactly as for
11755 @code{trace}, with the addition that the user can also specify
11756 @code{-m @var{marker}} as @var{location}. This probes the marker
11757 identified by the @var{marker} string identifier. This identifier
11758 depends on the static tracepoint backend library your program is
11759 using. You can find all the marker identifiers in the @samp{ID} field
11760 of the @code{info static-tracepoint-markers} command output.
11761 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
11762 Markers}. For example, in the following small program using the UST
11768 trace_mark(ust, bar33, "str %s", "FOOBAZ");
11773 the marker id is composed of joining the first two arguments to the
11774 @code{trace_mark} call with a slash, which translates to:
11777 (@value{GDBP}) info static-tracepoint-markers
11778 Cnt Enb ID Address What
11779 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
11785 so you may probe the marker above with:
11788 (@value{GDBP}) strace -m ust/bar33
11791 Static tracepoints accept an extra collect action --- @code{collect
11792 $_sdata}. This collects arbitrary user data passed in the probe point
11793 call to the tracing library. In the UST example above, you'll see
11794 that the third argument to @code{trace_mark} is a printf-like format
11795 string. The user data is then the result of running that formating
11796 string against the following arguments. Note that @code{info
11797 static-tracepoint-markers} command output lists that format string in
11798 the @samp{Data:} field.
11800 You can inspect this data when analyzing the trace buffer, by printing
11801 the $_sdata variable like any other variable available to
11802 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
11805 @cindex last tracepoint number
11806 @cindex recent tracepoint number
11807 @cindex tracepoint number
11808 The convenience variable @code{$tpnum} records the tracepoint number
11809 of the most recently set tracepoint.
11811 @kindex delete tracepoint
11812 @cindex tracepoint deletion
11813 @item delete tracepoint @r{[}@var{num}@r{]}
11814 Permanently delete one or more tracepoints. With no argument, the
11815 default is to delete all tracepoints. Note that the regular
11816 @code{delete} command can remove tracepoints also.
11821 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
11823 (@value{GDBP}) @b{delete trace} // remove all tracepoints
11827 You can abbreviate this command as @code{del tr}.
11830 @node Enable and Disable Tracepoints
11831 @subsection Enable and Disable Tracepoints
11833 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
11836 @kindex disable tracepoint
11837 @item disable tracepoint @r{[}@var{num}@r{]}
11838 Disable tracepoint @var{num}, or all tracepoints if no argument
11839 @var{num} is given. A disabled tracepoint will have no effect during
11840 a trace experiment, but it is not forgotten. You can re-enable
11841 a disabled tracepoint using the @code{enable tracepoint} command.
11842 If the command is issued during a trace experiment and the debug target
11843 has support for disabling tracepoints during a trace experiment, then the
11844 change will be effective immediately. Otherwise, it will be applied to the
11845 next trace experiment.
11847 @kindex enable tracepoint
11848 @item enable tracepoint @r{[}@var{num}@r{]}
11849 Enable tracepoint @var{num}, or all tracepoints. If this command is
11850 issued during a trace experiment and the debug target supports enabling
11851 tracepoints during a trace experiment, then the enabled tracepoints will
11852 become effective immediately. Otherwise, they will become effective the
11853 next time a trace experiment is run.
11856 @node Tracepoint Passcounts
11857 @subsection Tracepoint Passcounts
11861 @cindex tracepoint pass count
11862 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
11863 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
11864 automatically stop a trace experiment. If a tracepoint's passcount is
11865 @var{n}, then the trace experiment will be automatically stopped on
11866 the @var{n}'th time that tracepoint is hit. If the tracepoint number
11867 @var{num} is not specified, the @code{passcount} command sets the
11868 passcount of the most recently defined tracepoint. If no passcount is
11869 given, the trace experiment will run until stopped explicitly by the
11875 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
11876 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
11878 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
11879 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
11880 (@value{GDBP}) @b{trace foo}
11881 (@value{GDBP}) @b{pass 3}
11882 (@value{GDBP}) @b{trace bar}
11883 (@value{GDBP}) @b{pass 2}
11884 (@value{GDBP}) @b{trace baz}
11885 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
11886 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
11887 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
11888 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
11892 @node Tracepoint Conditions
11893 @subsection Tracepoint Conditions
11894 @cindex conditional tracepoints
11895 @cindex tracepoint conditions
11897 The simplest sort of tracepoint collects data every time your program
11898 reaches a specified place. You can also specify a @dfn{condition} for
11899 a tracepoint. A condition is just a Boolean expression in your
11900 programming language (@pxref{Expressions, ,Expressions}). A
11901 tracepoint with a condition evaluates the expression each time your
11902 program reaches it, and data collection happens only if the condition
11905 Tracepoint conditions can be specified when a tracepoint is set, by
11906 using @samp{if} in the arguments to the @code{trace} command.
11907 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
11908 also be set or changed at any time with the @code{condition} command,
11909 just as with breakpoints.
11911 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
11912 the conditional expression itself. Instead, @value{GDBN} encodes the
11913 expression into an agent expression (@pxref{Agent Expressions})
11914 suitable for execution on the target, independently of @value{GDBN}.
11915 Global variables become raw memory locations, locals become stack
11916 accesses, and so forth.
11918 For instance, suppose you have a function that is usually called
11919 frequently, but should not be called after an error has occurred. You
11920 could use the following tracepoint command to collect data about calls
11921 of that function that happen while the error code is propagating
11922 through the program; an unconditional tracepoint could end up
11923 collecting thousands of useless trace frames that you would have to
11927 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
11930 @node Trace State Variables
11931 @subsection Trace State Variables
11932 @cindex trace state variables
11934 A @dfn{trace state variable} is a special type of variable that is
11935 created and managed by target-side code. The syntax is the same as
11936 that for GDB's convenience variables (a string prefixed with ``$''),
11937 but they are stored on the target. They must be created explicitly,
11938 using a @code{tvariable} command. They are always 64-bit signed
11941 Trace state variables are remembered by @value{GDBN}, and downloaded
11942 to the target along with tracepoint information when the trace
11943 experiment starts. There are no intrinsic limits on the number of
11944 trace state variables, beyond memory limitations of the target.
11946 @cindex convenience variables, and trace state variables
11947 Although trace state variables are managed by the target, you can use
11948 them in print commands and expressions as if they were convenience
11949 variables; @value{GDBN} will get the current value from the target
11950 while the trace experiment is running. Trace state variables share
11951 the same namespace as other ``$'' variables, which means that you
11952 cannot have trace state variables with names like @code{$23} or
11953 @code{$pc}, nor can you have a trace state variable and a convenience
11954 variable with the same name.
11958 @item tvariable $@var{name} [ = @var{expression} ]
11960 The @code{tvariable} command creates a new trace state variable named
11961 @code{$@var{name}}, and optionally gives it an initial value of
11962 @var{expression}. @var{expression} is evaluated when this command is
11963 entered; the result will be converted to an integer if possible,
11964 otherwise @value{GDBN} will report an error. A subsequent
11965 @code{tvariable} command specifying the same name does not create a
11966 variable, but instead assigns the supplied initial value to the
11967 existing variable of that name, overwriting any previous initial
11968 value. The default initial value is 0.
11970 @item info tvariables
11971 @kindex info tvariables
11972 List all the trace state variables along with their initial values.
11973 Their current values may also be displayed, if the trace experiment is
11976 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
11977 @kindex delete tvariable
11978 Delete the given trace state variables, or all of them if no arguments
11983 @node Tracepoint Actions
11984 @subsection Tracepoint Action Lists
11988 @cindex tracepoint actions
11989 @item actions @r{[}@var{num}@r{]}
11990 This command will prompt for a list of actions to be taken when the
11991 tracepoint is hit. If the tracepoint number @var{num} is not
11992 specified, this command sets the actions for the one that was most
11993 recently defined (so that you can define a tracepoint and then say
11994 @code{actions} without bothering about its number). You specify the
11995 actions themselves on the following lines, one action at a time, and
11996 terminate the actions list with a line containing just @code{end}. So
11997 far, the only defined actions are @code{collect}, @code{teval}, and
11998 @code{while-stepping}.
12000 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
12001 Commands, ,Breakpoint Command Lists}), except that only the defined
12002 actions are allowed; any other @value{GDBN} command is rejected.
12004 @cindex remove actions from a tracepoint
12005 To remove all actions from a tracepoint, type @samp{actions @var{num}}
12006 and follow it immediately with @samp{end}.
12009 (@value{GDBP}) @b{collect @var{data}} // collect some data
12011 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
12013 (@value{GDBP}) @b{end} // signals the end of actions.
12016 In the following example, the action list begins with @code{collect}
12017 commands indicating the things to be collected when the tracepoint is
12018 hit. Then, in order to single-step and collect additional data
12019 following the tracepoint, a @code{while-stepping} command is used,
12020 followed by the list of things to be collected after each step in a
12021 sequence of single steps. The @code{while-stepping} command is
12022 terminated by its own separate @code{end} command. Lastly, the action
12023 list is terminated by an @code{end} command.
12026 (@value{GDBP}) @b{trace foo}
12027 (@value{GDBP}) @b{actions}
12028 Enter actions for tracepoint 1, one per line:
12031 > while-stepping 12
12032 > collect $pc, arr[i]
12037 @kindex collect @r{(tracepoints)}
12038 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
12039 Collect values of the given expressions when the tracepoint is hit.
12040 This command accepts a comma-separated list of any valid expressions.
12041 In addition to global, static, or local variables, the following
12042 special arguments are supported:
12046 Collect all registers.
12049 Collect all function arguments.
12052 Collect all local variables.
12055 Collect the return address. This is helpful if you want to see more
12059 Collects the number of arguments from the static probe at which the
12060 tracepoint is located.
12061 @xref{Static Probe Points}.
12063 @item $_probe_arg@var{n}
12064 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
12065 from the static probe at which the tracepoint is located.
12066 @xref{Static Probe Points}.
12069 @vindex $_sdata@r{, collect}
12070 Collect static tracepoint marker specific data. Only available for
12071 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
12072 Lists}. On the UST static tracepoints library backend, an
12073 instrumentation point resembles a @code{printf} function call. The
12074 tracing library is able to collect user specified data formatted to a
12075 character string using the format provided by the programmer that
12076 instrumented the program. Other backends have similar mechanisms.
12077 Here's an example of a UST marker call:
12080 const char master_name[] = "$your_name";
12081 trace_mark(channel1, marker1, "hello %s", master_name)
12084 In this case, collecting @code{$_sdata} collects the string
12085 @samp{hello $yourname}. When analyzing the trace buffer, you can
12086 inspect @samp{$_sdata} like any other variable available to
12090 You can give several consecutive @code{collect} commands, each one
12091 with a single argument, or one @code{collect} command with several
12092 arguments separated by commas; the effect is the same.
12094 The optional @var{mods} changes the usual handling of the arguments.
12095 @code{s} requests that pointers to chars be handled as strings, in
12096 particular collecting the contents of the memory being pointed at, up
12097 to the first zero. The upper bound is by default the value of the
12098 @code{print elements} variable; if @code{s} is followed by a decimal
12099 number, that is the upper bound instead. So for instance
12100 @samp{collect/s25 mystr} collects as many as 25 characters at
12103 The command @code{info scope} (@pxref{Symbols, info scope}) is
12104 particularly useful for figuring out what data to collect.
12106 @kindex teval @r{(tracepoints)}
12107 @item teval @var{expr1}, @var{expr2}, @dots{}
12108 Evaluate the given expressions when the tracepoint is hit. This
12109 command accepts a comma-separated list of expressions. The results
12110 are discarded, so this is mainly useful for assigning values to trace
12111 state variables (@pxref{Trace State Variables}) without adding those
12112 values to the trace buffer, as would be the case if the @code{collect}
12115 @kindex while-stepping @r{(tracepoints)}
12116 @item while-stepping @var{n}
12117 Perform @var{n} single-step instruction traces after the tracepoint,
12118 collecting new data after each step. The @code{while-stepping}
12119 command is followed by the list of what to collect while stepping
12120 (followed by its own @code{end} command):
12123 > while-stepping 12
12124 > collect $regs, myglobal
12130 Note that @code{$pc} is not automatically collected by
12131 @code{while-stepping}; you need to explicitly collect that register if
12132 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
12135 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
12136 @kindex set default-collect
12137 @cindex default collection action
12138 This variable is a list of expressions to collect at each tracepoint
12139 hit. It is effectively an additional @code{collect} action prepended
12140 to every tracepoint action list. The expressions are parsed
12141 individually for each tracepoint, so for instance a variable named
12142 @code{xyz} may be interpreted as a global for one tracepoint, and a
12143 local for another, as appropriate to the tracepoint's location.
12145 @item show default-collect
12146 @kindex show default-collect
12147 Show the list of expressions that are collected by default at each
12152 @node Listing Tracepoints
12153 @subsection Listing Tracepoints
12156 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
12157 @kindex info tp @r{[}@var{n}@dots{}@r{]}
12158 @cindex information about tracepoints
12159 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
12160 Display information about the tracepoint @var{num}. If you don't
12161 specify a tracepoint number, displays information about all the
12162 tracepoints defined so far. The format is similar to that used for
12163 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
12164 command, simply restricting itself to tracepoints.
12166 A tracepoint's listing may include additional information specific to
12171 its passcount as given by the @code{passcount @var{n}} command
12174 the state about installed on target of each location
12178 (@value{GDBP}) @b{info trace}
12179 Num Type Disp Enb Address What
12180 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
12182 collect globfoo, $regs
12187 2 tracepoint keep y <MULTIPLE>
12189 2.1 y 0x0804859c in func4 at change-loc.h:35
12190 installed on target
12191 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
12192 installed on target
12193 2.3 y <PENDING> set_tracepoint
12194 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
12195 not installed on target
12200 This command can be abbreviated @code{info tp}.
12203 @node Listing Static Tracepoint Markers
12204 @subsection Listing Static Tracepoint Markers
12207 @kindex info static-tracepoint-markers
12208 @cindex information about static tracepoint markers
12209 @item info static-tracepoint-markers
12210 Display information about all static tracepoint markers defined in the
12213 For each marker, the following columns are printed:
12217 An incrementing counter, output to help readability. This is not a
12220 The marker ID, as reported by the target.
12221 @item Enabled or Disabled
12222 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
12223 that are not enabled.
12225 Where the marker is in your program, as a memory address.
12227 Where the marker is in the source for your program, as a file and line
12228 number. If the debug information included in the program does not
12229 allow @value{GDBN} to locate the source of the marker, this column
12230 will be left blank.
12234 In addition, the following information may be printed for each marker:
12238 User data passed to the tracing library by the marker call. In the
12239 UST backend, this is the format string passed as argument to the
12241 @item Static tracepoints probing the marker
12242 The list of static tracepoints attached to the marker.
12246 (@value{GDBP}) info static-tracepoint-markers
12247 Cnt ID Enb Address What
12248 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
12249 Data: number1 %d number2 %d
12250 Probed by static tracepoints: #2
12251 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
12257 @node Starting and Stopping Trace Experiments
12258 @subsection Starting and Stopping Trace Experiments
12261 @kindex tstart [ @var{notes} ]
12262 @cindex start a new trace experiment
12263 @cindex collected data discarded
12265 This command starts the trace experiment, and begins collecting data.
12266 It has the side effect of discarding all the data collected in the
12267 trace buffer during the previous trace experiment. If any arguments
12268 are supplied, they are taken as a note and stored with the trace
12269 experiment's state. The notes may be arbitrary text, and are
12270 especially useful with disconnected tracing in a multi-user context;
12271 the notes can explain what the trace is doing, supply user contact
12272 information, and so forth.
12274 @kindex tstop [ @var{notes} ]
12275 @cindex stop a running trace experiment
12277 This command stops the trace experiment. If any arguments are
12278 supplied, they are recorded with the experiment as a note. This is
12279 useful if you are stopping a trace started by someone else, for
12280 instance if the trace is interfering with the system's behavior and
12281 needs to be stopped quickly.
12283 @strong{Note}: a trace experiment and data collection may stop
12284 automatically if any tracepoint's passcount is reached
12285 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
12288 @cindex status of trace data collection
12289 @cindex trace experiment, status of
12291 This command displays the status of the current trace data
12295 Here is an example of the commands we described so far:
12298 (@value{GDBP}) @b{trace gdb_c_test}
12299 (@value{GDBP}) @b{actions}
12300 Enter actions for tracepoint #1, one per line.
12301 > collect $regs,$locals,$args
12302 > while-stepping 11
12306 (@value{GDBP}) @b{tstart}
12307 [time passes @dots{}]
12308 (@value{GDBP}) @b{tstop}
12311 @anchor{disconnected tracing}
12312 @cindex disconnected tracing
12313 You can choose to continue running the trace experiment even if
12314 @value{GDBN} disconnects from the target, voluntarily or
12315 involuntarily. For commands such as @code{detach}, the debugger will
12316 ask what you want to do with the trace. But for unexpected
12317 terminations (@value{GDBN} crash, network outage), it would be
12318 unfortunate to lose hard-won trace data, so the variable
12319 @code{disconnected-tracing} lets you decide whether the trace should
12320 continue running without @value{GDBN}.
12323 @item set disconnected-tracing on
12324 @itemx set disconnected-tracing off
12325 @kindex set disconnected-tracing
12326 Choose whether a tracing run should continue to run if @value{GDBN}
12327 has disconnected from the target. Note that @code{detach} or
12328 @code{quit} will ask you directly what to do about a running trace no
12329 matter what this variable's setting, so the variable is mainly useful
12330 for handling unexpected situations, such as loss of the network.
12332 @item show disconnected-tracing
12333 @kindex show disconnected-tracing
12334 Show the current choice for disconnected tracing.
12338 When you reconnect to the target, the trace experiment may or may not
12339 still be running; it might have filled the trace buffer in the
12340 meantime, or stopped for one of the other reasons. If it is running,
12341 it will continue after reconnection.
12343 Upon reconnection, the target will upload information about the
12344 tracepoints in effect. @value{GDBN} will then compare that
12345 information to the set of tracepoints currently defined, and attempt
12346 to match them up, allowing for the possibility that the numbers may
12347 have changed due to creation and deletion in the meantime. If one of
12348 the target's tracepoints does not match any in @value{GDBN}, the
12349 debugger will create a new tracepoint, so that you have a number with
12350 which to specify that tracepoint. This matching-up process is
12351 necessarily heuristic, and it may result in useless tracepoints being
12352 created; you may simply delete them if they are of no use.
12354 @cindex circular trace buffer
12355 If your target agent supports a @dfn{circular trace buffer}, then you
12356 can run a trace experiment indefinitely without filling the trace
12357 buffer; when space runs out, the agent deletes already-collected trace
12358 frames, oldest first, until there is enough room to continue
12359 collecting. This is especially useful if your tracepoints are being
12360 hit too often, and your trace gets terminated prematurely because the
12361 buffer is full. To ask for a circular trace buffer, simply set
12362 @samp{circular-trace-buffer} to on. You can set this at any time,
12363 including during tracing; if the agent can do it, it will change
12364 buffer handling on the fly, otherwise it will not take effect until
12368 @item set circular-trace-buffer on
12369 @itemx set circular-trace-buffer off
12370 @kindex set circular-trace-buffer
12371 Choose whether a tracing run should use a linear or circular buffer
12372 for trace data. A linear buffer will not lose any trace data, but may
12373 fill up prematurely, while a circular buffer will discard old trace
12374 data, but it will have always room for the latest tracepoint hits.
12376 @item show circular-trace-buffer
12377 @kindex show circular-trace-buffer
12378 Show the current choice for the trace buffer. Note that this may not
12379 match the agent's current buffer handling, nor is it guaranteed to
12380 match the setting that might have been in effect during a past run,
12381 for instance if you are looking at frames from a trace file.
12386 @item set trace-buffer-size @var{n}
12387 @itemx set trace-buffer-size unlimited
12388 @kindex set trace-buffer-size
12389 Request that the target use a trace buffer of @var{n} bytes. Not all
12390 targets will honor the request; they may have a compiled-in size for
12391 the trace buffer, or some other limitation. Set to a value of
12392 @code{unlimited} or @code{-1} to let the target use whatever size it
12393 likes. This is also the default.
12395 @item show trace-buffer-size
12396 @kindex show trace-buffer-size
12397 Show the current requested size for the trace buffer. Note that this
12398 will only match the actual size if the target supports size-setting,
12399 and was able to handle the requested size. For instance, if the
12400 target can only change buffer size between runs, this variable will
12401 not reflect the change until the next run starts. Use @code{tstatus}
12402 to get a report of the actual buffer size.
12406 @item set trace-user @var{text}
12407 @kindex set trace-user
12409 @item show trace-user
12410 @kindex show trace-user
12412 @item set trace-notes @var{text}
12413 @kindex set trace-notes
12414 Set the trace run's notes.
12416 @item show trace-notes
12417 @kindex show trace-notes
12418 Show the trace run's notes.
12420 @item set trace-stop-notes @var{text}
12421 @kindex set trace-stop-notes
12422 Set the trace run's stop notes. The handling of the note is as for
12423 @code{tstop} arguments; the set command is convenient way to fix a
12424 stop note that is mistaken or incomplete.
12426 @item show trace-stop-notes
12427 @kindex show trace-stop-notes
12428 Show the trace run's stop notes.
12432 @node Tracepoint Restrictions
12433 @subsection Tracepoint Restrictions
12435 @cindex tracepoint restrictions
12436 There are a number of restrictions on the use of tracepoints. As
12437 described above, tracepoint data gathering occurs on the target
12438 without interaction from @value{GDBN}. Thus the full capabilities of
12439 the debugger are not available during data gathering, and then at data
12440 examination time, you will be limited by only having what was
12441 collected. The following items describe some common problems, but it
12442 is not exhaustive, and you may run into additional difficulties not
12448 Tracepoint expressions are intended to gather objects (lvalues). Thus
12449 the full flexibility of GDB's expression evaluator is not available.
12450 You cannot call functions, cast objects to aggregate types, access
12451 convenience variables or modify values (except by assignment to trace
12452 state variables). Some language features may implicitly call
12453 functions (for instance Objective-C fields with accessors), and therefore
12454 cannot be collected either.
12457 Collection of local variables, either individually or in bulk with
12458 @code{$locals} or @code{$args}, during @code{while-stepping} may
12459 behave erratically. The stepping action may enter a new scope (for
12460 instance by stepping into a function), or the location of the variable
12461 may change (for instance it is loaded into a register). The
12462 tracepoint data recorded uses the location information for the
12463 variables that is correct for the tracepoint location. When the
12464 tracepoint is created, it is not possible, in general, to determine
12465 where the steps of a @code{while-stepping} sequence will advance the
12466 program---particularly if a conditional branch is stepped.
12469 Collection of an incompletely-initialized or partially-destroyed object
12470 may result in something that @value{GDBN} cannot display, or displays
12471 in a misleading way.
12474 When @value{GDBN} displays a pointer to character it automatically
12475 dereferences the pointer to also display characters of the string
12476 being pointed to. However, collecting the pointer during tracing does
12477 not automatically collect the string. You need to explicitly
12478 dereference the pointer and provide size information if you want to
12479 collect not only the pointer, but the memory pointed to. For example,
12480 @code{*ptr@@50} can be used to collect the 50 element array pointed to
12484 It is not possible to collect a complete stack backtrace at a
12485 tracepoint. Instead, you may collect the registers and a few hundred
12486 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
12487 (adjust to use the name of the actual stack pointer register on your
12488 target architecture, and the amount of stack you wish to capture).
12489 Then the @code{backtrace} command will show a partial backtrace when
12490 using a trace frame. The number of stack frames that can be examined
12491 depends on the sizes of the frames in the collected stack. Note that
12492 if you ask for a block so large that it goes past the bottom of the
12493 stack, the target agent may report an error trying to read from an
12497 If you do not collect registers at a tracepoint, @value{GDBN} can
12498 infer that the value of @code{$pc} must be the same as the address of
12499 the tracepoint and use that when you are looking at a trace frame
12500 for that tracepoint. However, this cannot work if the tracepoint has
12501 multiple locations (for instance if it was set in a function that was
12502 inlined), or if it has a @code{while-stepping} loop. In those cases
12503 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
12508 @node Analyze Collected Data
12509 @section Using the Collected Data
12511 After the tracepoint experiment ends, you use @value{GDBN} commands
12512 for examining the trace data. The basic idea is that each tracepoint
12513 collects a trace @dfn{snapshot} every time it is hit and another
12514 snapshot every time it single-steps. All these snapshots are
12515 consecutively numbered from zero and go into a buffer, and you can
12516 examine them later. The way you examine them is to @dfn{focus} on a
12517 specific trace snapshot. When the remote stub is focused on a trace
12518 snapshot, it will respond to all @value{GDBN} requests for memory and
12519 registers by reading from the buffer which belongs to that snapshot,
12520 rather than from @emph{real} memory or registers of the program being
12521 debugged. This means that @strong{all} @value{GDBN} commands
12522 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
12523 behave as if we were currently debugging the program state as it was
12524 when the tracepoint occurred. Any requests for data that are not in
12525 the buffer will fail.
12528 * tfind:: How to select a trace snapshot
12529 * tdump:: How to display all data for a snapshot
12530 * save tracepoints:: How to save tracepoints for a future run
12534 @subsection @code{tfind @var{n}}
12537 @cindex select trace snapshot
12538 @cindex find trace snapshot
12539 The basic command for selecting a trace snapshot from the buffer is
12540 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
12541 counting from zero. If no argument @var{n} is given, the next
12542 snapshot is selected.
12544 Here are the various forms of using the @code{tfind} command.
12548 Find the first snapshot in the buffer. This is a synonym for
12549 @code{tfind 0} (since 0 is the number of the first snapshot).
12552 Stop debugging trace snapshots, resume @emph{live} debugging.
12555 Same as @samp{tfind none}.
12558 No argument means find the next trace snapshot.
12561 Find the previous trace snapshot before the current one. This permits
12562 retracing earlier steps.
12564 @item tfind tracepoint @var{num}
12565 Find the next snapshot associated with tracepoint @var{num}. Search
12566 proceeds forward from the last examined trace snapshot. If no
12567 argument @var{num} is given, it means find the next snapshot collected
12568 for the same tracepoint as the current snapshot.
12570 @item tfind pc @var{addr}
12571 Find the next snapshot associated with the value @var{addr} of the
12572 program counter. Search proceeds forward from the last examined trace
12573 snapshot. If no argument @var{addr} is given, it means find the next
12574 snapshot with the same value of PC as the current snapshot.
12576 @item tfind outside @var{addr1}, @var{addr2}
12577 Find the next snapshot whose PC is outside the given range of
12578 addresses (exclusive).
12580 @item tfind range @var{addr1}, @var{addr2}
12581 Find the next snapshot whose PC is between @var{addr1} and
12582 @var{addr2} (inclusive).
12584 @item tfind line @r{[}@var{file}:@r{]}@var{n}
12585 Find the next snapshot associated with the source line @var{n}. If
12586 the optional argument @var{file} is given, refer to line @var{n} in
12587 that source file. Search proceeds forward from the last examined
12588 trace snapshot. If no argument @var{n} is given, it means find the
12589 next line other than the one currently being examined; thus saying
12590 @code{tfind line} repeatedly can appear to have the same effect as
12591 stepping from line to line in a @emph{live} debugging session.
12594 The default arguments for the @code{tfind} commands are specifically
12595 designed to make it easy to scan through the trace buffer. For
12596 instance, @code{tfind} with no argument selects the next trace
12597 snapshot, and @code{tfind -} with no argument selects the previous
12598 trace snapshot. So, by giving one @code{tfind} command, and then
12599 simply hitting @key{RET} repeatedly you can examine all the trace
12600 snapshots in order. Or, by saying @code{tfind -} and then hitting
12601 @key{RET} repeatedly you can examine the snapshots in reverse order.
12602 The @code{tfind line} command with no argument selects the snapshot
12603 for the next source line executed. The @code{tfind pc} command with
12604 no argument selects the next snapshot with the same program counter
12605 (PC) as the current frame. The @code{tfind tracepoint} command with
12606 no argument selects the next trace snapshot collected by the same
12607 tracepoint as the current one.
12609 In addition to letting you scan through the trace buffer manually,
12610 these commands make it easy to construct @value{GDBN} scripts that
12611 scan through the trace buffer and print out whatever collected data
12612 you are interested in. Thus, if we want to examine the PC, FP, and SP
12613 registers from each trace frame in the buffer, we can say this:
12616 (@value{GDBP}) @b{tfind start}
12617 (@value{GDBP}) @b{while ($trace_frame != -1)}
12618 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
12619 $trace_frame, $pc, $sp, $fp
12623 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
12624 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
12625 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
12626 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
12627 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
12628 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
12629 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
12630 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
12631 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
12632 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
12633 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
12636 Or, if we want to examine the variable @code{X} at each source line in
12640 (@value{GDBP}) @b{tfind start}
12641 (@value{GDBP}) @b{while ($trace_frame != -1)}
12642 > printf "Frame %d, X == %d\n", $trace_frame, X
12652 @subsection @code{tdump}
12654 @cindex dump all data collected at tracepoint
12655 @cindex tracepoint data, display
12657 This command takes no arguments. It prints all the data collected at
12658 the current trace snapshot.
12661 (@value{GDBP}) @b{trace 444}
12662 (@value{GDBP}) @b{actions}
12663 Enter actions for tracepoint #2, one per line:
12664 > collect $regs, $locals, $args, gdb_long_test
12667 (@value{GDBP}) @b{tstart}
12669 (@value{GDBP}) @b{tfind line 444}
12670 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
12672 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
12674 (@value{GDBP}) @b{tdump}
12675 Data collected at tracepoint 2, trace frame 1:
12676 d0 0xc4aa0085 -995491707
12680 d4 0x71aea3d 119204413
12683 d7 0x380035 3670069
12684 a0 0x19e24a 1696330
12685 a1 0x3000668 50333288
12687 a3 0x322000 3284992
12688 a4 0x3000698 50333336
12689 a5 0x1ad3cc 1758156
12690 fp 0x30bf3c 0x30bf3c
12691 sp 0x30bf34 0x30bf34
12693 pc 0x20b2c8 0x20b2c8
12697 p = 0x20e5b4 "gdb-test"
12704 gdb_long_test = 17 '\021'
12709 @code{tdump} works by scanning the tracepoint's current collection
12710 actions and printing the value of each expression listed. So
12711 @code{tdump} can fail, if after a run, you change the tracepoint's
12712 actions to mention variables that were not collected during the run.
12714 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
12715 uses the collected value of @code{$pc} to distinguish between trace
12716 frames that were collected at the tracepoint hit, and frames that were
12717 collected while stepping. This allows it to correctly choose whether
12718 to display the basic list of collections, or the collections from the
12719 body of the while-stepping loop. However, if @code{$pc} was not collected,
12720 then @code{tdump} will always attempt to dump using the basic collection
12721 list, and may fail if a while-stepping frame does not include all the
12722 same data that is collected at the tracepoint hit.
12723 @c This is getting pretty arcane, example would be good.
12725 @node save tracepoints
12726 @subsection @code{save tracepoints @var{filename}}
12727 @kindex save tracepoints
12728 @kindex save-tracepoints
12729 @cindex save tracepoints for future sessions
12731 This command saves all current tracepoint definitions together with
12732 their actions and passcounts, into a file @file{@var{filename}}
12733 suitable for use in a later debugging session. To read the saved
12734 tracepoint definitions, use the @code{source} command (@pxref{Command
12735 Files}). The @w{@code{save-tracepoints}} command is a deprecated
12736 alias for @w{@code{save tracepoints}}
12738 @node Tracepoint Variables
12739 @section Convenience Variables for Tracepoints
12740 @cindex tracepoint variables
12741 @cindex convenience variables for tracepoints
12744 @vindex $trace_frame
12745 @item (int) $trace_frame
12746 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
12747 snapshot is selected.
12749 @vindex $tracepoint
12750 @item (int) $tracepoint
12751 The tracepoint for the current trace snapshot.
12753 @vindex $trace_line
12754 @item (int) $trace_line
12755 The line number for the current trace snapshot.
12757 @vindex $trace_file
12758 @item (char []) $trace_file
12759 The source file for the current trace snapshot.
12761 @vindex $trace_func
12762 @item (char []) $trace_func
12763 The name of the function containing @code{$tracepoint}.
12766 Note: @code{$trace_file} is not suitable for use in @code{printf},
12767 use @code{output} instead.
12769 Here's a simple example of using these convenience variables for
12770 stepping through all the trace snapshots and printing some of their
12771 data. Note that these are not the same as trace state variables,
12772 which are managed by the target.
12775 (@value{GDBP}) @b{tfind start}
12777 (@value{GDBP}) @b{while $trace_frame != -1}
12778 > output $trace_file
12779 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
12785 @section Using Trace Files
12786 @cindex trace files
12788 In some situations, the target running a trace experiment may no
12789 longer be available; perhaps it crashed, or the hardware was needed
12790 for a different activity. To handle these cases, you can arrange to
12791 dump the trace data into a file, and later use that file as a source
12792 of trace data, via the @code{target tfile} command.
12797 @item tsave [ -r ] @var{filename}
12798 @itemx tsave [-ctf] @var{dirname}
12799 Save the trace data to @var{filename}. By default, this command
12800 assumes that @var{filename} refers to the host filesystem, so if
12801 necessary @value{GDBN} will copy raw trace data up from the target and
12802 then save it. If the target supports it, you can also supply the
12803 optional argument @code{-r} (``remote'') to direct the target to save
12804 the data directly into @var{filename} in its own filesystem, which may be
12805 more efficient if the trace buffer is very large. (Note, however, that
12806 @code{target tfile} can only read from files accessible to the host.)
12807 By default, this command will save trace frame in tfile format.
12808 You can supply the optional argument @code{-ctf} to save date in CTF
12809 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
12810 that can be shared by multiple debugging and tracing tools. Please go to
12811 @indicateurl{http://www.efficios.com/ctf} to get more information.
12813 @kindex target tfile
12817 @item target tfile @var{filename}
12818 @itemx target ctf @var{dirname}
12819 Use the file named @var{filename} or directory named @var{dirname} as
12820 a source of trace data. Commands that examine data work as they do with
12821 a live target, but it is not possible to run any new trace experiments.
12822 @code{tstatus} will report the state of the trace run at the moment
12823 the data was saved, as well as the current trace frame you are examining.
12824 @var{filename} or @var{dirname} must be on a filesystem accessible to
12828 (@value{GDBP}) target ctf ctf.ctf
12829 (@value{GDBP}) tfind
12830 Found trace frame 0, tracepoint 2
12831 39 ++a; /* set tracepoint 1 here */
12832 (@value{GDBP}) tdump
12833 Data collected at tracepoint 2, trace frame 0:
12837 c = @{"123", "456", "789", "123", "456", "789"@}
12838 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
12846 @chapter Debugging Programs That Use Overlays
12849 If your program is too large to fit completely in your target system's
12850 memory, you can sometimes use @dfn{overlays} to work around this
12851 problem. @value{GDBN} provides some support for debugging programs that
12855 * How Overlays Work:: A general explanation of overlays.
12856 * Overlay Commands:: Managing overlays in @value{GDBN}.
12857 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
12858 mapped by asking the inferior.
12859 * Overlay Sample Program:: A sample program using overlays.
12862 @node How Overlays Work
12863 @section How Overlays Work
12864 @cindex mapped overlays
12865 @cindex unmapped overlays
12866 @cindex load address, overlay's
12867 @cindex mapped address
12868 @cindex overlay area
12870 Suppose you have a computer whose instruction address space is only 64
12871 kilobytes long, but which has much more memory which can be accessed by
12872 other means: special instructions, segment registers, or memory
12873 management hardware, for example. Suppose further that you want to
12874 adapt a program which is larger than 64 kilobytes to run on this system.
12876 One solution is to identify modules of your program which are relatively
12877 independent, and need not call each other directly; call these modules
12878 @dfn{overlays}. Separate the overlays from the main program, and place
12879 their machine code in the larger memory. Place your main program in
12880 instruction memory, but leave at least enough space there to hold the
12881 largest overlay as well.
12883 Now, to call a function located in an overlay, you must first copy that
12884 overlay's machine code from the large memory into the space set aside
12885 for it in the instruction memory, and then jump to its entry point
12888 @c NB: In the below the mapped area's size is greater or equal to the
12889 @c size of all overlays. This is intentional to remind the developer
12890 @c that overlays don't necessarily need to be the same size.
12894 Data Instruction Larger
12895 Address Space Address Space Address Space
12896 +-----------+ +-----------+ +-----------+
12898 +-----------+ +-----------+ +-----------+<-- overlay 1
12899 | program | | main | .----| overlay 1 | load address
12900 | variables | | program | | +-----------+
12901 | and heap | | | | | |
12902 +-----------+ | | | +-----------+<-- overlay 2
12903 | | +-----------+ | | | load address
12904 +-----------+ | | | .-| overlay 2 |
12906 mapped --->+-----------+ | | +-----------+
12907 address | | | | | |
12908 | overlay | <-' | | |
12909 | area | <---' +-----------+<-- overlay 3
12910 | | <---. | | load address
12911 +-----------+ `--| overlay 3 |
12918 @anchor{A code overlay}A code overlay
12922 The diagram (@pxref{A code overlay}) shows a system with separate data
12923 and instruction address spaces. To map an overlay, the program copies
12924 its code from the larger address space to the instruction address space.
12925 Since the overlays shown here all use the same mapped address, only one
12926 may be mapped at a time. For a system with a single address space for
12927 data and instructions, the diagram would be similar, except that the
12928 program variables and heap would share an address space with the main
12929 program and the overlay area.
12931 An overlay loaded into instruction memory and ready for use is called a
12932 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
12933 instruction memory. An overlay not present (or only partially present)
12934 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
12935 is its address in the larger memory. The mapped address is also called
12936 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
12937 called the @dfn{load memory address}, or @dfn{LMA}.
12939 Unfortunately, overlays are not a completely transparent way to adapt a
12940 program to limited instruction memory. They introduce a new set of
12941 global constraints you must keep in mind as you design your program:
12946 Before calling or returning to a function in an overlay, your program
12947 must make sure that overlay is actually mapped. Otherwise, the call or
12948 return will transfer control to the right address, but in the wrong
12949 overlay, and your program will probably crash.
12952 If the process of mapping an overlay is expensive on your system, you
12953 will need to choose your overlays carefully to minimize their effect on
12954 your program's performance.
12957 The executable file you load onto your system must contain each
12958 overlay's instructions, appearing at the overlay's load address, not its
12959 mapped address. However, each overlay's instructions must be relocated
12960 and its symbols defined as if the overlay were at its mapped address.
12961 You can use GNU linker scripts to specify different load and relocation
12962 addresses for pieces of your program; see @ref{Overlay Description,,,
12963 ld.info, Using ld: the GNU linker}.
12966 The procedure for loading executable files onto your system must be able
12967 to load their contents into the larger address space as well as the
12968 instruction and data spaces.
12972 The overlay system described above is rather simple, and could be
12973 improved in many ways:
12978 If your system has suitable bank switch registers or memory management
12979 hardware, you could use those facilities to make an overlay's load area
12980 contents simply appear at their mapped address in instruction space.
12981 This would probably be faster than copying the overlay to its mapped
12982 area in the usual way.
12985 If your overlays are small enough, you could set aside more than one
12986 overlay area, and have more than one overlay mapped at a time.
12989 You can use overlays to manage data, as well as instructions. In
12990 general, data overlays are even less transparent to your design than
12991 code overlays: whereas code overlays only require care when you call or
12992 return to functions, data overlays require care every time you access
12993 the data. Also, if you change the contents of a data overlay, you
12994 must copy its contents back out to its load address before you can copy a
12995 different data overlay into the same mapped area.
13000 @node Overlay Commands
13001 @section Overlay Commands
13003 To use @value{GDBN}'s overlay support, each overlay in your program must
13004 correspond to a separate section of the executable file. The section's
13005 virtual memory address and load memory address must be the overlay's
13006 mapped and load addresses. Identifying overlays with sections allows
13007 @value{GDBN} to determine the appropriate address of a function or
13008 variable, depending on whether the overlay is mapped or not.
13010 @value{GDBN}'s overlay commands all start with the word @code{overlay};
13011 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
13016 Disable @value{GDBN}'s overlay support. When overlay support is
13017 disabled, @value{GDBN} assumes that all functions and variables are
13018 always present at their mapped addresses. By default, @value{GDBN}'s
13019 overlay support is disabled.
13021 @item overlay manual
13022 @cindex manual overlay debugging
13023 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
13024 relies on you to tell it which overlays are mapped, and which are not,
13025 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
13026 commands described below.
13028 @item overlay map-overlay @var{overlay}
13029 @itemx overlay map @var{overlay}
13030 @cindex map an overlay
13031 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
13032 be the name of the object file section containing the overlay. When an
13033 overlay is mapped, @value{GDBN} assumes it can find the overlay's
13034 functions and variables at their mapped addresses. @value{GDBN} assumes
13035 that any other overlays whose mapped ranges overlap that of
13036 @var{overlay} are now unmapped.
13038 @item overlay unmap-overlay @var{overlay}
13039 @itemx overlay unmap @var{overlay}
13040 @cindex unmap an overlay
13041 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
13042 must be the name of the object file section containing the overlay.
13043 When an overlay is unmapped, @value{GDBN} assumes it can find the
13044 overlay's functions and variables at their load addresses.
13047 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
13048 consults a data structure the overlay manager maintains in the inferior
13049 to see which overlays are mapped. For details, see @ref{Automatic
13050 Overlay Debugging}.
13052 @item overlay load-target
13053 @itemx overlay load
13054 @cindex reloading the overlay table
13055 Re-read the overlay table from the inferior. Normally, @value{GDBN}
13056 re-reads the table @value{GDBN} automatically each time the inferior
13057 stops, so this command should only be necessary if you have changed the
13058 overlay mapping yourself using @value{GDBN}. This command is only
13059 useful when using automatic overlay debugging.
13061 @item overlay list-overlays
13062 @itemx overlay list
13063 @cindex listing mapped overlays
13064 Display a list of the overlays currently mapped, along with their mapped
13065 addresses, load addresses, and sizes.
13069 Normally, when @value{GDBN} prints a code address, it includes the name
13070 of the function the address falls in:
13073 (@value{GDBP}) print main
13074 $3 = @{int ()@} 0x11a0 <main>
13077 When overlay debugging is enabled, @value{GDBN} recognizes code in
13078 unmapped overlays, and prints the names of unmapped functions with
13079 asterisks around them. For example, if @code{foo} is a function in an
13080 unmapped overlay, @value{GDBN} prints it this way:
13083 (@value{GDBP}) overlay list
13084 No sections are mapped.
13085 (@value{GDBP}) print foo
13086 $5 = @{int (int)@} 0x100000 <*foo*>
13089 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
13093 (@value{GDBP}) overlay list
13094 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
13095 mapped at 0x1016 - 0x104a
13096 (@value{GDBP}) print foo
13097 $6 = @{int (int)@} 0x1016 <foo>
13100 When overlay debugging is enabled, @value{GDBN} can find the correct
13101 address for functions and variables in an overlay, whether or not the
13102 overlay is mapped. This allows most @value{GDBN} commands, like
13103 @code{break} and @code{disassemble}, to work normally, even on unmapped
13104 code. However, @value{GDBN}'s breakpoint support has some limitations:
13108 @cindex breakpoints in overlays
13109 @cindex overlays, setting breakpoints in
13110 You can set breakpoints in functions in unmapped overlays, as long as
13111 @value{GDBN} can write to the overlay at its load address.
13113 @value{GDBN} can not set hardware or simulator-based breakpoints in
13114 unmapped overlays. However, if you set a breakpoint at the end of your
13115 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
13116 you are using manual overlay management), @value{GDBN} will re-set its
13117 breakpoints properly.
13121 @node Automatic Overlay Debugging
13122 @section Automatic Overlay Debugging
13123 @cindex automatic overlay debugging
13125 @value{GDBN} can automatically track which overlays are mapped and which
13126 are not, given some simple co-operation from the overlay manager in the
13127 inferior. If you enable automatic overlay debugging with the
13128 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
13129 looks in the inferior's memory for certain variables describing the
13130 current state of the overlays.
13132 Here are the variables your overlay manager must define to support
13133 @value{GDBN}'s automatic overlay debugging:
13137 @item @code{_ovly_table}:
13138 This variable must be an array of the following structures:
13143 /* The overlay's mapped address. */
13146 /* The size of the overlay, in bytes. */
13147 unsigned long size;
13149 /* The overlay's load address. */
13152 /* Non-zero if the overlay is currently mapped;
13154 unsigned long mapped;
13158 @item @code{_novlys}:
13159 This variable must be a four-byte signed integer, holding the total
13160 number of elements in @code{_ovly_table}.
13164 To decide whether a particular overlay is mapped or not, @value{GDBN}
13165 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
13166 @code{lma} members equal the VMA and LMA of the overlay's section in the
13167 executable file. When @value{GDBN} finds a matching entry, it consults
13168 the entry's @code{mapped} member to determine whether the overlay is
13171 In addition, your overlay manager may define a function called
13172 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
13173 will silently set a breakpoint there. If the overlay manager then
13174 calls this function whenever it has changed the overlay table, this
13175 will enable @value{GDBN} to accurately keep track of which overlays
13176 are in program memory, and update any breakpoints that may be set
13177 in overlays. This will allow breakpoints to work even if the
13178 overlays are kept in ROM or other non-writable memory while they
13179 are not being executed.
13181 @node Overlay Sample Program
13182 @section Overlay Sample Program
13183 @cindex overlay example program
13185 When linking a program which uses overlays, you must place the overlays
13186 at their load addresses, while relocating them to run at their mapped
13187 addresses. To do this, you must write a linker script (@pxref{Overlay
13188 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
13189 since linker scripts are specific to a particular host system, target
13190 architecture, and target memory layout, this manual cannot provide
13191 portable sample code demonstrating @value{GDBN}'s overlay support.
13193 However, the @value{GDBN} source distribution does contain an overlaid
13194 program, with linker scripts for a few systems, as part of its test
13195 suite. The program consists of the following files from
13196 @file{gdb/testsuite/gdb.base}:
13200 The main program file.
13202 A simple overlay manager, used by @file{overlays.c}.
13207 Overlay modules, loaded and used by @file{overlays.c}.
13210 Linker scripts for linking the test program on the @code{d10v-elf}
13211 and @code{m32r-elf} targets.
13214 You can build the test program using the @code{d10v-elf} GCC
13215 cross-compiler like this:
13218 $ d10v-elf-gcc -g -c overlays.c
13219 $ d10v-elf-gcc -g -c ovlymgr.c
13220 $ d10v-elf-gcc -g -c foo.c
13221 $ d10v-elf-gcc -g -c bar.c
13222 $ d10v-elf-gcc -g -c baz.c
13223 $ d10v-elf-gcc -g -c grbx.c
13224 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
13225 baz.o grbx.o -Wl,-Td10v.ld -o overlays
13228 The build process is identical for any other architecture, except that
13229 you must substitute the appropriate compiler and linker script for the
13230 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
13234 @chapter Using @value{GDBN} with Different Languages
13237 Although programming languages generally have common aspects, they are
13238 rarely expressed in the same manner. For instance, in ANSI C,
13239 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
13240 Modula-2, it is accomplished by @code{p^}. Values can also be
13241 represented (and displayed) differently. Hex numbers in C appear as
13242 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
13244 @cindex working language
13245 Language-specific information is built into @value{GDBN} for some languages,
13246 allowing you to express operations like the above in your program's
13247 native language, and allowing @value{GDBN} to output values in a manner
13248 consistent with the syntax of your program's native language. The
13249 language you use to build expressions is called the @dfn{working
13253 * Setting:: Switching between source languages
13254 * Show:: Displaying the language
13255 * Checks:: Type and range checks
13256 * Supported Languages:: Supported languages
13257 * Unsupported Languages:: Unsupported languages
13261 @section Switching Between Source Languages
13263 There are two ways to control the working language---either have @value{GDBN}
13264 set it automatically, or select it manually yourself. You can use the
13265 @code{set language} command for either purpose. On startup, @value{GDBN}
13266 defaults to setting the language automatically. The working language is
13267 used to determine how expressions you type are interpreted, how values
13270 In addition to the working language, every source file that
13271 @value{GDBN} knows about has its own working language. For some object
13272 file formats, the compiler might indicate which language a particular
13273 source file is in. However, most of the time @value{GDBN} infers the
13274 language from the name of the file. The language of a source file
13275 controls whether C@t{++} names are demangled---this way @code{backtrace} can
13276 show each frame appropriately for its own language. There is no way to
13277 set the language of a source file from within @value{GDBN}, but you can
13278 set the language associated with a filename extension. @xref{Show, ,
13279 Displaying the Language}.
13281 This is most commonly a problem when you use a program, such
13282 as @code{cfront} or @code{f2c}, that generates C but is written in
13283 another language. In that case, make the
13284 program use @code{#line} directives in its C output; that way
13285 @value{GDBN} will know the correct language of the source code of the original
13286 program, and will display that source code, not the generated C code.
13289 * Filenames:: Filename extensions and languages.
13290 * Manually:: Setting the working language manually
13291 * Automatically:: Having @value{GDBN} infer the source language
13295 @subsection List of Filename Extensions and Languages
13297 If a source file name ends in one of the following extensions, then
13298 @value{GDBN} infers that its language is the one indicated.
13316 C@t{++} source file
13322 Objective-C source file
13326 Fortran source file
13329 Modula-2 source file
13333 Assembler source file. This actually behaves almost like C, but
13334 @value{GDBN} does not skip over function prologues when stepping.
13337 In addition, you may set the language associated with a filename
13338 extension. @xref{Show, , Displaying the Language}.
13341 @subsection Setting the Working Language
13343 If you allow @value{GDBN} to set the language automatically,
13344 expressions are interpreted the same way in your debugging session and
13347 @kindex set language
13348 If you wish, you may set the language manually. To do this, issue the
13349 command @samp{set language @var{lang}}, where @var{lang} is the name of
13350 a language, such as
13351 @code{c} or @code{modula-2}.
13352 For a list of the supported languages, type @samp{set language}.
13354 Setting the language manually prevents @value{GDBN} from updating the working
13355 language automatically. This can lead to confusion if you try
13356 to debug a program when the working language is not the same as the
13357 source language, when an expression is acceptable to both
13358 languages---but means different things. For instance, if the current
13359 source file were written in C, and @value{GDBN} was parsing Modula-2, a
13367 might not have the effect you intended. In C, this means to add
13368 @code{b} and @code{c} and place the result in @code{a}. The result
13369 printed would be the value of @code{a}. In Modula-2, this means to compare
13370 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
13372 @node Automatically
13373 @subsection Having @value{GDBN} Infer the Source Language
13375 To have @value{GDBN} set the working language automatically, use
13376 @samp{set language local} or @samp{set language auto}. @value{GDBN}
13377 then infers the working language. That is, when your program stops in a
13378 frame (usually by encountering a breakpoint), @value{GDBN} sets the
13379 working language to the language recorded for the function in that
13380 frame. If the language for a frame is unknown (that is, if the function
13381 or block corresponding to the frame was defined in a source file that
13382 does not have a recognized extension), the current working language is
13383 not changed, and @value{GDBN} issues a warning.
13385 This may not seem necessary for most programs, which are written
13386 entirely in one source language. However, program modules and libraries
13387 written in one source language can be used by a main program written in
13388 a different source language. Using @samp{set language auto} in this
13389 case frees you from having to set the working language manually.
13392 @section Displaying the Language
13394 The following commands help you find out which language is the
13395 working language, and also what language source files were written in.
13398 @item show language
13399 @anchor{show language}
13400 @kindex show language
13401 Display the current working language. This is the
13402 language you can use with commands such as @code{print} to
13403 build and compute expressions that may involve variables in your program.
13406 @kindex info frame@r{, show the source language}
13407 Display the source language for this frame. This language becomes the
13408 working language if you use an identifier from this frame.
13409 @xref{Frame Info, ,Information about a Frame}, to identify the other
13410 information listed here.
13413 @kindex info source@r{, show the source language}
13414 Display the source language of this source file.
13415 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
13416 information listed here.
13419 In unusual circumstances, you may have source files with extensions
13420 not in the standard list. You can then set the extension associated
13421 with a language explicitly:
13424 @item set extension-language @var{ext} @var{language}
13425 @kindex set extension-language
13426 Tell @value{GDBN} that source files with extension @var{ext} are to be
13427 assumed as written in the source language @var{language}.
13429 @item info extensions
13430 @kindex info extensions
13431 List all the filename extensions and the associated languages.
13435 @section Type and Range Checking
13437 Some languages are designed to guard you against making seemingly common
13438 errors through a series of compile- and run-time checks. These include
13439 checking the type of arguments to functions and operators and making
13440 sure mathematical overflows are caught at run time. Checks such as
13441 these help to ensure a program's correctness once it has been compiled
13442 by eliminating type mismatches and providing active checks for range
13443 errors when your program is running.
13445 By default @value{GDBN} checks for these errors according to the
13446 rules of the current source language. Although @value{GDBN} does not check
13447 the statements in your program, it can check expressions entered directly
13448 into @value{GDBN} for evaluation via the @code{print} command, for example.
13451 * Type Checking:: An overview of type checking
13452 * Range Checking:: An overview of range checking
13455 @cindex type checking
13456 @cindex checks, type
13457 @node Type Checking
13458 @subsection An Overview of Type Checking
13460 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
13461 arguments to operators and functions have to be of the correct type,
13462 otherwise an error occurs. These checks prevent type mismatch
13463 errors from ever causing any run-time problems. For example,
13466 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
13468 (@value{GDBP}) print obj.my_method (0)
13471 (@value{GDBP}) print obj.my_method (0x1234)
13472 Cannot resolve method klass::my_method to any overloaded instance
13475 The second example fails because in C@t{++} the integer constant
13476 @samp{0x1234} is not type-compatible with the pointer parameter type.
13478 For the expressions you use in @value{GDBN} commands, you can tell
13479 @value{GDBN} to not enforce strict type checking or
13480 to treat any mismatches as errors and abandon the expression;
13481 When type checking is disabled, @value{GDBN} successfully evaluates
13482 expressions like the second example above.
13484 Even if type checking is off, there may be other reasons
13485 related to type that prevent @value{GDBN} from evaluating an expression.
13486 For instance, @value{GDBN} does not know how to add an @code{int} and
13487 a @code{struct foo}. These particular type errors have nothing to do
13488 with the language in use and usually arise from expressions which make
13489 little sense to evaluate anyway.
13491 @value{GDBN} provides some additional commands for controlling type checking:
13493 @kindex set check type
13494 @kindex show check type
13496 @item set check type on
13497 @itemx set check type off
13498 Set strict type checking on or off. If any type mismatches occur in
13499 evaluating an expression while type checking is on, @value{GDBN} prints a
13500 message and aborts evaluation of the expression.
13502 @item show check type
13503 Show the current setting of type checking and whether @value{GDBN}
13504 is enforcing strict type checking rules.
13507 @cindex range checking
13508 @cindex checks, range
13509 @node Range Checking
13510 @subsection An Overview of Range Checking
13512 In some languages (such as Modula-2), it is an error to exceed the
13513 bounds of a type; this is enforced with run-time checks. Such range
13514 checking is meant to ensure program correctness by making sure
13515 computations do not overflow, or indices on an array element access do
13516 not exceed the bounds of the array.
13518 For expressions you use in @value{GDBN} commands, you can tell
13519 @value{GDBN} to treat range errors in one of three ways: ignore them,
13520 always treat them as errors and abandon the expression, or issue
13521 warnings but evaluate the expression anyway.
13523 A range error can result from numerical overflow, from exceeding an
13524 array index bound, or when you type a constant that is not a member
13525 of any type. Some languages, however, do not treat overflows as an
13526 error. In many implementations of C, mathematical overflow causes the
13527 result to ``wrap around'' to lower values---for example, if @var{m} is
13528 the largest integer value, and @var{s} is the smallest, then
13531 @var{m} + 1 @result{} @var{s}
13534 This, too, is specific to individual languages, and in some cases
13535 specific to individual compilers or machines. @xref{Supported Languages, ,
13536 Supported Languages}, for further details on specific languages.
13538 @value{GDBN} provides some additional commands for controlling the range checker:
13540 @kindex set check range
13541 @kindex show check range
13543 @item set check range auto
13544 Set range checking on or off based on the current working language.
13545 @xref{Supported Languages, ,Supported Languages}, for the default settings for
13548 @item set check range on
13549 @itemx set check range off
13550 Set range checking on or off, overriding the default setting for the
13551 current working language. A warning is issued if the setting does not
13552 match the language default. If a range error occurs and range checking is on,
13553 then a message is printed and evaluation of the expression is aborted.
13555 @item set check range warn
13556 Output messages when the @value{GDBN} range checker detects a range error,
13557 but attempt to evaluate the expression anyway. Evaluating the
13558 expression may still be impossible for other reasons, such as accessing
13559 memory that the process does not own (a typical example from many Unix
13563 Show the current setting of the range checker, and whether or not it is
13564 being set automatically by @value{GDBN}.
13567 @node Supported Languages
13568 @section Supported Languages
13570 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
13571 OpenCL C, Pascal, assembly, Modula-2, and Ada.
13572 @c This is false ...
13573 Some @value{GDBN} features may be used in expressions regardless of the
13574 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
13575 and the @samp{@{type@}addr} construct (@pxref{Expressions,
13576 ,Expressions}) can be used with the constructs of any supported
13579 The following sections detail to what degree each source language is
13580 supported by @value{GDBN}. These sections are not meant to be language
13581 tutorials or references, but serve only as a reference guide to what the
13582 @value{GDBN} expression parser accepts, and what input and output
13583 formats should look like for different languages. There are many good
13584 books written on each of these languages; please look to these for a
13585 language reference or tutorial.
13588 * C:: C and C@t{++}
13591 * Objective-C:: Objective-C
13592 * OpenCL C:: OpenCL C
13593 * Fortran:: Fortran
13595 * Modula-2:: Modula-2
13600 @subsection C and C@t{++}
13602 @cindex C and C@t{++}
13603 @cindex expressions in C or C@t{++}
13605 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
13606 to both languages. Whenever this is the case, we discuss those languages
13610 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
13611 @cindex @sc{gnu} C@t{++}
13612 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
13613 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
13614 effectively, you must compile your C@t{++} programs with a supported
13615 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
13616 compiler (@code{aCC}).
13619 * C Operators:: C and C@t{++} operators
13620 * C Constants:: C and C@t{++} constants
13621 * C Plus Plus Expressions:: C@t{++} expressions
13622 * C Defaults:: Default settings for C and C@t{++}
13623 * C Checks:: C and C@t{++} type and range checks
13624 * Debugging C:: @value{GDBN} and C
13625 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
13626 * Decimal Floating Point:: Numbers in Decimal Floating Point format
13630 @subsubsection C and C@t{++} Operators
13632 @cindex C and C@t{++} operators
13634 Operators must be defined on values of specific types. For instance,
13635 @code{+} is defined on numbers, but not on structures. Operators are
13636 often defined on groups of types.
13638 For the purposes of C and C@t{++}, the following definitions hold:
13643 @emph{Integral types} include @code{int} with any of its storage-class
13644 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
13647 @emph{Floating-point types} include @code{float}, @code{double}, and
13648 @code{long double} (if supported by the target platform).
13651 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
13654 @emph{Scalar types} include all of the above.
13659 The following operators are supported. They are listed here
13660 in order of increasing precedence:
13664 The comma or sequencing operator. Expressions in a comma-separated list
13665 are evaluated from left to right, with the result of the entire
13666 expression being the last expression evaluated.
13669 Assignment. The value of an assignment expression is the value
13670 assigned. Defined on scalar types.
13673 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
13674 and translated to @w{@code{@var{a} = @var{a op b}}}.
13675 @w{@code{@var{op}=}} and @code{=} have the same precedence.
13676 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
13677 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
13680 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
13681 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
13685 Logical @sc{or}. Defined on integral types.
13688 Logical @sc{and}. Defined on integral types.
13691 Bitwise @sc{or}. Defined on integral types.
13694 Bitwise exclusive-@sc{or}. Defined on integral types.
13697 Bitwise @sc{and}. Defined on integral types.
13700 Equality and inequality. Defined on scalar types. The value of these
13701 expressions is 0 for false and non-zero for true.
13703 @item <@r{, }>@r{, }<=@r{, }>=
13704 Less than, greater than, less than or equal, greater than or equal.
13705 Defined on scalar types. The value of these expressions is 0 for false
13706 and non-zero for true.
13709 left shift, and right shift. Defined on integral types.
13712 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13715 Addition and subtraction. Defined on integral types, floating-point types and
13718 @item *@r{, }/@r{, }%
13719 Multiplication, division, and modulus. Multiplication and division are
13720 defined on integral and floating-point types. Modulus is defined on
13724 Increment and decrement. When appearing before a variable, the
13725 operation is performed before the variable is used in an expression;
13726 when appearing after it, the variable's value is used before the
13727 operation takes place.
13730 Pointer dereferencing. Defined on pointer types. Same precedence as
13734 Address operator. Defined on variables. Same precedence as @code{++}.
13736 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
13737 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
13738 to examine the address
13739 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
13743 Negative. Defined on integral and floating-point types. Same
13744 precedence as @code{++}.
13747 Logical negation. Defined on integral types. Same precedence as
13751 Bitwise complement operator. Defined on integral types. Same precedence as
13756 Structure member, and pointer-to-structure member. For convenience,
13757 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
13758 pointer based on the stored type information.
13759 Defined on @code{struct} and @code{union} data.
13762 Dereferences of pointers to members.
13765 Array indexing. @code{@var{a}[@var{i}]} is defined as
13766 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
13769 Function parameter list. Same precedence as @code{->}.
13772 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
13773 and @code{class} types.
13776 Doubled colons also represent the @value{GDBN} scope operator
13777 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
13781 If an operator is redefined in the user code, @value{GDBN} usually
13782 attempts to invoke the redefined version instead of using the operator's
13783 predefined meaning.
13786 @subsubsection C and C@t{++} Constants
13788 @cindex C and C@t{++} constants
13790 @value{GDBN} allows you to express the constants of C and C@t{++} in the
13795 Integer constants are a sequence of digits. Octal constants are
13796 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
13797 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
13798 @samp{l}, specifying that the constant should be treated as a
13802 Floating point constants are a sequence of digits, followed by a decimal
13803 point, followed by a sequence of digits, and optionally followed by an
13804 exponent. An exponent is of the form:
13805 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
13806 sequence of digits. The @samp{+} is optional for positive exponents.
13807 A floating-point constant may also end with a letter @samp{f} or
13808 @samp{F}, specifying that the constant should be treated as being of
13809 the @code{float} (as opposed to the default @code{double}) type; or with
13810 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
13814 Enumerated constants consist of enumerated identifiers, or their
13815 integral equivalents.
13818 Character constants are a single character surrounded by single quotes
13819 (@code{'}), or a number---the ordinal value of the corresponding character
13820 (usually its @sc{ascii} value). Within quotes, the single character may
13821 be represented by a letter or by @dfn{escape sequences}, which are of
13822 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
13823 of the character's ordinal value; or of the form @samp{\@var{x}}, where
13824 @samp{@var{x}} is a predefined special character---for example,
13825 @samp{\n} for newline.
13827 Wide character constants can be written by prefixing a character
13828 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
13829 form of @samp{x}. The target wide character set is used when
13830 computing the value of this constant (@pxref{Character Sets}).
13833 String constants are a sequence of character constants surrounded by
13834 double quotes (@code{"}). Any valid character constant (as described
13835 above) may appear. Double quotes within the string must be preceded by
13836 a backslash, so for instance @samp{"a\"b'c"} is a string of five
13839 Wide string constants can be written by prefixing a string constant
13840 with @samp{L}, as in C. The target wide character set is used when
13841 computing the value of this constant (@pxref{Character Sets}).
13844 Pointer constants are an integral value. You can also write pointers
13845 to constants using the C operator @samp{&}.
13848 Array constants are comma-separated lists surrounded by braces @samp{@{}
13849 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
13850 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
13851 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
13854 @node C Plus Plus Expressions
13855 @subsubsection C@t{++} Expressions
13857 @cindex expressions in C@t{++}
13858 @value{GDBN} expression handling can interpret most C@t{++} expressions.
13860 @cindex debugging C@t{++} programs
13861 @cindex C@t{++} compilers
13862 @cindex debug formats and C@t{++}
13863 @cindex @value{NGCC} and C@t{++}
13865 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
13866 the proper compiler and the proper debug format. Currently,
13867 @value{GDBN} works best when debugging C@t{++} code that is compiled
13868 with the most recent version of @value{NGCC} possible. The DWARF
13869 debugging format is preferred; @value{NGCC} defaults to this on most
13870 popular platforms. Other compilers and/or debug formats are likely to
13871 work badly or not at all when using @value{GDBN} to debug C@t{++}
13872 code. @xref{Compilation}.
13877 @cindex member functions
13879 Member function calls are allowed; you can use expressions like
13882 count = aml->GetOriginal(x, y)
13885 @vindex this@r{, inside C@t{++} member functions}
13886 @cindex namespace in C@t{++}
13888 While a member function is active (in the selected stack frame), your
13889 expressions have the same namespace available as the member function;
13890 that is, @value{GDBN} allows implicit references to the class instance
13891 pointer @code{this} following the same rules as C@t{++}. @code{using}
13892 declarations in the current scope are also respected by @value{GDBN}.
13894 @cindex call overloaded functions
13895 @cindex overloaded functions, calling
13896 @cindex type conversions in C@t{++}
13898 You can call overloaded functions; @value{GDBN} resolves the function
13899 call to the right definition, with some restrictions. @value{GDBN} does not
13900 perform overload resolution involving user-defined type conversions,
13901 calls to constructors, or instantiations of templates that do not exist
13902 in the program. It also cannot handle ellipsis argument lists or
13905 It does perform integral conversions and promotions, floating-point
13906 promotions, arithmetic conversions, pointer conversions, conversions of
13907 class objects to base classes, and standard conversions such as those of
13908 functions or arrays to pointers; it requires an exact match on the
13909 number of function arguments.
13911 Overload resolution is always performed, unless you have specified
13912 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
13913 ,@value{GDBN} Features for C@t{++}}.
13915 You must specify @code{set overload-resolution off} in order to use an
13916 explicit function signature to call an overloaded function, as in
13918 p 'foo(char,int)'('x', 13)
13921 The @value{GDBN} command-completion facility can simplify this;
13922 see @ref{Completion, ,Command Completion}.
13924 @cindex reference declarations
13926 @value{GDBN} understands variables declared as C@t{++} references; you can use
13927 them in expressions just as you do in C@t{++} source---they are automatically
13930 In the parameter list shown when @value{GDBN} displays a frame, the values of
13931 reference variables are not displayed (unlike other variables); this
13932 avoids clutter, since references are often used for large structures.
13933 The @emph{address} of a reference variable is always shown, unless
13934 you have specified @samp{set print address off}.
13937 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
13938 expressions can use it just as expressions in your program do. Since
13939 one scope may be defined in another, you can use @code{::} repeatedly if
13940 necessary, for example in an expression like
13941 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
13942 resolving name scope by reference to source files, in both C and C@t{++}
13943 debugging (@pxref{Variables, ,Program Variables}).
13946 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
13951 @subsubsection C and C@t{++} Defaults
13953 @cindex C and C@t{++} defaults
13955 If you allow @value{GDBN} to set range checking automatically, it
13956 defaults to @code{off} whenever the working language changes to
13957 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
13958 selects the working language.
13960 If you allow @value{GDBN} to set the language automatically, it
13961 recognizes source files whose names end with @file{.c}, @file{.C}, or
13962 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
13963 these files, it sets the working language to C or C@t{++}.
13964 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
13965 for further details.
13968 @subsubsection C and C@t{++} Type and Range Checks
13970 @cindex C and C@t{++} checks
13972 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
13973 checking is used. However, if you turn type checking off, @value{GDBN}
13974 will allow certain non-standard conversions, such as promoting integer
13975 constants to pointers.
13977 Range checking, if turned on, is done on mathematical operations. Array
13978 indices are not checked, since they are often used to index a pointer
13979 that is not itself an array.
13982 @subsubsection @value{GDBN} and C
13984 The @code{set print union} and @code{show print union} commands apply to
13985 the @code{union} type. When set to @samp{on}, any @code{union} that is
13986 inside a @code{struct} or @code{class} is also printed. Otherwise, it
13987 appears as @samp{@{...@}}.
13989 The @code{@@} operator aids in the debugging of dynamic arrays, formed
13990 with pointers and a memory allocation function. @xref{Expressions,
13993 @node Debugging C Plus Plus
13994 @subsubsection @value{GDBN} Features for C@t{++}
13996 @cindex commands for C@t{++}
13998 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
13999 designed specifically for use with C@t{++}. Here is a summary:
14002 @cindex break in overloaded functions
14003 @item @r{breakpoint menus}
14004 When you want a breakpoint in a function whose name is overloaded,
14005 @value{GDBN} has the capability to display a menu of possible breakpoint
14006 locations to help you specify which function definition you want.
14007 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
14009 @cindex overloading in C@t{++}
14010 @item rbreak @var{regex}
14011 Setting breakpoints using regular expressions is helpful for setting
14012 breakpoints on overloaded functions that are not members of any special
14014 @xref{Set Breaks, ,Setting Breakpoints}.
14016 @cindex C@t{++} exception handling
14018 @itemx catch rethrow
14020 Debug C@t{++} exception handling using these commands. @xref{Set
14021 Catchpoints, , Setting Catchpoints}.
14023 @cindex inheritance
14024 @item ptype @var{typename}
14025 Print inheritance relationships as well as other information for type
14027 @xref{Symbols, ,Examining the Symbol Table}.
14029 @item info vtbl @var{expression}.
14030 The @code{info vtbl} command can be used to display the virtual
14031 method tables of the object computed by @var{expression}. This shows
14032 one entry per virtual table; there may be multiple virtual tables when
14033 multiple inheritance is in use.
14035 @cindex C@t{++} symbol display
14036 @item set print demangle
14037 @itemx show print demangle
14038 @itemx set print asm-demangle
14039 @itemx show print asm-demangle
14040 Control whether C@t{++} symbols display in their source form, both when
14041 displaying code as C@t{++} source and when displaying disassemblies.
14042 @xref{Print Settings, ,Print Settings}.
14044 @item set print object
14045 @itemx show print object
14046 Choose whether to print derived (actual) or declared types of objects.
14047 @xref{Print Settings, ,Print Settings}.
14049 @item set print vtbl
14050 @itemx show print vtbl
14051 Control the format for printing virtual function tables.
14052 @xref{Print Settings, ,Print Settings}.
14053 (The @code{vtbl} commands do not work on programs compiled with the HP
14054 ANSI C@t{++} compiler (@code{aCC}).)
14056 @kindex set overload-resolution
14057 @cindex overloaded functions, overload resolution
14058 @item set overload-resolution on
14059 Enable overload resolution for C@t{++} expression evaluation. The default
14060 is on. For overloaded functions, @value{GDBN} evaluates the arguments
14061 and searches for a function whose signature matches the argument types,
14062 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
14063 Expressions, ,C@t{++} Expressions}, for details).
14064 If it cannot find a match, it emits a message.
14066 @item set overload-resolution off
14067 Disable overload resolution for C@t{++} expression evaluation. For
14068 overloaded functions that are not class member functions, @value{GDBN}
14069 chooses the first function of the specified name that it finds in the
14070 symbol table, whether or not its arguments are of the correct type. For
14071 overloaded functions that are class member functions, @value{GDBN}
14072 searches for a function whose signature @emph{exactly} matches the
14075 @kindex show overload-resolution
14076 @item show overload-resolution
14077 Show the current setting of overload resolution.
14079 @item @r{Overloaded symbol names}
14080 You can specify a particular definition of an overloaded symbol, using
14081 the same notation that is used to declare such symbols in C@t{++}: type
14082 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
14083 also use the @value{GDBN} command-line word completion facilities to list the
14084 available choices, or to finish the type list for you.
14085 @xref{Completion,, Command Completion}, for details on how to do this.
14088 @node Decimal Floating Point
14089 @subsubsection Decimal Floating Point format
14090 @cindex decimal floating point format
14092 @value{GDBN} can examine, set and perform computations with numbers in
14093 decimal floating point format, which in the C language correspond to the
14094 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
14095 specified by the extension to support decimal floating-point arithmetic.
14097 There are two encodings in use, depending on the architecture: BID (Binary
14098 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
14099 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
14102 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
14103 to manipulate decimal floating point numbers, it is not possible to convert
14104 (using a cast, for example) integers wider than 32-bit to decimal float.
14106 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
14107 point computations, error checking in decimal float operations ignores
14108 underflow, overflow and divide by zero exceptions.
14110 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
14111 to inspect @code{_Decimal128} values stored in floating point registers.
14112 See @ref{PowerPC,,PowerPC} for more details.
14118 @value{GDBN} can be used to debug programs written in D and compiled with
14119 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
14120 specific feature --- dynamic arrays.
14125 @cindex Go (programming language)
14126 @value{GDBN} can be used to debug programs written in Go and compiled with
14127 @file{gccgo} or @file{6g} compilers.
14129 Here is a summary of the Go-specific features and restrictions:
14132 @cindex current Go package
14133 @item The current Go package
14134 The name of the current package does not need to be specified when
14135 specifying global variables and functions.
14137 For example, given the program:
14141 var myglob = "Shall we?"
14147 When stopped inside @code{main} either of these work:
14151 (gdb) p main.myglob
14154 @cindex builtin Go types
14155 @item Builtin Go types
14156 The @code{string} type is recognized by @value{GDBN} and is printed
14159 @cindex builtin Go functions
14160 @item Builtin Go functions
14161 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
14162 function and handles it internally.
14164 @cindex restrictions on Go expressions
14165 @item Restrictions on Go expressions
14166 All Go operators are supported except @code{&^}.
14167 The Go @code{_} ``blank identifier'' is not supported.
14168 Automatic dereferencing of pointers is not supported.
14172 @subsection Objective-C
14174 @cindex Objective-C
14175 This section provides information about some commands and command
14176 options that are useful for debugging Objective-C code. See also
14177 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
14178 few more commands specific to Objective-C support.
14181 * Method Names in Commands::
14182 * The Print Command with Objective-C::
14185 @node Method Names in Commands
14186 @subsubsection Method Names in Commands
14188 The following commands have been extended to accept Objective-C method
14189 names as line specifications:
14191 @kindex clear@r{, and Objective-C}
14192 @kindex break@r{, and Objective-C}
14193 @kindex info line@r{, and Objective-C}
14194 @kindex jump@r{, and Objective-C}
14195 @kindex list@r{, and Objective-C}
14199 @item @code{info line}
14204 A fully qualified Objective-C method name is specified as
14207 -[@var{Class} @var{methodName}]
14210 where the minus sign is used to indicate an instance method and a
14211 plus sign (not shown) is used to indicate a class method. The class
14212 name @var{Class} and method name @var{methodName} are enclosed in
14213 brackets, similar to the way messages are specified in Objective-C
14214 source code. For example, to set a breakpoint at the @code{create}
14215 instance method of class @code{Fruit} in the program currently being
14219 break -[Fruit create]
14222 To list ten program lines around the @code{initialize} class method,
14226 list +[NSText initialize]
14229 In the current version of @value{GDBN}, the plus or minus sign is
14230 required. In future versions of @value{GDBN}, the plus or minus
14231 sign will be optional, but you can use it to narrow the search. It
14232 is also possible to specify just a method name:
14238 You must specify the complete method name, including any colons. If
14239 your program's source files contain more than one @code{create} method,
14240 you'll be presented with a numbered list of classes that implement that
14241 method. Indicate your choice by number, or type @samp{0} to exit if
14244 As another example, to clear a breakpoint established at the
14245 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
14248 clear -[NSWindow makeKeyAndOrderFront:]
14251 @node The Print Command with Objective-C
14252 @subsubsection The Print Command With Objective-C
14253 @cindex Objective-C, print objects
14254 @kindex print-object
14255 @kindex po @r{(@code{print-object})}
14257 The print command has also been extended to accept methods. For example:
14260 print -[@var{object} hash]
14263 @cindex print an Objective-C object description
14264 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
14266 will tell @value{GDBN} to send the @code{hash} message to @var{object}
14267 and print the result. Also, an additional command has been added,
14268 @code{print-object} or @code{po} for short, which is meant to print
14269 the description of an object. However, this command may only work
14270 with certain Objective-C libraries that have a particular hook
14271 function, @code{_NSPrintForDebugger}, defined.
14274 @subsection OpenCL C
14277 This section provides information about @value{GDBN}s OpenCL C support.
14280 * OpenCL C Datatypes::
14281 * OpenCL C Expressions::
14282 * OpenCL C Operators::
14285 @node OpenCL C Datatypes
14286 @subsubsection OpenCL C Datatypes
14288 @cindex OpenCL C Datatypes
14289 @value{GDBN} supports the builtin scalar and vector datatypes specified
14290 by OpenCL 1.1. In addition the half- and double-precision floating point
14291 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
14292 extensions are also known to @value{GDBN}.
14294 @node OpenCL C Expressions
14295 @subsubsection OpenCL C Expressions
14297 @cindex OpenCL C Expressions
14298 @value{GDBN} supports accesses to vector components including the access as
14299 lvalue where possible. Since OpenCL C is based on C99 most C expressions
14300 supported by @value{GDBN} can be used as well.
14302 @node OpenCL C Operators
14303 @subsubsection OpenCL C Operators
14305 @cindex OpenCL C Operators
14306 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
14310 @subsection Fortran
14311 @cindex Fortran-specific support in @value{GDBN}
14313 @value{GDBN} can be used to debug programs written in Fortran, but it
14314 currently supports only the features of Fortran 77 language.
14316 @cindex trailing underscore, in Fortran symbols
14317 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
14318 among them) append an underscore to the names of variables and
14319 functions. When you debug programs compiled by those compilers, you
14320 will need to refer to variables and functions with a trailing
14324 * Fortran Operators:: Fortran operators and expressions
14325 * Fortran Defaults:: Default settings for Fortran
14326 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
14329 @node Fortran Operators
14330 @subsubsection Fortran Operators and Expressions
14332 @cindex Fortran operators and expressions
14334 Operators must be defined on values of specific types. For instance,
14335 @code{+} is defined on numbers, but not on characters or other non-
14336 arithmetic types. Operators are often defined on groups of types.
14340 The exponentiation operator. It raises the first operand to the power
14344 The range operator. Normally used in the form of array(low:high) to
14345 represent a section of array.
14348 The access component operator. Normally used to access elements in derived
14349 types. Also suitable for unions. As unions aren't part of regular Fortran,
14350 this can only happen when accessing a register that uses a gdbarch-defined
14354 @node Fortran Defaults
14355 @subsubsection Fortran Defaults
14357 @cindex Fortran Defaults
14359 Fortran symbols are usually case-insensitive, so @value{GDBN} by
14360 default uses case-insensitive matches for Fortran symbols. You can
14361 change that with the @samp{set case-insensitive} command, see
14362 @ref{Symbols}, for the details.
14364 @node Special Fortran Commands
14365 @subsubsection Special Fortran Commands
14367 @cindex Special Fortran commands
14369 @value{GDBN} has some commands to support Fortran-specific features,
14370 such as displaying common blocks.
14373 @cindex @code{COMMON} blocks, Fortran
14374 @kindex info common
14375 @item info common @r{[}@var{common-name}@r{]}
14376 This command prints the values contained in the Fortran @code{COMMON}
14377 block whose name is @var{common-name}. With no argument, the names of
14378 all @code{COMMON} blocks visible at the current program location are
14385 @cindex Pascal support in @value{GDBN}, limitations
14386 Debugging Pascal programs which use sets, subranges, file variables, or
14387 nested functions does not currently work. @value{GDBN} does not support
14388 entering expressions, printing values, or similar features using Pascal
14391 The Pascal-specific command @code{set print pascal_static-members}
14392 controls whether static members of Pascal objects are displayed.
14393 @xref{Print Settings, pascal_static-members}.
14396 @subsection Modula-2
14398 @cindex Modula-2, @value{GDBN} support
14400 The extensions made to @value{GDBN} to support Modula-2 only support
14401 output from the @sc{gnu} Modula-2 compiler (which is currently being
14402 developed). Other Modula-2 compilers are not currently supported, and
14403 attempting to debug executables produced by them is most likely
14404 to give an error as @value{GDBN} reads in the executable's symbol
14407 @cindex expressions in Modula-2
14409 * M2 Operators:: Built-in operators
14410 * Built-In Func/Proc:: Built-in functions and procedures
14411 * M2 Constants:: Modula-2 constants
14412 * M2 Types:: Modula-2 types
14413 * M2 Defaults:: Default settings for Modula-2
14414 * Deviations:: Deviations from standard Modula-2
14415 * M2 Checks:: Modula-2 type and range checks
14416 * M2 Scope:: The scope operators @code{::} and @code{.}
14417 * GDB/M2:: @value{GDBN} and Modula-2
14421 @subsubsection Operators
14422 @cindex Modula-2 operators
14424 Operators must be defined on values of specific types. For instance,
14425 @code{+} is defined on numbers, but not on structures. Operators are
14426 often defined on groups of types. For the purposes of Modula-2, the
14427 following definitions hold:
14432 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
14436 @emph{Character types} consist of @code{CHAR} and its subranges.
14439 @emph{Floating-point types} consist of @code{REAL}.
14442 @emph{Pointer types} consist of anything declared as @code{POINTER TO
14446 @emph{Scalar types} consist of all of the above.
14449 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
14452 @emph{Boolean types} consist of @code{BOOLEAN}.
14456 The following operators are supported, and appear in order of
14457 increasing precedence:
14461 Function argument or array index separator.
14464 Assignment. The value of @var{var} @code{:=} @var{value} is
14468 Less than, greater than on integral, floating-point, or enumerated
14472 Less than or equal to, greater than or equal to
14473 on integral, floating-point and enumerated types, or set inclusion on
14474 set types. Same precedence as @code{<}.
14476 @item =@r{, }<>@r{, }#
14477 Equality and two ways of expressing inequality, valid on scalar types.
14478 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
14479 available for inequality, since @code{#} conflicts with the script
14483 Set membership. Defined on set types and the types of their members.
14484 Same precedence as @code{<}.
14487 Boolean disjunction. Defined on boolean types.
14490 Boolean conjunction. Defined on boolean types.
14493 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14496 Addition and subtraction on integral and floating-point types, or union
14497 and difference on set types.
14500 Multiplication on integral and floating-point types, or set intersection
14504 Division on floating-point types, or symmetric set difference on set
14505 types. Same precedence as @code{*}.
14508 Integer division and remainder. Defined on integral types. Same
14509 precedence as @code{*}.
14512 Negative. Defined on @code{INTEGER} and @code{REAL} data.
14515 Pointer dereferencing. Defined on pointer types.
14518 Boolean negation. Defined on boolean types. Same precedence as
14522 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
14523 precedence as @code{^}.
14526 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
14529 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
14533 @value{GDBN} and Modula-2 scope operators.
14537 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
14538 treats the use of the operator @code{IN}, or the use of operators
14539 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
14540 @code{<=}, and @code{>=} on sets as an error.
14544 @node Built-In Func/Proc
14545 @subsubsection Built-in Functions and Procedures
14546 @cindex Modula-2 built-ins
14548 Modula-2 also makes available several built-in procedures and functions.
14549 In describing these, the following metavariables are used:
14554 represents an @code{ARRAY} variable.
14557 represents a @code{CHAR} constant or variable.
14560 represents a variable or constant of integral type.
14563 represents an identifier that belongs to a set. Generally used in the
14564 same function with the metavariable @var{s}. The type of @var{s} should
14565 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
14568 represents a variable or constant of integral or floating-point type.
14571 represents a variable or constant of floating-point type.
14577 represents a variable.
14580 represents a variable or constant of one of many types. See the
14581 explanation of the function for details.
14584 All Modula-2 built-in procedures also return a result, described below.
14588 Returns the absolute value of @var{n}.
14591 If @var{c} is a lower case letter, it returns its upper case
14592 equivalent, otherwise it returns its argument.
14595 Returns the character whose ordinal value is @var{i}.
14598 Decrements the value in the variable @var{v} by one. Returns the new value.
14600 @item DEC(@var{v},@var{i})
14601 Decrements the value in the variable @var{v} by @var{i}. Returns the
14604 @item EXCL(@var{m},@var{s})
14605 Removes the element @var{m} from the set @var{s}. Returns the new
14608 @item FLOAT(@var{i})
14609 Returns the floating point equivalent of the integer @var{i}.
14611 @item HIGH(@var{a})
14612 Returns the index of the last member of @var{a}.
14615 Increments the value in the variable @var{v} by one. Returns the new value.
14617 @item INC(@var{v},@var{i})
14618 Increments the value in the variable @var{v} by @var{i}. Returns the
14621 @item INCL(@var{m},@var{s})
14622 Adds the element @var{m} to the set @var{s} if it is not already
14623 there. Returns the new set.
14626 Returns the maximum value of the type @var{t}.
14629 Returns the minimum value of the type @var{t}.
14632 Returns boolean TRUE if @var{i} is an odd number.
14635 Returns the ordinal value of its argument. For example, the ordinal
14636 value of a character is its @sc{ascii} value (on machines supporting the
14637 @sc{ascii} character set). @var{x} must be of an ordered type, which include
14638 integral, character and enumerated types.
14640 @item SIZE(@var{x})
14641 Returns the size of its argument. @var{x} can be a variable or a type.
14643 @item TRUNC(@var{r})
14644 Returns the integral part of @var{r}.
14646 @item TSIZE(@var{x})
14647 Returns the size of its argument. @var{x} can be a variable or a type.
14649 @item VAL(@var{t},@var{i})
14650 Returns the member of the type @var{t} whose ordinal value is @var{i}.
14654 @emph{Warning:} Sets and their operations are not yet supported, so
14655 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
14659 @cindex Modula-2 constants
14661 @subsubsection Constants
14663 @value{GDBN} allows you to express the constants of Modula-2 in the following
14669 Integer constants are simply a sequence of digits. When used in an
14670 expression, a constant is interpreted to be type-compatible with the
14671 rest of the expression. Hexadecimal integers are specified by a
14672 trailing @samp{H}, and octal integers by a trailing @samp{B}.
14675 Floating point constants appear as a sequence of digits, followed by a
14676 decimal point and another sequence of digits. An optional exponent can
14677 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
14678 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
14679 digits of the floating point constant must be valid decimal (base 10)
14683 Character constants consist of a single character enclosed by a pair of
14684 like quotes, either single (@code{'}) or double (@code{"}). They may
14685 also be expressed by their ordinal value (their @sc{ascii} value, usually)
14686 followed by a @samp{C}.
14689 String constants consist of a sequence of characters enclosed by a
14690 pair of like quotes, either single (@code{'}) or double (@code{"}).
14691 Escape sequences in the style of C are also allowed. @xref{C
14692 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
14696 Enumerated constants consist of an enumerated identifier.
14699 Boolean constants consist of the identifiers @code{TRUE} and
14703 Pointer constants consist of integral values only.
14706 Set constants are not yet supported.
14710 @subsubsection Modula-2 Types
14711 @cindex Modula-2 types
14713 Currently @value{GDBN} can print the following data types in Modula-2
14714 syntax: array types, record types, set types, pointer types, procedure
14715 types, enumerated types, subrange types and base types. You can also
14716 print the contents of variables declared using these type.
14717 This section gives a number of simple source code examples together with
14718 sample @value{GDBN} sessions.
14720 The first example contains the following section of code:
14729 and you can request @value{GDBN} to interrogate the type and value of
14730 @code{r} and @code{s}.
14733 (@value{GDBP}) print s
14735 (@value{GDBP}) ptype s
14737 (@value{GDBP}) print r
14739 (@value{GDBP}) ptype r
14744 Likewise if your source code declares @code{s} as:
14748 s: SET ['A'..'Z'] ;
14752 then you may query the type of @code{s} by:
14755 (@value{GDBP}) ptype s
14756 type = SET ['A'..'Z']
14760 Note that at present you cannot interactively manipulate set
14761 expressions using the debugger.
14763 The following example shows how you might declare an array in Modula-2
14764 and how you can interact with @value{GDBN} to print its type and contents:
14768 s: ARRAY [-10..10] OF CHAR ;
14772 (@value{GDBP}) ptype s
14773 ARRAY [-10..10] OF CHAR
14776 Note that the array handling is not yet complete and although the type
14777 is printed correctly, expression handling still assumes that all
14778 arrays have a lower bound of zero and not @code{-10} as in the example
14781 Here are some more type related Modula-2 examples:
14785 colour = (blue, red, yellow, green) ;
14786 t = [blue..yellow] ;
14794 The @value{GDBN} interaction shows how you can query the data type
14795 and value of a variable.
14798 (@value{GDBP}) print s
14800 (@value{GDBP}) ptype t
14801 type = [blue..yellow]
14805 In this example a Modula-2 array is declared and its contents
14806 displayed. Observe that the contents are written in the same way as
14807 their @code{C} counterparts.
14811 s: ARRAY [1..5] OF CARDINAL ;
14817 (@value{GDBP}) print s
14818 $1 = @{1, 0, 0, 0, 0@}
14819 (@value{GDBP}) ptype s
14820 type = ARRAY [1..5] OF CARDINAL
14823 The Modula-2 language interface to @value{GDBN} also understands
14824 pointer types as shown in this example:
14828 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
14835 and you can request that @value{GDBN} describes the type of @code{s}.
14838 (@value{GDBP}) ptype s
14839 type = POINTER TO ARRAY [1..5] OF CARDINAL
14842 @value{GDBN} handles compound types as we can see in this example.
14843 Here we combine array types, record types, pointer types and subrange
14854 myarray = ARRAY myrange OF CARDINAL ;
14855 myrange = [-2..2] ;
14857 s: POINTER TO ARRAY myrange OF foo ;
14861 and you can ask @value{GDBN} to describe the type of @code{s} as shown
14865 (@value{GDBP}) ptype s
14866 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
14869 f3 : ARRAY [-2..2] OF CARDINAL;
14874 @subsubsection Modula-2 Defaults
14875 @cindex Modula-2 defaults
14877 If type and range checking are set automatically by @value{GDBN}, they
14878 both default to @code{on} whenever the working language changes to
14879 Modula-2. This happens regardless of whether you or @value{GDBN}
14880 selected the working language.
14882 If you allow @value{GDBN} to set the language automatically, then entering
14883 code compiled from a file whose name ends with @file{.mod} sets the
14884 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
14885 Infer the Source Language}, for further details.
14888 @subsubsection Deviations from Standard Modula-2
14889 @cindex Modula-2, deviations from
14891 A few changes have been made to make Modula-2 programs easier to debug.
14892 This is done primarily via loosening its type strictness:
14896 Unlike in standard Modula-2, pointer constants can be formed by
14897 integers. This allows you to modify pointer variables during
14898 debugging. (In standard Modula-2, the actual address contained in a
14899 pointer variable is hidden from you; it can only be modified
14900 through direct assignment to another pointer variable or expression that
14901 returned a pointer.)
14904 C escape sequences can be used in strings and characters to represent
14905 non-printable characters. @value{GDBN} prints out strings with these
14906 escape sequences embedded. Single non-printable characters are
14907 printed using the @samp{CHR(@var{nnn})} format.
14910 The assignment operator (@code{:=}) returns the value of its right-hand
14914 All built-in procedures both modify @emph{and} return their argument.
14918 @subsubsection Modula-2 Type and Range Checks
14919 @cindex Modula-2 checks
14922 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
14925 @c FIXME remove warning when type/range checks added
14927 @value{GDBN} considers two Modula-2 variables type equivalent if:
14931 They are of types that have been declared equivalent via a @code{TYPE
14932 @var{t1} = @var{t2}} statement
14935 They have been declared on the same line. (Note: This is true of the
14936 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
14939 As long as type checking is enabled, any attempt to combine variables
14940 whose types are not equivalent is an error.
14942 Range checking is done on all mathematical operations, assignment, array
14943 index bounds, and all built-in functions and procedures.
14946 @subsubsection The Scope Operators @code{::} and @code{.}
14948 @cindex @code{.}, Modula-2 scope operator
14949 @cindex colon, doubled as scope operator
14951 @vindex colon-colon@r{, in Modula-2}
14952 @c Info cannot handle :: but TeX can.
14955 @vindex ::@r{, in Modula-2}
14958 There are a few subtle differences between the Modula-2 scope operator
14959 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
14964 @var{module} . @var{id}
14965 @var{scope} :: @var{id}
14969 where @var{scope} is the name of a module or a procedure,
14970 @var{module} the name of a module, and @var{id} is any declared
14971 identifier within your program, except another module.
14973 Using the @code{::} operator makes @value{GDBN} search the scope
14974 specified by @var{scope} for the identifier @var{id}. If it is not
14975 found in the specified scope, then @value{GDBN} searches all scopes
14976 enclosing the one specified by @var{scope}.
14978 Using the @code{.} operator makes @value{GDBN} search the current scope for
14979 the identifier specified by @var{id} that was imported from the
14980 definition module specified by @var{module}. With this operator, it is
14981 an error if the identifier @var{id} was not imported from definition
14982 module @var{module}, or if @var{id} is not an identifier in
14986 @subsubsection @value{GDBN} and Modula-2
14988 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
14989 Five subcommands of @code{set print} and @code{show print} apply
14990 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
14991 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
14992 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
14993 analogue in Modula-2.
14995 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
14996 with any language, is not useful with Modula-2. Its
14997 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
14998 created in Modula-2 as they can in C or C@t{++}. However, because an
14999 address can be specified by an integral constant, the construct
15000 @samp{@{@var{type}@}@var{adrexp}} is still useful.
15002 @cindex @code{#} in Modula-2
15003 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
15004 interpreted as the beginning of a comment. Use @code{<>} instead.
15010 The extensions made to @value{GDBN} for Ada only support
15011 output from the @sc{gnu} Ada (GNAT) compiler.
15012 Other Ada compilers are not currently supported, and
15013 attempting to debug executables produced by them is most likely
15017 @cindex expressions in Ada
15019 * Ada Mode Intro:: General remarks on the Ada syntax
15020 and semantics supported by Ada mode
15022 * Omissions from Ada:: Restrictions on the Ada expression syntax.
15023 * Additions to Ada:: Extensions of the Ada expression syntax.
15024 * Stopping Before Main Program:: Debugging the program during elaboration.
15025 * Ada Exceptions:: Ada Exceptions
15026 * Ada Tasks:: Listing and setting breakpoints in tasks.
15027 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
15028 * Ravenscar Profile:: Tasking Support when using the Ravenscar
15030 * Ada Glitches:: Known peculiarities of Ada mode.
15033 @node Ada Mode Intro
15034 @subsubsection Introduction
15035 @cindex Ada mode, general
15037 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
15038 syntax, with some extensions.
15039 The philosophy behind the design of this subset is
15043 That @value{GDBN} should provide basic literals and access to operations for
15044 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
15045 leaving more sophisticated computations to subprograms written into the
15046 program (which therefore may be called from @value{GDBN}).
15049 That type safety and strict adherence to Ada language restrictions
15050 are not particularly important to the @value{GDBN} user.
15053 That brevity is important to the @value{GDBN} user.
15056 Thus, for brevity, the debugger acts as if all names declared in
15057 user-written packages are directly visible, even if they are not visible
15058 according to Ada rules, thus making it unnecessary to fully qualify most
15059 names with their packages, regardless of context. Where this causes
15060 ambiguity, @value{GDBN} asks the user's intent.
15062 The debugger will start in Ada mode if it detects an Ada main program.
15063 As for other languages, it will enter Ada mode when stopped in a program that
15064 was translated from an Ada source file.
15066 While in Ada mode, you may use `@t{--}' for comments. This is useful
15067 mostly for documenting command files. The standard @value{GDBN} comment
15068 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
15069 middle (to allow based literals).
15071 The debugger supports limited overloading. Given a subprogram call in which
15072 the function symbol has multiple definitions, it will use the number of
15073 actual parameters and some information about their types to attempt to narrow
15074 the set of definitions. It also makes very limited use of context, preferring
15075 procedures to functions in the context of the @code{call} command, and
15076 functions to procedures elsewhere.
15078 @node Omissions from Ada
15079 @subsubsection Omissions from Ada
15080 @cindex Ada, omissions from
15082 Here are the notable omissions from the subset:
15086 Only a subset of the attributes are supported:
15090 @t{'First}, @t{'Last}, and @t{'Length}
15091 on array objects (not on types and subtypes).
15094 @t{'Min} and @t{'Max}.
15097 @t{'Pos} and @t{'Val}.
15103 @t{'Range} on array objects (not subtypes), but only as the right
15104 operand of the membership (@code{in}) operator.
15107 @t{'Access}, @t{'Unchecked_Access}, and
15108 @t{'Unrestricted_Access} (a GNAT extension).
15116 @code{Characters.Latin_1} are not available and
15117 concatenation is not implemented. Thus, escape characters in strings are
15118 not currently available.
15121 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
15122 equality of representations. They will generally work correctly
15123 for strings and arrays whose elements have integer or enumeration types.
15124 They may not work correctly for arrays whose element
15125 types have user-defined equality, for arrays of real values
15126 (in particular, IEEE-conformant floating point, because of negative
15127 zeroes and NaNs), and for arrays whose elements contain unused bits with
15128 indeterminate values.
15131 The other component-by-component array operations (@code{and}, @code{or},
15132 @code{xor}, @code{not}, and relational tests other than equality)
15133 are not implemented.
15136 @cindex array aggregates (Ada)
15137 @cindex record aggregates (Ada)
15138 @cindex aggregates (Ada)
15139 There is limited support for array and record aggregates. They are
15140 permitted only on the right sides of assignments, as in these examples:
15143 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
15144 (@value{GDBP}) set An_Array := (1, others => 0)
15145 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
15146 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
15147 (@value{GDBP}) set A_Record := (1, "Peter", True);
15148 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
15152 discriminant's value by assigning an aggregate has an
15153 undefined effect if that discriminant is used within the record.
15154 However, you can first modify discriminants by directly assigning to
15155 them (which normally would not be allowed in Ada), and then performing an
15156 aggregate assignment. For example, given a variable @code{A_Rec}
15157 declared to have a type such as:
15160 type Rec (Len : Small_Integer := 0) is record
15162 Vals : IntArray (1 .. Len);
15166 you can assign a value with a different size of @code{Vals} with two
15170 (@value{GDBP}) set A_Rec.Len := 4
15171 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
15174 As this example also illustrates, @value{GDBN} is very loose about the usual
15175 rules concerning aggregates. You may leave out some of the
15176 components of an array or record aggregate (such as the @code{Len}
15177 component in the assignment to @code{A_Rec} above); they will retain their
15178 original values upon assignment. You may freely use dynamic values as
15179 indices in component associations. You may even use overlapping or
15180 redundant component associations, although which component values are
15181 assigned in such cases is not defined.
15184 Calls to dispatching subprograms are not implemented.
15187 The overloading algorithm is much more limited (i.e., less selective)
15188 than that of real Ada. It makes only limited use of the context in
15189 which a subexpression appears to resolve its meaning, and it is much
15190 looser in its rules for allowing type matches. As a result, some
15191 function calls will be ambiguous, and the user will be asked to choose
15192 the proper resolution.
15195 The @code{new} operator is not implemented.
15198 Entry calls are not implemented.
15201 Aside from printing, arithmetic operations on the native VAX floating-point
15202 formats are not supported.
15205 It is not possible to slice a packed array.
15208 The names @code{True} and @code{False}, when not part of a qualified name,
15209 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
15211 Should your program
15212 redefine these names in a package or procedure (at best a dubious practice),
15213 you will have to use fully qualified names to access their new definitions.
15216 @node Additions to Ada
15217 @subsubsection Additions to Ada
15218 @cindex Ada, deviations from
15220 As it does for other languages, @value{GDBN} makes certain generic
15221 extensions to Ada (@pxref{Expressions}):
15225 If the expression @var{E} is a variable residing in memory (typically
15226 a local variable or array element) and @var{N} is a positive integer,
15227 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
15228 @var{N}-1 adjacent variables following it in memory as an array. In
15229 Ada, this operator is generally not necessary, since its prime use is
15230 in displaying parts of an array, and slicing will usually do this in
15231 Ada. However, there are occasional uses when debugging programs in
15232 which certain debugging information has been optimized away.
15235 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
15236 appears in function or file @var{B}.'' When @var{B} is a file name,
15237 you must typically surround it in single quotes.
15240 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
15241 @var{type} that appears at address @var{addr}.''
15244 A name starting with @samp{$} is a convenience variable
15245 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
15248 In addition, @value{GDBN} provides a few other shortcuts and outright
15249 additions specific to Ada:
15253 The assignment statement is allowed as an expression, returning
15254 its right-hand operand as its value. Thus, you may enter
15257 (@value{GDBP}) set x := y + 3
15258 (@value{GDBP}) print A(tmp := y + 1)
15262 The semicolon is allowed as an ``operator,'' returning as its value
15263 the value of its right-hand operand.
15264 This allows, for example,
15265 complex conditional breaks:
15268 (@value{GDBP}) break f
15269 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
15273 Rather than use catenation and symbolic character names to introduce special
15274 characters into strings, one may instead use a special bracket notation,
15275 which is also used to print strings. A sequence of characters of the form
15276 @samp{["@var{XX}"]} within a string or character literal denotes the
15277 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
15278 sequence of characters @samp{["""]} also denotes a single quotation mark
15279 in strings. For example,
15281 "One line.["0a"]Next line.["0a"]"
15284 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
15288 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
15289 @t{'Max} is optional (and is ignored in any case). For example, it is valid
15293 (@value{GDBP}) print 'max(x, y)
15297 When printing arrays, @value{GDBN} uses positional notation when the
15298 array has a lower bound of 1, and uses a modified named notation otherwise.
15299 For example, a one-dimensional array of three integers with a lower bound
15300 of 3 might print as
15307 That is, in contrast to valid Ada, only the first component has a @code{=>}
15311 You may abbreviate attributes in expressions with any unique,
15312 multi-character subsequence of
15313 their names (an exact match gets preference).
15314 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
15315 in place of @t{a'length}.
15318 @cindex quoting Ada internal identifiers
15319 Since Ada is case-insensitive, the debugger normally maps identifiers you type
15320 to lower case. The GNAT compiler uses upper-case characters for
15321 some of its internal identifiers, which are normally of no interest to users.
15322 For the rare occasions when you actually have to look at them,
15323 enclose them in angle brackets to avoid the lower-case mapping.
15326 (@value{GDBP}) print <JMPBUF_SAVE>[0]
15330 Printing an object of class-wide type or dereferencing an
15331 access-to-class-wide value will display all the components of the object's
15332 specific type (as indicated by its run-time tag). Likewise, component
15333 selection on such a value will operate on the specific type of the
15338 @node Stopping Before Main Program
15339 @subsubsection Stopping at the Very Beginning
15341 @cindex breakpointing Ada elaboration code
15342 It is sometimes necessary to debug the program during elaboration, and
15343 before reaching the main procedure.
15344 As defined in the Ada Reference
15345 Manual, the elaboration code is invoked from a procedure called
15346 @code{adainit}. To run your program up to the beginning of
15347 elaboration, simply use the following two commands:
15348 @code{tbreak adainit} and @code{run}.
15350 @node Ada Exceptions
15351 @subsubsection Ada Exceptions
15353 A command is provided to list all Ada exceptions:
15356 @kindex info exceptions
15357 @item info exceptions
15358 @itemx info exceptions @var{regexp}
15359 The @code{info exceptions} command allows you to list all Ada exceptions
15360 defined within the program being debugged, as well as their addresses.
15361 With a regular expression, @var{regexp}, as argument, only those exceptions
15362 whose names match @var{regexp} are listed.
15365 Below is a small example, showing how the command can be used, first
15366 without argument, and next with a regular expression passed as an
15370 (@value{GDBP}) info exceptions
15371 All defined Ada exceptions:
15372 constraint_error: 0x613da0
15373 program_error: 0x613d20
15374 storage_error: 0x613ce0
15375 tasking_error: 0x613ca0
15376 const.aint_global_e: 0x613b00
15377 (@value{GDBP}) info exceptions const.aint
15378 All Ada exceptions matching regular expression "const.aint":
15379 constraint_error: 0x613da0
15380 const.aint_global_e: 0x613b00
15383 It is also possible to ask @value{GDBN} to stop your program's execution
15384 when an exception is raised. For more details, see @ref{Set Catchpoints}.
15387 @subsubsection Extensions for Ada Tasks
15388 @cindex Ada, tasking
15390 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
15391 @value{GDBN} provides the following task-related commands:
15396 This command shows a list of current Ada tasks, as in the following example:
15403 (@value{GDBP}) info tasks
15404 ID TID P-ID Pri State Name
15405 1 8088000 0 15 Child Activation Wait main_task
15406 2 80a4000 1 15 Accept Statement b
15407 3 809a800 1 15 Child Activation Wait a
15408 * 4 80ae800 3 15 Runnable c
15413 In this listing, the asterisk before the last task indicates it to be the
15414 task currently being inspected.
15418 Represents @value{GDBN}'s internal task number.
15424 The parent's task ID (@value{GDBN}'s internal task number).
15427 The base priority of the task.
15430 Current state of the task.
15434 The task has been created but has not been activated. It cannot be
15438 The task is not blocked for any reason known to Ada. (It may be waiting
15439 for a mutex, though.) It is conceptually "executing" in normal mode.
15442 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
15443 that were waiting on terminate alternatives have been awakened and have
15444 terminated themselves.
15446 @item Child Activation Wait
15447 The task is waiting for created tasks to complete activation.
15449 @item Accept Statement
15450 The task is waiting on an accept or selective wait statement.
15452 @item Waiting on entry call
15453 The task is waiting on an entry call.
15455 @item Async Select Wait
15456 The task is waiting to start the abortable part of an asynchronous
15460 The task is waiting on a select statement with only a delay
15463 @item Child Termination Wait
15464 The task is sleeping having completed a master within itself, and is
15465 waiting for the tasks dependent on that master to become terminated or
15466 waiting on a terminate Phase.
15468 @item Wait Child in Term Alt
15469 The task is sleeping waiting for tasks on terminate alternatives to
15470 finish terminating.
15472 @item Accepting RV with @var{taskno}
15473 The task is accepting a rendez-vous with the task @var{taskno}.
15477 Name of the task in the program.
15481 @kindex info task @var{taskno}
15482 @item info task @var{taskno}
15483 This command shows detailled informations on the specified task, as in
15484 the following example:
15489 (@value{GDBP}) info tasks
15490 ID TID P-ID Pri State Name
15491 1 8077880 0 15 Child Activation Wait main_task
15492 * 2 807c468 1 15 Runnable task_1
15493 (@value{GDBP}) info task 2
15494 Ada Task: 0x807c468
15497 Parent: 1 (main_task)
15503 @kindex task@r{ (Ada)}
15504 @cindex current Ada task ID
15505 This command prints the ID of the current task.
15511 (@value{GDBP}) info tasks
15512 ID TID P-ID Pri State Name
15513 1 8077870 0 15 Child Activation Wait main_task
15514 * 2 807c458 1 15 Runnable t
15515 (@value{GDBP}) task
15516 [Current task is 2]
15519 @item task @var{taskno}
15520 @cindex Ada task switching
15521 This command is like the @code{thread @var{threadno}}
15522 command (@pxref{Threads}). It switches the context of debugging
15523 from the current task to the given task.
15529 (@value{GDBP}) info tasks
15530 ID TID P-ID Pri State Name
15531 1 8077870 0 15 Child Activation Wait main_task
15532 * 2 807c458 1 15 Runnable t
15533 (@value{GDBP}) task 1
15534 [Switching to task 1]
15535 #0 0x8067726 in pthread_cond_wait ()
15537 #0 0x8067726 in pthread_cond_wait ()
15538 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
15539 #2 0x805cb63 in system.task_primitives.operations.sleep ()
15540 #3 0x806153e in system.tasking.stages.activate_tasks ()
15541 #4 0x804aacc in un () at un.adb:5
15544 @item break @var{linespec} task @var{taskno}
15545 @itemx break @var{linespec} task @var{taskno} if @dots{}
15546 @cindex breakpoints and tasks, in Ada
15547 @cindex task breakpoints, in Ada
15548 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
15549 These commands are like the @code{break @dots{} thread @dots{}}
15550 command (@pxref{Thread Stops}).
15551 @var{linespec} specifies source lines, as described
15552 in @ref{Specify Location}.
15554 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
15555 to specify that you only want @value{GDBN} to stop the program when a
15556 particular Ada task reaches this breakpoint. @var{taskno} is one of the
15557 numeric task identifiers assigned by @value{GDBN}, shown in the first
15558 column of the @samp{info tasks} display.
15560 If you do not specify @samp{task @var{taskno}} when you set a
15561 breakpoint, the breakpoint applies to @emph{all} tasks of your
15564 You can use the @code{task} qualifier on conditional breakpoints as
15565 well; in this case, place @samp{task @var{taskno}} before the
15566 breakpoint condition (before the @code{if}).
15574 (@value{GDBP}) info tasks
15575 ID TID P-ID Pri State Name
15576 1 140022020 0 15 Child Activation Wait main_task
15577 2 140045060 1 15 Accept/Select Wait t2
15578 3 140044840 1 15 Runnable t1
15579 * 4 140056040 1 15 Runnable t3
15580 (@value{GDBP}) b 15 task 2
15581 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
15582 (@value{GDBP}) cont
15587 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
15589 (@value{GDBP}) info tasks
15590 ID TID P-ID Pri State Name
15591 1 140022020 0 15 Child Activation Wait main_task
15592 * 2 140045060 1 15 Runnable t2
15593 3 140044840 1 15 Runnable t1
15594 4 140056040 1 15 Delay Sleep t3
15598 @node Ada Tasks and Core Files
15599 @subsubsection Tasking Support when Debugging Core Files
15600 @cindex Ada tasking and core file debugging
15602 When inspecting a core file, as opposed to debugging a live program,
15603 tasking support may be limited or even unavailable, depending on
15604 the platform being used.
15605 For instance, on x86-linux, the list of tasks is available, but task
15606 switching is not supported. On Tru64, however, task switching will work
15609 On certain platforms, including Tru64, the debugger needs to perform some
15610 memory writes in order to provide Ada tasking support. When inspecting
15611 a core file, this means that the core file must be opened with read-write
15612 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
15613 Under these circumstances, you should make a backup copy of the core
15614 file before inspecting it with @value{GDBN}.
15616 @node Ravenscar Profile
15617 @subsubsection Tasking Support when using the Ravenscar Profile
15618 @cindex Ravenscar Profile
15620 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
15621 specifically designed for systems with safety-critical real-time
15625 @kindex set ravenscar task-switching on
15626 @cindex task switching with program using Ravenscar Profile
15627 @item set ravenscar task-switching on
15628 Allows task switching when debugging a program that uses the Ravenscar
15629 Profile. This is the default.
15631 @kindex set ravenscar task-switching off
15632 @item set ravenscar task-switching off
15633 Turn off task switching when debugging a program that uses the Ravenscar
15634 Profile. This is mostly intended to disable the code that adds support
15635 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
15636 the Ravenscar runtime is preventing @value{GDBN} from working properly.
15637 To be effective, this command should be run before the program is started.
15639 @kindex show ravenscar task-switching
15640 @item show ravenscar task-switching
15641 Show whether it is possible to switch from task to task in a program
15642 using the Ravenscar Profile.
15647 @subsubsection Known Peculiarities of Ada Mode
15648 @cindex Ada, problems
15650 Besides the omissions listed previously (@pxref{Omissions from Ada}),
15651 we know of several problems with and limitations of Ada mode in
15653 some of which will be fixed with planned future releases of the debugger
15654 and the GNU Ada compiler.
15658 Static constants that the compiler chooses not to materialize as objects in
15659 storage are invisible to the debugger.
15662 Named parameter associations in function argument lists are ignored (the
15663 argument lists are treated as positional).
15666 Many useful library packages are currently invisible to the debugger.
15669 Fixed-point arithmetic, conversions, input, and output is carried out using
15670 floating-point arithmetic, and may give results that only approximate those on
15674 The GNAT compiler never generates the prefix @code{Standard} for any of
15675 the standard symbols defined by the Ada language. @value{GDBN} knows about
15676 this: it will strip the prefix from names when you use it, and will never
15677 look for a name you have so qualified among local symbols, nor match against
15678 symbols in other packages or subprograms. If you have
15679 defined entities anywhere in your program other than parameters and
15680 local variables whose simple names match names in @code{Standard},
15681 GNAT's lack of qualification here can cause confusion. When this happens,
15682 you can usually resolve the confusion
15683 by qualifying the problematic names with package
15684 @code{Standard} explicitly.
15687 Older versions of the compiler sometimes generate erroneous debugging
15688 information, resulting in the debugger incorrectly printing the value
15689 of affected entities. In some cases, the debugger is able to work
15690 around an issue automatically. In other cases, the debugger is able
15691 to work around the issue, but the work-around has to be specifically
15694 @kindex set ada trust-PAD-over-XVS
15695 @kindex show ada trust-PAD-over-XVS
15698 @item set ada trust-PAD-over-XVS on
15699 Configure GDB to strictly follow the GNAT encoding when computing the
15700 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
15701 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
15702 a complete description of the encoding used by the GNAT compiler).
15703 This is the default.
15705 @item set ada trust-PAD-over-XVS off
15706 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
15707 sometimes prints the wrong value for certain entities, changing @code{ada
15708 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
15709 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
15710 @code{off}, but this incurs a slight performance penalty, so it is
15711 recommended to leave this setting to @code{on} unless necessary.
15715 @node Unsupported Languages
15716 @section Unsupported Languages
15718 @cindex unsupported languages
15719 @cindex minimal language
15720 In addition to the other fully-supported programming languages,
15721 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
15722 It does not represent a real programming language, but provides a set
15723 of capabilities close to what the C or assembly languages provide.
15724 This should allow most simple operations to be performed while debugging
15725 an application that uses a language currently not supported by @value{GDBN}.
15727 If the language is set to @code{auto}, @value{GDBN} will automatically
15728 select this language if the current frame corresponds to an unsupported
15732 @chapter Examining the Symbol Table
15734 The commands described in this chapter allow you to inquire about the
15735 symbols (names of variables, functions and types) defined in your
15736 program. This information is inherent in the text of your program and
15737 does not change as your program executes. @value{GDBN} finds it in your
15738 program's symbol table, in the file indicated when you started @value{GDBN}
15739 (@pxref{File Options, ,Choosing Files}), or by one of the
15740 file-management commands (@pxref{Files, ,Commands to Specify Files}).
15742 @cindex symbol names
15743 @cindex names of symbols
15744 @cindex quoting names
15745 Occasionally, you may need to refer to symbols that contain unusual
15746 characters, which @value{GDBN} ordinarily treats as word delimiters. The
15747 most frequent case is in referring to static variables in other
15748 source files (@pxref{Variables,,Program Variables}). File names
15749 are recorded in object files as debugging symbols, but @value{GDBN} would
15750 ordinarily parse a typical file name, like @file{foo.c}, as the three words
15751 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
15752 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
15759 looks up the value of @code{x} in the scope of the file @file{foo.c}.
15762 @cindex case-insensitive symbol names
15763 @cindex case sensitivity in symbol names
15764 @kindex set case-sensitive
15765 @item set case-sensitive on
15766 @itemx set case-sensitive off
15767 @itemx set case-sensitive auto
15768 Normally, when @value{GDBN} looks up symbols, it matches their names
15769 with case sensitivity determined by the current source language.
15770 Occasionally, you may wish to control that. The command @code{set
15771 case-sensitive} lets you do that by specifying @code{on} for
15772 case-sensitive matches or @code{off} for case-insensitive ones. If
15773 you specify @code{auto}, case sensitivity is reset to the default
15774 suitable for the source language. The default is case-sensitive
15775 matches for all languages except for Fortran, for which the default is
15776 case-insensitive matches.
15778 @kindex show case-sensitive
15779 @item show case-sensitive
15780 This command shows the current setting of case sensitivity for symbols
15783 @kindex set print type methods
15784 @item set print type methods
15785 @itemx set print type methods on
15786 @itemx set print type methods off
15787 Normally, when @value{GDBN} prints a class, it displays any methods
15788 declared in that class. You can control this behavior either by
15789 passing the appropriate flag to @code{ptype}, or using @command{set
15790 print type methods}. Specifying @code{on} will cause @value{GDBN} to
15791 display the methods; this is the default. Specifying @code{off} will
15792 cause @value{GDBN} to omit the methods.
15794 @kindex show print type methods
15795 @item show print type methods
15796 This command shows the current setting of method display when printing
15799 @kindex set print type typedefs
15800 @item set print type typedefs
15801 @itemx set print type typedefs on
15802 @itemx set print type typedefs off
15804 Normally, when @value{GDBN} prints a class, it displays any typedefs
15805 defined in that class. You can control this behavior either by
15806 passing the appropriate flag to @code{ptype}, or using @command{set
15807 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
15808 display the typedef definitions; this is the default. Specifying
15809 @code{off} will cause @value{GDBN} to omit the typedef definitions.
15810 Note that this controls whether the typedef definition itself is
15811 printed, not whether typedef names are substituted when printing other
15814 @kindex show print type typedefs
15815 @item show print type typedefs
15816 This command shows the current setting of typedef display when
15819 @kindex info address
15820 @cindex address of a symbol
15821 @item info address @var{symbol}
15822 Describe where the data for @var{symbol} is stored. For a register
15823 variable, this says which register it is kept in. For a non-register
15824 local variable, this prints the stack-frame offset at which the variable
15827 Note the contrast with @samp{print &@var{symbol}}, which does not work
15828 at all for a register variable, and for a stack local variable prints
15829 the exact address of the current instantiation of the variable.
15831 @kindex info symbol
15832 @cindex symbol from address
15833 @cindex closest symbol and offset for an address
15834 @item info symbol @var{addr}
15835 Print the name of a symbol which is stored at the address @var{addr}.
15836 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
15837 nearest symbol and an offset from it:
15840 (@value{GDBP}) info symbol 0x54320
15841 _initialize_vx + 396 in section .text
15845 This is the opposite of the @code{info address} command. You can use
15846 it to find out the name of a variable or a function given its address.
15848 For dynamically linked executables, the name of executable or shared
15849 library containing the symbol is also printed:
15852 (@value{GDBP}) info symbol 0x400225
15853 _start + 5 in section .text of /tmp/a.out
15854 (@value{GDBP}) info symbol 0x2aaaac2811cf
15855 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
15859 @item whatis[/@var{flags}] [@var{arg}]
15860 Print the data type of @var{arg}, which can be either an expression
15861 or a name of a data type. With no argument, print the data type of
15862 @code{$}, the last value in the value history.
15864 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
15865 is not actually evaluated, and any side-effecting operations (such as
15866 assignments or function calls) inside it do not take place.
15868 If @var{arg} is a variable or an expression, @code{whatis} prints its
15869 literal type as it is used in the source code. If the type was
15870 defined using a @code{typedef}, @code{whatis} will @emph{not} print
15871 the data type underlying the @code{typedef}. If the type of the
15872 variable or the expression is a compound data type, such as
15873 @code{struct} or @code{class}, @code{whatis} never prints their
15874 fields or methods. It just prints the @code{struct}/@code{class}
15875 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
15876 such a compound data type, use @code{ptype}.
15878 If @var{arg} is a type name that was defined using @code{typedef},
15879 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
15880 Unrolling means that @code{whatis} will show the underlying type used
15881 in the @code{typedef} declaration of @var{arg}. However, if that
15882 underlying type is also a @code{typedef}, @code{whatis} will not
15885 For C code, the type names may also have the form @samp{class
15886 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
15887 @var{union-tag}} or @samp{enum @var{enum-tag}}.
15889 @var{flags} can be used to modify how the type is displayed.
15890 Available flags are:
15894 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
15895 parameters and typedefs defined in a class when printing the class'
15896 members. The @code{/r} flag disables this.
15899 Do not print methods defined in the class.
15902 Print methods defined in the class. This is the default, but the flag
15903 exists in case you change the default with @command{set print type methods}.
15906 Do not print typedefs defined in the class. Note that this controls
15907 whether the typedef definition itself is printed, not whether typedef
15908 names are substituted when printing other types.
15911 Print typedefs defined in the class. This is the default, but the flag
15912 exists in case you change the default with @command{set print type typedefs}.
15916 @item ptype[/@var{flags}] [@var{arg}]
15917 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
15918 detailed description of the type, instead of just the name of the type.
15919 @xref{Expressions, ,Expressions}.
15921 Contrary to @code{whatis}, @code{ptype} always unrolls any
15922 @code{typedef}s in its argument declaration, whether the argument is
15923 a variable, expression, or a data type. This means that @code{ptype}
15924 of a variable or an expression will not print literally its type as
15925 present in the source code---use @code{whatis} for that. @code{typedef}s at
15926 the pointer or reference targets are also unrolled. Only @code{typedef}s of
15927 fields, methods and inner @code{class typedef}s of @code{struct}s,
15928 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
15930 For example, for this variable declaration:
15933 typedef double real_t;
15934 struct complex @{ real_t real; double imag; @};
15935 typedef struct complex complex_t;
15937 real_t *real_pointer_var;
15941 the two commands give this output:
15945 (@value{GDBP}) whatis var
15947 (@value{GDBP}) ptype var
15948 type = struct complex @{
15952 (@value{GDBP}) whatis complex_t
15953 type = struct complex
15954 (@value{GDBP}) whatis struct complex
15955 type = struct complex
15956 (@value{GDBP}) ptype struct complex
15957 type = struct complex @{
15961 (@value{GDBP}) whatis real_pointer_var
15963 (@value{GDBP}) ptype real_pointer_var
15969 As with @code{whatis}, using @code{ptype} without an argument refers to
15970 the type of @code{$}, the last value in the value history.
15972 @cindex incomplete type
15973 Sometimes, programs use opaque data types or incomplete specifications
15974 of complex data structure. If the debug information included in the
15975 program does not allow @value{GDBN} to display a full declaration of
15976 the data type, it will say @samp{<incomplete type>}. For example,
15977 given these declarations:
15981 struct foo *fooptr;
15985 but no definition for @code{struct foo} itself, @value{GDBN} will say:
15988 (@value{GDBP}) ptype foo
15989 $1 = <incomplete type>
15993 ``Incomplete type'' is C terminology for data types that are not
15994 completely specified.
15997 @item info types @var{regexp}
15999 Print a brief description of all types whose names match the regular
16000 expression @var{regexp} (or all types in your program, if you supply
16001 no argument). Each complete typename is matched as though it were a
16002 complete line; thus, @samp{i type value} gives information on all
16003 types in your program whose names include the string @code{value}, but
16004 @samp{i type ^value$} gives information only on types whose complete
16005 name is @code{value}.
16007 This command differs from @code{ptype} in two ways: first, like
16008 @code{whatis}, it does not print a detailed description; second, it
16009 lists all source files where a type is defined.
16011 @kindex info type-printers
16012 @item info type-printers
16013 Versions of @value{GDBN} that ship with Python scripting enabled may
16014 have ``type printers'' available. When using @command{ptype} or
16015 @command{whatis}, these printers are consulted when the name of a type
16016 is needed. @xref{Type Printing API}, for more information on writing
16019 @code{info type-printers} displays all the available type printers.
16021 @kindex enable type-printer
16022 @kindex disable type-printer
16023 @item enable type-printer @var{name}@dots{}
16024 @item disable type-printer @var{name}@dots{}
16025 These commands can be used to enable or disable type printers.
16028 @cindex local variables
16029 @item info scope @var{location}
16030 List all the variables local to a particular scope. This command
16031 accepts a @var{location} argument---a function name, a source line, or
16032 an address preceded by a @samp{*}, and prints all the variables local
16033 to the scope defined by that location. (@xref{Specify Location}, for
16034 details about supported forms of @var{location}.) For example:
16037 (@value{GDBP}) @b{info scope command_line_handler}
16038 Scope for command_line_handler:
16039 Symbol rl is an argument at stack/frame offset 8, length 4.
16040 Symbol linebuffer is in static storage at address 0x150a18, length 4.
16041 Symbol linelength is in static storage at address 0x150a1c, length 4.
16042 Symbol p is a local variable in register $esi, length 4.
16043 Symbol p1 is a local variable in register $ebx, length 4.
16044 Symbol nline is a local variable in register $edx, length 4.
16045 Symbol repeat is a local variable at frame offset -8, length 4.
16049 This command is especially useful for determining what data to collect
16050 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
16053 @kindex info source
16055 Show information about the current source file---that is, the source file for
16056 the function containing the current point of execution:
16059 the name of the source file, and the directory containing it,
16061 the directory it was compiled in,
16063 its length, in lines,
16065 which programming language it is written in,
16067 whether the executable includes debugging information for that file, and
16068 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
16070 whether the debugging information includes information about
16071 preprocessor macros.
16075 @kindex info sources
16077 Print the names of all source files in your program for which there is
16078 debugging information, organized into two lists: files whose symbols
16079 have already been read, and files whose symbols will be read when needed.
16081 @kindex info functions
16082 @item info functions
16083 Print the names and data types of all defined functions.
16085 @item info functions @var{regexp}
16086 Print the names and data types of all defined functions
16087 whose names contain a match for regular expression @var{regexp}.
16088 Thus, @samp{info fun step} finds all functions whose names
16089 include @code{step}; @samp{info fun ^step} finds those whose names
16090 start with @code{step}. If a function name contains characters
16091 that conflict with the regular expression language (e.g.@:
16092 @samp{operator*()}), they may be quoted with a backslash.
16094 @kindex info variables
16095 @item info variables
16096 Print the names and data types of all variables that are defined
16097 outside of functions (i.e.@: excluding local variables).
16099 @item info variables @var{regexp}
16100 Print the names and data types of all variables (except for local
16101 variables) whose names contain a match for regular expression
16104 @kindex info classes
16105 @cindex Objective-C, classes and selectors
16107 @itemx info classes @var{regexp}
16108 Display all Objective-C classes in your program, or
16109 (with the @var{regexp} argument) all those matching a particular regular
16112 @kindex info selectors
16113 @item info selectors
16114 @itemx info selectors @var{regexp}
16115 Display all Objective-C selectors in your program, or
16116 (with the @var{regexp} argument) all those matching a particular regular
16120 This was never implemented.
16121 @kindex info methods
16123 @itemx info methods @var{regexp}
16124 The @code{info methods} command permits the user to examine all defined
16125 methods within C@t{++} program, or (with the @var{regexp} argument) a
16126 specific set of methods found in the various C@t{++} classes. Many
16127 C@t{++} classes provide a large number of methods. Thus, the output
16128 from the @code{ptype} command can be overwhelming and hard to use. The
16129 @code{info-methods} command filters the methods, printing only those
16130 which match the regular-expression @var{regexp}.
16133 @cindex opaque data types
16134 @kindex set opaque-type-resolution
16135 @item set opaque-type-resolution on
16136 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
16137 declared as a pointer to a @code{struct}, @code{class}, or
16138 @code{union}---for example, @code{struct MyType *}---that is used in one
16139 source file although the full declaration of @code{struct MyType} is in
16140 another source file. The default is on.
16142 A change in the setting of this subcommand will not take effect until
16143 the next time symbols for a file are loaded.
16145 @item set opaque-type-resolution off
16146 Tell @value{GDBN} not to resolve opaque types. In this case, the type
16147 is printed as follows:
16149 @{<no data fields>@}
16152 @kindex show opaque-type-resolution
16153 @item show opaque-type-resolution
16154 Show whether opaque types are resolved or not.
16156 @kindex maint print symbols
16157 @cindex symbol dump
16158 @kindex maint print psymbols
16159 @cindex partial symbol dump
16160 @kindex maint print msymbols
16161 @cindex minimal symbol dump
16162 @item maint print symbols @var{filename}
16163 @itemx maint print psymbols @var{filename}
16164 @itemx maint print msymbols @var{filename}
16165 Write a dump of debugging symbol data into the file @var{filename}.
16166 These commands are used to debug the @value{GDBN} symbol-reading code. Only
16167 symbols with debugging data are included. If you use @samp{maint print
16168 symbols}, @value{GDBN} includes all the symbols for which it has already
16169 collected full details: that is, @var{filename} reflects symbols for
16170 only those files whose symbols @value{GDBN} has read. You can use the
16171 command @code{info sources} to find out which files these are. If you
16172 use @samp{maint print psymbols} instead, the dump shows information about
16173 symbols that @value{GDBN} only knows partially---that is, symbols defined in
16174 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
16175 @samp{maint print msymbols} dumps just the minimal symbol information
16176 required for each object file from which @value{GDBN} has read some symbols.
16177 @xref{Files, ,Commands to Specify Files}, for a discussion of how
16178 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
16180 @kindex maint info symtabs
16181 @kindex maint info psymtabs
16182 @cindex listing @value{GDBN}'s internal symbol tables
16183 @cindex symbol tables, listing @value{GDBN}'s internal
16184 @cindex full symbol tables, listing @value{GDBN}'s internal
16185 @cindex partial symbol tables, listing @value{GDBN}'s internal
16186 @item maint info symtabs @r{[} @var{regexp} @r{]}
16187 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
16189 List the @code{struct symtab} or @code{struct partial_symtab}
16190 structures whose names match @var{regexp}. If @var{regexp} is not
16191 given, list them all. The output includes expressions which you can
16192 copy into a @value{GDBN} debugging this one to examine a particular
16193 structure in more detail. For example:
16196 (@value{GDBP}) maint info psymtabs dwarf2read
16197 @{ objfile /home/gnu/build/gdb/gdb
16198 ((struct objfile *) 0x82e69d0)
16199 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
16200 ((struct partial_symtab *) 0x8474b10)
16203 text addresses 0x814d3c8 -- 0x8158074
16204 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
16205 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
16206 dependencies (none)
16209 (@value{GDBP}) maint info symtabs
16213 We see that there is one partial symbol table whose filename contains
16214 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
16215 and we see that @value{GDBN} has not read in any symtabs yet at all.
16216 If we set a breakpoint on a function, that will cause @value{GDBN} to
16217 read the symtab for the compilation unit containing that function:
16220 (@value{GDBP}) break dwarf2_psymtab_to_symtab
16221 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
16223 (@value{GDBP}) maint info symtabs
16224 @{ objfile /home/gnu/build/gdb/gdb
16225 ((struct objfile *) 0x82e69d0)
16226 @{ symtab /home/gnu/src/gdb/dwarf2read.c
16227 ((struct symtab *) 0x86c1f38)
16230 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
16231 linetable ((struct linetable *) 0x8370fa0)
16232 debugformat DWARF 2
16241 @chapter Altering Execution
16243 Once you think you have found an error in your program, you might want to
16244 find out for certain whether correcting the apparent error would lead to
16245 correct results in the rest of the run. You can find the answer by
16246 experiment, using the @value{GDBN} features for altering execution of the
16249 For example, you can store new values into variables or memory
16250 locations, give your program a signal, restart it at a different
16251 address, or even return prematurely from a function.
16254 * Assignment:: Assignment to variables
16255 * Jumping:: Continuing at a different address
16256 * Signaling:: Giving your program a signal
16257 * Returning:: Returning from a function
16258 * Calling:: Calling your program's functions
16259 * Patching:: Patching your program
16263 @section Assignment to Variables
16266 @cindex setting variables
16267 To alter the value of a variable, evaluate an assignment expression.
16268 @xref{Expressions, ,Expressions}. For example,
16275 stores the value 4 into the variable @code{x}, and then prints the
16276 value of the assignment expression (which is 4).
16277 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
16278 information on operators in supported languages.
16280 @kindex set variable
16281 @cindex variables, setting
16282 If you are not interested in seeing the value of the assignment, use the
16283 @code{set} command instead of the @code{print} command. @code{set} is
16284 really the same as @code{print} except that the expression's value is
16285 not printed and is not put in the value history (@pxref{Value History,
16286 ,Value History}). The expression is evaluated only for its effects.
16288 If the beginning of the argument string of the @code{set} command
16289 appears identical to a @code{set} subcommand, use the @code{set
16290 variable} command instead of just @code{set}. This command is identical
16291 to @code{set} except for its lack of subcommands. For example, if your
16292 program has a variable @code{width}, you get an error if you try to set
16293 a new value with just @samp{set width=13}, because @value{GDBN} has the
16294 command @code{set width}:
16297 (@value{GDBP}) whatis width
16299 (@value{GDBP}) p width
16301 (@value{GDBP}) set width=47
16302 Invalid syntax in expression.
16306 The invalid expression, of course, is @samp{=47}. In
16307 order to actually set the program's variable @code{width}, use
16310 (@value{GDBP}) set var width=47
16313 Because the @code{set} command has many subcommands that can conflict
16314 with the names of program variables, it is a good idea to use the
16315 @code{set variable} command instead of just @code{set}. For example, if
16316 your program has a variable @code{g}, you run into problems if you try
16317 to set a new value with just @samp{set g=4}, because @value{GDBN} has
16318 the command @code{set gnutarget}, abbreviated @code{set g}:
16322 (@value{GDBP}) whatis g
16326 (@value{GDBP}) set g=4
16330 The program being debugged has been started already.
16331 Start it from the beginning? (y or n) y
16332 Starting program: /home/smith/cc_progs/a.out
16333 "/home/smith/cc_progs/a.out": can't open to read symbols:
16334 Invalid bfd target.
16335 (@value{GDBP}) show g
16336 The current BFD target is "=4".
16341 The program variable @code{g} did not change, and you silently set the
16342 @code{gnutarget} to an invalid value. In order to set the variable
16346 (@value{GDBP}) set var g=4
16349 @value{GDBN} allows more implicit conversions in assignments than C; you can
16350 freely store an integer value into a pointer variable or vice versa,
16351 and you can convert any structure to any other structure that is the
16352 same length or shorter.
16353 @comment FIXME: how do structs align/pad in these conversions?
16354 @comment /doc@cygnus.com 18dec1990
16356 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
16357 construct to generate a value of specified type at a specified address
16358 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
16359 to memory location @code{0x83040} as an integer (which implies a certain size
16360 and representation in memory), and
16363 set @{int@}0x83040 = 4
16367 stores the value 4 into that memory location.
16370 @section Continuing at a Different Address
16372 Ordinarily, when you continue your program, you do so at the place where
16373 it stopped, with the @code{continue} command. You can instead continue at
16374 an address of your own choosing, with the following commands:
16378 @kindex j @r{(@code{jump})}
16379 @item jump @var{linespec}
16380 @itemx j @var{linespec}
16381 @itemx jump @var{location}
16382 @itemx j @var{location}
16383 Resume execution at line @var{linespec} or at address given by
16384 @var{location}. Execution stops again immediately if there is a
16385 breakpoint there. @xref{Specify Location}, for a description of the
16386 different forms of @var{linespec} and @var{location}. It is common
16387 practice to use the @code{tbreak} command in conjunction with
16388 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
16390 The @code{jump} command does not change the current stack frame, or
16391 the stack pointer, or the contents of any memory location or any
16392 register other than the program counter. If line @var{linespec} is in
16393 a different function from the one currently executing, the results may
16394 be bizarre if the two functions expect different patterns of arguments or
16395 of local variables. For this reason, the @code{jump} command requests
16396 confirmation if the specified line is not in the function currently
16397 executing. However, even bizarre results are predictable if you are
16398 well acquainted with the machine-language code of your program.
16401 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
16402 On many systems, you can get much the same effect as the @code{jump}
16403 command by storing a new value into the register @code{$pc}. The
16404 difference is that this does not start your program running; it only
16405 changes the address of where it @emph{will} run when you continue. For
16413 makes the next @code{continue} command or stepping command execute at
16414 address @code{0x485}, rather than at the address where your program stopped.
16415 @xref{Continuing and Stepping, ,Continuing and Stepping}.
16417 The most common occasion to use the @code{jump} command is to back
16418 up---perhaps with more breakpoints set---over a portion of a program
16419 that has already executed, in order to examine its execution in more
16424 @section Giving your Program a Signal
16425 @cindex deliver a signal to a program
16429 @item signal @var{signal}
16430 Resume execution where your program stopped, but immediately give it the
16431 signal @var{signal}. @var{signal} can be the name or the number of a
16432 signal. For example, on many systems @code{signal 2} and @code{signal
16433 SIGINT} are both ways of sending an interrupt signal.
16435 Alternatively, if @var{signal} is zero, continue execution without
16436 giving a signal. This is useful when your program stopped on account of
16437 a signal and would ordinarily see the signal when resumed with the
16438 @code{continue} command; @samp{signal 0} causes it to resume without a
16441 @code{signal} does not repeat when you press @key{RET} a second time
16442 after executing the command.
16446 Invoking the @code{signal} command is not the same as invoking the
16447 @code{kill} utility from the shell. Sending a signal with @code{kill}
16448 causes @value{GDBN} to decide what to do with the signal depending on
16449 the signal handling tables (@pxref{Signals}). The @code{signal} command
16450 passes the signal directly to your program.
16454 @section Returning from a Function
16457 @cindex returning from a function
16460 @itemx return @var{expression}
16461 You can cancel execution of a function call with the @code{return}
16462 command. If you give an
16463 @var{expression} argument, its value is used as the function's return
16467 When you use @code{return}, @value{GDBN} discards the selected stack frame
16468 (and all frames within it). You can think of this as making the
16469 discarded frame return prematurely. If you wish to specify a value to
16470 be returned, give that value as the argument to @code{return}.
16472 This pops the selected stack frame (@pxref{Selection, ,Selecting a
16473 Frame}), and any other frames inside of it, leaving its caller as the
16474 innermost remaining frame. That frame becomes selected. The
16475 specified value is stored in the registers used for returning values
16478 The @code{return} command does not resume execution; it leaves the
16479 program stopped in the state that would exist if the function had just
16480 returned. In contrast, the @code{finish} command (@pxref{Continuing
16481 and Stepping, ,Continuing and Stepping}) resumes execution until the
16482 selected stack frame returns naturally.
16484 @value{GDBN} needs to know how the @var{expression} argument should be set for
16485 the inferior. The concrete registers assignment depends on the OS ABI and the
16486 type being returned by the selected stack frame. For example it is common for
16487 OS ABI to return floating point values in FPU registers while integer values in
16488 CPU registers. Still some ABIs return even floating point values in CPU
16489 registers. Larger integer widths (such as @code{long long int}) also have
16490 specific placement rules. @value{GDBN} already knows the OS ABI from its
16491 current target so it needs to find out also the type being returned to make the
16492 assignment into the right register(s).
16494 Normally, the selected stack frame has debug info. @value{GDBN} will always
16495 use the debug info instead of the implicit type of @var{expression} when the
16496 debug info is available. For example, if you type @kbd{return -1}, and the
16497 function in the current stack frame is declared to return a @code{long long
16498 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
16499 into a @code{long long int}:
16502 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
16504 (@value{GDBP}) return -1
16505 Make func return now? (y or n) y
16506 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
16507 43 printf ("result=%lld\n", func ());
16511 However, if the selected stack frame does not have a debug info, e.g., if the
16512 function was compiled without debug info, @value{GDBN} has to find out the type
16513 to return from user. Specifying a different type by mistake may set the value
16514 in different inferior registers than the caller code expects. For example,
16515 typing @kbd{return -1} with its implicit type @code{int} would set only a part
16516 of a @code{long long int} result for a debug info less function (on 32-bit
16517 architectures). Therefore the user is required to specify the return type by
16518 an appropriate cast explicitly:
16521 Breakpoint 2, 0x0040050b in func ()
16522 (@value{GDBP}) return -1
16523 Return value type not available for selected stack frame.
16524 Please use an explicit cast of the value to return.
16525 (@value{GDBP}) return (long long int) -1
16526 Make selected stack frame return now? (y or n) y
16527 #0 0x00400526 in main ()
16532 @section Calling Program Functions
16535 @cindex calling functions
16536 @cindex inferior functions, calling
16537 @item print @var{expr}
16538 Evaluate the expression @var{expr} and display the resulting value.
16539 @var{expr} may include calls to functions in the program being
16543 @item call @var{expr}
16544 Evaluate the expression @var{expr} without displaying @code{void}
16547 You can use this variant of the @code{print} command if you want to
16548 execute a function from your program that does not return anything
16549 (a.k.a.@: @dfn{a void function}), but without cluttering the output
16550 with @code{void} returned values that @value{GDBN} will otherwise
16551 print. If the result is not void, it is printed and saved in the
16555 It is possible for the function you call via the @code{print} or
16556 @code{call} command to generate a signal (e.g., if there's a bug in
16557 the function, or if you passed it incorrect arguments). What happens
16558 in that case is controlled by the @code{set unwindonsignal} command.
16560 Similarly, with a C@t{++} program it is possible for the function you
16561 call via the @code{print} or @code{call} command to generate an
16562 exception that is not handled due to the constraints of the dummy
16563 frame. In this case, any exception that is raised in the frame, but has
16564 an out-of-frame exception handler will not be found. GDB builds a
16565 dummy-frame for the inferior function call, and the unwinder cannot
16566 seek for exception handlers outside of this dummy-frame. What happens
16567 in that case is controlled by the
16568 @code{set unwind-on-terminating-exception} command.
16571 @item set unwindonsignal
16572 @kindex set unwindonsignal
16573 @cindex unwind stack in called functions
16574 @cindex call dummy stack unwinding
16575 Set unwinding of the stack if a signal is received while in a function
16576 that @value{GDBN} called in the program being debugged. If set to on,
16577 @value{GDBN} unwinds the stack it created for the call and restores
16578 the context to what it was before the call. If set to off (the
16579 default), @value{GDBN} stops in the frame where the signal was
16582 @item show unwindonsignal
16583 @kindex show unwindonsignal
16584 Show the current setting of stack unwinding in the functions called by
16587 @item set unwind-on-terminating-exception
16588 @kindex set unwind-on-terminating-exception
16589 @cindex unwind stack in called functions with unhandled exceptions
16590 @cindex call dummy stack unwinding on unhandled exception.
16591 Set unwinding of the stack if a C@t{++} exception is raised, but left
16592 unhandled while in a function that @value{GDBN} called in the program being
16593 debugged. If set to on (the default), @value{GDBN} unwinds the stack
16594 it created for the call and restores the context to what it was before
16595 the call. If set to off, @value{GDBN} the exception is delivered to
16596 the default C@t{++} exception handler and the inferior terminated.
16598 @item show unwind-on-terminating-exception
16599 @kindex show unwind-on-terminating-exception
16600 Show the current setting of stack unwinding in the functions called by
16605 @cindex weak alias functions
16606 Sometimes, a function you wish to call is actually a @dfn{weak alias}
16607 for another function. In such case, @value{GDBN} might not pick up
16608 the type information, including the types of the function arguments,
16609 which causes @value{GDBN} to call the inferior function incorrectly.
16610 As a result, the called function will function erroneously and may
16611 even crash. A solution to that is to use the name of the aliased
16615 @section Patching Programs
16617 @cindex patching binaries
16618 @cindex writing into executables
16619 @cindex writing into corefiles
16621 By default, @value{GDBN} opens the file containing your program's
16622 executable code (or the corefile) read-only. This prevents accidental
16623 alterations to machine code; but it also prevents you from intentionally
16624 patching your program's binary.
16626 If you'd like to be able to patch the binary, you can specify that
16627 explicitly with the @code{set write} command. For example, you might
16628 want to turn on internal debugging flags, or even to make emergency
16634 @itemx set write off
16635 If you specify @samp{set write on}, @value{GDBN} opens executable and
16636 core files for both reading and writing; if you specify @kbd{set write
16637 off} (the default), @value{GDBN} opens them read-only.
16639 If you have already loaded a file, you must load it again (using the
16640 @code{exec-file} or @code{core-file} command) after changing @code{set
16641 write}, for your new setting to take effect.
16645 Display whether executable files and core files are opened for writing
16646 as well as reading.
16650 @chapter @value{GDBN} Files
16652 @value{GDBN} needs to know the file name of the program to be debugged,
16653 both in order to read its symbol table and in order to start your
16654 program. To debug a core dump of a previous run, you must also tell
16655 @value{GDBN} the name of the core dump file.
16658 * Files:: Commands to specify files
16659 * Separate Debug Files:: Debugging information in separate files
16660 * MiniDebugInfo:: Debugging information in a special section
16661 * Index Files:: Index files speed up GDB
16662 * Symbol Errors:: Errors reading symbol files
16663 * Data Files:: GDB data files
16667 @section Commands to Specify Files
16669 @cindex symbol table
16670 @cindex core dump file
16672 You may want to specify executable and core dump file names. The usual
16673 way to do this is at start-up time, using the arguments to
16674 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
16675 Out of @value{GDBN}}).
16677 Occasionally it is necessary to change to a different file during a
16678 @value{GDBN} session. Or you may run @value{GDBN} and forget to
16679 specify a file you want to use. Or you are debugging a remote target
16680 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
16681 Program}). In these situations the @value{GDBN} commands to specify
16682 new files are useful.
16685 @cindex executable file
16687 @item file @var{filename}
16688 Use @var{filename} as the program to be debugged. It is read for its
16689 symbols and for the contents of pure memory. It is also the program
16690 executed when you use the @code{run} command. If you do not specify a
16691 directory and the file is not found in the @value{GDBN} working directory,
16692 @value{GDBN} uses the environment variable @code{PATH} as a list of
16693 directories to search, just as the shell does when looking for a program
16694 to run. You can change the value of this variable, for both @value{GDBN}
16695 and your program, using the @code{path} command.
16697 @cindex unlinked object files
16698 @cindex patching object files
16699 You can load unlinked object @file{.o} files into @value{GDBN} using
16700 the @code{file} command. You will not be able to ``run'' an object
16701 file, but you can disassemble functions and inspect variables. Also,
16702 if the underlying BFD functionality supports it, you could use
16703 @kbd{gdb -write} to patch object files using this technique. Note
16704 that @value{GDBN} can neither interpret nor modify relocations in this
16705 case, so branches and some initialized variables will appear to go to
16706 the wrong place. But this feature is still handy from time to time.
16709 @code{file} with no argument makes @value{GDBN} discard any information it
16710 has on both executable file and the symbol table.
16713 @item exec-file @r{[} @var{filename} @r{]}
16714 Specify that the program to be run (but not the symbol table) is found
16715 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
16716 if necessary to locate your program. Omitting @var{filename} means to
16717 discard information on the executable file.
16719 @kindex symbol-file
16720 @item symbol-file @r{[} @var{filename} @r{]}
16721 Read symbol table information from file @var{filename}. @code{PATH} is
16722 searched when necessary. Use the @code{file} command to get both symbol
16723 table and program to run from the same file.
16725 @code{symbol-file} with no argument clears out @value{GDBN} information on your
16726 program's symbol table.
16728 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
16729 some breakpoints and auto-display expressions. This is because they may
16730 contain pointers to the internal data recording symbols and data types,
16731 which are part of the old symbol table data being discarded inside
16734 @code{symbol-file} does not repeat if you press @key{RET} again after
16737 When @value{GDBN} is configured for a particular environment, it
16738 understands debugging information in whatever format is the standard
16739 generated for that environment; you may use either a @sc{gnu} compiler, or
16740 other compilers that adhere to the local conventions.
16741 Best results are usually obtained from @sc{gnu} compilers; for example,
16742 using @code{@value{NGCC}} you can generate debugging information for
16745 For most kinds of object files, with the exception of old SVR3 systems
16746 using COFF, the @code{symbol-file} command does not normally read the
16747 symbol table in full right away. Instead, it scans the symbol table
16748 quickly to find which source files and which symbols are present. The
16749 details are read later, one source file at a time, as they are needed.
16751 The purpose of this two-stage reading strategy is to make @value{GDBN}
16752 start up faster. For the most part, it is invisible except for
16753 occasional pauses while the symbol table details for a particular source
16754 file are being read. (The @code{set verbose} command can turn these
16755 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
16756 Warnings and Messages}.)
16758 We have not implemented the two-stage strategy for COFF yet. When the
16759 symbol table is stored in COFF format, @code{symbol-file} reads the
16760 symbol table data in full right away. Note that ``stabs-in-COFF''
16761 still does the two-stage strategy, since the debug info is actually
16765 @cindex reading symbols immediately
16766 @cindex symbols, reading immediately
16767 @item symbol-file @r{[} -readnow @r{]} @var{filename}
16768 @itemx file @r{[} -readnow @r{]} @var{filename}
16769 You can override the @value{GDBN} two-stage strategy for reading symbol
16770 tables by using the @samp{-readnow} option with any of the commands that
16771 load symbol table information, if you want to be sure @value{GDBN} has the
16772 entire symbol table available.
16774 @c FIXME: for now no mention of directories, since this seems to be in
16775 @c flux. 13mar1992 status is that in theory GDB would look either in
16776 @c current dir or in same dir as myprog; but issues like competing
16777 @c GDB's, or clutter in system dirs, mean that in practice right now
16778 @c only current dir is used. FFish says maybe a special GDB hierarchy
16779 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
16783 @item core-file @r{[}@var{filename}@r{]}
16785 Specify the whereabouts of a core dump file to be used as the ``contents
16786 of memory''. Traditionally, core files contain only some parts of the
16787 address space of the process that generated them; @value{GDBN} can access the
16788 executable file itself for other parts.
16790 @code{core-file} with no argument specifies that no core file is
16793 Note that the core file is ignored when your program is actually running
16794 under @value{GDBN}. So, if you have been running your program and you
16795 wish to debug a core file instead, you must kill the subprocess in which
16796 the program is running. To do this, use the @code{kill} command
16797 (@pxref{Kill Process, ,Killing the Child Process}).
16799 @kindex add-symbol-file
16800 @cindex dynamic linking
16801 @item add-symbol-file @var{filename} @var{address}
16802 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
16803 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
16804 The @code{add-symbol-file} command reads additional symbol table
16805 information from the file @var{filename}. You would use this command
16806 when @var{filename} has been dynamically loaded (by some other means)
16807 into the program that is running. @var{address} should be the memory
16808 address at which the file has been loaded; @value{GDBN} cannot figure
16809 this out for itself. You can additionally specify an arbitrary number
16810 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
16811 section name and base address for that section. You can specify any
16812 @var{address} as an expression.
16814 The symbol table of the file @var{filename} is added to the symbol table
16815 originally read with the @code{symbol-file} command. You can use the
16816 @code{add-symbol-file} command any number of times; the new symbol data
16817 thus read is kept in addition to the old.
16819 Changes can be reverted using the command @code{remove-symbol-file}.
16821 @cindex relocatable object files, reading symbols from
16822 @cindex object files, relocatable, reading symbols from
16823 @cindex reading symbols from relocatable object files
16824 @cindex symbols, reading from relocatable object files
16825 @cindex @file{.o} files, reading symbols from
16826 Although @var{filename} is typically a shared library file, an
16827 executable file, or some other object file which has been fully
16828 relocated for loading into a process, you can also load symbolic
16829 information from relocatable @file{.o} files, as long as:
16833 the file's symbolic information refers only to linker symbols defined in
16834 that file, not to symbols defined by other object files,
16836 every section the file's symbolic information refers to has actually
16837 been loaded into the inferior, as it appears in the file, and
16839 you can determine the address at which every section was loaded, and
16840 provide these to the @code{add-symbol-file} command.
16844 Some embedded operating systems, like Sun Chorus and VxWorks, can load
16845 relocatable files into an already running program; such systems
16846 typically make the requirements above easy to meet. However, it's
16847 important to recognize that many native systems use complex link
16848 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
16849 assembly, for example) that make the requirements difficult to meet. In
16850 general, one cannot assume that using @code{add-symbol-file} to read a
16851 relocatable object file's symbolic information will have the same effect
16852 as linking the relocatable object file into the program in the normal
16855 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
16857 @kindex remove-symbol-file
16858 @item remove-symbol-file @var{filename}
16859 @item remove-symbol-file -a @var{address}
16860 Remove a symbol file added via the @code{add-symbol-file} command. The
16861 file to remove can be identified by its @var{filename} or by an @var{address}
16862 that lies within the boundaries of this symbol file in memory. Example:
16865 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
16866 add symbol table from file "/home/user/gdb/mylib.so" at
16867 .text_addr = 0x7ffff7ff9480
16869 Reading symbols from /home/user/gdb/mylib.so...done.
16870 (gdb) remove-symbol-file -a 0x7ffff7ff9480
16871 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
16876 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
16878 @kindex add-symbol-file-from-memory
16879 @cindex @code{syscall DSO}
16880 @cindex load symbols from memory
16881 @item add-symbol-file-from-memory @var{address}
16882 Load symbols from the given @var{address} in a dynamically loaded
16883 object file whose image is mapped directly into the inferior's memory.
16884 For example, the Linux kernel maps a @code{syscall DSO} into each
16885 process's address space; this DSO provides kernel-specific code for
16886 some system calls. The argument can be any expression whose
16887 evaluation yields the address of the file's shared object file header.
16888 For this command to work, you must have used @code{symbol-file} or
16889 @code{exec-file} commands in advance.
16891 @kindex add-shared-symbol-files
16893 @item add-shared-symbol-files @var{library-file}
16894 @itemx assf @var{library-file}
16895 The @code{add-shared-symbol-files} command can currently be used only
16896 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
16897 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
16898 @value{GDBN} automatically looks for shared libraries, however if
16899 @value{GDBN} does not find yours, you can invoke
16900 @code{add-shared-symbol-files}. It takes one argument: the shared
16901 library's file name. @code{assf} is a shorthand alias for
16902 @code{add-shared-symbol-files}.
16905 @item section @var{section} @var{addr}
16906 The @code{section} command changes the base address of the named
16907 @var{section} of the exec file to @var{addr}. This can be used if the
16908 exec file does not contain section addresses, (such as in the
16909 @code{a.out} format), or when the addresses specified in the file
16910 itself are wrong. Each section must be changed separately. The
16911 @code{info files} command, described below, lists all the sections and
16915 @kindex info target
16918 @code{info files} and @code{info target} are synonymous; both print the
16919 current target (@pxref{Targets, ,Specifying a Debugging Target}),
16920 including the names of the executable and core dump files currently in
16921 use by @value{GDBN}, and the files from which symbols were loaded. The
16922 command @code{help target} lists all possible targets rather than
16925 @kindex maint info sections
16926 @item maint info sections
16927 Another command that can give you extra information about program sections
16928 is @code{maint info sections}. In addition to the section information
16929 displayed by @code{info files}, this command displays the flags and file
16930 offset of each section in the executable and core dump files. In addition,
16931 @code{maint info sections} provides the following command options (which
16932 may be arbitrarily combined):
16936 Display sections for all loaded object files, including shared libraries.
16937 @item @var{sections}
16938 Display info only for named @var{sections}.
16939 @item @var{section-flags}
16940 Display info only for sections for which @var{section-flags} are true.
16941 The section flags that @value{GDBN} currently knows about are:
16944 Section will have space allocated in the process when loaded.
16945 Set for all sections except those containing debug information.
16947 Section will be loaded from the file into the child process memory.
16948 Set for pre-initialized code and data, clear for @code{.bss} sections.
16950 Section needs to be relocated before loading.
16952 Section cannot be modified by the child process.
16954 Section contains executable code only.
16956 Section contains data only (no executable code).
16958 Section will reside in ROM.
16960 Section contains data for constructor/destructor lists.
16962 Section is not empty.
16964 An instruction to the linker to not output the section.
16965 @item COFF_SHARED_LIBRARY
16966 A notification to the linker that the section contains
16967 COFF shared library information.
16969 Section contains common symbols.
16972 @kindex set trust-readonly-sections
16973 @cindex read-only sections
16974 @item set trust-readonly-sections on
16975 Tell @value{GDBN} that readonly sections in your object file
16976 really are read-only (i.e.@: that their contents will not change).
16977 In that case, @value{GDBN} can fetch values from these sections
16978 out of the object file, rather than from the target program.
16979 For some targets (notably embedded ones), this can be a significant
16980 enhancement to debugging performance.
16982 The default is off.
16984 @item set trust-readonly-sections off
16985 Tell @value{GDBN} not to trust readonly sections. This means that
16986 the contents of the section might change while the program is running,
16987 and must therefore be fetched from the target when needed.
16989 @item show trust-readonly-sections
16990 Show the current setting of trusting readonly sections.
16993 All file-specifying commands allow both absolute and relative file names
16994 as arguments. @value{GDBN} always converts the file name to an absolute file
16995 name and remembers it that way.
16997 @cindex shared libraries
16998 @anchor{Shared Libraries}
16999 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
17000 and IBM RS/6000 AIX shared libraries.
17002 On MS-Windows @value{GDBN} must be linked with the Expat library to support
17003 shared libraries. @xref{Expat}.
17005 @value{GDBN} automatically loads symbol definitions from shared libraries
17006 when you use the @code{run} command, or when you examine a core file.
17007 (Before you issue the @code{run} command, @value{GDBN} does not understand
17008 references to a function in a shared library, however---unless you are
17009 debugging a core file).
17011 On HP-UX, if the program loads a library explicitly, @value{GDBN}
17012 automatically loads the symbols at the time of the @code{shl_load} call.
17014 @c FIXME: some @value{GDBN} release may permit some refs to undef
17015 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
17016 @c FIXME...lib; check this from time to time when updating manual
17018 There are times, however, when you may wish to not automatically load
17019 symbol definitions from shared libraries, such as when they are
17020 particularly large or there are many of them.
17022 To control the automatic loading of shared library symbols, use the
17026 @kindex set auto-solib-add
17027 @item set auto-solib-add @var{mode}
17028 If @var{mode} is @code{on}, symbols from all shared object libraries
17029 will be loaded automatically when the inferior begins execution, you
17030 attach to an independently started inferior, or when the dynamic linker
17031 informs @value{GDBN} that a new library has been loaded. If @var{mode}
17032 is @code{off}, symbols must be loaded manually, using the
17033 @code{sharedlibrary} command. The default value is @code{on}.
17035 @cindex memory used for symbol tables
17036 If your program uses lots of shared libraries with debug info that
17037 takes large amounts of memory, you can decrease the @value{GDBN}
17038 memory footprint by preventing it from automatically loading the
17039 symbols from shared libraries. To that end, type @kbd{set
17040 auto-solib-add off} before running the inferior, then load each
17041 library whose debug symbols you do need with @kbd{sharedlibrary
17042 @var{regexp}}, where @var{regexp} is a regular expression that matches
17043 the libraries whose symbols you want to be loaded.
17045 @kindex show auto-solib-add
17046 @item show auto-solib-add
17047 Display the current autoloading mode.
17050 @cindex load shared library
17051 To explicitly load shared library symbols, use the @code{sharedlibrary}
17055 @kindex info sharedlibrary
17057 @item info share @var{regex}
17058 @itemx info sharedlibrary @var{regex}
17059 Print the names of the shared libraries which are currently loaded
17060 that match @var{regex}. If @var{regex} is omitted then print
17061 all shared libraries that are loaded.
17063 @kindex sharedlibrary
17065 @item sharedlibrary @var{regex}
17066 @itemx share @var{regex}
17067 Load shared object library symbols for files matching a
17068 Unix regular expression.
17069 As with files loaded automatically, it only loads shared libraries
17070 required by your program for a core file or after typing @code{run}. If
17071 @var{regex} is omitted all shared libraries required by your program are
17074 @item nosharedlibrary
17075 @kindex nosharedlibrary
17076 @cindex unload symbols from shared libraries
17077 Unload all shared object library symbols. This discards all symbols
17078 that have been loaded from all shared libraries. Symbols from shared
17079 libraries that were loaded by explicit user requests are not
17083 Sometimes you may wish that @value{GDBN} stops and gives you control
17084 when any of shared library events happen. The best way to do this is
17085 to use @code{catch load} and @code{catch unload} (@pxref{Set
17088 @value{GDBN} also supports the the @code{set stop-on-solib-events}
17089 command for this. This command exists for historical reasons. It is
17090 less useful than setting a catchpoint, because it does not allow for
17091 conditions or commands as a catchpoint does.
17094 @item set stop-on-solib-events
17095 @kindex set stop-on-solib-events
17096 This command controls whether @value{GDBN} should give you control
17097 when the dynamic linker notifies it about some shared library event.
17098 The most common event of interest is loading or unloading of a new
17101 @item show stop-on-solib-events
17102 @kindex show stop-on-solib-events
17103 Show whether @value{GDBN} stops and gives you control when shared
17104 library events happen.
17107 Shared libraries are also supported in many cross or remote debugging
17108 configurations. @value{GDBN} needs to have access to the target's libraries;
17109 this can be accomplished either by providing copies of the libraries
17110 on the host system, or by asking @value{GDBN} to automatically retrieve the
17111 libraries from the target. If copies of the target libraries are
17112 provided, they need to be the same as the target libraries, although the
17113 copies on the target can be stripped as long as the copies on the host are
17116 @cindex where to look for shared libraries
17117 For remote debugging, you need to tell @value{GDBN} where the target
17118 libraries are, so that it can load the correct copies---otherwise, it
17119 may try to load the host's libraries. @value{GDBN} has two variables
17120 to specify the search directories for target libraries.
17123 @cindex prefix for shared library file names
17124 @cindex system root, alternate
17125 @kindex set solib-absolute-prefix
17126 @kindex set sysroot
17127 @item set sysroot @var{path}
17128 Use @var{path} as the system root for the program being debugged. Any
17129 absolute shared library paths will be prefixed with @var{path}; many
17130 runtime loaders store the absolute paths to the shared library in the
17131 target program's memory. If you use @code{set sysroot} to find shared
17132 libraries, they need to be laid out in the same way that they are on
17133 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
17136 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
17137 retrieve the target libraries from the remote system. This is only
17138 supported when using a remote target that supports the @code{remote get}
17139 command (@pxref{File Transfer,,Sending files to a remote system}).
17140 The part of @var{path} following the initial @file{remote:}
17141 (if present) is used as system root prefix on the remote file system.
17142 @footnote{If you want to specify a local system root using a directory
17143 that happens to be named @file{remote:}, you need to use some equivalent
17144 variant of the name like @file{./remote:}.}
17146 For targets with an MS-DOS based filesystem, such as MS-Windows and
17147 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
17148 absolute file name with @var{path}. But first, on Unix hosts,
17149 @value{GDBN} converts all backslash directory separators into forward
17150 slashes, because the backslash is not a directory separator on Unix:
17153 c:\foo\bar.dll @result{} c:/foo/bar.dll
17156 Then, @value{GDBN} attempts prefixing the target file name with
17157 @var{path}, and looks for the resulting file name in the host file
17161 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
17164 If that does not find the shared library, @value{GDBN} tries removing
17165 the @samp{:} character from the drive spec, both for convenience, and,
17166 for the case of the host file system not supporting file names with
17170 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
17173 This makes it possible to have a system root that mirrors a target
17174 with more than one drive. E.g., you may want to setup your local
17175 copies of the target system shared libraries like so (note @samp{c} vs
17179 @file{/path/to/sysroot/c/sys/bin/foo.dll}
17180 @file{/path/to/sysroot/c/sys/bin/bar.dll}
17181 @file{/path/to/sysroot/z/sys/bin/bar.dll}
17185 and point the system root at @file{/path/to/sysroot}, so that
17186 @value{GDBN} can find the correct copies of both
17187 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
17189 If that still does not find the shared library, @value{GDBN} tries
17190 removing the whole drive spec from the target file name:
17193 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
17196 This last lookup makes it possible to not care about the drive name,
17197 if you don't want or need to.
17199 The @code{set solib-absolute-prefix} command is an alias for @code{set
17202 @cindex default system root
17203 @cindex @samp{--with-sysroot}
17204 You can set the default system root by using the configure-time
17205 @samp{--with-sysroot} option. If the system root is inside
17206 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
17207 @samp{--exec-prefix}), then the default system root will be updated
17208 automatically if the installed @value{GDBN} is moved to a new
17211 @kindex show sysroot
17213 Display the current shared library prefix.
17215 @kindex set solib-search-path
17216 @item set solib-search-path @var{path}
17217 If this variable is set, @var{path} is a colon-separated list of
17218 directories to search for shared libraries. @samp{solib-search-path}
17219 is used after @samp{sysroot} fails to locate the library, or if the
17220 path to the library is relative instead of absolute. If you want to
17221 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
17222 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
17223 finding your host's libraries. @samp{sysroot} is preferred; setting
17224 it to a nonexistent directory may interfere with automatic loading
17225 of shared library symbols.
17227 @kindex show solib-search-path
17228 @item show solib-search-path
17229 Display the current shared library search path.
17231 @cindex DOS file-name semantics of file names.
17232 @kindex set target-file-system-kind (unix|dos-based|auto)
17233 @kindex show target-file-system-kind
17234 @item set target-file-system-kind @var{kind}
17235 Set assumed file system kind for target reported file names.
17237 Shared library file names as reported by the target system may not
17238 make sense as is on the system @value{GDBN} is running on. For
17239 example, when remote debugging a target that has MS-DOS based file
17240 system semantics, from a Unix host, the target may be reporting to
17241 @value{GDBN} a list of loaded shared libraries with file names such as
17242 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
17243 drive letters, so the @samp{c:\} prefix is not normally understood as
17244 indicating an absolute file name, and neither is the backslash
17245 normally considered a directory separator character. In that case,
17246 the native file system would interpret this whole absolute file name
17247 as a relative file name with no directory components. This would make
17248 it impossible to point @value{GDBN} at a copy of the remote target's
17249 shared libraries on the host using @code{set sysroot}, and impractical
17250 with @code{set solib-search-path}. Setting
17251 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
17252 to interpret such file names similarly to how the target would, and to
17253 map them to file names valid on @value{GDBN}'s native file system
17254 semantics. The value of @var{kind} can be @code{"auto"}, in addition
17255 to one of the supported file system kinds. In that case, @value{GDBN}
17256 tries to determine the appropriate file system variant based on the
17257 current target's operating system (@pxref{ABI, ,Configuring the
17258 Current ABI}). The supported file system settings are:
17262 Instruct @value{GDBN} to assume the target file system is of Unix
17263 kind. Only file names starting the forward slash (@samp{/}) character
17264 are considered absolute, and the directory separator character is also
17268 Instruct @value{GDBN} to assume the target file system is DOS based.
17269 File names starting with either a forward slash, or a drive letter
17270 followed by a colon (e.g., @samp{c:}), are considered absolute, and
17271 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
17272 considered directory separators.
17275 Instruct @value{GDBN} to use the file system kind associated with the
17276 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
17277 This is the default.
17281 @cindex file name canonicalization
17282 @cindex base name differences
17283 When processing file names provided by the user, @value{GDBN}
17284 frequently needs to compare them to the file names recorded in the
17285 program's debug info. Normally, @value{GDBN} compares just the
17286 @dfn{base names} of the files as strings, which is reasonably fast
17287 even for very large programs. (The base name of a file is the last
17288 portion of its name, after stripping all the leading directories.)
17289 This shortcut in comparison is based upon the assumption that files
17290 cannot have more than one base name. This is usually true, but
17291 references to files that use symlinks or similar filesystem
17292 facilities violate that assumption. If your program records files
17293 using such facilities, or if you provide file names to @value{GDBN}
17294 using symlinks etc., you can set @code{basenames-may-differ} to
17295 @code{true} to instruct @value{GDBN} to completely canonicalize each
17296 pair of file names it needs to compare. This will make file-name
17297 comparisons accurate, but at a price of a significant slowdown.
17300 @item set basenames-may-differ
17301 @kindex set basenames-may-differ
17302 Set whether a source file may have multiple base names.
17304 @item show basenames-may-differ
17305 @kindex show basenames-may-differ
17306 Show whether a source file may have multiple base names.
17309 @node Separate Debug Files
17310 @section Debugging Information in Separate Files
17311 @cindex separate debugging information files
17312 @cindex debugging information in separate files
17313 @cindex @file{.debug} subdirectories
17314 @cindex debugging information directory, global
17315 @cindex global debugging information directories
17316 @cindex build ID, and separate debugging files
17317 @cindex @file{.build-id} directory
17319 @value{GDBN} allows you to put a program's debugging information in a
17320 file separate from the executable itself, in a way that allows
17321 @value{GDBN} to find and load the debugging information automatically.
17322 Since debugging information can be very large---sometimes larger
17323 than the executable code itself---some systems distribute debugging
17324 information for their executables in separate files, which users can
17325 install only when they need to debug a problem.
17327 @value{GDBN} supports two ways of specifying the separate debug info
17332 The executable contains a @dfn{debug link} that specifies the name of
17333 the separate debug info file. The separate debug file's name is
17334 usually @file{@var{executable}.debug}, where @var{executable} is the
17335 name of the corresponding executable file without leading directories
17336 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
17337 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
17338 checksum for the debug file, which @value{GDBN} uses to validate that
17339 the executable and the debug file came from the same build.
17342 The executable contains a @dfn{build ID}, a unique bit string that is
17343 also present in the corresponding debug info file. (This is supported
17344 only on some operating systems, notably those which use the ELF format
17345 for binary files and the @sc{gnu} Binutils.) For more details about
17346 this feature, see the description of the @option{--build-id}
17347 command-line option in @ref{Options, , Command Line Options, ld.info,
17348 The GNU Linker}. The debug info file's name is not specified
17349 explicitly by the build ID, but can be computed from the build ID, see
17353 Depending on the way the debug info file is specified, @value{GDBN}
17354 uses two different methods of looking for the debug file:
17358 For the ``debug link'' method, @value{GDBN} looks up the named file in
17359 the directory of the executable file, then in a subdirectory of that
17360 directory named @file{.debug}, and finally under each one of the global debug
17361 directories, in a subdirectory whose name is identical to the leading
17362 directories of the executable's absolute file name.
17365 For the ``build ID'' method, @value{GDBN} looks in the
17366 @file{.build-id} subdirectory of each one of the global debug directories for
17367 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
17368 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
17369 are the rest of the bit string. (Real build ID strings are 32 or more
17370 hex characters, not 10.)
17373 So, for example, suppose you ask @value{GDBN} to debug
17374 @file{/usr/bin/ls}, which has a debug link that specifies the
17375 file @file{ls.debug}, and a build ID whose value in hex is
17376 @code{abcdef1234}. If the list of the global debug directories includes
17377 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
17378 debug information files, in the indicated order:
17382 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
17384 @file{/usr/bin/ls.debug}
17386 @file{/usr/bin/.debug/ls.debug}
17388 @file{/usr/lib/debug/usr/bin/ls.debug}.
17391 @anchor{debug-file-directory}
17392 Global debugging info directories default to what is set by @value{GDBN}
17393 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
17394 you can also set the global debugging info directories, and view the list
17395 @value{GDBN} is currently using.
17399 @kindex set debug-file-directory
17400 @item set debug-file-directory @var{directories}
17401 Set the directories which @value{GDBN} searches for separate debugging
17402 information files to @var{directory}. Multiple path components can be set
17403 concatenating them by a path separator.
17405 @kindex show debug-file-directory
17406 @item show debug-file-directory
17407 Show the directories @value{GDBN} searches for separate debugging
17412 @cindex @code{.gnu_debuglink} sections
17413 @cindex debug link sections
17414 A debug link is a special section of the executable file named
17415 @code{.gnu_debuglink}. The section must contain:
17419 A filename, with any leading directory components removed, followed by
17422 zero to three bytes of padding, as needed to reach the next four-byte
17423 boundary within the section, and
17425 a four-byte CRC checksum, stored in the same endianness used for the
17426 executable file itself. The checksum is computed on the debugging
17427 information file's full contents by the function given below, passing
17428 zero as the @var{crc} argument.
17431 Any executable file format can carry a debug link, as long as it can
17432 contain a section named @code{.gnu_debuglink} with the contents
17435 @cindex @code{.note.gnu.build-id} sections
17436 @cindex build ID sections
17437 The build ID is a special section in the executable file (and in other
17438 ELF binary files that @value{GDBN} may consider). This section is
17439 often named @code{.note.gnu.build-id}, but that name is not mandatory.
17440 It contains unique identification for the built files---the ID remains
17441 the same across multiple builds of the same build tree. The default
17442 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
17443 content for the build ID string. The same section with an identical
17444 value is present in the original built binary with symbols, in its
17445 stripped variant, and in the separate debugging information file.
17447 The debugging information file itself should be an ordinary
17448 executable, containing a full set of linker symbols, sections, and
17449 debugging information. The sections of the debugging information file
17450 should have the same names, addresses, and sizes as the original file,
17451 but they need not contain any data---much like a @code{.bss} section
17452 in an ordinary executable.
17454 The @sc{gnu} binary utilities (Binutils) package includes the
17455 @samp{objcopy} utility that can produce
17456 the separated executable / debugging information file pairs using the
17457 following commands:
17460 @kbd{objcopy --only-keep-debug foo foo.debug}
17465 These commands remove the debugging
17466 information from the executable file @file{foo} and place it in the file
17467 @file{foo.debug}. You can use the first, second or both methods to link the
17472 The debug link method needs the following additional command to also leave
17473 behind a debug link in @file{foo}:
17476 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
17479 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
17480 a version of the @code{strip} command such that the command @kbd{strip foo -f
17481 foo.debug} has the same functionality as the two @code{objcopy} commands and
17482 the @code{ln -s} command above, together.
17485 Build ID gets embedded into the main executable using @code{ld --build-id} or
17486 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
17487 compatibility fixes for debug files separation are present in @sc{gnu} binary
17488 utilities (Binutils) package since version 2.18.
17493 @cindex CRC algorithm definition
17494 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
17495 IEEE 802.3 using the polynomial:
17497 @c TexInfo requires naked braces for multi-digit exponents for Tex
17498 @c output, but this causes HTML output to barf. HTML has to be set using
17499 @c raw commands. So we end up having to specify this equation in 2
17504 <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>
17505 + <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
17511 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
17512 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
17516 The function is computed byte at a time, taking the least
17517 significant bit of each byte first. The initial pattern
17518 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
17519 the final result is inverted to ensure trailing zeros also affect the
17522 @emph{Note:} This is the same CRC polynomial as used in handling the
17523 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
17524 , @value{GDBN} Remote Serial Protocol}). However in the
17525 case of the Remote Serial Protocol, the CRC is computed @emph{most}
17526 significant bit first, and the result is not inverted, so trailing
17527 zeros have no effect on the CRC value.
17529 To complete the description, we show below the code of the function
17530 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
17531 initially supplied @code{crc} argument means that an initial call to
17532 this function passing in zero will start computing the CRC using
17535 @kindex gnu_debuglink_crc32
17538 gnu_debuglink_crc32 (unsigned long crc,
17539 unsigned char *buf, size_t len)
17541 static const unsigned long crc32_table[256] =
17543 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
17544 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
17545 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
17546 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
17547 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
17548 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
17549 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
17550 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
17551 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
17552 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
17553 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
17554 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
17555 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
17556 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
17557 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
17558 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
17559 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
17560 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
17561 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
17562 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
17563 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
17564 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
17565 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
17566 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
17567 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
17568 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
17569 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
17570 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
17571 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
17572 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
17573 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
17574 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
17575 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
17576 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
17577 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
17578 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
17579 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
17580 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
17581 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
17582 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
17583 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
17584 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
17585 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
17586 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
17587 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
17588 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
17589 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
17590 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
17591 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
17592 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
17593 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
17596 unsigned char *end;
17598 crc = ~crc & 0xffffffff;
17599 for (end = buf + len; buf < end; ++buf)
17600 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
17601 return ~crc & 0xffffffff;
17606 This computation does not apply to the ``build ID'' method.
17608 @node MiniDebugInfo
17609 @section Debugging information in a special section
17610 @cindex separate debug sections
17611 @cindex @samp{.gnu_debugdata} section
17613 Some systems ship pre-built executables and libraries that have a
17614 special @samp{.gnu_debugdata} section. This feature is called
17615 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
17616 is used to supply extra symbols for backtraces.
17618 The intent of this section is to provide extra minimal debugging
17619 information for use in simple backtraces. It is not intended to be a
17620 replacement for full separate debugging information (@pxref{Separate
17621 Debug Files}). The example below shows the intended use; however,
17622 @value{GDBN} does not currently put restrictions on what sort of
17623 debugging information might be included in the section.
17625 @value{GDBN} has support for this extension. If the section exists,
17626 then it is used provided that no other source of debugging information
17627 can be found, and that @value{GDBN} was configured with LZMA support.
17629 This section can be easily created using @command{objcopy} and other
17630 standard utilities:
17633 # Extract the dynamic symbols from the main binary, there is no need
17634 # to also have these in the normal symbol table.
17635 nm -D @var{binary} --format=posix --defined-only \
17636 | awk '@{ print $1 @}' | sort > dynsyms
17638 # Extract all the text (i.e. function) symbols from the debuginfo.
17639 # (Note that we actually also accept "D" symbols, for the benefit
17640 # of platforms like PowerPC64 that use function descriptors.)
17641 nm @var{binary} --format=posix --defined-only \
17642 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
17645 # Keep all the function symbols not already in the dynamic symbol
17647 comm -13 dynsyms funcsyms > keep_symbols
17649 # Separate full debug info into debug binary.
17650 objcopy --only-keep-debug @var{binary} debug
17652 # Copy the full debuginfo, keeping only a minimal set of symbols and
17653 # removing some unnecessary sections.
17654 objcopy -S --remove-section .gdb_index --remove-section .comment \
17655 --keep-symbols=keep_symbols debug mini_debuginfo
17657 # Drop the full debug info from the original binary.
17658 strip --strip-all -R .comment @var{binary}
17660 # Inject the compressed data into the .gnu_debugdata section of the
17663 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
17667 @section Index Files Speed Up @value{GDBN}
17668 @cindex index files
17669 @cindex @samp{.gdb_index} section
17671 When @value{GDBN} finds a symbol file, it scans the symbols in the
17672 file in order to construct an internal symbol table. This lets most
17673 @value{GDBN} operations work quickly---at the cost of a delay early
17674 on. For large programs, this delay can be quite lengthy, so
17675 @value{GDBN} provides a way to build an index, which speeds up
17678 The index is stored as a section in the symbol file. @value{GDBN} can
17679 write the index to a file, then you can put it into the symbol file
17680 using @command{objcopy}.
17682 To create an index file, use the @code{save gdb-index} command:
17685 @item save gdb-index @var{directory}
17686 @kindex save gdb-index
17687 Create an index file for each symbol file currently known by
17688 @value{GDBN}. Each file is named after its corresponding symbol file,
17689 with @samp{.gdb-index} appended, and is written into the given
17693 Once you have created an index file you can merge it into your symbol
17694 file, here named @file{symfile}, using @command{objcopy}:
17697 $ objcopy --add-section .gdb_index=symfile.gdb-index \
17698 --set-section-flags .gdb_index=readonly symfile symfile
17701 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
17702 sections that have been deprecated. Usually they are deprecated because
17703 they are missing a new feature or have performance issues.
17704 To tell @value{GDBN} to use a deprecated index section anyway
17705 specify @code{set use-deprecated-index-sections on}.
17706 The default is @code{off}.
17707 This can speed up startup, but may result in some functionality being lost.
17708 @xref{Index Section Format}.
17710 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
17711 must be done before gdb reads the file. The following will not work:
17714 $ gdb -ex "set use-deprecated-index-sections on" <program>
17717 Instead you must do, for example,
17720 $ gdb -iex "set use-deprecated-index-sections on" <program>
17723 There are currently some limitation on indices. They only work when
17724 for DWARF debugging information, not stabs. And, they do not
17725 currently work for programs using Ada.
17727 @node Symbol Errors
17728 @section Errors Reading Symbol Files
17730 While reading a symbol file, @value{GDBN} occasionally encounters problems,
17731 such as symbol types it does not recognize, or known bugs in compiler
17732 output. By default, @value{GDBN} does not notify you of such problems, since
17733 they are relatively common and primarily of interest to people
17734 debugging compilers. If you are interested in seeing information
17735 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
17736 only one message about each such type of problem, no matter how many
17737 times the problem occurs; or you can ask @value{GDBN} to print more messages,
17738 to see how many times the problems occur, with the @code{set
17739 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
17742 The messages currently printed, and their meanings, include:
17745 @item inner block not inside outer block in @var{symbol}
17747 The symbol information shows where symbol scopes begin and end
17748 (such as at the start of a function or a block of statements). This
17749 error indicates that an inner scope block is not fully contained
17750 in its outer scope blocks.
17752 @value{GDBN} circumvents the problem by treating the inner block as if it had
17753 the same scope as the outer block. In the error message, @var{symbol}
17754 may be shown as ``@code{(don't know)}'' if the outer block is not a
17757 @item block at @var{address} out of order
17759 The symbol information for symbol scope blocks should occur in
17760 order of increasing addresses. This error indicates that it does not
17763 @value{GDBN} does not circumvent this problem, and has trouble
17764 locating symbols in the source file whose symbols it is reading. (You
17765 can often determine what source file is affected by specifying
17766 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
17769 @item bad block start address patched
17771 The symbol information for a symbol scope block has a start address
17772 smaller than the address of the preceding source line. This is known
17773 to occur in the SunOS 4.1.1 (and earlier) C compiler.
17775 @value{GDBN} circumvents the problem by treating the symbol scope block as
17776 starting on the previous source line.
17778 @item bad string table offset in symbol @var{n}
17781 Symbol number @var{n} contains a pointer into the string table which is
17782 larger than the size of the string table.
17784 @value{GDBN} circumvents the problem by considering the symbol to have the
17785 name @code{foo}, which may cause other problems if many symbols end up
17788 @item unknown symbol type @code{0x@var{nn}}
17790 The symbol information contains new data types that @value{GDBN} does
17791 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
17792 uncomprehended information, in hexadecimal.
17794 @value{GDBN} circumvents the error by ignoring this symbol information.
17795 This usually allows you to debug your program, though certain symbols
17796 are not accessible. If you encounter such a problem and feel like
17797 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
17798 on @code{complain}, then go up to the function @code{read_dbx_symtab}
17799 and examine @code{*bufp} to see the symbol.
17801 @item stub type has NULL name
17803 @value{GDBN} could not find the full definition for a struct or class.
17805 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
17806 The symbol information for a C@t{++} member function is missing some
17807 information that recent versions of the compiler should have output for
17810 @item info mismatch between compiler and debugger
17812 @value{GDBN} could not parse a type specification output by the compiler.
17817 @section GDB Data Files
17819 @cindex prefix for data files
17820 @value{GDBN} will sometimes read an auxiliary data file. These files
17821 are kept in a directory known as the @dfn{data directory}.
17823 You can set the data directory's name, and view the name @value{GDBN}
17824 is currently using.
17827 @kindex set data-directory
17828 @item set data-directory @var{directory}
17829 Set the directory which @value{GDBN} searches for auxiliary data files
17830 to @var{directory}.
17832 @kindex show data-directory
17833 @item show data-directory
17834 Show the directory @value{GDBN} searches for auxiliary data files.
17837 @cindex default data directory
17838 @cindex @samp{--with-gdb-datadir}
17839 You can set the default data directory by using the configure-time
17840 @samp{--with-gdb-datadir} option. If the data directory is inside
17841 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
17842 @samp{--exec-prefix}), then the default data directory will be updated
17843 automatically if the installed @value{GDBN} is moved to a new
17846 The data directory may also be specified with the
17847 @code{--data-directory} command line option.
17848 @xref{Mode Options}.
17851 @chapter Specifying a Debugging Target
17853 @cindex debugging target
17854 A @dfn{target} is the execution environment occupied by your program.
17856 Often, @value{GDBN} runs in the same host environment as your program;
17857 in that case, the debugging target is specified as a side effect when
17858 you use the @code{file} or @code{core} commands. When you need more
17859 flexibility---for example, running @value{GDBN} on a physically separate
17860 host, or controlling a standalone system over a serial port or a
17861 realtime system over a TCP/IP connection---you can use the @code{target}
17862 command to specify one of the target types configured for @value{GDBN}
17863 (@pxref{Target Commands, ,Commands for Managing Targets}).
17865 @cindex target architecture
17866 It is possible to build @value{GDBN} for several different @dfn{target
17867 architectures}. When @value{GDBN} is built like that, you can choose
17868 one of the available architectures with the @kbd{set architecture}
17872 @kindex set architecture
17873 @kindex show architecture
17874 @item set architecture @var{arch}
17875 This command sets the current target architecture to @var{arch}. The
17876 value of @var{arch} can be @code{"auto"}, in addition to one of the
17877 supported architectures.
17879 @item show architecture
17880 Show the current target architecture.
17882 @item set processor
17884 @kindex set processor
17885 @kindex show processor
17886 These are alias commands for, respectively, @code{set architecture}
17887 and @code{show architecture}.
17891 * Active Targets:: Active targets
17892 * Target Commands:: Commands for managing targets
17893 * Byte Order:: Choosing target byte order
17896 @node Active Targets
17897 @section Active Targets
17899 @cindex stacking targets
17900 @cindex active targets
17901 @cindex multiple targets
17903 There are multiple classes of targets such as: processes, executable files or
17904 recording sessions. Core files belong to the process class, making core file
17905 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
17906 on multiple active targets, one in each class. This allows you to (for
17907 example) start a process and inspect its activity, while still having access to
17908 the executable file after the process finishes. Or if you start process
17909 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
17910 presented a virtual layer of the recording target, while the process target
17911 remains stopped at the chronologically last point of the process execution.
17913 Use the @code{core-file} and @code{exec-file} commands to select a new core
17914 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
17915 specify as a target a process that is already running, use the @code{attach}
17916 command (@pxref{Attach, ,Debugging an Already-running Process}).
17918 @node Target Commands
17919 @section Commands for Managing Targets
17922 @item target @var{type} @var{parameters}
17923 Connects the @value{GDBN} host environment to a target machine or
17924 process. A target is typically a protocol for talking to debugging
17925 facilities. You use the argument @var{type} to specify the type or
17926 protocol of the target machine.
17928 Further @var{parameters} are interpreted by the target protocol, but
17929 typically include things like device names or host names to connect
17930 with, process numbers, and baud rates.
17932 The @code{target} command does not repeat if you press @key{RET} again
17933 after executing the command.
17935 @kindex help target
17937 Displays the names of all targets available. To display targets
17938 currently selected, use either @code{info target} or @code{info files}
17939 (@pxref{Files, ,Commands to Specify Files}).
17941 @item help target @var{name}
17942 Describe a particular target, including any parameters necessary to
17945 @kindex set gnutarget
17946 @item set gnutarget @var{args}
17947 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
17948 knows whether it is reading an @dfn{executable},
17949 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
17950 with the @code{set gnutarget} command. Unlike most @code{target} commands,
17951 with @code{gnutarget} the @code{target} refers to a program, not a machine.
17954 @emph{Warning:} To specify a file format with @code{set gnutarget},
17955 you must know the actual BFD name.
17959 @xref{Files, , Commands to Specify Files}.
17961 @kindex show gnutarget
17962 @item show gnutarget
17963 Use the @code{show gnutarget} command to display what file format
17964 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
17965 @value{GDBN} will determine the file format for each file automatically,
17966 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
17969 @cindex common targets
17970 Here are some common targets (available, or not, depending on the GDB
17975 @item target exec @var{program}
17976 @cindex executable file target
17977 An executable file. @samp{target exec @var{program}} is the same as
17978 @samp{exec-file @var{program}}.
17980 @item target core @var{filename}
17981 @cindex core dump file target
17982 A core dump file. @samp{target core @var{filename}} is the same as
17983 @samp{core-file @var{filename}}.
17985 @item target remote @var{medium}
17986 @cindex remote target
17987 A remote system connected to @value{GDBN} via a serial line or network
17988 connection. This command tells @value{GDBN} to use its own remote
17989 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
17991 For example, if you have a board connected to @file{/dev/ttya} on the
17992 machine running @value{GDBN}, you could say:
17995 target remote /dev/ttya
17998 @code{target remote} supports the @code{load} command. This is only
17999 useful if you have some other way of getting the stub to the target
18000 system, and you can put it somewhere in memory where it won't get
18001 clobbered by the download.
18003 @item target sim @r{[}@var{simargs}@r{]} @dots{}
18004 @cindex built-in simulator target
18005 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
18013 works; however, you cannot assume that a specific memory map, device
18014 drivers, or even basic I/O is available, although some simulators do
18015 provide these. For info about any processor-specific simulator details,
18016 see the appropriate section in @ref{Embedded Processors, ,Embedded
18021 Different targets are available on different configurations of @value{GDBN};
18022 your configuration may have more or fewer targets.
18024 Many remote targets require you to download the executable's code once
18025 you've successfully established a connection. You may wish to control
18026 various aspects of this process.
18031 @kindex set hash@r{, for remote monitors}
18032 @cindex hash mark while downloading
18033 This command controls whether a hash mark @samp{#} is displayed while
18034 downloading a file to the remote monitor. If on, a hash mark is
18035 displayed after each S-record is successfully downloaded to the
18039 @kindex show hash@r{, for remote monitors}
18040 Show the current status of displaying the hash mark.
18042 @item set debug monitor
18043 @kindex set debug monitor
18044 @cindex display remote monitor communications
18045 Enable or disable display of communications messages between
18046 @value{GDBN} and the remote monitor.
18048 @item show debug monitor
18049 @kindex show debug monitor
18050 Show the current status of displaying communications between
18051 @value{GDBN} and the remote monitor.
18056 @kindex load @var{filename}
18057 @item load @var{filename}
18059 Depending on what remote debugging facilities are configured into
18060 @value{GDBN}, the @code{load} command may be available. Where it exists, it
18061 is meant to make @var{filename} (an executable) available for debugging
18062 on the remote system---by downloading, or dynamic linking, for example.
18063 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
18064 the @code{add-symbol-file} command.
18066 If your @value{GDBN} does not have a @code{load} command, attempting to
18067 execute it gets the error message ``@code{You can't do that when your
18068 target is @dots{}}''
18070 The file is loaded at whatever address is specified in the executable.
18071 For some object file formats, you can specify the load address when you
18072 link the program; for other formats, like a.out, the object file format
18073 specifies a fixed address.
18074 @c FIXME! This would be a good place for an xref to the GNU linker doc.
18076 Depending on the remote side capabilities, @value{GDBN} may be able to
18077 load programs into flash memory.
18079 @code{load} does not repeat if you press @key{RET} again after using it.
18083 @section Choosing Target Byte Order
18085 @cindex choosing target byte order
18086 @cindex target byte order
18088 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
18089 offer the ability to run either big-endian or little-endian byte
18090 orders. Usually the executable or symbol will include a bit to
18091 designate the endian-ness, and you will not need to worry about
18092 which to use. However, you may still find it useful to adjust
18093 @value{GDBN}'s idea of processor endian-ness manually.
18097 @item set endian big
18098 Instruct @value{GDBN} to assume the target is big-endian.
18100 @item set endian little
18101 Instruct @value{GDBN} to assume the target is little-endian.
18103 @item set endian auto
18104 Instruct @value{GDBN} to use the byte order associated with the
18108 Display @value{GDBN}'s current idea of the target byte order.
18112 Note that these commands merely adjust interpretation of symbolic
18113 data on the host, and that they have absolutely no effect on the
18117 @node Remote Debugging
18118 @chapter Debugging Remote Programs
18119 @cindex remote debugging
18121 If you are trying to debug a program running on a machine that cannot run
18122 @value{GDBN} in the usual way, it is often useful to use remote debugging.
18123 For example, you might use remote debugging on an operating system kernel,
18124 or on a small system which does not have a general purpose operating system
18125 powerful enough to run a full-featured debugger.
18127 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
18128 to make this work with particular debugging targets. In addition,
18129 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
18130 but not specific to any particular target system) which you can use if you
18131 write the remote stubs---the code that runs on the remote system to
18132 communicate with @value{GDBN}.
18134 Other remote targets may be available in your
18135 configuration of @value{GDBN}; use @code{help target} to list them.
18138 * Connecting:: Connecting to a remote target
18139 * File Transfer:: Sending files to a remote system
18140 * Server:: Using the gdbserver program
18141 * Remote Configuration:: Remote configuration
18142 * Remote Stub:: Implementing a remote stub
18146 @section Connecting to a Remote Target
18148 On the @value{GDBN} host machine, you will need an unstripped copy of
18149 your program, since @value{GDBN} needs symbol and debugging information.
18150 Start up @value{GDBN} as usual, using the name of the local copy of your
18151 program as the first argument.
18153 @cindex @code{target remote}
18154 @value{GDBN} can communicate with the target over a serial line, or
18155 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
18156 each case, @value{GDBN} uses the same protocol for debugging your
18157 program; only the medium carrying the debugging packets varies. The
18158 @code{target remote} command establishes a connection to the target.
18159 Its arguments indicate which medium to use:
18163 @item target remote @var{serial-device}
18164 @cindex serial line, @code{target remote}
18165 Use @var{serial-device} to communicate with the target. For example,
18166 to use a serial line connected to the device named @file{/dev/ttyb}:
18169 target remote /dev/ttyb
18172 If you're using a serial line, you may want to give @value{GDBN} the
18173 @samp{--baud} option, or use the @code{set serial baud} command
18174 (@pxref{Remote Configuration, set serial baud}) before the
18175 @code{target} command.
18177 @item target remote @code{@var{host}:@var{port}}
18178 @itemx target remote @code{tcp:@var{host}:@var{port}}
18179 @cindex @acronym{TCP} port, @code{target remote}
18180 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
18181 The @var{host} may be either a host name or a numeric @acronym{IP}
18182 address; @var{port} must be a decimal number. The @var{host} could be
18183 the target machine itself, if it is directly connected to the net, or
18184 it might be a terminal server which in turn has a serial line to the
18187 For example, to connect to port 2828 on a terminal server named
18191 target remote manyfarms:2828
18194 If your remote target is actually running on the same machine as your
18195 debugger session (e.g.@: a simulator for your target running on the
18196 same host), you can omit the hostname. For example, to connect to
18197 port 1234 on your local machine:
18200 target remote :1234
18204 Note that the colon is still required here.
18206 @item target remote @code{udp:@var{host}:@var{port}}
18207 @cindex @acronym{UDP} port, @code{target remote}
18208 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
18209 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
18212 target remote udp:manyfarms:2828
18215 When using a @acronym{UDP} connection for remote debugging, you should
18216 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
18217 can silently drop packets on busy or unreliable networks, which will
18218 cause havoc with your debugging session.
18220 @item target remote | @var{command}
18221 @cindex pipe, @code{target remote} to
18222 Run @var{command} in the background and communicate with it using a
18223 pipe. The @var{command} is a shell command, to be parsed and expanded
18224 by the system's command shell, @code{/bin/sh}; it should expect remote
18225 protocol packets on its standard input, and send replies on its
18226 standard output. You could use this to run a stand-alone simulator
18227 that speaks the remote debugging protocol, to make net connections
18228 using programs like @code{ssh}, or for other similar tricks.
18230 If @var{command} closes its standard output (perhaps by exiting),
18231 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
18232 program has already exited, this will have no effect.)
18236 Once the connection has been established, you can use all the usual
18237 commands to examine and change data. The remote program is already
18238 running; you can use @kbd{step} and @kbd{continue}, and you do not
18239 need to use @kbd{run}.
18241 @cindex interrupting remote programs
18242 @cindex remote programs, interrupting
18243 Whenever @value{GDBN} is waiting for the remote program, if you type the
18244 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
18245 program. This may or may not succeed, depending in part on the hardware
18246 and the serial drivers the remote system uses. If you type the
18247 interrupt character once again, @value{GDBN} displays this prompt:
18250 Interrupted while waiting for the program.
18251 Give up (and stop debugging it)? (y or n)
18254 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
18255 (If you decide you want to try again later, you can use @samp{target
18256 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
18257 goes back to waiting.
18260 @kindex detach (remote)
18262 When you have finished debugging the remote program, you can use the
18263 @code{detach} command to release it from @value{GDBN} control.
18264 Detaching from the target normally resumes its execution, but the results
18265 will depend on your particular remote stub. After the @code{detach}
18266 command, @value{GDBN} is free to connect to another target.
18270 The @code{disconnect} command behaves like @code{detach}, except that
18271 the target is generally not resumed. It will wait for @value{GDBN}
18272 (this instance or another one) to connect and continue debugging. After
18273 the @code{disconnect} command, @value{GDBN} is again free to connect to
18276 @cindex send command to remote monitor
18277 @cindex extend @value{GDBN} for remote targets
18278 @cindex add new commands for external monitor
18280 @item monitor @var{cmd}
18281 This command allows you to send arbitrary commands directly to the
18282 remote monitor. Since @value{GDBN} doesn't care about the commands it
18283 sends like this, this command is the way to extend @value{GDBN}---you
18284 can add new commands that only the external monitor will understand
18288 @node File Transfer
18289 @section Sending files to a remote system
18290 @cindex remote target, file transfer
18291 @cindex file transfer
18292 @cindex sending files to remote systems
18294 Some remote targets offer the ability to transfer files over the same
18295 connection used to communicate with @value{GDBN}. This is convenient
18296 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
18297 running @code{gdbserver} over a network interface. For other targets,
18298 e.g.@: embedded devices with only a single serial port, this may be
18299 the only way to upload or download files.
18301 Not all remote targets support these commands.
18305 @item remote put @var{hostfile} @var{targetfile}
18306 Copy file @var{hostfile} from the host system (the machine running
18307 @value{GDBN}) to @var{targetfile} on the target system.
18310 @item remote get @var{targetfile} @var{hostfile}
18311 Copy file @var{targetfile} from the target system to @var{hostfile}
18312 on the host system.
18314 @kindex remote delete
18315 @item remote delete @var{targetfile}
18316 Delete @var{targetfile} from the target system.
18321 @section Using the @code{gdbserver} Program
18324 @cindex remote connection without stubs
18325 @code{gdbserver} is a control program for Unix-like systems, which
18326 allows you to connect your program with a remote @value{GDBN} via
18327 @code{target remote}---but without linking in the usual debugging stub.
18329 @code{gdbserver} is not a complete replacement for the debugging stubs,
18330 because it requires essentially the same operating-system facilities
18331 that @value{GDBN} itself does. In fact, a system that can run
18332 @code{gdbserver} to connect to a remote @value{GDBN} could also run
18333 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
18334 because it is a much smaller program than @value{GDBN} itself. It is
18335 also easier to port than all of @value{GDBN}, so you may be able to get
18336 started more quickly on a new system by using @code{gdbserver}.
18337 Finally, if you develop code for real-time systems, you may find that
18338 the tradeoffs involved in real-time operation make it more convenient to
18339 do as much development work as possible on another system, for example
18340 by cross-compiling. You can use @code{gdbserver} to make a similar
18341 choice for debugging.
18343 @value{GDBN} and @code{gdbserver} communicate via either a serial line
18344 or a TCP connection, using the standard @value{GDBN} remote serial
18348 @emph{Warning:} @code{gdbserver} does not have any built-in security.
18349 Do not run @code{gdbserver} connected to any public network; a
18350 @value{GDBN} connection to @code{gdbserver} provides access to the
18351 target system with the same privileges as the user running
18355 @subsection Running @code{gdbserver}
18356 @cindex arguments, to @code{gdbserver}
18357 @cindex @code{gdbserver}, command-line arguments
18359 Run @code{gdbserver} on the target system. You need a copy of the
18360 program you want to debug, including any libraries it requires.
18361 @code{gdbserver} does not need your program's symbol table, so you can
18362 strip the program if necessary to save space. @value{GDBN} on the host
18363 system does all the symbol handling.
18365 To use the server, you must tell it how to communicate with @value{GDBN};
18366 the name of your program; and the arguments for your program. The usual
18370 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
18373 @var{comm} is either a device name (to use a serial line), or a TCP
18374 hostname and portnumber, or @code{-} or @code{stdio} to use
18375 stdin/stdout of @code{gdbserver}.
18376 For example, to debug Emacs with the argument
18377 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
18381 target> gdbserver /dev/com1 emacs foo.txt
18384 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
18387 To use a TCP connection instead of a serial line:
18390 target> gdbserver host:2345 emacs foo.txt
18393 The only difference from the previous example is the first argument,
18394 specifying that you are communicating with the host @value{GDBN} via
18395 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
18396 expect a TCP connection from machine @samp{host} to local TCP port 2345.
18397 (Currently, the @samp{host} part is ignored.) You can choose any number
18398 you want for the port number as long as it does not conflict with any
18399 TCP ports already in use on the target system (for example, @code{23} is
18400 reserved for @code{telnet}).@footnote{If you choose a port number that
18401 conflicts with another service, @code{gdbserver} prints an error message
18402 and exits.} You must use the same port number with the host @value{GDBN}
18403 @code{target remote} command.
18405 The @code{stdio} connection is useful when starting @code{gdbserver}
18409 (gdb) target remote | ssh -T hostname gdbserver - hello
18412 The @samp{-T} option to ssh is provided because we don't need a remote pty,
18413 and we don't want escape-character handling. Ssh does this by default when
18414 a command is provided, the flag is provided to make it explicit.
18415 You could elide it if you want to.
18417 Programs started with stdio-connected gdbserver have @file{/dev/null} for
18418 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
18419 display through a pipe connected to gdbserver.
18420 Both @code{stdout} and @code{stderr} use the same pipe.
18422 @subsubsection Attaching to a Running Program
18423 @cindex attach to a program, @code{gdbserver}
18424 @cindex @option{--attach}, @code{gdbserver} option
18426 On some targets, @code{gdbserver} can also attach to running programs.
18427 This is accomplished via the @code{--attach} argument. The syntax is:
18430 target> gdbserver --attach @var{comm} @var{pid}
18433 @var{pid} is the process ID of a currently running process. It isn't necessary
18434 to point @code{gdbserver} at a binary for the running process.
18437 You can debug processes by name instead of process ID if your target has the
18438 @code{pidof} utility:
18441 target> gdbserver --attach @var{comm} `pidof @var{program}`
18444 In case more than one copy of @var{program} is running, or @var{program}
18445 has multiple threads, most versions of @code{pidof} support the
18446 @code{-s} option to only return the first process ID.
18448 @subsubsection Multi-Process Mode for @code{gdbserver}
18449 @cindex @code{gdbserver}, multiple processes
18450 @cindex multiple processes with @code{gdbserver}
18452 When you connect to @code{gdbserver} using @code{target remote},
18453 @code{gdbserver} debugs the specified program only once. When the
18454 program exits, or you detach from it, @value{GDBN} closes the connection
18455 and @code{gdbserver} exits.
18457 If you connect using @kbd{target extended-remote}, @code{gdbserver}
18458 enters multi-process mode. When the debugged program exits, or you
18459 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
18460 though no program is running. The @code{run} and @code{attach}
18461 commands instruct @code{gdbserver} to run or attach to a new program.
18462 The @code{run} command uses @code{set remote exec-file} (@pxref{set
18463 remote exec-file}) to select the program to run. Command line
18464 arguments are supported, except for wildcard expansion and I/O
18465 redirection (@pxref{Arguments}).
18467 @cindex @option{--multi}, @code{gdbserver} option
18468 To start @code{gdbserver} without supplying an initial command to run
18469 or process ID to attach, use the @option{--multi} command line option.
18470 Then you can connect using @kbd{target extended-remote} and start
18471 the program you want to debug.
18473 In multi-process mode @code{gdbserver} does not automatically exit unless you
18474 use the option @option{--once}. You can terminate it by using
18475 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
18476 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
18477 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
18478 @option{--multi} option to @code{gdbserver} has no influence on that.
18480 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
18482 This section applies only when @code{gdbserver} is run to listen on a TCP port.
18484 @code{gdbserver} normally terminates after all of its debugged processes have
18485 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
18486 extended-remote}, @code{gdbserver} stays running even with no processes left.
18487 @value{GDBN} normally terminates the spawned debugged process on its exit,
18488 which normally also terminates @code{gdbserver} in the @kbd{target remote}
18489 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
18490 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
18491 stays running even in the @kbd{target remote} mode.
18493 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
18494 Such reconnecting is useful for features like @ref{disconnected tracing}. For
18495 completeness, at most one @value{GDBN} can be connected at a time.
18497 @cindex @option{--once}, @code{gdbserver} option
18498 By default, @code{gdbserver} keeps the listening TCP port open, so that
18499 subsequent connections are possible. However, if you start @code{gdbserver}
18500 with the @option{--once} option, it will stop listening for any further
18501 connection attempts after connecting to the first @value{GDBN} session. This
18502 means no further connections to @code{gdbserver} will be possible after the
18503 first one. It also means @code{gdbserver} will terminate after the first
18504 connection with remote @value{GDBN} has closed, even for unexpectedly closed
18505 connections and even in the @kbd{target extended-remote} mode. The
18506 @option{--once} option allows reusing the same port number for connecting to
18507 multiple instances of @code{gdbserver} running on the same host, since each
18508 instance closes its port after the first connection.
18510 @subsubsection Other Command-Line Arguments for @code{gdbserver}
18512 @cindex @option{--debug}, @code{gdbserver} option
18513 The @option{--debug} option tells @code{gdbserver} to display extra
18514 status information about the debugging process.
18515 @cindex @option{--remote-debug}, @code{gdbserver} option
18516 The @option{--remote-debug} option tells @code{gdbserver} to display
18517 remote protocol debug output. These options are intended for
18518 @code{gdbserver} development and for bug reports to the developers.
18520 @cindex @option{--wrapper}, @code{gdbserver} option
18521 The @option{--wrapper} option specifies a wrapper to launch programs
18522 for debugging. The option should be followed by the name of the
18523 wrapper, then any command-line arguments to pass to the wrapper, then
18524 @kbd{--} indicating the end of the wrapper arguments.
18526 @code{gdbserver} runs the specified wrapper program with a combined
18527 command line including the wrapper arguments, then the name of the
18528 program to debug, then any arguments to the program. The wrapper
18529 runs until it executes your program, and then @value{GDBN} gains control.
18531 You can use any program that eventually calls @code{execve} with
18532 its arguments as a wrapper. Several standard Unix utilities do
18533 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
18534 with @code{exec "$@@"} will also work.
18536 For example, you can use @code{env} to pass an environment variable to
18537 the debugged program, without setting the variable in @code{gdbserver}'s
18541 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
18544 @subsection Connecting to @code{gdbserver}
18546 Run @value{GDBN} on the host system.
18548 First make sure you have the necessary symbol files. Load symbols for
18549 your application using the @code{file} command before you connect. Use
18550 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
18551 was compiled with the correct sysroot using @code{--with-sysroot}).
18553 The symbol file and target libraries must exactly match the executable
18554 and libraries on the target, with one exception: the files on the host
18555 system should not be stripped, even if the files on the target system
18556 are. Mismatched or missing files will lead to confusing results
18557 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
18558 files may also prevent @code{gdbserver} from debugging multi-threaded
18561 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
18562 For TCP connections, you must start up @code{gdbserver} prior to using
18563 the @code{target remote} command. Otherwise you may get an error whose
18564 text depends on the host system, but which usually looks something like
18565 @samp{Connection refused}. Don't use the @code{load}
18566 command in @value{GDBN} when using @code{gdbserver}, since the program is
18567 already on the target.
18569 @subsection Monitor Commands for @code{gdbserver}
18570 @cindex monitor commands, for @code{gdbserver}
18571 @anchor{Monitor Commands for gdbserver}
18573 During a @value{GDBN} session using @code{gdbserver}, you can use the
18574 @code{monitor} command to send special requests to @code{gdbserver}.
18575 Here are the available commands.
18579 List the available monitor commands.
18581 @item monitor set debug 0
18582 @itemx monitor set debug 1
18583 Disable or enable general debugging messages.
18585 @item monitor set remote-debug 0
18586 @itemx monitor set remote-debug 1
18587 Disable or enable specific debugging messages associated with the remote
18588 protocol (@pxref{Remote Protocol}).
18590 @item monitor set libthread-db-search-path [PATH]
18591 @cindex gdbserver, search path for @code{libthread_db}
18592 When this command is issued, @var{path} is a colon-separated list of
18593 directories to search for @code{libthread_db} (@pxref{Threads,,set
18594 libthread-db-search-path}). If you omit @var{path},
18595 @samp{libthread-db-search-path} will be reset to its default value.
18597 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
18598 not supported in @code{gdbserver}.
18601 Tell gdbserver to exit immediately. This command should be followed by
18602 @code{disconnect} to close the debugging session. @code{gdbserver} will
18603 detach from any attached processes and kill any processes it created.
18604 Use @code{monitor exit} to terminate @code{gdbserver} at the end
18605 of a multi-process mode debug session.
18609 @subsection Tracepoints support in @code{gdbserver}
18610 @cindex tracepoints support in @code{gdbserver}
18612 On some targets, @code{gdbserver} supports tracepoints, fast
18613 tracepoints and static tracepoints.
18615 For fast or static tracepoints to work, a special library called the
18616 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
18617 This library is built and distributed as an integral part of
18618 @code{gdbserver}. In addition, support for static tracepoints
18619 requires building the in-process agent library with static tracepoints
18620 support. At present, the UST (LTTng Userspace Tracer,
18621 @url{http://lttng.org/ust}) tracing engine is supported. This support
18622 is automatically available if UST development headers are found in the
18623 standard include path when @code{gdbserver} is built, or if
18624 @code{gdbserver} was explicitly configured using @option{--with-ust}
18625 to point at such headers. You can explicitly disable the support
18626 using @option{--with-ust=no}.
18628 There are several ways to load the in-process agent in your program:
18631 @item Specifying it as dependency at link time
18633 You can link your program dynamically with the in-process agent
18634 library. On most systems, this is accomplished by adding
18635 @code{-linproctrace} to the link command.
18637 @item Using the system's preloading mechanisms
18639 You can force loading the in-process agent at startup time by using
18640 your system's support for preloading shared libraries. Many Unixes
18641 support the concept of preloading user defined libraries. In most
18642 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
18643 in the environment. See also the description of @code{gdbserver}'s
18644 @option{--wrapper} command line option.
18646 @item Using @value{GDBN} to force loading the agent at run time
18648 On some systems, you can force the inferior to load a shared library,
18649 by calling a dynamic loader function in the inferior that takes care
18650 of dynamically looking up and loading a shared library. On most Unix
18651 systems, the function is @code{dlopen}. You'll use the @code{call}
18652 command for that. For example:
18655 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
18658 Note that on most Unix systems, for the @code{dlopen} function to be
18659 available, the program needs to be linked with @code{-ldl}.
18662 On systems that have a userspace dynamic loader, like most Unix
18663 systems, when you connect to @code{gdbserver} using @code{target
18664 remote}, you'll find that the program is stopped at the dynamic
18665 loader's entry point, and no shared library has been loaded in the
18666 program's address space yet, including the in-process agent. In that
18667 case, before being able to use any of the fast or static tracepoints
18668 features, you need to let the loader run and load the shared
18669 libraries. The simplest way to do that is to run the program to the
18670 main procedure. E.g., if debugging a C or C@t{++} program, start
18671 @code{gdbserver} like so:
18674 $ gdbserver :9999 myprogram
18677 Start GDB and connect to @code{gdbserver} like so, and run to main:
18681 (@value{GDBP}) target remote myhost:9999
18682 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
18683 (@value{GDBP}) b main
18684 (@value{GDBP}) continue
18687 The in-process tracing agent library should now be loaded into the
18688 process; you can confirm it with the @code{info sharedlibrary}
18689 command, which will list @file{libinproctrace.so} as loaded in the
18690 process. You are now ready to install fast tracepoints, list static
18691 tracepoint markers, probe static tracepoints markers, and start
18694 @node Remote Configuration
18695 @section Remote Configuration
18698 @kindex show remote
18699 This section documents the configuration options available when
18700 debugging remote programs. For the options related to the File I/O
18701 extensions of the remote protocol, see @ref{system,
18702 system-call-allowed}.
18705 @item set remoteaddresssize @var{bits}
18706 @cindex address size for remote targets
18707 @cindex bits in remote address
18708 Set the maximum size of address in a memory packet to the specified
18709 number of bits. @value{GDBN} will mask off the address bits above
18710 that number, when it passes addresses to the remote target. The
18711 default value is the number of bits in the target's address.
18713 @item show remoteaddresssize
18714 Show the current value of remote address size in bits.
18716 @item set serial baud @var{n}
18717 @cindex baud rate for remote targets
18718 Set the baud rate for the remote serial I/O to @var{n} baud. The
18719 value is used to set the speed of the serial port used for debugging
18722 @item show serial baud
18723 Show the current speed of the remote connection.
18725 @item set remotebreak
18726 @cindex interrupt remote programs
18727 @cindex BREAK signal instead of Ctrl-C
18728 @anchor{set remotebreak}
18729 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
18730 when you type @kbd{Ctrl-c} to interrupt the program running
18731 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
18732 character instead. The default is off, since most remote systems
18733 expect to see @samp{Ctrl-C} as the interrupt signal.
18735 @item show remotebreak
18736 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
18737 interrupt the remote program.
18739 @item set remoteflow on
18740 @itemx set remoteflow off
18741 @kindex set remoteflow
18742 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
18743 on the serial port used to communicate to the remote target.
18745 @item show remoteflow
18746 @kindex show remoteflow
18747 Show the current setting of hardware flow control.
18749 @item set remotelogbase @var{base}
18750 Set the base (a.k.a.@: radix) of logging serial protocol
18751 communications to @var{base}. Supported values of @var{base} are:
18752 @code{ascii}, @code{octal}, and @code{hex}. The default is
18755 @item show remotelogbase
18756 Show the current setting of the radix for logging remote serial
18759 @item set remotelogfile @var{file}
18760 @cindex record serial communications on file
18761 Record remote serial communications on the named @var{file}. The
18762 default is not to record at all.
18764 @item show remotelogfile.
18765 Show the current setting of the file name on which to record the
18766 serial communications.
18768 @item set remotetimeout @var{num}
18769 @cindex timeout for serial communications
18770 @cindex remote timeout
18771 Set the timeout limit to wait for the remote target to respond to
18772 @var{num} seconds. The default is 2 seconds.
18774 @item show remotetimeout
18775 Show the current number of seconds to wait for the remote target
18778 @cindex limit hardware breakpoints and watchpoints
18779 @cindex remote target, limit break- and watchpoints
18780 @anchor{set remote hardware-watchpoint-limit}
18781 @anchor{set remote hardware-breakpoint-limit}
18782 @item set remote hardware-watchpoint-limit @var{limit}
18783 @itemx set remote hardware-breakpoint-limit @var{limit}
18784 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
18785 watchpoints. A limit of -1, the default, is treated as unlimited.
18787 @cindex limit hardware watchpoints length
18788 @cindex remote target, limit watchpoints length
18789 @anchor{set remote hardware-watchpoint-length-limit}
18790 @item set remote hardware-watchpoint-length-limit @var{limit}
18791 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
18792 a remote hardware watchpoint. A limit of -1, the default, is treated
18795 @item show remote hardware-watchpoint-length-limit
18796 Show the current limit (in bytes) of the maximum length of
18797 a remote hardware watchpoint.
18799 @item set remote exec-file @var{filename}
18800 @itemx show remote exec-file
18801 @anchor{set remote exec-file}
18802 @cindex executable file, for remote target
18803 Select the file used for @code{run} with @code{target
18804 extended-remote}. This should be set to a filename valid on the
18805 target system. If it is not set, the target will use a default
18806 filename (e.g.@: the last program run).
18808 @item set remote interrupt-sequence
18809 @cindex interrupt remote programs
18810 @cindex select Ctrl-C, BREAK or BREAK-g
18811 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
18812 @samp{BREAK-g} as the
18813 sequence to the remote target in order to interrupt the execution.
18814 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
18815 is high level of serial line for some certain time.
18816 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
18817 It is @code{BREAK} signal followed by character @code{g}.
18819 @item show interrupt-sequence
18820 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
18821 is sent by @value{GDBN} to interrupt the remote program.
18822 @code{BREAK-g} is BREAK signal followed by @code{g} and
18823 also known as Magic SysRq g.
18825 @item set remote interrupt-on-connect
18826 @cindex send interrupt-sequence on start
18827 Specify whether interrupt-sequence is sent to remote target when
18828 @value{GDBN} connects to it. This is mostly needed when you debug
18829 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
18830 which is known as Magic SysRq g in order to connect @value{GDBN}.
18832 @item show interrupt-on-connect
18833 Show whether interrupt-sequence is sent
18834 to remote target when @value{GDBN} connects to it.
18838 @item set tcp auto-retry on
18839 @cindex auto-retry, for remote TCP target
18840 Enable auto-retry for remote TCP connections. This is useful if the remote
18841 debugging agent is launched in parallel with @value{GDBN}; there is a race
18842 condition because the agent may not become ready to accept the connection
18843 before @value{GDBN} attempts to connect. When auto-retry is
18844 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
18845 to establish the connection using the timeout specified by
18846 @code{set tcp connect-timeout}.
18848 @item set tcp auto-retry off
18849 Do not auto-retry failed TCP connections.
18851 @item show tcp auto-retry
18852 Show the current auto-retry setting.
18854 @item set tcp connect-timeout @var{seconds}
18855 @itemx set tcp connect-timeout unlimited
18856 @cindex connection timeout, for remote TCP target
18857 @cindex timeout, for remote target connection
18858 Set the timeout for establishing a TCP connection to the remote target to
18859 @var{seconds}. The timeout affects both polling to retry failed connections
18860 (enabled by @code{set tcp auto-retry on}) and waiting for connections
18861 that are merely slow to complete, and represents an approximate cumulative
18862 value. If @var{seconds} is @code{unlimited}, there is no timeout and
18863 @value{GDBN} will keep attempting to establish a connection forever,
18864 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
18866 @item show tcp connect-timeout
18867 Show the current connection timeout setting.
18870 @cindex remote packets, enabling and disabling
18871 The @value{GDBN} remote protocol autodetects the packets supported by
18872 your debugging stub. If you need to override the autodetection, you
18873 can use these commands to enable or disable individual packets. Each
18874 packet can be set to @samp{on} (the remote target supports this
18875 packet), @samp{off} (the remote target does not support this packet),
18876 or @samp{auto} (detect remote target support for this packet). They
18877 all default to @samp{auto}. For more information about each packet,
18878 see @ref{Remote Protocol}.
18880 During normal use, you should not have to use any of these commands.
18881 If you do, that may be a bug in your remote debugging stub, or a bug
18882 in @value{GDBN}. You may want to report the problem to the
18883 @value{GDBN} developers.
18885 For each packet @var{name}, the command to enable or disable the
18886 packet is @code{set remote @var{name}-packet}. The available settings
18889 @multitable @columnfractions 0.28 0.32 0.25
18892 @tab Related Features
18894 @item @code{fetch-register}
18896 @tab @code{info registers}
18898 @item @code{set-register}
18902 @item @code{binary-download}
18904 @tab @code{load}, @code{set}
18906 @item @code{read-aux-vector}
18907 @tab @code{qXfer:auxv:read}
18908 @tab @code{info auxv}
18910 @item @code{symbol-lookup}
18911 @tab @code{qSymbol}
18912 @tab Detecting multiple threads
18914 @item @code{attach}
18915 @tab @code{vAttach}
18918 @item @code{verbose-resume}
18920 @tab Stepping or resuming multiple threads
18926 @item @code{software-breakpoint}
18930 @item @code{hardware-breakpoint}
18934 @item @code{write-watchpoint}
18938 @item @code{read-watchpoint}
18942 @item @code{access-watchpoint}
18946 @item @code{target-features}
18947 @tab @code{qXfer:features:read}
18948 @tab @code{set architecture}
18950 @item @code{library-info}
18951 @tab @code{qXfer:libraries:read}
18952 @tab @code{info sharedlibrary}
18954 @item @code{memory-map}
18955 @tab @code{qXfer:memory-map:read}
18956 @tab @code{info mem}
18958 @item @code{read-sdata-object}
18959 @tab @code{qXfer:sdata:read}
18960 @tab @code{print $_sdata}
18962 @item @code{read-spu-object}
18963 @tab @code{qXfer:spu:read}
18964 @tab @code{info spu}
18966 @item @code{write-spu-object}
18967 @tab @code{qXfer:spu:write}
18968 @tab @code{info spu}
18970 @item @code{read-siginfo-object}
18971 @tab @code{qXfer:siginfo:read}
18972 @tab @code{print $_siginfo}
18974 @item @code{write-siginfo-object}
18975 @tab @code{qXfer:siginfo:write}
18976 @tab @code{set $_siginfo}
18978 @item @code{threads}
18979 @tab @code{qXfer:threads:read}
18980 @tab @code{info threads}
18982 @item @code{get-thread-local-@*storage-address}
18983 @tab @code{qGetTLSAddr}
18984 @tab Displaying @code{__thread} variables
18986 @item @code{get-thread-information-block-address}
18987 @tab @code{qGetTIBAddr}
18988 @tab Display MS-Windows Thread Information Block.
18990 @item @code{search-memory}
18991 @tab @code{qSearch:memory}
18994 @item @code{supported-packets}
18995 @tab @code{qSupported}
18996 @tab Remote communications parameters
18998 @item @code{pass-signals}
18999 @tab @code{QPassSignals}
19000 @tab @code{handle @var{signal}}
19002 @item @code{program-signals}
19003 @tab @code{QProgramSignals}
19004 @tab @code{handle @var{signal}}
19006 @item @code{hostio-close-packet}
19007 @tab @code{vFile:close}
19008 @tab @code{remote get}, @code{remote put}
19010 @item @code{hostio-open-packet}
19011 @tab @code{vFile:open}
19012 @tab @code{remote get}, @code{remote put}
19014 @item @code{hostio-pread-packet}
19015 @tab @code{vFile:pread}
19016 @tab @code{remote get}, @code{remote put}
19018 @item @code{hostio-pwrite-packet}
19019 @tab @code{vFile:pwrite}
19020 @tab @code{remote get}, @code{remote put}
19022 @item @code{hostio-unlink-packet}
19023 @tab @code{vFile:unlink}
19024 @tab @code{remote delete}
19026 @item @code{hostio-readlink-packet}
19027 @tab @code{vFile:readlink}
19030 @item @code{noack-packet}
19031 @tab @code{QStartNoAckMode}
19032 @tab Packet acknowledgment
19034 @item @code{osdata}
19035 @tab @code{qXfer:osdata:read}
19036 @tab @code{info os}
19038 @item @code{query-attached}
19039 @tab @code{qAttached}
19040 @tab Querying remote process attach state.
19042 @item @code{trace-buffer-size}
19043 @tab @code{QTBuffer:size}
19044 @tab @code{set trace-buffer-size}
19046 @item @code{trace-status}
19047 @tab @code{qTStatus}
19048 @tab @code{tstatus}
19050 @item @code{traceframe-info}
19051 @tab @code{qXfer:traceframe-info:read}
19052 @tab Traceframe info
19054 @item @code{install-in-trace}
19055 @tab @code{InstallInTrace}
19056 @tab Install tracepoint in tracing
19058 @item @code{disable-randomization}
19059 @tab @code{QDisableRandomization}
19060 @tab @code{set disable-randomization}
19062 @item @code{conditional-breakpoints-packet}
19063 @tab @code{Z0 and Z1}
19064 @tab @code{Support for target-side breakpoint condition evaluation}
19068 @section Implementing a Remote Stub
19070 @cindex debugging stub, example
19071 @cindex remote stub, example
19072 @cindex stub example, remote debugging
19073 The stub files provided with @value{GDBN} implement the target side of the
19074 communication protocol, and the @value{GDBN} side is implemented in the
19075 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
19076 these subroutines to communicate, and ignore the details. (If you're
19077 implementing your own stub file, you can still ignore the details: start
19078 with one of the existing stub files. @file{sparc-stub.c} is the best
19079 organized, and therefore the easiest to read.)
19081 @cindex remote serial debugging, overview
19082 To debug a program running on another machine (the debugging
19083 @dfn{target} machine), you must first arrange for all the usual
19084 prerequisites for the program to run by itself. For example, for a C
19089 A startup routine to set up the C runtime environment; these usually
19090 have a name like @file{crt0}. The startup routine may be supplied by
19091 your hardware supplier, or you may have to write your own.
19094 A C subroutine library to support your program's
19095 subroutine calls, notably managing input and output.
19098 A way of getting your program to the other machine---for example, a
19099 download program. These are often supplied by the hardware
19100 manufacturer, but you may have to write your own from hardware
19104 The next step is to arrange for your program to use a serial port to
19105 communicate with the machine where @value{GDBN} is running (the @dfn{host}
19106 machine). In general terms, the scheme looks like this:
19110 @value{GDBN} already understands how to use this protocol; when everything
19111 else is set up, you can simply use the @samp{target remote} command
19112 (@pxref{Targets,,Specifying a Debugging Target}).
19114 @item On the target,
19115 you must link with your program a few special-purpose subroutines that
19116 implement the @value{GDBN} remote serial protocol. The file containing these
19117 subroutines is called a @dfn{debugging stub}.
19119 On certain remote targets, you can use an auxiliary program
19120 @code{gdbserver} instead of linking a stub into your program.
19121 @xref{Server,,Using the @code{gdbserver} Program}, for details.
19124 The debugging stub is specific to the architecture of the remote
19125 machine; for example, use @file{sparc-stub.c} to debug programs on
19128 @cindex remote serial stub list
19129 These working remote stubs are distributed with @value{GDBN}:
19134 @cindex @file{i386-stub.c}
19137 For Intel 386 and compatible architectures.
19140 @cindex @file{m68k-stub.c}
19141 @cindex Motorola 680x0
19143 For Motorola 680x0 architectures.
19146 @cindex @file{sh-stub.c}
19149 For Renesas SH architectures.
19152 @cindex @file{sparc-stub.c}
19154 For @sc{sparc} architectures.
19156 @item sparcl-stub.c
19157 @cindex @file{sparcl-stub.c}
19160 For Fujitsu @sc{sparclite} architectures.
19164 The @file{README} file in the @value{GDBN} distribution may list other
19165 recently added stubs.
19168 * Stub Contents:: What the stub can do for you
19169 * Bootstrapping:: What you must do for the stub
19170 * Debug Session:: Putting it all together
19173 @node Stub Contents
19174 @subsection What the Stub Can Do for You
19176 @cindex remote serial stub
19177 The debugging stub for your architecture supplies these three
19181 @item set_debug_traps
19182 @findex set_debug_traps
19183 @cindex remote serial stub, initialization
19184 This routine arranges for @code{handle_exception} to run when your
19185 program stops. You must call this subroutine explicitly in your
19186 program's startup code.
19188 @item handle_exception
19189 @findex handle_exception
19190 @cindex remote serial stub, main routine
19191 This is the central workhorse, but your program never calls it
19192 explicitly---the setup code arranges for @code{handle_exception} to
19193 run when a trap is triggered.
19195 @code{handle_exception} takes control when your program stops during
19196 execution (for example, on a breakpoint), and mediates communications
19197 with @value{GDBN} on the host machine. This is where the communications
19198 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
19199 representative on the target machine. It begins by sending summary
19200 information on the state of your program, then continues to execute,
19201 retrieving and transmitting any information @value{GDBN} needs, until you
19202 execute a @value{GDBN} command that makes your program resume; at that point,
19203 @code{handle_exception} returns control to your own code on the target
19207 @cindex @code{breakpoint} subroutine, remote
19208 Use this auxiliary subroutine to make your program contain a
19209 breakpoint. Depending on the particular situation, this may be the only
19210 way for @value{GDBN} to get control. For instance, if your target
19211 machine has some sort of interrupt button, you won't need to call this;
19212 pressing the interrupt button transfers control to
19213 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
19214 simply receiving characters on the serial port may also trigger a trap;
19215 again, in that situation, you don't need to call @code{breakpoint} from
19216 your own program---simply running @samp{target remote} from the host
19217 @value{GDBN} session gets control.
19219 Call @code{breakpoint} if none of these is true, or if you simply want
19220 to make certain your program stops at a predetermined point for the
19221 start of your debugging session.
19224 @node Bootstrapping
19225 @subsection What You Must Do for the Stub
19227 @cindex remote stub, support routines
19228 The debugging stubs that come with @value{GDBN} are set up for a particular
19229 chip architecture, but they have no information about the rest of your
19230 debugging target machine.
19232 First of all you need to tell the stub how to communicate with the
19236 @item int getDebugChar()
19237 @findex getDebugChar
19238 Write this subroutine to read a single character from the serial port.
19239 It may be identical to @code{getchar} for your target system; a
19240 different name is used to allow you to distinguish the two if you wish.
19242 @item void putDebugChar(int)
19243 @findex putDebugChar
19244 Write this subroutine to write a single character to the serial port.
19245 It may be identical to @code{putchar} for your target system; a
19246 different name is used to allow you to distinguish the two if you wish.
19249 @cindex control C, and remote debugging
19250 @cindex interrupting remote targets
19251 If you want @value{GDBN} to be able to stop your program while it is
19252 running, you need to use an interrupt-driven serial driver, and arrange
19253 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
19254 character). That is the character which @value{GDBN} uses to tell the
19255 remote system to stop.
19257 Getting the debugging target to return the proper status to @value{GDBN}
19258 probably requires changes to the standard stub; one quick and dirty way
19259 is to just execute a breakpoint instruction (the ``dirty'' part is that
19260 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
19262 Other routines you need to supply are:
19265 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
19266 @findex exceptionHandler
19267 Write this function to install @var{exception_address} in the exception
19268 handling tables. You need to do this because the stub does not have any
19269 way of knowing what the exception handling tables on your target system
19270 are like (for example, the processor's table might be in @sc{rom},
19271 containing entries which point to a table in @sc{ram}).
19272 @var{exception_number} is the exception number which should be changed;
19273 its meaning is architecture-dependent (for example, different numbers
19274 might represent divide by zero, misaligned access, etc). When this
19275 exception occurs, control should be transferred directly to
19276 @var{exception_address}, and the processor state (stack, registers,
19277 and so on) should be just as it is when a processor exception occurs. So if
19278 you want to use a jump instruction to reach @var{exception_address}, it
19279 should be a simple jump, not a jump to subroutine.
19281 For the 386, @var{exception_address} should be installed as an interrupt
19282 gate so that interrupts are masked while the handler runs. The gate
19283 should be at privilege level 0 (the most privileged level). The
19284 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
19285 help from @code{exceptionHandler}.
19287 @item void flush_i_cache()
19288 @findex flush_i_cache
19289 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
19290 instruction cache, if any, on your target machine. If there is no
19291 instruction cache, this subroutine may be a no-op.
19293 On target machines that have instruction caches, @value{GDBN} requires this
19294 function to make certain that the state of your program is stable.
19298 You must also make sure this library routine is available:
19301 @item void *memset(void *, int, int)
19303 This is the standard library function @code{memset} that sets an area of
19304 memory to a known value. If you have one of the free versions of
19305 @code{libc.a}, @code{memset} can be found there; otherwise, you must
19306 either obtain it from your hardware manufacturer, or write your own.
19309 If you do not use the GNU C compiler, you may need other standard
19310 library subroutines as well; this varies from one stub to another,
19311 but in general the stubs are likely to use any of the common library
19312 subroutines which @code{@value{NGCC}} generates as inline code.
19315 @node Debug Session
19316 @subsection Putting it All Together
19318 @cindex remote serial debugging summary
19319 In summary, when your program is ready to debug, you must follow these
19324 Make sure you have defined the supporting low-level routines
19325 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
19327 @code{getDebugChar}, @code{putDebugChar},
19328 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
19332 Insert these lines in your program's startup code, before the main
19333 procedure is called:
19340 On some machines, when a breakpoint trap is raised, the hardware
19341 automatically makes the PC point to the instruction after the
19342 breakpoint. If your machine doesn't do that, you may need to adjust
19343 @code{handle_exception} to arrange for it to return to the instruction
19344 after the breakpoint on this first invocation, so that your program
19345 doesn't keep hitting the initial breakpoint instead of making
19349 For the 680x0 stub only, you need to provide a variable called
19350 @code{exceptionHook}. Normally you just use:
19353 void (*exceptionHook)() = 0;
19357 but if before calling @code{set_debug_traps}, you set it to point to a
19358 function in your program, that function is called when
19359 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
19360 error). The function indicated by @code{exceptionHook} is called with
19361 one parameter: an @code{int} which is the exception number.
19364 Compile and link together: your program, the @value{GDBN} debugging stub for
19365 your target architecture, and the supporting subroutines.
19368 Make sure you have a serial connection between your target machine and
19369 the @value{GDBN} host, and identify the serial port on the host.
19372 @c The "remote" target now provides a `load' command, so we should
19373 @c document that. FIXME.
19374 Download your program to your target machine (or get it there by
19375 whatever means the manufacturer provides), and start it.
19378 Start @value{GDBN} on the host, and connect to the target
19379 (@pxref{Connecting,,Connecting to a Remote Target}).
19383 @node Configurations
19384 @chapter Configuration-Specific Information
19386 While nearly all @value{GDBN} commands are available for all native and
19387 cross versions of the debugger, there are some exceptions. This chapter
19388 describes things that are only available in certain configurations.
19390 There are three major categories of configurations: native
19391 configurations, where the host and target are the same, embedded
19392 operating system configurations, which are usually the same for several
19393 different processor architectures, and bare embedded processors, which
19394 are quite different from each other.
19399 * Embedded Processors::
19406 This section describes details specific to particular native
19411 * BSD libkvm Interface:: Debugging BSD kernel memory images
19412 * SVR4 Process Information:: SVR4 process information
19413 * DJGPP Native:: Features specific to the DJGPP port
19414 * Cygwin Native:: Features specific to the Cygwin port
19415 * Hurd Native:: Features specific to @sc{gnu} Hurd
19416 * Darwin:: Features specific to Darwin
19422 On HP-UX systems, if you refer to a function or variable name that
19423 begins with a dollar sign, @value{GDBN} searches for a user or system
19424 name first, before it searches for a convenience variable.
19427 @node BSD libkvm Interface
19428 @subsection BSD libkvm Interface
19431 @cindex kernel memory image
19432 @cindex kernel crash dump
19434 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
19435 interface that provides a uniform interface for accessing kernel virtual
19436 memory images, including live systems and crash dumps. @value{GDBN}
19437 uses this interface to allow you to debug live kernels and kernel crash
19438 dumps on many native BSD configurations. This is implemented as a
19439 special @code{kvm} debugging target. For debugging a live system, load
19440 the currently running kernel into @value{GDBN} and connect to the
19444 (@value{GDBP}) @b{target kvm}
19447 For debugging crash dumps, provide the file name of the crash dump as an
19451 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
19454 Once connected to the @code{kvm} target, the following commands are
19460 Set current context from the @dfn{Process Control Block} (PCB) address.
19463 Set current context from proc address. This command isn't available on
19464 modern FreeBSD systems.
19467 @node SVR4 Process Information
19468 @subsection SVR4 Process Information
19470 @cindex examine process image
19471 @cindex process info via @file{/proc}
19473 Many versions of SVR4 and compatible systems provide a facility called
19474 @samp{/proc} that can be used to examine the image of a running
19475 process using file-system subroutines.
19477 If @value{GDBN} is configured for an operating system with this
19478 facility, the command @code{info proc} is available to report
19479 information about the process running your program, or about any
19480 process running on your system. This includes, as of this writing,
19481 @sc{gnu}/Linux, OSF/1 (Digital Unix), Solaris, and Irix, but
19482 not HP-UX, for example.
19484 This command may also work on core files that were created on a system
19485 that has the @samp{/proc} facility.
19491 @itemx info proc @var{process-id}
19492 Summarize available information about any running process. If a
19493 process ID is specified by @var{process-id}, display information about
19494 that process; otherwise display information about the program being
19495 debugged. The summary includes the debugged process ID, the command
19496 line used to invoke it, its current working directory, and its
19497 executable file's absolute file name.
19499 On some systems, @var{process-id} can be of the form
19500 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
19501 within a process. If the optional @var{pid} part is missing, it means
19502 a thread from the process being debugged (the leading @samp{/} still
19503 needs to be present, or else @value{GDBN} will interpret the number as
19504 a process ID rather than a thread ID).
19506 @item info proc cmdline
19507 @cindex info proc cmdline
19508 Show the original command line of the process. This command is
19509 specific to @sc{gnu}/Linux.
19511 @item info proc cwd
19512 @cindex info proc cwd
19513 Show the current working directory of the process. This command is
19514 specific to @sc{gnu}/Linux.
19516 @item info proc exe
19517 @cindex info proc exe
19518 Show the name of executable of the process. This command is specific
19521 @item info proc mappings
19522 @cindex memory address space mappings
19523 Report the memory address space ranges accessible in the program, with
19524 information on whether the process has read, write, or execute access
19525 rights to each range. On @sc{gnu}/Linux systems, each memory range
19526 includes the object file which is mapped to that range, instead of the
19527 memory access rights to that range.
19529 @item info proc stat
19530 @itemx info proc status
19531 @cindex process detailed status information
19532 These subcommands are specific to @sc{gnu}/Linux systems. They show
19533 the process-related information, including the user ID and group ID;
19534 how many threads are there in the process; its virtual memory usage;
19535 the signals that are pending, blocked, and ignored; its TTY; its
19536 consumption of system and user time; its stack size; its @samp{nice}
19537 value; etc. For more information, see the @samp{proc} man page
19538 (type @kbd{man 5 proc} from your shell prompt).
19540 @item info proc all
19541 Show all the information about the process described under all of the
19542 above @code{info proc} subcommands.
19545 @comment These sub-options of 'info proc' were not included when
19546 @comment procfs.c was re-written. Keep their descriptions around
19547 @comment against the day when someone finds the time to put them back in.
19548 @kindex info proc times
19549 @item info proc times
19550 Starting time, user CPU time, and system CPU time for your program and
19553 @kindex info proc id
19555 Report on the process IDs related to your program: its own process ID,
19556 the ID of its parent, the process group ID, and the session ID.
19559 @item set procfs-trace
19560 @kindex set procfs-trace
19561 @cindex @code{procfs} API calls
19562 This command enables and disables tracing of @code{procfs} API calls.
19564 @item show procfs-trace
19565 @kindex show procfs-trace
19566 Show the current state of @code{procfs} API call tracing.
19568 @item set procfs-file @var{file}
19569 @kindex set procfs-file
19570 Tell @value{GDBN} to write @code{procfs} API trace to the named
19571 @var{file}. @value{GDBN} appends the trace info to the previous
19572 contents of the file. The default is to display the trace on the
19575 @item show procfs-file
19576 @kindex show procfs-file
19577 Show the file to which @code{procfs} API trace is written.
19579 @item proc-trace-entry
19580 @itemx proc-trace-exit
19581 @itemx proc-untrace-entry
19582 @itemx proc-untrace-exit
19583 @kindex proc-trace-entry
19584 @kindex proc-trace-exit
19585 @kindex proc-untrace-entry
19586 @kindex proc-untrace-exit
19587 These commands enable and disable tracing of entries into and exits
19588 from the @code{syscall} interface.
19591 @kindex info pidlist
19592 @cindex process list, QNX Neutrino
19593 For QNX Neutrino only, this command displays the list of all the
19594 processes and all the threads within each process.
19597 @kindex info meminfo
19598 @cindex mapinfo list, QNX Neutrino
19599 For QNX Neutrino only, this command displays the list of all mapinfos.
19603 @subsection Features for Debugging @sc{djgpp} Programs
19604 @cindex @sc{djgpp} debugging
19605 @cindex native @sc{djgpp} debugging
19606 @cindex MS-DOS-specific commands
19609 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
19610 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
19611 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
19612 top of real-mode DOS systems and their emulations.
19614 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
19615 defines a few commands specific to the @sc{djgpp} port. This
19616 subsection describes those commands.
19621 This is a prefix of @sc{djgpp}-specific commands which print
19622 information about the target system and important OS structures.
19625 @cindex MS-DOS system info
19626 @cindex free memory information (MS-DOS)
19627 @item info dos sysinfo
19628 This command displays assorted information about the underlying
19629 platform: the CPU type and features, the OS version and flavor, the
19630 DPMI version, and the available conventional and DPMI memory.
19635 @cindex segment descriptor tables
19636 @cindex descriptor tables display
19638 @itemx info dos ldt
19639 @itemx info dos idt
19640 These 3 commands display entries from, respectively, Global, Local,
19641 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
19642 tables are data structures which store a descriptor for each segment
19643 that is currently in use. The segment's selector is an index into a
19644 descriptor table; the table entry for that index holds the
19645 descriptor's base address and limit, and its attributes and access
19648 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
19649 segment (used for both data and the stack), and a DOS segment (which
19650 allows access to DOS/BIOS data structures and absolute addresses in
19651 conventional memory). However, the DPMI host will usually define
19652 additional segments in order to support the DPMI environment.
19654 @cindex garbled pointers
19655 These commands allow to display entries from the descriptor tables.
19656 Without an argument, all entries from the specified table are
19657 displayed. An argument, which should be an integer expression, means
19658 display a single entry whose index is given by the argument. For
19659 example, here's a convenient way to display information about the
19660 debugged program's data segment:
19663 @exdent @code{(@value{GDBP}) info dos ldt $ds}
19664 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
19668 This comes in handy when you want to see whether a pointer is outside
19669 the data segment's limit (i.e.@: @dfn{garbled}).
19671 @cindex page tables display (MS-DOS)
19673 @itemx info dos pte
19674 These two commands display entries from, respectively, the Page
19675 Directory and the Page Tables. Page Directories and Page Tables are
19676 data structures which control how virtual memory addresses are mapped
19677 into physical addresses. A Page Table includes an entry for every
19678 page of memory that is mapped into the program's address space; there
19679 may be several Page Tables, each one holding up to 4096 entries. A
19680 Page Directory has up to 4096 entries, one each for every Page Table
19681 that is currently in use.
19683 Without an argument, @kbd{info dos pde} displays the entire Page
19684 Directory, and @kbd{info dos pte} displays all the entries in all of
19685 the Page Tables. An argument, an integer expression, given to the
19686 @kbd{info dos pde} command means display only that entry from the Page
19687 Directory table. An argument given to the @kbd{info dos pte} command
19688 means display entries from a single Page Table, the one pointed to by
19689 the specified entry in the Page Directory.
19691 @cindex direct memory access (DMA) on MS-DOS
19692 These commands are useful when your program uses @dfn{DMA} (Direct
19693 Memory Access), which needs physical addresses to program the DMA
19696 These commands are supported only with some DPMI servers.
19698 @cindex physical address from linear address
19699 @item info dos address-pte @var{addr}
19700 This command displays the Page Table entry for a specified linear
19701 address. The argument @var{addr} is a linear address which should
19702 already have the appropriate segment's base address added to it,
19703 because this command accepts addresses which may belong to @emph{any}
19704 segment. For example, here's how to display the Page Table entry for
19705 the page where a variable @code{i} is stored:
19708 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
19709 @exdent @code{Page Table entry for address 0x11a00d30:}
19710 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
19714 This says that @code{i} is stored at offset @code{0xd30} from the page
19715 whose physical base address is @code{0x02698000}, and shows all the
19716 attributes of that page.
19718 Note that you must cast the addresses of variables to a @code{char *},
19719 since otherwise the value of @code{__djgpp_base_address}, the base
19720 address of all variables and functions in a @sc{djgpp} program, will
19721 be added using the rules of C pointer arithmetics: if @code{i} is
19722 declared an @code{int}, @value{GDBN} will add 4 times the value of
19723 @code{__djgpp_base_address} to the address of @code{i}.
19725 Here's another example, it displays the Page Table entry for the
19729 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
19730 @exdent @code{Page Table entry for address 0x29110:}
19731 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
19735 (The @code{+ 3} offset is because the transfer buffer's address is the
19736 3rd member of the @code{_go32_info_block} structure.) The output
19737 clearly shows that this DPMI server maps the addresses in conventional
19738 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
19739 linear (@code{0x29110}) addresses are identical.
19741 This command is supported only with some DPMI servers.
19744 @cindex DOS serial data link, remote debugging
19745 In addition to native debugging, the DJGPP port supports remote
19746 debugging via a serial data link. The following commands are specific
19747 to remote serial debugging in the DJGPP port of @value{GDBN}.
19750 @kindex set com1base
19751 @kindex set com1irq
19752 @kindex set com2base
19753 @kindex set com2irq
19754 @kindex set com3base
19755 @kindex set com3irq
19756 @kindex set com4base
19757 @kindex set com4irq
19758 @item set com1base @var{addr}
19759 This command sets the base I/O port address of the @file{COM1} serial
19762 @item set com1irq @var{irq}
19763 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
19764 for the @file{COM1} serial port.
19766 There are similar commands @samp{set com2base}, @samp{set com3irq},
19767 etc.@: for setting the port address and the @code{IRQ} lines for the
19770 @kindex show com1base
19771 @kindex show com1irq
19772 @kindex show com2base
19773 @kindex show com2irq
19774 @kindex show com3base
19775 @kindex show com3irq
19776 @kindex show com4base
19777 @kindex show com4irq
19778 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
19779 display the current settings of the base address and the @code{IRQ}
19780 lines used by the COM ports.
19783 @kindex info serial
19784 @cindex DOS serial port status
19785 This command prints the status of the 4 DOS serial ports. For each
19786 port, it prints whether it's active or not, its I/O base address and
19787 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
19788 counts of various errors encountered so far.
19792 @node Cygwin Native
19793 @subsection Features for Debugging MS Windows PE Executables
19794 @cindex MS Windows debugging
19795 @cindex native Cygwin debugging
19796 @cindex Cygwin-specific commands
19798 @value{GDBN} supports native debugging of MS Windows programs, including
19799 DLLs with and without symbolic debugging information.
19801 @cindex Ctrl-BREAK, MS-Windows
19802 @cindex interrupt debuggee on MS-Windows
19803 MS-Windows programs that call @code{SetConsoleMode} to switch off the
19804 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
19805 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
19806 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
19807 sequence, which can be used to interrupt the debuggee even if it
19810 There are various additional Cygwin-specific commands, described in
19811 this section. Working with DLLs that have no debugging symbols is
19812 described in @ref{Non-debug DLL Symbols}.
19817 This is a prefix of MS Windows-specific commands which print
19818 information about the target system and important OS structures.
19820 @item info w32 selector
19821 This command displays information returned by
19822 the Win32 API @code{GetThreadSelectorEntry} function.
19823 It takes an optional argument that is evaluated to
19824 a long value to give the information about this given selector.
19825 Without argument, this command displays information
19826 about the six segment registers.
19828 @item info w32 thread-information-block
19829 This command displays thread specific information stored in the
19830 Thread Information Block (readable on the X86 CPU family using @code{$fs}
19831 selector for 32-bit programs and @code{$gs} for 64-bit programs).
19835 This is a Cygwin-specific alias of @code{info shared}.
19837 @kindex dll-symbols
19839 This command loads symbols from a dll similarly to
19840 add-sym command but without the need to specify a base address.
19842 @kindex set cygwin-exceptions
19843 @cindex debugging the Cygwin DLL
19844 @cindex Cygwin DLL, debugging
19845 @item set cygwin-exceptions @var{mode}
19846 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
19847 happen inside the Cygwin DLL. If @var{mode} is @code{off},
19848 @value{GDBN} will delay recognition of exceptions, and may ignore some
19849 exceptions which seem to be caused by internal Cygwin DLL
19850 ``bookkeeping''. This option is meant primarily for debugging the
19851 Cygwin DLL itself; the default value is @code{off} to avoid annoying
19852 @value{GDBN} users with false @code{SIGSEGV} signals.
19854 @kindex show cygwin-exceptions
19855 @item show cygwin-exceptions
19856 Displays whether @value{GDBN} will break on exceptions that happen
19857 inside the Cygwin DLL itself.
19859 @kindex set new-console
19860 @item set new-console @var{mode}
19861 If @var{mode} is @code{on} the debuggee will
19862 be started in a new console on next start.
19863 If @var{mode} is @code{off}, the debuggee will
19864 be started in the same console as the debugger.
19866 @kindex show new-console
19867 @item show new-console
19868 Displays whether a new console is used
19869 when the debuggee is started.
19871 @kindex set new-group
19872 @item set new-group @var{mode}
19873 This boolean value controls whether the debuggee should
19874 start a new group or stay in the same group as the debugger.
19875 This affects the way the Windows OS handles
19878 @kindex show new-group
19879 @item show new-group
19880 Displays current value of new-group boolean.
19882 @kindex set debugevents
19883 @item set debugevents
19884 This boolean value adds debug output concerning kernel events related
19885 to the debuggee seen by the debugger. This includes events that
19886 signal thread and process creation and exit, DLL loading and
19887 unloading, console interrupts, and debugging messages produced by the
19888 Windows @code{OutputDebugString} API call.
19890 @kindex set debugexec
19891 @item set debugexec
19892 This boolean value adds debug output concerning execute events
19893 (such as resume thread) seen by the debugger.
19895 @kindex set debugexceptions
19896 @item set debugexceptions
19897 This boolean value adds debug output concerning exceptions in the
19898 debuggee seen by the debugger.
19900 @kindex set debugmemory
19901 @item set debugmemory
19902 This boolean value adds debug output concerning debuggee memory reads
19903 and writes by the debugger.
19907 This boolean values specifies whether the debuggee is called
19908 via a shell or directly (default value is on).
19912 Displays if the debuggee will be started with a shell.
19917 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
19920 @node Non-debug DLL Symbols
19921 @subsubsection Support for DLLs without Debugging Symbols
19922 @cindex DLLs with no debugging symbols
19923 @cindex Minimal symbols and DLLs
19925 Very often on windows, some of the DLLs that your program relies on do
19926 not include symbolic debugging information (for example,
19927 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
19928 symbols in a DLL, it relies on the minimal amount of symbolic
19929 information contained in the DLL's export table. This section
19930 describes working with such symbols, known internally to @value{GDBN} as
19931 ``minimal symbols''.
19933 Note that before the debugged program has started execution, no DLLs
19934 will have been loaded. The easiest way around this problem is simply to
19935 start the program --- either by setting a breakpoint or letting the
19936 program run once to completion. It is also possible to force
19937 @value{GDBN} to load a particular DLL before starting the executable ---
19938 see the shared library information in @ref{Files}, or the
19939 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
19940 explicitly loading symbols from a DLL with no debugging information will
19941 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
19942 which may adversely affect symbol lookup performance.
19944 @subsubsection DLL Name Prefixes
19946 In keeping with the naming conventions used by the Microsoft debugging
19947 tools, DLL export symbols are made available with a prefix based on the
19948 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
19949 also entered into the symbol table, so @code{CreateFileA} is often
19950 sufficient. In some cases there will be name clashes within a program
19951 (particularly if the executable itself includes full debugging symbols)
19952 necessitating the use of the fully qualified name when referring to the
19953 contents of the DLL. Use single-quotes around the name to avoid the
19954 exclamation mark (``!'') being interpreted as a language operator.
19956 Note that the internal name of the DLL may be all upper-case, even
19957 though the file name of the DLL is lower-case, or vice-versa. Since
19958 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
19959 some confusion. If in doubt, try the @code{info functions} and
19960 @code{info variables} commands or even @code{maint print msymbols}
19961 (@pxref{Symbols}). Here's an example:
19964 (@value{GDBP}) info function CreateFileA
19965 All functions matching regular expression "CreateFileA":
19967 Non-debugging symbols:
19968 0x77e885f4 CreateFileA
19969 0x77e885f4 KERNEL32!CreateFileA
19973 (@value{GDBP}) info function !
19974 All functions matching regular expression "!":
19976 Non-debugging symbols:
19977 0x6100114c cygwin1!__assert
19978 0x61004034 cygwin1!_dll_crt0@@0
19979 0x61004240 cygwin1!dll_crt0(per_process *)
19983 @subsubsection Working with Minimal Symbols
19985 Symbols extracted from a DLL's export table do not contain very much
19986 type information. All that @value{GDBN} can do is guess whether a symbol
19987 refers to a function or variable depending on the linker section that
19988 contains the symbol. Also note that the actual contents of the memory
19989 contained in a DLL are not available unless the program is running. This
19990 means that you cannot examine the contents of a variable or disassemble
19991 a function within a DLL without a running program.
19993 Variables are generally treated as pointers and dereferenced
19994 automatically. For this reason, it is often necessary to prefix a
19995 variable name with the address-of operator (``&'') and provide explicit
19996 type information in the command. Here's an example of the type of
20000 (@value{GDBP}) print 'cygwin1!__argv'
20005 (@value{GDBP}) x 'cygwin1!__argv'
20006 0x10021610: "\230y\""
20009 And two possible solutions:
20012 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
20013 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
20017 (@value{GDBP}) x/2x &'cygwin1!__argv'
20018 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
20019 (@value{GDBP}) x/x 0x10021608
20020 0x10021608: 0x0022fd98
20021 (@value{GDBP}) x/s 0x0022fd98
20022 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
20025 Setting a break point within a DLL is possible even before the program
20026 starts execution. However, under these circumstances, @value{GDBN} can't
20027 examine the initial instructions of the function in order to skip the
20028 function's frame set-up code. You can work around this by using ``*&''
20029 to set the breakpoint at a raw memory address:
20032 (@value{GDBP}) break *&'python22!PyOS_Readline'
20033 Breakpoint 1 at 0x1e04eff0
20036 The author of these extensions is not entirely convinced that setting a
20037 break point within a shared DLL like @file{kernel32.dll} is completely
20041 @subsection Commands Specific to @sc{gnu} Hurd Systems
20042 @cindex @sc{gnu} Hurd debugging
20044 This subsection describes @value{GDBN} commands specific to the
20045 @sc{gnu} Hurd native debugging.
20050 @kindex set signals@r{, Hurd command}
20051 @kindex set sigs@r{, Hurd command}
20052 This command toggles the state of inferior signal interception by
20053 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
20054 affected by this command. @code{sigs} is a shorthand alias for
20059 @kindex show signals@r{, Hurd command}
20060 @kindex show sigs@r{, Hurd command}
20061 Show the current state of intercepting inferior's signals.
20063 @item set signal-thread
20064 @itemx set sigthread
20065 @kindex set signal-thread
20066 @kindex set sigthread
20067 This command tells @value{GDBN} which thread is the @code{libc} signal
20068 thread. That thread is run when a signal is delivered to a running
20069 process. @code{set sigthread} is the shorthand alias of @code{set
20072 @item show signal-thread
20073 @itemx show sigthread
20074 @kindex show signal-thread
20075 @kindex show sigthread
20076 These two commands show which thread will run when the inferior is
20077 delivered a signal.
20080 @kindex set stopped@r{, Hurd command}
20081 This commands tells @value{GDBN} that the inferior process is stopped,
20082 as with the @code{SIGSTOP} signal. The stopped process can be
20083 continued by delivering a signal to it.
20086 @kindex show stopped@r{, Hurd command}
20087 This command shows whether @value{GDBN} thinks the debuggee is
20090 @item set exceptions
20091 @kindex set exceptions@r{, Hurd command}
20092 Use this command to turn off trapping of exceptions in the inferior.
20093 When exception trapping is off, neither breakpoints nor
20094 single-stepping will work. To restore the default, set exception
20097 @item show exceptions
20098 @kindex show exceptions@r{, Hurd command}
20099 Show the current state of trapping exceptions in the inferior.
20101 @item set task pause
20102 @kindex set task@r{, Hurd commands}
20103 @cindex task attributes (@sc{gnu} Hurd)
20104 @cindex pause current task (@sc{gnu} Hurd)
20105 This command toggles task suspension when @value{GDBN} has control.
20106 Setting it to on takes effect immediately, and the task is suspended
20107 whenever @value{GDBN} gets control. Setting it to off will take
20108 effect the next time the inferior is continued. If this option is set
20109 to off, you can use @code{set thread default pause on} or @code{set
20110 thread pause on} (see below) to pause individual threads.
20112 @item show task pause
20113 @kindex show task@r{, Hurd commands}
20114 Show the current state of task suspension.
20116 @item set task detach-suspend-count
20117 @cindex task suspend count
20118 @cindex detach from task, @sc{gnu} Hurd
20119 This command sets the suspend count the task will be left with when
20120 @value{GDBN} detaches from it.
20122 @item show task detach-suspend-count
20123 Show the suspend count the task will be left with when detaching.
20125 @item set task exception-port
20126 @itemx set task excp
20127 @cindex task exception port, @sc{gnu} Hurd
20128 This command sets the task exception port to which @value{GDBN} will
20129 forward exceptions. The argument should be the value of the @dfn{send
20130 rights} of the task. @code{set task excp} is a shorthand alias.
20132 @item set noninvasive
20133 @cindex noninvasive task options
20134 This command switches @value{GDBN} to a mode that is the least
20135 invasive as far as interfering with the inferior is concerned. This
20136 is the same as using @code{set task pause}, @code{set exceptions}, and
20137 @code{set signals} to values opposite to the defaults.
20139 @item info send-rights
20140 @itemx info receive-rights
20141 @itemx info port-rights
20142 @itemx info port-sets
20143 @itemx info dead-names
20146 @cindex send rights, @sc{gnu} Hurd
20147 @cindex receive rights, @sc{gnu} Hurd
20148 @cindex port rights, @sc{gnu} Hurd
20149 @cindex port sets, @sc{gnu} Hurd
20150 @cindex dead names, @sc{gnu} Hurd
20151 These commands display information about, respectively, send rights,
20152 receive rights, port rights, port sets, and dead names of a task.
20153 There are also shorthand aliases: @code{info ports} for @code{info
20154 port-rights} and @code{info psets} for @code{info port-sets}.
20156 @item set thread pause
20157 @kindex set thread@r{, Hurd command}
20158 @cindex thread properties, @sc{gnu} Hurd
20159 @cindex pause current thread (@sc{gnu} Hurd)
20160 This command toggles current thread suspension when @value{GDBN} has
20161 control. Setting it to on takes effect immediately, and the current
20162 thread is suspended whenever @value{GDBN} gets control. Setting it to
20163 off will take effect the next time the inferior is continued.
20164 Normally, this command has no effect, since when @value{GDBN} has
20165 control, the whole task is suspended. However, if you used @code{set
20166 task pause off} (see above), this command comes in handy to suspend
20167 only the current thread.
20169 @item show thread pause
20170 @kindex show thread@r{, Hurd command}
20171 This command shows the state of current thread suspension.
20173 @item set thread run
20174 This command sets whether the current thread is allowed to run.
20176 @item show thread run
20177 Show whether the current thread is allowed to run.
20179 @item set thread detach-suspend-count
20180 @cindex thread suspend count, @sc{gnu} Hurd
20181 @cindex detach from thread, @sc{gnu} Hurd
20182 This command sets the suspend count @value{GDBN} will leave on a
20183 thread when detaching. This number is relative to the suspend count
20184 found by @value{GDBN} when it notices the thread; use @code{set thread
20185 takeover-suspend-count} to force it to an absolute value.
20187 @item show thread detach-suspend-count
20188 Show the suspend count @value{GDBN} will leave on the thread when
20191 @item set thread exception-port
20192 @itemx set thread excp
20193 Set the thread exception port to which to forward exceptions. This
20194 overrides the port set by @code{set task exception-port} (see above).
20195 @code{set thread excp} is the shorthand alias.
20197 @item set thread takeover-suspend-count
20198 Normally, @value{GDBN}'s thread suspend counts are relative to the
20199 value @value{GDBN} finds when it notices each thread. This command
20200 changes the suspend counts to be absolute instead.
20202 @item set thread default
20203 @itemx show thread default
20204 @cindex thread default settings, @sc{gnu} Hurd
20205 Each of the above @code{set thread} commands has a @code{set thread
20206 default} counterpart (e.g., @code{set thread default pause}, @code{set
20207 thread default exception-port}, etc.). The @code{thread default}
20208 variety of commands sets the default thread properties for all
20209 threads; you can then change the properties of individual threads with
20210 the non-default commands.
20217 @value{GDBN} provides the following commands specific to the Darwin target:
20220 @item set debug darwin @var{num}
20221 @kindex set debug darwin
20222 When set to a non zero value, enables debugging messages specific to
20223 the Darwin support. Higher values produce more verbose output.
20225 @item show debug darwin
20226 @kindex show debug darwin
20227 Show the current state of Darwin messages.
20229 @item set debug mach-o @var{num}
20230 @kindex set debug mach-o
20231 When set to a non zero value, enables debugging messages while
20232 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
20233 file format used on Darwin for object and executable files.) Higher
20234 values produce more verbose output. This is a command to diagnose
20235 problems internal to @value{GDBN} and should not be needed in normal
20238 @item show debug mach-o
20239 @kindex show debug mach-o
20240 Show the current state of Mach-O file messages.
20242 @item set mach-exceptions on
20243 @itemx set mach-exceptions off
20244 @kindex set mach-exceptions
20245 On Darwin, faults are first reported as a Mach exception and are then
20246 mapped to a Posix signal. Use this command to turn on trapping of
20247 Mach exceptions in the inferior. This might be sometimes useful to
20248 better understand the cause of a fault. The default is off.
20250 @item show mach-exceptions
20251 @kindex show mach-exceptions
20252 Show the current state of exceptions trapping.
20257 @section Embedded Operating Systems
20259 This section describes configurations involving the debugging of
20260 embedded operating systems that are available for several different
20264 * VxWorks:: Using @value{GDBN} with VxWorks
20267 @value{GDBN} includes the ability to debug programs running on
20268 various real-time operating systems.
20271 @subsection Using @value{GDBN} with VxWorks
20277 @kindex target vxworks
20278 @item target vxworks @var{machinename}
20279 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
20280 is the target system's machine name or IP address.
20284 On VxWorks, @code{load} links @var{filename} dynamically on the
20285 current target system as well as adding its symbols in @value{GDBN}.
20287 @value{GDBN} enables developers to spawn and debug tasks running on networked
20288 VxWorks targets from a Unix host. Already-running tasks spawned from
20289 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
20290 both the Unix host and on the VxWorks target. The program
20291 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
20292 installed with the name @code{vxgdb}, to distinguish it from a
20293 @value{GDBN} for debugging programs on the host itself.)
20296 @item VxWorks-timeout @var{args}
20297 @kindex vxworks-timeout
20298 All VxWorks-based targets now support the option @code{vxworks-timeout}.
20299 This option is set by the user, and @var{args} represents the number of
20300 seconds @value{GDBN} waits for responses to rpc's. You might use this if
20301 your VxWorks target is a slow software simulator or is on the far side
20302 of a thin network line.
20305 The following information on connecting to VxWorks was current when
20306 this manual was produced; newer releases of VxWorks may use revised
20309 @findex INCLUDE_RDB
20310 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
20311 to include the remote debugging interface routines in the VxWorks
20312 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
20313 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
20314 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
20315 source debugging task @code{tRdbTask} when VxWorks is booted. For more
20316 information on configuring and remaking VxWorks, see the manufacturer's
20318 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
20320 Once you have included @file{rdb.a} in your VxWorks system image and set
20321 your Unix execution search path to find @value{GDBN}, you are ready to
20322 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
20323 @code{vxgdb}, depending on your installation).
20325 @value{GDBN} comes up showing the prompt:
20332 * VxWorks Connection:: Connecting to VxWorks
20333 * VxWorks Download:: VxWorks download
20334 * VxWorks Attach:: Running tasks
20337 @node VxWorks Connection
20338 @subsubsection Connecting to VxWorks
20340 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
20341 network. To connect to a target whose host name is ``@code{tt}'', type:
20344 (vxgdb) target vxworks tt
20348 @value{GDBN} displays messages like these:
20351 Attaching remote machine across net...
20356 @value{GDBN} then attempts to read the symbol tables of any object modules
20357 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
20358 these files by searching the directories listed in the command search
20359 path (@pxref{Environment, ,Your Program's Environment}); if it fails
20360 to find an object file, it displays a message such as:
20363 prog.o: No such file or directory.
20366 When this happens, add the appropriate directory to the search path with
20367 the @value{GDBN} command @code{path}, and execute the @code{target}
20370 @node VxWorks Download
20371 @subsubsection VxWorks Download
20373 @cindex download to VxWorks
20374 If you have connected to the VxWorks target and you want to debug an
20375 object that has not yet been loaded, you can use the @value{GDBN}
20376 @code{load} command to download a file from Unix to VxWorks
20377 incrementally. The object file given as an argument to the @code{load}
20378 command is actually opened twice: first by the VxWorks target in order
20379 to download the code, then by @value{GDBN} in order to read the symbol
20380 table. This can lead to problems if the current working directories on
20381 the two systems differ. If both systems have NFS mounted the same
20382 filesystems, you can avoid these problems by using absolute paths.
20383 Otherwise, it is simplest to set the working directory on both systems
20384 to the directory in which the object file resides, and then to reference
20385 the file by its name, without any path. For instance, a program
20386 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
20387 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
20388 program, type this on VxWorks:
20391 -> cd "@var{vxpath}/vw/demo/rdb"
20395 Then, in @value{GDBN}, type:
20398 (vxgdb) cd @var{hostpath}/vw/demo/rdb
20399 (vxgdb) load prog.o
20402 @value{GDBN} displays a response similar to this:
20405 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
20408 You can also use the @code{load} command to reload an object module
20409 after editing and recompiling the corresponding source file. Note that
20410 this makes @value{GDBN} delete all currently-defined breakpoints,
20411 auto-displays, and convenience variables, and to clear the value
20412 history. (This is necessary in order to preserve the integrity of
20413 debugger's data structures that reference the target system's symbol
20416 @node VxWorks Attach
20417 @subsubsection Running Tasks
20419 @cindex running VxWorks tasks
20420 You can also attach to an existing task using the @code{attach} command as
20424 (vxgdb) attach @var{task}
20428 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
20429 or suspended when you attach to it. Running tasks are suspended at
20430 the time of attachment.
20432 @node Embedded Processors
20433 @section Embedded Processors
20435 This section goes into details specific to particular embedded
20438 @cindex send command to simulator
20439 Whenever a specific embedded processor has a simulator, @value{GDBN}
20440 allows to send an arbitrary command to the simulator.
20443 @item sim @var{command}
20444 @kindex sim@r{, a command}
20445 Send an arbitrary @var{command} string to the simulator. Consult the
20446 documentation for the specific simulator in use for information about
20447 acceptable commands.
20453 * M32R/D:: Renesas M32R/D
20454 * M68K:: Motorola M68K
20455 * MicroBlaze:: Xilinx MicroBlaze
20456 * MIPS Embedded:: MIPS Embedded
20457 * PowerPC Embedded:: PowerPC Embedded
20458 * PA:: HP PA Embedded
20459 * Sparclet:: Tsqware Sparclet
20460 * Sparclite:: Fujitsu Sparclite
20461 * Z8000:: Zilog Z8000
20464 * Super-H:: Renesas Super-H
20473 @item target rdi @var{dev}
20474 ARM Angel monitor, via RDI library interface to ADP protocol. You may
20475 use this target to communicate with both boards running the Angel
20476 monitor, or with the EmbeddedICE JTAG debug device.
20479 @item target rdp @var{dev}
20484 @value{GDBN} provides the following ARM-specific commands:
20487 @item set arm disassembler
20489 This commands selects from a list of disassembly styles. The
20490 @code{"std"} style is the standard style.
20492 @item show arm disassembler
20494 Show the current disassembly style.
20496 @item set arm apcs32
20497 @cindex ARM 32-bit mode
20498 This command toggles ARM operation mode between 32-bit and 26-bit.
20500 @item show arm apcs32
20501 Display the current usage of the ARM 32-bit mode.
20503 @item set arm fpu @var{fputype}
20504 This command sets the ARM floating-point unit (FPU) type. The
20505 argument @var{fputype} can be one of these:
20509 Determine the FPU type by querying the OS ABI.
20511 Software FPU, with mixed-endian doubles on little-endian ARM
20514 GCC-compiled FPA co-processor.
20516 Software FPU with pure-endian doubles.
20522 Show the current type of the FPU.
20525 This command forces @value{GDBN} to use the specified ABI.
20528 Show the currently used ABI.
20530 @item set arm fallback-mode (arm|thumb|auto)
20531 @value{GDBN} uses the symbol table, when available, to determine
20532 whether instructions are ARM or Thumb. This command controls
20533 @value{GDBN}'s default behavior when the symbol table is not
20534 available. The default is @samp{auto}, which causes @value{GDBN} to
20535 use the current execution mode (from the @code{T} bit in the @code{CPSR}
20538 @item show arm fallback-mode
20539 Show the current fallback instruction mode.
20541 @item set arm force-mode (arm|thumb|auto)
20542 This command overrides use of the symbol table to determine whether
20543 instructions are ARM or Thumb. The default is @samp{auto}, which
20544 causes @value{GDBN} to use the symbol table and then the setting
20545 of @samp{set arm fallback-mode}.
20547 @item show arm force-mode
20548 Show the current forced instruction mode.
20550 @item set debug arm
20551 Toggle whether to display ARM-specific debugging messages from the ARM
20552 target support subsystem.
20554 @item show debug arm
20555 Show whether ARM-specific debugging messages are enabled.
20558 The following commands are available when an ARM target is debugged
20559 using the RDI interface:
20562 @item rdilogfile @r{[}@var{file}@r{]}
20564 @cindex ADP (Angel Debugger Protocol) logging
20565 Set the filename for the ADP (Angel Debugger Protocol) packet log.
20566 With an argument, sets the log file to the specified @var{file}. With
20567 no argument, show the current log file name. The default log file is
20570 @item rdilogenable @r{[}@var{arg}@r{]}
20571 @kindex rdilogenable
20572 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
20573 enables logging, with an argument 0 or @code{"no"} disables it. With
20574 no arguments displays the current setting. When logging is enabled,
20575 ADP packets exchanged between @value{GDBN} and the RDI target device
20576 are logged to a file.
20578 @item set rdiromatzero
20579 @kindex set rdiromatzero
20580 @cindex ROM at zero address, RDI
20581 Tell @value{GDBN} whether the target has ROM at address 0. If on,
20582 vector catching is disabled, so that zero address can be used. If off
20583 (the default), vector catching is enabled. For this command to take
20584 effect, it needs to be invoked prior to the @code{target rdi} command.
20586 @item show rdiromatzero
20587 @kindex show rdiromatzero
20588 Show the current setting of ROM at zero address.
20590 @item set rdiheartbeat
20591 @kindex set rdiheartbeat
20592 @cindex RDI heartbeat
20593 Enable or disable RDI heartbeat packets. It is not recommended to
20594 turn on this option, since it confuses ARM and EPI JTAG interface, as
20595 well as the Angel monitor.
20597 @item show rdiheartbeat
20598 @kindex show rdiheartbeat
20599 Show the setting of RDI heartbeat packets.
20603 @item target sim @r{[}@var{simargs}@r{]} @dots{}
20604 The @value{GDBN} ARM simulator accepts the following optional arguments.
20607 @item --swi-support=@var{type}
20608 Tell the simulator which SWI interfaces to support.
20609 @var{type} may be a comma separated list of the following values.
20610 The default value is @code{all}.
20623 @subsection Renesas M32R/D and M32R/SDI
20626 @kindex target m32r
20627 @item target m32r @var{dev}
20628 Renesas M32R/D ROM monitor.
20630 @kindex target m32rsdi
20631 @item target m32rsdi @var{dev}
20632 Renesas M32R SDI server, connected via parallel port to the board.
20635 The following @value{GDBN} commands are specific to the M32R monitor:
20638 @item set download-path @var{path}
20639 @kindex set download-path
20640 @cindex find downloadable @sc{srec} files (M32R)
20641 Set the default path for finding downloadable @sc{srec} files.
20643 @item show download-path
20644 @kindex show download-path
20645 Show the default path for downloadable @sc{srec} files.
20647 @item set board-address @var{addr}
20648 @kindex set board-address
20649 @cindex M32-EVA target board address
20650 Set the IP address for the M32R-EVA target board.
20652 @item show board-address
20653 @kindex show board-address
20654 Show the current IP address of the target board.
20656 @item set server-address @var{addr}
20657 @kindex set server-address
20658 @cindex download server address (M32R)
20659 Set the IP address for the download server, which is the @value{GDBN}'s
20662 @item show server-address
20663 @kindex show server-address
20664 Display the IP address of the download server.
20666 @item upload @r{[}@var{file}@r{]}
20667 @kindex upload@r{, M32R}
20668 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
20669 upload capability. If no @var{file} argument is given, the current
20670 executable file is uploaded.
20672 @item tload @r{[}@var{file}@r{]}
20673 @kindex tload@r{, M32R}
20674 Test the @code{upload} command.
20677 The following commands are available for M32R/SDI:
20682 @cindex reset SDI connection, M32R
20683 This command resets the SDI connection.
20687 This command shows the SDI connection status.
20690 @kindex debug_chaos
20691 @cindex M32R/Chaos debugging
20692 Instructs the remote that M32R/Chaos debugging is to be used.
20694 @item use_debug_dma
20695 @kindex use_debug_dma
20696 Instructs the remote to use the DEBUG_DMA method of accessing memory.
20699 @kindex use_mon_code
20700 Instructs the remote to use the MON_CODE method of accessing memory.
20703 @kindex use_ib_break
20704 Instructs the remote to set breakpoints by IB break.
20706 @item use_dbt_break
20707 @kindex use_dbt_break
20708 Instructs the remote to set breakpoints by DBT.
20714 The Motorola m68k configuration includes ColdFire support, and a
20715 target command for the following ROM monitor.
20719 @kindex target dbug
20720 @item target dbug @var{dev}
20721 dBUG ROM monitor for Motorola ColdFire.
20726 @subsection MicroBlaze
20727 @cindex Xilinx MicroBlaze
20728 @cindex XMD, Xilinx Microprocessor Debugger
20730 The MicroBlaze is a soft-core processor supported on various Xilinx
20731 FPGAs, such as Spartan or Virtex series. Boards with these processors
20732 usually have JTAG ports which connect to a host system running the Xilinx
20733 Embedded Development Kit (EDK) or Software Development Kit (SDK).
20734 This host system is used to download the configuration bitstream to
20735 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
20736 communicates with the target board using the JTAG interface and
20737 presents a @code{gdbserver} interface to the board. By default
20738 @code{xmd} uses port @code{1234}. (While it is possible to change
20739 this default port, it requires the use of undocumented @code{xmd}
20740 commands. Contact Xilinx support if you need to do this.)
20742 Use these GDB commands to connect to the MicroBlaze target processor.
20745 @item target remote :1234
20746 Use this command to connect to the target if you are running @value{GDBN}
20747 on the same system as @code{xmd}.
20749 @item target remote @var{xmd-host}:1234
20750 Use this command to connect to the target if it is connected to @code{xmd}
20751 running on a different system named @var{xmd-host}.
20754 Use this command to download a program to the MicroBlaze target.
20756 @item set debug microblaze @var{n}
20757 Enable MicroBlaze-specific debugging messages if non-zero.
20759 @item show debug microblaze @var{n}
20760 Show MicroBlaze-specific debugging level.
20763 @node MIPS Embedded
20764 @subsection @acronym{MIPS} Embedded
20766 @cindex @acronym{MIPS} boards
20767 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
20768 @acronym{MIPS} board attached to a serial line. This is available when
20769 you configure @value{GDBN} with @samp{--target=mips-elf}.
20772 Use these @value{GDBN} commands to specify the connection to your target board:
20775 @item target mips @var{port}
20776 @kindex target mips @var{port}
20777 To run a program on the board, start up @code{@value{GDBP}} with the
20778 name of your program as the argument. To connect to the board, use the
20779 command @samp{target mips @var{port}}, where @var{port} is the name of
20780 the serial port connected to the board. If the program has not already
20781 been downloaded to the board, you may use the @code{load} command to
20782 download it. You can then use all the usual @value{GDBN} commands.
20784 For example, this sequence connects to the target board through a serial
20785 port, and loads and runs a program called @var{prog} through the
20789 host$ @value{GDBP} @var{prog}
20790 @value{GDBN} is free software and @dots{}
20791 (@value{GDBP}) target mips /dev/ttyb
20792 (@value{GDBP}) load @var{prog}
20796 @item target mips @var{hostname}:@var{portnumber}
20797 On some @value{GDBN} host configurations, you can specify a TCP
20798 connection (for instance, to a serial line managed by a terminal
20799 concentrator) instead of a serial port, using the syntax
20800 @samp{@var{hostname}:@var{portnumber}}.
20802 @item target pmon @var{port}
20803 @kindex target pmon @var{port}
20806 @item target ddb @var{port}
20807 @kindex target ddb @var{port}
20808 NEC's DDB variant of PMON for Vr4300.
20810 @item target lsi @var{port}
20811 @kindex target lsi @var{port}
20812 LSI variant of PMON.
20814 @kindex target r3900
20815 @item target r3900 @var{dev}
20816 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
20818 @kindex target array
20819 @item target array @var{dev}
20820 Array Tech LSI33K RAID controller board.
20826 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
20829 @item set mipsfpu double
20830 @itemx set mipsfpu single
20831 @itemx set mipsfpu none
20832 @itemx set mipsfpu auto
20833 @itemx show mipsfpu
20834 @kindex set mipsfpu
20835 @kindex show mipsfpu
20836 @cindex @acronym{MIPS} remote floating point
20837 @cindex floating point, @acronym{MIPS} remote
20838 If your target board does not support the @acronym{MIPS} floating point
20839 coprocessor, you should use the command @samp{set mipsfpu none} (if you
20840 need this, you may wish to put the command in your @value{GDBN} init
20841 file). This tells @value{GDBN} how to find the return value of
20842 functions which return floating point values. It also allows
20843 @value{GDBN} to avoid saving the floating point registers when calling
20844 functions on the board. If you are using a floating point coprocessor
20845 with only single precision floating point support, as on the @sc{r4650}
20846 processor, use the command @samp{set mipsfpu single}. The default
20847 double precision floating point coprocessor may be selected using
20848 @samp{set mipsfpu double}.
20850 In previous versions the only choices were double precision or no
20851 floating point, so @samp{set mipsfpu on} will select double precision
20852 and @samp{set mipsfpu off} will select no floating point.
20854 As usual, you can inquire about the @code{mipsfpu} variable with
20855 @samp{show mipsfpu}.
20857 @item set timeout @var{seconds}
20858 @itemx set retransmit-timeout @var{seconds}
20859 @itemx show timeout
20860 @itemx show retransmit-timeout
20861 @cindex @code{timeout}, @acronym{MIPS} protocol
20862 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
20863 @kindex set timeout
20864 @kindex show timeout
20865 @kindex set retransmit-timeout
20866 @kindex show retransmit-timeout
20867 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
20868 remote protocol, with the @code{set timeout @var{seconds}} command. The
20869 default is 5 seconds. Similarly, you can control the timeout used while
20870 waiting for an acknowledgment of a packet with the @code{set
20871 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
20872 You can inspect both values with @code{show timeout} and @code{show
20873 retransmit-timeout}. (These commands are @emph{only} available when
20874 @value{GDBN} is configured for @samp{--target=mips-elf}.)
20876 The timeout set by @code{set timeout} does not apply when @value{GDBN}
20877 is waiting for your program to stop. In that case, @value{GDBN} waits
20878 forever because it has no way of knowing how long the program is going
20879 to run before stopping.
20881 @item set syn-garbage-limit @var{num}
20882 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
20883 @cindex synchronize with remote @acronym{MIPS} target
20884 Limit the maximum number of characters @value{GDBN} should ignore when
20885 it tries to synchronize with the remote target. The default is 10
20886 characters. Setting the limit to -1 means there's no limit.
20888 @item show syn-garbage-limit
20889 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
20890 Show the current limit on the number of characters to ignore when
20891 trying to synchronize with the remote system.
20893 @item set monitor-prompt @var{prompt}
20894 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
20895 @cindex remote monitor prompt
20896 Tell @value{GDBN} to expect the specified @var{prompt} string from the
20897 remote monitor. The default depends on the target:
20907 @item show monitor-prompt
20908 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
20909 Show the current strings @value{GDBN} expects as the prompt from the
20912 @item set monitor-warnings
20913 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
20914 Enable or disable monitor warnings about hardware breakpoints. This
20915 has effect only for the @code{lsi} target. When on, @value{GDBN} will
20916 display warning messages whose codes are returned by the @code{lsi}
20917 PMON monitor for breakpoint commands.
20919 @item show monitor-warnings
20920 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
20921 Show the current setting of printing monitor warnings.
20923 @item pmon @var{command}
20924 @kindex pmon@r{, @acronym{MIPS} remote}
20925 @cindex send PMON command
20926 This command allows sending an arbitrary @var{command} string to the
20927 monitor. The monitor must be in debug mode for this to work.
20930 @node PowerPC Embedded
20931 @subsection PowerPC Embedded
20933 @cindex DVC register
20934 @value{GDBN} supports using the DVC (Data Value Compare) register to
20935 implement in hardware simple hardware watchpoint conditions of the form:
20938 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
20939 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
20942 The DVC register will be automatically used when @value{GDBN} detects
20943 such pattern in a condition expression, and the created watchpoint uses one
20944 debug register (either the @code{exact-watchpoints} option is on and the
20945 variable is scalar, or the variable has a length of one byte). This feature
20946 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
20949 When running on PowerPC embedded processors, @value{GDBN} automatically uses
20950 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
20951 in which case watchpoints using only one debug register are created when
20952 watching variables of scalar types.
20954 You can create an artificial array to watch an arbitrary memory
20955 region using one of the following commands (@pxref{Expressions}):
20958 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
20959 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
20962 PowerPC embedded processors support masked watchpoints. See the discussion
20963 about the @code{mask} argument in @ref{Set Watchpoints}.
20965 @cindex ranged breakpoint
20966 PowerPC embedded processors support hardware accelerated
20967 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
20968 the inferior whenever it executes an instruction at any address within
20969 the range it specifies. To set a ranged breakpoint in @value{GDBN},
20970 use the @code{break-range} command.
20972 @value{GDBN} provides the following PowerPC-specific commands:
20975 @kindex break-range
20976 @item break-range @var{start-location}, @var{end-location}
20977 Set a breakpoint for an address range.
20978 @var{start-location} and @var{end-location} can specify a function name,
20979 a line number, an offset of lines from the current line or from the start
20980 location, or an address of an instruction (see @ref{Specify Location},
20981 for a list of all the possible ways to specify a @var{location}.)
20982 The breakpoint will stop execution of the inferior whenever it
20983 executes an instruction at any address within the specified range,
20984 (including @var{start-location} and @var{end-location}.)
20986 @kindex set powerpc
20987 @item set powerpc soft-float
20988 @itemx show powerpc soft-float
20989 Force @value{GDBN} to use (or not use) a software floating point calling
20990 convention. By default, @value{GDBN} selects the calling convention based
20991 on the selected architecture and the provided executable file.
20993 @item set powerpc vector-abi
20994 @itemx show powerpc vector-abi
20995 Force @value{GDBN} to use the specified calling convention for vector
20996 arguments and return values. The valid options are @samp{auto};
20997 @samp{generic}, to avoid vector registers even if they are present;
20998 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
20999 registers. By default, @value{GDBN} selects the calling convention
21000 based on the selected architecture and the provided executable file.
21002 @item set powerpc exact-watchpoints
21003 @itemx show powerpc exact-watchpoints
21004 Allow @value{GDBN} to use only one debug register when watching a variable
21005 of scalar type, thus assuming that the variable is accessed through the
21006 address of its first byte.
21008 @kindex target dink32
21009 @item target dink32 @var{dev}
21010 DINK32 ROM monitor.
21012 @kindex target ppcbug
21013 @item target ppcbug @var{dev}
21014 @kindex target ppcbug1
21015 @item target ppcbug1 @var{dev}
21016 PPCBUG ROM monitor for PowerPC.
21019 @item target sds @var{dev}
21020 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
21023 @cindex SDS protocol
21024 The following commands specific to the SDS protocol are supported
21028 @item set sdstimeout @var{nsec}
21029 @kindex set sdstimeout
21030 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
21031 default is 2 seconds.
21033 @item show sdstimeout
21034 @kindex show sdstimeout
21035 Show the current value of the SDS timeout.
21037 @item sds @var{command}
21038 @kindex sds@r{, a command}
21039 Send the specified @var{command} string to the SDS monitor.
21044 @subsection HP PA Embedded
21048 @kindex target op50n
21049 @item target op50n @var{dev}
21050 OP50N monitor, running on an OKI HPPA board.
21052 @kindex target w89k
21053 @item target w89k @var{dev}
21054 W89K monitor, running on a Winbond HPPA board.
21059 @subsection Tsqware Sparclet
21063 @value{GDBN} enables developers to debug tasks running on
21064 Sparclet targets from a Unix host.
21065 @value{GDBN} uses code that runs on
21066 both the Unix host and on the Sparclet target. The program
21067 @code{@value{GDBP}} is installed and executed on the Unix host.
21070 @item remotetimeout @var{args}
21071 @kindex remotetimeout
21072 @value{GDBN} supports the option @code{remotetimeout}.
21073 This option is set by the user, and @var{args} represents the number of
21074 seconds @value{GDBN} waits for responses.
21077 @cindex compiling, on Sparclet
21078 When compiling for debugging, include the options @samp{-g} to get debug
21079 information and @samp{-Ttext} to relocate the program to where you wish to
21080 load it on the target. You may also want to add the options @samp{-n} or
21081 @samp{-N} in order to reduce the size of the sections. Example:
21084 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
21087 You can use @code{objdump} to verify that the addresses are what you intended:
21090 sparclet-aout-objdump --headers --syms prog
21093 @cindex running, on Sparclet
21095 your Unix execution search path to find @value{GDBN}, you are ready to
21096 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
21097 (or @code{sparclet-aout-gdb}, depending on your installation).
21099 @value{GDBN} comes up showing the prompt:
21106 * Sparclet File:: Setting the file to debug
21107 * Sparclet Connection:: Connecting to Sparclet
21108 * Sparclet Download:: Sparclet download
21109 * Sparclet Execution:: Running and debugging
21112 @node Sparclet File
21113 @subsubsection Setting File to Debug
21115 The @value{GDBN} command @code{file} lets you choose with program to debug.
21118 (gdbslet) file prog
21122 @value{GDBN} then attempts to read the symbol table of @file{prog}.
21123 @value{GDBN} locates
21124 the file by searching the directories listed in the command search
21126 If the file was compiled with debug information (option @samp{-g}), source
21127 files will be searched as well.
21128 @value{GDBN} locates
21129 the source files by searching the directories listed in the directory search
21130 path (@pxref{Environment, ,Your Program's Environment}).
21132 to find a file, it displays a message such as:
21135 prog: No such file or directory.
21138 When this happens, add the appropriate directories to the search paths with
21139 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
21140 @code{target} command again.
21142 @node Sparclet Connection
21143 @subsubsection Connecting to Sparclet
21145 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
21146 To connect to a target on serial port ``@code{ttya}'', type:
21149 (gdbslet) target sparclet /dev/ttya
21150 Remote target sparclet connected to /dev/ttya
21151 main () at ../prog.c:3
21155 @value{GDBN} displays messages like these:
21161 @node Sparclet Download
21162 @subsubsection Sparclet Download
21164 @cindex download to Sparclet
21165 Once connected to the Sparclet target,
21166 you can use the @value{GDBN}
21167 @code{load} command to download the file from the host to the target.
21168 The file name and load offset should be given as arguments to the @code{load}
21170 Since the file format is aout, the program must be loaded to the starting
21171 address. You can use @code{objdump} to find out what this value is. The load
21172 offset is an offset which is added to the VMA (virtual memory address)
21173 of each of the file's sections.
21174 For instance, if the program
21175 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
21176 and bss at 0x12010170, in @value{GDBN}, type:
21179 (gdbslet) load prog 0x12010000
21180 Loading section .text, size 0xdb0 vma 0x12010000
21183 If the code is loaded at a different address then what the program was linked
21184 to, you may need to use the @code{section} and @code{add-symbol-file} commands
21185 to tell @value{GDBN} where to map the symbol table.
21187 @node Sparclet Execution
21188 @subsubsection Running and Debugging
21190 @cindex running and debugging Sparclet programs
21191 You can now begin debugging the task using @value{GDBN}'s execution control
21192 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
21193 manual for the list of commands.
21197 Breakpoint 1 at 0x12010000: file prog.c, line 3.
21199 Starting program: prog
21200 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
21201 3 char *symarg = 0;
21203 4 char *execarg = "hello!";
21208 @subsection Fujitsu Sparclite
21212 @kindex target sparclite
21213 @item target sparclite @var{dev}
21214 Fujitsu sparclite boards, used only for the purpose of loading.
21215 You must use an additional command to debug the program.
21216 For example: target remote @var{dev} using @value{GDBN} standard
21222 @subsection Zilog Z8000
21225 @cindex simulator, Z8000
21226 @cindex Zilog Z8000 simulator
21228 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
21231 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
21232 unsegmented variant of the Z8000 architecture) or the Z8001 (the
21233 segmented variant). The simulator recognizes which architecture is
21234 appropriate by inspecting the object code.
21237 @item target sim @var{args}
21239 @kindex target sim@r{, with Z8000}
21240 Debug programs on a simulated CPU. If the simulator supports setup
21241 options, specify them via @var{args}.
21245 After specifying this target, you can debug programs for the simulated
21246 CPU in the same style as programs for your host computer; use the
21247 @code{file} command to load a new program image, the @code{run} command
21248 to run your program, and so on.
21250 As well as making available all the usual machine registers
21251 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
21252 additional items of information as specially named registers:
21257 Counts clock-ticks in the simulator.
21260 Counts instructions run in the simulator.
21263 Execution time in 60ths of a second.
21267 You can refer to these values in @value{GDBN} expressions with the usual
21268 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
21269 conditional breakpoint that suspends only after at least 5000
21270 simulated clock ticks.
21273 @subsection Atmel AVR
21276 When configured for debugging the Atmel AVR, @value{GDBN} supports the
21277 following AVR-specific commands:
21280 @item info io_registers
21281 @kindex info io_registers@r{, AVR}
21282 @cindex I/O registers (Atmel AVR)
21283 This command displays information about the AVR I/O registers. For
21284 each register, @value{GDBN} prints its number and value.
21291 When configured for debugging CRIS, @value{GDBN} provides the
21292 following CRIS-specific commands:
21295 @item set cris-version @var{ver}
21296 @cindex CRIS version
21297 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
21298 The CRIS version affects register names and sizes. This command is useful in
21299 case autodetection of the CRIS version fails.
21301 @item show cris-version
21302 Show the current CRIS version.
21304 @item set cris-dwarf2-cfi
21305 @cindex DWARF-2 CFI and CRIS
21306 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
21307 Change to @samp{off} when using @code{gcc-cris} whose version is below
21310 @item show cris-dwarf2-cfi
21311 Show the current state of using DWARF-2 CFI.
21313 @item set cris-mode @var{mode}
21315 Set the current CRIS mode to @var{mode}. It should only be changed when
21316 debugging in guru mode, in which case it should be set to
21317 @samp{guru} (the default is @samp{normal}).
21319 @item show cris-mode
21320 Show the current CRIS mode.
21324 @subsection Renesas Super-H
21327 For the Renesas Super-H processor, @value{GDBN} provides these
21331 @item set sh calling-convention @var{convention}
21332 @kindex set sh calling-convention
21333 Set the calling-convention used when calling functions from @value{GDBN}.
21334 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
21335 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
21336 convention. If the DWARF-2 information of the called function specifies
21337 that the function follows the Renesas calling convention, the function
21338 is called using the Renesas calling convention. If the calling convention
21339 is set to @samp{renesas}, the Renesas calling convention is always used,
21340 regardless of the DWARF-2 information. This can be used to override the
21341 default of @samp{gcc} if debug information is missing, or the compiler
21342 does not emit the DWARF-2 calling convention entry for a function.
21344 @item show sh calling-convention
21345 @kindex show sh calling-convention
21346 Show the current calling convention setting.
21351 @node Architectures
21352 @section Architectures
21354 This section describes characteristics of architectures that affect
21355 all uses of @value{GDBN} with the architecture, both native and cross.
21362 * HPPA:: HP PA architecture
21363 * SPU:: Cell Broadband Engine SPU architecture
21369 @subsection AArch64
21370 @cindex AArch64 support
21372 When @value{GDBN} is debugging the AArch64 architecture, it provides the
21373 following special commands:
21376 @item set debug aarch64
21377 @kindex set debug aarch64
21378 This command determines whether AArch64 architecture-specific debugging
21379 messages are to be displayed.
21381 @item show debug aarch64
21382 Show whether AArch64 debugging messages are displayed.
21387 @subsection x86 Architecture-specific Issues
21390 @item set struct-convention @var{mode}
21391 @kindex set struct-convention
21392 @cindex struct return convention
21393 @cindex struct/union returned in registers
21394 Set the convention used by the inferior to return @code{struct}s and
21395 @code{union}s from functions to @var{mode}. Possible values of
21396 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
21397 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
21398 are returned on the stack, while @code{"reg"} means that a
21399 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
21400 be returned in a register.
21402 @item show struct-convention
21403 @kindex show struct-convention
21404 Show the current setting of the convention to return @code{struct}s
21408 @subsubsection Intel(R) @dfn{Memory Protection Extensions} (MPX).
21409 @cindex Intel(R) Memory Protection Extensions (MPX).
21411 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
21412 @footnote{The register named with capital letters represent the architecture
21413 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
21414 which are the lower bound and upper bound. Bounds are effective addresses or
21415 memory locations. The upper bounds are architecturally represented in 1's
21416 complement form. A bound having lower bound = 0, and upper bound = 0
21417 (1's complement of all bits set) will allow access to the entire address space.
21419 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
21420 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
21421 display the upper bound performing the complement of one operation on the
21422 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
21423 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
21424 can also be noted that the upper bounds are inclusive.
21426 As an example, assume that the register BND0 holds bounds for a pointer having
21427 access allowed for the range between 0x32 and 0x71. The values present on
21428 bnd0raw and bnd registers are presented as follows:
21431 bnd0raw = @{0x32, 0xffffffff8e@}
21432 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
21435 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
21436 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
21437 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
21438 Python, the display includes the memory size, in bits, accessible to
21444 See the following section.
21447 @subsection @acronym{MIPS}
21449 @cindex stack on Alpha
21450 @cindex stack on @acronym{MIPS}
21451 @cindex Alpha stack
21452 @cindex @acronym{MIPS} stack
21453 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
21454 sometimes requires @value{GDBN} to search backward in the object code to
21455 find the beginning of a function.
21457 @cindex response time, @acronym{MIPS} debugging
21458 To improve response time (especially for embedded applications, where
21459 @value{GDBN} may be restricted to a slow serial line for this search)
21460 you may want to limit the size of this search, using one of these
21464 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
21465 @item set heuristic-fence-post @var{limit}
21466 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
21467 search for the beginning of a function. A value of @var{0} (the
21468 default) means there is no limit. However, except for @var{0}, the
21469 larger the limit the more bytes @code{heuristic-fence-post} must search
21470 and therefore the longer it takes to run. You should only need to use
21471 this command when debugging a stripped executable.
21473 @item show heuristic-fence-post
21474 Display the current limit.
21478 These commands are available @emph{only} when @value{GDBN} is configured
21479 for debugging programs on Alpha or @acronym{MIPS} processors.
21481 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
21485 @item set mips abi @var{arg}
21486 @kindex set mips abi
21487 @cindex set ABI for @acronym{MIPS}
21488 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
21489 values of @var{arg} are:
21493 The default ABI associated with the current binary (this is the
21503 @item show mips abi
21504 @kindex show mips abi
21505 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
21507 @item set mips compression @var{arg}
21508 @kindex set mips compression
21509 @cindex code compression, @acronym{MIPS}
21510 Tell @value{GDBN} which @acronym{MIPS} compressed
21511 @acronym{ISA, Instruction Set Architecture} encoding is used by the
21512 inferior. @value{GDBN} uses this for code disassembly and other
21513 internal interpretation purposes. This setting is only referred to
21514 when no executable has been associated with the debugging session or
21515 the executable does not provide information about the encoding it uses.
21516 Otherwise this setting is automatically updated from information
21517 provided by the executable.
21519 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
21520 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
21521 executables containing @acronym{MIPS16} code frequently are not
21522 identified as such.
21524 This setting is ``sticky''; that is, it retains its value across
21525 debugging sessions until reset either explicitly with this command or
21526 implicitly from an executable.
21528 The compiler and/or assembler typically add symbol table annotations to
21529 identify functions compiled for the @acronym{MIPS16} or
21530 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
21531 are present, @value{GDBN} uses them in preference to the global
21532 compressed @acronym{ISA} encoding setting.
21534 @item show mips compression
21535 @kindex show mips compression
21536 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
21537 @value{GDBN} to debug the inferior.
21540 @itemx show mipsfpu
21541 @xref{MIPS Embedded, set mipsfpu}.
21543 @item set mips mask-address @var{arg}
21544 @kindex set mips mask-address
21545 @cindex @acronym{MIPS} addresses, masking
21546 This command determines whether the most-significant 32 bits of 64-bit
21547 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
21548 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
21549 setting, which lets @value{GDBN} determine the correct value.
21551 @item show mips mask-address
21552 @kindex show mips mask-address
21553 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
21556 @item set remote-mips64-transfers-32bit-regs
21557 @kindex set remote-mips64-transfers-32bit-regs
21558 This command controls compatibility with 64-bit @acronym{MIPS} targets that
21559 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
21560 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
21561 and 64 bits for other registers, set this option to @samp{on}.
21563 @item show remote-mips64-transfers-32bit-regs
21564 @kindex show remote-mips64-transfers-32bit-regs
21565 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
21567 @item set debug mips
21568 @kindex set debug mips
21569 This command turns on and off debugging messages for the @acronym{MIPS}-specific
21570 target code in @value{GDBN}.
21572 @item show debug mips
21573 @kindex show debug mips
21574 Show the current setting of @acronym{MIPS} debugging messages.
21580 @cindex HPPA support
21582 When @value{GDBN} is debugging the HP PA architecture, it provides the
21583 following special commands:
21586 @item set debug hppa
21587 @kindex set debug hppa
21588 This command determines whether HPPA architecture-specific debugging
21589 messages are to be displayed.
21591 @item show debug hppa
21592 Show whether HPPA debugging messages are displayed.
21594 @item maint print unwind @var{address}
21595 @kindex maint print unwind@r{, HPPA}
21596 This command displays the contents of the unwind table entry at the
21597 given @var{address}.
21603 @subsection Cell Broadband Engine SPU architecture
21604 @cindex Cell Broadband Engine
21607 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
21608 it provides the following special commands:
21611 @item info spu event
21613 Display SPU event facility status. Shows current event mask
21614 and pending event status.
21616 @item info spu signal
21617 Display SPU signal notification facility status. Shows pending
21618 signal-control word and signal notification mode of both signal
21619 notification channels.
21621 @item info spu mailbox
21622 Display SPU mailbox facility status. Shows all pending entries,
21623 in order of processing, in each of the SPU Write Outbound,
21624 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
21627 Display MFC DMA status. Shows all pending commands in the MFC
21628 DMA queue. For each entry, opcode, tag, class IDs, effective
21629 and local store addresses and transfer size are shown.
21631 @item info spu proxydma
21632 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
21633 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
21634 and local store addresses and transfer size are shown.
21638 When @value{GDBN} is debugging a combined PowerPC/SPU application
21639 on the Cell Broadband Engine, it provides in addition the following
21643 @item set spu stop-on-load @var{arg}
21645 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
21646 will give control to the user when a new SPE thread enters its @code{main}
21647 function. The default is @code{off}.
21649 @item show spu stop-on-load
21651 Show whether to stop for new SPE threads.
21653 @item set spu auto-flush-cache @var{arg}
21654 Set whether to automatically flush the software-managed cache. When set to
21655 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
21656 cache to be flushed whenever SPE execution stops. This provides a consistent
21657 view of PowerPC memory that is accessed via the cache. If an application
21658 does not use the software-managed cache, this option has no effect.
21660 @item show spu auto-flush-cache
21661 Show whether to automatically flush the software-managed cache.
21666 @subsection PowerPC
21667 @cindex PowerPC architecture
21669 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
21670 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
21671 numbers stored in the floating point registers. These values must be stored
21672 in two consecutive registers, always starting at an even register like
21673 @code{f0} or @code{f2}.
21675 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
21676 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
21677 @code{f2} and @code{f3} for @code{$dl1} and so on.
21679 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
21680 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
21683 @subsection Nios II
21684 @cindex Nios II architecture
21686 When @value{GDBN} is debugging the Nios II architecture,
21687 it provides the following special commands:
21691 @item set debug nios2
21692 @kindex set debug nios2
21693 This command turns on and off debugging messages for the Nios II
21694 target code in @value{GDBN}.
21696 @item show debug nios2
21697 @kindex show debug nios2
21698 Show the current setting of Nios II debugging messages.
21701 @node Controlling GDB
21702 @chapter Controlling @value{GDBN}
21704 You can alter the way @value{GDBN} interacts with you by using the
21705 @code{set} command. For commands controlling how @value{GDBN} displays
21706 data, see @ref{Print Settings, ,Print Settings}. Other settings are
21711 * Editing:: Command editing
21712 * Command History:: Command history
21713 * Screen Size:: Screen size
21714 * Numbers:: Numbers
21715 * ABI:: Configuring the current ABI
21716 * Auto-loading:: Automatically loading associated files
21717 * Messages/Warnings:: Optional warnings and messages
21718 * Debugging Output:: Optional messages about internal happenings
21719 * Other Misc Settings:: Other Miscellaneous Settings
21727 @value{GDBN} indicates its readiness to read a command by printing a string
21728 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
21729 can change the prompt string with the @code{set prompt} command. For
21730 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
21731 the prompt in one of the @value{GDBN} sessions so that you can always tell
21732 which one you are talking to.
21734 @emph{Note:} @code{set prompt} does not add a space for you after the
21735 prompt you set. This allows you to set a prompt which ends in a space
21736 or a prompt that does not.
21740 @item set prompt @var{newprompt}
21741 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
21743 @kindex show prompt
21745 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
21748 Versions of @value{GDBN} that ship with Python scripting enabled have
21749 prompt extensions. The commands for interacting with these extensions
21753 @kindex set extended-prompt
21754 @item set extended-prompt @var{prompt}
21755 Set an extended prompt that allows for substitutions.
21756 @xref{gdb.prompt}, for a list of escape sequences that can be used for
21757 substitution. Any escape sequences specified as part of the prompt
21758 string are replaced with the corresponding strings each time the prompt
21764 set extended-prompt Current working directory: \w (gdb)
21767 Note that when an extended-prompt is set, it takes control of the
21768 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
21770 @kindex show extended-prompt
21771 @item show extended-prompt
21772 Prints the extended prompt. Any escape sequences specified as part of
21773 the prompt string with @code{set extended-prompt}, are replaced with the
21774 corresponding strings each time the prompt is displayed.
21778 @section Command Editing
21780 @cindex command line editing
21782 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
21783 @sc{gnu} library provides consistent behavior for programs which provide a
21784 command line interface to the user. Advantages are @sc{gnu} Emacs-style
21785 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
21786 substitution, and a storage and recall of command history across
21787 debugging sessions.
21789 You may control the behavior of command line editing in @value{GDBN} with the
21790 command @code{set}.
21793 @kindex set editing
21796 @itemx set editing on
21797 Enable command line editing (enabled by default).
21799 @item set editing off
21800 Disable command line editing.
21802 @kindex show editing
21804 Show whether command line editing is enabled.
21807 @ifset SYSTEM_READLINE
21808 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
21810 @ifclear SYSTEM_READLINE
21811 @xref{Command Line Editing},
21813 for more details about the Readline
21814 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
21815 encouraged to read that chapter.
21817 @node Command History
21818 @section Command History
21819 @cindex command history
21821 @value{GDBN} can keep track of the commands you type during your
21822 debugging sessions, so that you can be certain of precisely what
21823 happened. Use these commands to manage the @value{GDBN} command
21826 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
21827 package, to provide the history facility.
21828 @ifset SYSTEM_READLINE
21829 @xref{Using History Interactively, , , history, GNU History Library},
21831 @ifclear SYSTEM_READLINE
21832 @xref{Using History Interactively},
21834 for the detailed description of the History library.
21836 To issue a command to @value{GDBN} without affecting certain aspects of
21837 the state which is seen by users, prefix it with @samp{server }
21838 (@pxref{Server Prefix}). This
21839 means that this command will not affect the command history, nor will it
21840 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
21841 pressed on a line by itself.
21843 @cindex @code{server}, command prefix
21844 The server prefix does not affect the recording of values into the value
21845 history; to print a value without recording it into the value history,
21846 use the @code{output} command instead of the @code{print} command.
21848 Here is the description of @value{GDBN} commands related to command
21852 @cindex history substitution
21853 @cindex history file
21854 @kindex set history filename
21855 @cindex @env{GDBHISTFILE}, environment variable
21856 @item set history filename @var{fname}
21857 Set the name of the @value{GDBN} command history file to @var{fname}.
21858 This is the file where @value{GDBN} reads an initial command history
21859 list, and where it writes the command history from this session when it
21860 exits. You can access this list through history expansion or through
21861 the history command editing characters listed below. This file defaults
21862 to the value of the environment variable @code{GDBHISTFILE}, or to
21863 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
21866 @cindex save command history
21867 @kindex set history save
21868 @item set history save
21869 @itemx set history save on
21870 Record command history in a file, whose name may be specified with the
21871 @code{set history filename} command. By default, this option is disabled.
21873 @item set history save off
21874 Stop recording command history in a file.
21876 @cindex history size
21877 @kindex set history size
21878 @cindex @env{HISTSIZE}, environment variable
21879 @item set history size @var{size}
21880 @itemx set history size unlimited
21881 Set the number of commands which @value{GDBN} keeps in its history list.
21882 This defaults to the value of the environment variable
21883 @code{HISTSIZE}, or to 256 if this variable is not set. If @var{size}
21884 is @code{unlimited}, the number of commands @value{GDBN} keeps in the
21885 history list is unlimited.
21888 History expansion assigns special meaning to the character @kbd{!}.
21889 @ifset SYSTEM_READLINE
21890 @xref{Event Designators, , , history, GNU History Library},
21892 @ifclear SYSTEM_READLINE
21893 @xref{Event Designators},
21897 @cindex history expansion, turn on/off
21898 Since @kbd{!} is also the logical not operator in C, history expansion
21899 is off by default. If you decide to enable history expansion with the
21900 @code{set history expansion on} command, you may sometimes need to
21901 follow @kbd{!} (when it is used as logical not, in an expression) with
21902 a space or a tab to prevent it from being expanded. The readline
21903 history facilities do not attempt substitution on the strings
21904 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
21906 The commands to control history expansion are:
21909 @item set history expansion on
21910 @itemx set history expansion
21911 @kindex set history expansion
21912 Enable history expansion. History expansion is off by default.
21914 @item set history expansion off
21915 Disable history expansion.
21918 @kindex show history
21920 @itemx show history filename
21921 @itemx show history save
21922 @itemx show history size
21923 @itemx show history expansion
21924 These commands display the state of the @value{GDBN} history parameters.
21925 @code{show history} by itself displays all four states.
21930 @kindex show commands
21931 @cindex show last commands
21932 @cindex display command history
21933 @item show commands
21934 Display the last ten commands in the command history.
21936 @item show commands @var{n}
21937 Print ten commands centered on command number @var{n}.
21939 @item show commands +
21940 Print ten commands just after the commands last printed.
21944 @section Screen Size
21945 @cindex size of screen
21946 @cindex pauses in output
21948 Certain commands to @value{GDBN} may produce large amounts of
21949 information output to the screen. To help you read all of it,
21950 @value{GDBN} pauses and asks you for input at the end of each page of
21951 output. Type @key{RET} when you want to continue the output, or @kbd{q}
21952 to discard the remaining output. Also, the screen width setting
21953 determines when to wrap lines of output. Depending on what is being
21954 printed, @value{GDBN} tries to break the line at a readable place,
21955 rather than simply letting it overflow onto the following line.
21957 Normally @value{GDBN} knows the size of the screen from the terminal
21958 driver software. For example, on Unix @value{GDBN} uses the termcap data base
21959 together with the value of the @code{TERM} environment variable and the
21960 @code{stty rows} and @code{stty cols} settings. If this is not correct,
21961 you can override it with the @code{set height} and @code{set
21968 @kindex show height
21969 @item set height @var{lpp}
21970 @itemx set height unlimited
21972 @itemx set width @var{cpl}
21973 @itemx set width unlimited
21975 These @code{set} commands specify a screen height of @var{lpp} lines and
21976 a screen width of @var{cpl} characters. The associated @code{show}
21977 commands display the current settings.
21979 If you specify a height of either @code{unlimited} or zero lines,
21980 @value{GDBN} does not pause during output no matter how long the
21981 output is. This is useful if output is to a file or to an editor
21984 Likewise, you can specify @samp{set width unlimited} or @samp{set
21985 width 0} to prevent @value{GDBN} from wrapping its output.
21987 @item set pagination on
21988 @itemx set pagination off
21989 @kindex set pagination
21990 Turn the output pagination on or off; the default is on. Turning
21991 pagination off is the alternative to @code{set height unlimited}. Note that
21992 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
21993 Options, -batch}) also automatically disables pagination.
21995 @item show pagination
21996 @kindex show pagination
21997 Show the current pagination mode.
22002 @cindex number representation
22003 @cindex entering numbers
22005 You can always enter numbers in octal, decimal, or hexadecimal in
22006 @value{GDBN} by the usual conventions: octal numbers begin with
22007 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
22008 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
22009 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
22010 10; likewise, the default display for numbers---when no particular
22011 format is specified---is base 10. You can change the default base for
22012 both input and output with the commands described below.
22015 @kindex set input-radix
22016 @item set input-radix @var{base}
22017 Set the default base for numeric input. Supported choices
22018 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
22019 specified either unambiguously or using the current input radix; for
22023 set input-radix 012
22024 set input-radix 10.
22025 set input-radix 0xa
22029 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
22030 leaves the input radix unchanged, no matter what it was, since
22031 @samp{10}, being without any leading or trailing signs of its base, is
22032 interpreted in the current radix. Thus, if the current radix is 16,
22033 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
22036 @kindex set output-radix
22037 @item set output-radix @var{base}
22038 Set the default base for numeric display. Supported choices
22039 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
22040 specified either unambiguously or using the current input radix.
22042 @kindex show input-radix
22043 @item show input-radix
22044 Display the current default base for numeric input.
22046 @kindex show output-radix
22047 @item show output-radix
22048 Display the current default base for numeric display.
22050 @item set radix @r{[}@var{base}@r{]}
22054 These commands set and show the default base for both input and output
22055 of numbers. @code{set radix} sets the radix of input and output to
22056 the same base; without an argument, it resets the radix back to its
22057 default value of 10.
22062 @section Configuring the Current ABI
22064 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
22065 application automatically. However, sometimes you need to override its
22066 conclusions. Use these commands to manage @value{GDBN}'s view of the
22072 @cindex Newlib OS ABI and its influence on the longjmp handling
22074 One @value{GDBN} configuration can debug binaries for multiple operating
22075 system targets, either via remote debugging or native emulation.
22076 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
22077 but you can override its conclusion using the @code{set osabi} command.
22078 One example where this is useful is in debugging of binaries which use
22079 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
22080 not have the same identifying marks that the standard C library for your
22083 When @value{GDBN} is debugging the AArch64 architecture, it provides a
22084 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
22085 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
22086 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
22090 Show the OS ABI currently in use.
22093 With no argument, show the list of registered available OS ABI's.
22095 @item set osabi @var{abi}
22096 Set the current OS ABI to @var{abi}.
22099 @cindex float promotion
22101 Generally, the way that an argument of type @code{float} is passed to a
22102 function depends on whether the function is prototyped. For a prototyped
22103 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
22104 according to the architecture's convention for @code{float}. For unprototyped
22105 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
22106 @code{double} and then passed.
22108 Unfortunately, some forms of debug information do not reliably indicate whether
22109 a function is prototyped. If @value{GDBN} calls a function that is not marked
22110 as prototyped, it consults @kbd{set coerce-float-to-double}.
22113 @kindex set coerce-float-to-double
22114 @item set coerce-float-to-double
22115 @itemx set coerce-float-to-double on
22116 Arguments of type @code{float} will be promoted to @code{double} when passed
22117 to an unprototyped function. This is the default setting.
22119 @item set coerce-float-to-double off
22120 Arguments of type @code{float} will be passed directly to unprototyped
22123 @kindex show coerce-float-to-double
22124 @item show coerce-float-to-double
22125 Show the current setting of promoting @code{float} to @code{double}.
22129 @kindex show cp-abi
22130 @value{GDBN} needs to know the ABI used for your program's C@t{++}
22131 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
22132 used to build your application. @value{GDBN} only fully supports
22133 programs with a single C@t{++} ABI; if your program contains code using
22134 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
22135 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
22136 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
22137 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
22138 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
22139 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
22144 Show the C@t{++} ABI currently in use.
22147 With no argument, show the list of supported C@t{++} ABI's.
22149 @item set cp-abi @var{abi}
22150 @itemx set cp-abi auto
22151 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
22155 @section Automatically loading associated files
22156 @cindex auto-loading
22158 @value{GDBN} sometimes reads files with commands and settings automatically,
22159 without being explicitly told so by the user. We call this feature
22160 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
22161 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
22162 results or introduce security risks (e.g., if the file comes from untrusted
22166 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
22167 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
22169 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
22170 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
22173 There are various kinds of files @value{GDBN} can automatically load.
22174 In addition to these files, @value{GDBN} supports auto-loading code written
22175 in various extension languages. @xref{Auto-loading extensions}.
22177 Note that loading of these associated files (including the local @file{.gdbinit}
22178 file) requires accordingly configured @code{auto-load safe-path}
22179 (@pxref{Auto-loading safe path}).
22181 For these reasons, @value{GDBN} includes commands and options to let you
22182 control when to auto-load files and which files should be auto-loaded.
22185 @anchor{set auto-load off}
22186 @kindex set auto-load off
22187 @item set auto-load off
22188 Globally disable loading of all auto-loaded files.
22189 You may want to use this command with the @samp{-iex} option
22190 (@pxref{Option -init-eval-command}) such as:
22192 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
22195 Be aware that system init file (@pxref{System-wide configuration})
22196 and init files from your home directory (@pxref{Home Directory Init File})
22197 still get read (as they come from generally trusted directories).
22198 To prevent @value{GDBN} from auto-loading even those init files, use the
22199 @option{-nx} option (@pxref{Mode Options}), in addition to
22200 @code{set auto-load no}.
22202 @anchor{show auto-load}
22203 @kindex show auto-load
22204 @item show auto-load
22205 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
22209 (gdb) show auto-load
22210 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
22211 libthread-db: Auto-loading of inferior specific libthread_db is on.
22212 local-gdbinit: Auto-loading of .gdbinit script from current directory
22214 python-scripts: Auto-loading of Python scripts is on.
22215 safe-path: List of directories from which it is safe to auto-load files
22216 is $debugdir:$datadir/auto-load.
22217 scripts-directory: List of directories from which to load auto-loaded scripts
22218 is $debugdir:$datadir/auto-load.
22221 @anchor{info auto-load}
22222 @kindex info auto-load
22223 @item info auto-load
22224 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
22228 (gdb) info auto-load
22231 Yes /home/user/gdb/gdb-gdb.gdb
22232 libthread-db: No auto-loaded libthread-db.
22233 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
22237 Yes /home/user/gdb/gdb-gdb.py
22241 These are @value{GDBN} control commands for the auto-loading:
22243 @multitable @columnfractions .5 .5
22244 @item @xref{set auto-load off}.
22245 @tab Disable auto-loading globally.
22246 @item @xref{show auto-load}.
22247 @tab Show setting of all kinds of files.
22248 @item @xref{info auto-load}.
22249 @tab Show state of all kinds of files.
22250 @item @xref{set auto-load gdb-scripts}.
22251 @tab Control for @value{GDBN} command scripts.
22252 @item @xref{show auto-load gdb-scripts}.
22253 @tab Show setting of @value{GDBN} command scripts.
22254 @item @xref{info auto-load gdb-scripts}.
22255 @tab Show state of @value{GDBN} command scripts.
22256 @item @xref{set auto-load python-scripts}.
22257 @tab Control for @value{GDBN} Python scripts.
22258 @item @xref{show auto-load python-scripts}.
22259 @tab Show setting of @value{GDBN} Python scripts.
22260 @item @xref{info auto-load python-scripts}.
22261 @tab Show state of @value{GDBN} Python scripts.
22262 @item @xref{set auto-load scripts-directory}.
22263 @tab Control for @value{GDBN} auto-loaded scripts location.
22264 @item @xref{show auto-load scripts-directory}.
22265 @tab Show @value{GDBN} auto-loaded scripts location.
22266 @item @xref{set auto-load local-gdbinit}.
22267 @tab Control for init file in the current directory.
22268 @item @xref{show auto-load local-gdbinit}.
22269 @tab Show setting of init file in the current directory.
22270 @item @xref{info auto-load local-gdbinit}.
22271 @tab Show state of init file in the current directory.
22272 @item @xref{set auto-load libthread-db}.
22273 @tab Control for thread debugging library.
22274 @item @xref{show auto-load libthread-db}.
22275 @tab Show setting of thread debugging library.
22276 @item @xref{info auto-load libthread-db}.
22277 @tab Show state of thread debugging library.
22278 @item @xref{set auto-load safe-path}.
22279 @tab Control directories trusted for automatic loading.
22280 @item @xref{show auto-load safe-path}.
22281 @tab Show directories trusted for automatic loading.
22282 @item @xref{add-auto-load-safe-path}.
22283 @tab Add directory trusted for automatic loading.
22286 @node Init File in the Current Directory
22287 @subsection Automatically loading init file in the current directory
22288 @cindex auto-loading init file in the current directory
22290 By default, @value{GDBN} reads and executes the canned sequences of commands
22291 from init file (if any) in the current working directory,
22292 see @ref{Init File in the Current Directory during Startup}.
22294 Note that loading of this local @file{.gdbinit} file also requires accordingly
22295 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22298 @anchor{set auto-load local-gdbinit}
22299 @kindex set auto-load local-gdbinit
22300 @item set auto-load local-gdbinit [on|off]
22301 Enable or disable the auto-loading of canned sequences of commands
22302 (@pxref{Sequences}) found in init file in the current directory.
22304 @anchor{show auto-load local-gdbinit}
22305 @kindex show auto-load local-gdbinit
22306 @item show auto-load local-gdbinit
22307 Show whether auto-loading of canned sequences of commands from init file in the
22308 current directory is enabled or disabled.
22310 @anchor{info auto-load local-gdbinit}
22311 @kindex info auto-load local-gdbinit
22312 @item info auto-load local-gdbinit
22313 Print whether canned sequences of commands from init file in the
22314 current directory have been auto-loaded.
22317 @node libthread_db.so.1 file
22318 @subsection Automatically loading thread debugging library
22319 @cindex auto-loading libthread_db.so.1
22321 This feature is currently present only on @sc{gnu}/Linux native hosts.
22323 @value{GDBN} reads in some cases thread debugging library from places specific
22324 to the inferior (@pxref{set libthread-db-search-path}).
22326 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
22327 without checking this @samp{set auto-load libthread-db} switch as system
22328 libraries have to be trusted in general. In all other cases of
22329 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
22330 auto-load libthread-db} is enabled before trying to open such thread debugging
22333 Note that loading of this debugging library also requires accordingly configured
22334 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22337 @anchor{set auto-load libthread-db}
22338 @kindex set auto-load libthread-db
22339 @item set auto-load libthread-db [on|off]
22340 Enable or disable the auto-loading of inferior specific thread debugging library.
22342 @anchor{show auto-load libthread-db}
22343 @kindex show auto-load libthread-db
22344 @item show auto-load libthread-db
22345 Show whether auto-loading of inferior specific thread debugging library is
22346 enabled or disabled.
22348 @anchor{info auto-load libthread-db}
22349 @kindex info auto-load libthread-db
22350 @item info auto-load libthread-db
22351 Print the list of all loaded inferior specific thread debugging libraries and
22352 for each such library print list of inferior @var{pid}s using it.
22355 @node Auto-loading safe path
22356 @subsection Security restriction for auto-loading
22357 @cindex auto-loading safe-path
22359 As the files of inferior can come from untrusted source (such as submitted by
22360 an application user) @value{GDBN} does not always load any files automatically.
22361 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
22362 directories trusted for loading files not explicitly requested by user.
22363 Each directory can also be a shell wildcard pattern.
22365 If the path is not set properly you will see a warning and the file will not
22370 Reading symbols from /home/user/gdb/gdb...done.
22371 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
22372 declined by your `auto-load safe-path' set
22373 to "$debugdir:$datadir/auto-load".
22374 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
22375 declined by your `auto-load safe-path' set
22376 to "$debugdir:$datadir/auto-load".
22380 To instruct @value{GDBN} to go ahead and use the init files anyway,
22381 invoke @value{GDBN} like this:
22384 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
22387 The list of trusted directories is controlled by the following commands:
22390 @anchor{set auto-load safe-path}
22391 @kindex set auto-load safe-path
22392 @item set auto-load safe-path @r{[}@var{directories}@r{]}
22393 Set the list of directories (and their subdirectories) trusted for automatic
22394 loading and execution of scripts. You can also enter a specific trusted file.
22395 Each directory can also be a shell wildcard pattern; wildcards do not match
22396 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
22397 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
22398 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
22399 its default value as specified during @value{GDBN} compilation.
22401 The list of directories uses path separator (@samp{:} on GNU and Unix
22402 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
22403 to the @env{PATH} environment variable.
22405 @anchor{show auto-load safe-path}
22406 @kindex show auto-load safe-path
22407 @item show auto-load safe-path
22408 Show the list of directories trusted for automatic loading and execution of
22411 @anchor{add-auto-load-safe-path}
22412 @kindex add-auto-load-safe-path
22413 @item add-auto-load-safe-path
22414 Add an entry (or list of entries) the list of directories trusted for automatic
22415 loading and execution of scripts. Multiple entries may be delimited by the
22416 host platform path separator in use.
22419 This variable defaults to what @code{--with-auto-load-dir} has been configured
22420 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
22421 substitution applies the same as for @ref{set auto-load scripts-directory}.
22422 The default @code{set auto-load safe-path} value can be also overriden by
22423 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
22425 Setting this variable to @file{/} disables this security protection,
22426 corresponding @value{GDBN} configuration option is
22427 @option{--without-auto-load-safe-path}.
22428 This variable is supposed to be set to the system directories writable by the
22429 system superuser only. Users can add their source directories in init files in
22430 their home directories (@pxref{Home Directory Init File}). See also deprecated
22431 init file in the current directory
22432 (@pxref{Init File in the Current Directory during Startup}).
22434 To force @value{GDBN} to load the files it declined to load in the previous
22435 example, you could use one of the following ways:
22438 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
22439 Specify this trusted directory (or a file) as additional component of the list.
22440 You have to specify also any existing directories displayed by
22441 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
22443 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
22444 Specify this directory as in the previous case but just for a single
22445 @value{GDBN} session.
22447 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
22448 Disable auto-loading safety for a single @value{GDBN} session.
22449 This assumes all the files you debug during this @value{GDBN} session will come
22450 from trusted sources.
22452 @item @kbd{./configure --without-auto-load-safe-path}
22453 During compilation of @value{GDBN} you may disable any auto-loading safety.
22454 This assumes all the files you will ever debug with this @value{GDBN} come from
22458 On the other hand you can also explicitly forbid automatic files loading which
22459 also suppresses any such warning messages:
22462 @item @kbd{gdb -iex "set auto-load no" @dots{}}
22463 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
22465 @item @file{~/.gdbinit}: @samp{set auto-load no}
22466 Disable auto-loading globally for the user
22467 (@pxref{Home Directory Init File}). While it is improbable, you could also
22468 use system init file instead (@pxref{System-wide configuration}).
22471 This setting applies to the file names as entered by user. If no entry matches
22472 @value{GDBN} tries as a last resort to also resolve all the file names into
22473 their canonical form (typically resolving symbolic links) and compare the
22474 entries again. @value{GDBN} already canonicalizes most of the filenames on its
22475 own before starting the comparison so a canonical form of directories is
22476 recommended to be entered.
22478 @node Auto-loading verbose mode
22479 @subsection Displaying files tried for auto-load
22480 @cindex auto-loading verbose mode
22482 For better visibility of all the file locations where you can place scripts to
22483 be auto-loaded with inferior --- or to protect yourself against accidental
22484 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
22485 all the files attempted to be loaded. Both existing and non-existing files may
22488 For example the list of directories from which it is safe to auto-load files
22489 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
22490 may not be too obvious while setting it up.
22493 (gdb) set debug auto-load on
22494 (gdb) file ~/src/t/true
22495 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
22496 for objfile "/tmp/true".
22497 auto-load: Updating directories of "/usr:/opt".
22498 auto-load: Using directory "/usr".
22499 auto-load: Using directory "/opt".
22500 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
22501 by your `auto-load safe-path' set to "/usr:/opt".
22505 @anchor{set debug auto-load}
22506 @kindex set debug auto-load
22507 @item set debug auto-load [on|off]
22508 Set whether to print the filenames attempted to be auto-loaded.
22510 @anchor{show debug auto-load}
22511 @kindex show debug auto-load
22512 @item show debug auto-load
22513 Show whether printing of the filenames attempted to be auto-loaded is turned
22517 @node Messages/Warnings
22518 @section Optional Warnings and Messages
22520 @cindex verbose operation
22521 @cindex optional warnings
22522 By default, @value{GDBN} is silent about its inner workings. If you are
22523 running on a slow machine, you may want to use the @code{set verbose}
22524 command. This makes @value{GDBN} tell you when it does a lengthy
22525 internal operation, so you will not think it has crashed.
22527 Currently, the messages controlled by @code{set verbose} are those
22528 which announce that the symbol table for a source file is being read;
22529 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
22532 @kindex set verbose
22533 @item set verbose on
22534 Enables @value{GDBN} output of certain informational messages.
22536 @item set verbose off
22537 Disables @value{GDBN} output of certain informational messages.
22539 @kindex show verbose
22541 Displays whether @code{set verbose} is on or off.
22544 By default, if @value{GDBN} encounters bugs in the symbol table of an
22545 object file, it is silent; but if you are debugging a compiler, you may
22546 find this information useful (@pxref{Symbol Errors, ,Errors Reading
22551 @kindex set complaints
22552 @item set complaints @var{limit}
22553 Permits @value{GDBN} to output @var{limit} complaints about each type of
22554 unusual symbols before becoming silent about the problem. Set
22555 @var{limit} to zero to suppress all complaints; set it to a large number
22556 to prevent complaints from being suppressed.
22558 @kindex show complaints
22559 @item show complaints
22560 Displays how many symbol complaints @value{GDBN} is permitted to produce.
22564 @anchor{confirmation requests}
22565 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
22566 lot of stupid questions to confirm certain commands. For example, if
22567 you try to run a program which is already running:
22571 The program being debugged has been started already.
22572 Start it from the beginning? (y or n)
22575 If you are willing to unflinchingly face the consequences of your own
22576 commands, you can disable this ``feature'':
22580 @kindex set confirm
22582 @cindex confirmation
22583 @cindex stupid questions
22584 @item set confirm off
22585 Disables confirmation requests. Note that running @value{GDBN} with
22586 the @option{--batch} option (@pxref{Mode Options, -batch}) also
22587 automatically disables confirmation requests.
22589 @item set confirm on
22590 Enables confirmation requests (the default).
22592 @kindex show confirm
22594 Displays state of confirmation requests.
22598 @cindex command tracing
22599 If you need to debug user-defined commands or sourced files you may find it
22600 useful to enable @dfn{command tracing}. In this mode each command will be
22601 printed as it is executed, prefixed with one or more @samp{+} symbols, the
22602 quantity denoting the call depth of each command.
22605 @kindex set trace-commands
22606 @cindex command scripts, debugging
22607 @item set trace-commands on
22608 Enable command tracing.
22609 @item set trace-commands off
22610 Disable command tracing.
22611 @item show trace-commands
22612 Display the current state of command tracing.
22615 @node Debugging Output
22616 @section Optional Messages about Internal Happenings
22617 @cindex optional debugging messages
22619 @value{GDBN} has commands that enable optional debugging messages from
22620 various @value{GDBN} subsystems; normally these commands are of
22621 interest to @value{GDBN} maintainers, or when reporting a bug. This
22622 section documents those commands.
22625 @kindex set exec-done-display
22626 @item set exec-done-display
22627 Turns on or off the notification of asynchronous commands'
22628 completion. When on, @value{GDBN} will print a message when an
22629 asynchronous command finishes its execution. The default is off.
22630 @kindex show exec-done-display
22631 @item show exec-done-display
22632 Displays the current setting of asynchronous command completion
22635 @cindex ARM AArch64
22636 @item set debug aarch64
22637 Turns on or off display of debugging messages related to ARM AArch64.
22638 The default is off.
22640 @item show debug aarch64
22641 Displays the current state of displaying debugging messages related to
22643 @cindex gdbarch debugging info
22644 @cindex architecture debugging info
22645 @item set debug arch
22646 Turns on or off display of gdbarch debugging info. The default is off
22647 @item show debug arch
22648 Displays the current state of displaying gdbarch debugging info.
22649 @item set debug aix-solib
22650 @cindex AIX shared library debugging
22651 Control display of debugging messages from the AIX shared library
22652 support module. The default is off.
22653 @item show debug aix-thread
22654 Show the current state of displaying AIX shared library debugging messages.
22655 @item set debug aix-thread
22656 @cindex AIX threads
22657 Display debugging messages about inner workings of the AIX thread
22659 @item show debug aix-thread
22660 Show the current state of AIX thread debugging info display.
22661 @item set debug check-physname
22663 Check the results of the ``physname'' computation. When reading DWARF
22664 debugging information for C@t{++}, @value{GDBN} attempts to compute
22665 each entity's name. @value{GDBN} can do this computation in two
22666 different ways, depending on exactly what information is present.
22667 When enabled, this setting causes @value{GDBN} to compute the names
22668 both ways and display any discrepancies.
22669 @item show debug check-physname
22670 Show the current state of ``physname'' checking.
22671 @item set debug coff-pe-read
22672 @cindex COFF/PE exported symbols
22673 Control display of debugging messages related to reading of COFF/PE
22674 exported symbols. The default is off.
22675 @item show debug coff-pe-read
22676 Displays the current state of displaying debugging messages related to
22677 reading of COFF/PE exported symbols.
22678 @item set debug dwarf2-die
22679 @cindex DWARF2 DIEs
22680 Dump DWARF2 DIEs after they are read in.
22681 The value is the number of nesting levels to print.
22682 A value of zero turns off the display.
22683 @item show debug dwarf2-die
22684 Show the current state of DWARF2 DIE debugging.
22685 @item set debug dwarf2-read
22686 @cindex DWARF2 Reading
22687 Turns on or off display of debugging messages related to reading
22688 DWARF debug info. The default is 0 (off).
22689 A value of 1 provides basic information.
22690 A value greater than 1 provides more verbose information.
22691 @item show debug dwarf2-read
22692 Show the current state of DWARF2 reader debugging.
22693 @item set debug displaced
22694 @cindex displaced stepping debugging info
22695 Turns on or off display of @value{GDBN} debugging info for the
22696 displaced stepping support. The default is off.
22697 @item show debug displaced
22698 Displays the current state of displaying @value{GDBN} debugging info
22699 related to displaced stepping.
22700 @item set debug event
22701 @cindex event debugging info
22702 Turns on or off display of @value{GDBN} event debugging info. The
22704 @item show debug event
22705 Displays the current state of displaying @value{GDBN} event debugging
22707 @item set debug expression
22708 @cindex expression debugging info
22709 Turns on or off display of debugging info about @value{GDBN}
22710 expression parsing. The default is off.
22711 @item show debug expression
22712 Displays the current state of displaying debugging info about
22713 @value{GDBN} expression parsing.
22714 @item set debug frame
22715 @cindex frame debugging info
22716 Turns on or off display of @value{GDBN} frame debugging info. The
22718 @item show debug frame
22719 Displays the current state of displaying @value{GDBN} frame debugging
22721 @item set debug gnu-nat
22722 @cindex @sc{gnu}/Hurd debug messages
22723 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
22724 @item show debug gnu-nat
22725 Show the current state of @sc{gnu}/Hurd debugging messages.
22726 @item set debug infrun
22727 @cindex inferior debugging info
22728 Turns on or off display of @value{GDBN} debugging info for running the inferior.
22729 The default is off. @file{infrun.c} contains GDB's runtime state machine used
22730 for implementing operations such as single-stepping the inferior.
22731 @item show debug infrun
22732 Displays the current state of @value{GDBN} inferior debugging.
22733 @item set debug jit
22734 @cindex just-in-time compilation, debugging messages
22735 Turns on or off debugging messages from JIT debug support.
22736 @item show debug jit
22737 Displays the current state of @value{GDBN} JIT debugging.
22738 @item set debug lin-lwp
22739 @cindex @sc{gnu}/Linux LWP debug messages
22740 @cindex Linux lightweight processes
22741 Turns on or off debugging messages from the Linux LWP debug support.
22742 @item show debug lin-lwp
22743 Show the current state of Linux LWP debugging messages.
22744 @item set debug mach-o
22745 @cindex Mach-O symbols processing
22746 Control display of debugging messages related to Mach-O symbols
22747 processing. The default is off.
22748 @item show debug mach-o
22749 Displays the current state of displaying debugging messages related to
22750 reading of COFF/PE exported symbols.
22751 @item set debug notification
22752 @cindex remote async notification debugging info
22753 Turns on or off debugging messages about remote async notification.
22754 The default is off.
22755 @item show debug notification
22756 Displays the current state of remote async notification debugging messages.
22757 @item set debug observer
22758 @cindex observer debugging info
22759 Turns on or off display of @value{GDBN} observer debugging. This
22760 includes info such as the notification of observable events.
22761 @item show debug observer
22762 Displays the current state of observer debugging.
22763 @item set debug overload
22764 @cindex C@t{++} overload debugging info
22765 Turns on or off display of @value{GDBN} C@t{++} overload debugging
22766 info. This includes info such as ranking of functions, etc. The default
22768 @item show debug overload
22769 Displays the current state of displaying @value{GDBN} C@t{++} overload
22771 @cindex expression parser, debugging info
22772 @cindex debug expression parser
22773 @item set debug parser
22774 Turns on or off the display of expression parser debugging output.
22775 Internally, this sets the @code{yydebug} variable in the expression
22776 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
22777 details. The default is off.
22778 @item show debug parser
22779 Show the current state of expression parser debugging.
22780 @cindex packets, reporting on stdout
22781 @cindex serial connections, debugging
22782 @cindex debug remote protocol
22783 @cindex remote protocol debugging
22784 @cindex display remote packets
22785 @item set debug remote
22786 Turns on or off display of reports on all packets sent back and forth across
22787 the serial line to the remote machine. The info is printed on the
22788 @value{GDBN} standard output stream. The default is off.
22789 @item show debug remote
22790 Displays the state of display of remote packets.
22791 @item set debug serial
22792 Turns on or off display of @value{GDBN} serial debugging info. The
22794 @item show debug serial
22795 Displays the current state of displaying @value{GDBN} serial debugging
22797 @item set debug solib-frv
22798 @cindex FR-V shared-library debugging
22799 Turns on or off debugging messages for FR-V shared-library code.
22800 @item show debug solib-frv
22801 Display the current state of FR-V shared-library code debugging
22803 @item set debug symfile
22804 @cindex symbol file functions
22805 Turns on or off display of debugging messages related to symbol file functions.
22806 The default is off. @xref{Files}.
22807 @item show debug symfile
22808 Show the current state of symbol file debugging messages.
22809 @item set debug symtab-create
22810 @cindex symbol table creation
22811 Turns on or off display of debugging messages related to symbol table creation.
22812 The default is 0 (off).
22813 A value of 1 provides basic information.
22814 A value greater than 1 provides more verbose information.
22815 @item show debug symtab-create
22816 Show the current state of symbol table creation debugging.
22817 @item set debug target
22818 @cindex target debugging info
22819 Turns on or off display of @value{GDBN} target debugging info. This info
22820 includes what is going on at the target level of GDB, as it happens. The
22821 default is 0. Set it to 1 to track events, and to 2 to also track the
22822 value of large memory transfers. Changes to this flag do not take effect
22823 until the next time you connect to a target or use the @code{run} command.
22824 @item show debug target
22825 Displays the current state of displaying @value{GDBN} target debugging
22827 @item set debug timestamp
22828 @cindex timestampping debugging info
22829 Turns on or off display of timestamps with @value{GDBN} debugging info.
22830 When enabled, seconds and microseconds are displayed before each debugging
22832 @item show debug timestamp
22833 Displays the current state of displaying timestamps with @value{GDBN}
22835 @item set debugvarobj
22836 @cindex variable object debugging info
22837 Turns on or off display of @value{GDBN} variable object debugging
22838 info. The default is off.
22839 @item show debugvarobj
22840 Displays the current state of displaying @value{GDBN} variable object
22842 @item set debug xml
22843 @cindex XML parser debugging
22844 Turns on or off debugging messages for built-in XML parsers.
22845 @item show debug xml
22846 Displays the current state of XML debugging messages.
22849 @node Other Misc Settings
22850 @section Other Miscellaneous Settings
22851 @cindex miscellaneous settings
22854 @kindex set interactive-mode
22855 @item set interactive-mode
22856 If @code{on}, forces @value{GDBN} to assume that GDB was started
22857 in a terminal. In practice, this means that @value{GDBN} should wait
22858 for the user to answer queries generated by commands entered at
22859 the command prompt. If @code{off}, forces @value{GDBN} to operate
22860 in the opposite mode, and it uses the default answers to all queries.
22861 If @code{auto} (the default), @value{GDBN} tries to determine whether
22862 its standard input is a terminal, and works in interactive-mode if it
22863 is, non-interactively otherwise.
22865 In the vast majority of cases, the debugger should be able to guess
22866 correctly which mode should be used. But this setting can be useful
22867 in certain specific cases, such as running a MinGW @value{GDBN}
22868 inside a cygwin window.
22870 @kindex show interactive-mode
22871 @item show interactive-mode
22872 Displays whether the debugger is operating in interactive mode or not.
22875 @node Extending GDB
22876 @chapter Extending @value{GDBN}
22877 @cindex extending GDB
22879 @value{GDBN} provides several mechanisms for extension.
22880 @value{GDBN} also provides the ability to automatically load
22881 extensions when it reads a file for debugging. This allows the
22882 user to automatically customize @value{GDBN} for the program
22886 * Sequences:: Canned Sequences of @value{GDBN} Commands
22887 * Python:: Extending @value{GDBN} using Python
22888 * Auto-loading extensions:: Automatically loading extensions
22889 * Aliases:: Creating new spellings of existing commands
22892 To facilitate the use of extension languages, @value{GDBN} is capable
22893 of evaluating the contents of a file. When doing so, @value{GDBN}
22894 can recognize which extension language is being used by looking at
22895 the filename extension. Files with an unrecognized filename extension
22896 are always treated as a @value{GDBN} Command Files.
22897 @xref{Command Files,, Command files}.
22899 You can control how @value{GDBN} evaluates these files with the following
22903 @kindex set script-extension
22904 @kindex show script-extension
22905 @item set script-extension off
22906 All scripts are always evaluated as @value{GDBN} Command Files.
22908 @item set script-extension soft
22909 The debugger determines the scripting language based on filename
22910 extension. If this scripting language is supported, @value{GDBN}
22911 evaluates the script using that language. Otherwise, it evaluates
22912 the file as a @value{GDBN} Command File.
22914 @item set script-extension strict
22915 The debugger determines the scripting language based on filename
22916 extension, and evaluates the script using that language. If the
22917 language is not supported, then the evaluation fails.
22919 @item show script-extension
22920 Display the current value of the @code{script-extension} option.
22925 @section Canned Sequences of Commands
22927 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
22928 Command Lists}), @value{GDBN} provides two ways to store sequences of
22929 commands for execution as a unit: user-defined commands and command
22933 * Define:: How to define your own commands
22934 * Hooks:: Hooks for user-defined commands
22935 * Command Files:: How to write scripts of commands to be stored in a file
22936 * Output:: Commands for controlled output
22937 * Auto-loading sequences:: Controlling auto-loaded command files
22941 @subsection User-defined Commands
22943 @cindex user-defined command
22944 @cindex arguments, to user-defined commands
22945 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
22946 which you assign a new name as a command. This is done with the
22947 @code{define} command. User commands may accept up to 10 arguments
22948 separated by whitespace. Arguments are accessed within the user command
22949 via @code{$arg0@dots{}$arg9}. A trivial example:
22953 print $arg0 + $arg1 + $arg2
22958 To execute the command use:
22965 This defines the command @code{adder}, which prints the sum of
22966 its three arguments. Note the arguments are text substitutions, so they may
22967 reference variables, use complex expressions, or even perform inferior
22970 @cindex argument count in user-defined commands
22971 @cindex how many arguments (user-defined commands)
22972 In addition, @code{$argc} may be used to find out how many arguments have
22973 been passed. This expands to a number in the range 0@dots{}10.
22978 print $arg0 + $arg1
22981 print $arg0 + $arg1 + $arg2
22989 @item define @var{commandname}
22990 Define a command named @var{commandname}. If there is already a command
22991 by that name, you are asked to confirm that you want to redefine it.
22992 @var{commandname} may be a bare command name consisting of letters,
22993 numbers, dashes, and underscores. It may also start with any predefined
22994 prefix command. For example, @samp{define target my-target} creates
22995 a user-defined @samp{target my-target} command.
22997 The definition of the command is made up of other @value{GDBN} command lines,
22998 which are given following the @code{define} command. The end of these
22999 commands is marked by a line containing @code{end}.
23002 @kindex end@r{ (user-defined commands)}
23003 @item document @var{commandname}
23004 Document the user-defined command @var{commandname}, so that it can be
23005 accessed by @code{help}. The command @var{commandname} must already be
23006 defined. This command reads lines of documentation just as @code{define}
23007 reads the lines of the command definition, ending with @code{end}.
23008 After the @code{document} command is finished, @code{help} on command
23009 @var{commandname} displays the documentation you have written.
23011 You may use the @code{document} command again to change the
23012 documentation of a command. Redefining the command with @code{define}
23013 does not change the documentation.
23015 @kindex dont-repeat
23016 @cindex don't repeat command
23018 Used inside a user-defined command, this tells @value{GDBN} that this
23019 command should not be repeated when the user hits @key{RET}
23020 (@pxref{Command Syntax, repeat last command}).
23022 @kindex help user-defined
23023 @item help user-defined
23024 List all user-defined commands and all python commands defined in class
23025 COMAND_USER. The first line of the documentation or docstring is
23030 @itemx show user @var{commandname}
23031 Display the @value{GDBN} commands used to define @var{commandname} (but
23032 not its documentation). If no @var{commandname} is given, display the
23033 definitions for all user-defined commands.
23034 This does not work for user-defined python commands.
23036 @cindex infinite recursion in user-defined commands
23037 @kindex show max-user-call-depth
23038 @kindex set max-user-call-depth
23039 @item show max-user-call-depth
23040 @itemx set max-user-call-depth
23041 The value of @code{max-user-call-depth} controls how many recursion
23042 levels are allowed in user-defined commands before @value{GDBN} suspects an
23043 infinite recursion and aborts the command.
23044 This does not apply to user-defined python commands.
23047 In addition to the above commands, user-defined commands frequently
23048 use control flow commands, described in @ref{Command Files}.
23050 When user-defined commands are executed, the
23051 commands of the definition are not printed. An error in any command
23052 stops execution of the user-defined command.
23054 If used interactively, commands that would ask for confirmation proceed
23055 without asking when used inside a user-defined command. Many @value{GDBN}
23056 commands that normally print messages to say what they are doing omit the
23057 messages when used in a user-defined command.
23060 @subsection User-defined Command Hooks
23061 @cindex command hooks
23062 @cindex hooks, for commands
23063 @cindex hooks, pre-command
23066 You may define @dfn{hooks}, which are a special kind of user-defined
23067 command. Whenever you run the command @samp{foo}, if the user-defined
23068 command @samp{hook-foo} exists, it is executed (with no arguments)
23069 before that command.
23071 @cindex hooks, post-command
23073 A hook may also be defined which is run after the command you executed.
23074 Whenever you run the command @samp{foo}, if the user-defined command
23075 @samp{hookpost-foo} exists, it is executed (with no arguments) after
23076 that command. Post-execution hooks may exist simultaneously with
23077 pre-execution hooks, for the same command.
23079 It is valid for a hook to call the command which it hooks. If this
23080 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
23082 @c It would be nice if hookpost could be passed a parameter indicating
23083 @c if the command it hooks executed properly or not. FIXME!
23085 @kindex stop@r{, a pseudo-command}
23086 In addition, a pseudo-command, @samp{stop} exists. Defining
23087 (@samp{hook-stop}) makes the associated commands execute every time
23088 execution stops in your program: before breakpoint commands are run,
23089 displays are printed, or the stack frame is printed.
23091 For example, to ignore @code{SIGALRM} signals while
23092 single-stepping, but treat them normally during normal execution,
23097 handle SIGALRM nopass
23101 handle SIGALRM pass
23104 define hook-continue
23105 handle SIGALRM pass
23109 As a further example, to hook at the beginning and end of the @code{echo}
23110 command, and to add extra text to the beginning and end of the message,
23118 define hookpost-echo
23122 (@value{GDBP}) echo Hello World
23123 <<<---Hello World--->>>
23128 You can define a hook for any single-word command in @value{GDBN}, but
23129 not for command aliases; you should define a hook for the basic command
23130 name, e.g.@: @code{backtrace} rather than @code{bt}.
23131 @c FIXME! So how does Joe User discover whether a command is an alias
23133 You can hook a multi-word command by adding @code{hook-} or
23134 @code{hookpost-} to the last word of the command, e.g.@:
23135 @samp{define target hook-remote} to add a hook to @samp{target remote}.
23137 If an error occurs during the execution of your hook, execution of
23138 @value{GDBN} commands stops and @value{GDBN} issues a prompt
23139 (before the command that you actually typed had a chance to run).
23141 If you try to define a hook which does not match any known command, you
23142 get a warning from the @code{define} command.
23144 @node Command Files
23145 @subsection Command Files
23147 @cindex command files
23148 @cindex scripting commands
23149 A command file for @value{GDBN} is a text file made of lines that are
23150 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
23151 also be included. An empty line in a command file does nothing; it
23152 does not mean to repeat the last command, as it would from the
23155 You can request the execution of a command file with the @code{source}
23156 command. Note that the @code{source} command is also used to evaluate
23157 scripts that are not Command Files. The exact behavior can be configured
23158 using the @code{script-extension} setting.
23159 @xref{Extending GDB,, Extending GDB}.
23163 @cindex execute commands from a file
23164 @item source [-s] [-v] @var{filename}
23165 Execute the command file @var{filename}.
23168 The lines in a command file are generally executed sequentially,
23169 unless the order of execution is changed by one of the
23170 @emph{flow-control commands} described below. The commands are not
23171 printed as they are executed. An error in any command terminates
23172 execution of the command file and control is returned to the console.
23174 @value{GDBN} first searches for @var{filename} in the current directory.
23175 If the file is not found there, and @var{filename} does not specify a
23176 directory, then @value{GDBN} also looks for the file on the source search path
23177 (specified with the @samp{directory} command);
23178 except that @file{$cdir} is not searched because the compilation directory
23179 is not relevant to scripts.
23181 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
23182 on the search path even if @var{filename} specifies a directory.
23183 The search is done by appending @var{filename} to each element of the
23184 search path. So, for example, if @var{filename} is @file{mylib/myscript}
23185 and the search path contains @file{/home/user} then @value{GDBN} will
23186 look for the script @file{/home/user/mylib/myscript}.
23187 The search is also done if @var{filename} is an absolute path.
23188 For example, if @var{filename} is @file{/tmp/myscript} and
23189 the search path contains @file{/home/user} then @value{GDBN} will
23190 look for the script @file{/home/user/tmp/myscript}.
23191 For DOS-like systems, if @var{filename} contains a drive specification,
23192 it is stripped before concatenation. For example, if @var{filename} is
23193 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
23194 will look for the script @file{c:/tmp/myscript}.
23196 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
23197 each command as it is executed. The option must be given before
23198 @var{filename}, and is interpreted as part of the filename anywhere else.
23200 Commands that would ask for confirmation if used interactively proceed
23201 without asking when used in a command file. Many @value{GDBN} commands that
23202 normally print messages to say what they are doing omit the messages
23203 when called from command files.
23205 @value{GDBN} also accepts command input from standard input. In this
23206 mode, normal output goes to standard output and error output goes to
23207 standard error. Errors in a command file supplied on standard input do
23208 not terminate execution of the command file---execution continues with
23212 gdb < cmds > log 2>&1
23215 (The syntax above will vary depending on the shell used.) This example
23216 will execute commands from the file @file{cmds}. All output and errors
23217 would be directed to @file{log}.
23219 Since commands stored on command files tend to be more general than
23220 commands typed interactively, they frequently need to deal with
23221 complicated situations, such as different or unexpected values of
23222 variables and symbols, changes in how the program being debugged is
23223 built, etc. @value{GDBN} provides a set of flow-control commands to
23224 deal with these complexities. Using these commands, you can write
23225 complex scripts that loop over data structures, execute commands
23226 conditionally, etc.
23233 This command allows to include in your script conditionally executed
23234 commands. The @code{if} command takes a single argument, which is an
23235 expression to evaluate. It is followed by a series of commands that
23236 are executed only if the expression is true (its value is nonzero).
23237 There can then optionally be an @code{else} line, followed by a series
23238 of commands that are only executed if the expression was false. The
23239 end of the list is marked by a line containing @code{end}.
23243 This command allows to write loops. Its syntax is similar to
23244 @code{if}: the command takes a single argument, which is an expression
23245 to evaluate, and must be followed by the commands to execute, one per
23246 line, terminated by an @code{end}. These commands are called the
23247 @dfn{body} of the loop. The commands in the body of @code{while} are
23248 executed repeatedly as long as the expression evaluates to true.
23252 This command exits the @code{while} loop in whose body it is included.
23253 Execution of the script continues after that @code{while}s @code{end}
23256 @kindex loop_continue
23257 @item loop_continue
23258 This command skips the execution of the rest of the body of commands
23259 in the @code{while} loop in whose body it is included. Execution
23260 branches to the beginning of the @code{while} loop, where it evaluates
23261 the controlling expression.
23263 @kindex end@r{ (if/else/while commands)}
23265 Terminate the block of commands that are the body of @code{if},
23266 @code{else}, or @code{while} flow-control commands.
23271 @subsection Commands for Controlled Output
23273 During the execution of a command file or a user-defined command, normal
23274 @value{GDBN} output is suppressed; the only output that appears is what is
23275 explicitly printed by the commands in the definition. This section
23276 describes three commands useful for generating exactly the output you
23281 @item echo @var{text}
23282 @c I do not consider backslash-space a standard C escape sequence
23283 @c because it is not in ANSI.
23284 Print @var{text}. Nonprinting characters can be included in
23285 @var{text} using C escape sequences, such as @samp{\n} to print a
23286 newline. @strong{No newline is printed unless you specify one.}
23287 In addition to the standard C escape sequences, a backslash followed
23288 by a space stands for a space. This is useful for displaying a
23289 string with spaces at the beginning or the end, since leading and
23290 trailing spaces are otherwise trimmed from all arguments.
23291 To print @samp{@w{ }and foo =@w{ }}, use the command
23292 @samp{echo \@w{ }and foo = \@w{ }}.
23294 A backslash at the end of @var{text} can be used, as in C, to continue
23295 the command onto subsequent lines. For example,
23298 echo This is some text\n\
23299 which is continued\n\
23300 onto several lines.\n
23303 produces the same output as
23306 echo This is some text\n
23307 echo which is continued\n
23308 echo onto several lines.\n
23312 @item output @var{expression}
23313 Print the value of @var{expression} and nothing but that value: no
23314 newlines, no @samp{$@var{nn} = }. The value is not entered in the
23315 value history either. @xref{Expressions, ,Expressions}, for more information
23318 @item output/@var{fmt} @var{expression}
23319 Print the value of @var{expression} in format @var{fmt}. You can use
23320 the same formats as for @code{print}. @xref{Output Formats,,Output
23321 Formats}, for more information.
23324 @item printf @var{template}, @var{expressions}@dots{}
23325 Print the values of one or more @var{expressions} under the control of
23326 the string @var{template}. To print several values, make
23327 @var{expressions} be a comma-separated list of individual expressions,
23328 which may be either numbers or pointers. Their values are printed as
23329 specified by @var{template}, exactly as a C program would do by
23330 executing the code below:
23333 printf (@var{template}, @var{expressions}@dots{});
23336 As in @code{C} @code{printf}, ordinary characters in @var{template}
23337 are printed verbatim, while @dfn{conversion specification} introduced
23338 by the @samp{%} character cause subsequent @var{expressions} to be
23339 evaluated, their values converted and formatted according to type and
23340 style information encoded in the conversion specifications, and then
23343 For example, you can print two values in hex like this:
23346 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
23349 @code{printf} supports all the standard @code{C} conversion
23350 specifications, including the flags and modifiers between the @samp{%}
23351 character and the conversion letter, with the following exceptions:
23355 The argument-ordering modifiers, such as @samp{2$}, are not supported.
23358 The modifier @samp{*} is not supported for specifying precision or
23362 The @samp{'} flag (for separation of digits into groups according to
23363 @code{LC_NUMERIC'}) is not supported.
23366 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
23370 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
23373 The conversion letters @samp{a} and @samp{A} are not supported.
23377 Note that the @samp{ll} type modifier is supported only if the
23378 underlying @code{C} implementation used to build @value{GDBN} supports
23379 the @code{long long int} type, and the @samp{L} type modifier is
23380 supported only if @code{long double} type is available.
23382 As in @code{C}, @code{printf} supports simple backslash-escape
23383 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
23384 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
23385 single character. Octal and hexadecimal escape sequences are not
23388 Additionally, @code{printf} supports conversion specifications for DFP
23389 (@dfn{Decimal Floating Point}) types using the following length modifiers
23390 together with a floating point specifier.
23395 @samp{H} for printing @code{Decimal32} types.
23398 @samp{D} for printing @code{Decimal64} types.
23401 @samp{DD} for printing @code{Decimal128} types.
23404 If the underlying @code{C} implementation used to build @value{GDBN} has
23405 support for the three length modifiers for DFP types, other modifiers
23406 such as width and precision will also be available for @value{GDBN} to use.
23408 In case there is no such @code{C} support, no additional modifiers will be
23409 available and the value will be printed in the standard way.
23411 Here's an example of printing DFP types using the above conversion letters:
23413 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
23417 @item eval @var{template}, @var{expressions}@dots{}
23418 Convert the values of one or more @var{expressions} under the control of
23419 the string @var{template} to a command line, and call it.
23423 @node Auto-loading sequences
23424 @subsection Controlling auto-loading native @value{GDBN} scripts
23425 @cindex native script auto-loading
23427 When a new object file is read (for example, due to the @code{file}
23428 command, or because the inferior has loaded a shared library),
23429 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
23430 @xref{Auto-loading extensions}.
23432 Auto-loading can be enabled or disabled,
23433 and the list of auto-loaded scripts can be printed.
23436 @anchor{set auto-load gdb-scripts}
23437 @kindex set auto-load gdb-scripts
23438 @item set auto-load gdb-scripts [on|off]
23439 Enable or disable the auto-loading of canned sequences of commands scripts.
23441 @anchor{show auto-load gdb-scripts}
23442 @kindex show auto-load gdb-scripts
23443 @item show auto-load gdb-scripts
23444 Show whether auto-loading of canned sequences of commands scripts is enabled or
23447 @anchor{info auto-load gdb-scripts}
23448 @kindex info auto-load gdb-scripts
23449 @cindex print list of auto-loaded canned sequences of commands scripts
23450 @item info auto-load gdb-scripts [@var{regexp}]
23451 Print the list of all canned sequences of commands scripts that @value{GDBN}
23455 If @var{regexp} is supplied only canned sequences of commands scripts with
23456 matching names are printed.
23459 @section Extending @value{GDBN} using Python
23460 @cindex python scripting
23461 @cindex scripting with python
23463 You can extend @value{GDBN} using the @uref{http://www.python.org/,
23464 Python programming language}. This feature is available only if
23465 @value{GDBN} was configured using @option{--with-python}.
23467 @cindex python directory
23468 Python scripts used by @value{GDBN} should be installed in
23469 @file{@var{data-directory}/python}, where @var{data-directory} is
23470 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
23471 This directory, known as the @dfn{python directory},
23472 is automatically added to the Python Search Path in order to allow
23473 the Python interpreter to locate all scripts installed at this location.
23475 Additionally, @value{GDBN} commands and convenience functions which
23476 are written in Python and are located in the
23477 @file{@var{data-directory}/python/gdb/command} or
23478 @file{@var{data-directory}/python/gdb/function} directories are
23479 automatically imported when @value{GDBN} starts.
23482 * Python Commands:: Accessing Python from @value{GDBN}.
23483 * Python API:: Accessing @value{GDBN} from Python.
23484 * Python Auto-loading:: Automatically loading Python code.
23485 * Python modules:: Python modules provided by @value{GDBN}.
23488 @node Python Commands
23489 @subsection Python Commands
23490 @cindex python commands
23491 @cindex commands to access python
23493 @value{GDBN} provides two commands for accessing the Python interpreter,
23494 and one related setting:
23497 @kindex python-interactive
23499 @item python-interactive @r{[}@var{command}@r{]}
23500 @itemx pi @r{[}@var{command}@r{]}
23501 Without an argument, the @code{python-interactive} command can be used
23502 to start an interactive Python prompt. To return to @value{GDBN},
23503 type the @code{EOF} character (e.g., @kbd{Ctrl-D} on an empty prompt).
23505 Alternatively, a single-line Python command can be given as an
23506 argument and evaluated. If the command is an expression, the result
23507 will be printed; otherwise, nothing will be printed. For example:
23510 (@value{GDBP}) python-interactive 2 + 3
23516 @item python @r{[}@var{command}@r{]}
23517 @itemx py @r{[}@var{command}@r{]}
23518 The @code{python} command can be used to evaluate Python code.
23520 If given an argument, the @code{python} command will evaluate the
23521 argument as a Python command. For example:
23524 (@value{GDBP}) python print 23
23528 If you do not provide an argument to @code{python}, it will act as a
23529 multi-line command, like @code{define}. In this case, the Python
23530 script is made up of subsequent command lines, given after the
23531 @code{python} command. This command list is terminated using a line
23532 containing @code{end}. For example:
23535 (@value{GDBP}) python
23537 End with a line saying just "end".
23543 @kindex set python print-stack
23544 @item set python print-stack
23545 By default, @value{GDBN} will print only the message component of a
23546 Python exception when an error occurs in a Python script. This can be
23547 controlled using @code{set python print-stack}: if @code{full}, then
23548 full Python stack printing is enabled; if @code{none}, then Python stack
23549 and message printing is disabled; if @code{message}, the default, only
23550 the message component of the error is printed.
23553 It is also possible to execute a Python script from the @value{GDBN}
23557 @item source @file{script-name}
23558 The script name must end with @samp{.py} and @value{GDBN} must be configured
23559 to recognize the script language based on filename extension using
23560 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
23562 @item python execfile ("script-name")
23563 This method is based on the @code{execfile} Python built-in function,
23564 and thus is always available.
23568 @subsection Python API
23570 @cindex programming in python
23572 You can get quick online help for @value{GDBN}'s Python API by issuing
23573 the command @w{@kbd{python help (gdb)}}.
23575 Functions and methods which have two or more optional arguments allow
23576 them to be specified using keyword syntax. This allows passing some
23577 optional arguments while skipping others. Example:
23578 @w{@code{gdb.some_function ('foo', bar = 1, baz = 2)}}.
23581 * Basic Python:: Basic Python Functions.
23582 * Exception Handling:: How Python exceptions are translated.
23583 * Values From Inferior:: Python representation of values.
23584 * Types In Python:: Python representation of types.
23585 * Pretty Printing API:: Pretty-printing values.
23586 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
23587 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
23588 * Type Printing API:: Pretty-printing types.
23589 * Frame Filter API:: Filtering Frames.
23590 * Frame Decorator API:: Decorating Frames.
23591 * Writing a Frame Filter:: Writing a Frame Filter.
23592 * Inferiors In Python:: Python representation of inferiors (processes)
23593 * Events In Python:: Listening for events from @value{GDBN}.
23594 * Threads In Python:: Accessing inferior threads from Python.
23595 * Commands In Python:: Implementing new commands in Python.
23596 * Parameters In Python:: Adding new @value{GDBN} parameters.
23597 * Functions In Python:: Writing new convenience functions.
23598 * Progspaces In Python:: Program spaces.
23599 * Objfiles In Python:: Object files.
23600 * Frames In Python:: Accessing inferior stack frames from Python.
23601 * Blocks In Python:: Accessing blocks from Python.
23602 * Symbols In Python:: Python representation of symbols.
23603 * Symbol Tables In Python:: Python representation of symbol tables.
23604 * Line Tables In Python:: Python representation of line tables.
23605 * Breakpoints In Python:: Manipulating breakpoints using Python.
23606 * Finish Breakpoints in Python:: Setting Breakpoints on function return
23608 * Lazy Strings In Python:: Python representation of lazy strings.
23609 * Architectures In Python:: Python representation of architectures.
23613 @subsubsection Basic Python
23615 @cindex python stdout
23616 @cindex python pagination
23617 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
23618 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
23619 A Python program which outputs to one of these streams may have its
23620 output interrupted by the user (@pxref{Screen Size}). In this
23621 situation, a Python @code{KeyboardInterrupt} exception is thrown.
23623 Some care must be taken when writing Python code to run in
23624 @value{GDBN}. Two things worth noting in particular:
23628 @value{GDBN} install handlers for @code{SIGCHLD} and @code{SIGINT}.
23629 Python code must not override these, or even change the options using
23630 @code{sigaction}. If your program changes the handling of these
23631 signals, @value{GDBN} will most likely stop working correctly. Note
23632 that it is unfortunately common for GUI toolkits to install a
23633 @code{SIGCHLD} handler.
23636 @value{GDBN} takes care to mark its internal file descriptors as
23637 close-on-exec. However, this cannot be done in a thread-safe way on
23638 all platforms. Your Python programs should be aware of this and
23639 should both create new file descriptors with the close-on-exec flag
23640 set and arrange to close unneeded file descriptors before starting a
23644 @cindex python functions
23645 @cindex python module
23647 @value{GDBN} introduces a new Python module, named @code{gdb}. All
23648 methods and classes added by @value{GDBN} are placed in this module.
23649 @value{GDBN} automatically @code{import}s the @code{gdb} module for
23650 use in all scripts evaluated by the @code{python} command.
23652 @findex gdb.PYTHONDIR
23653 @defvar gdb.PYTHONDIR
23654 A string containing the python directory (@pxref{Python}).
23657 @findex gdb.execute
23658 @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]})
23659 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
23660 If a GDB exception happens while @var{command} runs, it is
23661 translated as described in @ref{Exception Handling,,Exception Handling}.
23663 @var{from_tty} specifies whether @value{GDBN} ought to consider this
23664 command as having originated from the user invoking it interactively.
23665 It must be a boolean value. If omitted, it defaults to @code{False}.
23667 By default, any output produced by @var{command} is sent to
23668 @value{GDBN}'s standard output. If the @var{to_string} parameter is
23669 @code{True}, then output will be collected by @code{gdb.execute} and
23670 returned as a string. The default is @code{False}, in which case the
23671 return value is @code{None}. If @var{to_string} is @code{True}, the
23672 @value{GDBN} virtual terminal will be temporarily set to unlimited width
23673 and height, and its pagination will be disabled; @pxref{Screen Size}.
23676 @findex gdb.breakpoints
23677 @defun gdb.breakpoints ()
23678 Return a sequence holding all of @value{GDBN}'s breakpoints.
23679 @xref{Breakpoints In Python}, for more information.
23682 @findex gdb.parameter
23683 @defun gdb.parameter (parameter)
23684 Return the value of a @value{GDBN} parameter. @var{parameter} is a
23685 string naming the parameter to look up; @var{parameter} may contain
23686 spaces if the parameter has a multi-part name. For example,
23687 @samp{print object} is a valid parameter name.
23689 If the named parameter does not exist, this function throws a
23690 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
23691 parameter's value is converted to a Python value of the appropriate
23692 type, and returned.
23695 @findex gdb.history
23696 @defun gdb.history (number)
23697 Return a value from @value{GDBN}'s value history (@pxref{Value
23698 History}). @var{number} indicates which history element to return.
23699 If @var{number} is negative, then @value{GDBN} will take its absolute value
23700 and count backward from the last element (i.e., the most recent element) to
23701 find the value to return. If @var{number} is zero, then @value{GDBN} will
23702 return the most recent element. If the element specified by @var{number}
23703 doesn't exist in the value history, a @code{gdb.error} exception will be
23706 If no exception is raised, the return value is always an instance of
23707 @code{gdb.Value} (@pxref{Values From Inferior}).
23710 @findex gdb.parse_and_eval
23711 @defun gdb.parse_and_eval (expression)
23712 Parse @var{expression} as an expression in the current language,
23713 evaluate it, and return the result as a @code{gdb.Value}.
23714 @var{expression} must be a string.
23716 This function can be useful when implementing a new command
23717 (@pxref{Commands In Python}), as it provides a way to parse the
23718 command's argument as an expression. It is also useful simply to
23719 compute values, for example, it is the only way to get the value of a
23720 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
23723 @findex gdb.find_pc_line
23724 @defun gdb.find_pc_line (pc)
23725 Return the @code{gdb.Symtab_and_line} object corresponding to the
23726 @var{pc} value. @xref{Symbol Tables In Python}. If an invalid
23727 value of @var{pc} is passed as an argument, then the @code{symtab} and
23728 @code{line} attributes of the returned @code{gdb.Symtab_and_line} object
23729 will be @code{None} and 0 respectively.
23732 @findex gdb.post_event
23733 @defun gdb.post_event (event)
23734 Put @var{event}, a callable object taking no arguments, into
23735 @value{GDBN}'s internal event queue. This callable will be invoked at
23736 some later point, during @value{GDBN}'s event processing. Events
23737 posted using @code{post_event} will be run in the order in which they
23738 were posted; however, there is no way to know when they will be
23739 processed relative to other events inside @value{GDBN}.
23741 @value{GDBN} is not thread-safe. If your Python program uses multiple
23742 threads, you must be careful to only call @value{GDBN}-specific
23743 functions in the main @value{GDBN} thread. @code{post_event} ensures
23747 (@value{GDBP}) python
23751 > def __init__(self, message):
23752 > self.message = message;
23753 > def __call__(self):
23754 > gdb.write(self.message)
23756 >class MyThread1 (threading.Thread):
23758 > gdb.post_event(Writer("Hello "))
23760 >class MyThread2 (threading.Thread):
23762 > gdb.post_event(Writer("World\n"))
23764 >MyThread1().start()
23765 >MyThread2().start()
23767 (@value{GDBP}) Hello World
23772 @defun gdb.write (string @r{[}, stream{]})
23773 Print a string to @value{GDBN}'s paginated output stream. The
23774 optional @var{stream} determines the stream to print to. The default
23775 stream is @value{GDBN}'s standard output stream. Possible stream
23782 @value{GDBN}'s standard output stream.
23787 @value{GDBN}'s standard error stream.
23792 @value{GDBN}'s log stream (@pxref{Logging Output}).
23795 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
23796 call this function and will automatically direct the output to the
23801 @defun gdb.flush ()
23802 Flush the buffer of a @value{GDBN} paginated stream so that the
23803 contents are displayed immediately. @value{GDBN} will flush the
23804 contents of a stream automatically when it encounters a newline in the
23805 buffer. The optional @var{stream} determines the stream to flush. The
23806 default stream is @value{GDBN}'s standard output stream. Possible
23813 @value{GDBN}'s standard output stream.
23818 @value{GDBN}'s standard error stream.
23823 @value{GDBN}'s log stream (@pxref{Logging Output}).
23827 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
23828 call this function for the relevant stream.
23831 @findex gdb.target_charset
23832 @defun gdb.target_charset ()
23833 Return the name of the current target character set (@pxref{Character
23834 Sets}). This differs from @code{gdb.parameter('target-charset')} in
23835 that @samp{auto} is never returned.
23838 @findex gdb.target_wide_charset
23839 @defun gdb.target_wide_charset ()
23840 Return the name of the current target wide character set
23841 (@pxref{Character Sets}). This differs from
23842 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
23846 @findex gdb.solib_name
23847 @defun gdb.solib_name (address)
23848 Return the name of the shared library holding the given @var{address}
23849 as a string, or @code{None}.
23852 @findex gdb.decode_line
23853 @defun gdb.decode_line @r{[}expression@r{]}
23854 Return locations of the line specified by @var{expression}, or of the
23855 current line if no argument was given. This function returns a Python
23856 tuple containing two elements. The first element contains a string
23857 holding any unparsed section of @var{expression} (or @code{None} if
23858 the expression has been fully parsed). The second element contains
23859 either @code{None} or another tuple that contains all the locations
23860 that match the expression represented as @code{gdb.Symtab_and_line}
23861 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
23862 provided, it is decoded the way that @value{GDBN}'s inbuilt
23863 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
23866 @defun gdb.prompt_hook (current_prompt)
23867 @anchor{prompt_hook}
23869 If @var{prompt_hook} is callable, @value{GDBN} will call the method
23870 assigned to this operation before a prompt is displayed by
23873 The parameter @code{current_prompt} contains the current @value{GDBN}
23874 prompt. This method must return a Python string, or @code{None}. If
23875 a string is returned, the @value{GDBN} prompt will be set to that
23876 string. If @code{None} is returned, @value{GDBN} will continue to use
23877 the current prompt.
23879 Some prompts cannot be substituted in @value{GDBN}. Secondary prompts
23880 such as those used by readline for command input, and annotation
23881 related prompts are prohibited from being changed.
23884 @node Exception Handling
23885 @subsubsection Exception Handling
23886 @cindex python exceptions
23887 @cindex exceptions, python
23889 When executing the @code{python} command, Python exceptions
23890 uncaught within the Python code are translated to calls to
23891 @value{GDBN} error-reporting mechanism. If the command that called
23892 @code{python} does not handle the error, @value{GDBN} will
23893 terminate it and print an error message containing the Python
23894 exception name, the associated value, and the Python call stack
23895 backtrace at the point where the exception was raised. Example:
23898 (@value{GDBP}) python print foo
23899 Traceback (most recent call last):
23900 File "<string>", line 1, in <module>
23901 NameError: name 'foo' is not defined
23904 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
23905 Python code are converted to Python exceptions. The type of the
23906 Python exception depends on the error.
23910 This is the base class for most exceptions generated by @value{GDBN}.
23911 It is derived from @code{RuntimeError}, for compatibility with earlier
23912 versions of @value{GDBN}.
23914 If an error occurring in @value{GDBN} does not fit into some more
23915 specific category, then the generated exception will have this type.
23917 @item gdb.MemoryError
23918 This is a subclass of @code{gdb.error} which is thrown when an
23919 operation tried to access invalid memory in the inferior.
23921 @item KeyboardInterrupt
23922 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
23923 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
23926 In all cases, your exception handler will see the @value{GDBN} error
23927 message as its value and the Python call stack backtrace at the Python
23928 statement closest to where the @value{GDBN} error occured as the
23931 @findex gdb.GdbError
23932 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
23933 it is useful to be able to throw an exception that doesn't cause a
23934 traceback to be printed. For example, the user may have invoked the
23935 command incorrectly. Use the @code{gdb.GdbError} exception
23936 to handle this case. Example:
23940 >class HelloWorld (gdb.Command):
23941 > """Greet the whole world."""
23942 > def __init__ (self):
23943 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
23944 > def invoke (self, args, from_tty):
23945 > argv = gdb.string_to_argv (args)
23946 > if len (argv) != 0:
23947 > raise gdb.GdbError ("hello-world takes no arguments")
23948 > print "Hello, World!"
23951 (gdb) hello-world 42
23952 hello-world takes no arguments
23955 @node Values From Inferior
23956 @subsubsection Values From Inferior
23957 @cindex values from inferior, with Python
23958 @cindex python, working with values from inferior
23960 @cindex @code{gdb.Value}
23961 @value{GDBN} provides values it obtains from the inferior program in
23962 an object of type @code{gdb.Value}. @value{GDBN} uses this object
23963 for its internal bookkeeping of the inferior's values, and for
23964 fetching values when necessary.
23966 Inferior values that are simple scalars can be used directly in
23967 Python expressions that are valid for the value's data type. Here's
23968 an example for an integer or floating-point value @code{some_val}:
23975 As result of this, @code{bar} will also be a @code{gdb.Value} object
23976 whose values are of the same type as those of @code{some_val}.
23978 Inferior values that are structures or instances of some class can
23979 be accessed using the Python @dfn{dictionary syntax}. For example, if
23980 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
23981 can access its @code{foo} element with:
23984 bar = some_val['foo']
23987 @cindex getting structure elements using gdb.Field objects as subscripts
23988 Again, @code{bar} will also be a @code{gdb.Value} object. Structure
23989 elements can also be accessed by using @code{gdb.Field} objects as
23990 subscripts (@pxref{Types In Python}, for more information on
23991 @code{gdb.Field} objects). For example, if @code{foo_field} is a
23992 @code{gdb.Field} object corresponding to element @code{foo} of the above
23993 structure, then @code{bar} can also be accessed as follows:
23996 bar = some_val[foo_field]
23999 A @code{gdb.Value} that represents a function can be executed via
24000 inferior function call. Any arguments provided to the call must match
24001 the function's prototype, and must be provided in the order specified
24004 For example, @code{some_val} is a @code{gdb.Value} instance
24005 representing a function that takes two integers as arguments. To
24006 execute this function, call it like so:
24009 result = some_val (10,20)
24012 Any values returned from a function call will be stored as a
24015 The following attributes are provided:
24017 @defvar Value.address
24018 If this object is addressable, this read-only attribute holds a
24019 @code{gdb.Value} object representing the address. Otherwise,
24020 this attribute holds @code{None}.
24023 @cindex optimized out value in Python
24024 @defvar Value.is_optimized_out
24025 This read-only boolean attribute is true if the compiler optimized out
24026 this value, thus it is not available for fetching from the inferior.
24030 The type of this @code{gdb.Value}. The value of this attribute is a
24031 @code{gdb.Type} object (@pxref{Types In Python}).
24034 @defvar Value.dynamic_type
24035 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
24036 type information (@acronym{RTTI}) to determine the dynamic type of the
24037 value. If this value is of class type, it will return the class in
24038 which the value is embedded, if any. If this value is of pointer or
24039 reference to a class type, it will compute the dynamic type of the
24040 referenced object, and return a pointer or reference to that type,
24041 respectively. In all other cases, it will return the value's static
24044 Note that this feature will only work when debugging a C@t{++} program
24045 that includes @acronym{RTTI} for the object in question. Otherwise,
24046 it will just return the static type of the value as in @kbd{ptype foo}
24047 (@pxref{Symbols, ptype}).
24050 @defvar Value.is_lazy
24051 The value of this read-only boolean attribute is @code{True} if this
24052 @code{gdb.Value} has not yet been fetched from the inferior.
24053 @value{GDBN} does not fetch values until necessary, for efficiency.
24057 myval = gdb.parse_and_eval ('somevar')
24060 The value of @code{somevar} is not fetched at this time. It will be
24061 fetched when the value is needed, or when the @code{fetch_lazy}
24065 The following methods are provided:
24067 @defun Value.__init__ (@var{val})
24068 Many Python values can be converted directly to a @code{gdb.Value} via
24069 this object initializer. Specifically:
24072 @item Python boolean
24073 A Python boolean is converted to the boolean type from the current
24076 @item Python integer
24077 A Python integer is converted to the C @code{long} type for the
24078 current architecture.
24081 A Python long is converted to the C @code{long long} type for the
24082 current architecture.
24085 A Python float is converted to the C @code{double} type for the
24086 current architecture.
24088 @item Python string
24089 A Python string is converted to a target string, using the current
24092 @item @code{gdb.Value}
24093 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
24095 @item @code{gdb.LazyString}
24096 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
24097 Python}), then the lazy string's @code{value} method is called, and
24098 its result is used.
24102 @defun Value.cast (type)
24103 Return a new instance of @code{gdb.Value} that is the result of
24104 casting this instance to the type described by @var{type}, which must
24105 be a @code{gdb.Type} object. If the cast cannot be performed for some
24106 reason, this method throws an exception.
24109 @defun Value.dereference ()
24110 For pointer data types, this method returns a new @code{gdb.Value} object
24111 whose contents is the object pointed to by the pointer. For example, if
24112 @code{foo} is a C pointer to an @code{int}, declared in your C program as
24119 then you can use the corresponding @code{gdb.Value} to access what
24120 @code{foo} points to like this:
24123 bar = foo.dereference ()
24126 The result @code{bar} will be a @code{gdb.Value} object holding the
24127 value pointed to by @code{foo}.
24129 A similar function @code{Value.referenced_value} exists which also
24130 returns @code{gdb.Value} objects corresonding to the values pointed to
24131 by pointer values (and additionally, values referenced by reference
24132 values). However, the behavior of @code{Value.dereference}
24133 differs from @code{Value.referenced_value} by the fact that the
24134 behavior of @code{Value.dereference} is identical to applying the C
24135 unary operator @code{*} on a given value. For example, consider a
24136 reference to a pointer @code{ptrref}, declared in your C@t{++} program
24140 typedef int *intptr;
24144 intptr &ptrref = ptr;
24147 Though @code{ptrref} is a reference value, one can apply the method
24148 @code{Value.dereference} to the @code{gdb.Value} object corresponding
24149 to it and obtain a @code{gdb.Value} which is identical to that
24150 corresponding to @code{val}. However, if you apply the method
24151 @code{Value.referenced_value}, the result would be a @code{gdb.Value}
24152 object identical to that corresponding to @code{ptr}.
24155 py_ptrref = gdb.parse_and_eval ("ptrref")
24156 py_val = py_ptrref.dereference ()
24157 py_ptr = py_ptrref.referenced_value ()
24160 The @code{gdb.Value} object @code{py_val} is identical to that
24161 corresponding to @code{val}, and @code{py_ptr} is identical to that
24162 corresponding to @code{ptr}. In general, @code{Value.dereference} can
24163 be applied whenever the C unary operator @code{*} can be applied
24164 to the corresponding C value. For those cases where applying both
24165 @code{Value.dereference} and @code{Value.referenced_value} is allowed,
24166 the results obtained need not be identical (as we have seen in the above
24167 example). The results are however identical when applied on
24168 @code{gdb.Value} objects corresponding to pointers (@code{gdb.Value}
24169 objects with type code @code{TYPE_CODE_PTR}) in a C/C@t{++} program.
24172 @defun Value.referenced_value ()
24173 For pointer or reference data types, this method returns a new
24174 @code{gdb.Value} object corresponding to the value referenced by the
24175 pointer/reference value. For pointer data types,
24176 @code{Value.dereference} and @code{Value.referenced_value} produce
24177 identical results. The difference between these methods is that
24178 @code{Value.dereference} cannot get the values referenced by reference
24179 values. For example, consider a reference to an @code{int}, declared
24180 in your C@t{++} program as
24188 then applying @code{Value.dereference} to the @code{gdb.Value} object
24189 corresponding to @code{ref} will result in an error, while applying
24190 @code{Value.referenced_value} will result in a @code{gdb.Value} object
24191 identical to that corresponding to @code{val}.
24194 py_ref = gdb.parse_and_eval ("ref")
24195 er_ref = py_ref.dereference () # Results in error
24196 py_val = py_ref.referenced_value () # Returns the referenced value
24199 The @code{gdb.Value} object @code{py_val} is identical to that
24200 corresponding to @code{val}.
24203 @defun Value.dynamic_cast (type)
24204 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
24205 operator were used. Consult a C@t{++} reference for details.
24208 @defun Value.reinterpret_cast (type)
24209 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
24210 operator were used. Consult a C@t{++} reference for details.
24213 @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]})
24214 If this @code{gdb.Value} represents a string, then this method
24215 converts the contents to a Python string. Otherwise, this method will
24216 throw an exception.
24218 Strings are recognized in a language-specific way; whether a given
24219 @code{gdb.Value} represents a string is determined by the current
24222 For C-like languages, a value is a string if it is a pointer to or an
24223 array of characters or ints. The string is assumed to be terminated
24224 by a zero of the appropriate width. However if the optional length
24225 argument is given, the string will be converted to that given length,
24226 ignoring any embedded zeros that the string may contain.
24228 If the optional @var{encoding} argument is given, it must be a string
24229 naming the encoding of the string in the @code{gdb.Value}, such as
24230 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
24231 the same encodings as the corresponding argument to Python's
24232 @code{string.decode} method, and the Python codec machinery will be used
24233 to convert the string. If @var{encoding} is not given, or if
24234 @var{encoding} is the empty string, then either the @code{target-charset}
24235 (@pxref{Character Sets}) will be used, or a language-specific encoding
24236 will be used, if the current language is able to supply one.
24238 The optional @var{errors} argument is the same as the corresponding
24239 argument to Python's @code{string.decode} method.
24241 If the optional @var{length} argument is given, the string will be
24242 fetched and converted to the given length.
24245 @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]})
24246 If this @code{gdb.Value} represents a string, then this method
24247 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
24248 In Python}). Otherwise, this method will throw an exception.
24250 If the optional @var{encoding} argument is given, it must be a string
24251 naming the encoding of the @code{gdb.LazyString}. Some examples are:
24252 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
24253 @var{encoding} argument is an encoding that @value{GDBN} does
24254 recognize, @value{GDBN} will raise an error.
24256 When a lazy string is printed, the @value{GDBN} encoding machinery is
24257 used to convert the string during printing. If the optional
24258 @var{encoding} argument is not provided, or is an empty string,
24259 @value{GDBN} will automatically select the encoding most suitable for
24260 the string type. For further information on encoding in @value{GDBN}
24261 please see @ref{Character Sets}.
24263 If the optional @var{length} argument is given, the string will be
24264 fetched and encoded to the length of characters specified. If
24265 the @var{length} argument is not provided, the string will be fetched
24266 and encoded until a null of appropriate width is found.
24269 @defun Value.fetch_lazy ()
24270 If the @code{gdb.Value} object is currently a lazy value
24271 (@code{gdb.Value.is_lazy} is @code{True}), then the value is
24272 fetched from the inferior. Any errors that occur in the process
24273 will produce a Python exception.
24275 If the @code{gdb.Value} object is not a lazy value, this method
24278 This method does not return a value.
24282 @node Types In Python
24283 @subsubsection Types In Python
24284 @cindex types in Python
24285 @cindex Python, working with types
24288 @value{GDBN} represents types from the inferior using the class
24291 The following type-related functions are available in the @code{gdb}
24294 @findex gdb.lookup_type
24295 @defun gdb.lookup_type (name @r{[}, block@r{]})
24296 This function looks up a type by name. @var{name} is the name of the
24297 type to look up. It must be a string.
24299 If @var{block} is given, then @var{name} is looked up in that scope.
24300 Otherwise, it is searched for globally.
24302 Ordinarily, this function will return an instance of @code{gdb.Type}.
24303 If the named type cannot be found, it will throw an exception.
24306 If the type is a structure or class type, or an enum type, the fields
24307 of that type can be accessed using the Python @dfn{dictionary syntax}.
24308 For example, if @code{some_type} is a @code{gdb.Type} instance holding
24309 a structure type, you can access its @code{foo} field with:
24312 bar = some_type['foo']
24315 @code{bar} will be a @code{gdb.Field} object; see below under the
24316 description of the @code{Type.fields} method for a description of the
24317 @code{gdb.Field} class.
24319 An instance of @code{Type} has the following attributes:
24322 The type code for this type. The type code will be one of the
24323 @code{TYPE_CODE_} constants defined below.
24327 The name of this type. If this type has no name, then @code{None}
24331 @defvar Type.sizeof
24332 The size of this type, in target @code{char} units. Usually, a
24333 target's @code{char} type will be an 8-bit byte. However, on some
24334 unusual platforms, this type may have a different size.
24338 The tag name for this type. The tag name is the name after
24339 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
24340 languages have this concept. If this type has no tag name, then
24341 @code{None} is returned.
24344 The following methods are provided:
24346 @defun Type.fields ()
24347 For structure and union types, this method returns the fields. Range
24348 types have two fields, the minimum and maximum values. Enum types
24349 have one field per enum constant. Function and method types have one
24350 field per parameter. The base types of C@t{++} classes are also
24351 represented as fields. If the type has no fields, or does not fit
24352 into one of these categories, an empty sequence will be returned.
24354 Each field is a @code{gdb.Field} object, with some pre-defined attributes:
24357 This attribute is not available for @code{enum} or @code{static}
24358 (as in C@t{++} or Java) fields. The value is the position, counting
24359 in bits, from the start of the containing type.
24362 This attribute is only available for @code{enum} fields, and its value
24363 is the enumeration member's integer representation.
24366 The name of the field, or @code{None} for anonymous fields.
24369 This is @code{True} if the field is artificial, usually meaning that
24370 it was provided by the compiler and not the user. This attribute is
24371 always provided, and is @code{False} if the field is not artificial.
24373 @item is_base_class
24374 This is @code{True} if the field represents a base class of a C@t{++}
24375 structure. This attribute is always provided, and is @code{False}
24376 if the field is not a base class of the type that is the argument of
24377 @code{fields}, or if that type was not a C@t{++} class.
24380 If the field is packed, or is a bitfield, then this will have a
24381 non-zero value, which is the size of the field in bits. Otherwise,
24382 this will be zero; in this case the field's size is given by its type.
24385 The type of the field. This is usually an instance of @code{Type},
24386 but it can be @code{None} in some situations.
24389 The type which contains this field. This is an instance of
24394 @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]})
24395 Return a new @code{gdb.Type} object which represents an array of this
24396 type. If one argument is given, it is the inclusive upper bound of
24397 the array; in this case the lower bound is zero. If two arguments are
24398 given, the first argument is the lower bound of the array, and the
24399 second argument is the upper bound of the array. An array's length
24400 must not be negative, but the bounds can be.
24403 @defun Type.vector (@var{n1} @r{[}, @var{n2}@r{]})
24404 Return a new @code{gdb.Type} object which represents a vector of this
24405 type. If one argument is given, it is the inclusive upper bound of
24406 the vector; in this case the lower bound is zero. If two arguments are
24407 given, the first argument is the lower bound of the vector, and the
24408 second argument is the upper bound of the vector. A vector's length
24409 must not be negative, but the bounds can be.
24411 The difference between an @code{array} and a @code{vector} is that
24412 arrays behave like in C: when used in expressions they decay to a pointer
24413 to the first element whereas vectors are treated as first class values.
24416 @defun Type.const ()
24417 Return a new @code{gdb.Type} object which represents a
24418 @code{const}-qualified variant of this type.
24421 @defun Type.volatile ()
24422 Return a new @code{gdb.Type} object which represents a
24423 @code{volatile}-qualified variant of this type.
24426 @defun Type.unqualified ()
24427 Return a new @code{gdb.Type} object which represents an unqualified
24428 variant of this type. That is, the result is neither @code{const} nor
24432 @defun Type.range ()
24433 Return a Python @code{Tuple} object that contains two elements: the
24434 low bound of the argument type and the high bound of that type. If
24435 the type does not have a range, @value{GDBN} will raise a
24436 @code{gdb.error} exception (@pxref{Exception Handling}).
24439 @defun Type.reference ()
24440 Return a new @code{gdb.Type} object which represents a reference to this
24444 @defun Type.pointer ()
24445 Return a new @code{gdb.Type} object which represents a pointer to this
24449 @defun Type.strip_typedefs ()
24450 Return a new @code{gdb.Type} that represents the real type,
24451 after removing all layers of typedefs.
24454 @defun Type.target ()
24455 Return a new @code{gdb.Type} object which represents the target type
24458 For a pointer type, the target type is the type of the pointed-to
24459 object. For an array type (meaning C-like arrays), the target type is
24460 the type of the elements of the array. For a function or method type,
24461 the target type is the type of the return value. For a complex type,
24462 the target type is the type of the elements. For a typedef, the
24463 target type is the aliased type.
24465 If the type does not have a target, this method will throw an
24469 @defun Type.template_argument (n @r{[}, block@r{]})
24470 If this @code{gdb.Type} is an instantiation of a template, this will
24471 return a new @code{gdb.Type} which represents the type of the
24472 @var{n}th template argument.
24474 If this @code{gdb.Type} is not a template type, this will throw an
24475 exception. Ordinarily, only C@t{++} code will have template types.
24477 If @var{block} is given, then @var{name} is looked up in that scope.
24478 Otherwise, it is searched for globally.
24482 Each type has a code, which indicates what category this type falls
24483 into. The available type categories are represented by constants
24484 defined in the @code{gdb} module:
24487 @findex TYPE_CODE_PTR
24488 @findex gdb.TYPE_CODE_PTR
24489 @item gdb.TYPE_CODE_PTR
24490 The type is a pointer.
24492 @findex TYPE_CODE_ARRAY
24493 @findex gdb.TYPE_CODE_ARRAY
24494 @item gdb.TYPE_CODE_ARRAY
24495 The type is an array.
24497 @findex TYPE_CODE_STRUCT
24498 @findex gdb.TYPE_CODE_STRUCT
24499 @item gdb.TYPE_CODE_STRUCT
24500 The type is a structure.
24502 @findex TYPE_CODE_UNION
24503 @findex gdb.TYPE_CODE_UNION
24504 @item gdb.TYPE_CODE_UNION
24505 The type is a union.
24507 @findex TYPE_CODE_ENUM
24508 @findex gdb.TYPE_CODE_ENUM
24509 @item gdb.TYPE_CODE_ENUM
24510 The type is an enum.
24512 @findex TYPE_CODE_FLAGS
24513 @findex gdb.TYPE_CODE_FLAGS
24514 @item gdb.TYPE_CODE_FLAGS
24515 A bit flags type, used for things such as status registers.
24517 @findex TYPE_CODE_FUNC
24518 @findex gdb.TYPE_CODE_FUNC
24519 @item gdb.TYPE_CODE_FUNC
24520 The type is a function.
24522 @findex TYPE_CODE_INT
24523 @findex gdb.TYPE_CODE_INT
24524 @item gdb.TYPE_CODE_INT
24525 The type is an integer type.
24527 @findex TYPE_CODE_FLT
24528 @findex gdb.TYPE_CODE_FLT
24529 @item gdb.TYPE_CODE_FLT
24530 A floating point type.
24532 @findex TYPE_CODE_VOID
24533 @findex gdb.TYPE_CODE_VOID
24534 @item gdb.TYPE_CODE_VOID
24535 The special type @code{void}.
24537 @findex TYPE_CODE_SET
24538 @findex gdb.TYPE_CODE_SET
24539 @item gdb.TYPE_CODE_SET
24542 @findex TYPE_CODE_RANGE
24543 @findex gdb.TYPE_CODE_RANGE
24544 @item gdb.TYPE_CODE_RANGE
24545 A range type, that is, an integer type with bounds.
24547 @findex TYPE_CODE_STRING
24548 @findex gdb.TYPE_CODE_STRING
24549 @item gdb.TYPE_CODE_STRING
24550 A string type. Note that this is only used for certain languages with
24551 language-defined string types; C strings are not represented this way.
24553 @findex TYPE_CODE_BITSTRING
24554 @findex gdb.TYPE_CODE_BITSTRING
24555 @item gdb.TYPE_CODE_BITSTRING
24556 A string of bits. It is deprecated.
24558 @findex TYPE_CODE_ERROR
24559 @findex gdb.TYPE_CODE_ERROR
24560 @item gdb.TYPE_CODE_ERROR
24561 An unknown or erroneous type.
24563 @findex TYPE_CODE_METHOD
24564 @findex gdb.TYPE_CODE_METHOD
24565 @item gdb.TYPE_CODE_METHOD
24566 A method type, as found in C@t{++} or Java.
24568 @findex TYPE_CODE_METHODPTR
24569 @findex gdb.TYPE_CODE_METHODPTR
24570 @item gdb.TYPE_CODE_METHODPTR
24571 A pointer-to-member-function.
24573 @findex TYPE_CODE_MEMBERPTR
24574 @findex gdb.TYPE_CODE_MEMBERPTR
24575 @item gdb.TYPE_CODE_MEMBERPTR
24576 A pointer-to-member.
24578 @findex TYPE_CODE_REF
24579 @findex gdb.TYPE_CODE_REF
24580 @item gdb.TYPE_CODE_REF
24583 @findex TYPE_CODE_CHAR
24584 @findex gdb.TYPE_CODE_CHAR
24585 @item gdb.TYPE_CODE_CHAR
24588 @findex TYPE_CODE_BOOL
24589 @findex gdb.TYPE_CODE_BOOL
24590 @item gdb.TYPE_CODE_BOOL
24593 @findex TYPE_CODE_COMPLEX
24594 @findex gdb.TYPE_CODE_COMPLEX
24595 @item gdb.TYPE_CODE_COMPLEX
24596 A complex float type.
24598 @findex TYPE_CODE_TYPEDEF
24599 @findex gdb.TYPE_CODE_TYPEDEF
24600 @item gdb.TYPE_CODE_TYPEDEF
24601 A typedef to some other type.
24603 @findex TYPE_CODE_NAMESPACE
24604 @findex gdb.TYPE_CODE_NAMESPACE
24605 @item gdb.TYPE_CODE_NAMESPACE
24606 A C@t{++} namespace.
24608 @findex TYPE_CODE_DECFLOAT
24609 @findex gdb.TYPE_CODE_DECFLOAT
24610 @item gdb.TYPE_CODE_DECFLOAT
24611 A decimal floating point type.
24613 @findex TYPE_CODE_INTERNAL_FUNCTION
24614 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
24615 @item gdb.TYPE_CODE_INTERNAL_FUNCTION
24616 A function internal to @value{GDBN}. This is the type used to represent
24617 convenience functions.
24620 Further support for types is provided in the @code{gdb.types}
24621 Python module (@pxref{gdb.types}).
24623 @node Pretty Printing API
24624 @subsubsection Pretty Printing API
24626 An example output is provided (@pxref{Pretty Printing}).
24628 A pretty-printer is just an object that holds a value and implements a
24629 specific interface, defined here.
24631 @defun pretty_printer.children (self)
24632 @value{GDBN} will call this method on a pretty-printer to compute the
24633 children of the pretty-printer's value.
24635 This method must return an object conforming to the Python iterator
24636 protocol. Each item returned by the iterator must be a tuple holding
24637 two elements. The first element is the ``name'' of the child; the
24638 second element is the child's value. The value can be any Python
24639 object which is convertible to a @value{GDBN} value.
24641 This method is optional. If it does not exist, @value{GDBN} will act
24642 as though the value has no children.
24645 @defun pretty_printer.display_hint (self)
24646 The CLI may call this method and use its result to change the
24647 formatting of a value. The result will also be supplied to an MI
24648 consumer as a @samp{displayhint} attribute of the variable being
24651 This method is optional. If it does exist, this method must return a
24654 Some display hints are predefined by @value{GDBN}:
24658 Indicate that the object being printed is ``array-like''. The CLI
24659 uses this to respect parameters such as @code{set print elements} and
24660 @code{set print array}.
24663 Indicate that the object being printed is ``map-like'', and that the
24664 children of this value can be assumed to alternate between keys and
24668 Indicate that the object being printed is ``string-like''. If the
24669 printer's @code{to_string} method returns a Python string of some
24670 kind, then @value{GDBN} will call its internal language-specific
24671 string-printing function to format the string. For the CLI this means
24672 adding quotation marks, possibly escaping some characters, respecting
24673 @code{set print elements}, and the like.
24677 @defun pretty_printer.to_string (self)
24678 @value{GDBN} will call this method to display the string
24679 representation of the value passed to the object's constructor.
24681 When printing from the CLI, if the @code{to_string} method exists,
24682 then @value{GDBN} will prepend its result to the values returned by
24683 @code{children}. Exactly how this formatting is done is dependent on
24684 the display hint, and may change as more hints are added. Also,
24685 depending on the print settings (@pxref{Print Settings}), the CLI may
24686 print just the result of @code{to_string} in a stack trace, omitting
24687 the result of @code{children}.
24689 If this method returns a string, it is printed verbatim.
24691 Otherwise, if this method returns an instance of @code{gdb.Value},
24692 then @value{GDBN} prints this value. This may result in a call to
24693 another pretty-printer.
24695 If instead the method returns a Python value which is convertible to a
24696 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
24697 the resulting value. Again, this may result in a call to another
24698 pretty-printer. Python scalars (integers, floats, and booleans) and
24699 strings are convertible to @code{gdb.Value}; other types are not.
24701 Finally, if this method returns @code{None} then no further operations
24702 are peformed in this method and nothing is printed.
24704 If the result is not one of these types, an exception is raised.
24707 @value{GDBN} provides a function which can be used to look up the
24708 default pretty-printer for a @code{gdb.Value}:
24710 @findex gdb.default_visualizer
24711 @defun gdb.default_visualizer (value)
24712 This function takes a @code{gdb.Value} object as an argument. If a
24713 pretty-printer for this value exists, then it is returned. If no such
24714 printer exists, then this returns @code{None}.
24717 @node Selecting Pretty-Printers
24718 @subsubsection Selecting Pretty-Printers
24720 The Python list @code{gdb.pretty_printers} contains an array of
24721 functions or callable objects that have been registered via addition
24722 as a pretty-printer. Printers in this list are called @code{global}
24723 printers, they're available when debugging all inferiors.
24724 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
24725 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
24728 Each function on these lists is passed a single @code{gdb.Value}
24729 argument and should return a pretty-printer object conforming to the
24730 interface definition above (@pxref{Pretty Printing API}). If a function
24731 cannot create a pretty-printer for the value, it should return
24734 @value{GDBN} first checks the @code{pretty_printers} attribute of each
24735 @code{gdb.Objfile} in the current program space and iteratively calls
24736 each enabled lookup routine in the list for that @code{gdb.Objfile}
24737 until it receives a pretty-printer object.
24738 If no pretty-printer is found in the objfile lists, @value{GDBN} then
24739 searches the pretty-printer list of the current program space,
24740 calling each enabled function until an object is returned.
24741 After these lists have been exhausted, it tries the global
24742 @code{gdb.pretty_printers} list, again calling each enabled function until an
24743 object is returned.
24745 The order in which the objfiles are searched is not specified. For a
24746 given list, functions are always invoked from the head of the list,
24747 and iterated over sequentially until the end of the list, or a printer
24748 object is returned.
24750 For various reasons a pretty-printer may not work.
24751 For example, the underlying data structure may have changed and
24752 the pretty-printer is out of date.
24754 The consequences of a broken pretty-printer are severe enough that
24755 @value{GDBN} provides support for enabling and disabling individual
24756 printers. For example, if @code{print frame-arguments} is on,
24757 a backtrace can become highly illegible if any argument is printed
24758 with a broken printer.
24760 Pretty-printers are enabled and disabled by attaching an @code{enabled}
24761 attribute to the registered function or callable object. If this attribute
24762 is present and its value is @code{False}, the printer is disabled, otherwise
24763 the printer is enabled.
24765 @node Writing a Pretty-Printer
24766 @subsubsection Writing a Pretty-Printer
24767 @cindex writing a pretty-printer
24769 A pretty-printer consists of two parts: a lookup function to detect
24770 if the type is supported, and the printer itself.
24772 Here is an example showing how a @code{std::string} printer might be
24773 written. @xref{Pretty Printing API}, for details on the API this class
24777 class StdStringPrinter(object):
24778 "Print a std::string"
24780 def __init__(self, val):
24783 def to_string(self):
24784 return self.val['_M_dataplus']['_M_p']
24786 def display_hint(self):
24790 And here is an example showing how a lookup function for the printer
24791 example above might be written.
24794 def str_lookup_function(val):
24795 lookup_tag = val.type.tag
24796 if lookup_tag == None:
24798 regex = re.compile("^std::basic_string<char,.*>$")
24799 if regex.match(lookup_tag):
24800 return StdStringPrinter(val)
24804 The example lookup function extracts the value's type, and attempts to
24805 match it to a type that it can pretty-print. If it is a type the
24806 printer can pretty-print, it will return a printer object. If not, it
24807 returns @code{None}.
24809 We recommend that you put your core pretty-printers into a Python
24810 package. If your pretty-printers are for use with a library, we
24811 further recommend embedding a version number into the package name.
24812 This practice will enable @value{GDBN} to load multiple versions of
24813 your pretty-printers at the same time, because they will have
24816 You should write auto-loaded code (@pxref{Python Auto-loading}) such that it
24817 can be evaluated multiple times without changing its meaning. An
24818 ideal auto-load file will consist solely of @code{import}s of your
24819 printer modules, followed by a call to a register pretty-printers with
24820 the current objfile.
24822 Taken as a whole, this approach will scale nicely to multiple
24823 inferiors, each potentially using a different library version.
24824 Embedding a version number in the Python package name will ensure that
24825 @value{GDBN} is able to load both sets of printers simultaneously.
24826 Then, because the search for pretty-printers is done by objfile, and
24827 because your auto-loaded code took care to register your library's
24828 printers with a specific objfile, @value{GDBN} will find the correct
24829 printers for the specific version of the library used by each
24832 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
24833 this code might appear in @code{gdb.libstdcxx.v6}:
24836 def register_printers(objfile):
24837 objfile.pretty_printers.append(str_lookup_function)
24841 And then the corresponding contents of the auto-load file would be:
24844 import gdb.libstdcxx.v6
24845 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
24848 The previous example illustrates a basic pretty-printer.
24849 There are a few things that can be improved on.
24850 The printer doesn't have a name, making it hard to identify in a
24851 list of installed printers. The lookup function has a name, but
24852 lookup functions can have arbitrary, even identical, names.
24854 Second, the printer only handles one type, whereas a library typically has
24855 several types. One could install a lookup function for each desired type
24856 in the library, but one could also have a single lookup function recognize
24857 several types. The latter is the conventional way this is handled.
24858 If a pretty-printer can handle multiple data types, then its
24859 @dfn{subprinters} are the printers for the individual data types.
24861 The @code{gdb.printing} module provides a formal way of solving these
24862 problems (@pxref{gdb.printing}).
24863 Here is another example that handles multiple types.
24865 These are the types we are going to pretty-print:
24868 struct foo @{ int a, b; @};
24869 struct bar @{ struct foo x, y; @};
24872 Here are the printers:
24876 """Print a foo object."""
24878 def __init__(self, val):
24881 def to_string(self):
24882 return ("a=<" + str(self.val["a"]) +
24883 "> b=<" + str(self.val["b"]) + ">")
24886 """Print a bar object."""
24888 def __init__(self, val):
24891 def to_string(self):
24892 return ("x=<" + str(self.val["x"]) +
24893 "> y=<" + str(self.val["y"]) + ">")
24896 This example doesn't need a lookup function, that is handled by the
24897 @code{gdb.printing} module. Instead a function is provided to build up
24898 the object that handles the lookup.
24901 import gdb.printing
24903 def build_pretty_printer():
24904 pp = gdb.printing.RegexpCollectionPrettyPrinter(
24906 pp.add_printer('foo', '^foo$', fooPrinter)
24907 pp.add_printer('bar', '^bar$', barPrinter)
24911 And here is the autoload support:
24914 import gdb.printing
24916 gdb.printing.register_pretty_printer(
24917 gdb.current_objfile(),
24918 my_library.build_pretty_printer())
24921 Finally, when this printer is loaded into @value{GDBN}, here is the
24922 corresponding output of @samp{info pretty-printer}:
24925 (gdb) info pretty-printer
24932 @node Type Printing API
24933 @subsubsection Type Printing API
24934 @cindex type printing API for Python
24936 @value{GDBN} provides a way for Python code to customize type display.
24937 This is mainly useful for substituting canonical typedef names for
24940 @cindex type printer
24941 A @dfn{type printer} is just a Python object conforming to a certain
24942 protocol. A simple base class implementing the protocol is provided;
24943 see @ref{gdb.types}. A type printer must supply at least:
24945 @defivar type_printer enabled
24946 A boolean which is True if the printer is enabled, and False
24947 otherwise. This is manipulated by the @code{enable type-printer}
24948 and @code{disable type-printer} commands.
24951 @defivar type_printer name
24952 The name of the type printer. This must be a string. This is used by
24953 the @code{enable type-printer} and @code{disable type-printer}
24957 @defmethod type_printer instantiate (self)
24958 This is called by @value{GDBN} at the start of type-printing. It is
24959 only called if the type printer is enabled. This method must return a
24960 new object that supplies a @code{recognize} method, as described below.
24964 When displaying a type, say via the @code{ptype} command, @value{GDBN}
24965 will compute a list of type recognizers. This is done by iterating
24966 first over the per-objfile type printers (@pxref{Objfiles In Python}),
24967 followed by the per-progspace type printers (@pxref{Progspaces In
24968 Python}), and finally the global type printers.
24970 @value{GDBN} will call the @code{instantiate} method of each enabled
24971 type printer. If this method returns @code{None}, then the result is
24972 ignored; otherwise, it is appended to the list of recognizers.
24974 Then, when @value{GDBN} is going to display a type name, it iterates
24975 over the list of recognizers. For each one, it calls the recognition
24976 function, stopping if the function returns a non-@code{None} value.
24977 The recognition function is defined as:
24979 @defmethod type_recognizer recognize (self, type)
24980 If @var{type} is not recognized, return @code{None}. Otherwise,
24981 return a string which is to be printed as the name of @var{type}.
24982 @var{type} will be an instance of @code{gdb.Type} (@pxref{Types In
24986 @value{GDBN} uses this two-pass approach so that type printers can
24987 efficiently cache information without holding on to it too long. For
24988 example, it can be convenient to look up type information in a type
24989 printer and hold it for a recognizer's lifetime; if a single pass were
24990 done then type printers would have to make use of the event system in
24991 order to avoid holding information that could become stale as the
24994 @node Frame Filter API
24995 @subsubsection Filtering Frames.
24996 @cindex frame filters api
24998 Frame filters are Python objects that manipulate the visibility of a
24999 frame or frames when a backtrace (@pxref{Backtrace}) is printed by
25002 Only commands that print a backtrace, or, in the case of @sc{gdb/mi}
25003 commands (@pxref{GDB/MI}), those that return a collection of frames
25004 are affected. The commands that work with frame filters are:
25006 @code{backtrace} (@pxref{backtrace-command,, The backtrace command}),
25007 @code{-stack-list-frames}
25008 (@pxref{-stack-list-frames,, The -stack-list-frames command}),
25009 @code{-stack-list-variables} (@pxref{-stack-list-variables,, The
25010 -stack-list-variables command}), @code{-stack-list-arguments}
25011 @pxref{-stack-list-arguments,, The -stack-list-arguments command}) and
25012 @code{-stack-list-locals} (@pxref{-stack-list-locals,, The
25013 -stack-list-locals command}).
25015 A frame filter works by taking an iterator as an argument, applying
25016 actions to the contents of that iterator, and returning another
25017 iterator (or, possibly, the same iterator it was provided in the case
25018 where the filter does not perform any operations). Typically, frame
25019 filters utilize tools such as the Python's @code{itertools} module to
25020 work with and create new iterators from the source iterator.
25021 Regardless of how a filter chooses to apply actions, it must not alter
25022 the underlying @value{GDBN} frame or frames, or attempt to alter the
25023 call-stack within @value{GDBN}. This preserves data integrity within
25024 @value{GDBN}. Frame filters are executed on a priority basis and care
25025 should be taken that some frame filters may have been executed before,
25026 and that some frame filters will be executed after.
25028 An important consideration when designing frame filters, and well
25029 worth reflecting upon, is that frame filters should avoid unwinding
25030 the call stack if possible. Some stacks can run very deep, into the
25031 tens of thousands in some cases. To search every frame when a frame
25032 filter executes may be too expensive at that step. The frame filter
25033 cannot know how many frames it has to iterate over, and it may have to
25034 iterate through them all. This ends up duplicating effort as
25035 @value{GDBN} performs this iteration when it prints the frames. If
25036 the filter can defer unwinding frames until frame decorators are
25037 executed, after the last filter has executed, it should. @xref{Frame
25038 Decorator API}, for more information on decorators. Also, there are
25039 examples for both frame decorators and filters in later chapters.
25040 @xref{Writing a Frame Filter}, for more information.
25042 The Python dictionary @code{gdb.frame_filters} contains key/object
25043 pairings that comprise a frame filter. Frame filters in this
25044 dictionary are called @code{global} frame filters, and they are
25045 available when debugging all inferiors. These frame filters must
25046 register with the dictionary directly. In addition to the
25047 @code{global} dictionary, there are other dictionaries that are loaded
25048 with different inferiors via auto-loading (@pxref{Python
25049 Auto-loading}). The two other areas where frame filter dictionaries
25050 can be found are: @code{gdb.Progspace} which contains a
25051 @code{frame_filters} dictionary attribute, and each @code{gdb.Objfile}
25052 object which also contains a @code{frame_filters} dictionary
25055 When a command is executed from @value{GDBN} that is compatible with
25056 frame filters, @value{GDBN} combines the @code{global},
25057 @code{gdb.Progspace} and all @code{gdb.Objfile} dictionaries currently
25058 loaded. All of the @code{gdb.Objfile} dictionaries are combined, as
25059 several frames, and thus several object files, might be in use.
25060 @value{GDBN} then prunes any frame filter whose @code{enabled}
25061 attribute is @code{False}. This pruned list is then sorted according
25062 to the @code{priority} attribute in each filter.
25064 Once the dictionaries are combined, pruned and sorted, @value{GDBN}
25065 creates an iterator which wraps each frame in the call stack in a
25066 @code{FrameDecorator} object, and calls each filter in order. The
25067 output from the previous filter will always be the input to the next
25070 Frame filters have a mandatory interface which each frame filter must
25071 implement, defined here:
25073 @defun FrameFilter.filter (iterator)
25074 @value{GDBN} will call this method on a frame filter when it has
25075 reached the order in the priority list for that filter.
25077 For example, if there are four frame filters:
25088 The order that the frame filters will be called is:
25091 Filter3 -> Filter2 -> Filter1 -> Filter4
25094 Note that the output from @code{Filter3} is passed to the input of
25095 @code{Filter2}, and so on.
25097 This @code{filter} method is passed a Python iterator. This iterator
25098 contains a sequence of frame decorators that wrap each
25099 @code{gdb.Frame}, or a frame decorator that wraps another frame
25100 decorator. The first filter that is executed in the sequence of frame
25101 filters will receive an iterator entirely comprised of default
25102 @code{FrameDecorator} objects. However, after each frame filter is
25103 executed, the previous frame filter may have wrapped some or all of
25104 the frame decorators with their own frame decorator. As frame
25105 decorators must also conform to a mandatory interface, these
25106 decorators can be assumed to act in a uniform manner (@pxref{Frame
25109 This method must return an object conforming to the Python iterator
25110 protocol. Each item in the iterator must be an object conforming to
25111 the frame decorator interface. If a frame filter does not wish to
25112 perform any operations on this iterator, it should return that
25113 iterator untouched.
25115 This method is not optional. If it does not exist, @value{GDBN} will
25116 raise and print an error.
25119 @defvar FrameFilter.name
25120 The @code{name} attribute must be Python string which contains the
25121 name of the filter displayed by @value{GDBN} (@pxref{Frame Filter
25122 Management}). This attribute may contain any combination of letters
25123 or numbers. Care should be taken to ensure that it is unique. This
25124 attribute is mandatory.
25127 @defvar FrameFilter.enabled
25128 The @code{enabled} attribute must be Python boolean. This attribute
25129 indicates to @value{GDBN} whether the frame filter is enabled, and
25130 should be considered when frame filters are executed. If
25131 @code{enabled} is @code{True}, then the frame filter will be executed
25132 when any of the backtrace commands detailed earlier in this chapter
25133 are executed. If @code{enabled} is @code{False}, then the frame
25134 filter will not be executed. This attribute is mandatory.
25137 @defvar FrameFilter.priority
25138 The @code{priority} attribute must be Python integer. This attribute
25139 controls the order of execution in relation to other frame filters.
25140 There are no imposed limits on the range of @code{priority} other than
25141 it must be a valid integer. The higher the @code{priority} attribute,
25142 the sooner the frame filter will be executed in relation to other
25143 frame filters. Although @code{priority} can be negative, it is
25144 recommended practice to assume zero is the lowest priority that a
25145 frame filter can be assigned. Frame filters that have the same
25146 priority are executed in unsorted order in that priority slot. This
25147 attribute is mandatory.
25150 @node Frame Decorator API
25151 @subsubsection Decorating Frames.
25152 @cindex frame decorator api
25154 Frame decorators are sister objects to frame filters (@pxref{Frame
25155 Filter API}). Frame decorators are applied by a frame filter and can
25156 only be used in conjunction with frame filters.
25158 The purpose of a frame decorator is to customize the printed content
25159 of each @code{gdb.Frame} in commands where frame filters are executed.
25160 This concept is called decorating a frame. Frame decorators decorate
25161 a @code{gdb.Frame} with Python code contained within each API call.
25162 This separates the actual data contained in a @code{gdb.Frame} from
25163 the decorated data produced by a frame decorator. This abstraction is
25164 necessary to maintain integrity of the data contained in each
25167 Frame decorators have a mandatory interface, defined below.
25169 @value{GDBN} already contains a frame decorator called
25170 @code{FrameDecorator}. This contains substantial amounts of
25171 boilerplate code to decorate the content of a @code{gdb.Frame}. It is
25172 recommended that other frame decorators inherit and extend this
25173 object, and only to override the methods needed.
25175 @defun FrameDecorator.elided (self)
25177 The @code{elided} method groups frames together in a hierarchical
25178 system. An example would be an interpreter, where multiple low-level
25179 frames make up a single call in the interpreted language. In this
25180 example, the frame filter would elide the low-level frames and present
25181 a single high-level frame, representing the call in the interpreted
25182 language, to the user.
25184 The @code{elided} function must return an iterable and this iterable
25185 must contain the frames that are being elided wrapped in a suitable
25186 frame decorator. If no frames are being elided this function may
25187 return an empty iterable, or @code{None}. Elided frames are indented
25188 from normal frames in a @code{CLI} backtrace, or in the case of
25189 @code{GDB/MI}, are placed in the @code{children} field of the eliding
25192 It is the frame filter's task to also filter out the elided frames from
25193 the source iterator. This will avoid printing the frame twice.
25196 @defun FrameDecorator.function (self)
25198 This method returns the name of the function in the frame that is to
25201 This method must return a Python string describing the function, or
25204 If this function returns @code{None}, @value{GDBN} will not print any
25205 data for this field.
25208 @defun FrameDecorator.address (self)
25210 This method returns the address of the frame that is to be printed.
25212 This method must return a Python numeric integer type of sufficient
25213 size to describe the address of the frame, or @code{None}.
25215 If this function returns a @code{None}, @value{GDBN} will not print
25216 any data for this field.
25219 @defun FrameDecorator.filename (self)
25221 This method returns the filename and path associated with this frame.
25223 This method must return a Python string containing the filename and
25224 the path to the object file backing the frame, or @code{None}.
25226 If this function returns a @code{None}, @value{GDBN} will not print
25227 any data for this field.
25230 @defun FrameDecorator.line (self):
25232 This method returns the line number associated with the current
25233 position within the function addressed by this frame.
25235 This method must return a Python integer type, or @code{None}.
25237 If this function returns a @code{None}, @value{GDBN} will not print
25238 any data for this field.
25241 @defun FrameDecorator.frame_args (self)
25242 @anchor{frame_args}
25244 This method must return an iterable, or @code{None}. Returning an
25245 empty iterable, or @code{None} means frame arguments will not be
25246 printed for this frame. This iterable must contain objects that
25247 implement two methods, described here.
25249 This object must implement a @code{argument} method which takes a
25250 single @code{self} parameter and must return a @code{gdb.Symbol}
25251 (@pxref{Symbols In Python}), or a Python string. The object must also
25252 implement a @code{value} method which takes a single @code{self}
25253 parameter and must return a @code{gdb.Value} (@pxref{Values From
25254 Inferior}), a Python value, or @code{None}. If the @code{value}
25255 method returns @code{None}, and the @code{argument} method returns a
25256 @code{gdb.Symbol}, @value{GDBN} will look-up and print the value of
25257 the @code{gdb.Symbol} automatically.
25262 class SymValueWrapper():
25264 def __init__(self, symbol, value):
25274 class SomeFrameDecorator()
25277 def frame_args(self):
25280 block = self.inferior_frame.block()
25284 # Iterate over all symbols in a block. Only add
25285 # symbols that are arguments.
25287 if not sym.is_argument:
25289 args.append(SymValueWrapper(sym,None))
25291 # Add example synthetic argument.
25292 args.append(SymValueWrapper(``foo'', 42))
25298 @defun FrameDecorator.frame_locals (self)
25300 This method must return an iterable or @code{None}. Returning an
25301 empty iterable, or @code{None} means frame local arguments will not be
25302 printed for this frame.
25304 The object interface, the description of the various strategies for
25305 reading frame locals, and the example are largely similar to those
25306 described in the @code{frame_args} function, (@pxref{frame_args,,The
25307 frame filter frame_args function}). Below is a modified example:
25310 class SomeFrameDecorator()
25313 def frame_locals(self):
25316 block = self.inferior_frame.block()
25320 # Iterate over all symbols in a block. Add all
25321 # symbols, except arguments.
25323 if sym.is_argument:
25325 vars.append(SymValueWrapper(sym,None))
25327 # Add an example of a synthetic local variable.
25328 vars.append(SymValueWrapper(``bar'', 99))
25334 @defun FrameDecorator.inferior_frame (self):
25336 This method must return the underlying @code{gdb.Frame} that this
25337 frame decorator is decorating. @value{GDBN} requires the underlying
25338 frame for internal frame information to determine how to print certain
25339 values when printing a frame.
25342 @node Writing a Frame Filter
25343 @subsubsection Writing a Frame Filter
25344 @cindex writing a frame filter
25346 There are three basic elements that a frame filter must implement: it
25347 must correctly implement the documented interface (@pxref{Frame Filter
25348 API}), it must register itself with @value{GDBN}, and finally, it must
25349 decide if it is to work on the data provided by @value{GDBN}. In all
25350 cases, whether it works on the iterator or not, each frame filter must
25351 return an iterator. A bare-bones frame filter follows the pattern in
25352 the following example.
25357 class FrameFilter():
25359 def __init__(self):
25360 # Frame filter attribute creation.
25362 # 'name' is the name of the filter that GDB will display.
25364 # 'priority' is the priority of the filter relative to other
25367 # 'enabled' is a boolean that indicates whether this filter is
25368 # enabled and should be executed.
25371 self.priority = 100
25372 self.enabled = True
25374 # Register this frame filter with the global frame_filters
25376 gdb.frame_filters[self.name] = self
25378 def filter(self, frame_iter):
25379 # Just return the iterator.
25383 The frame filter in the example above implements the three
25384 requirements for all frame filters. It implements the API, self
25385 registers, and makes a decision on the iterator (in this case, it just
25386 returns the iterator untouched).
25388 The first step is attribute creation and assignment, and as shown in
25389 the comments the filter assigns the following attributes: @code{name},
25390 @code{priority} and whether the filter should be enabled with the
25391 @code{enabled} attribute.
25393 The second step is registering the frame filter with the dictionary or
25394 dictionaries that the frame filter has interest in. As shown in the
25395 comments, this filter just registers itself with the global dictionary
25396 @code{gdb.frame_filters}. As noted earlier, @code{gdb.frame_filters}
25397 is a dictionary that is initialized in the @code{gdb} module when
25398 @value{GDBN} starts. What dictionary a filter registers with is an
25399 important consideration. Generally, if a filter is specific to a set
25400 of code, it should be registered either in the @code{objfile} or
25401 @code{progspace} dictionaries as they are specific to the program
25402 currently loaded in @value{GDBN}. The global dictionary is always
25403 present in @value{GDBN} and is never unloaded. Any filters registered
25404 with the global dictionary will exist until @value{GDBN} exits. To
25405 avoid filters that may conflict, it is generally better to register
25406 frame filters against the dictionaries that more closely align with
25407 the usage of the filter currently in question. @xref{Python
25408 Auto-loading}, for further information on auto-loading Python scripts.
25410 @value{GDBN} takes a hands-off approach to frame filter registration,
25411 therefore it is the frame filter's responsibility to ensure
25412 registration has occurred, and that any exceptions are handled
25413 appropriately. In particular, you may wish to handle exceptions
25414 relating to Python dictionary key uniqueness. It is mandatory that
25415 the dictionary key is the same as frame filter's @code{name}
25416 attribute. When a user manages frame filters (@pxref{Frame Filter
25417 Management}), the names @value{GDBN} will display are those contained
25418 in the @code{name} attribute.
25420 The final step of this example is the implementation of the
25421 @code{filter} method. As shown in the example comments, we define the
25422 @code{filter} method and note that the method must take an iterator,
25423 and also must return an iterator. In this bare-bones example, the
25424 frame filter is not very useful as it just returns the iterator
25425 untouched. However this is a valid operation for frame filters that
25426 have the @code{enabled} attribute set, but decide not to operate on
25429 In the next example, the frame filter operates on all frames and
25430 utilizes a frame decorator to perform some work on the frames.
25431 @xref{Frame Decorator API}, for further information on the frame
25432 decorator interface.
25434 This example works on inlined frames. It highlights frames which are
25435 inlined by tagging them with an ``[inlined]'' tag. By applying a
25436 frame decorator to all frames with the Python @code{itertools imap}
25437 method, the example defers actions to the frame decorator. Frame
25438 decorators are only processed when @value{GDBN} prints the backtrace.
25440 This introduces a new decision making topic: whether to perform
25441 decision making operations at the filtering step, or at the printing
25442 step. In this example's approach, it does not perform any filtering
25443 decisions at the filtering step beyond mapping a frame decorator to
25444 each frame. This allows the actual decision making to be performed
25445 when each frame is printed. This is an important consideration, and
25446 well worth reflecting upon when designing a frame filter. An issue
25447 that frame filters should avoid is unwinding the stack if possible.
25448 Some stacks can run very deep, into the tens of thousands in some
25449 cases. To search every frame to determine if it is inlined ahead of
25450 time may be too expensive at the filtering step. The frame filter
25451 cannot know how many frames it has to iterate over, and it would have
25452 to iterate through them all. This ends up duplicating effort as
25453 @value{GDBN} performs this iteration when it prints the frames.
25455 In this example decision making can be deferred to the printing step.
25456 As each frame is printed, the frame decorator can examine each frame
25457 in turn when @value{GDBN} iterates. From a performance viewpoint,
25458 this is the most appropriate decision to make as it avoids duplicating
25459 the effort that the printing step would undertake anyway. Also, if
25460 there are many frame filters unwinding the stack during filtering, it
25461 can substantially delay the printing of the backtrace which will
25462 result in large memory usage, and a poor user experience.
25465 class InlineFilter():
25467 def __init__(self):
25468 self.name = "InlinedFrameFilter"
25469 self.priority = 100
25470 self.enabled = True
25471 gdb.frame_filters[self.name] = self
25473 def filter(self, frame_iter):
25474 frame_iter = itertools.imap(InlinedFrameDecorator,
25479 This frame filter is somewhat similar to the earlier example, except
25480 that the @code{filter} method applies a frame decorator object called
25481 @code{InlinedFrameDecorator} to each element in the iterator. The
25482 @code{imap} Python method is light-weight. It does not proactively
25483 iterate over the iterator, but rather creates a new iterator which
25484 wraps the existing one.
25486 Below is the frame decorator for this example.
25489 class InlinedFrameDecorator(FrameDecorator):
25491 def __init__(self, fobj):
25492 super(InlinedFrameDecorator, self).__init__(fobj)
25494 def function(self):
25495 frame = fobj.inferior_frame()
25496 name = str(frame.name())
25498 if frame.type() == gdb.INLINE_FRAME:
25499 name = name + " [inlined]"
25504 This frame decorator only defines and overrides the @code{function}
25505 method. It lets the supplied @code{FrameDecorator}, which is shipped
25506 with @value{GDBN}, perform the other work associated with printing
25509 The combination of these two objects create this output from a
25513 #0 0x004004e0 in bar () at inline.c:11
25514 #1 0x00400566 in max [inlined] (b=6, a=12) at inline.c:21
25515 #2 0x00400566 in main () at inline.c:31
25518 So in the case of this example, a frame decorator is applied to all
25519 frames, regardless of whether they may be inlined or not. As
25520 @value{GDBN} iterates over the iterator produced by the frame filters,
25521 @value{GDBN} executes each frame decorator which then makes a decision
25522 on what to print in the @code{function} callback. Using a strategy
25523 like this is a way to defer decisions on the frame content to printing
25526 @subheading Eliding Frames
25528 It might be that the above example is not desirable for representing
25529 inlined frames, and a hierarchical approach may be preferred. If we
25530 want to hierarchically represent frames, the @code{elided} frame
25531 decorator interface might be preferable.
25533 This example approaches the issue with the @code{elided} method. This
25534 example is quite long, but very simplistic. It is out-of-scope for
25535 this section to write a complete example that comprehensively covers
25536 all approaches of finding and printing inlined frames. However, this
25537 example illustrates the approach an author might use.
25539 This example comprises of three sections.
25542 class InlineFrameFilter():
25544 def __init__(self):
25545 self.name = "InlinedFrameFilter"
25546 self.priority = 100
25547 self.enabled = True
25548 gdb.frame_filters[self.name] = self
25550 def filter(self, frame_iter):
25551 return ElidingInlineIterator(frame_iter)
25554 This frame filter is very similar to the other examples. The only
25555 difference is this frame filter is wrapping the iterator provided to
25556 it (@code{frame_iter}) with a custom iterator called
25557 @code{ElidingInlineIterator}. This again defers actions to when
25558 @value{GDBN} prints the backtrace, as the iterator is not traversed
25561 The iterator for this example is as follows. It is in this section of
25562 the example where decisions are made on the content of the backtrace.
25565 class ElidingInlineIterator:
25566 def __init__(self, ii):
25567 self.input_iterator = ii
25569 def __iter__(self):
25573 frame = next(self.input_iterator)
25575 if frame.inferior_frame().type() != gdb.INLINE_FRAME:
25579 eliding_frame = next(self.input_iterator)
25580 except StopIteration:
25582 return ElidingFrameDecorator(eliding_frame, [frame])
25585 This iterator implements the Python iterator protocol. When the
25586 @code{next} function is called (when @value{GDBN} prints each frame),
25587 the iterator checks if this frame decorator, @code{frame}, is wrapping
25588 an inlined frame. If it is not, it returns the existing frame decorator
25589 untouched. If it is wrapping an inlined frame, it assumes that the
25590 inlined frame was contained within the next oldest frame,
25591 @code{eliding_frame}, which it fetches. It then creates and returns a
25592 frame decorator, @code{ElidingFrameDecorator}, which contains both the
25593 elided frame, and the eliding frame.
25596 class ElidingInlineDecorator(FrameDecorator):
25598 def __init__(self, frame, elided_frames):
25599 super(ElidingInlineDecorator, self).__init__(frame)
25601 self.elided_frames = elided_frames
25604 return iter(self.elided_frames)
25607 This frame decorator overrides one function and returns the inlined
25608 frame in the @code{elided} method. As before it lets
25609 @code{FrameDecorator} do the rest of the work involved in printing
25610 this frame. This produces the following output.
25613 #0 0x004004e0 in bar () at inline.c:11
25614 #2 0x00400529 in main () at inline.c:25
25615 #1 0x00400529 in max (b=6, a=12) at inline.c:15
25618 In that output, @code{max} which has been inlined into @code{main} is
25619 printed hierarchically. Another approach would be to combine the
25620 @code{function} method, and the @code{elided} method to both print a
25621 marker in the inlined frame, and also show the hierarchical
25624 @node Inferiors In Python
25625 @subsubsection Inferiors In Python
25626 @cindex inferiors in Python
25628 @findex gdb.Inferior
25629 Programs which are being run under @value{GDBN} are called inferiors
25630 (@pxref{Inferiors and Programs}). Python scripts can access
25631 information about and manipulate inferiors controlled by @value{GDBN}
25632 via objects of the @code{gdb.Inferior} class.
25634 The following inferior-related functions are available in the @code{gdb}
25637 @defun gdb.inferiors ()
25638 Return a tuple containing all inferior objects.
25641 @defun gdb.selected_inferior ()
25642 Return an object representing the current inferior.
25645 A @code{gdb.Inferior} object has the following attributes:
25647 @defvar Inferior.num
25648 ID of inferior, as assigned by GDB.
25651 @defvar Inferior.pid
25652 Process ID of the inferior, as assigned by the underlying operating
25656 @defvar Inferior.was_attached
25657 Boolean signaling whether the inferior was created using `attach', or
25658 started by @value{GDBN} itself.
25661 A @code{gdb.Inferior} object has the following methods:
25663 @defun Inferior.is_valid ()
25664 Returns @code{True} if the @code{gdb.Inferior} object is valid,
25665 @code{False} if not. A @code{gdb.Inferior} object will become invalid
25666 if the inferior no longer exists within @value{GDBN}. All other
25667 @code{gdb.Inferior} methods will throw an exception if it is invalid
25668 at the time the method is called.
25671 @defun Inferior.threads ()
25672 This method returns a tuple holding all the threads which are valid
25673 when it is called. If there are no valid threads, the method will
25674 return an empty tuple.
25677 @findex Inferior.read_memory
25678 @defun Inferior.read_memory (address, length)
25679 Read @var{length} bytes of memory from the inferior, starting at
25680 @var{address}. Returns a buffer object, which behaves much like an array
25681 or a string. It can be modified and given to the
25682 @code{Inferior.write_memory} function. In @code{Python} 3, the return
25683 value is a @code{memoryview} object.
25686 @findex Inferior.write_memory
25687 @defun Inferior.write_memory (address, buffer @r{[}, length@r{]})
25688 Write the contents of @var{buffer} to the inferior, starting at
25689 @var{address}. The @var{buffer} parameter must be a Python object
25690 which supports the buffer protocol, i.e., a string, an array or the
25691 object returned from @code{Inferior.read_memory}. If given, @var{length}
25692 determines the number of bytes from @var{buffer} to be written.
25695 @findex gdb.search_memory
25696 @defun Inferior.search_memory (address, length, pattern)
25697 Search a region of the inferior memory starting at @var{address} with
25698 the given @var{length} using the search pattern supplied in
25699 @var{pattern}. The @var{pattern} parameter must be a Python object
25700 which supports the buffer protocol, i.e., a string, an array or the
25701 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
25702 containing the address where the pattern was found, or @code{None} if
25703 the pattern could not be found.
25706 @node Events In Python
25707 @subsubsection Events In Python
25708 @cindex inferior events in Python
25710 @value{GDBN} provides a general event facility so that Python code can be
25711 notified of various state changes, particularly changes that occur in
25714 An @dfn{event} is just an object that describes some state change. The
25715 type of the object and its attributes will vary depending on the details
25716 of the change. All the existing events are described below.
25718 In order to be notified of an event, you must register an event handler
25719 with an @dfn{event registry}. An event registry is an object in the
25720 @code{gdb.events} module which dispatches particular events. A registry
25721 provides methods to register and unregister event handlers:
25723 @defun EventRegistry.connect (object)
25724 Add the given callable @var{object} to the registry. This object will be
25725 called when an event corresponding to this registry occurs.
25728 @defun EventRegistry.disconnect (object)
25729 Remove the given @var{object} from the registry. Once removed, the object
25730 will no longer receive notifications of events.
25733 Here is an example:
25736 def exit_handler (event):
25737 print "event type: exit"
25738 print "exit code: %d" % (event.exit_code)
25740 gdb.events.exited.connect (exit_handler)
25743 In the above example we connect our handler @code{exit_handler} to the
25744 registry @code{events.exited}. Once connected, @code{exit_handler} gets
25745 called when the inferior exits. The argument @dfn{event} in this example is
25746 of type @code{gdb.ExitedEvent}. As you can see in the example the
25747 @code{ExitedEvent} object has an attribute which indicates the exit code of
25750 The following is a listing of the event registries that are available and
25751 details of the events they emit:
25756 Emits @code{gdb.ThreadEvent}.
25758 Some events can be thread specific when @value{GDBN} is running in non-stop
25759 mode. When represented in Python, these events all extend
25760 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
25761 events which are emitted by this or other modules might extend this event.
25762 Examples of these events are @code{gdb.BreakpointEvent} and
25763 @code{gdb.ContinueEvent}.
25765 @defvar ThreadEvent.inferior_thread
25766 In non-stop mode this attribute will be set to the specific thread which was
25767 involved in the emitted event. Otherwise, it will be set to @code{None}.
25770 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
25772 This event indicates that the inferior has been continued after a stop. For
25773 inherited attribute refer to @code{gdb.ThreadEvent} above.
25775 @item events.exited
25776 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
25777 @code{events.ExitedEvent} has two attributes:
25778 @defvar ExitedEvent.exit_code
25779 An integer representing the exit code, if available, which the inferior
25780 has returned. (The exit code could be unavailable if, for example,
25781 @value{GDBN} detaches from the inferior.) If the exit code is unavailable,
25782 the attribute does not exist.
25784 @defvar ExitedEvent inferior
25785 A reference to the inferior which triggered the @code{exited} event.
25789 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
25791 Indicates that the inferior has stopped. All events emitted by this registry
25792 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
25793 will indicate the stopped thread when @value{GDBN} is running in non-stop
25794 mode. Refer to @code{gdb.ThreadEvent} above for more details.
25796 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
25798 This event indicates that the inferior or one of its threads has received as
25799 signal. @code{gdb.SignalEvent} has the following attributes:
25801 @defvar SignalEvent.stop_signal
25802 A string representing the signal received by the inferior. A list of possible
25803 signal values can be obtained by running the command @code{info signals} in
25804 the @value{GDBN} command prompt.
25807 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
25809 @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have
25810 been hit, and has the following attributes:
25812 @defvar BreakpointEvent.breakpoints
25813 A sequence containing references to all the breakpoints (type
25814 @code{gdb.Breakpoint}) that were hit.
25815 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
25817 @defvar BreakpointEvent.breakpoint
25818 A reference to the first breakpoint that was hit.
25819 This function is maintained for backward compatibility and is now deprecated
25820 in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute.
25823 @item events.new_objfile
25824 Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has
25825 been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute:
25827 @defvar NewObjFileEvent.new_objfile
25828 A reference to the object file (@code{gdb.Objfile}) which has been loaded.
25829 @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object.
25834 @node Threads In Python
25835 @subsubsection Threads In Python
25836 @cindex threads in python
25838 @findex gdb.InferiorThread
25839 Python scripts can access information about, and manipulate inferior threads
25840 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
25842 The following thread-related functions are available in the @code{gdb}
25845 @findex gdb.selected_thread
25846 @defun gdb.selected_thread ()
25847 This function returns the thread object for the selected thread. If there
25848 is no selected thread, this will return @code{None}.
25851 A @code{gdb.InferiorThread} object has the following attributes:
25853 @defvar InferiorThread.name
25854 The name of the thread. If the user specified a name using
25855 @code{thread name}, then this returns that name. Otherwise, if an
25856 OS-supplied name is available, then it is returned. Otherwise, this
25857 returns @code{None}.
25859 This attribute can be assigned to. The new value must be a string
25860 object, which sets the new name, or @code{None}, which removes any
25861 user-specified thread name.
25864 @defvar InferiorThread.num
25865 ID of the thread, as assigned by GDB.
25868 @defvar InferiorThread.ptid
25869 ID of the thread, as assigned by the operating system. This attribute is a
25870 tuple containing three integers. The first is the Process ID (PID); the second
25871 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
25872 Either the LWPID or TID may be 0, which indicates that the operating system
25873 does not use that identifier.
25876 A @code{gdb.InferiorThread} object has the following methods:
25878 @defun InferiorThread.is_valid ()
25879 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
25880 @code{False} if not. A @code{gdb.InferiorThread} object will become
25881 invalid if the thread exits, or the inferior that the thread belongs
25882 is deleted. All other @code{gdb.InferiorThread} methods will throw an
25883 exception if it is invalid at the time the method is called.
25886 @defun InferiorThread.switch ()
25887 This changes @value{GDBN}'s currently selected thread to the one represented
25891 @defun InferiorThread.is_stopped ()
25892 Return a Boolean indicating whether the thread is stopped.
25895 @defun InferiorThread.is_running ()
25896 Return a Boolean indicating whether the thread is running.
25899 @defun InferiorThread.is_exited ()
25900 Return a Boolean indicating whether the thread is exited.
25903 @node Commands In Python
25904 @subsubsection Commands In Python
25906 @cindex commands in python
25907 @cindex python commands
25908 You can implement new @value{GDBN} CLI commands in Python. A CLI
25909 command is implemented using an instance of the @code{gdb.Command}
25910 class, most commonly using a subclass.
25912 @defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]})
25913 The object initializer for @code{Command} registers the new command
25914 with @value{GDBN}. This initializer is normally invoked from the
25915 subclass' own @code{__init__} method.
25917 @var{name} is the name of the command. If @var{name} consists of
25918 multiple words, then the initial words are looked for as prefix
25919 commands. In this case, if one of the prefix commands does not exist,
25920 an exception is raised.
25922 There is no support for multi-line commands.
25924 @var{command_class} should be one of the @samp{COMMAND_} constants
25925 defined below. This argument tells @value{GDBN} how to categorize the
25926 new command in the help system.
25928 @var{completer_class} is an optional argument. If given, it should be
25929 one of the @samp{COMPLETE_} constants defined below. This argument
25930 tells @value{GDBN} how to perform completion for this command. If not
25931 given, @value{GDBN} will attempt to complete using the object's
25932 @code{complete} method (see below); if no such method is found, an
25933 error will occur when completion is attempted.
25935 @var{prefix} is an optional argument. If @code{True}, then the new
25936 command is a prefix command; sub-commands of this command may be
25939 The help text for the new command is taken from the Python
25940 documentation string for the command's class, if there is one. If no
25941 documentation string is provided, the default value ``This command is
25942 not documented.'' is used.
25945 @cindex don't repeat Python command
25946 @defun Command.dont_repeat ()
25947 By default, a @value{GDBN} command is repeated when the user enters a
25948 blank line at the command prompt. A command can suppress this
25949 behavior by invoking the @code{dont_repeat} method. This is similar
25950 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
25953 @defun Command.invoke (argument, from_tty)
25954 This method is called by @value{GDBN} when this command is invoked.
25956 @var{argument} is a string. It is the argument to the command, after
25957 leading and trailing whitespace has been stripped.
25959 @var{from_tty} is a boolean argument. When true, this means that the
25960 command was entered by the user at the terminal; when false it means
25961 that the command came from elsewhere.
25963 If this method throws an exception, it is turned into a @value{GDBN}
25964 @code{error} call. Otherwise, the return value is ignored.
25966 @findex gdb.string_to_argv
25967 To break @var{argument} up into an argv-like string use
25968 @code{gdb.string_to_argv}. This function behaves identically to
25969 @value{GDBN}'s internal argument lexer @code{buildargv}.
25970 It is recommended to use this for consistency.
25971 Arguments are separated by spaces and may be quoted.
25975 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
25976 ['1', '2 "3', '4 "5', "6 '7"]
25981 @cindex completion of Python commands
25982 @defun Command.complete (text, word)
25983 This method is called by @value{GDBN} when the user attempts
25984 completion on this command. All forms of completion are handled by
25985 this method, that is, the @key{TAB} and @key{M-?} key bindings
25986 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
25989 The arguments @var{text} and @var{word} are both strings. @var{text}
25990 holds the complete command line up to the cursor's location.
25991 @var{word} holds the last word of the command line; this is computed
25992 using a word-breaking heuristic.
25994 The @code{complete} method can return several values:
25997 If the return value is a sequence, the contents of the sequence are
25998 used as the completions. It is up to @code{complete} to ensure that the
25999 contents actually do complete the word. A zero-length sequence is
26000 allowed, it means that there were no completions available. Only
26001 string elements of the sequence are used; other elements in the
26002 sequence are ignored.
26005 If the return value is one of the @samp{COMPLETE_} constants defined
26006 below, then the corresponding @value{GDBN}-internal completion
26007 function is invoked, and its result is used.
26010 All other results are treated as though there were no available
26015 When a new command is registered, it must be declared as a member of
26016 some general class of commands. This is used to classify top-level
26017 commands in the on-line help system; note that prefix commands are not
26018 listed under their own category but rather that of their top-level
26019 command. The available classifications are represented by constants
26020 defined in the @code{gdb} module:
26023 @findex COMMAND_NONE
26024 @findex gdb.COMMAND_NONE
26025 @item gdb.COMMAND_NONE
26026 The command does not belong to any particular class. A command in
26027 this category will not be displayed in any of the help categories.
26029 @findex COMMAND_RUNNING
26030 @findex gdb.COMMAND_RUNNING
26031 @item gdb.COMMAND_RUNNING
26032 The command is related to running the inferior. For example,
26033 @code{start}, @code{step}, and @code{continue} are in this category.
26034 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
26035 commands in this category.
26037 @findex COMMAND_DATA
26038 @findex gdb.COMMAND_DATA
26039 @item gdb.COMMAND_DATA
26040 The command is related to data or variables. For example,
26041 @code{call}, @code{find}, and @code{print} are in this category. Type
26042 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
26045 @findex COMMAND_STACK
26046 @findex gdb.COMMAND_STACK
26047 @item gdb.COMMAND_STACK
26048 The command has to do with manipulation of the stack. For example,
26049 @code{backtrace}, @code{frame}, and @code{return} are in this
26050 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
26051 list of commands in this category.
26053 @findex COMMAND_FILES
26054 @findex gdb.COMMAND_FILES
26055 @item gdb.COMMAND_FILES
26056 This class is used for file-related commands. For example,
26057 @code{file}, @code{list} and @code{section} are in this category.
26058 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
26059 commands in this category.
26061 @findex COMMAND_SUPPORT
26062 @findex gdb.COMMAND_SUPPORT
26063 @item gdb.COMMAND_SUPPORT
26064 This should be used for ``support facilities'', generally meaning
26065 things that are useful to the user when interacting with @value{GDBN},
26066 but not related to the state of the inferior. For example,
26067 @code{help}, @code{make}, and @code{shell} are in this category. Type
26068 @kbd{help support} at the @value{GDBN} prompt to see a list of
26069 commands in this category.
26071 @findex COMMAND_STATUS
26072 @findex gdb.COMMAND_STATUS
26073 @item gdb.COMMAND_STATUS
26074 The command is an @samp{info}-related command, that is, related to the
26075 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
26076 and @code{show} are in this category. Type @kbd{help status} at the
26077 @value{GDBN} prompt to see a list of commands in this category.
26079 @findex COMMAND_BREAKPOINTS
26080 @findex gdb.COMMAND_BREAKPOINTS
26081 @item gdb.COMMAND_BREAKPOINTS
26082 The command has to do with breakpoints. For example, @code{break},
26083 @code{clear}, and @code{delete} are in this category. Type @kbd{help
26084 breakpoints} at the @value{GDBN} prompt to see a list of commands in
26087 @findex COMMAND_TRACEPOINTS
26088 @findex gdb.COMMAND_TRACEPOINTS
26089 @item gdb.COMMAND_TRACEPOINTS
26090 The command has to do with tracepoints. For example, @code{trace},
26091 @code{actions}, and @code{tfind} are in this category. Type
26092 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
26093 commands in this category.
26095 @findex COMMAND_USER
26096 @findex gdb.COMMAND_USER
26097 @item gdb.COMMAND_USER
26098 The command is a general purpose command for the user, and typically
26099 does not fit in one of the other categories.
26100 Type @kbd{help user-defined} at the @value{GDBN} prompt to see
26101 a list of commands in this category, as well as the list of gdb macros
26102 (@pxref{Sequences}).
26104 @findex COMMAND_OBSCURE
26105 @findex gdb.COMMAND_OBSCURE
26106 @item gdb.COMMAND_OBSCURE
26107 The command is only used in unusual circumstances, or is not of
26108 general interest to users. For example, @code{checkpoint},
26109 @code{fork}, and @code{stop} are in this category. Type @kbd{help
26110 obscure} at the @value{GDBN} prompt to see a list of commands in this
26113 @findex COMMAND_MAINTENANCE
26114 @findex gdb.COMMAND_MAINTENANCE
26115 @item gdb.COMMAND_MAINTENANCE
26116 The command is only useful to @value{GDBN} maintainers. The
26117 @code{maintenance} and @code{flushregs} commands are in this category.
26118 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
26119 commands in this category.
26122 A new command can use a predefined completion function, either by
26123 specifying it via an argument at initialization, or by returning it
26124 from the @code{complete} method. These predefined completion
26125 constants are all defined in the @code{gdb} module:
26128 @findex COMPLETE_NONE
26129 @findex gdb.COMPLETE_NONE
26130 @item gdb.COMPLETE_NONE
26131 This constant means that no completion should be done.
26133 @findex COMPLETE_FILENAME
26134 @findex gdb.COMPLETE_FILENAME
26135 @item gdb.COMPLETE_FILENAME
26136 This constant means that filename completion should be performed.
26138 @findex COMPLETE_LOCATION
26139 @findex gdb.COMPLETE_LOCATION
26140 @item gdb.COMPLETE_LOCATION
26141 This constant means that location completion should be done.
26142 @xref{Specify Location}.
26144 @findex COMPLETE_COMMAND
26145 @findex gdb.COMPLETE_COMMAND
26146 @item gdb.COMPLETE_COMMAND
26147 This constant means that completion should examine @value{GDBN}
26150 @findex COMPLETE_SYMBOL
26151 @findex gdb.COMPLETE_SYMBOL
26152 @item gdb.COMPLETE_SYMBOL
26153 This constant means that completion should be done using symbol names
26156 @findex COMPLETE_EXPRESSION
26157 @findex gdb.COMPLETE_EXPRESSION
26158 @item gdb.COMPLETE_EXPRESSION
26159 This constant means that completion should be done on expressions.
26160 Often this means completing on symbol names, but some language
26161 parsers also have support for completing on field names.
26164 The following code snippet shows how a trivial CLI command can be
26165 implemented in Python:
26168 class HelloWorld (gdb.Command):
26169 """Greet the whole world."""
26171 def __init__ (self):
26172 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
26174 def invoke (self, arg, from_tty):
26175 print "Hello, World!"
26180 The last line instantiates the class, and is necessary to trigger the
26181 registration of the command with @value{GDBN}. Depending on how the
26182 Python code is read into @value{GDBN}, you may need to import the
26183 @code{gdb} module explicitly.
26185 @node Parameters In Python
26186 @subsubsection Parameters In Python
26188 @cindex parameters in python
26189 @cindex python parameters
26190 @tindex gdb.Parameter
26192 You can implement new @value{GDBN} parameters using Python. A new
26193 parameter is implemented as an instance of the @code{gdb.Parameter}
26196 Parameters are exposed to the user via the @code{set} and
26197 @code{show} commands. @xref{Help}.
26199 There are many parameters that already exist and can be set in
26200 @value{GDBN}. Two examples are: @code{set follow fork} and
26201 @code{set charset}. Setting these parameters influences certain
26202 behavior in @value{GDBN}. Similarly, you can define parameters that
26203 can be used to influence behavior in custom Python scripts and commands.
26205 @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]})
26206 The object initializer for @code{Parameter} registers the new
26207 parameter with @value{GDBN}. This initializer is normally invoked
26208 from the subclass' own @code{__init__} method.
26210 @var{name} is the name of the new parameter. If @var{name} consists
26211 of multiple words, then the initial words are looked for as prefix
26212 parameters. An example of this can be illustrated with the
26213 @code{set print} set of parameters. If @var{name} is
26214 @code{print foo}, then @code{print} will be searched as the prefix
26215 parameter. In this case the parameter can subsequently be accessed in
26216 @value{GDBN} as @code{set print foo}.
26218 If @var{name} consists of multiple words, and no prefix parameter group
26219 can be found, an exception is raised.
26221 @var{command-class} should be one of the @samp{COMMAND_} constants
26222 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
26223 categorize the new parameter in the help system.
26225 @var{parameter-class} should be one of the @samp{PARAM_} constants
26226 defined below. This argument tells @value{GDBN} the type of the new
26227 parameter; this information is used for input validation and
26230 If @var{parameter-class} is @code{PARAM_ENUM}, then
26231 @var{enum-sequence} must be a sequence of strings. These strings
26232 represent the possible values for the parameter.
26234 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
26235 of a fourth argument will cause an exception to be thrown.
26237 The help text for the new parameter is taken from the Python
26238 documentation string for the parameter's class, if there is one. If
26239 there is no documentation string, a default value is used.
26242 @defvar Parameter.set_doc
26243 If this attribute exists, and is a string, then its value is used as
26244 the help text for this parameter's @code{set} command. The value is
26245 examined when @code{Parameter.__init__} is invoked; subsequent changes
26249 @defvar Parameter.show_doc
26250 If this attribute exists, and is a string, then its value is used as
26251 the help text for this parameter's @code{show} command. The value is
26252 examined when @code{Parameter.__init__} is invoked; subsequent changes
26256 @defvar Parameter.value
26257 The @code{value} attribute holds the underlying value of the
26258 parameter. It can be read and assigned to just as any other
26259 attribute. @value{GDBN} does validation when assignments are made.
26262 There are two methods that should be implemented in any
26263 @code{Parameter} class. These are:
26265 @defun Parameter.get_set_string (self)
26266 @value{GDBN} will call this method when a @var{parameter}'s value has
26267 been changed via the @code{set} API (for example, @kbd{set foo off}).
26268 The @code{value} attribute has already been populated with the new
26269 value and may be used in output. This method must return a string.
26272 @defun Parameter.get_show_string (self, svalue)
26273 @value{GDBN} will call this method when a @var{parameter}'s
26274 @code{show} API has been invoked (for example, @kbd{show foo}). The
26275 argument @code{svalue} receives the string representation of the
26276 current value. This method must return a string.
26279 When a new parameter is defined, its type must be specified. The
26280 available types are represented by constants defined in the @code{gdb}
26284 @findex PARAM_BOOLEAN
26285 @findex gdb.PARAM_BOOLEAN
26286 @item gdb.PARAM_BOOLEAN
26287 The value is a plain boolean. The Python boolean values, @code{True}
26288 and @code{False} are the only valid values.
26290 @findex PARAM_AUTO_BOOLEAN
26291 @findex gdb.PARAM_AUTO_BOOLEAN
26292 @item gdb.PARAM_AUTO_BOOLEAN
26293 The value has three possible states: true, false, and @samp{auto}. In
26294 Python, true and false are represented using boolean constants, and
26295 @samp{auto} is represented using @code{None}.
26297 @findex PARAM_UINTEGER
26298 @findex gdb.PARAM_UINTEGER
26299 @item gdb.PARAM_UINTEGER
26300 The value is an unsigned integer. The value of 0 should be
26301 interpreted to mean ``unlimited''.
26303 @findex PARAM_INTEGER
26304 @findex gdb.PARAM_INTEGER
26305 @item gdb.PARAM_INTEGER
26306 The value is a signed integer. The value of 0 should be interpreted
26307 to mean ``unlimited''.
26309 @findex PARAM_STRING
26310 @findex gdb.PARAM_STRING
26311 @item gdb.PARAM_STRING
26312 The value is a string. When the user modifies the string, any escape
26313 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
26314 translated into corresponding characters and encoded into the current
26317 @findex PARAM_STRING_NOESCAPE
26318 @findex gdb.PARAM_STRING_NOESCAPE
26319 @item gdb.PARAM_STRING_NOESCAPE
26320 The value is a string. When the user modifies the string, escapes are
26321 passed through untranslated.
26323 @findex PARAM_OPTIONAL_FILENAME
26324 @findex gdb.PARAM_OPTIONAL_FILENAME
26325 @item gdb.PARAM_OPTIONAL_FILENAME
26326 The value is a either a filename (a string), or @code{None}.
26328 @findex PARAM_FILENAME
26329 @findex gdb.PARAM_FILENAME
26330 @item gdb.PARAM_FILENAME
26331 The value is a filename. This is just like
26332 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
26334 @findex PARAM_ZINTEGER
26335 @findex gdb.PARAM_ZINTEGER
26336 @item gdb.PARAM_ZINTEGER
26337 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
26338 is interpreted as itself.
26341 @findex gdb.PARAM_ENUM
26342 @item gdb.PARAM_ENUM
26343 The value is a string, which must be one of a collection string
26344 constants provided when the parameter is created.
26347 @node Functions In Python
26348 @subsubsection Writing new convenience functions
26350 @cindex writing convenience functions
26351 @cindex convenience functions in python
26352 @cindex python convenience functions
26353 @tindex gdb.Function
26355 You can implement new convenience functions (@pxref{Convenience Vars})
26356 in Python. A convenience function is an instance of a subclass of the
26357 class @code{gdb.Function}.
26359 @defun Function.__init__ (name)
26360 The initializer for @code{Function} registers the new function with
26361 @value{GDBN}. The argument @var{name} is the name of the function,
26362 a string. The function will be visible to the user as a convenience
26363 variable of type @code{internal function}, whose name is the same as
26364 the given @var{name}.
26366 The documentation for the new function is taken from the documentation
26367 string for the new class.
26370 @defun Function.invoke (@var{*args})
26371 When a convenience function is evaluated, its arguments are converted
26372 to instances of @code{gdb.Value}, and then the function's
26373 @code{invoke} method is called. Note that @value{GDBN} does not
26374 predetermine the arity of convenience functions. Instead, all
26375 available arguments are passed to @code{invoke}, following the
26376 standard Python calling convention. In particular, a convenience
26377 function can have default values for parameters without ill effect.
26379 The return value of this method is used as its value in the enclosing
26380 expression. If an ordinary Python value is returned, it is converted
26381 to a @code{gdb.Value} following the usual rules.
26384 The following code snippet shows how a trivial convenience function can
26385 be implemented in Python:
26388 class Greet (gdb.Function):
26389 """Return string to greet someone.
26390 Takes a name as argument."""
26392 def __init__ (self):
26393 super (Greet, self).__init__ ("greet")
26395 def invoke (self, name):
26396 return "Hello, %s!" % name.string ()
26401 The last line instantiates the class, and is necessary to trigger the
26402 registration of the function with @value{GDBN}. Depending on how the
26403 Python code is read into @value{GDBN}, you may need to import the
26404 @code{gdb} module explicitly.
26406 Now you can use the function in an expression:
26409 (gdb) print $greet("Bob")
26413 @node Progspaces In Python
26414 @subsubsection Program Spaces In Python
26416 @cindex progspaces in python
26417 @tindex gdb.Progspace
26419 A program space, or @dfn{progspace}, represents a symbolic view
26420 of an address space.
26421 It consists of all of the objfiles of the program.
26422 @xref{Objfiles In Python}.
26423 @xref{Inferiors and Programs, program spaces}, for more details
26424 about program spaces.
26426 The following progspace-related functions are available in the
26429 @findex gdb.current_progspace
26430 @defun gdb.current_progspace ()
26431 This function returns the program space of the currently selected inferior.
26432 @xref{Inferiors and Programs}.
26435 @findex gdb.progspaces
26436 @defun gdb.progspaces ()
26437 Return a sequence of all the progspaces currently known to @value{GDBN}.
26440 Each progspace is represented by an instance of the @code{gdb.Progspace}
26443 @defvar Progspace.filename
26444 The file name of the progspace as a string.
26447 @defvar Progspace.pretty_printers
26448 The @code{pretty_printers} attribute is a list of functions. It is
26449 used to look up pretty-printers. A @code{Value} is passed to each
26450 function in order; if the function returns @code{None}, then the
26451 search continues. Otherwise, the return value should be an object
26452 which is used to format the value. @xref{Pretty Printing API}, for more
26456 @defvar Progspace.type_printers
26457 The @code{type_printers} attribute is a list of type printer objects.
26458 @xref{Type Printing API}, for more information.
26461 @defvar Progspace.frame_filters
26462 The @code{frame_filters} attribute is a dictionary of frame filter
26463 objects. @xref{Frame Filter API}, for more information.
26466 @node Objfiles In Python
26467 @subsubsection Objfiles In Python
26469 @cindex objfiles in python
26470 @tindex gdb.Objfile
26472 @value{GDBN} loads symbols for an inferior from various
26473 symbol-containing files (@pxref{Files}). These include the primary
26474 executable file, any shared libraries used by the inferior, and any
26475 separate debug info files (@pxref{Separate Debug Files}).
26476 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
26478 The following objfile-related functions are available in the
26481 @findex gdb.current_objfile
26482 @defun gdb.current_objfile ()
26483 When auto-loading a Python script (@pxref{Python Auto-loading}), @value{GDBN}
26484 sets the ``current objfile'' to the corresponding objfile. This
26485 function returns the current objfile. If there is no current objfile,
26486 this function returns @code{None}.
26489 @findex gdb.objfiles
26490 @defun gdb.objfiles ()
26491 Return a sequence of all the objfiles current known to @value{GDBN}.
26492 @xref{Objfiles In Python}.
26495 Each objfile is represented by an instance of the @code{gdb.Objfile}
26498 @defvar Objfile.filename
26499 The file name of the objfile as a string.
26502 @defvar Objfile.pretty_printers
26503 The @code{pretty_printers} attribute is a list of functions. It is
26504 used to look up pretty-printers. A @code{Value} is passed to each
26505 function in order; if the function returns @code{None}, then the
26506 search continues. Otherwise, the return value should be an object
26507 which is used to format the value. @xref{Pretty Printing API}, for more
26511 @defvar Objfile.type_printers
26512 The @code{type_printers} attribute is a list of type printer objects.
26513 @xref{Type Printing API}, for more information.
26516 @defvar Objfile.frame_filters
26517 The @code{frame_filters} attribute is a dictionary of frame filter
26518 objects. @xref{Frame Filter API}, for more information.
26521 A @code{gdb.Objfile} object has the following methods:
26523 @defun Objfile.is_valid ()
26524 Returns @code{True} if the @code{gdb.Objfile} object is valid,
26525 @code{False} if not. A @code{gdb.Objfile} object can become invalid
26526 if the object file it refers to is not loaded in @value{GDBN} any
26527 longer. All other @code{gdb.Objfile} methods will throw an exception
26528 if it is invalid at the time the method is called.
26531 @node Frames In Python
26532 @subsubsection Accessing inferior stack frames from Python.
26534 @cindex frames in python
26535 When the debugged program stops, @value{GDBN} is able to analyze its call
26536 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
26537 represents a frame in the stack. A @code{gdb.Frame} object is only valid
26538 while its corresponding frame exists in the inferior's stack. If you try
26539 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
26540 exception (@pxref{Exception Handling}).
26542 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
26546 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
26550 The following frame-related functions are available in the @code{gdb} module:
26552 @findex gdb.selected_frame
26553 @defun gdb.selected_frame ()
26554 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
26557 @findex gdb.newest_frame
26558 @defun gdb.newest_frame ()
26559 Return the newest frame object for the selected thread.
26562 @defun gdb.frame_stop_reason_string (reason)
26563 Return a string explaining the reason why @value{GDBN} stopped unwinding
26564 frames, as expressed by the given @var{reason} code (an integer, see the
26565 @code{unwind_stop_reason} method further down in this section).
26568 A @code{gdb.Frame} object has the following methods:
26570 @defun Frame.is_valid ()
26571 Returns true if the @code{gdb.Frame} object is valid, false if not.
26572 A frame object can become invalid if the frame it refers to doesn't
26573 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
26574 an exception if it is invalid at the time the method is called.
26577 @defun Frame.name ()
26578 Returns the function name of the frame, or @code{None} if it can't be
26582 @defun Frame.architecture ()
26583 Returns the @code{gdb.Architecture} object corresponding to the frame's
26584 architecture. @xref{Architectures In Python}.
26587 @defun Frame.type ()
26588 Returns the type of the frame. The value can be one of:
26590 @item gdb.NORMAL_FRAME
26591 An ordinary stack frame.
26593 @item gdb.DUMMY_FRAME
26594 A fake stack frame that was created by @value{GDBN} when performing an
26595 inferior function call.
26597 @item gdb.INLINE_FRAME
26598 A frame representing an inlined function. The function was inlined
26599 into a @code{gdb.NORMAL_FRAME} that is older than this one.
26601 @item gdb.TAILCALL_FRAME
26602 A frame representing a tail call. @xref{Tail Call Frames}.
26604 @item gdb.SIGTRAMP_FRAME
26605 A signal trampoline frame. This is the frame created by the OS when
26606 it calls into a signal handler.
26608 @item gdb.ARCH_FRAME
26609 A fake stack frame representing a cross-architecture call.
26611 @item gdb.SENTINEL_FRAME
26612 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
26617 @defun Frame.unwind_stop_reason ()
26618 Return an integer representing the reason why it's not possible to find
26619 more frames toward the outermost frame. Use
26620 @code{gdb.frame_stop_reason_string} to convert the value returned by this
26621 function to a string. The value can be one of:
26624 @item gdb.FRAME_UNWIND_NO_REASON
26625 No particular reason (older frames should be available).
26627 @item gdb.FRAME_UNWIND_NULL_ID
26628 The previous frame's analyzer returns an invalid result. This is no
26629 longer used by @value{GDBN}, and is kept only for backward
26632 @item gdb.FRAME_UNWIND_OUTERMOST
26633 This frame is the outermost.
26635 @item gdb.FRAME_UNWIND_UNAVAILABLE
26636 Cannot unwind further, because that would require knowing the
26637 values of registers or memory that have not been collected.
26639 @item gdb.FRAME_UNWIND_INNER_ID
26640 This frame ID looks like it ought to belong to a NEXT frame,
26641 but we got it for a PREV frame. Normally, this is a sign of
26642 unwinder failure. It could also indicate stack corruption.
26644 @item gdb.FRAME_UNWIND_SAME_ID
26645 This frame has the same ID as the previous one. That means
26646 that unwinding further would almost certainly give us another
26647 frame with exactly the same ID, so break the chain. Normally,
26648 this is a sign of unwinder failure. It could also indicate
26651 @item gdb.FRAME_UNWIND_NO_SAVED_PC
26652 The frame unwinder did not find any saved PC, but we needed
26653 one to unwind further.
26655 @item gdb.FRAME_UNWIND_FIRST_ERROR
26656 Any stop reason greater or equal to this value indicates some kind
26657 of error. This special value facilitates writing code that tests
26658 for errors in unwinding in a way that will work correctly even if
26659 the list of the other values is modified in future @value{GDBN}
26660 versions. Using it, you could write:
26662 reason = gdb.selected_frame().unwind_stop_reason ()
26663 reason_str = gdb.frame_stop_reason_string (reason)
26664 if reason >= gdb.FRAME_UNWIND_FIRST_ERROR:
26665 print "An error occured: %s" % reason_str
26672 Returns the frame's resume address.
26675 @defun Frame.block ()
26676 Return the frame's code block. @xref{Blocks In Python}.
26679 @defun Frame.function ()
26680 Return the symbol for the function corresponding to this frame.
26681 @xref{Symbols In Python}.
26684 @defun Frame.older ()
26685 Return the frame that called this frame.
26688 @defun Frame.newer ()
26689 Return the frame called by this frame.
26692 @defun Frame.find_sal ()
26693 Return the frame's symtab and line object.
26694 @xref{Symbol Tables In Python}.
26697 @defun Frame.read_var (variable @r{[}, block@r{]})
26698 Return the value of @var{variable} in this frame. If the optional
26699 argument @var{block} is provided, search for the variable from that
26700 block; otherwise start at the frame's current block (which is
26701 determined by the frame's current program counter). @var{variable}
26702 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
26703 @code{gdb.Block} object.
26706 @defun Frame.select ()
26707 Set this frame to be the selected frame. @xref{Stack, ,Examining the
26711 @node Blocks In Python
26712 @subsubsection Accessing blocks from Python.
26714 @cindex blocks in python
26717 In @value{GDBN}, symbols are stored in blocks. A block corresponds
26718 roughly to a scope in the source code. Blocks are organized
26719 hierarchically, and are represented individually in Python as a
26720 @code{gdb.Block}. Blocks rely on debugging information being
26723 A frame has a block. Please see @ref{Frames In Python}, for a more
26724 in-depth discussion of frames.
26726 The outermost block is known as the @dfn{global block}. The global
26727 block typically holds public global variables and functions.
26729 The block nested just inside the global block is the @dfn{static
26730 block}. The static block typically holds file-scoped variables and
26733 @value{GDBN} provides a method to get a block's superblock, but there
26734 is currently no way to examine the sub-blocks of a block, or to
26735 iterate over all the blocks in a symbol table (@pxref{Symbol Tables In
26738 Here is a short example that should help explain blocks:
26741 /* This is in the global block. */
26744 /* This is in the static block. */
26745 static int file_scope;
26747 /* 'function' is in the global block, and 'argument' is
26748 in a block nested inside of 'function'. */
26749 int function (int argument)
26751 /* 'local' is in a block inside 'function'. It may or may
26752 not be in the same block as 'argument'. */
26756 /* 'inner' is in a block whose superblock is the one holding
26760 /* If this call is expanded by the compiler, you may see
26761 a nested block here whose function is 'inline_function'
26762 and whose superblock is the one holding 'inner'. */
26763 inline_function ();
26768 A @code{gdb.Block} is iterable. The iterator returns the symbols
26769 (@pxref{Symbols In Python}) local to the block. Python programs
26770 should not assume that a specific block object will always contain a
26771 given symbol, since changes in @value{GDBN} features and
26772 infrastructure may cause symbols move across blocks in a symbol
26775 The following block-related functions are available in the @code{gdb}
26778 @findex gdb.block_for_pc
26779 @defun gdb.block_for_pc (pc)
26780 Return the innermost @code{gdb.Block} containing the given @var{pc}
26781 value. If the block cannot be found for the @var{pc} value specified,
26782 the function will return @code{None}.
26785 A @code{gdb.Block} object has the following methods:
26787 @defun Block.is_valid ()
26788 Returns @code{True} if the @code{gdb.Block} object is valid,
26789 @code{False} if not. A block object can become invalid if the block it
26790 refers to doesn't exist anymore in the inferior. All other
26791 @code{gdb.Block} methods will throw an exception if it is invalid at
26792 the time the method is called. The block's validity is also checked
26793 during iteration over symbols of the block.
26796 A @code{gdb.Block} object has the following attributes:
26798 @defvar Block.start
26799 The start address of the block. This attribute is not writable.
26803 The end address of the block. This attribute is not writable.
26806 @defvar Block.function
26807 The name of the block represented as a @code{gdb.Symbol}. If the
26808 block is not named, then this attribute holds @code{None}. This
26809 attribute is not writable.
26811 For ordinary function blocks, the superblock is the static block.
26812 However, you should note that it is possible for a function block to
26813 have a superblock that is not the static block -- for instance this
26814 happens for an inlined function.
26817 @defvar Block.superblock
26818 The block containing this block. If this parent block does not exist,
26819 this attribute holds @code{None}. This attribute is not writable.
26822 @defvar Block.global_block
26823 The global block associated with this block. This attribute is not
26827 @defvar Block.static_block
26828 The static block associated with this block. This attribute is not
26832 @defvar Block.is_global
26833 @code{True} if the @code{gdb.Block} object is a global block,
26834 @code{False} if not. This attribute is not
26838 @defvar Block.is_static
26839 @code{True} if the @code{gdb.Block} object is a static block,
26840 @code{False} if not. This attribute is not writable.
26843 @node Symbols In Python
26844 @subsubsection Python representation of Symbols.
26846 @cindex symbols in python
26849 @value{GDBN} represents every variable, function and type as an
26850 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
26851 Similarly, Python represents these symbols in @value{GDBN} with the
26852 @code{gdb.Symbol} object.
26854 The following symbol-related functions are available in the @code{gdb}
26857 @findex gdb.lookup_symbol
26858 @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]})
26859 This function searches for a symbol by name. The search scope can be
26860 restricted to the parameters defined in the optional domain and block
26863 @var{name} is the name of the symbol. It must be a string. The
26864 optional @var{block} argument restricts the search to symbols visible
26865 in that @var{block}. The @var{block} argument must be a
26866 @code{gdb.Block} object. If omitted, the block for the current frame
26867 is used. The optional @var{domain} argument restricts
26868 the search to the domain type. The @var{domain} argument must be a
26869 domain constant defined in the @code{gdb} module and described later
26872 The result is a tuple of two elements.
26873 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
26875 If the symbol is found, the second element is @code{True} if the symbol
26876 is a field of a method's object (e.g., @code{this} in C@t{++}),
26877 otherwise it is @code{False}.
26878 If the symbol is not found, the second element is @code{False}.
26881 @findex gdb.lookup_global_symbol
26882 @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]})
26883 This function searches for a global symbol by name.
26884 The search scope can be restricted to by the domain argument.
26886 @var{name} is the name of the symbol. It must be a string.
26887 The optional @var{domain} argument restricts the search to the domain type.
26888 The @var{domain} argument must be a domain constant defined in the @code{gdb}
26889 module and described later in this chapter.
26891 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
26895 A @code{gdb.Symbol} object has the following attributes:
26897 @defvar Symbol.type
26898 The type of the symbol or @code{None} if no type is recorded.
26899 This attribute is represented as a @code{gdb.Type} object.
26900 @xref{Types In Python}. This attribute is not writable.
26903 @defvar Symbol.symtab
26904 The symbol table in which the symbol appears. This attribute is
26905 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
26906 Python}. This attribute is not writable.
26909 @defvar Symbol.line
26910 The line number in the source code at which the symbol was defined.
26911 This is an integer.
26914 @defvar Symbol.name
26915 The name of the symbol as a string. This attribute is not writable.
26918 @defvar Symbol.linkage_name
26919 The name of the symbol, as used by the linker (i.e., may be mangled).
26920 This attribute is not writable.
26923 @defvar Symbol.print_name
26924 The name of the symbol in a form suitable for output. This is either
26925 @code{name} or @code{linkage_name}, depending on whether the user
26926 asked @value{GDBN} to display demangled or mangled names.
26929 @defvar Symbol.addr_class
26930 The address class of the symbol. This classifies how to find the value
26931 of a symbol. Each address class is a constant defined in the
26932 @code{gdb} module and described later in this chapter.
26935 @defvar Symbol.needs_frame
26936 This is @code{True} if evaluating this symbol's value requires a frame
26937 (@pxref{Frames In Python}) and @code{False} otherwise. Typically,
26938 local variables will require a frame, but other symbols will not.
26941 @defvar Symbol.is_argument
26942 @code{True} if the symbol is an argument of a function.
26945 @defvar Symbol.is_constant
26946 @code{True} if the symbol is a constant.
26949 @defvar Symbol.is_function
26950 @code{True} if the symbol is a function or a method.
26953 @defvar Symbol.is_variable
26954 @code{True} if the symbol is a variable.
26957 A @code{gdb.Symbol} object has the following methods:
26959 @defun Symbol.is_valid ()
26960 Returns @code{True} if the @code{gdb.Symbol} object is valid,
26961 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
26962 the symbol it refers to does not exist in @value{GDBN} any longer.
26963 All other @code{gdb.Symbol} methods will throw an exception if it is
26964 invalid at the time the method is called.
26967 @defun Symbol.value (@r{[}frame@r{]})
26968 Compute the value of the symbol, as a @code{gdb.Value}. For
26969 functions, this computes the address of the function, cast to the
26970 appropriate type. If the symbol requires a frame in order to compute
26971 its value, then @var{frame} must be given. If @var{frame} is not
26972 given, or if @var{frame} is invalid, then this method will throw an
26976 The available domain categories in @code{gdb.Symbol} are represented
26977 as constants in the @code{gdb} module:
26980 @findex SYMBOL_UNDEF_DOMAIN
26981 @findex gdb.SYMBOL_UNDEF_DOMAIN
26982 @item gdb.SYMBOL_UNDEF_DOMAIN
26983 This is used when a domain has not been discovered or none of the
26984 following domains apply. This usually indicates an error either
26985 in the symbol information or in @value{GDBN}'s handling of symbols.
26986 @findex SYMBOL_VAR_DOMAIN
26987 @findex gdb.SYMBOL_VAR_DOMAIN
26988 @item gdb.SYMBOL_VAR_DOMAIN
26989 This domain contains variables, function names, typedef names and enum
26991 @findex SYMBOL_STRUCT_DOMAIN
26992 @findex gdb.SYMBOL_STRUCT_DOMAIN
26993 @item gdb.SYMBOL_STRUCT_DOMAIN
26994 This domain holds struct, union and enum type names.
26995 @findex SYMBOL_LABEL_DOMAIN
26996 @findex gdb.SYMBOL_LABEL_DOMAIN
26997 @item gdb.SYMBOL_LABEL_DOMAIN
26998 This domain contains names of labels (for gotos).
26999 @findex SYMBOL_VARIABLES_DOMAIN
27000 @findex gdb.SYMBOL_VARIABLES_DOMAIN
27001 @item gdb.SYMBOL_VARIABLES_DOMAIN
27002 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
27003 contains everything minus functions and types.
27004 @findex SYMBOL_FUNCTIONS_DOMAIN
27005 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
27006 @item gdb.SYMBOL_FUNCTION_DOMAIN
27007 This domain contains all functions.
27008 @findex SYMBOL_TYPES_DOMAIN
27009 @findex gdb.SYMBOL_TYPES_DOMAIN
27010 @item gdb.SYMBOL_TYPES_DOMAIN
27011 This domain contains all types.
27014 The available address class categories in @code{gdb.Symbol} are represented
27015 as constants in the @code{gdb} module:
27018 @findex SYMBOL_LOC_UNDEF
27019 @findex gdb.SYMBOL_LOC_UNDEF
27020 @item gdb.SYMBOL_LOC_UNDEF
27021 If this is returned by address class, it indicates an error either in
27022 the symbol information or in @value{GDBN}'s handling of symbols.
27023 @findex SYMBOL_LOC_CONST
27024 @findex gdb.SYMBOL_LOC_CONST
27025 @item gdb.SYMBOL_LOC_CONST
27026 Value is constant int.
27027 @findex SYMBOL_LOC_STATIC
27028 @findex gdb.SYMBOL_LOC_STATIC
27029 @item gdb.SYMBOL_LOC_STATIC
27030 Value is at a fixed address.
27031 @findex SYMBOL_LOC_REGISTER
27032 @findex gdb.SYMBOL_LOC_REGISTER
27033 @item gdb.SYMBOL_LOC_REGISTER
27034 Value is in a register.
27035 @findex SYMBOL_LOC_ARG
27036 @findex gdb.SYMBOL_LOC_ARG
27037 @item gdb.SYMBOL_LOC_ARG
27038 Value is an argument. This value is at the offset stored within the
27039 symbol inside the frame's argument list.
27040 @findex SYMBOL_LOC_REF_ARG
27041 @findex gdb.SYMBOL_LOC_REF_ARG
27042 @item gdb.SYMBOL_LOC_REF_ARG
27043 Value address is stored in the frame's argument list. Just like
27044 @code{LOC_ARG} except that the value's address is stored at the
27045 offset, not the value itself.
27046 @findex SYMBOL_LOC_REGPARM_ADDR
27047 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
27048 @item gdb.SYMBOL_LOC_REGPARM_ADDR
27049 Value is a specified register. Just like @code{LOC_REGISTER} except
27050 the register holds the address of the argument instead of the argument
27052 @findex SYMBOL_LOC_LOCAL
27053 @findex gdb.SYMBOL_LOC_LOCAL
27054 @item gdb.SYMBOL_LOC_LOCAL
27055 Value is a local variable.
27056 @findex SYMBOL_LOC_TYPEDEF
27057 @findex gdb.SYMBOL_LOC_TYPEDEF
27058 @item gdb.SYMBOL_LOC_TYPEDEF
27059 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
27061 @findex SYMBOL_LOC_BLOCK
27062 @findex gdb.SYMBOL_LOC_BLOCK
27063 @item gdb.SYMBOL_LOC_BLOCK
27065 @findex SYMBOL_LOC_CONST_BYTES
27066 @findex gdb.SYMBOL_LOC_CONST_BYTES
27067 @item gdb.SYMBOL_LOC_CONST_BYTES
27068 Value is a byte-sequence.
27069 @findex SYMBOL_LOC_UNRESOLVED
27070 @findex gdb.SYMBOL_LOC_UNRESOLVED
27071 @item gdb.SYMBOL_LOC_UNRESOLVED
27072 Value is at a fixed address, but the address of the variable has to be
27073 determined from the minimal symbol table whenever the variable is
27075 @findex SYMBOL_LOC_OPTIMIZED_OUT
27076 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
27077 @item gdb.SYMBOL_LOC_OPTIMIZED_OUT
27078 The value does not actually exist in the program.
27079 @findex SYMBOL_LOC_COMPUTED
27080 @findex gdb.SYMBOL_LOC_COMPUTED
27081 @item gdb.SYMBOL_LOC_COMPUTED
27082 The value's address is a computed location.
27085 @node Symbol Tables In Python
27086 @subsubsection Symbol table representation in Python.
27088 @cindex symbol tables in python
27090 @tindex gdb.Symtab_and_line
27092 Access to symbol table data maintained by @value{GDBN} on the inferior
27093 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
27094 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
27095 from the @code{find_sal} method in @code{gdb.Frame} object.
27096 @xref{Frames In Python}.
27098 For more information on @value{GDBN}'s symbol table management, see
27099 @ref{Symbols, ,Examining the Symbol Table}, for more information.
27101 A @code{gdb.Symtab_and_line} object has the following attributes:
27103 @defvar Symtab_and_line.symtab
27104 The symbol table object (@code{gdb.Symtab}) for this frame.
27105 This attribute is not writable.
27108 @defvar Symtab_and_line.pc
27109 Indicates the start of the address range occupied by code for the
27110 current source line. This attribute is not writable.
27113 @defvar Symtab_and_line.last
27114 Indicates the end of the address range occupied by code for the current
27115 source line. This attribute is not writable.
27118 @defvar Symtab_and_line.line
27119 Indicates the current line number for this object. This
27120 attribute is not writable.
27123 A @code{gdb.Symtab_and_line} object has the following methods:
27125 @defun Symtab_and_line.is_valid ()
27126 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
27127 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
27128 invalid if the Symbol table and line object it refers to does not
27129 exist in @value{GDBN} any longer. All other
27130 @code{gdb.Symtab_and_line} methods will throw an exception if it is
27131 invalid at the time the method is called.
27134 A @code{gdb.Symtab} object has the following attributes:
27136 @defvar Symtab.filename
27137 The symbol table's source filename. This attribute is not writable.
27140 @defvar Symtab.objfile
27141 The symbol table's backing object file. @xref{Objfiles In Python}.
27142 This attribute is not writable.
27145 A @code{gdb.Symtab} object has the following methods:
27147 @defun Symtab.is_valid ()
27148 Returns @code{True} if the @code{gdb.Symtab} object is valid,
27149 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
27150 the symbol table it refers to does not exist in @value{GDBN} any
27151 longer. All other @code{gdb.Symtab} methods will throw an exception
27152 if it is invalid at the time the method is called.
27155 @defun Symtab.fullname ()
27156 Return the symbol table's source absolute file name.
27159 @defun Symtab.global_block ()
27160 Return the global block of the underlying symbol table.
27161 @xref{Blocks In Python}.
27164 @defun Symtab.static_block ()
27165 Return the static block of the underlying symbol table.
27166 @xref{Blocks In Python}.
27169 @defun Symtab.linetable ()
27170 Return the line table associated with the symbol table.
27171 @xref{Line Tables In Python}.
27174 @node Line Tables In Python
27175 @subsubsection Manipulating line tables using Python
27177 @cindex line tables in python
27178 @tindex gdb.LineTable
27180 Python code can request and inspect line table information from a
27181 symbol table that is loaded in @value{GDBN}. A line table is a
27182 mapping of source lines to their executable locations in memory. To
27183 acquire the line table information for a particular symbol table, use
27184 the @code{linetable} function (@pxref{Symbol Tables In Python}).
27186 A @code{gdb.LineTable} is iterable. The iterator returns
27187 @code{LineTableEntry} objects that correspond to the source line and
27188 address for each line table entry. @code{LineTableEntry} objects have
27189 the following attributes:
27191 @defvar LineTableEntry.line
27192 The source line number for this line table entry. This number
27193 corresponds to the actual line of source. This attribute is not
27197 @defvar LineTableEntry.pc
27198 The address that is associated with the line table entry where the
27199 executable code for that source line resides in memory. This
27200 attribute is not writable.
27203 As there can be multiple addresses for a single source line, you may
27204 receive multiple @code{LineTableEntry} objects with matching
27205 @code{line} attributes, but with different @code{pc} attributes. The
27206 iterator is sorted in ascending @code{pc} order. Here is a small
27207 example illustrating iterating over a line table.
27210 symtab = gdb.selected_frame().find_sal().symtab
27211 linetable = symtab.linetable()
27212 for line in linetable:
27213 print "Line: "+str(line.line)+" Address: "+hex(line.pc)
27216 This will have the following output:
27219 Line: 33 Address: 0x4005c8L
27220 Line: 37 Address: 0x4005caL
27221 Line: 39 Address: 0x4005d2L
27222 Line: 40 Address: 0x4005f8L
27223 Line: 42 Address: 0x4005ffL
27224 Line: 44 Address: 0x400608L
27225 Line: 42 Address: 0x40060cL
27226 Line: 45 Address: 0x400615L
27229 In addition to being able to iterate over a @code{LineTable}, it also
27230 has the following direct access methods:
27232 @defun LineTable.line (line)
27233 Return a Python @code{Tuple} of @code{LineTableEntry} objects for any
27234 entries in the line table for the given @var{line}. @var{line} refers
27235 to the source code line. If there are no entries for that source code
27236 @var{line}, the Python @code{None} is returned.
27239 @defun LineTable.has_line (line)
27240 Return a Python @code{Boolean} indicating whether there is an entry in
27241 the line table for this source line. Return @code{True} if an entry
27242 is found, or @code{False} if not.
27245 @defun LineTable.source_lines ()
27246 Return a Python @code{List} of the source line numbers in the symbol
27247 table. Only lines with executable code locations are returned. The
27248 contents of the @code{List} will just be the source line entries
27249 represented as Python @code{Long} values.
27252 @node Breakpoints In Python
27253 @subsubsection Manipulating breakpoints using Python
27255 @cindex breakpoints in python
27256 @tindex gdb.Breakpoint
27258 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
27261 @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal @r{[},temporary@r{]]]]})
27262 Create a new breakpoint. @var{spec} is a string naming the location
27263 of the breakpoint, or an expression that defines a watchpoint. The
27264 contents can be any location recognized by the @code{break} command,
27265 or in the case of a watchpoint, by the @code{watch} command. The
27266 optional @var{type} denotes the breakpoint to create from the types
27267 defined later in this chapter. This argument can be either:
27268 @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type}
27269 defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal}
27270 argument allows the breakpoint to become invisible to the user. The
27271 breakpoint will neither be reported when created, nor will it be
27272 listed in the output from @code{info breakpoints} (but will be listed
27273 with the @code{maint info breakpoints} command). The optional
27274 @var{temporary} argument makes the breakpoint a temporary breakpoint.
27275 Temporary breakpoints are deleted after they have been hit. Any
27276 further access to the Python breakpoint after it has been hit will
27277 result in a runtime error (as that breakpoint has now been
27278 automatically deleted). The optional @var{wp_class} argument defines
27279 the class of watchpoint to create, if @var{type} is
27280 @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it
27281 is assumed to be a @code{gdb.WP_WRITE} class.
27284 @defun Breakpoint.stop (self)
27285 The @code{gdb.Breakpoint} class can be sub-classed and, in
27286 particular, you may choose to implement the @code{stop} method.
27287 If this method is defined in a sub-class of @code{gdb.Breakpoint},
27288 it will be called when the inferior reaches any location of a
27289 breakpoint which instantiates that sub-class. If the method returns
27290 @code{True}, the inferior will be stopped at the location of the
27291 breakpoint, otherwise the inferior will continue.
27293 If there are multiple breakpoints at the same location with a
27294 @code{stop} method, each one will be called regardless of the
27295 return status of the previous. This ensures that all @code{stop}
27296 methods have a chance to execute at that location. In this scenario
27297 if one of the methods returns @code{True} but the others return
27298 @code{False}, the inferior will still be stopped.
27300 You should not alter the execution state of the inferior (i.e.@:, step,
27301 next, etc.), alter the current frame context (i.e.@:, change the current
27302 active frame), or alter, add or delete any breakpoint. As a general
27303 rule, you should not alter any data within @value{GDBN} or the inferior
27306 Example @code{stop} implementation:
27309 class MyBreakpoint (gdb.Breakpoint):
27311 inf_val = gdb.parse_and_eval("foo")
27318 The available watchpoint types represented by constants are defined in the
27323 @findex gdb.WP_READ
27325 Read only watchpoint.
27328 @findex gdb.WP_WRITE
27330 Write only watchpoint.
27333 @findex gdb.WP_ACCESS
27334 @item gdb.WP_ACCESS
27335 Read/Write watchpoint.
27338 @defun Breakpoint.is_valid ()
27339 Return @code{True} if this @code{Breakpoint} object is valid,
27340 @code{False} otherwise. A @code{Breakpoint} object can become invalid
27341 if the user deletes the breakpoint. In this case, the object still
27342 exists, but the underlying breakpoint does not. In the cases of
27343 watchpoint scope, the watchpoint remains valid even if execution of the
27344 inferior leaves the scope of that watchpoint.
27347 @defun Breakpoint.delete
27348 Permanently deletes the @value{GDBN} breakpoint. This also
27349 invalidates the Python @code{Breakpoint} object. Any further access
27350 to this object's attributes or methods will raise an error.
27353 @defvar Breakpoint.enabled
27354 This attribute is @code{True} if the breakpoint is enabled, and
27355 @code{False} otherwise. This attribute is writable.
27358 @defvar Breakpoint.silent
27359 This attribute is @code{True} if the breakpoint is silent, and
27360 @code{False} otherwise. This attribute is writable.
27362 Note that a breakpoint can also be silent if it has commands and the
27363 first command is @code{silent}. This is not reported by the
27364 @code{silent} attribute.
27367 @defvar Breakpoint.thread
27368 If the breakpoint is thread-specific, this attribute holds the thread
27369 id. If the breakpoint is not thread-specific, this attribute is
27370 @code{None}. This attribute is writable.
27373 @defvar Breakpoint.task
27374 If the breakpoint is Ada task-specific, this attribute holds the Ada task
27375 id. If the breakpoint is not task-specific (or the underlying
27376 language is not Ada), this attribute is @code{None}. This attribute
27380 @defvar Breakpoint.ignore_count
27381 This attribute holds the ignore count for the breakpoint, an integer.
27382 This attribute is writable.
27385 @defvar Breakpoint.number
27386 This attribute holds the breakpoint's number --- the identifier used by
27387 the user to manipulate the breakpoint. This attribute is not writable.
27390 @defvar Breakpoint.type
27391 This attribute holds the breakpoint's type --- the identifier used to
27392 determine the actual breakpoint type or use-case. This attribute is not
27396 @defvar Breakpoint.visible
27397 This attribute tells whether the breakpoint is visible to the user
27398 when set, or when the @samp{info breakpoints} command is run. This
27399 attribute is not writable.
27402 @defvar Breakpoint.temporary
27403 This attribute indicates whether the breakpoint was created as a
27404 temporary breakpoint. Temporary breakpoints are automatically deleted
27405 after that breakpoint has been hit. Access to this attribute, and all
27406 other attributes and functions other than the @code{is_valid}
27407 function, will result in an error after the breakpoint has been hit
27408 (as it has been automatically deleted). This attribute is not
27412 The available types are represented by constants defined in the @code{gdb}
27416 @findex BP_BREAKPOINT
27417 @findex gdb.BP_BREAKPOINT
27418 @item gdb.BP_BREAKPOINT
27419 Normal code breakpoint.
27421 @findex BP_WATCHPOINT
27422 @findex gdb.BP_WATCHPOINT
27423 @item gdb.BP_WATCHPOINT
27424 Watchpoint breakpoint.
27426 @findex BP_HARDWARE_WATCHPOINT
27427 @findex gdb.BP_HARDWARE_WATCHPOINT
27428 @item gdb.BP_HARDWARE_WATCHPOINT
27429 Hardware assisted watchpoint.
27431 @findex BP_READ_WATCHPOINT
27432 @findex gdb.BP_READ_WATCHPOINT
27433 @item gdb.BP_READ_WATCHPOINT
27434 Hardware assisted read watchpoint.
27436 @findex BP_ACCESS_WATCHPOINT
27437 @findex gdb.BP_ACCESS_WATCHPOINT
27438 @item gdb.BP_ACCESS_WATCHPOINT
27439 Hardware assisted access watchpoint.
27442 @defvar Breakpoint.hit_count
27443 This attribute holds the hit count for the breakpoint, an integer.
27444 This attribute is writable, but currently it can only be set to zero.
27447 @defvar Breakpoint.location
27448 This attribute holds the location of the breakpoint, as specified by
27449 the user. It is a string. If the breakpoint does not have a location
27450 (that is, it is a watchpoint) the attribute's value is @code{None}. This
27451 attribute is not writable.
27454 @defvar Breakpoint.expression
27455 This attribute holds a breakpoint expression, as specified by
27456 the user. It is a string. If the breakpoint does not have an
27457 expression (the breakpoint is not a watchpoint) the attribute's value
27458 is @code{None}. This attribute is not writable.
27461 @defvar Breakpoint.condition
27462 This attribute holds the condition of the breakpoint, as specified by
27463 the user. It is a string. If there is no condition, this attribute's
27464 value is @code{None}. This attribute is writable.
27467 @defvar Breakpoint.commands
27468 This attribute holds the commands attached to the breakpoint. If
27469 there are commands, this attribute's value is a string holding all the
27470 commands, separated by newlines. If there are no commands, this
27471 attribute is @code{None}. This attribute is not writable.
27474 @node Finish Breakpoints in Python
27475 @subsubsection Finish Breakpoints
27477 @cindex python finish breakpoints
27478 @tindex gdb.FinishBreakpoint
27480 A finish breakpoint is a temporary breakpoint set at the return address of
27481 a frame, based on the @code{finish} command. @code{gdb.FinishBreakpoint}
27482 extends @code{gdb.Breakpoint}. The underlying breakpoint will be disabled
27483 and deleted when the execution will run out of the breakpoint scope (i.e.@:
27484 @code{Breakpoint.stop} or @code{FinishBreakpoint.out_of_scope} triggered).
27485 Finish breakpoints are thread specific and must be create with the right
27488 @defun FinishBreakpoint.__init__ (@r{[}frame@r{]} @r{[}, internal@r{]})
27489 Create a finish breakpoint at the return address of the @code{gdb.Frame}
27490 object @var{frame}. If @var{frame} is not provided, this defaults to the
27491 newest frame. The optional @var{internal} argument allows the breakpoint to
27492 become invisible to the user. @xref{Breakpoints In Python}, for further
27493 details about this argument.
27496 @defun FinishBreakpoint.out_of_scope (self)
27497 In some circumstances (e.g.@: @code{longjmp}, C@t{++} exceptions, @value{GDBN}
27498 @code{return} command, @dots{}), a function may not properly terminate, and
27499 thus never hit the finish breakpoint. When @value{GDBN} notices such a
27500 situation, the @code{out_of_scope} callback will be triggered.
27502 You may want to sub-class @code{gdb.FinishBreakpoint} and override this
27506 class MyFinishBreakpoint (gdb.FinishBreakpoint)
27508 print "normal finish"
27511 def out_of_scope ():
27512 print "abnormal finish"
27516 @defvar FinishBreakpoint.return_value
27517 When @value{GDBN} is stopped at a finish breakpoint and the frame
27518 used to build the @code{gdb.FinishBreakpoint} object had debug symbols, this
27519 attribute will contain a @code{gdb.Value} object corresponding to the return
27520 value of the function. The value will be @code{None} if the function return
27521 type is @code{void} or if the return value was not computable. This attribute
27525 @node Lazy Strings In Python
27526 @subsubsection Python representation of lazy strings.
27528 @cindex lazy strings in python
27529 @tindex gdb.LazyString
27531 A @dfn{lazy string} is a string whose contents is not retrieved or
27532 encoded until it is needed.
27534 A @code{gdb.LazyString} is represented in @value{GDBN} as an
27535 @code{address} that points to a region of memory, an @code{encoding}
27536 that will be used to encode that region of memory, and a @code{length}
27537 to delimit the region of memory that represents the string. The
27538 difference between a @code{gdb.LazyString} and a string wrapped within
27539 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
27540 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
27541 retrieved and encoded during printing, while a @code{gdb.Value}
27542 wrapping a string is immediately retrieved and encoded on creation.
27544 A @code{gdb.LazyString} object has the following functions:
27546 @defun LazyString.value ()
27547 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
27548 will point to the string in memory, but will lose all the delayed
27549 retrieval, encoding and handling that @value{GDBN} applies to a
27550 @code{gdb.LazyString}.
27553 @defvar LazyString.address
27554 This attribute holds the address of the string. This attribute is not
27558 @defvar LazyString.length
27559 This attribute holds the length of the string in characters. If the
27560 length is -1, then the string will be fetched and encoded up to the
27561 first null of appropriate width. This attribute is not writable.
27564 @defvar LazyString.encoding
27565 This attribute holds the encoding that will be applied to the string
27566 when the string is printed by @value{GDBN}. If the encoding is not
27567 set, or contains an empty string, then @value{GDBN} will select the
27568 most appropriate encoding when the string is printed. This attribute
27572 @defvar LazyString.type
27573 This attribute holds the type that is represented by the lazy string's
27574 type. For a lazy string this will always be a pointer type. To
27575 resolve this to the lazy string's character type, use the type's
27576 @code{target} method. @xref{Types In Python}. This attribute is not
27580 @node Architectures In Python
27581 @subsubsection Python representation of architectures
27582 @cindex Python architectures
27584 @value{GDBN} uses architecture specific parameters and artifacts in a
27585 number of its various computations. An architecture is represented
27586 by an instance of the @code{gdb.Architecture} class.
27588 A @code{gdb.Architecture} class has the following methods:
27590 @defun Architecture.name ()
27591 Return the name (string value) of the architecture.
27594 @defun Architecture.disassemble (@var{start_pc} @r{[}, @var{end_pc} @r{[}, @var{count}@r{]]})
27595 Return a list of disassembled instructions starting from the memory
27596 address @var{start_pc}. The optional arguments @var{end_pc} and
27597 @var{count} determine the number of instructions in the returned list.
27598 If both the optional arguments @var{end_pc} and @var{count} are
27599 specified, then a list of at most @var{count} disassembled instructions
27600 whose start address falls in the closed memory address interval from
27601 @var{start_pc} to @var{end_pc} are returned. If @var{end_pc} is not
27602 specified, but @var{count} is specified, then @var{count} number of
27603 instructions starting from the address @var{start_pc} are returned. If
27604 @var{count} is not specified but @var{end_pc} is specified, then all
27605 instructions whose start address falls in the closed memory address
27606 interval from @var{start_pc} to @var{end_pc} are returned. If neither
27607 @var{end_pc} nor @var{count} are specified, then a single instruction at
27608 @var{start_pc} is returned. For all of these cases, each element of the
27609 returned list is a Python @code{dict} with the following string keys:
27614 The value corresponding to this key is a Python long integer capturing
27615 the memory address of the instruction.
27618 The value corresponding to this key is a string value which represents
27619 the instruction with assembly language mnemonics. The assembly
27620 language flavor used is the same as that specified by the current CLI
27621 variable @code{disassembly-flavor}. @xref{Machine Code}.
27624 The value corresponding to this key is the length (integer value) of the
27625 instruction in bytes.
27630 @node Python Auto-loading
27631 @subsection Python Auto-loading
27632 @cindex Python auto-loading
27634 When a new object file is read (for example, due to the @code{file}
27635 command, or because the inferior has loaded a shared library),
27636 @value{GDBN} will look for Python support scripts in several ways:
27637 @file{@var{objfile}-gdb.py} and @code{.debug_gdb_scripts} section.
27638 @xref{Auto-loading extensions}.
27640 The auto-loading feature is useful for supplying application-specific
27641 debugging commands and scripts.
27643 Auto-loading can be enabled or disabled,
27644 and the list of auto-loaded scripts can be printed.
27647 @anchor{set auto-load python-scripts}
27648 @kindex set auto-load python-scripts
27649 @item set auto-load python-scripts [on|off]
27650 Enable or disable the auto-loading of Python scripts.
27652 @anchor{show auto-load python-scripts}
27653 @kindex show auto-load python-scripts
27654 @item show auto-load python-scripts
27655 Show whether auto-loading of Python scripts is enabled or disabled.
27657 @anchor{info auto-load python-scripts}
27658 @kindex info auto-load python-scripts
27659 @cindex print list of auto-loaded Python scripts
27660 @item info auto-load python-scripts [@var{regexp}]
27661 Print the list of all Python scripts that @value{GDBN} auto-loaded.
27663 Also printed is the list of Python scripts that were mentioned in
27664 the @code{.debug_gdb_scripts} section and were not found
27665 (@pxref{dotdebug_gdb_scripts section}).
27666 This is useful because their names are not printed when @value{GDBN}
27667 tries to load them and fails. There may be many of them, and printing
27668 an error message for each one is problematic.
27670 If @var{regexp} is supplied only Python scripts with matching names are printed.
27675 (gdb) info auto-load python-scripts
27677 Yes py-section-script.py
27678 full name: /tmp/py-section-script.py
27679 No my-foo-pretty-printers.py
27683 When reading an auto-loaded file, @value{GDBN} sets the
27684 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
27685 function (@pxref{Objfiles In Python}). This can be useful for
27686 registering objfile-specific pretty-printers and frame-filters.
27688 @node Python modules
27689 @subsection Python modules
27690 @cindex python modules
27692 @value{GDBN} comes with several modules to assist writing Python code.
27695 * gdb.printing:: Building and registering pretty-printers.
27696 * gdb.types:: Utilities for working with types.
27697 * gdb.prompt:: Utilities for prompt value substitution.
27701 @subsubsection gdb.printing
27702 @cindex gdb.printing
27704 This module provides a collection of utilities for working with
27708 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
27709 This class specifies the API that makes @samp{info pretty-printer},
27710 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
27711 Pretty-printers should generally inherit from this class.
27713 @item SubPrettyPrinter (@var{name})
27714 For printers that handle multiple types, this class specifies the
27715 corresponding API for the subprinters.
27717 @item RegexpCollectionPrettyPrinter (@var{name})
27718 Utility class for handling multiple printers, all recognized via
27719 regular expressions.
27720 @xref{Writing a Pretty-Printer}, for an example.
27722 @item FlagEnumerationPrinter (@var{name})
27723 A pretty-printer which handles printing of @code{enum} values. Unlike
27724 @value{GDBN}'s built-in @code{enum} printing, this printer attempts to
27725 work properly when there is some overlap between the enumeration
27726 constants. @var{name} is the name of the printer and also the name of
27727 the @code{enum} type to look up.
27729 @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False)
27730 Register @var{printer} with the pretty-printer list of @var{obj}.
27731 If @var{replace} is @code{True} then any existing copy of the printer
27732 is replaced. Otherwise a @code{RuntimeError} exception is raised
27733 if a printer with the same name already exists.
27737 @subsubsection gdb.types
27740 This module provides a collection of utilities for working with
27741 @code{gdb.Type} objects.
27744 @item get_basic_type (@var{type})
27745 Return @var{type} with const and volatile qualifiers stripped,
27746 and with typedefs and C@t{++} references converted to the underlying type.
27751 typedef const int const_int;
27753 const_int& foo_ref (foo);
27754 int main () @{ return 0; @}
27761 (gdb) python import gdb.types
27762 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
27763 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
27767 @item has_field (@var{type}, @var{field})
27768 Return @code{True} if @var{type}, assumed to be a type with fields
27769 (e.g., a structure or union), has field @var{field}.
27771 @item make_enum_dict (@var{enum_type})
27772 Return a Python @code{dictionary} type produced from @var{enum_type}.
27774 @item deep_items (@var{type})
27775 Returns a Python iterator similar to the standard
27776 @code{gdb.Type.iteritems} method, except that the iterator returned
27777 by @code{deep_items} will recursively traverse anonymous struct or
27778 union fields. For example:
27792 Then in @value{GDBN}:
27794 (@value{GDBP}) python import gdb.types
27795 (@value{GDBP}) python struct_a = gdb.lookup_type("struct A")
27796 (@value{GDBP}) python print struct_a.keys ()
27798 (@value{GDBP}) python print [k for k,v in gdb.types.deep_items(struct_a)]
27799 @{['a', 'b0', 'b1']@}
27802 @item get_type_recognizers ()
27803 Return a list of the enabled type recognizers for the current context.
27804 This is called by @value{GDBN} during the type-printing process
27805 (@pxref{Type Printing API}).
27807 @item apply_type_recognizers (recognizers, type_obj)
27808 Apply the type recognizers, @var{recognizers}, to the type object
27809 @var{type_obj}. If any recognizer returns a string, return that
27810 string. Otherwise, return @code{None}. This is called by
27811 @value{GDBN} during the type-printing process (@pxref{Type Printing
27814 @item register_type_printer (locus, printer)
27815 This is a convenience function to register a type printer.
27816 @var{printer} is the type printer to register. It must implement the
27817 type printer protocol. @var{locus} is either a @code{gdb.Objfile}, in
27818 which case the printer is registered with that objfile; a
27819 @code{gdb.Progspace}, in which case the printer is registered with
27820 that progspace; or @code{None}, in which case the printer is
27821 registered globally.
27824 This is a base class that implements the type printer protocol. Type
27825 printers are encouraged, but not required, to derive from this class.
27826 It defines a constructor:
27828 @defmethod TypePrinter __init__ (self, name)
27829 Initialize the type printer with the given name. The new printer
27830 starts in the enabled state.
27836 @subsubsection gdb.prompt
27839 This module provides a method for prompt value-substitution.
27842 @item substitute_prompt (@var{string})
27843 Return @var{string} with escape sequences substituted by values. Some
27844 escape sequences take arguments. You can specify arguments inside
27845 ``@{@}'' immediately following the escape sequence.
27847 The escape sequences you can pass to this function are:
27851 Substitute a backslash.
27853 Substitute an ESC character.
27855 Substitute the selected frame; an argument names a frame parameter.
27857 Substitute a newline.
27859 Substitute a parameter's value; the argument names the parameter.
27861 Substitute a carriage return.
27863 Substitute the selected thread; an argument names a thread parameter.
27865 Substitute the version of GDB.
27867 Substitute the current working directory.
27869 Begin a sequence of non-printing characters. These sequences are
27870 typically used with the ESC character, and are not counted in the string
27871 length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a
27872 blue-colored ``(gdb)'' prompt where the length is five.
27874 End a sequence of non-printing characters.
27880 substitute_prompt (``frame: \f,
27881 print arguments: \p@{print frame-arguments@}'')
27884 @exdent will return the string:
27887 "frame: main, print arguments: scalars"
27891 @node Auto-loading extensions
27892 @section Auto-loading extensions
27893 @cindex auto-loading extensions
27895 @value{GDBN} provides two mechanisms for automatically loading extensions
27896 when a new object file is read (for example, due to the @code{file}
27897 command, or because the inferior has loaded a shared library):
27898 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
27899 section of modern file formats like ELF.
27902 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
27903 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
27904 * Which flavor to choose?::
27907 The auto-loading feature is useful for supplying application-specific
27908 debugging commands and features.
27910 Auto-loading can be enabled or disabled,
27911 and the list of auto-loaded scripts can be printed.
27912 See the @samp{auto-loading} section of each extension language
27913 for more information.
27914 For @value{GDBN} command files see @ref{Auto-loading sequences}.
27915 For Python files see @ref{Python Auto-loading}.
27917 Note that loading of this script file also requires accordingly configured
27918 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27920 @node objfile-gdbdotext file
27921 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
27922 @cindex @file{@var{objfile}-gdb.gdb}
27923 @cindex @file{@var{objfile}-gdb.py}
27924 @cindex @file{@var{objfile}-gdb.scm}
27926 When a new object file is read, @value{GDBN} looks for a file named
27927 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
27928 where @var{objfile} is the object file's name and
27929 where @var{ext} is the file extension for the extension language:
27932 @item @file{@var{objfile}-gdb.gdb}
27933 GDB's own command language
27934 @item @file{@var{objfile}-gdb.py}
27938 @var{script-name} is formed by ensuring that the file name of @var{objfile}
27939 is absolute, following all symlinks, and resolving @code{.} and @code{..}
27940 components, and appending the @file{-gdb.@var{ext}} suffix.
27941 If this file exists and is readable, @value{GDBN} will evaluate it as a
27942 script in the specified extension language.
27944 If this file does not exist, then @value{GDBN} will look for
27945 @var{script-name} file in all of the directories as specified below.
27947 Note that loading of these files requires an accordingly configured
27948 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27950 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
27951 scripts normally according to its @file{.exe} filename. But if no scripts are
27952 found @value{GDBN} also tries script filenames matching the object file without
27953 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
27954 is attempted on any platform. This makes the script filenames compatible
27955 between Unix and MS-Windows hosts.
27958 @anchor{set auto-load scripts-directory}
27959 @kindex set auto-load scripts-directory
27960 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
27961 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
27962 may be delimited by the host platform path separator in use
27963 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
27965 Each entry here needs to be covered also by the security setting
27966 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
27968 @anchor{with-auto-load-dir}
27969 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
27970 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
27971 configuration option @option{--with-auto-load-dir}.
27973 Any reference to @file{$debugdir} will get replaced by
27974 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
27975 reference to @file{$datadir} will get replaced by @var{data-directory} which is
27976 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
27977 @file{$datadir} must be placed as a directory component --- either alone or
27978 delimited by @file{/} or @file{\} directory separators, depending on the host
27981 The list of directories uses path separator (@samp{:} on GNU and Unix
27982 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
27983 to the @env{PATH} environment variable.
27985 @anchor{show auto-load scripts-directory}
27986 @kindex show auto-load scripts-directory
27987 @item show auto-load scripts-directory
27988 Show @value{GDBN} auto-loaded scripts location.
27991 @value{GDBN} does not track which files it has already auto-loaded this way.
27992 @value{GDBN} will load the associated script every time the corresponding
27993 @var{objfile} is opened.
27994 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
27995 is evaluated more than once.
27997 @node dotdebug_gdb_scripts section
27998 @subsection The @code{.debug_gdb_scripts} section
27999 @cindex @code{.debug_gdb_scripts} section
28001 For systems using file formats like ELF and COFF,
28002 when @value{GDBN} loads a new object file
28003 it will look for a special section named @code{.debug_gdb_scripts}.
28004 If this section exists, its contents is a list of NUL-terminated names
28005 of scripts to load. Each entry begins with a non-NULL prefix byte that
28006 specifies the kind of entry, typically the extension language.
28008 @value{GDBN} will look for each specified script file first in the
28009 current directory and then along the source search path
28010 (@pxref{Source Path, ,Specifying Source Directories}),
28011 except that @file{$cdir} is not searched, since the compilation
28012 directory is not relevant to scripts.
28014 Entries can be placed in section @code{.debug_gdb_scripts} with,
28015 for example, this GCC macro for Python scripts.
28018 /* Note: The "MS" section flags are to remove duplicates. */
28019 #define DEFINE_GDB_PY_SCRIPT(script_name) \
28021 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
28022 .byte 1 /* Python */\n\
28023 .asciz \"" script_name "\"\n\
28029 Then one can reference the macro in a header or source file like this:
28032 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
28035 The script name may include directories if desired.
28037 Note that loading of this script file also requires accordingly configured
28038 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
28040 If the macro invocation is put in a header, any application or library
28041 using this header will get a reference to the specified script,
28042 and with the use of @code{"MS"} attributes on the section, the linker
28043 will remove duplicates.
28045 @node Which flavor to choose?
28046 @subsection Which flavor to choose?
28048 Given the multiple ways of auto-loading extensions, it might not always
28049 be clear which one to choose. This section provides some guidance.
28052 Benefits of the @file{-gdb.@var{ext}} way:
28056 Can be used with file formats that don't support multiple sections.
28059 Ease of finding scripts for public libraries.
28061 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
28062 in the source search path.
28063 For publicly installed libraries, e.g., @file{libstdc++}, there typically
28064 isn't a source directory in which to find the script.
28067 Doesn't require source code additions.
28071 Benefits of the @code{.debug_gdb_scripts} way:
28075 Works with static linking.
28077 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
28078 trigger their loading. When an application is statically linked the only
28079 objfile available is the executable, and it is cumbersome to attach all the
28080 scripts from all the input libraries to the executable's
28081 @file{-gdb.@var{ext}} script.
28084 Works with classes that are entirely inlined.
28086 Some classes can be entirely inlined, and thus there may not be an associated
28087 shared library to attach a @file{-gdb.@var{ext}} script to.
28090 Scripts needn't be copied out of the source tree.
28092 In some circumstances, apps can be built out of large collections of internal
28093 libraries, and the build infrastructure necessary to install the
28094 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
28095 cumbersome. It may be easier to specify the scripts in the
28096 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
28097 top of the source tree to the source search path.
28101 @section Creating new spellings of existing commands
28102 @cindex aliases for commands
28104 It is often useful to define alternate spellings of existing commands.
28105 For example, if a new @value{GDBN} command defined in Python has
28106 a long name to type, it is handy to have an abbreviated version of it
28107 that involves less typing.
28109 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
28110 of the @samp{step} command even though it is otherwise an ambiguous
28111 abbreviation of other commands like @samp{set} and @samp{show}.
28113 Aliases are also used to provide shortened or more common versions
28114 of multi-word commands. For example, @value{GDBN} provides the
28115 @samp{tty} alias of the @samp{set inferior-tty} command.
28117 You can define a new alias with the @samp{alias} command.
28122 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
28126 @var{ALIAS} specifies the name of the new alias.
28127 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
28130 @var{COMMAND} specifies the name of an existing command
28131 that is being aliased.
28133 The @samp{-a} option specifies that the new alias is an abbreviation
28134 of the command. Abbreviations are not shown in command
28135 lists displayed by the @samp{help} command.
28137 The @samp{--} option specifies the end of options,
28138 and is useful when @var{ALIAS} begins with a dash.
28140 Here is a simple example showing how to make an abbreviation
28141 of a command so that there is less to type.
28142 Suppose you were tired of typing @samp{disas}, the current
28143 shortest unambiguous abbreviation of the @samp{disassemble} command
28144 and you wanted an even shorter version named @samp{di}.
28145 The following will accomplish this.
28148 (gdb) alias -a di = disas
28151 Note that aliases are different from user-defined commands.
28152 With a user-defined command, you also need to write documentation
28153 for it with the @samp{document} command.
28154 An alias automatically picks up the documentation of the existing command.
28156 Here is an example where we make @samp{elms} an abbreviation of
28157 @samp{elements} in the @samp{set print elements} command.
28158 This is to show that you can make an abbreviation of any part
28162 (gdb) alias -a set print elms = set print elements
28163 (gdb) alias -a show print elms = show print elements
28164 (gdb) set p elms 20
28166 Limit on string chars or array elements to print is 200.
28169 Note that if you are defining an alias of a @samp{set} command,
28170 and you want to have an alias for the corresponding @samp{show}
28171 command, then you need to define the latter separately.
28173 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
28174 @var{ALIAS}, just as they are normally.
28177 (gdb) alias -a set pr elms = set p ele
28180 Finally, here is an example showing the creation of a one word
28181 alias for a more complex command.
28182 This creates alias @samp{spe} of the command @samp{set print elements}.
28185 (gdb) alias spe = set print elements
28190 @chapter Command Interpreters
28191 @cindex command interpreters
28193 @value{GDBN} supports multiple command interpreters, and some command
28194 infrastructure to allow users or user interface writers to switch
28195 between interpreters or run commands in other interpreters.
28197 @value{GDBN} currently supports two command interpreters, the console
28198 interpreter (sometimes called the command-line interpreter or @sc{cli})
28199 and the machine interface interpreter (or @sc{gdb/mi}). This manual
28200 describes both of these interfaces in great detail.
28202 By default, @value{GDBN} will start with the console interpreter.
28203 However, the user may choose to start @value{GDBN} with another
28204 interpreter by specifying the @option{-i} or @option{--interpreter}
28205 startup options. Defined interpreters include:
28209 @cindex console interpreter
28210 The traditional console or command-line interpreter. This is the most often
28211 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
28212 @value{GDBN} will use this interpreter.
28215 @cindex mi interpreter
28216 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
28217 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
28218 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
28222 @cindex mi2 interpreter
28223 The current @sc{gdb/mi} interface.
28226 @cindex mi1 interpreter
28227 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
28231 @cindex invoke another interpreter
28232 The interpreter being used by @value{GDBN} may not be dynamically
28233 switched at runtime. Although possible, this could lead to a very
28234 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
28235 enters the command "interpreter-set console" in a console view,
28236 @value{GDBN} would switch to using the console interpreter, rendering
28237 the IDE inoperable!
28239 @kindex interpreter-exec
28240 Although you may only choose a single interpreter at startup, you may execute
28241 commands in any interpreter from the current interpreter using the appropriate
28242 command. If you are running the console interpreter, simply use the
28243 @code{interpreter-exec} command:
28246 interpreter-exec mi "-data-list-register-names"
28249 @sc{gdb/mi} has a similar command, although it is only available in versions of
28250 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
28253 @chapter @value{GDBN} Text User Interface
28255 @cindex Text User Interface
28258 * TUI Overview:: TUI overview
28259 * TUI Keys:: TUI key bindings
28260 * TUI Single Key Mode:: TUI single key mode
28261 * TUI Commands:: TUI-specific commands
28262 * TUI Configuration:: TUI configuration variables
28265 The @value{GDBN} Text User Interface (TUI) is a terminal
28266 interface which uses the @code{curses} library to show the source
28267 file, the assembly output, the program registers and @value{GDBN}
28268 commands in separate text windows. The TUI mode is supported only
28269 on platforms where a suitable version of the @code{curses} library
28272 The TUI mode is enabled by default when you invoke @value{GDBN} as
28273 @samp{@value{GDBP} -tui}.
28274 You can also switch in and out of TUI mode while @value{GDBN} runs by
28275 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
28276 @xref{TUI Keys, ,TUI Key Bindings}.
28279 @section TUI Overview
28281 In TUI mode, @value{GDBN} can display several text windows:
28285 This window is the @value{GDBN} command window with the @value{GDBN}
28286 prompt and the @value{GDBN} output. The @value{GDBN} input is still
28287 managed using readline.
28290 The source window shows the source file of the program. The current
28291 line and active breakpoints are displayed in this window.
28294 The assembly window shows the disassembly output of the program.
28297 This window shows the processor registers. Registers are highlighted
28298 when their values change.
28301 The source and assembly windows show the current program position
28302 by highlighting the current line and marking it with a @samp{>} marker.
28303 Breakpoints are indicated with two markers. The first marker
28304 indicates the breakpoint type:
28308 Breakpoint which was hit at least once.
28311 Breakpoint which was never hit.
28314 Hardware breakpoint which was hit at least once.
28317 Hardware breakpoint which was never hit.
28320 The second marker indicates whether the breakpoint is enabled or not:
28324 Breakpoint is enabled.
28327 Breakpoint is disabled.
28330 The source, assembly and register windows are updated when the current
28331 thread changes, when the frame changes, or when the program counter
28334 These windows are not all visible at the same time. The command
28335 window is always visible. The others can be arranged in several
28346 source and assembly,
28349 source and registers, or
28352 assembly and registers.
28355 A status line above the command window shows the following information:
28359 Indicates the current @value{GDBN} target.
28360 (@pxref{Targets, ,Specifying a Debugging Target}).
28363 Gives the current process or thread number.
28364 When no process is being debugged, this field is set to @code{No process}.
28367 Gives the current function name for the selected frame.
28368 The name is demangled if demangling is turned on (@pxref{Print Settings}).
28369 When there is no symbol corresponding to the current program counter,
28370 the string @code{??} is displayed.
28373 Indicates the current line number for the selected frame.
28374 When the current line number is not known, the string @code{??} is displayed.
28377 Indicates the current program counter address.
28381 @section TUI Key Bindings
28382 @cindex TUI key bindings
28384 The TUI installs several key bindings in the readline keymaps
28385 @ifset SYSTEM_READLINE
28386 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
28388 @ifclear SYSTEM_READLINE
28389 (@pxref{Command Line Editing}).
28391 The following key bindings are installed for both TUI mode and the
28392 @value{GDBN} standard mode.
28401 Enter or leave the TUI mode. When leaving the TUI mode,
28402 the curses window management stops and @value{GDBN} operates using
28403 its standard mode, writing on the terminal directly. When reentering
28404 the TUI mode, control is given back to the curses windows.
28405 The screen is then refreshed.
28409 Use a TUI layout with only one window. The layout will
28410 either be @samp{source} or @samp{assembly}. When the TUI mode
28411 is not active, it will switch to the TUI mode.
28413 Think of this key binding as the Emacs @kbd{C-x 1} binding.
28417 Use a TUI layout with at least two windows. When the current
28418 layout already has two windows, the next layout with two windows is used.
28419 When a new layout is chosen, one window will always be common to the
28420 previous layout and the new one.
28422 Think of it as the Emacs @kbd{C-x 2} binding.
28426 Change the active window. The TUI associates several key bindings
28427 (like scrolling and arrow keys) with the active window. This command
28428 gives the focus to the next TUI window.
28430 Think of it as the Emacs @kbd{C-x o} binding.
28434 Switch in and out of the TUI SingleKey mode that binds single
28435 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
28438 The following key bindings only work in the TUI mode:
28443 Scroll the active window one page up.
28447 Scroll the active window one page down.
28451 Scroll the active window one line up.
28455 Scroll the active window one line down.
28459 Scroll the active window one column left.
28463 Scroll the active window one column right.
28467 Refresh the screen.
28470 Because the arrow keys scroll the active window in the TUI mode, they
28471 are not available for their normal use by readline unless the command
28472 window has the focus. When another window is active, you must use
28473 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
28474 and @kbd{C-f} to control the command window.
28476 @node TUI Single Key Mode
28477 @section TUI Single Key Mode
28478 @cindex TUI single key mode
28480 The TUI also provides a @dfn{SingleKey} mode, which binds several
28481 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
28482 switch into this mode, where the following key bindings are used:
28485 @kindex c @r{(SingleKey TUI key)}
28489 @kindex d @r{(SingleKey TUI key)}
28493 @kindex f @r{(SingleKey TUI key)}
28497 @kindex n @r{(SingleKey TUI key)}
28501 @kindex q @r{(SingleKey TUI key)}
28503 exit the SingleKey mode.
28505 @kindex r @r{(SingleKey TUI key)}
28509 @kindex s @r{(SingleKey TUI key)}
28513 @kindex u @r{(SingleKey TUI key)}
28517 @kindex v @r{(SingleKey TUI key)}
28521 @kindex w @r{(SingleKey TUI key)}
28526 Other keys temporarily switch to the @value{GDBN} command prompt.
28527 The key that was pressed is inserted in the editing buffer so that
28528 it is possible to type most @value{GDBN} commands without interaction
28529 with the TUI SingleKey mode. Once the command is entered the TUI
28530 SingleKey mode is restored. The only way to permanently leave
28531 this mode is by typing @kbd{q} or @kbd{C-x s}.
28535 @section TUI-specific Commands
28536 @cindex TUI commands
28538 The TUI has specific commands to control the text windows.
28539 These commands are always available, even when @value{GDBN} is not in
28540 the TUI mode. When @value{GDBN} is in the standard mode, most
28541 of these commands will automatically switch to the TUI mode.
28543 Note that if @value{GDBN}'s @code{stdout} is not connected to a
28544 terminal, or @value{GDBN} has been started with the machine interface
28545 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
28546 these commands will fail with an error, because it would not be
28547 possible or desirable to enable curses window management.
28552 List and give the size of all displayed windows.
28556 Display the next layout.
28559 Display the previous layout.
28562 Display the source window only.
28565 Display the assembly window only.
28568 Display the source and assembly window.
28571 Display the register window together with the source or assembly window.
28575 Make the next window active for scrolling.
28578 Make the previous window active for scrolling.
28581 Make the source window active for scrolling.
28584 Make the assembly window active for scrolling.
28587 Make the register window active for scrolling.
28590 Make the command window active for scrolling.
28594 Refresh the screen. This is similar to typing @kbd{C-L}.
28596 @item tui reg float
28598 Show the floating point registers in the register window.
28600 @item tui reg general
28601 Show the general registers in the register window.
28604 Show the next register group. The list of register groups as well as
28605 their order is target specific. The predefined register groups are the
28606 following: @code{general}, @code{float}, @code{system}, @code{vector},
28607 @code{all}, @code{save}, @code{restore}.
28609 @item tui reg system
28610 Show the system registers in the register window.
28614 Update the source window and the current execution point.
28616 @item winheight @var{name} +@var{count}
28617 @itemx winheight @var{name} -@var{count}
28619 Change the height of the window @var{name} by @var{count}
28620 lines. Positive counts increase the height, while negative counts
28623 @item tabset @var{nchars}
28625 Set the width of tab stops to be @var{nchars} characters.
28628 @node TUI Configuration
28629 @section TUI Configuration Variables
28630 @cindex TUI configuration variables
28632 Several configuration variables control the appearance of TUI windows.
28635 @item set tui border-kind @var{kind}
28636 @kindex set tui border-kind
28637 Select the border appearance for the source, assembly and register windows.
28638 The possible values are the following:
28641 Use a space character to draw the border.
28644 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
28647 Use the Alternate Character Set to draw the border. The border is
28648 drawn using character line graphics if the terminal supports them.
28651 @item set tui border-mode @var{mode}
28652 @kindex set tui border-mode
28653 @itemx set tui active-border-mode @var{mode}
28654 @kindex set tui active-border-mode
28655 Select the display attributes for the borders of the inactive windows
28656 or the active window. The @var{mode} can be one of the following:
28659 Use normal attributes to display the border.
28665 Use reverse video mode.
28668 Use half bright mode.
28670 @item half-standout
28671 Use half bright and standout mode.
28674 Use extra bright or bold mode.
28676 @item bold-standout
28677 Use extra bright or bold and standout mode.
28682 @chapter Using @value{GDBN} under @sc{gnu} Emacs
28685 @cindex @sc{gnu} Emacs
28686 A special interface allows you to use @sc{gnu} Emacs to view (and
28687 edit) the source files for the program you are debugging with
28690 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
28691 executable file you want to debug as an argument. This command starts
28692 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
28693 created Emacs buffer.
28694 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
28696 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
28701 All ``terminal'' input and output goes through an Emacs buffer, called
28704 This applies both to @value{GDBN} commands and their output, and to the input
28705 and output done by the program you are debugging.
28707 This is useful because it means that you can copy the text of previous
28708 commands and input them again; you can even use parts of the output
28711 All the facilities of Emacs' Shell mode are available for interacting
28712 with your program. In particular, you can send signals the usual
28713 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
28717 @value{GDBN} displays source code through Emacs.
28719 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
28720 source file for that frame and puts an arrow (@samp{=>}) at the
28721 left margin of the current line. Emacs uses a separate buffer for
28722 source display, and splits the screen to show both your @value{GDBN} session
28725 Explicit @value{GDBN} @code{list} or search commands still produce output as
28726 usual, but you probably have no reason to use them from Emacs.
28729 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
28730 a graphical mode, enabled by default, which provides further buffers
28731 that can control the execution and describe the state of your program.
28732 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
28734 If you specify an absolute file name when prompted for the @kbd{M-x
28735 gdb} argument, then Emacs sets your current working directory to where
28736 your program resides. If you only specify the file name, then Emacs
28737 sets your current working directory to the directory associated
28738 with the previous buffer. In this case, @value{GDBN} may find your
28739 program by searching your environment's @code{PATH} variable, but on
28740 some operating systems it might not find the source. So, although the
28741 @value{GDBN} input and output session proceeds normally, the auxiliary
28742 buffer does not display the current source and line of execution.
28744 The initial working directory of @value{GDBN} is printed on the top
28745 line of the GUD buffer and this serves as a default for the commands
28746 that specify files for @value{GDBN} to operate on. @xref{Files,
28747 ,Commands to Specify Files}.
28749 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
28750 need to call @value{GDBN} by a different name (for example, if you
28751 keep several configurations around, with different names) you can
28752 customize the Emacs variable @code{gud-gdb-command-name} to run the
28755 In the GUD buffer, you can use these special Emacs commands in
28756 addition to the standard Shell mode commands:
28760 Describe the features of Emacs' GUD Mode.
28763 Execute to another source line, like the @value{GDBN} @code{step} command; also
28764 update the display window to show the current file and location.
28767 Execute to next source line in this function, skipping all function
28768 calls, like the @value{GDBN} @code{next} command. Then update the display window
28769 to show the current file and location.
28772 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
28773 display window accordingly.
28776 Execute until exit from the selected stack frame, like the @value{GDBN}
28777 @code{finish} command.
28780 Continue execution of your program, like the @value{GDBN} @code{continue}
28784 Go up the number of frames indicated by the numeric argument
28785 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
28786 like the @value{GDBN} @code{up} command.
28789 Go down the number of frames indicated by the numeric argument, like the
28790 @value{GDBN} @code{down} command.
28793 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
28794 tells @value{GDBN} to set a breakpoint on the source line point is on.
28796 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
28797 separate frame which shows a backtrace when the GUD buffer is current.
28798 Move point to any frame in the stack and type @key{RET} to make it
28799 become the current frame and display the associated source in the
28800 source buffer. Alternatively, click @kbd{Mouse-2} to make the
28801 selected frame become the current one. In graphical mode, the
28802 speedbar displays watch expressions.
28804 If you accidentally delete the source-display buffer, an easy way to get
28805 it back is to type the command @code{f} in the @value{GDBN} buffer, to
28806 request a frame display; when you run under Emacs, this recreates
28807 the source buffer if necessary to show you the context of the current
28810 The source files displayed in Emacs are in ordinary Emacs buffers
28811 which are visiting the source files in the usual way. You can edit
28812 the files with these buffers if you wish; but keep in mind that @value{GDBN}
28813 communicates with Emacs in terms of line numbers. If you add or
28814 delete lines from the text, the line numbers that @value{GDBN} knows cease
28815 to correspond properly with the code.
28817 A more detailed description of Emacs' interaction with @value{GDBN} is
28818 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
28822 @chapter The @sc{gdb/mi} Interface
28824 @unnumberedsec Function and Purpose
28826 @cindex @sc{gdb/mi}, its purpose
28827 @sc{gdb/mi} is a line based machine oriented text interface to
28828 @value{GDBN} and is activated by specifying using the
28829 @option{--interpreter} command line option (@pxref{Mode Options}). It
28830 is specifically intended to support the development of systems which
28831 use the debugger as just one small component of a larger system.
28833 This chapter is a specification of the @sc{gdb/mi} interface. It is written
28834 in the form of a reference manual.
28836 Note that @sc{gdb/mi} is still under construction, so some of the
28837 features described below are incomplete and subject to change
28838 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
28840 @unnumberedsec Notation and Terminology
28842 @cindex notational conventions, for @sc{gdb/mi}
28843 This chapter uses the following notation:
28847 @code{|} separates two alternatives.
28850 @code{[ @var{something} ]} indicates that @var{something} is optional:
28851 it may or may not be given.
28854 @code{( @var{group} )*} means that @var{group} inside the parentheses
28855 may repeat zero or more times.
28858 @code{( @var{group} )+} means that @var{group} inside the parentheses
28859 may repeat one or more times.
28862 @code{"@var{string}"} means a literal @var{string}.
28866 @heading Dependencies
28870 * GDB/MI General Design::
28871 * GDB/MI Command Syntax::
28872 * GDB/MI Compatibility with CLI::
28873 * GDB/MI Development and Front Ends::
28874 * GDB/MI Output Records::
28875 * GDB/MI Simple Examples::
28876 * GDB/MI Command Description Format::
28877 * GDB/MI Breakpoint Commands::
28878 * GDB/MI Catchpoint Commands::
28879 * GDB/MI Program Context::
28880 * GDB/MI Thread Commands::
28881 * GDB/MI Ada Tasking Commands::
28882 * GDB/MI Program Execution::
28883 * GDB/MI Stack Manipulation::
28884 * GDB/MI Variable Objects::
28885 * GDB/MI Data Manipulation::
28886 * GDB/MI Tracepoint Commands::
28887 * GDB/MI Symbol Query::
28888 * GDB/MI File Commands::
28890 * GDB/MI Kod Commands::
28891 * GDB/MI Memory Overlay Commands::
28892 * GDB/MI Signal Handling Commands::
28894 * GDB/MI Target Manipulation::
28895 * GDB/MI File Transfer Commands::
28896 * GDB/MI Ada Exceptions Commands::
28897 * GDB/MI Support Commands::
28898 * GDB/MI Miscellaneous Commands::
28901 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28902 @node GDB/MI General Design
28903 @section @sc{gdb/mi} General Design
28904 @cindex GDB/MI General Design
28906 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
28907 parts---commands sent to @value{GDBN}, responses to those commands
28908 and notifications. Each command results in exactly one response,
28909 indicating either successful completion of the command, or an error.
28910 For the commands that do not resume the target, the response contains the
28911 requested information. For the commands that resume the target, the
28912 response only indicates whether the target was successfully resumed.
28913 Notifications is the mechanism for reporting changes in the state of the
28914 target, or in @value{GDBN} state, that cannot conveniently be associated with
28915 a command and reported as part of that command response.
28917 The important examples of notifications are:
28921 Exec notifications. These are used to report changes in
28922 target state---when a target is resumed, or stopped. It would not
28923 be feasible to include this information in response of resuming
28924 commands, because one resume commands can result in multiple events in
28925 different threads. Also, quite some time may pass before any event
28926 happens in the target, while a frontend needs to know whether the resuming
28927 command itself was successfully executed.
28930 Console output, and status notifications. Console output
28931 notifications are used to report output of CLI commands, as well as
28932 diagnostics for other commands. Status notifications are used to
28933 report the progress of a long-running operation. Naturally, including
28934 this information in command response would mean no output is produced
28935 until the command is finished, which is undesirable.
28938 General notifications. Commands may have various side effects on
28939 the @value{GDBN} or target state beyond their official purpose. For example,
28940 a command may change the selected thread. Although such changes can
28941 be included in command response, using notification allows for more
28942 orthogonal frontend design.
28946 There's no guarantee that whenever an MI command reports an error,
28947 @value{GDBN} or the target are in any specific state, and especially,
28948 the state is not reverted to the state before the MI command was
28949 processed. Therefore, whenever an MI command results in an error,
28950 we recommend that the frontend refreshes all the information shown in
28951 the user interface.
28955 * Context management::
28956 * Asynchronous and non-stop modes::
28960 @node Context management
28961 @subsection Context management
28963 @subsubsection Threads and Frames
28965 In most cases when @value{GDBN} accesses the target, this access is
28966 done in context of a specific thread and frame (@pxref{Frames}).
28967 Often, even when accessing global data, the target requires that a thread
28968 be specified. The CLI interface maintains the selected thread and frame,
28969 and supplies them to target on each command. This is convenient,
28970 because a command line user would not want to specify that information
28971 explicitly on each command, and because user interacts with
28972 @value{GDBN} via a single terminal, so no confusion is possible as
28973 to what thread and frame are the current ones.
28975 In the case of MI, the concept of selected thread and frame is less
28976 useful. First, a frontend can easily remember this information
28977 itself. Second, a graphical frontend can have more than one window,
28978 each one used for debugging a different thread, and the frontend might
28979 want to access additional threads for internal purposes. This
28980 increases the risk that by relying on implicitly selected thread, the
28981 frontend may be operating on a wrong one. Therefore, each MI command
28982 should explicitly specify which thread and frame to operate on. To
28983 make it possible, each MI command accepts the @samp{--thread} and
28984 @samp{--frame} options, the value to each is @value{GDBN} identifier
28985 for thread and frame to operate on.
28987 Usually, each top-level window in a frontend allows the user to select
28988 a thread and a frame, and remembers the user selection for further
28989 operations. However, in some cases @value{GDBN} may suggest that the
28990 current thread be changed. For example, when stopping on a breakpoint
28991 it is reasonable to switch to the thread where breakpoint is hit. For
28992 another example, if the user issues the CLI @samp{thread} command via
28993 the frontend, it is desirable to change the frontend's selected thread to the
28994 one specified by user. @value{GDBN} communicates the suggestion to
28995 change current thread using the @samp{=thread-selected} notification.
28996 No such notification is available for the selected frame at the moment.
28998 Note that historically, MI shares the selected thread with CLI, so
28999 frontends used the @code{-thread-select} to execute commands in the
29000 right context. However, getting this to work right is cumbersome. The
29001 simplest way is for frontend to emit @code{-thread-select} command
29002 before every command. This doubles the number of commands that need
29003 to be sent. The alternative approach is to suppress @code{-thread-select}
29004 if the selected thread in @value{GDBN} is supposed to be identical to the
29005 thread the frontend wants to operate on. However, getting this
29006 optimization right can be tricky. In particular, if the frontend
29007 sends several commands to @value{GDBN}, and one of the commands changes the
29008 selected thread, then the behaviour of subsequent commands will
29009 change. So, a frontend should either wait for response from such
29010 problematic commands, or explicitly add @code{-thread-select} for
29011 all subsequent commands. No frontend is known to do this exactly
29012 right, so it is suggested to just always pass the @samp{--thread} and
29013 @samp{--frame} options.
29015 @subsubsection Language
29017 The execution of several commands depends on which language is selected.
29018 By default, the current language (@pxref{show language}) is used.
29019 But for commands known to be language-sensitive, it is recommended
29020 to use the @samp{--language} option. This option takes one argument,
29021 which is the name of the language to use while executing the command.
29025 -data-evaluate-expression --language c "sizeof (void*)"
29030 The valid language names are the same names accepted by the
29031 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
29032 @samp{local} or @samp{unknown}.
29034 @node Asynchronous and non-stop modes
29035 @subsection Asynchronous command execution and non-stop mode
29037 On some targets, @value{GDBN} is capable of processing MI commands
29038 even while the target is running. This is called @dfn{asynchronous
29039 command execution} (@pxref{Background Execution}). The frontend may
29040 specify a preferrence for asynchronous execution using the
29041 @code{-gdb-set target-async 1} command, which should be emitted before
29042 either running the executable or attaching to the target. After the
29043 frontend has started the executable or attached to the target, it can
29044 find if asynchronous execution is enabled using the
29045 @code{-list-target-features} command.
29047 Even if @value{GDBN} can accept a command while target is running,
29048 many commands that access the target do not work when the target is
29049 running. Therefore, asynchronous command execution is most useful
29050 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
29051 it is possible to examine the state of one thread, while other threads
29054 When a given thread is running, MI commands that try to access the
29055 target in the context of that thread may not work, or may work only on
29056 some targets. In particular, commands that try to operate on thread's
29057 stack will not work, on any target. Commands that read memory, or
29058 modify breakpoints, may work or not work, depending on the target. Note
29059 that even commands that operate on global state, such as @code{print},
29060 @code{set}, and breakpoint commands, still access the target in the
29061 context of a specific thread, so frontend should try to find a
29062 stopped thread and perform the operation on that thread (using the
29063 @samp{--thread} option).
29065 Which commands will work in the context of a running thread is
29066 highly target dependent. However, the two commands
29067 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
29068 to find the state of a thread, will always work.
29070 @node Thread groups
29071 @subsection Thread groups
29072 @value{GDBN} may be used to debug several processes at the same time.
29073 On some platfroms, @value{GDBN} may support debugging of several
29074 hardware systems, each one having several cores with several different
29075 processes running on each core. This section describes the MI
29076 mechanism to support such debugging scenarios.
29078 The key observation is that regardless of the structure of the
29079 target, MI can have a global list of threads, because most commands that
29080 accept the @samp{--thread} option do not need to know what process that
29081 thread belongs to. Therefore, it is not necessary to introduce
29082 neither additional @samp{--process} option, nor an notion of the
29083 current process in the MI interface. The only strictly new feature
29084 that is required is the ability to find how the threads are grouped
29087 To allow the user to discover such grouping, and to support arbitrary
29088 hierarchy of machines/cores/processes, MI introduces the concept of a
29089 @dfn{thread group}. Thread group is a collection of threads and other
29090 thread groups. A thread group always has a string identifier, a type,
29091 and may have additional attributes specific to the type. A new
29092 command, @code{-list-thread-groups}, returns the list of top-level
29093 thread groups, which correspond to processes that @value{GDBN} is
29094 debugging at the moment. By passing an identifier of a thread group
29095 to the @code{-list-thread-groups} command, it is possible to obtain
29096 the members of specific thread group.
29098 To allow the user to easily discover processes, and other objects, he
29099 wishes to debug, a concept of @dfn{available thread group} is
29100 introduced. Available thread group is an thread group that
29101 @value{GDBN} is not debugging, but that can be attached to, using the
29102 @code{-target-attach} command. The list of available top-level thread
29103 groups can be obtained using @samp{-list-thread-groups --available}.
29104 In general, the content of a thread group may be only retrieved only
29105 after attaching to that thread group.
29107 Thread groups are related to inferiors (@pxref{Inferiors and
29108 Programs}). Each inferior corresponds to a thread group of a special
29109 type @samp{process}, and some additional operations are permitted on
29110 such thread groups.
29112 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29113 @node GDB/MI Command Syntax
29114 @section @sc{gdb/mi} Command Syntax
29117 * GDB/MI Input Syntax::
29118 * GDB/MI Output Syntax::
29121 @node GDB/MI Input Syntax
29122 @subsection @sc{gdb/mi} Input Syntax
29124 @cindex input syntax for @sc{gdb/mi}
29125 @cindex @sc{gdb/mi}, input syntax
29127 @item @var{command} @expansion{}
29128 @code{@var{cli-command} | @var{mi-command}}
29130 @item @var{cli-command} @expansion{}
29131 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
29132 @var{cli-command} is any existing @value{GDBN} CLI command.
29134 @item @var{mi-command} @expansion{}
29135 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
29136 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
29138 @item @var{token} @expansion{}
29139 "any sequence of digits"
29141 @item @var{option} @expansion{}
29142 @code{"-" @var{parameter} [ " " @var{parameter} ]}
29144 @item @var{parameter} @expansion{}
29145 @code{@var{non-blank-sequence} | @var{c-string}}
29147 @item @var{operation} @expansion{}
29148 @emph{any of the operations described in this chapter}
29150 @item @var{non-blank-sequence} @expansion{}
29151 @emph{anything, provided it doesn't contain special characters such as
29152 "-", @var{nl}, """ and of course " "}
29154 @item @var{c-string} @expansion{}
29155 @code{""" @var{seven-bit-iso-c-string-content} """}
29157 @item @var{nl} @expansion{}
29166 The CLI commands are still handled by the @sc{mi} interpreter; their
29167 output is described below.
29170 The @code{@var{token}}, when present, is passed back when the command
29174 Some @sc{mi} commands accept optional arguments as part of the parameter
29175 list. Each option is identified by a leading @samp{-} (dash) and may be
29176 followed by an optional argument parameter. Options occur first in the
29177 parameter list and can be delimited from normal parameters using
29178 @samp{--} (this is useful when some parameters begin with a dash).
29185 We want easy access to the existing CLI syntax (for debugging).
29188 We want it to be easy to spot a @sc{mi} operation.
29191 @node GDB/MI Output Syntax
29192 @subsection @sc{gdb/mi} Output Syntax
29194 @cindex output syntax of @sc{gdb/mi}
29195 @cindex @sc{gdb/mi}, output syntax
29196 The output from @sc{gdb/mi} consists of zero or more out-of-band records
29197 followed, optionally, by a single result record. This result record
29198 is for the most recent command. The sequence of output records is
29199 terminated by @samp{(gdb)}.
29201 If an input command was prefixed with a @code{@var{token}} then the
29202 corresponding output for that command will also be prefixed by that same
29206 @item @var{output} @expansion{}
29207 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
29209 @item @var{result-record} @expansion{}
29210 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
29212 @item @var{out-of-band-record} @expansion{}
29213 @code{@var{async-record} | @var{stream-record}}
29215 @item @var{async-record} @expansion{}
29216 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
29218 @item @var{exec-async-output} @expansion{}
29219 @code{[ @var{token} ] "*" @var{async-output nl}}
29221 @item @var{status-async-output} @expansion{}
29222 @code{[ @var{token} ] "+" @var{async-output nl}}
29224 @item @var{notify-async-output} @expansion{}
29225 @code{[ @var{token} ] "=" @var{async-output nl}}
29227 @item @var{async-output} @expansion{}
29228 @code{@var{async-class} ( "," @var{result} )*}
29230 @item @var{result-class} @expansion{}
29231 @code{"done" | "running" | "connected" | "error" | "exit"}
29233 @item @var{async-class} @expansion{}
29234 @code{"stopped" | @var{others}} (where @var{others} will be added
29235 depending on the needs---this is still in development).
29237 @item @var{result} @expansion{}
29238 @code{ @var{variable} "=" @var{value}}
29240 @item @var{variable} @expansion{}
29241 @code{ @var{string} }
29243 @item @var{value} @expansion{}
29244 @code{ @var{const} | @var{tuple} | @var{list} }
29246 @item @var{const} @expansion{}
29247 @code{@var{c-string}}
29249 @item @var{tuple} @expansion{}
29250 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
29252 @item @var{list} @expansion{}
29253 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
29254 @var{result} ( "," @var{result} )* "]" }
29256 @item @var{stream-record} @expansion{}
29257 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
29259 @item @var{console-stream-output} @expansion{}
29260 @code{"~" @var{c-string nl}}
29262 @item @var{target-stream-output} @expansion{}
29263 @code{"@@" @var{c-string nl}}
29265 @item @var{log-stream-output} @expansion{}
29266 @code{"&" @var{c-string nl}}
29268 @item @var{nl} @expansion{}
29271 @item @var{token} @expansion{}
29272 @emph{any sequence of digits}.
29280 All output sequences end in a single line containing a period.
29283 The @code{@var{token}} is from the corresponding request. Note that
29284 for all async output, while the token is allowed by the grammar and
29285 may be output by future versions of @value{GDBN} for select async
29286 output messages, it is generally omitted. Frontends should treat
29287 all async output as reporting general changes in the state of the
29288 target and there should be no need to associate async output to any
29292 @cindex status output in @sc{gdb/mi}
29293 @var{status-async-output} contains on-going status information about the
29294 progress of a slow operation. It can be discarded. All status output is
29295 prefixed by @samp{+}.
29298 @cindex async output in @sc{gdb/mi}
29299 @var{exec-async-output} contains asynchronous state change on the target
29300 (stopped, started, disappeared). All async output is prefixed by
29304 @cindex notify output in @sc{gdb/mi}
29305 @var{notify-async-output} contains supplementary information that the
29306 client should handle (e.g., a new breakpoint information). All notify
29307 output is prefixed by @samp{=}.
29310 @cindex console output in @sc{gdb/mi}
29311 @var{console-stream-output} is output that should be displayed as is in the
29312 console. It is the textual response to a CLI command. All the console
29313 output is prefixed by @samp{~}.
29316 @cindex target output in @sc{gdb/mi}
29317 @var{target-stream-output} is the output produced by the target program.
29318 All the target output is prefixed by @samp{@@}.
29321 @cindex log output in @sc{gdb/mi}
29322 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
29323 instance messages that should be displayed as part of an error log. All
29324 the log output is prefixed by @samp{&}.
29327 @cindex list output in @sc{gdb/mi}
29328 New @sc{gdb/mi} commands should only output @var{lists} containing
29334 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
29335 details about the various output records.
29337 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29338 @node GDB/MI Compatibility with CLI
29339 @section @sc{gdb/mi} Compatibility with CLI
29341 @cindex compatibility, @sc{gdb/mi} and CLI
29342 @cindex @sc{gdb/mi}, compatibility with CLI
29344 For the developers convenience CLI commands can be entered directly,
29345 but there may be some unexpected behaviour. For example, commands
29346 that query the user will behave as if the user replied yes, breakpoint
29347 command lists are not executed and some CLI commands, such as
29348 @code{if}, @code{when} and @code{define}, prompt for further input with
29349 @samp{>}, which is not valid MI output.
29351 This feature may be removed at some stage in the future and it is
29352 recommended that front ends use the @code{-interpreter-exec} command
29353 (@pxref{-interpreter-exec}).
29355 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29356 @node GDB/MI Development and Front Ends
29357 @section @sc{gdb/mi} Development and Front Ends
29358 @cindex @sc{gdb/mi} development
29360 The application which takes the MI output and presents the state of the
29361 program being debugged to the user is called a @dfn{front end}.
29363 Although @sc{gdb/mi} is still incomplete, it is currently being used
29364 by a variety of front ends to @value{GDBN}. This makes it difficult
29365 to introduce new functionality without breaking existing usage. This
29366 section tries to minimize the problems by describing how the protocol
29369 Some changes in MI need not break a carefully designed front end, and
29370 for these the MI version will remain unchanged. The following is a
29371 list of changes that may occur within one level, so front ends should
29372 parse MI output in a way that can handle them:
29376 New MI commands may be added.
29379 New fields may be added to the output of any MI command.
29382 The range of values for fields with specified values, e.g.,
29383 @code{in_scope} (@pxref{-var-update}) may be extended.
29385 @c The format of field's content e.g type prefix, may change so parse it
29386 @c at your own risk. Yes, in general?
29388 @c The order of fields may change? Shouldn't really matter but it might
29389 @c resolve inconsistencies.
29392 If the changes are likely to break front ends, the MI version level
29393 will be increased by one. This will allow the front end to parse the
29394 output according to the MI version. Apart from mi0, new versions of
29395 @value{GDBN} will not support old versions of MI and it will be the
29396 responsibility of the front end to work with the new one.
29398 @c Starting with mi3, add a new command -mi-version that prints the MI
29401 The best way to avoid unexpected changes in MI that might break your front
29402 end is to make your project known to @value{GDBN} developers and
29403 follow development on @email{gdb@@sourceware.org} and
29404 @email{gdb-patches@@sourceware.org}.
29405 @cindex mailing lists
29407 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29408 @node GDB/MI Output Records
29409 @section @sc{gdb/mi} Output Records
29412 * GDB/MI Result Records::
29413 * GDB/MI Stream Records::
29414 * GDB/MI Async Records::
29415 * GDB/MI Breakpoint Information::
29416 * GDB/MI Frame Information::
29417 * GDB/MI Thread Information::
29418 * GDB/MI Ada Exception Information::
29421 @node GDB/MI Result Records
29422 @subsection @sc{gdb/mi} Result Records
29424 @cindex result records in @sc{gdb/mi}
29425 @cindex @sc{gdb/mi}, result records
29426 In addition to a number of out-of-band notifications, the response to a
29427 @sc{gdb/mi} command includes one of the following result indications:
29431 @item "^done" [ "," @var{results} ]
29432 The synchronous operation was successful, @code{@var{results}} are the return
29437 This result record is equivalent to @samp{^done}. Historically, it
29438 was output instead of @samp{^done} if the command has resumed the
29439 target. This behaviour is maintained for backward compatibility, but
29440 all frontends should treat @samp{^done} and @samp{^running}
29441 identically and rely on the @samp{*running} output record to determine
29442 which threads are resumed.
29446 @value{GDBN} has connected to a remote target.
29448 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
29450 The operation failed. The @code{msg=@var{c-string}} variable contains
29451 the corresponding error message.
29453 If present, the @code{code=@var{c-string}} variable provides an error
29454 code on which consumers can rely on to detect the corresponding
29455 error condition. At present, only one error code is defined:
29458 @item "undefined-command"
29459 Indicates that the command causing the error does not exist.
29464 @value{GDBN} has terminated.
29468 @node GDB/MI Stream Records
29469 @subsection @sc{gdb/mi} Stream Records
29471 @cindex @sc{gdb/mi}, stream records
29472 @cindex stream records in @sc{gdb/mi}
29473 @value{GDBN} internally maintains a number of output streams: the console, the
29474 target, and the log. The output intended for each of these streams is
29475 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
29477 Each stream record begins with a unique @dfn{prefix character} which
29478 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
29479 Syntax}). In addition to the prefix, each stream record contains a
29480 @code{@var{string-output}}. This is either raw text (with an implicit new
29481 line) or a quoted C string (which does not contain an implicit newline).
29484 @item "~" @var{string-output}
29485 The console output stream contains text that should be displayed in the
29486 CLI console window. It contains the textual responses to CLI commands.
29488 @item "@@" @var{string-output}
29489 The target output stream contains any textual output from the running
29490 target. This is only present when GDB's event loop is truly
29491 asynchronous, which is currently only the case for remote targets.
29493 @item "&" @var{string-output}
29494 The log stream contains debugging messages being produced by @value{GDBN}'s
29498 @node GDB/MI Async Records
29499 @subsection @sc{gdb/mi} Async Records
29501 @cindex async records in @sc{gdb/mi}
29502 @cindex @sc{gdb/mi}, async records
29503 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
29504 additional changes that have occurred. Those changes can either be a
29505 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
29506 target activity (e.g., target stopped).
29508 The following is the list of possible async records:
29512 @item *running,thread-id="@var{thread}"
29513 The target is now running. The @var{thread} field tells which
29514 specific thread is now running, and can be @samp{all} if all threads
29515 are running. The frontend should assume that no interaction with a
29516 running thread is possible after this notification is produced.
29517 The frontend should not assume that this notification is output
29518 only once for any command. @value{GDBN} may emit this notification
29519 several times, either for different threads, because it cannot resume
29520 all threads together, or even for a single thread, if the thread must
29521 be stepped though some code before letting it run freely.
29523 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
29524 The target has stopped. The @var{reason} field can have one of the
29528 @item breakpoint-hit
29529 A breakpoint was reached.
29530 @item watchpoint-trigger
29531 A watchpoint was triggered.
29532 @item read-watchpoint-trigger
29533 A read watchpoint was triggered.
29534 @item access-watchpoint-trigger
29535 An access watchpoint was triggered.
29536 @item function-finished
29537 An -exec-finish or similar CLI command was accomplished.
29538 @item location-reached
29539 An -exec-until or similar CLI command was accomplished.
29540 @item watchpoint-scope
29541 A watchpoint has gone out of scope.
29542 @item end-stepping-range
29543 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
29544 similar CLI command was accomplished.
29545 @item exited-signalled
29546 The inferior exited because of a signal.
29548 The inferior exited.
29549 @item exited-normally
29550 The inferior exited normally.
29551 @item signal-received
29552 A signal was received by the inferior.
29554 The inferior has stopped due to a library being loaded or unloaded.
29555 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
29556 set or when a @code{catch load} or @code{catch unload} catchpoint is
29557 in use (@pxref{Set Catchpoints}).
29559 The inferior has forked. This is reported when @code{catch fork}
29560 (@pxref{Set Catchpoints}) has been used.
29562 The inferior has vforked. This is reported in when @code{catch vfork}
29563 (@pxref{Set Catchpoints}) has been used.
29564 @item syscall-entry
29565 The inferior entered a system call. This is reported when @code{catch
29566 syscall} (@pxref{Set Catchpoints}) has been used.
29567 @item syscall-entry
29568 The inferior returned from a system call. This is reported when
29569 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
29571 The inferior called @code{exec}. This is reported when @code{catch exec}
29572 (@pxref{Set Catchpoints}) has been used.
29575 The @var{id} field identifies the thread that directly caused the stop
29576 -- for example by hitting a breakpoint. Depending on whether all-stop
29577 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
29578 stop all threads, or only the thread that directly triggered the stop.
29579 If all threads are stopped, the @var{stopped} field will have the
29580 value of @code{"all"}. Otherwise, the value of the @var{stopped}
29581 field will be a list of thread identifiers. Presently, this list will
29582 always include a single thread, but frontend should be prepared to see
29583 several threads in the list. The @var{core} field reports the
29584 processor core on which the stop event has happened. This field may be absent
29585 if such information is not available.
29587 @item =thread-group-added,id="@var{id}"
29588 @itemx =thread-group-removed,id="@var{id}"
29589 A thread group was either added or removed. The @var{id} field
29590 contains the @value{GDBN} identifier of the thread group. When a thread
29591 group is added, it generally might not be associated with a running
29592 process. When a thread group is removed, its id becomes invalid and
29593 cannot be used in any way.
29595 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
29596 A thread group became associated with a running program,
29597 either because the program was just started or the thread group
29598 was attached to a program. The @var{id} field contains the
29599 @value{GDBN} identifier of the thread group. The @var{pid} field
29600 contains process identifier, specific to the operating system.
29602 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
29603 A thread group is no longer associated with a running program,
29604 either because the program has exited, or because it was detached
29605 from. The @var{id} field contains the @value{GDBN} identifier of the
29606 thread group. @var{code} is the exit code of the inferior; it exists
29607 only when the inferior exited with some code.
29609 @item =thread-created,id="@var{id}",group-id="@var{gid}"
29610 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
29611 A thread either was created, or has exited. The @var{id} field
29612 contains the @value{GDBN} identifier of the thread. The @var{gid}
29613 field identifies the thread group this thread belongs to.
29615 @item =thread-selected,id="@var{id}"
29616 Informs that the selected thread was changed as result of the last
29617 command. This notification is not emitted as result of @code{-thread-select}
29618 command but is emitted whenever an MI command that is not documented
29619 to change the selected thread actually changes it. In particular,
29620 invoking, directly or indirectly (via user-defined command), the CLI
29621 @code{thread} command, will generate this notification.
29623 We suggest that in response to this notification, front ends
29624 highlight the selected thread and cause subsequent commands to apply to
29627 @item =library-loaded,...
29628 Reports that a new library file was loaded by the program. This
29629 notification has 4 fields---@var{id}, @var{target-name},
29630 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
29631 opaque identifier of the library. For remote debugging case,
29632 @var{target-name} and @var{host-name} fields give the name of the
29633 library file on the target, and on the host respectively. For native
29634 debugging, both those fields have the same value. The
29635 @var{symbols-loaded} field is emitted only for backward compatibility
29636 and should not be relied on to convey any useful information. The
29637 @var{thread-group} field, if present, specifies the id of the thread
29638 group in whose context the library was loaded. If the field is
29639 absent, it means the library was loaded in the context of all present
29642 @item =library-unloaded,...
29643 Reports that a library was unloaded by the program. This notification
29644 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
29645 the same meaning as for the @code{=library-loaded} notification.
29646 The @var{thread-group} field, if present, specifies the id of the
29647 thread group in whose context the library was unloaded. If the field is
29648 absent, it means the library was unloaded in the context of all present
29651 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
29652 @itemx =traceframe-changed,end
29653 Reports that the trace frame was changed and its new number is
29654 @var{tfnum}. The number of the tracepoint associated with this trace
29655 frame is @var{tpnum}.
29657 @item =tsv-created,name=@var{name},initial=@var{initial}
29658 Reports that the new trace state variable @var{name} is created with
29659 initial value @var{initial}.
29661 @item =tsv-deleted,name=@var{name}
29662 @itemx =tsv-deleted
29663 Reports that the trace state variable @var{name} is deleted or all
29664 trace state variables are deleted.
29666 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
29667 Reports that the trace state variable @var{name} is modified with
29668 the initial value @var{initial}. The current value @var{current} of
29669 trace state variable is optional and is reported if the current
29670 value of trace state variable is known.
29672 @item =breakpoint-created,bkpt=@{...@}
29673 @itemx =breakpoint-modified,bkpt=@{...@}
29674 @itemx =breakpoint-deleted,id=@var{number}
29675 Reports that a breakpoint was created, modified, or deleted,
29676 respectively. Only user-visible breakpoints are reported to the MI
29679 The @var{bkpt} argument is of the same form as returned by the various
29680 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
29681 @var{number} is the ordinal number of the breakpoint.
29683 Note that if a breakpoint is emitted in the result record of a
29684 command, then it will not also be emitted in an async record.
29686 @item =record-started,thread-group="@var{id}"
29687 @itemx =record-stopped,thread-group="@var{id}"
29688 Execution log recording was either started or stopped on an
29689 inferior. The @var{id} is the @value{GDBN} identifier of the thread
29690 group corresponding to the affected inferior.
29692 @item =cmd-param-changed,param=@var{param},value=@var{value}
29693 Reports that a parameter of the command @code{set @var{param}} is
29694 changed to @var{value}. In the multi-word @code{set} command,
29695 the @var{param} is the whole parameter list to @code{set} command.
29696 For example, In command @code{set check type on}, @var{param}
29697 is @code{check type} and @var{value} is @code{on}.
29699 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
29700 Reports that bytes from @var{addr} to @var{data} + @var{len} were
29701 written in an inferior. The @var{id} is the identifier of the
29702 thread group corresponding to the affected inferior. The optional
29703 @code{type="code"} part is reported if the memory written to holds
29707 @node GDB/MI Breakpoint Information
29708 @subsection @sc{gdb/mi} Breakpoint Information
29710 When @value{GDBN} reports information about a breakpoint, a
29711 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
29716 The breakpoint number. For a breakpoint that represents one location
29717 of a multi-location breakpoint, this will be a dotted pair, like
29721 The type of the breakpoint. For ordinary breakpoints this will be
29722 @samp{breakpoint}, but many values are possible.
29725 If the type of the breakpoint is @samp{catchpoint}, then this
29726 indicates the exact type of catchpoint.
29729 This is the breakpoint disposition---either @samp{del}, meaning that
29730 the breakpoint will be deleted at the next stop, or @samp{keep},
29731 meaning that the breakpoint will not be deleted.
29734 This indicates whether the breakpoint is enabled, in which case the
29735 value is @samp{y}, or disabled, in which case the value is @samp{n}.
29736 Note that this is not the same as the field @code{enable}.
29739 The address of the breakpoint. This may be a hexidecimal number,
29740 giving the address; or the string @samp{<PENDING>}, for a pending
29741 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
29742 multiple locations. This field will not be present if no address can
29743 be determined. For example, a watchpoint does not have an address.
29746 If known, the function in which the breakpoint appears.
29747 If not known, this field is not present.
29750 The name of the source file which contains this function, if known.
29751 If not known, this field is not present.
29754 The full file name of the source file which contains this function, if
29755 known. If not known, this field is not present.
29758 The line number at which this breakpoint appears, if known.
29759 If not known, this field is not present.
29762 If the source file is not known, this field may be provided. If
29763 provided, this holds the address of the breakpoint, possibly followed
29767 If this breakpoint is pending, this field is present and holds the
29768 text used to set the breakpoint, as entered by the user.
29771 Where this breakpoint's condition is evaluated, either @samp{host} or
29775 If this is a thread-specific breakpoint, then this identifies the
29776 thread in which the breakpoint can trigger.
29779 If this breakpoint is restricted to a particular Ada task, then this
29780 field will hold the task identifier.
29783 If the breakpoint is conditional, this is the condition expression.
29786 The ignore count of the breakpoint.
29789 The enable count of the breakpoint.
29791 @item traceframe-usage
29794 @item static-tracepoint-marker-string-id
29795 For a static tracepoint, the name of the static tracepoint marker.
29798 For a masked watchpoint, this is the mask.
29801 A tracepoint's pass count.
29803 @item original-location
29804 The location of the breakpoint as originally specified by the user.
29805 This field is optional.
29808 The number of times the breakpoint has been hit.
29811 This field is only given for tracepoints. This is either @samp{y},
29812 meaning that the tracepoint is installed, or @samp{n}, meaning that it
29816 Some extra data, the exact contents of which are type-dependent.
29820 For example, here is what the output of @code{-break-insert}
29821 (@pxref{GDB/MI Breakpoint Commands}) might be:
29824 -> -break-insert main
29825 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29826 enabled="y",addr="0x08048564",func="main",file="myprog.c",
29827 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
29832 @node GDB/MI Frame Information
29833 @subsection @sc{gdb/mi} Frame Information
29835 Response from many MI commands includes an information about stack
29836 frame. This information is a tuple that may have the following
29841 The level of the stack frame. The innermost frame has the level of
29842 zero. This field is always present.
29845 The name of the function corresponding to the frame. This field may
29846 be absent if @value{GDBN} is unable to determine the function name.
29849 The code address for the frame. This field is always present.
29852 The name of the source files that correspond to the frame's code
29853 address. This field may be absent.
29856 The source line corresponding to the frames' code address. This field
29860 The name of the binary file (either executable or shared library) the
29861 corresponds to the frame's code address. This field may be absent.
29865 @node GDB/MI Thread Information
29866 @subsection @sc{gdb/mi} Thread Information
29868 Whenever @value{GDBN} has to report an information about a thread, it
29869 uses a tuple with the following fields:
29873 The numeric id assigned to the thread by @value{GDBN}. This field is
29877 Target-specific string identifying the thread. This field is always present.
29880 Additional information about the thread provided by the target.
29881 It is supposed to be human-readable and not interpreted by the
29882 frontend. This field is optional.
29885 Either @samp{stopped} or @samp{running}, depending on whether the
29886 thread is presently running. This field is always present.
29889 The value of this field is an integer number of the processor core the
29890 thread was last seen on. This field is optional.
29893 @node GDB/MI Ada Exception Information
29894 @subsection @sc{gdb/mi} Ada Exception Information
29896 Whenever a @code{*stopped} record is emitted because the program
29897 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
29898 @value{GDBN} provides the name of the exception that was raised via
29899 the @code{exception-name} field.
29901 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29902 @node GDB/MI Simple Examples
29903 @section Simple Examples of @sc{gdb/mi} Interaction
29904 @cindex @sc{gdb/mi}, simple examples
29906 This subsection presents several simple examples of interaction using
29907 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
29908 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
29909 the output received from @sc{gdb/mi}.
29911 Note the line breaks shown in the examples are here only for
29912 readability, they don't appear in the real output.
29914 @subheading Setting a Breakpoint
29916 Setting a breakpoint generates synchronous output which contains detailed
29917 information of the breakpoint.
29920 -> -break-insert main
29921 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29922 enabled="y",addr="0x08048564",func="main",file="myprog.c",
29923 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
29928 @subheading Program Execution
29930 Program execution generates asynchronous records and MI gives the
29931 reason that execution stopped.
29937 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
29938 frame=@{addr="0x08048564",func="main",
29939 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
29940 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
29945 <- *stopped,reason="exited-normally"
29949 @subheading Quitting @value{GDBN}
29951 Quitting @value{GDBN} just prints the result class @samp{^exit}.
29959 Please note that @samp{^exit} is printed immediately, but it might
29960 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
29961 performs necessary cleanups, including killing programs being debugged
29962 or disconnecting from debug hardware, so the frontend should wait till
29963 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
29964 fails to exit in reasonable time.
29966 @subheading A Bad Command
29968 Here's what happens if you pass a non-existent command:
29972 <- ^error,msg="Undefined MI command: rubbish"
29977 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29978 @node GDB/MI Command Description Format
29979 @section @sc{gdb/mi} Command Description Format
29981 The remaining sections describe blocks of commands. Each block of
29982 commands is laid out in a fashion similar to this section.
29984 @subheading Motivation
29986 The motivation for this collection of commands.
29988 @subheading Introduction
29990 A brief introduction to this collection of commands as a whole.
29992 @subheading Commands
29994 For each command in the block, the following is described:
29996 @subsubheading Synopsis
29999 -command @var{args}@dots{}
30002 @subsubheading Result
30004 @subsubheading @value{GDBN} Command
30006 The corresponding @value{GDBN} CLI command(s), if any.
30008 @subsubheading Example
30010 Example(s) formatted for readability. Some of the described commands have
30011 not been implemented yet and these are labeled N.A.@: (not available).
30014 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30015 @node GDB/MI Breakpoint Commands
30016 @section @sc{gdb/mi} Breakpoint Commands
30018 @cindex breakpoint commands for @sc{gdb/mi}
30019 @cindex @sc{gdb/mi}, breakpoint commands
30020 This section documents @sc{gdb/mi} commands for manipulating
30023 @subheading The @code{-break-after} Command
30024 @findex -break-after
30026 @subsubheading Synopsis
30029 -break-after @var{number} @var{count}
30032 The breakpoint number @var{number} is not in effect until it has been
30033 hit @var{count} times. To see how this is reflected in the output of
30034 the @samp{-break-list} command, see the description of the
30035 @samp{-break-list} command below.
30037 @subsubheading @value{GDBN} Command
30039 The corresponding @value{GDBN} command is @samp{ignore}.
30041 @subsubheading Example
30046 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
30047 enabled="y",addr="0x000100d0",func="main",file="hello.c",
30048 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
30056 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30057 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30058 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30059 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30060 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30061 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30062 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30063 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30064 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30065 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
30070 @subheading The @code{-break-catch} Command
30071 @findex -break-catch
30074 @subheading The @code{-break-commands} Command
30075 @findex -break-commands
30077 @subsubheading Synopsis
30080 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
30083 Specifies the CLI commands that should be executed when breakpoint
30084 @var{number} is hit. The parameters @var{command1} to @var{commandN}
30085 are the commands. If no command is specified, any previously-set
30086 commands are cleared. @xref{Break Commands}. Typical use of this
30087 functionality is tracing a program, that is, printing of values of
30088 some variables whenever breakpoint is hit and then continuing.
30090 @subsubheading @value{GDBN} Command
30092 The corresponding @value{GDBN} command is @samp{commands}.
30094 @subsubheading Example
30099 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
30100 enabled="y",addr="0x000100d0",func="main",file="hello.c",
30101 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
30104 -break-commands 1 "print v" "continue"
30109 @subheading The @code{-break-condition} Command
30110 @findex -break-condition
30112 @subsubheading Synopsis
30115 -break-condition @var{number} @var{expr}
30118 Breakpoint @var{number} will stop the program only if the condition in
30119 @var{expr} is true. The condition becomes part of the
30120 @samp{-break-list} output (see the description of the @samp{-break-list}
30123 @subsubheading @value{GDBN} Command
30125 The corresponding @value{GDBN} command is @samp{condition}.
30127 @subsubheading Example
30131 -break-condition 1 1
30135 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30136 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30137 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30138 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30139 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30140 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30141 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30142 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30143 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30144 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
30148 @subheading The @code{-break-delete} Command
30149 @findex -break-delete
30151 @subsubheading Synopsis
30154 -break-delete ( @var{breakpoint} )+
30157 Delete the breakpoint(s) whose number(s) are specified in the argument
30158 list. This is obviously reflected in the breakpoint list.
30160 @subsubheading @value{GDBN} Command
30162 The corresponding @value{GDBN} command is @samp{delete}.
30164 @subsubheading Example
30172 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
30173 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30174 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30175 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30176 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30177 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30178 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30183 @subheading The @code{-break-disable} Command
30184 @findex -break-disable
30186 @subsubheading Synopsis
30189 -break-disable ( @var{breakpoint} )+
30192 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
30193 break list is now set to @samp{n} for the named @var{breakpoint}(s).
30195 @subsubheading @value{GDBN} Command
30197 The corresponding @value{GDBN} command is @samp{disable}.
30199 @subsubheading Example
30207 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30208 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30209 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30210 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30211 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30212 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30213 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30214 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
30215 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30216 line="5",thread-groups=["i1"],times="0"@}]@}
30220 @subheading The @code{-break-enable} Command
30221 @findex -break-enable
30223 @subsubheading Synopsis
30226 -break-enable ( @var{breakpoint} )+
30229 Enable (previously disabled) @var{breakpoint}(s).
30231 @subsubheading @value{GDBN} Command
30233 The corresponding @value{GDBN} command is @samp{enable}.
30235 @subsubheading Example
30243 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30244 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30245 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30246 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30247 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30248 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30249 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30250 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
30251 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30252 line="5",thread-groups=["i1"],times="0"@}]@}
30256 @subheading The @code{-break-info} Command
30257 @findex -break-info
30259 @subsubheading Synopsis
30262 -break-info @var{breakpoint}
30266 Get information about a single breakpoint.
30268 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
30269 Information}, for details on the format of each breakpoint in the
30272 @subsubheading @value{GDBN} Command
30274 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
30276 @subsubheading Example
30279 @subheading The @code{-break-insert} Command
30280 @findex -break-insert
30282 @subsubheading Synopsis
30285 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
30286 [ -c @var{condition} ] [ -i @var{ignore-count} ]
30287 [ -p @var{thread-id} ] [ @var{location} ]
30291 If specified, @var{location}, can be one of:
30298 @item filename:linenum
30299 @item filename:function
30303 The possible optional parameters of this command are:
30307 Insert a temporary breakpoint.
30309 Insert a hardware breakpoint.
30311 If @var{location} cannot be parsed (for example if it
30312 refers to unknown files or functions), create a pending
30313 breakpoint. Without this flag, @value{GDBN} will report
30314 an error, and won't create a breakpoint, if @var{location}
30317 Create a disabled breakpoint.
30319 Create a tracepoint. @xref{Tracepoints}. When this parameter
30320 is used together with @samp{-h}, a fast tracepoint is created.
30321 @item -c @var{condition}
30322 Make the breakpoint conditional on @var{condition}.
30323 @item -i @var{ignore-count}
30324 Initialize the @var{ignore-count}.
30325 @item -p @var{thread-id}
30326 Restrict the breakpoint to the specified @var{thread-id}.
30329 @subsubheading Result
30331 @xref{GDB/MI Breakpoint Information}, for details on the format of the
30332 resulting breakpoint.
30334 Note: this format is open to change.
30335 @c An out-of-band breakpoint instead of part of the result?
30337 @subsubheading @value{GDBN} Command
30339 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
30340 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
30342 @subsubheading Example
30347 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
30348 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
30351 -break-insert -t foo
30352 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
30353 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
30357 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30358 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30359 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30360 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30361 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30362 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30363 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30364 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30365 addr="0x0001072c", func="main",file="recursive2.c",
30366 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
30368 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
30369 addr="0x00010774",func="foo",file="recursive2.c",
30370 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
30373 @c -break-insert -r foo.*
30374 @c ~int foo(int, int);
30375 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
30376 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
30381 @subheading The @code{-dprintf-insert} Command
30382 @findex -dprintf-insert
30384 @subsubheading Synopsis
30387 -dprintf-insert [ -t ] [ -f ] [ -d ]
30388 [ -c @var{condition} ] [ -i @var{ignore-count} ]
30389 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
30394 If specified, @var{location}, can be one of:
30397 @item @var{function}
30400 @c @item @var{linenum}
30401 @item @var{filename}:@var{linenum}
30402 @item @var{filename}:function
30403 @item *@var{address}
30406 The possible optional parameters of this command are:
30410 Insert a temporary breakpoint.
30412 If @var{location} cannot be parsed (for example, if it
30413 refers to unknown files or functions), create a pending
30414 breakpoint. Without this flag, @value{GDBN} will report
30415 an error, and won't create a breakpoint, if @var{location}
30418 Create a disabled breakpoint.
30419 @item -c @var{condition}
30420 Make the breakpoint conditional on @var{condition}.
30421 @item -i @var{ignore-count}
30422 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
30423 to @var{ignore-count}.
30424 @item -p @var{thread-id}
30425 Restrict the breakpoint to the specified @var{thread-id}.
30428 @subsubheading Result
30430 @xref{GDB/MI Breakpoint Information}, for details on the format of the
30431 resulting breakpoint.
30433 @c An out-of-band breakpoint instead of part of the result?
30435 @subsubheading @value{GDBN} Command
30437 The corresponding @value{GDBN} command is @samp{dprintf}.
30439 @subsubheading Example
30443 4-dprintf-insert foo "At foo entry\n"
30444 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
30445 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
30446 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
30447 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
30448 original-location="foo"@}
30450 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
30451 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
30452 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
30453 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
30454 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
30455 original-location="mi-dprintf.c:26"@}
30459 @subheading The @code{-break-list} Command
30460 @findex -break-list
30462 @subsubheading Synopsis
30468 Displays the list of inserted breakpoints, showing the following fields:
30472 number of the breakpoint
30474 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
30476 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
30479 is the breakpoint enabled or no: @samp{y} or @samp{n}
30481 memory location at which the breakpoint is set
30483 logical location of the breakpoint, expressed by function name, file
30485 @item Thread-groups
30486 list of thread groups to which this breakpoint applies
30488 number of times the breakpoint has been hit
30491 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
30492 @code{body} field is an empty list.
30494 @subsubheading @value{GDBN} Command
30496 The corresponding @value{GDBN} command is @samp{info break}.
30498 @subsubheading Example
30503 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30504 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30505 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30506 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30507 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30508 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30509 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30510 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30511 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
30513 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
30514 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
30515 line="13",thread-groups=["i1"],times="0"@}]@}
30519 Here's an example of the result when there are no breakpoints:
30524 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
30525 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30526 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30527 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30528 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30529 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30530 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30535 @subheading The @code{-break-passcount} Command
30536 @findex -break-passcount
30538 @subsubheading Synopsis
30541 -break-passcount @var{tracepoint-number} @var{passcount}
30544 Set the passcount for tracepoint @var{tracepoint-number} to
30545 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
30546 is not a tracepoint, error is emitted. This corresponds to CLI
30547 command @samp{passcount}.
30549 @subheading The @code{-break-watch} Command
30550 @findex -break-watch
30552 @subsubheading Synopsis
30555 -break-watch [ -a | -r ]
30558 Create a watchpoint. With the @samp{-a} option it will create an
30559 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
30560 read from or on a write to the memory location. With the @samp{-r}
30561 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
30562 trigger only when the memory location is accessed for reading. Without
30563 either of the options, the watchpoint created is a regular watchpoint,
30564 i.e., it will trigger when the memory location is accessed for writing.
30565 @xref{Set Watchpoints, , Setting Watchpoints}.
30567 Note that @samp{-break-list} will report a single list of watchpoints and
30568 breakpoints inserted.
30570 @subsubheading @value{GDBN} Command
30572 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
30575 @subsubheading Example
30577 Setting a watchpoint on a variable in the @code{main} function:
30582 ^done,wpt=@{number="2",exp="x"@}
30587 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
30588 value=@{old="-268439212",new="55"@},
30589 frame=@{func="main",args=[],file="recursive2.c",
30590 fullname="/home/foo/bar/recursive2.c",line="5"@}
30594 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
30595 the program execution twice: first for the variable changing value, then
30596 for the watchpoint going out of scope.
30601 ^done,wpt=@{number="5",exp="C"@}
30606 *stopped,reason="watchpoint-trigger",
30607 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
30608 frame=@{func="callee4",args=[],
30609 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30610 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
30615 *stopped,reason="watchpoint-scope",wpnum="5",
30616 frame=@{func="callee3",args=[@{name="strarg",
30617 value="0x11940 \"A string argument.\""@}],
30618 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30619 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
30623 Listing breakpoints and watchpoints, at different points in the program
30624 execution. Note that once the watchpoint goes out of scope, it is
30630 ^done,wpt=@{number="2",exp="C"@}
30633 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30634 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30635 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30636 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30637 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30638 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30639 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30640 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30641 addr="0x00010734",func="callee4",
30642 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30643 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
30645 bkpt=@{number="2",type="watchpoint",disp="keep",
30646 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
30651 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
30652 value=@{old="-276895068",new="3"@},
30653 frame=@{func="callee4",args=[],
30654 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30655 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
30658 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30659 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30660 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30661 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30662 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30663 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30664 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30665 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30666 addr="0x00010734",func="callee4",
30667 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30668 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
30670 bkpt=@{number="2",type="watchpoint",disp="keep",
30671 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
30675 ^done,reason="watchpoint-scope",wpnum="2",
30676 frame=@{func="callee3",args=[@{name="strarg",
30677 value="0x11940 \"A string argument.\""@}],
30678 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30679 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
30682 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30683 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30684 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30685 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30686 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30687 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30688 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30689 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30690 addr="0x00010734",func="callee4",
30691 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30692 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
30693 thread-groups=["i1"],times="1"@}]@}
30698 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30699 @node GDB/MI Catchpoint Commands
30700 @section @sc{gdb/mi} Catchpoint Commands
30702 This section documents @sc{gdb/mi} commands for manipulating
30706 * Shared Library GDB/MI Catchpoint Commands::
30707 * Ada Exception GDB/MI Catchpoint Commands::
30710 @node Shared Library GDB/MI Catchpoint Commands
30711 @subsection Shared Library @sc{gdb/mi} Catchpoints
30713 @subheading The @code{-catch-load} Command
30714 @findex -catch-load
30716 @subsubheading Synopsis
30719 -catch-load [ -t ] [ -d ] @var{regexp}
30722 Add a catchpoint for library load events. If the @samp{-t} option is used,
30723 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
30724 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
30725 in a disabled state. The @samp{regexp} argument is a regular
30726 expression used to match the name of the loaded library.
30729 @subsubheading @value{GDBN} Command
30731 The corresponding @value{GDBN} command is @samp{catch load}.
30733 @subsubheading Example
30736 -catch-load -t foo.so
30737 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
30738 what="load of library matching foo.so",catch-type="load",times="0"@}
30743 @subheading The @code{-catch-unload} Command
30744 @findex -catch-unload
30746 @subsubheading Synopsis
30749 -catch-unload [ -t ] [ -d ] @var{regexp}
30752 Add a catchpoint for library unload events. If the @samp{-t} option is
30753 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
30754 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
30755 created in a disabled state. The @samp{regexp} argument is a regular
30756 expression used to match the name of the unloaded library.
30758 @subsubheading @value{GDBN} Command
30760 The corresponding @value{GDBN} command is @samp{catch unload}.
30762 @subsubheading Example
30765 -catch-unload -d bar.so
30766 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
30767 what="load of library matching bar.so",catch-type="unload",times="0"@}
30771 @node Ada Exception GDB/MI Catchpoint Commands
30772 @subsection Ada Exception @sc{gdb/mi} Catchpoints
30774 The following @sc{gdb/mi} commands can be used to create catchpoints
30775 that stop the execution when Ada exceptions are being raised.
30777 @subheading The @code{-catch-assert} Command
30778 @findex -catch-assert
30780 @subsubheading Synopsis
30783 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
30786 Add a catchpoint for failed Ada assertions.
30788 The possible optional parameters for this command are:
30791 @item -c @var{condition}
30792 Make the catchpoint conditional on @var{condition}.
30794 Create a disabled catchpoint.
30796 Create a temporary catchpoint.
30799 @subsubheading @value{GDBN} Command
30801 The corresponding @value{GDBN} command is @samp{catch assert}.
30803 @subsubheading Example
30807 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
30808 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
30809 thread-groups=["i1"],times="0",
30810 original-location="__gnat_debug_raise_assert_failure"@}
30814 @subheading The @code{-catch-exception} Command
30815 @findex -catch-exception
30817 @subsubheading Synopsis
30820 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
30824 Add a catchpoint stopping when Ada exceptions are raised.
30825 By default, the command stops the program when any Ada exception
30826 gets raised. But it is also possible, by using some of the
30827 optional parameters described below, to create more selective
30830 The possible optional parameters for this command are:
30833 @item -c @var{condition}
30834 Make the catchpoint conditional on @var{condition}.
30836 Create a disabled catchpoint.
30837 @item -e @var{exception-name}
30838 Only stop when @var{exception-name} is raised. This option cannot
30839 be used combined with @samp{-u}.
30841 Create a temporary catchpoint.
30843 Stop only when an unhandled exception gets raised. This option
30844 cannot be used combined with @samp{-e}.
30847 @subsubheading @value{GDBN} Command
30849 The corresponding @value{GDBN} commands are @samp{catch exception}
30850 and @samp{catch exception unhandled}.
30852 @subsubheading Example
30855 -catch-exception -e Program_Error
30856 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
30857 enabled="y",addr="0x0000000000404874",
30858 what="`Program_Error' Ada exception", thread-groups=["i1"],
30859 times="0",original-location="__gnat_debug_raise_exception"@}
30863 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30864 @node GDB/MI Program Context
30865 @section @sc{gdb/mi} Program Context
30867 @subheading The @code{-exec-arguments} Command
30868 @findex -exec-arguments
30871 @subsubheading Synopsis
30874 -exec-arguments @var{args}
30877 Set the inferior program arguments, to be used in the next
30880 @subsubheading @value{GDBN} Command
30882 The corresponding @value{GDBN} command is @samp{set args}.
30884 @subsubheading Example
30888 -exec-arguments -v word
30895 @subheading The @code{-exec-show-arguments} Command
30896 @findex -exec-show-arguments
30898 @subsubheading Synopsis
30901 -exec-show-arguments
30904 Print the arguments of the program.
30906 @subsubheading @value{GDBN} Command
30908 The corresponding @value{GDBN} command is @samp{show args}.
30910 @subsubheading Example
30915 @subheading The @code{-environment-cd} Command
30916 @findex -environment-cd
30918 @subsubheading Synopsis
30921 -environment-cd @var{pathdir}
30924 Set @value{GDBN}'s working directory.
30926 @subsubheading @value{GDBN} Command
30928 The corresponding @value{GDBN} command is @samp{cd}.
30930 @subsubheading Example
30934 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
30940 @subheading The @code{-environment-directory} Command
30941 @findex -environment-directory
30943 @subsubheading Synopsis
30946 -environment-directory [ -r ] [ @var{pathdir} ]+
30949 Add directories @var{pathdir} to beginning of search path for source files.
30950 If the @samp{-r} option is used, the search path is reset to the default
30951 search path. If directories @var{pathdir} are supplied in addition to the
30952 @samp{-r} option, the search path is first reset and then addition
30954 Multiple directories may be specified, separated by blanks. Specifying
30955 multiple directories in a single command
30956 results in the directories added to the beginning of the
30957 search path in the same order they were presented in the command.
30958 If blanks are needed as
30959 part of a directory name, double-quotes should be used around
30960 the name. In the command output, the path will show up separated
30961 by the system directory-separator character. The directory-separator
30962 character must not be used
30963 in any directory name.
30964 If no directories are specified, the current search path is displayed.
30966 @subsubheading @value{GDBN} Command
30968 The corresponding @value{GDBN} command is @samp{dir}.
30970 @subsubheading Example
30974 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
30975 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
30977 -environment-directory ""
30978 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
30980 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
30981 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
30983 -environment-directory -r
30984 ^done,source-path="$cdir:$cwd"
30989 @subheading The @code{-environment-path} Command
30990 @findex -environment-path
30992 @subsubheading Synopsis
30995 -environment-path [ -r ] [ @var{pathdir} ]+
30998 Add directories @var{pathdir} to beginning of search path for object files.
30999 If the @samp{-r} option is used, the search path is reset to the original
31000 search path that existed at gdb start-up. If directories @var{pathdir} are
31001 supplied in addition to the
31002 @samp{-r} option, the search path is first reset and then addition
31004 Multiple directories may be specified, separated by blanks. Specifying
31005 multiple directories in a single command
31006 results in the directories added to the beginning of the
31007 search path in the same order they were presented in the command.
31008 If blanks are needed as
31009 part of a directory name, double-quotes should be used around
31010 the name. In the command output, the path will show up separated
31011 by the system directory-separator character. The directory-separator
31012 character must not be used
31013 in any directory name.
31014 If no directories are specified, the current path is displayed.
31017 @subsubheading @value{GDBN} Command
31019 The corresponding @value{GDBN} command is @samp{path}.
31021 @subsubheading Example
31026 ^done,path="/usr/bin"
31028 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
31029 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
31031 -environment-path -r /usr/local/bin
31032 ^done,path="/usr/local/bin:/usr/bin"
31037 @subheading The @code{-environment-pwd} Command
31038 @findex -environment-pwd
31040 @subsubheading Synopsis
31046 Show the current working directory.
31048 @subsubheading @value{GDBN} Command
31050 The corresponding @value{GDBN} command is @samp{pwd}.
31052 @subsubheading Example
31057 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
31061 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31062 @node GDB/MI Thread Commands
31063 @section @sc{gdb/mi} Thread Commands
31066 @subheading The @code{-thread-info} Command
31067 @findex -thread-info
31069 @subsubheading Synopsis
31072 -thread-info [ @var{thread-id} ]
31075 Reports information about either a specific thread, if
31076 the @var{thread-id} parameter is present, or about all
31077 threads. When printing information about all threads,
31078 also reports the current thread.
31080 @subsubheading @value{GDBN} Command
31082 The @samp{info thread} command prints the same information
31085 @subsubheading Result
31087 The result is a list of threads. The following attributes are
31088 defined for a given thread:
31092 This field exists only for the current thread. It has the value @samp{*}.
31095 The identifier that @value{GDBN} uses to refer to the thread.
31098 The identifier that the target uses to refer to the thread.
31101 Extra information about the thread, in a target-specific format. This
31105 The name of the thread. If the user specified a name using the
31106 @code{thread name} command, then this name is given. Otherwise, if
31107 @value{GDBN} can extract the thread name from the target, then that
31108 name is given. If @value{GDBN} cannot find the thread name, then this
31112 The stack frame currently executing in the thread.
31115 The thread's state. The @samp{state} field may have the following
31120 The thread is stopped. Frame information is available for stopped
31124 The thread is running. There's no frame information for running
31130 If @value{GDBN} can find the CPU core on which this thread is running,
31131 then this field is the core identifier. This field is optional.
31135 @subsubheading Example
31140 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
31141 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
31142 args=[]@},state="running"@},
31143 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
31144 frame=@{level="0",addr="0x0804891f",func="foo",
31145 args=[@{name="i",value="10"@}],
31146 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
31147 state="running"@}],
31148 current-thread-id="1"
31152 @subheading The @code{-thread-list-ids} Command
31153 @findex -thread-list-ids
31155 @subsubheading Synopsis
31161 Produces a list of the currently known @value{GDBN} thread ids. At the
31162 end of the list it also prints the total number of such threads.
31164 This command is retained for historical reasons, the
31165 @code{-thread-info} command should be used instead.
31167 @subsubheading @value{GDBN} Command
31169 Part of @samp{info threads} supplies the same information.
31171 @subsubheading Example
31176 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
31177 current-thread-id="1",number-of-threads="3"
31182 @subheading The @code{-thread-select} Command
31183 @findex -thread-select
31185 @subsubheading Synopsis
31188 -thread-select @var{threadnum}
31191 Make @var{threadnum} the current thread. It prints the number of the new
31192 current thread, and the topmost frame for that thread.
31194 This command is deprecated in favor of explicitly using the
31195 @samp{--thread} option to each command.
31197 @subsubheading @value{GDBN} Command
31199 The corresponding @value{GDBN} command is @samp{thread}.
31201 @subsubheading Example
31208 *stopped,reason="end-stepping-range",thread-id="2",line="187",
31209 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
31213 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
31214 number-of-threads="3"
31217 ^done,new-thread-id="3",
31218 frame=@{level="0",func="vprintf",
31219 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
31220 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
31224 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31225 @node GDB/MI Ada Tasking Commands
31226 @section @sc{gdb/mi} Ada Tasking Commands
31228 @subheading The @code{-ada-task-info} Command
31229 @findex -ada-task-info
31231 @subsubheading Synopsis
31234 -ada-task-info [ @var{task-id} ]
31237 Reports information about either a specific Ada task, if the
31238 @var{task-id} parameter is present, or about all Ada tasks.
31240 @subsubheading @value{GDBN} Command
31242 The @samp{info tasks} command prints the same information
31243 about all Ada tasks (@pxref{Ada Tasks}).
31245 @subsubheading Result
31247 The result is a table of Ada tasks. The following columns are
31248 defined for each Ada task:
31252 This field exists only for the current thread. It has the value @samp{*}.
31255 The identifier that @value{GDBN} uses to refer to the Ada task.
31258 The identifier that the target uses to refer to the Ada task.
31261 The identifier of the thread corresponding to the Ada task.
31263 This field should always exist, as Ada tasks are always implemented
31264 on top of a thread. But if @value{GDBN} cannot find this corresponding
31265 thread for any reason, the field is omitted.
31268 This field exists only when the task was created by another task.
31269 In this case, it provides the ID of the parent task.
31272 The base priority of the task.
31275 The current state of the task. For a detailed description of the
31276 possible states, see @ref{Ada Tasks}.
31279 The name of the task.
31283 @subsubheading Example
31287 ^done,tasks=@{nr_rows="3",nr_cols="8",
31288 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
31289 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
31290 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
31291 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
31292 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
31293 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
31294 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
31295 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
31296 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
31297 state="Child Termination Wait",name="main_task"@}]@}
31301 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31302 @node GDB/MI Program Execution
31303 @section @sc{gdb/mi} Program Execution
31305 These are the asynchronous commands which generate the out-of-band
31306 record @samp{*stopped}. Currently @value{GDBN} only really executes
31307 asynchronously with remote targets and this interaction is mimicked in
31310 @subheading The @code{-exec-continue} Command
31311 @findex -exec-continue
31313 @subsubheading Synopsis
31316 -exec-continue [--reverse] [--all|--thread-group N]
31319 Resumes the execution of the inferior program, which will continue
31320 to execute until it reaches a debugger stop event. If the
31321 @samp{--reverse} option is specified, execution resumes in reverse until
31322 it reaches a stop event. Stop events may include
31325 breakpoints or watchpoints
31327 signals or exceptions
31329 the end of the process (or its beginning under @samp{--reverse})
31331 the end or beginning of a replay log if one is being used.
31333 In all-stop mode (@pxref{All-Stop
31334 Mode}), may resume only one thread, or all threads, depending on the
31335 value of the @samp{scheduler-locking} variable. If @samp{--all} is
31336 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
31337 ignored in all-stop mode. If the @samp{--thread-group} options is
31338 specified, then all threads in that thread group are resumed.
31340 @subsubheading @value{GDBN} Command
31342 The corresponding @value{GDBN} corresponding is @samp{continue}.
31344 @subsubheading Example
31351 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
31352 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
31358 @subheading The @code{-exec-finish} Command
31359 @findex -exec-finish
31361 @subsubheading Synopsis
31364 -exec-finish [--reverse]
31367 Resumes the execution of the inferior program until the current
31368 function is exited. Displays the results returned by the function.
31369 If the @samp{--reverse} option is specified, resumes the reverse
31370 execution of the inferior program until the point where current
31371 function was called.
31373 @subsubheading @value{GDBN} Command
31375 The corresponding @value{GDBN} command is @samp{finish}.
31377 @subsubheading Example
31379 Function returning @code{void}.
31386 *stopped,reason="function-finished",frame=@{func="main",args=[],
31387 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
31391 Function returning other than @code{void}. The name of the internal
31392 @value{GDBN} variable storing the result is printed, together with the
31399 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
31400 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
31401 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31402 gdb-result-var="$1",return-value="0"
31407 @subheading The @code{-exec-interrupt} Command
31408 @findex -exec-interrupt
31410 @subsubheading Synopsis
31413 -exec-interrupt [--all|--thread-group N]
31416 Interrupts the background execution of the target. Note how the token
31417 associated with the stop message is the one for the execution command
31418 that has been interrupted. The token for the interrupt itself only
31419 appears in the @samp{^done} output. If the user is trying to
31420 interrupt a non-running program, an error message will be printed.
31422 Note that when asynchronous execution is enabled, this command is
31423 asynchronous just like other execution commands. That is, first the
31424 @samp{^done} response will be printed, and the target stop will be
31425 reported after that using the @samp{*stopped} notification.
31427 In non-stop mode, only the context thread is interrupted by default.
31428 All threads (in all inferiors) will be interrupted if the
31429 @samp{--all} option is specified. If the @samp{--thread-group}
31430 option is specified, all threads in that group will be interrupted.
31432 @subsubheading @value{GDBN} Command
31434 The corresponding @value{GDBN} command is @samp{interrupt}.
31436 @subsubheading Example
31447 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
31448 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
31449 fullname="/home/foo/bar/try.c",line="13"@}
31454 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
31458 @subheading The @code{-exec-jump} Command
31461 @subsubheading Synopsis
31464 -exec-jump @var{location}
31467 Resumes execution of the inferior program at the location specified by
31468 parameter. @xref{Specify Location}, for a description of the
31469 different forms of @var{location}.
31471 @subsubheading @value{GDBN} Command
31473 The corresponding @value{GDBN} command is @samp{jump}.
31475 @subsubheading Example
31478 -exec-jump foo.c:10
31479 *running,thread-id="all"
31484 @subheading The @code{-exec-next} Command
31487 @subsubheading Synopsis
31490 -exec-next [--reverse]
31493 Resumes execution of the inferior program, stopping when the beginning
31494 of the next source line is reached.
31496 If the @samp{--reverse} option is specified, resumes reverse execution
31497 of the inferior program, stopping at the beginning of the previous
31498 source line. If you issue this command on the first line of a
31499 function, it will take you back to the caller of that function, to the
31500 source line where the function was called.
31503 @subsubheading @value{GDBN} Command
31505 The corresponding @value{GDBN} command is @samp{next}.
31507 @subsubheading Example
31513 *stopped,reason="end-stepping-range",line="8",file="hello.c"
31518 @subheading The @code{-exec-next-instruction} Command
31519 @findex -exec-next-instruction
31521 @subsubheading Synopsis
31524 -exec-next-instruction [--reverse]
31527 Executes one machine instruction. If the instruction is a function
31528 call, continues until the function returns. If the program stops at an
31529 instruction in the middle of a source line, the address will be
31532 If the @samp{--reverse} option is specified, resumes reverse execution
31533 of the inferior program, stopping at the previous instruction. If the
31534 previously executed instruction was a return from another function,
31535 it will continue to execute in reverse until the call to that function
31536 (from the current stack frame) is reached.
31538 @subsubheading @value{GDBN} Command
31540 The corresponding @value{GDBN} command is @samp{nexti}.
31542 @subsubheading Example
31546 -exec-next-instruction
31550 *stopped,reason="end-stepping-range",
31551 addr="0x000100d4",line="5",file="hello.c"
31556 @subheading The @code{-exec-return} Command
31557 @findex -exec-return
31559 @subsubheading Synopsis
31565 Makes current function return immediately. Doesn't execute the inferior.
31566 Displays the new current frame.
31568 @subsubheading @value{GDBN} Command
31570 The corresponding @value{GDBN} command is @samp{return}.
31572 @subsubheading Example
31576 200-break-insert callee4
31577 200^done,bkpt=@{number="1",addr="0x00010734",
31578 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
31583 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
31584 frame=@{func="callee4",args=[],
31585 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31586 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
31592 111^done,frame=@{level="0",func="callee3",
31593 args=[@{name="strarg",
31594 value="0x11940 \"A string argument.\""@}],
31595 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31596 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
31601 @subheading The @code{-exec-run} Command
31604 @subsubheading Synopsis
31607 -exec-run [ --all | --thread-group N ] [ --start ]
31610 Starts execution of the inferior from the beginning. The inferior
31611 executes until either a breakpoint is encountered or the program
31612 exits. In the latter case the output will include an exit code, if
31613 the program has exited exceptionally.
31615 When neither the @samp{--all} nor the @samp{--thread-group} option
31616 is specified, the current inferior is started. If the
31617 @samp{--thread-group} option is specified, it should refer to a thread
31618 group of type @samp{process}, and that thread group will be started.
31619 If the @samp{--all} option is specified, then all inferiors will be started.
31621 Using the @samp{--start} option instructs the debugger to stop
31622 the execution at the start of the inferior's main subprogram,
31623 following the same behavior as the @code{start} command
31624 (@pxref{Starting}).
31626 @subsubheading @value{GDBN} Command
31628 The corresponding @value{GDBN} command is @samp{run}.
31630 @subsubheading Examples
31635 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
31640 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
31641 frame=@{func="main",args=[],file="recursive2.c",
31642 fullname="/home/foo/bar/recursive2.c",line="4"@}
31647 Program exited normally:
31655 *stopped,reason="exited-normally"
31660 Program exited exceptionally:
31668 *stopped,reason="exited",exit-code="01"
31672 Another way the program can terminate is if it receives a signal such as
31673 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
31677 *stopped,reason="exited-signalled",signal-name="SIGINT",
31678 signal-meaning="Interrupt"
31682 @c @subheading -exec-signal
31685 @subheading The @code{-exec-step} Command
31688 @subsubheading Synopsis
31691 -exec-step [--reverse]
31694 Resumes execution of the inferior program, stopping when the beginning
31695 of the next source line is reached, if the next source line is not a
31696 function call. If it is, stop at the first instruction of the called
31697 function. If the @samp{--reverse} option is specified, resumes reverse
31698 execution of the inferior program, stopping at the beginning of the
31699 previously executed source line.
31701 @subsubheading @value{GDBN} Command
31703 The corresponding @value{GDBN} command is @samp{step}.
31705 @subsubheading Example
31707 Stepping into a function:
31713 *stopped,reason="end-stepping-range",
31714 frame=@{func="foo",args=[@{name="a",value="10"@},
31715 @{name="b",value="0"@}],file="recursive2.c",
31716 fullname="/home/foo/bar/recursive2.c",line="11"@}
31726 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
31731 @subheading The @code{-exec-step-instruction} Command
31732 @findex -exec-step-instruction
31734 @subsubheading Synopsis
31737 -exec-step-instruction [--reverse]
31740 Resumes the inferior which executes one machine instruction. If the
31741 @samp{--reverse} option is specified, resumes reverse execution of the
31742 inferior program, stopping at the previously executed instruction.
31743 The output, once @value{GDBN} has stopped, will vary depending on
31744 whether we have stopped in the middle of a source line or not. In the
31745 former case, the address at which the program stopped will be printed
31748 @subsubheading @value{GDBN} Command
31750 The corresponding @value{GDBN} command is @samp{stepi}.
31752 @subsubheading Example
31756 -exec-step-instruction
31760 *stopped,reason="end-stepping-range",
31761 frame=@{func="foo",args=[],file="try.c",
31762 fullname="/home/foo/bar/try.c",line="10"@}
31764 -exec-step-instruction
31768 *stopped,reason="end-stepping-range",
31769 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
31770 fullname="/home/foo/bar/try.c",line="10"@}
31775 @subheading The @code{-exec-until} Command
31776 @findex -exec-until
31778 @subsubheading Synopsis
31781 -exec-until [ @var{location} ]
31784 Executes the inferior until the @var{location} specified in the
31785 argument is reached. If there is no argument, the inferior executes
31786 until a source line greater than the current one is reached. The
31787 reason for stopping in this case will be @samp{location-reached}.
31789 @subsubheading @value{GDBN} Command
31791 The corresponding @value{GDBN} command is @samp{until}.
31793 @subsubheading Example
31797 -exec-until recursive2.c:6
31801 *stopped,reason="location-reached",frame=@{func="main",args=[],
31802 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
31807 @subheading -file-clear
31808 Is this going away????
31811 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31812 @node GDB/MI Stack Manipulation
31813 @section @sc{gdb/mi} Stack Manipulation Commands
31815 @subheading The @code{-enable-frame-filters} Command
31816 @findex -enable-frame-filters
31819 -enable-frame-filters
31822 @value{GDBN} allows Python-based frame filters to affect the output of
31823 the MI commands relating to stack traces. As there is no way to
31824 implement this in a fully backward-compatible way, a front end must
31825 request that this functionality be enabled.
31827 Once enabled, this feature cannot be disabled.
31829 Note that if Python support has not been compiled into @value{GDBN},
31830 this command will still succeed (and do nothing).
31832 @subheading The @code{-stack-info-frame} Command
31833 @findex -stack-info-frame
31835 @subsubheading Synopsis
31841 Get info on the selected frame.
31843 @subsubheading @value{GDBN} Command
31845 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
31846 (without arguments).
31848 @subsubheading Example
31853 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
31854 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31855 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
31859 @subheading The @code{-stack-info-depth} Command
31860 @findex -stack-info-depth
31862 @subsubheading Synopsis
31865 -stack-info-depth [ @var{max-depth} ]
31868 Return the depth of the stack. If the integer argument @var{max-depth}
31869 is specified, do not count beyond @var{max-depth} frames.
31871 @subsubheading @value{GDBN} Command
31873 There's no equivalent @value{GDBN} command.
31875 @subsubheading Example
31877 For a stack with frame levels 0 through 11:
31884 -stack-info-depth 4
31887 -stack-info-depth 12
31890 -stack-info-depth 11
31893 -stack-info-depth 13
31898 @anchor{-stack-list-arguments}
31899 @subheading The @code{-stack-list-arguments} Command
31900 @findex -stack-list-arguments
31902 @subsubheading Synopsis
31905 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
31906 [ @var{low-frame} @var{high-frame} ]
31909 Display a list of the arguments for the frames between @var{low-frame}
31910 and @var{high-frame} (inclusive). If @var{low-frame} and
31911 @var{high-frame} are not provided, list the arguments for the whole
31912 call stack. If the two arguments are equal, show the single frame
31913 at the corresponding level. It is an error if @var{low-frame} is
31914 larger than the actual number of frames. On the other hand,
31915 @var{high-frame} may be larger than the actual number of frames, in
31916 which case only existing frames will be returned.
31918 If @var{print-values} is 0 or @code{--no-values}, print only the names of
31919 the variables; if it is 1 or @code{--all-values}, print also their
31920 values; and if it is 2 or @code{--simple-values}, print the name,
31921 type and value for simple data types, and the name and type for arrays,
31922 structures and unions. If the option @code{--no-frame-filters} is
31923 supplied, then Python frame filters will not be executed.
31925 If the @code{--skip-unavailable} option is specified, arguments that
31926 are not available are not listed. Partially available arguments
31927 are still displayed, however.
31929 Use of this command to obtain arguments in a single frame is
31930 deprecated in favor of the @samp{-stack-list-variables} command.
31932 @subsubheading @value{GDBN} Command
31934 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
31935 @samp{gdb_get_args} command which partially overlaps with the
31936 functionality of @samp{-stack-list-arguments}.
31938 @subsubheading Example
31945 frame=@{level="0",addr="0x00010734",func="callee4",
31946 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31947 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
31948 frame=@{level="1",addr="0x0001076c",func="callee3",
31949 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31950 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
31951 frame=@{level="2",addr="0x0001078c",func="callee2",
31952 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31953 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
31954 frame=@{level="3",addr="0x000107b4",func="callee1",
31955 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31956 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
31957 frame=@{level="4",addr="0x000107e0",func="main",
31958 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31959 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
31961 -stack-list-arguments 0
31964 frame=@{level="0",args=[]@},
31965 frame=@{level="1",args=[name="strarg"]@},
31966 frame=@{level="2",args=[name="intarg",name="strarg"]@},
31967 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
31968 frame=@{level="4",args=[]@}]
31970 -stack-list-arguments 1
31973 frame=@{level="0",args=[]@},
31975 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
31976 frame=@{level="2",args=[
31977 @{name="intarg",value="2"@},
31978 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
31979 @{frame=@{level="3",args=[
31980 @{name="intarg",value="2"@},
31981 @{name="strarg",value="0x11940 \"A string argument.\""@},
31982 @{name="fltarg",value="3.5"@}]@},
31983 frame=@{level="4",args=[]@}]
31985 -stack-list-arguments 0 2 2
31986 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
31988 -stack-list-arguments 1 2 2
31989 ^done,stack-args=[frame=@{level="2",
31990 args=[@{name="intarg",value="2"@},
31991 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
31995 @c @subheading -stack-list-exception-handlers
31998 @anchor{-stack-list-frames}
31999 @subheading The @code{-stack-list-frames} Command
32000 @findex -stack-list-frames
32002 @subsubheading Synopsis
32005 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
32008 List the frames currently on the stack. For each frame it displays the
32013 The frame number, 0 being the topmost frame, i.e., the innermost function.
32015 The @code{$pc} value for that frame.
32019 File name of the source file where the function lives.
32020 @item @var{fullname}
32021 The full file name of the source file where the function lives.
32023 Line number corresponding to the @code{$pc}.
32025 The shared library where this function is defined. This is only given
32026 if the frame's function is not known.
32029 If invoked without arguments, this command prints a backtrace for the
32030 whole stack. If given two integer arguments, it shows the frames whose
32031 levels are between the two arguments (inclusive). If the two arguments
32032 are equal, it shows the single frame at the corresponding level. It is
32033 an error if @var{low-frame} is larger than the actual number of
32034 frames. On the other hand, @var{high-frame} may be larger than the
32035 actual number of frames, in which case only existing frames will be
32036 returned. If the option @code{--no-frame-filters} is supplied, then
32037 Python frame filters will not be executed.
32039 @subsubheading @value{GDBN} Command
32041 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
32043 @subsubheading Example
32045 Full stack backtrace:
32051 [frame=@{level="0",addr="0x0001076c",func="foo",
32052 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
32053 frame=@{level="1",addr="0x000107a4",func="foo",
32054 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
32055 frame=@{level="2",addr="0x000107a4",func="foo",
32056 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
32057 frame=@{level="3",addr="0x000107a4",func="foo",
32058 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
32059 frame=@{level="4",addr="0x000107a4",func="foo",
32060 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
32061 frame=@{level="5",addr="0x000107a4",func="foo",
32062 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
32063 frame=@{level="6",addr="0x000107a4",func="foo",
32064 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
32065 frame=@{level="7",addr="0x000107a4",func="foo",
32066 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
32067 frame=@{level="8",addr="0x000107a4",func="foo",
32068 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
32069 frame=@{level="9",addr="0x000107a4",func="foo",
32070 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
32071 frame=@{level="10",addr="0x000107a4",func="foo",
32072 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
32073 frame=@{level="11",addr="0x00010738",func="main",
32074 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
32078 Show frames between @var{low_frame} and @var{high_frame}:
32082 -stack-list-frames 3 5
32084 [frame=@{level="3",addr="0x000107a4",func="foo",
32085 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
32086 frame=@{level="4",addr="0x000107a4",func="foo",
32087 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
32088 frame=@{level="5",addr="0x000107a4",func="foo",
32089 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
32093 Show a single frame:
32097 -stack-list-frames 3 3
32099 [frame=@{level="3",addr="0x000107a4",func="foo",
32100 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
32105 @subheading The @code{-stack-list-locals} Command
32106 @findex -stack-list-locals
32107 @anchor{-stack-list-locals}
32109 @subsubheading Synopsis
32112 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
32115 Display the local variable names for the selected frame. If
32116 @var{print-values} is 0 or @code{--no-values}, print only the names of
32117 the variables; if it is 1 or @code{--all-values}, print also their
32118 values; and if it is 2 or @code{--simple-values}, print the name,
32119 type and value for simple data types, and the name and type for arrays,
32120 structures and unions. In this last case, a frontend can immediately
32121 display the value of simple data types and create variable objects for
32122 other data types when the user wishes to explore their values in
32123 more detail. If the option @code{--no-frame-filters} is supplied, then
32124 Python frame filters will not be executed.
32126 If the @code{--skip-unavailable} option is specified, local variables
32127 that are not available are not listed. Partially available local
32128 variables are still displayed, however.
32130 This command is deprecated in favor of the
32131 @samp{-stack-list-variables} command.
32133 @subsubheading @value{GDBN} Command
32135 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
32137 @subsubheading Example
32141 -stack-list-locals 0
32142 ^done,locals=[name="A",name="B",name="C"]
32144 -stack-list-locals --all-values
32145 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
32146 @{name="C",value="@{1, 2, 3@}"@}]
32147 -stack-list-locals --simple-values
32148 ^done,locals=[@{name="A",type="int",value="1"@},
32149 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
32153 @anchor{-stack-list-variables}
32154 @subheading The @code{-stack-list-variables} Command
32155 @findex -stack-list-variables
32157 @subsubheading Synopsis
32160 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
32163 Display the names of local variables and function arguments for the selected frame. If
32164 @var{print-values} is 0 or @code{--no-values}, print only the names of
32165 the variables; if it is 1 or @code{--all-values}, print also their
32166 values; and if it is 2 or @code{--simple-values}, print the name,
32167 type and value for simple data types, and the name and type for arrays,
32168 structures and unions. If the option @code{--no-frame-filters} is
32169 supplied, then Python frame filters will not be executed.
32171 If the @code{--skip-unavailable} option is specified, local variables
32172 and arguments that are not available are not listed. Partially
32173 available arguments and local variables are still displayed, however.
32175 @subsubheading Example
32179 -stack-list-variables --thread 1 --frame 0 --all-values
32180 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
32185 @subheading The @code{-stack-select-frame} Command
32186 @findex -stack-select-frame
32188 @subsubheading Synopsis
32191 -stack-select-frame @var{framenum}
32194 Change the selected frame. Select a different frame @var{framenum} on
32197 This command in deprecated in favor of passing the @samp{--frame}
32198 option to every command.
32200 @subsubheading @value{GDBN} Command
32202 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
32203 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
32205 @subsubheading Example
32209 -stack-select-frame 2
32214 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32215 @node GDB/MI Variable Objects
32216 @section @sc{gdb/mi} Variable Objects
32220 @subheading Motivation for Variable Objects in @sc{gdb/mi}
32222 For the implementation of a variable debugger window (locals, watched
32223 expressions, etc.), we are proposing the adaptation of the existing code
32224 used by @code{Insight}.
32226 The two main reasons for that are:
32230 It has been proven in practice (it is already on its second generation).
32233 It will shorten development time (needless to say how important it is
32237 The original interface was designed to be used by Tcl code, so it was
32238 slightly changed so it could be used through @sc{gdb/mi}. This section
32239 describes the @sc{gdb/mi} operations that will be available and gives some
32240 hints about their use.
32242 @emph{Note}: In addition to the set of operations described here, we
32243 expect the @sc{gui} implementation of a variable window to require, at
32244 least, the following operations:
32247 @item @code{-gdb-show} @code{output-radix}
32248 @item @code{-stack-list-arguments}
32249 @item @code{-stack-list-locals}
32250 @item @code{-stack-select-frame}
32255 @subheading Introduction to Variable Objects
32257 @cindex variable objects in @sc{gdb/mi}
32259 Variable objects are "object-oriented" MI interface for examining and
32260 changing values of expressions. Unlike some other MI interfaces that
32261 work with expressions, variable objects are specifically designed for
32262 simple and efficient presentation in the frontend. A variable object
32263 is identified by string name. When a variable object is created, the
32264 frontend specifies the expression for that variable object. The
32265 expression can be a simple variable, or it can be an arbitrary complex
32266 expression, and can even involve CPU registers. After creating a
32267 variable object, the frontend can invoke other variable object
32268 operations---for example to obtain or change the value of a variable
32269 object, or to change display format.
32271 Variable objects have hierarchical tree structure. Any variable object
32272 that corresponds to a composite type, such as structure in C, has
32273 a number of child variable objects, for example corresponding to each
32274 element of a structure. A child variable object can itself have
32275 children, recursively. Recursion ends when we reach
32276 leaf variable objects, which always have built-in types. Child variable
32277 objects are created only by explicit request, so if a frontend
32278 is not interested in the children of a particular variable object, no
32279 child will be created.
32281 For a leaf variable object it is possible to obtain its value as a
32282 string, or set the value from a string. String value can be also
32283 obtained for a non-leaf variable object, but it's generally a string
32284 that only indicates the type of the object, and does not list its
32285 contents. Assignment to a non-leaf variable object is not allowed.
32287 A frontend does not need to read the values of all variable objects each time
32288 the program stops. Instead, MI provides an update command that lists all
32289 variable objects whose values has changed since the last update
32290 operation. This considerably reduces the amount of data that must
32291 be transferred to the frontend. As noted above, children variable
32292 objects are created on demand, and only leaf variable objects have a
32293 real value. As result, gdb will read target memory only for leaf
32294 variables that frontend has created.
32296 The automatic update is not always desirable. For example, a frontend
32297 might want to keep a value of some expression for future reference,
32298 and never update it. For another example, fetching memory is
32299 relatively slow for embedded targets, so a frontend might want
32300 to disable automatic update for the variables that are either not
32301 visible on the screen, or ``closed''. This is possible using so
32302 called ``frozen variable objects''. Such variable objects are never
32303 implicitly updated.
32305 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
32306 fixed variable object, the expression is parsed when the variable
32307 object is created, including associating identifiers to specific
32308 variables. The meaning of expression never changes. For a floating
32309 variable object the values of variables whose names appear in the
32310 expressions are re-evaluated every time in the context of the current
32311 frame. Consider this example:
32316 struct work_state state;
32323 If a fixed variable object for the @code{state} variable is created in
32324 this function, and we enter the recursive call, the variable
32325 object will report the value of @code{state} in the top-level
32326 @code{do_work} invocation. On the other hand, a floating variable
32327 object will report the value of @code{state} in the current frame.
32329 If an expression specified when creating a fixed variable object
32330 refers to a local variable, the variable object becomes bound to the
32331 thread and frame in which the variable object is created. When such
32332 variable object is updated, @value{GDBN} makes sure that the
32333 thread/frame combination the variable object is bound to still exists,
32334 and re-evaluates the variable object in context of that thread/frame.
32336 The following is the complete set of @sc{gdb/mi} operations defined to
32337 access this functionality:
32339 @multitable @columnfractions .4 .6
32340 @item @strong{Operation}
32341 @tab @strong{Description}
32343 @item @code{-enable-pretty-printing}
32344 @tab enable Python-based pretty-printing
32345 @item @code{-var-create}
32346 @tab create a variable object
32347 @item @code{-var-delete}
32348 @tab delete the variable object and/or its children
32349 @item @code{-var-set-format}
32350 @tab set the display format of this variable
32351 @item @code{-var-show-format}
32352 @tab show the display format of this variable
32353 @item @code{-var-info-num-children}
32354 @tab tells how many children this object has
32355 @item @code{-var-list-children}
32356 @tab return a list of the object's children
32357 @item @code{-var-info-type}
32358 @tab show the type of this variable object
32359 @item @code{-var-info-expression}
32360 @tab print parent-relative expression that this variable object represents
32361 @item @code{-var-info-path-expression}
32362 @tab print full expression that this variable object represents
32363 @item @code{-var-show-attributes}
32364 @tab is this variable editable? does it exist here?
32365 @item @code{-var-evaluate-expression}
32366 @tab get the value of this variable
32367 @item @code{-var-assign}
32368 @tab set the value of this variable
32369 @item @code{-var-update}
32370 @tab update the variable and its children
32371 @item @code{-var-set-frozen}
32372 @tab set frozeness attribute
32373 @item @code{-var-set-update-range}
32374 @tab set range of children to display on update
32377 In the next subsection we describe each operation in detail and suggest
32378 how it can be used.
32380 @subheading Description And Use of Operations on Variable Objects
32382 @subheading The @code{-enable-pretty-printing} Command
32383 @findex -enable-pretty-printing
32386 -enable-pretty-printing
32389 @value{GDBN} allows Python-based visualizers to affect the output of the
32390 MI variable object commands. However, because there was no way to
32391 implement this in a fully backward-compatible way, a front end must
32392 request that this functionality be enabled.
32394 Once enabled, this feature cannot be disabled.
32396 Note that if Python support has not been compiled into @value{GDBN},
32397 this command will still succeed (and do nothing).
32399 This feature is currently (as of @value{GDBN} 7.0) experimental, and
32400 may work differently in future versions of @value{GDBN}.
32402 @subheading The @code{-var-create} Command
32403 @findex -var-create
32405 @subsubheading Synopsis
32408 -var-create @{@var{name} | "-"@}
32409 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
32412 This operation creates a variable object, which allows the monitoring of
32413 a variable, the result of an expression, a memory cell or a CPU
32416 The @var{name} parameter is the string by which the object can be
32417 referenced. It must be unique. If @samp{-} is specified, the varobj
32418 system will generate a string ``varNNNNNN'' automatically. It will be
32419 unique provided that one does not specify @var{name} of that format.
32420 The command fails if a duplicate name is found.
32422 The frame under which the expression should be evaluated can be
32423 specified by @var{frame-addr}. A @samp{*} indicates that the current
32424 frame should be used. A @samp{@@} indicates that a floating variable
32425 object must be created.
32427 @var{expression} is any expression valid on the current language set (must not
32428 begin with a @samp{*}), or one of the following:
32432 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
32435 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
32438 @samp{$@var{regname}} --- a CPU register name
32441 @cindex dynamic varobj
32442 A varobj's contents may be provided by a Python-based pretty-printer. In this
32443 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
32444 have slightly different semantics in some cases. If the
32445 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
32446 will never create a dynamic varobj. This ensures backward
32447 compatibility for existing clients.
32449 @subsubheading Result
32451 This operation returns attributes of the newly-created varobj. These
32456 The name of the varobj.
32459 The number of children of the varobj. This number is not necessarily
32460 reliable for a dynamic varobj. Instead, you must examine the
32461 @samp{has_more} attribute.
32464 The varobj's scalar value. For a varobj whose type is some sort of
32465 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
32466 will not be interesting.
32469 The varobj's type. This is a string representation of the type, as
32470 would be printed by the @value{GDBN} CLI. If @samp{print object}
32471 (@pxref{Print Settings, set print object}) is set to @code{on}, the
32472 @emph{actual} (derived) type of the object is shown rather than the
32473 @emph{declared} one.
32476 If a variable object is bound to a specific thread, then this is the
32477 thread's identifier.
32480 For a dynamic varobj, this indicates whether there appear to be any
32481 children available. For a non-dynamic varobj, this will be 0.
32484 This attribute will be present and have the value @samp{1} if the
32485 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
32486 then this attribute will not be present.
32489 A dynamic varobj can supply a display hint to the front end. The
32490 value comes directly from the Python pretty-printer object's
32491 @code{display_hint} method. @xref{Pretty Printing API}.
32494 Typical output will look like this:
32497 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
32498 has_more="@var{has_more}"
32502 @subheading The @code{-var-delete} Command
32503 @findex -var-delete
32505 @subsubheading Synopsis
32508 -var-delete [ -c ] @var{name}
32511 Deletes a previously created variable object and all of its children.
32512 With the @samp{-c} option, just deletes the children.
32514 Returns an error if the object @var{name} is not found.
32517 @subheading The @code{-var-set-format} Command
32518 @findex -var-set-format
32520 @subsubheading Synopsis
32523 -var-set-format @var{name} @var{format-spec}
32526 Sets the output format for the value of the object @var{name} to be
32529 @anchor{-var-set-format}
32530 The syntax for the @var{format-spec} is as follows:
32533 @var{format-spec} @expansion{}
32534 @{binary | decimal | hexadecimal | octal | natural@}
32537 The natural format is the default format choosen automatically
32538 based on the variable type (like decimal for an @code{int}, hex
32539 for pointers, etc.).
32541 For a variable with children, the format is set only on the
32542 variable itself, and the children are not affected.
32544 @subheading The @code{-var-show-format} Command
32545 @findex -var-show-format
32547 @subsubheading Synopsis
32550 -var-show-format @var{name}
32553 Returns the format used to display the value of the object @var{name}.
32556 @var{format} @expansion{}
32561 @subheading The @code{-var-info-num-children} Command
32562 @findex -var-info-num-children
32564 @subsubheading Synopsis
32567 -var-info-num-children @var{name}
32570 Returns the number of children of a variable object @var{name}:
32576 Note that this number is not completely reliable for a dynamic varobj.
32577 It will return the current number of children, but more children may
32581 @subheading The @code{-var-list-children} Command
32582 @findex -var-list-children
32584 @subsubheading Synopsis
32587 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
32589 @anchor{-var-list-children}
32591 Return a list of the children of the specified variable object and
32592 create variable objects for them, if they do not already exist. With
32593 a single argument or if @var{print-values} has a value of 0 or
32594 @code{--no-values}, print only the names of the variables; if
32595 @var{print-values} is 1 or @code{--all-values}, also print their
32596 values; and if it is 2 or @code{--simple-values} print the name and
32597 value for simple data types and just the name for arrays, structures
32600 @var{from} and @var{to}, if specified, indicate the range of children
32601 to report. If @var{from} or @var{to} is less than zero, the range is
32602 reset and all children will be reported. Otherwise, children starting
32603 at @var{from} (zero-based) and up to and excluding @var{to} will be
32606 If a child range is requested, it will only affect the current call to
32607 @code{-var-list-children}, but not future calls to @code{-var-update}.
32608 For this, you must instead use @code{-var-set-update-range}. The
32609 intent of this approach is to enable a front end to implement any
32610 update approach it likes; for example, scrolling a view may cause the
32611 front end to request more children with @code{-var-list-children}, and
32612 then the front end could call @code{-var-set-update-range} with a
32613 different range to ensure that future updates are restricted to just
32616 For each child the following results are returned:
32621 Name of the variable object created for this child.
32624 The expression to be shown to the user by the front end to designate this child.
32625 For example this may be the name of a structure member.
32627 For a dynamic varobj, this value cannot be used to form an
32628 expression. There is no way to do this at all with a dynamic varobj.
32630 For C/C@t{++} structures there are several pseudo children returned to
32631 designate access qualifiers. For these pseudo children @var{exp} is
32632 @samp{public}, @samp{private}, or @samp{protected}. In this case the
32633 type and value are not present.
32635 A dynamic varobj will not report the access qualifying
32636 pseudo-children, regardless of the language. This information is not
32637 available at all with a dynamic varobj.
32640 Number of children this child has. For a dynamic varobj, this will be
32644 The type of the child. If @samp{print object}
32645 (@pxref{Print Settings, set print object}) is set to @code{on}, the
32646 @emph{actual} (derived) type of the object is shown rather than the
32647 @emph{declared} one.
32650 If values were requested, this is the value.
32653 If this variable object is associated with a thread, this is the thread id.
32654 Otherwise this result is not present.
32657 If the variable object is frozen, this variable will be present with a value of 1.
32660 A dynamic varobj can supply a display hint to the front end. The
32661 value comes directly from the Python pretty-printer object's
32662 @code{display_hint} method. @xref{Pretty Printing API}.
32665 This attribute will be present and have the value @samp{1} if the
32666 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
32667 then this attribute will not be present.
32671 The result may have its own attributes:
32675 A dynamic varobj can supply a display hint to the front end. The
32676 value comes directly from the Python pretty-printer object's
32677 @code{display_hint} method. @xref{Pretty Printing API}.
32680 This is an integer attribute which is nonzero if there are children
32681 remaining after the end of the selected range.
32684 @subsubheading Example
32688 -var-list-children n
32689 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
32690 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
32692 -var-list-children --all-values n
32693 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
32694 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
32698 @subheading The @code{-var-info-type} Command
32699 @findex -var-info-type
32701 @subsubheading Synopsis
32704 -var-info-type @var{name}
32707 Returns the type of the specified variable @var{name}. The type is
32708 returned as a string in the same format as it is output by the
32712 type=@var{typename}
32716 @subheading The @code{-var-info-expression} Command
32717 @findex -var-info-expression
32719 @subsubheading Synopsis
32722 -var-info-expression @var{name}
32725 Returns a string that is suitable for presenting this
32726 variable object in user interface. The string is generally
32727 not valid expression in the current language, and cannot be evaluated.
32729 For example, if @code{a} is an array, and variable object
32730 @code{A} was created for @code{a}, then we'll get this output:
32733 (gdb) -var-info-expression A.1
32734 ^done,lang="C",exp="1"
32738 Here, the value of @code{lang} is the language name, which can be
32739 found in @ref{Supported Languages}.
32741 Note that the output of the @code{-var-list-children} command also
32742 includes those expressions, so the @code{-var-info-expression} command
32745 @subheading The @code{-var-info-path-expression} Command
32746 @findex -var-info-path-expression
32748 @subsubheading Synopsis
32751 -var-info-path-expression @var{name}
32754 Returns an expression that can be evaluated in the current
32755 context and will yield the same value that a variable object has.
32756 Compare this with the @code{-var-info-expression} command, which
32757 result can be used only for UI presentation. Typical use of
32758 the @code{-var-info-path-expression} command is creating a
32759 watchpoint from a variable object.
32761 This command is currently not valid for children of a dynamic varobj,
32762 and will give an error when invoked on one.
32764 For example, suppose @code{C} is a C@t{++} class, derived from class
32765 @code{Base}, and that the @code{Base} class has a member called
32766 @code{m_size}. Assume a variable @code{c} is has the type of
32767 @code{C} and a variable object @code{C} was created for variable
32768 @code{c}. Then, we'll get this output:
32770 (gdb) -var-info-path-expression C.Base.public.m_size
32771 ^done,path_expr=((Base)c).m_size)
32774 @subheading The @code{-var-show-attributes} Command
32775 @findex -var-show-attributes
32777 @subsubheading Synopsis
32780 -var-show-attributes @var{name}
32783 List attributes of the specified variable object @var{name}:
32786 status=@var{attr} [ ( ,@var{attr} )* ]
32790 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
32792 @subheading The @code{-var-evaluate-expression} Command
32793 @findex -var-evaluate-expression
32795 @subsubheading Synopsis
32798 -var-evaluate-expression [-f @var{format-spec}] @var{name}
32801 Evaluates the expression that is represented by the specified variable
32802 object and returns its value as a string. The format of the string
32803 can be specified with the @samp{-f} option. The possible values of
32804 this option are the same as for @code{-var-set-format}
32805 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
32806 the current display format will be used. The current display format
32807 can be changed using the @code{-var-set-format} command.
32813 Note that one must invoke @code{-var-list-children} for a variable
32814 before the value of a child variable can be evaluated.
32816 @subheading The @code{-var-assign} Command
32817 @findex -var-assign
32819 @subsubheading Synopsis
32822 -var-assign @var{name} @var{expression}
32825 Assigns the value of @var{expression} to the variable object specified
32826 by @var{name}. The object must be @samp{editable}. If the variable's
32827 value is altered by the assign, the variable will show up in any
32828 subsequent @code{-var-update} list.
32830 @subsubheading Example
32838 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
32842 @subheading The @code{-var-update} Command
32843 @findex -var-update
32845 @subsubheading Synopsis
32848 -var-update [@var{print-values}] @{@var{name} | "*"@}
32851 Reevaluate the expressions corresponding to the variable object
32852 @var{name} and all its direct and indirect children, and return the
32853 list of variable objects whose values have changed; @var{name} must
32854 be a root variable object. Here, ``changed'' means that the result of
32855 @code{-var-evaluate-expression} before and after the
32856 @code{-var-update} is different. If @samp{*} is used as the variable
32857 object names, all existing variable objects are updated, except
32858 for frozen ones (@pxref{-var-set-frozen}). The option
32859 @var{print-values} determines whether both names and values, or just
32860 names are printed. The possible values of this option are the same
32861 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
32862 recommended to use the @samp{--all-values} option, to reduce the
32863 number of MI commands needed on each program stop.
32865 With the @samp{*} parameter, if a variable object is bound to a
32866 currently running thread, it will not be updated, without any
32869 If @code{-var-set-update-range} was previously used on a varobj, then
32870 only the selected range of children will be reported.
32872 @code{-var-update} reports all the changed varobjs in a tuple named
32875 Each item in the change list is itself a tuple holding:
32879 The name of the varobj.
32882 If values were requested for this update, then this field will be
32883 present and will hold the value of the varobj.
32886 @anchor{-var-update}
32887 This field is a string which may take one of three values:
32891 The variable object's current value is valid.
32894 The variable object does not currently hold a valid value but it may
32895 hold one in the future if its associated expression comes back into
32899 The variable object no longer holds a valid value.
32900 This can occur when the executable file being debugged has changed,
32901 either through recompilation or by using the @value{GDBN} @code{file}
32902 command. The front end should normally choose to delete these variable
32906 In the future new values may be added to this list so the front should
32907 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
32910 This is only present if the varobj is still valid. If the type
32911 changed, then this will be the string @samp{true}; otherwise it will
32914 When a varobj's type changes, its children are also likely to have
32915 become incorrect. Therefore, the varobj's children are automatically
32916 deleted when this attribute is @samp{true}. Also, the varobj's update
32917 range, when set using the @code{-var-set-update-range} command, is
32921 If the varobj's type changed, then this field will be present and will
32924 @item new_num_children
32925 For a dynamic varobj, if the number of children changed, or if the
32926 type changed, this will be the new number of children.
32928 The @samp{numchild} field in other varobj responses is generally not
32929 valid for a dynamic varobj -- it will show the number of children that
32930 @value{GDBN} knows about, but because dynamic varobjs lazily
32931 instantiate their children, this will not reflect the number of
32932 children which may be available.
32934 The @samp{new_num_children} attribute only reports changes to the
32935 number of children known by @value{GDBN}. This is the only way to
32936 detect whether an update has removed children (which necessarily can
32937 only happen at the end of the update range).
32940 The display hint, if any.
32943 This is an integer value, which will be 1 if there are more children
32944 available outside the varobj's update range.
32947 This attribute will be present and have the value @samp{1} if the
32948 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
32949 then this attribute will not be present.
32952 If new children were added to a dynamic varobj within the selected
32953 update range (as set by @code{-var-set-update-range}), then they will
32954 be listed in this attribute.
32957 @subsubheading Example
32964 -var-update --all-values var1
32965 ^done,changelist=[@{name="var1",value="3",in_scope="true",
32966 type_changed="false"@}]
32970 @subheading The @code{-var-set-frozen} Command
32971 @findex -var-set-frozen
32972 @anchor{-var-set-frozen}
32974 @subsubheading Synopsis
32977 -var-set-frozen @var{name} @var{flag}
32980 Set the frozenness flag on the variable object @var{name}. The
32981 @var{flag} parameter should be either @samp{1} to make the variable
32982 frozen or @samp{0} to make it unfrozen. If a variable object is
32983 frozen, then neither itself, nor any of its children, are
32984 implicitly updated by @code{-var-update} of
32985 a parent variable or by @code{-var-update *}. Only
32986 @code{-var-update} of the variable itself will update its value and
32987 values of its children. After a variable object is unfrozen, it is
32988 implicitly updated by all subsequent @code{-var-update} operations.
32989 Unfreezing a variable does not update it, only subsequent
32990 @code{-var-update} does.
32992 @subsubheading Example
32996 -var-set-frozen V 1
33001 @subheading The @code{-var-set-update-range} command
33002 @findex -var-set-update-range
33003 @anchor{-var-set-update-range}
33005 @subsubheading Synopsis
33008 -var-set-update-range @var{name} @var{from} @var{to}
33011 Set the range of children to be returned by future invocations of
33012 @code{-var-update}.
33014 @var{from} and @var{to} indicate the range of children to report. If
33015 @var{from} or @var{to} is less than zero, the range is reset and all
33016 children will be reported. Otherwise, children starting at @var{from}
33017 (zero-based) and up to and excluding @var{to} will be reported.
33019 @subsubheading Example
33023 -var-set-update-range V 1 2
33027 @subheading The @code{-var-set-visualizer} command
33028 @findex -var-set-visualizer
33029 @anchor{-var-set-visualizer}
33031 @subsubheading Synopsis
33034 -var-set-visualizer @var{name} @var{visualizer}
33037 Set a visualizer for the variable object @var{name}.
33039 @var{visualizer} is the visualizer to use. The special value
33040 @samp{None} means to disable any visualizer in use.
33042 If not @samp{None}, @var{visualizer} must be a Python expression.
33043 This expression must evaluate to a callable object which accepts a
33044 single argument. @value{GDBN} will call this object with the value of
33045 the varobj @var{name} as an argument (this is done so that the same
33046 Python pretty-printing code can be used for both the CLI and MI).
33047 When called, this object must return an object which conforms to the
33048 pretty-printing interface (@pxref{Pretty Printing API}).
33050 The pre-defined function @code{gdb.default_visualizer} may be used to
33051 select a visualizer by following the built-in process
33052 (@pxref{Selecting Pretty-Printers}). This is done automatically when
33053 a varobj is created, and so ordinarily is not needed.
33055 This feature is only available if Python support is enabled. The MI
33056 command @code{-list-features} (@pxref{GDB/MI Support Commands})
33057 can be used to check this.
33059 @subsubheading Example
33061 Resetting the visualizer:
33065 -var-set-visualizer V None
33069 Reselecting the default (type-based) visualizer:
33073 -var-set-visualizer V gdb.default_visualizer
33077 Suppose @code{SomeClass} is a visualizer class. A lambda expression
33078 can be used to instantiate this class for a varobj:
33082 -var-set-visualizer V "lambda val: SomeClass()"
33086 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33087 @node GDB/MI Data Manipulation
33088 @section @sc{gdb/mi} Data Manipulation
33090 @cindex data manipulation, in @sc{gdb/mi}
33091 @cindex @sc{gdb/mi}, data manipulation
33092 This section describes the @sc{gdb/mi} commands that manipulate data:
33093 examine memory and registers, evaluate expressions, etc.
33095 @c REMOVED FROM THE INTERFACE.
33096 @c @subheading -data-assign
33097 @c Change the value of a program variable. Plenty of side effects.
33098 @c @subsubheading GDB Command
33100 @c @subsubheading Example
33103 @subheading The @code{-data-disassemble} Command
33104 @findex -data-disassemble
33106 @subsubheading Synopsis
33110 [ -s @var{start-addr} -e @var{end-addr} ]
33111 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
33119 @item @var{start-addr}
33120 is the beginning address (or @code{$pc})
33121 @item @var{end-addr}
33123 @item @var{filename}
33124 is the name of the file to disassemble
33125 @item @var{linenum}
33126 is the line number to disassemble around
33128 is the number of disassembly lines to be produced. If it is -1,
33129 the whole function will be disassembled, in case no @var{end-addr} is
33130 specified. If @var{end-addr} is specified as a non-zero value, and
33131 @var{lines} is lower than the number of disassembly lines between
33132 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
33133 displayed; if @var{lines} is higher than the number of lines between
33134 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
33137 is either 0 (meaning only disassembly), 1 (meaning mixed source and
33138 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
33139 mixed source and disassembly with raw opcodes).
33142 @subsubheading Result
33144 The result of the @code{-data-disassemble} command will be a list named
33145 @samp{asm_insns}, the contents of this list depend on the @var{mode}
33146 used with the @code{-data-disassemble} command.
33148 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
33153 The address at which this instruction was disassembled.
33156 The name of the function this instruction is within.
33159 The decimal offset in bytes from the start of @samp{func-name}.
33162 The text disassembly for this @samp{address}.
33165 This field is only present for mode 2. This contains the raw opcode
33166 bytes for the @samp{inst} field.
33170 For modes 1 and 3 the @samp{asm_insns} list contains tuples named
33171 @samp{src_and_asm_line}, each of which has the following fields:
33175 The line number within @samp{file}.
33178 The file name from the compilation unit. This might be an absolute
33179 file name or a relative file name depending on the compile command
33183 Absolute file name of @samp{file}. It is converted to a canonical form
33184 using the source file search path
33185 (@pxref{Source Path, ,Specifying Source Directories})
33186 and after resolving all the symbolic links.
33188 If the source file is not found this field will contain the path as
33189 present in the debug information.
33191 @item line_asm_insn
33192 This is a list of tuples containing the disassembly for @samp{line} in
33193 @samp{file}. The fields of each tuple are the same as for
33194 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
33195 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
33200 Note that whatever included in the @samp{inst} field, is not
33201 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
33204 @subsubheading @value{GDBN} Command
33206 The corresponding @value{GDBN} command is @samp{disassemble}.
33208 @subsubheading Example
33210 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
33214 -data-disassemble -s $pc -e "$pc + 20" -- 0
33217 @{address="0x000107c0",func-name="main",offset="4",
33218 inst="mov 2, %o0"@},
33219 @{address="0x000107c4",func-name="main",offset="8",
33220 inst="sethi %hi(0x11800), %o2"@},
33221 @{address="0x000107c8",func-name="main",offset="12",
33222 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
33223 @{address="0x000107cc",func-name="main",offset="16",
33224 inst="sethi %hi(0x11800), %o2"@},
33225 @{address="0x000107d0",func-name="main",offset="20",
33226 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
33230 Disassemble the whole @code{main} function. Line 32 is part of
33234 -data-disassemble -f basics.c -l 32 -- 0
33236 @{address="0x000107bc",func-name="main",offset="0",
33237 inst="save %sp, -112, %sp"@},
33238 @{address="0x000107c0",func-name="main",offset="4",
33239 inst="mov 2, %o0"@},
33240 @{address="0x000107c4",func-name="main",offset="8",
33241 inst="sethi %hi(0x11800), %o2"@},
33243 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
33244 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
33248 Disassemble 3 instructions from the start of @code{main}:
33252 -data-disassemble -f basics.c -l 32 -n 3 -- 0
33254 @{address="0x000107bc",func-name="main",offset="0",
33255 inst="save %sp, -112, %sp"@},
33256 @{address="0x000107c0",func-name="main",offset="4",
33257 inst="mov 2, %o0"@},
33258 @{address="0x000107c4",func-name="main",offset="8",
33259 inst="sethi %hi(0x11800), %o2"@}]
33263 Disassemble 3 instructions from the start of @code{main} in mixed mode:
33267 -data-disassemble -f basics.c -l 32 -n 3 -- 1
33269 src_and_asm_line=@{line="31",
33270 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
33271 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
33272 line_asm_insn=[@{address="0x000107bc",
33273 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
33274 src_and_asm_line=@{line="32",
33275 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
33276 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
33277 line_asm_insn=[@{address="0x000107c0",
33278 func-name="main",offset="4",inst="mov 2, %o0"@},
33279 @{address="0x000107c4",func-name="main",offset="8",
33280 inst="sethi %hi(0x11800), %o2"@}]@}]
33285 @subheading The @code{-data-evaluate-expression} Command
33286 @findex -data-evaluate-expression
33288 @subsubheading Synopsis
33291 -data-evaluate-expression @var{expr}
33294 Evaluate @var{expr} as an expression. The expression could contain an
33295 inferior function call. The function call will execute synchronously.
33296 If the expression contains spaces, it must be enclosed in double quotes.
33298 @subsubheading @value{GDBN} Command
33300 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
33301 @samp{call}. In @code{gdbtk} only, there's a corresponding
33302 @samp{gdb_eval} command.
33304 @subsubheading Example
33306 In the following example, the numbers that precede the commands are the
33307 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
33308 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
33312 211-data-evaluate-expression A
33315 311-data-evaluate-expression &A
33316 311^done,value="0xefffeb7c"
33318 411-data-evaluate-expression A+3
33321 511-data-evaluate-expression "A + 3"
33327 @subheading The @code{-data-list-changed-registers} Command
33328 @findex -data-list-changed-registers
33330 @subsubheading Synopsis
33333 -data-list-changed-registers
33336 Display a list of the registers that have changed.
33338 @subsubheading @value{GDBN} Command
33340 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
33341 has the corresponding command @samp{gdb_changed_register_list}.
33343 @subsubheading Example
33345 On a PPC MBX board:
33353 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
33354 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
33357 -data-list-changed-registers
33358 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
33359 "10","11","13","14","15","16","17","18","19","20","21","22","23",
33360 "24","25","26","27","28","30","31","64","65","66","67","69"]
33365 @subheading The @code{-data-list-register-names} Command
33366 @findex -data-list-register-names
33368 @subsubheading Synopsis
33371 -data-list-register-names [ ( @var{regno} )+ ]
33374 Show a list of register names for the current target. If no arguments
33375 are given, it shows a list of the names of all the registers. If
33376 integer numbers are given as arguments, it will print a list of the
33377 names of the registers corresponding to the arguments. To ensure
33378 consistency between a register name and its number, the output list may
33379 include empty register names.
33381 @subsubheading @value{GDBN} Command
33383 @value{GDBN} does not have a command which corresponds to
33384 @samp{-data-list-register-names}. In @code{gdbtk} there is a
33385 corresponding command @samp{gdb_regnames}.
33387 @subsubheading Example
33389 For the PPC MBX board:
33392 -data-list-register-names
33393 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
33394 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
33395 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
33396 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
33397 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
33398 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
33399 "", "pc","ps","cr","lr","ctr","xer"]
33401 -data-list-register-names 1 2 3
33402 ^done,register-names=["r1","r2","r3"]
33406 @subheading The @code{-data-list-register-values} Command
33407 @findex -data-list-register-values
33409 @subsubheading Synopsis
33412 -data-list-register-values
33413 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
33416 Display the registers' contents. @var{fmt} is the format according to
33417 which the registers' contents are to be returned, followed by an optional
33418 list of numbers specifying the registers to display. A missing list of
33419 numbers indicates that the contents of all the registers must be
33420 returned. The @code{--skip-unavailable} option indicates that only
33421 the available registers are to be returned.
33423 Allowed formats for @var{fmt} are:
33440 @subsubheading @value{GDBN} Command
33442 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
33443 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
33445 @subsubheading Example
33447 For a PPC MBX board (note: line breaks are for readability only, they
33448 don't appear in the actual output):
33452 -data-list-register-values r 64 65
33453 ^done,register-values=[@{number="64",value="0xfe00a300"@},
33454 @{number="65",value="0x00029002"@}]
33456 -data-list-register-values x
33457 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
33458 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
33459 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
33460 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
33461 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
33462 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
33463 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
33464 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
33465 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
33466 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
33467 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
33468 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
33469 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
33470 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
33471 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
33472 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
33473 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
33474 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
33475 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
33476 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
33477 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
33478 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
33479 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
33480 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
33481 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
33482 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
33483 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
33484 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
33485 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
33486 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
33487 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
33488 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
33489 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
33490 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
33491 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
33492 @{number="69",value="0x20002b03"@}]
33497 @subheading The @code{-data-read-memory} Command
33498 @findex -data-read-memory
33500 This command is deprecated, use @code{-data-read-memory-bytes} instead.
33502 @subsubheading Synopsis
33505 -data-read-memory [ -o @var{byte-offset} ]
33506 @var{address} @var{word-format} @var{word-size}
33507 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
33514 @item @var{address}
33515 An expression specifying the address of the first memory word to be
33516 read. Complex expressions containing embedded white space should be
33517 quoted using the C convention.
33519 @item @var{word-format}
33520 The format to be used to print the memory words. The notation is the
33521 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
33524 @item @var{word-size}
33525 The size of each memory word in bytes.
33527 @item @var{nr-rows}
33528 The number of rows in the output table.
33530 @item @var{nr-cols}
33531 The number of columns in the output table.
33534 If present, indicates that each row should include an @sc{ascii} dump. The
33535 value of @var{aschar} is used as a padding character when a byte is not a
33536 member of the printable @sc{ascii} character set (printable @sc{ascii}
33537 characters are those whose code is between 32 and 126, inclusively).
33539 @item @var{byte-offset}
33540 An offset to add to the @var{address} before fetching memory.
33543 This command displays memory contents as a table of @var{nr-rows} by
33544 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
33545 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
33546 (returned as @samp{total-bytes}). Should less than the requested number
33547 of bytes be returned by the target, the missing words are identified
33548 using @samp{N/A}. The number of bytes read from the target is returned
33549 in @samp{nr-bytes} and the starting address used to read memory in
33552 The address of the next/previous row or page is available in
33553 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
33556 @subsubheading @value{GDBN} Command
33558 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
33559 @samp{gdb_get_mem} memory read command.
33561 @subsubheading Example
33563 Read six bytes of memory starting at @code{bytes+6} but then offset by
33564 @code{-6} bytes. Format as three rows of two columns. One byte per
33565 word. Display each word in hex.
33569 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
33570 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
33571 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
33572 prev-page="0x0000138a",memory=[
33573 @{addr="0x00001390",data=["0x00","0x01"]@},
33574 @{addr="0x00001392",data=["0x02","0x03"]@},
33575 @{addr="0x00001394",data=["0x04","0x05"]@}]
33579 Read two bytes of memory starting at address @code{shorts + 64} and
33580 display as a single word formatted in decimal.
33584 5-data-read-memory shorts+64 d 2 1 1
33585 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
33586 next-row="0x00001512",prev-row="0x0000150e",
33587 next-page="0x00001512",prev-page="0x0000150e",memory=[
33588 @{addr="0x00001510",data=["128"]@}]
33592 Read thirty two bytes of memory starting at @code{bytes+16} and format
33593 as eight rows of four columns. Include a string encoding with @samp{x}
33594 used as the non-printable character.
33598 4-data-read-memory bytes+16 x 1 8 4 x
33599 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
33600 next-row="0x000013c0",prev-row="0x0000139c",
33601 next-page="0x000013c0",prev-page="0x00001380",memory=[
33602 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
33603 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
33604 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
33605 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
33606 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
33607 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
33608 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
33609 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
33613 @subheading The @code{-data-read-memory-bytes} Command
33614 @findex -data-read-memory-bytes
33616 @subsubheading Synopsis
33619 -data-read-memory-bytes [ -o @var{byte-offset} ]
33620 @var{address} @var{count}
33627 @item @var{address}
33628 An expression specifying the address of the first memory word to be
33629 read. Complex expressions containing embedded white space should be
33630 quoted using the C convention.
33633 The number of bytes to read. This should be an integer literal.
33635 @item @var{byte-offset}
33636 The offsets in bytes relative to @var{address} at which to start
33637 reading. This should be an integer literal. This option is provided
33638 so that a frontend is not required to first evaluate address and then
33639 perform address arithmetics itself.
33643 This command attempts to read all accessible memory regions in the
33644 specified range. First, all regions marked as unreadable in the memory
33645 map (if one is defined) will be skipped. @xref{Memory Region
33646 Attributes}. Second, @value{GDBN} will attempt to read the remaining
33647 regions. For each one, if reading full region results in an errors,
33648 @value{GDBN} will try to read a subset of the region.
33650 In general, every single byte in the region may be readable or not,
33651 and the only way to read every readable byte is to try a read at
33652 every address, which is not practical. Therefore, @value{GDBN} will
33653 attempt to read all accessible bytes at either beginning or the end
33654 of the region, using a binary division scheme. This heuristic works
33655 well for reading accross a memory map boundary. Note that if a region
33656 has a readable range that is neither at the beginning or the end,
33657 @value{GDBN} will not read it.
33659 The result record (@pxref{GDB/MI Result Records}) that is output of
33660 the command includes a field named @samp{memory} whose content is a
33661 list of tuples. Each tuple represent a successfully read memory block
33662 and has the following fields:
33666 The start address of the memory block, as hexadecimal literal.
33669 The end address of the memory block, as hexadecimal literal.
33672 The offset of the memory block, as hexadecimal literal, relative to
33673 the start address passed to @code{-data-read-memory-bytes}.
33676 The contents of the memory block, in hex.
33682 @subsubheading @value{GDBN} Command
33684 The corresponding @value{GDBN} command is @samp{x}.
33686 @subsubheading Example
33690 -data-read-memory-bytes &a 10
33691 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
33693 contents="01000000020000000300"@}]
33698 @subheading The @code{-data-write-memory-bytes} Command
33699 @findex -data-write-memory-bytes
33701 @subsubheading Synopsis
33704 -data-write-memory-bytes @var{address} @var{contents}
33705 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
33712 @item @var{address}
33713 An expression specifying the address of the first memory word to be
33714 read. Complex expressions containing embedded white space should be
33715 quoted using the C convention.
33717 @item @var{contents}
33718 The hex-encoded bytes to write.
33721 Optional argument indicating the number of bytes to be written. If @var{count}
33722 is greater than @var{contents}' length, @value{GDBN} will repeatedly
33723 write @var{contents} until it fills @var{count} bytes.
33727 @subsubheading @value{GDBN} Command
33729 There's no corresponding @value{GDBN} command.
33731 @subsubheading Example
33735 -data-write-memory-bytes &a "aabbccdd"
33742 -data-write-memory-bytes &a "aabbccdd" 16e
33747 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33748 @node GDB/MI Tracepoint Commands
33749 @section @sc{gdb/mi} Tracepoint Commands
33751 The commands defined in this section implement MI support for
33752 tracepoints. For detailed introduction, see @ref{Tracepoints}.
33754 @subheading The @code{-trace-find} Command
33755 @findex -trace-find
33757 @subsubheading Synopsis
33760 -trace-find @var{mode} [@var{parameters}@dots{}]
33763 Find a trace frame using criteria defined by @var{mode} and
33764 @var{parameters}. The following table lists permissible
33765 modes and their parameters. For details of operation, see @ref{tfind}.
33770 No parameters are required. Stops examining trace frames.
33773 An integer is required as parameter. Selects tracepoint frame with
33776 @item tracepoint-number
33777 An integer is required as parameter. Finds next
33778 trace frame that corresponds to tracepoint with the specified number.
33781 An address is required as parameter. Finds
33782 next trace frame that corresponds to any tracepoint at the specified
33785 @item pc-inside-range
33786 Two addresses are required as parameters. Finds next trace
33787 frame that corresponds to a tracepoint at an address inside the
33788 specified range. Both bounds are considered to be inside the range.
33790 @item pc-outside-range
33791 Two addresses are required as parameters. Finds
33792 next trace frame that corresponds to a tracepoint at an address outside
33793 the specified range. Both bounds are considered to be inside the range.
33796 Line specification is required as parameter. @xref{Specify Location}.
33797 Finds next trace frame that corresponds to a tracepoint at
33798 the specified location.
33802 If @samp{none} was passed as @var{mode}, the response does not
33803 have fields. Otherwise, the response may have the following fields:
33807 This field has either @samp{0} or @samp{1} as the value, depending
33808 on whether a matching tracepoint was found.
33811 The index of the found traceframe. This field is present iff
33812 the @samp{found} field has value of @samp{1}.
33815 The index of the found tracepoint. This field is present iff
33816 the @samp{found} field has value of @samp{1}.
33819 The information about the frame corresponding to the found trace
33820 frame. This field is present only if a trace frame was found.
33821 @xref{GDB/MI Frame Information}, for description of this field.
33825 @subsubheading @value{GDBN} Command
33827 The corresponding @value{GDBN} command is @samp{tfind}.
33829 @subheading -trace-define-variable
33830 @findex -trace-define-variable
33832 @subsubheading Synopsis
33835 -trace-define-variable @var{name} [ @var{value} ]
33838 Create trace variable @var{name} if it does not exist. If
33839 @var{value} is specified, sets the initial value of the specified
33840 trace variable to that value. Note that the @var{name} should start
33841 with the @samp{$} character.
33843 @subsubheading @value{GDBN} Command
33845 The corresponding @value{GDBN} command is @samp{tvariable}.
33847 @subheading The @code{-trace-frame-collected} Command
33848 @findex -trace-frame-collected
33850 @subsubheading Synopsis
33853 -trace-frame-collected
33854 [--var-print-values @var{var_pval}]
33855 [--comp-print-values @var{comp_pval}]
33856 [--registers-format @var{regformat}]
33857 [--memory-contents]
33860 This command returns the set of collected objects, register names,
33861 trace state variable names, memory ranges and computed expressions
33862 that have been collected at a particular trace frame. The optional
33863 parameters to the command affect the output format in different ways.
33864 See the output description table below for more details.
33866 The reported names can be used in the normal manner to create
33867 varobjs and inspect the objects themselves. The items returned by
33868 this command are categorized so that it is clear which is a variable,
33869 which is a register, which is a trace state variable, which is a
33870 memory range and which is a computed expression.
33872 For instance, if the actions were
33874 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
33875 collect *(int*)0xaf02bef0@@40
33879 the object collected in its entirety would be @code{myVar}. The
33880 object @code{myArray} would be partially collected, because only the
33881 element at index @code{myIndex} would be collected. The remaining
33882 objects would be computed expressions.
33884 An example output would be:
33888 -trace-frame-collected
33890 explicit-variables=[@{name="myVar",value="1"@}],
33891 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
33892 @{name="myObj.field",value="0"@},
33893 @{name="myPtr->field",value="1"@},
33894 @{name="myCount + 2",value="3"@},
33895 @{name="$tvar1 + 1",value="43970027"@}],
33896 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
33897 @{number="1",value="0x0"@},
33898 @{number="2",value="0x4"@},
33900 @{number="125",value="0x0"@}],
33901 tvars=[@{name="$tvar1",current="43970026"@}],
33902 memory=[@{address="0x0000000000602264",length="4"@},
33903 @{address="0x0000000000615bc0",length="4"@}]
33910 @item explicit-variables
33911 The set of objects that have been collected in their entirety (as
33912 opposed to collecting just a few elements of an array or a few struct
33913 members). For each object, its name and value are printed.
33914 The @code{--var-print-values} option affects how or whether the value
33915 field is output. If @var{var_pval} is 0, then print only the names;
33916 if it is 1, print also their values; and if it is 2, print the name,
33917 type and value for simple data types, and the name and type for
33918 arrays, structures and unions.
33920 @item computed-expressions
33921 The set of computed expressions that have been collected at the
33922 current trace frame. The @code{--comp-print-values} option affects
33923 this set like the @code{--var-print-values} option affects the
33924 @code{explicit-variables} set. See above.
33927 The registers that have been collected at the current trace frame.
33928 For each register collected, the name and current value are returned.
33929 The value is formatted according to the @code{--registers-format}
33930 option. See the @command{-data-list-register-values} command for a
33931 list of the allowed formats. The default is @samp{x}.
33934 The trace state variables that have been collected at the current
33935 trace frame. For each trace state variable collected, the name and
33936 current value are returned.
33939 The set of memory ranges that have been collected at the current trace
33940 frame. Its content is a list of tuples. Each tuple represents a
33941 collected memory range and has the following fields:
33945 The start address of the memory range, as hexadecimal literal.
33948 The length of the memory range, as decimal literal.
33951 The contents of the memory block, in hex. This field is only present
33952 if the @code{--memory-contents} option is specified.
33958 @subsubheading @value{GDBN} Command
33960 There is no corresponding @value{GDBN} command.
33962 @subsubheading Example
33964 @subheading -trace-list-variables
33965 @findex -trace-list-variables
33967 @subsubheading Synopsis
33970 -trace-list-variables
33973 Return a table of all defined trace variables. Each element of the
33974 table has the following fields:
33978 The name of the trace variable. This field is always present.
33981 The initial value. This is a 64-bit signed integer. This
33982 field is always present.
33985 The value the trace variable has at the moment. This is a 64-bit
33986 signed integer. This field is absent iff current value is
33987 not defined, for example if the trace was never run, or is
33992 @subsubheading @value{GDBN} Command
33994 The corresponding @value{GDBN} command is @samp{tvariables}.
33996 @subsubheading Example
34000 -trace-list-variables
34001 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
34002 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
34003 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
34004 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
34005 body=[variable=@{name="$trace_timestamp",initial="0"@}
34006 variable=@{name="$foo",initial="10",current="15"@}]@}
34010 @subheading -trace-save
34011 @findex -trace-save
34013 @subsubheading Synopsis
34016 -trace-save [-r ] @var{filename}
34019 Saves the collected trace data to @var{filename}. Without the
34020 @samp{-r} option, the data is downloaded from the target and saved
34021 in a local file. With the @samp{-r} option the target is asked
34022 to perform the save.
34024 @subsubheading @value{GDBN} Command
34026 The corresponding @value{GDBN} command is @samp{tsave}.
34029 @subheading -trace-start
34030 @findex -trace-start
34032 @subsubheading Synopsis
34038 Starts a tracing experiments. The result of this command does not
34041 @subsubheading @value{GDBN} Command
34043 The corresponding @value{GDBN} command is @samp{tstart}.
34045 @subheading -trace-status
34046 @findex -trace-status
34048 @subsubheading Synopsis
34054 Obtains the status of a tracing experiment. The result may include
34055 the following fields:
34060 May have a value of either @samp{0}, when no tracing operations are
34061 supported, @samp{1}, when all tracing operations are supported, or
34062 @samp{file} when examining trace file. In the latter case, examining
34063 of trace frame is possible but new tracing experiement cannot be
34064 started. This field is always present.
34067 May have a value of either @samp{0} or @samp{1} depending on whether
34068 tracing experiement is in progress on target. This field is present
34069 if @samp{supported} field is not @samp{0}.
34072 Report the reason why the tracing was stopped last time. This field
34073 may be absent iff tracing was never stopped on target yet. The
34074 value of @samp{request} means the tracing was stopped as result of
34075 the @code{-trace-stop} command. The value of @samp{overflow} means
34076 the tracing buffer is full. The value of @samp{disconnection} means
34077 tracing was automatically stopped when @value{GDBN} has disconnected.
34078 The value of @samp{passcount} means tracing was stopped when a
34079 tracepoint was passed a maximal number of times for that tracepoint.
34080 This field is present if @samp{supported} field is not @samp{0}.
34082 @item stopping-tracepoint
34083 The number of tracepoint whose passcount as exceeded. This field is
34084 present iff the @samp{stop-reason} field has the value of
34088 @itemx frames-created
34089 The @samp{frames} field is a count of the total number of trace frames
34090 in the trace buffer, while @samp{frames-created} is the total created
34091 during the run, including ones that were discarded, such as when a
34092 circular trace buffer filled up. Both fields are optional.
34096 These fields tell the current size of the tracing buffer and the
34097 remaining space. These fields are optional.
34100 The value of the circular trace buffer flag. @code{1} means that the
34101 trace buffer is circular and old trace frames will be discarded if
34102 necessary to make room, @code{0} means that the trace buffer is linear
34106 The value of the disconnected tracing flag. @code{1} means that
34107 tracing will continue after @value{GDBN} disconnects, @code{0} means
34108 that the trace run will stop.
34111 The filename of the trace file being examined. This field is
34112 optional, and only present when examining a trace file.
34116 @subsubheading @value{GDBN} Command
34118 The corresponding @value{GDBN} command is @samp{tstatus}.
34120 @subheading -trace-stop
34121 @findex -trace-stop
34123 @subsubheading Synopsis
34129 Stops a tracing experiment. The result of this command has the same
34130 fields as @code{-trace-status}, except that the @samp{supported} and
34131 @samp{running} fields are not output.
34133 @subsubheading @value{GDBN} Command
34135 The corresponding @value{GDBN} command is @samp{tstop}.
34138 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34139 @node GDB/MI Symbol Query
34140 @section @sc{gdb/mi} Symbol Query Commands
34144 @subheading The @code{-symbol-info-address} Command
34145 @findex -symbol-info-address
34147 @subsubheading Synopsis
34150 -symbol-info-address @var{symbol}
34153 Describe where @var{symbol} is stored.
34155 @subsubheading @value{GDBN} Command
34157 The corresponding @value{GDBN} command is @samp{info address}.
34159 @subsubheading Example
34163 @subheading The @code{-symbol-info-file} Command
34164 @findex -symbol-info-file
34166 @subsubheading Synopsis
34172 Show the file for the symbol.
34174 @subsubheading @value{GDBN} Command
34176 There's no equivalent @value{GDBN} command. @code{gdbtk} has
34177 @samp{gdb_find_file}.
34179 @subsubheading Example
34183 @subheading The @code{-symbol-info-function} Command
34184 @findex -symbol-info-function
34186 @subsubheading Synopsis
34189 -symbol-info-function
34192 Show which function the symbol lives in.
34194 @subsubheading @value{GDBN} Command
34196 @samp{gdb_get_function} in @code{gdbtk}.
34198 @subsubheading Example
34202 @subheading The @code{-symbol-info-line} Command
34203 @findex -symbol-info-line
34205 @subsubheading Synopsis
34211 Show the core addresses of the code for a source line.
34213 @subsubheading @value{GDBN} Command
34215 The corresponding @value{GDBN} command is @samp{info line}.
34216 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
34218 @subsubheading Example
34222 @subheading The @code{-symbol-info-symbol} Command
34223 @findex -symbol-info-symbol
34225 @subsubheading Synopsis
34228 -symbol-info-symbol @var{addr}
34231 Describe what symbol is at location @var{addr}.
34233 @subsubheading @value{GDBN} Command
34235 The corresponding @value{GDBN} command is @samp{info symbol}.
34237 @subsubheading Example
34241 @subheading The @code{-symbol-list-functions} Command
34242 @findex -symbol-list-functions
34244 @subsubheading Synopsis
34247 -symbol-list-functions
34250 List the functions in the executable.
34252 @subsubheading @value{GDBN} Command
34254 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
34255 @samp{gdb_search} in @code{gdbtk}.
34257 @subsubheading Example
34262 @subheading The @code{-symbol-list-lines} Command
34263 @findex -symbol-list-lines
34265 @subsubheading Synopsis
34268 -symbol-list-lines @var{filename}
34271 Print the list of lines that contain code and their associated program
34272 addresses for the given source filename. The entries are sorted in
34273 ascending PC order.
34275 @subsubheading @value{GDBN} Command
34277 There is no corresponding @value{GDBN} command.
34279 @subsubheading Example
34282 -symbol-list-lines basics.c
34283 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
34289 @subheading The @code{-symbol-list-types} Command
34290 @findex -symbol-list-types
34292 @subsubheading Synopsis
34298 List all the type names.
34300 @subsubheading @value{GDBN} Command
34302 The corresponding commands are @samp{info types} in @value{GDBN},
34303 @samp{gdb_search} in @code{gdbtk}.
34305 @subsubheading Example
34309 @subheading The @code{-symbol-list-variables} Command
34310 @findex -symbol-list-variables
34312 @subsubheading Synopsis
34315 -symbol-list-variables
34318 List all the global and static variable names.
34320 @subsubheading @value{GDBN} Command
34322 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
34324 @subsubheading Example
34328 @subheading The @code{-symbol-locate} Command
34329 @findex -symbol-locate
34331 @subsubheading Synopsis
34337 @subsubheading @value{GDBN} Command
34339 @samp{gdb_loc} in @code{gdbtk}.
34341 @subsubheading Example
34345 @subheading The @code{-symbol-type} Command
34346 @findex -symbol-type
34348 @subsubheading Synopsis
34351 -symbol-type @var{variable}
34354 Show type of @var{variable}.
34356 @subsubheading @value{GDBN} Command
34358 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
34359 @samp{gdb_obj_variable}.
34361 @subsubheading Example
34366 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34367 @node GDB/MI File Commands
34368 @section @sc{gdb/mi} File Commands
34370 This section describes the GDB/MI commands to specify executable file names
34371 and to read in and obtain symbol table information.
34373 @subheading The @code{-file-exec-and-symbols} Command
34374 @findex -file-exec-and-symbols
34376 @subsubheading Synopsis
34379 -file-exec-and-symbols @var{file}
34382 Specify the executable file to be debugged. This file is the one from
34383 which the symbol table is also read. If no file is specified, the
34384 command clears the executable and symbol information. If breakpoints
34385 are set when using this command with no arguments, @value{GDBN} will produce
34386 error messages. Otherwise, no output is produced, except a completion
34389 @subsubheading @value{GDBN} Command
34391 The corresponding @value{GDBN} command is @samp{file}.
34393 @subsubheading Example
34397 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
34403 @subheading The @code{-file-exec-file} Command
34404 @findex -file-exec-file
34406 @subsubheading Synopsis
34409 -file-exec-file @var{file}
34412 Specify the executable file to be debugged. Unlike
34413 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
34414 from this file. If used without argument, @value{GDBN} clears the information
34415 about the executable file. No output is produced, except a completion
34418 @subsubheading @value{GDBN} Command
34420 The corresponding @value{GDBN} command is @samp{exec-file}.
34422 @subsubheading Example
34426 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
34433 @subheading The @code{-file-list-exec-sections} Command
34434 @findex -file-list-exec-sections
34436 @subsubheading Synopsis
34439 -file-list-exec-sections
34442 List the sections of the current executable file.
34444 @subsubheading @value{GDBN} Command
34446 The @value{GDBN} command @samp{info file} shows, among the rest, the same
34447 information as this command. @code{gdbtk} has a corresponding command
34448 @samp{gdb_load_info}.
34450 @subsubheading Example
34455 @subheading The @code{-file-list-exec-source-file} Command
34456 @findex -file-list-exec-source-file
34458 @subsubheading Synopsis
34461 -file-list-exec-source-file
34464 List the line number, the current source file, and the absolute path
34465 to the current source file for the current executable. The macro
34466 information field has a value of @samp{1} or @samp{0} depending on
34467 whether or not the file includes preprocessor macro information.
34469 @subsubheading @value{GDBN} Command
34471 The @value{GDBN} equivalent is @samp{info source}
34473 @subsubheading Example
34477 123-file-list-exec-source-file
34478 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
34483 @subheading The @code{-file-list-exec-source-files} Command
34484 @findex -file-list-exec-source-files
34486 @subsubheading Synopsis
34489 -file-list-exec-source-files
34492 List the source files for the current executable.
34494 It will always output both the filename and fullname (absolute file
34495 name) of a source file.
34497 @subsubheading @value{GDBN} Command
34499 The @value{GDBN} equivalent is @samp{info sources}.
34500 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
34502 @subsubheading Example
34505 -file-list-exec-source-files
34507 @{file=foo.c,fullname=/home/foo.c@},
34508 @{file=/home/bar.c,fullname=/home/bar.c@},
34509 @{file=gdb_could_not_find_fullpath.c@}]
34514 @subheading The @code{-file-list-shared-libraries} Command
34515 @findex -file-list-shared-libraries
34517 @subsubheading Synopsis
34520 -file-list-shared-libraries
34523 List the shared libraries in the program.
34525 @subsubheading @value{GDBN} Command
34527 The corresponding @value{GDBN} command is @samp{info shared}.
34529 @subsubheading Example
34533 @subheading The @code{-file-list-symbol-files} Command
34534 @findex -file-list-symbol-files
34536 @subsubheading Synopsis
34539 -file-list-symbol-files
34544 @subsubheading @value{GDBN} Command
34546 The corresponding @value{GDBN} command is @samp{info file} (part of it).
34548 @subsubheading Example
34553 @subheading The @code{-file-symbol-file} Command
34554 @findex -file-symbol-file
34556 @subsubheading Synopsis
34559 -file-symbol-file @var{file}
34562 Read symbol table info from the specified @var{file} argument. When
34563 used without arguments, clears @value{GDBN}'s symbol table info. No output is
34564 produced, except for a completion notification.
34566 @subsubheading @value{GDBN} Command
34568 The corresponding @value{GDBN} command is @samp{symbol-file}.
34570 @subsubheading Example
34574 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
34580 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34581 @node GDB/MI Memory Overlay Commands
34582 @section @sc{gdb/mi} Memory Overlay Commands
34584 The memory overlay commands are not implemented.
34586 @c @subheading -overlay-auto
34588 @c @subheading -overlay-list-mapping-state
34590 @c @subheading -overlay-list-overlays
34592 @c @subheading -overlay-map
34594 @c @subheading -overlay-off
34596 @c @subheading -overlay-on
34598 @c @subheading -overlay-unmap
34600 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34601 @node GDB/MI Signal Handling Commands
34602 @section @sc{gdb/mi} Signal Handling Commands
34604 Signal handling commands are not implemented.
34606 @c @subheading -signal-handle
34608 @c @subheading -signal-list-handle-actions
34610 @c @subheading -signal-list-signal-types
34614 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34615 @node GDB/MI Target Manipulation
34616 @section @sc{gdb/mi} Target Manipulation Commands
34619 @subheading The @code{-target-attach} Command
34620 @findex -target-attach
34622 @subsubheading Synopsis
34625 -target-attach @var{pid} | @var{gid} | @var{file}
34628 Attach to a process @var{pid} or a file @var{file} outside of
34629 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
34630 group, the id previously returned by
34631 @samp{-list-thread-groups --available} must be used.
34633 @subsubheading @value{GDBN} Command
34635 The corresponding @value{GDBN} command is @samp{attach}.
34637 @subsubheading Example
34641 =thread-created,id="1"
34642 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
34648 @subheading The @code{-target-compare-sections} Command
34649 @findex -target-compare-sections
34651 @subsubheading Synopsis
34654 -target-compare-sections [ @var{section} ]
34657 Compare data of section @var{section} on target to the exec file.
34658 Without the argument, all sections are compared.
34660 @subsubheading @value{GDBN} Command
34662 The @value{GDBN} equivalent is @samp{compare-sections}.
34664 @subsubheading Example
34669 @subheading The @code{-target-detach} Command
34670 @findex -target-detach
34672 @subsubheading Synopsis
34675 -target-detach [ @var{pid} | @var{gid} ]
34678 Detach from the remote target which normally resumes its execution.
34679 If either @var{pid} or @var{gid} is specified, detaches from either
34680 the specified process, or specified thread group. There's no output.
34682 @subsubheading @value{GDBN} Command
34684 The corresponding @value{GDBN} command is @samp{detach}.
34686 @subsubheading Example
34696 @subheading The @code{-target-disconnect} Command
34697 @findex -target-disconnect
34699 @subsubheading Synopsis
34705 Disconnect from the remote target. There's no output and the target is
34706 generally not resumed.
34708 @subsubheading @value{GDBN} Command
34710 The corresponding @value{GDBN} command is @samp{disconnect}.
34712 @subsubheading Example
34722 @subheading The @code{-target-download} Command
34723 @findex -target-download
34725 @subsubheading Synopsis
34731 Loads the executable onto the remote target.
34732 It prints out an update message every half second, which includes the fields:
34736 The name of the section.
34738 The size of what has been sent so far for that section.
34740 The size of the section.
34742 The total size of what was sent so far (the current and the previous sections).
34744 The size of the overall executable to download.
34748 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
34749 @sc{gdb/mi} Output Syntax}).
34751 In addition, it prints the name and size of the sections, as they are
34752 downloaded. These messages include the following fields:
34756 The name of the section.
34758 The size of the section.
34760 The size of the overall executable to download.
34764 At the end, a summary is printed.
34766 @subsubheading @value{GDBN} Command
34768 The corresponding @value{GDBN} command is @samp{load}.
34770 @subsubheading Example
34772 Note: each status message appears on a single line. Here the messages
34773 have been broken down so that they can fit onto a page.
34778 +download,@{section=".text",section-size="6668",total-size="9880"@}
34779 +download,@{section=".text",section-sent="512",section-size="6668",
34780 total-sent="512",total-size="9880"@}
34781 +download,@{section=".text",section-sent="1024",section-size="6668",
34782 total-sent="1024",total-size="9880"@}
34783 +download,@{section=".text",section-sent="1536",section-size="6668",
34784 total-sent="1536",total-size="9880"@}
34785 +download,@{section=".text",section-sent="2048",section-size="6668",
34786 total-sent="2048",total-size="9880"@}
34787 +download,@{section=".text",section-sent="2560",section-size="6668",
34788 total-sent="2560",total-size="9880"@}
34789 +download,@{section=".text",section-sent="3072",section-size="6668",
34790 total-sent="3072",total-size="9880"@}
34791 +download,@{section=".text",section-sent="3584",section-size="6668",
34792 total-sent="3584",total-size="9880"@}
34793 +download,@{section=".text",section-sent="4096",section-size="6668",
34794 total-sent="4096",total-size="9880"@}
34795 +download,@{section=".text",section-sent="4608",section-size="6668",
34796 total-sent="4608",total-size="9880"@}
34797 +download,@{section=".text",section-sent="5120",section-size="6668",
34798 total-sent="5120",total-size="9880"@}
34799 +download,@{section=".text",section-sent="5632",section-size="6668",
34800 total-sent="5632",total-size="9880"@}
34801 +download,@{section=".text",section-sent="6144",section-size="6668",
34802 total-sent="6144",total-size="9880"@}
34803 +download,@{section=".text",section-sent="6656",section-size="6668",
34804 total-sent="6656",total-size="9880"@}
34805 +download,@{section=".init",section-size="28",total-size="9880"@}
34806 +download,@{section=".fini",section-size="28",total-size="9880"@}
34807 +download,@{section=".data",section-size="3156",total-size="9880"@}
34808 +download,@{section=".data",section-sent="512",section-size="3156",
34809 total-sent="7236",total-size="9880"@}
34810 +download,@{section=".data",section-sent="1024",section-size="3156",
34811 total-sent="7748",total-size="9880"@}
34812 +download,@{section=".data",section-sent="1536",section-size="3156",
34813 total-sent="8260",total-size="9880"@}
34814 +download,@{section=".data",section-sent="2048",section-size="3156",
34815 total-sent="8772",total-size="9880"@}
34816 +download,@{section=".data",section-sent="2560",section-size="3156",
34817 total-sent="9284",total-size="9880"@}
34818 +download,@{section=".data",section-sent="3072",section-size="3156",
34819 total-sent="9796",total-size="9880"@}
34820 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
34827 @subheading The @code{-target-exec-status} Command
34828 @findex -target-exec-status
34830 @subsubheading Synopsis
34833 -target-exec-status
34836 Provide information on the state of the target (whether it is running or
34837 not, for instance).
34839 @subsubheading @value{GDBN} Command
34841 There's no equivalent @value{GDBN} command.
34843 @subsubheading Example
34847 @subheading The @code{-target-list-available-targets} Command
34848 @findex -target-list-available-targets
34850 @subsubheading Synopsis
34853 -target-list-available-targets
34856 List the possible targets to connect to.
34858 @subsubheading @value{GDBN} Command
34860 The corresponding @value{GDBN} command is @samp{help target}.
34862 @subsubheading Example
34866 @subheading The @code{-target-list-current-targets} Command
34867 @findex -target-list-current-targets
34869 @subsubheading Synopsis
34872 -target-list-current-targets
34875 Describe the current target.
34877 @subsubheading @value{GDBN} Command
34879 The corresponding information is printed by @samp{info file} (among
34882 @subsubheading Example
34886 @subheading The @code{-target-list-parameters} Command
34887 @findex -target-list-parameters
34889 @subsubheading Synopsis
34892 -target-list-parameters
34898 @subsubheading @value{GDBN} Command
34902 @subsubheading Example
34906 @subheading The @code{-target-select} Command
34907 @findex -target-select
34909 @subsubheading Synopsis
34912 -target-select @var{type} @var{parameters @dots{}}
34915 Connect @value{GDBN} to the remote target. This command takes two args:
34919 The type of target, for instance @samp{remote}, etc.
34920 @item @var{parameters}
34921 Device names, host names and the like. @xref{Target Commands, ,
34922 Commands for Managing Targets}, for more details.
34925 The output is a connection notification, followed by the address at
34926 which the target program is, in the following form:
34929 ^connected,addr="@var{address}",func="@var{function name}",
34930 args=[@var{arg list}]
34933 @subsubheading @value{GDBN} Command
34935 The corresponding @value{GDBN} command is @samp{target}.
34937 @subsubheading Example
34941 -target-select remote /dev/ttya
34942 ^connected,addr="0xfe00a300",func="??",args=[]
34946 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34947 @node GDB/MI File Transfer Commands
34948 @section @sc{gdb/mi} File Transfer Commands
34951 @subheading The @code{-target-file-put} Command
34952 @findex -target-file-put
34954 @subsubheading Synopsis
34957 -target-file-put @var{hostfile} @var{targetfile}
34960 Copy file @var{hostfile} from the host system (the machine running
34961 @value{GDBN}) to @var{targetfile} on the target system.
34963 @subsubheading @value{GDBN} Command
34965 The corresponding @value{GDBN} command is @samp{remote put}.
34967 @subsubheading Example
34971 -target-file-put localfile remotefile
34977 @subheading The @code{-target-file-get} Command
34978 @findex -target-file-get
34980 @subsubheading Synopsis
34983 -target-file-get @var{targetfile} @var{hostfile}
34986 Copy file @var{targetfile} from the target system to @var{hostfile}
34987 on the host system.
34989 @subsubheading @value{GDBN} Command
34991 The corresponding @value{GDBN} command is @samp{remote get}.
34993 @subsubheading Example
34997 -target-file-get remotefile localfile
35003 @subheading The @code{-target-file-delete} Command
35004 @findex -target-file-delete
35006 @subsubheading Synopsis
35009 -target-file-delete @var{targetfile}
35012 Delete @var{targetfile} from the target system.
35014 @subsubheading @value{GDBN} Command
35016 The corresponding @value{GDBN} command is @samp{remote delete}.
35018 @subsubheading Example
35022 -target-file-delete remotefile
35028 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35029 @node GDB/MI Ada Exceptions Commands
35030 @section Ada Exceptions @sc{gdb/mi} Commands
35032 @subheading The @code{-info-ada-exceptions} Command
35033 @findex -info-ada-exceptions
35035 @subsubheading Synopsis
35038 -info-ada-exceptions [ @var{regexp}]
35041 List all Ada exceptions defined within the program being debugged.
35042 With a regular expression @var{regexp}, only those exceptions whose
35043 names match @var{regexp} are listed.
35045 @subsubheading @value{GDBN} Command
35047 The corresponding @value{GDBN} command is @samp{info exceptions}.
35049 @subsubheading Result
35051 The result is a table of Ada exceptions. The following columns are
35052 defined for each exception:
35056 The name of the exception.
35059 The address of the exception.
35063 @subsubheading Example
35066 -info-ada-exceptions aint
35067 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
35068 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
35069 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
35070 body=[@{name="constraint_error",address="0x0000000000613da0"@},
35071 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
35074 @subheading Catching Ada Exceptions
35076 The commands describing how to ask @value{GDBN} to stop when a program
35077 raises an exception are described at @ref{Ada Exception GDB/MI
35078 Catchpoint Commands}.
35081 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35082 @node GDB/MI Support Commands
35083 @section @sc{gdb/mi} Support Commands
35085 Since new commands and features get regularly added to @sc{gdb/mi},
35086 some commands are available to help front-ends query the debugger
35087 about support for these capabilities. Similarly, it is also possible
35088 to query @value{GDBN} about target support of certain features.
35090 @subheading The @code{-info-gdb-mi-command} Command
35091 @cindex @code{-info-gdb-mi-command}
35092 @findex -info-gdb-mi-command
35094 @subsubheading Synopsis
35097 -info-gdb-mi-command @var{cmd_name}
35100 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
35102 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
35103 is technically not part of the command name (@pxref{GDB/MI Input
35104 Syntax}), and thus should be omitted in @var{cmd_name}. However,
35105 for ease of use, this command also accepts the form with the leading
35108 @subsubheading @value{GDBN} Command
35110 There is no corresponding @value{GDBN} command.
35112 @subsubheading Result
35114 The result is a tuple. There is currently only one field:
35118 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
35119 @code{"false"} otherwise.
35123 @subsubheading Example
35125 Here is an example where the @sc{gdb/mi} command does not exist:
35128 -info-gdb-mi-command unsupported-command
35129 ^done,command=@{exists="false"@}
35133 And here is an example where the @sc{gdb/mi} command is known
35137 -info-gdb-mi-command symbol-list-lines
35138 ^done,command=@{exists="true"@}
35141 @subheading The @code{-list-features} Command
35142 @findex -list-features
35143 @cindex supported @sc{gdb/mi} features, list
35145 Returns a list of particular features of the MI protocol that
35146 this version of gdb implements. A feature can be a command,
35147 or a new field in an output of some command, or even an
35148 important bugfix. While a frontend can sometimes detect presence
35149 of a feature at runtime, it is easier to perform detection at debugger
35152 The command returns a list of strings, with each string naming an
35153 available feature. Each returned string is just a name, it does not
35154 have any internal structure. The list of possible feature names
35160 (gdb) -list-features
35161 ^done,result=["feature1","feature2"]
35164 The current list of features is:
35167 @item frozen-varobjs
35168 Indicates support for the @code{-var-set-frozen} command, as well
35169 as possible presense of the @code{frozen} field in the output
35170 of @code{-varobj-create}.
35171 @item pending-breakpoints
35172 Indicates support for the @option{-f} option to the @code{-break-insert}
35175 Indicates Python scripting support, Python-based
35176 pretty-printing commands, and possible presence of the
35177 @samp{display_hint} field in the output of @code{-var-list-children}
35179 Indicates support for the @code{-thread-info} command.
35180 @item data-read-memory-bytes
35181 Indicates support for the @code{-data-read-memory-bytes} and the
35182 @code{-data-write-memory-bytes} commands.
35183 @item breakpoint-notifications
35184 Indicates that changes to breakpoints and breakpoints created via the
35185 CLI will be announced via async records.
35186 @item ada-task-info
35187 Indicates support for the @code{-ada-task-info} command.
35188 @item language-option
35189 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
35190 option (@pxref{Context management}).
35191 @item info-gdb-mi-command
35192 Indicates support for the @code{-info-gdb-mi-command} command.
35193 @item undefined-command-error-code
35194 Indicates support for the "undefined-command" error code in error result
35195 records, produced when trying to execute an undefined @sc{gdb/mi} command
35196 (@pxref{GDB/MI Result Records}).
35197 @item exec-run-start-option
35198 Indicates that the @code{-exec-run} command supports the @option{--start}
35199 option (@pxref{GDB/MI Program Execution}).
35202 @subheading The @code{-list-target-features} Command
35203 @findex -list-target-features
35205 Returns a list of particular features that are supported by the
35206 target. Those features affect the permitted MI commands, but
35207 unlike the features reported by the @code{-list-features} command, the
35208 features depend on which target GDB is using at the moment. Whenever
35209 a target can change, due to commands such as @code{-target-select},
35210 @code{-target-attach} or @code{-exec-run}, the list of target features
35211 may change, and the frontend should obtain it again.
35215 (gdb) -list-target-features
35216 ^done,result=["async"]
35219 The current list of features is:
35223 Indicates that the target is capable of asynchronous command
35224 execution, which means that @value{GDBN} will accept further commands
35225 while the target is running.
35228 Indicates that the target is capable of reverse execution.
35229 @xref{Reverse Execution}, for more information.
35233 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35234 @node GDB/MI Miscellaneous Commands
35235 @section Miscellaneous @sc{gdb/mi} Commands
35237 @c @subheading -gdb-complete
35239 @subheading The @code{-gdb-exit} Command
35242 @subsubheading Synopsis
35248 Exit @value{GDBN} immediately.
35250 @subsubheading @value{GDBN} Command
35252 Approximately corresponds to @samp{quit}.
35254 @subsubheading Example
35264 @subheading The @code{-exec-abort} Command
35265 @findex -exec-abort
35267 @subsubheading Synopsis
35273 Kill the inferior running program.
35275 @subsubheading @value{GDBN} Command
35277 The corresponding @value{GDBN} command is @samp{kill}.
35279 @subsubheading Example
35284 @subheading The @code{-gdb-set} Command
35287 @subsubheading Synopsis
35293 Set an internal @value{GDBN} variable.
35294 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
35296 @subsubheading @value{GDBN} Command
35298 The corresponding @value{GDBN} command is @samp{set}.
35300 @subsubheading Example
35310 @subheading The @code{-gdb-show} Command
35313 @subsubheading Synopsis
35319 Show the current value of a @value{GDBN} variable.
35321 @subsubheading @value{GDBN} Command
35323 The corresponding @value{GDBN} command is @samp{show}.
35325 @subsubheading Example
35334 @c @subheading -gdb-source
35337 @subheading The @code{-gdb-version} Command
35338 @findex -gdb-version
35340 @subsubheading Synopsis
35346 Show version information for @value{GDBN}. Used mostly in testing.
35348 @subsubheading @value{GDBN} Command
35350 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
35351 default shows this information when you start an interactive session.
35353 @subsubheading Example
35355 @c This example modifies the actual output from GDB to avoid overfull
35361 ~Copyright 2000 Free Software Foundation, Inc.
35362 ~GDB is free software, covered by the GNU General Public License, and
35363 ~you are welcome to change it and/or distribute copies of it under
35364 ~ certain conditions.
35365 ~Type "show copying" to see the conditions.
35366 ~There is absolutely no warranty for GDB. Type "show warranty" for
35368 ~This GDB was configured as
35369 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
35374 @subheading The @code{-list-thread-groups} Command
35375 @findex -list-thread-groups
35377 @subheading Synopsis
35380 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
35383 Lists thread groups (@pxref{Thread groups}). When a single thread
35384 group is passed as the argument, lists the children of that group.
35385 When several thread group are passed, lists information about those
35386 thread groups. Without any parameters, lists information about all
35387 top-level thread groups.
35389 Normally, thread groups that are being debugged are reported.
35390 With the @samp{--available} option, @value{GDBN} reports thread groups
35391 available on the target.
35393 The output of this command may have either a @samp{threads} result or
35394 a @samp{groups} result. The @samp{thread} result has a list of tuples
35395 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
35396 Information}). The @samp{groups} result has a list of tuples as value,
35397 each tuple describing a thread group. If top-level groups are
35398 requested (that is, no parameter is passed), or when several groups
35399 are passed, the output always has a @samp{groups} result. The format
35400 of the @samp{group} result is described below.
35402 To reduce the number of roundtrips it's possible to list thread groups
35403 together with their children, by passing the @samp{--recurse} option
35404 and the recursion depth. Presently, only recursion depth of 1 is
35405 permitted. If this option is present, then every reported thread group
35406 will also include its children, either as @samp{group} or
35407 @samp{threads} field.
35409 In general, any combination of option and parameters is permitted, with
35410 the following caveats:
35414 When a single thread group is passed, the output will typically
35415 be the @samp{threads} result. Because threads may not contain
35416 anything, the @samp{recurse} option will be ignored.
35419 When the @samp{--available} option is passed, limited information may
35420 be available. In particular, the list of threads of a process might
35421 be inaccessible. Further, specifying specific thread groups might
35422 not give any performance advantage over listing all thread groups.
35423 The frontend should assume that @samp{-list-thread-groups --available}
35424 is always an expensive operation and cache the results.
35428 The @samp{groups} result is a list of tuples, where each tuple may
35429 have the following fields:
35433 Identifier of the thread group. This field is always present.
35434 The identifier is an opaque string; frontends should not try to
35435 convert it to an integer, even though it might look like one.
35438 The type of the thread group. At present, only @samp{process} is a
35442 The target-specific process identifier. This field is only present
35443 for thread groups of type @samp{process} and only if the process exists.
35446 The number of children this thread group has. This field may be
35447 absent for an available thread group.
35450 This field has a list of tuples as value, each tuple describing a
35451 thread. It may be present if the @samp{--recurse} option is
35452 specified, and it's actually possible to obtain the threads.
35455 This field is a list of integers, each identifying a core that one
35456 thread of the group is running on. This field may be absent if
35457 such information is not available.
35460 The name of the executable file that corresponds to this thread group.
35461 The field is only present for thread groups of type @samp{process},
35462 and only if there is a corresponding executable file.
35466 @subheading Example
35470 -list-thread-groups
35471 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
35472 -list-thread-groups 17
35473 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
35474 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
35475 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
35476 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
35477 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
35478 -list-thread-groups --available
35479 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
35480 -list-thread-groups --available --recurse 1
35481 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
35482 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
35483 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
35484 -list-thread-groups --available --recurse 1 17 18
35485 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
35486 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
35487 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
35490 @subheading The @code{-info-os} Command
35493 @subsubheading Synopsis
35496 -info-os [ @var{type} ]
35499 If no argument is supplied, the command returns a table of available
35500 operating-system-specific information types. If one of these types is
35501 supplied as an argument @var{type}, then the command returns a table
35502 of data of that type.
35504 The types of information available depend on the target operating
35507 @subsubheading @value{GDBN} Command
35509 The corresponding @value{GDBN} command is @samp{info os}.
35511 @subsubheading Example
35513 When run on a @sc{gnu}/Linux system, the output will look something
35519 ^done,OSDataTable=@{nr_rows="9",nr_cols="3",
35520 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
35521 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
35522 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
35523 body=[item=@{col0="processes",col1="Listing of all processes",
35524 col2="Processes"@},
35525 item=@{col0="procgroups",col1="Listing of all process groups",
35526 col2="Process groups"@},
35527 item=@{col0="threads",col1="Listing of all threads",
35529 item=@{col0="files",col1="Listing of all file descriptors",
35530 col2="File descriptors"@},
35531 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
35533 item=@{col0="shm",col1="Listing of all shared-memory regions",
35534 col2="Shared-memory regions"@},
35535 item=@{col0="semaphores",col1="Listing of all semaphores",
35536 col2="Semaphores"@},
35537 item=@{col0="msg",col1="Listing of all message queues",
35538 col2="Message queues"@},
35539 item=@{col0="modules",col1="Listing of all loaded kernel modules",
35540 col2="Kernel modules"@}]@}
35543 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
35544 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
35545 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
35546 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
35547 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
35548 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
35549 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
35550 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
35552 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
35553 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
35557 (Note that the MI output here includes a @code{"Title"} column that
35558 does not appear in command-line @code{info os}; this column is useful
35559 for MI clients that want to enumerate the types of data, such as in a
35560 popup menu, but is needless clutter on the command line, and
35561 @code{info os} omits it.)
35563 @subheading The @code{-add-inferior} Command
35564 @findex -add-inferior
35566 @subheading Synopsis
35572 Creates a new inferior (@pxref{Inferiors and Programs}). The created
35573 inferior is not associated with any executable. Such association may
35574 be established with the @samp{-file-exec-and-symbols} command
35575 (@pxref{GDB/MI File Commands}). The command response has a single
35576 field, @samp{inferior}, whose value is the identifier of the
35577 thread group corresponding to the new inferior.
35579 @subheading Example
35584 ^done,inferior="i3"
35587 @subheading The @code{-interpreter-exec} Command
35588 @findex -interpreter-exec
35590 @subheading Synopsis
35593 -interpreter-exec @var{interpreter} @var{command}
35595 @anchor{-interpreter-exec}
35597 Execute the specified @var{command} in the given @var{interpreter}.
35599 @subheading @value{GDBN} Command
35601 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
35603 @subheading Example
35607 -interpreter-exec console "break main"
35608 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
35609 &"During symbol reading, bad structure-type format.\n"
35610 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
35615 @subheading The @code{-inferior-tty-set} Command
35616 @findex -inferior-tty-set
35618 @subheading Synopsis
35621 -inferior-tty-set /dev/pts/1
35624 Set terminal for future runs of the program being debugged.
35626 @subheading @value{GDBN} Command
35628 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
35630 @subheading Example
35634 -inferior-tty-set /dev/pts/1
35639 @subheading The @code{-inferior-tty-show} Command
35640 @findex -inferior-tty-show
35642 @subheading Synopsis
35648 Show terminal for future runs of program being debugged.
35650 @subheading @value{GDBN} Command
35652 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
35654 @subheading Example
35658 -inferior-tty-set /dev/pts/1
35662 ^done,inferior_tty_terminal="/dev/pts/1"
35666 @subheading The @code{-enable-timings} Command
35667 @findex -enable-timings
35669 @subheading Synopsis
35672 -enable-timings [yes | no]
35675 Toggle the printing of the wallclock, user and system times for an MI
35676 command as a field in its output. This command is to help frontend
35677 developers optimize the performance of their code. No argument is
35678 equivalent to @samp{yes}.
35680 @subheading @value{GDBN} Command
35684 @subheading Example
35692 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
35693 addr="0x080484ed",func="main",file="myprog.c",
35694 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
35696 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
35704 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
35705 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
35706 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
35707 fullname="/home/nickrob/myprog.c",line="73"@}
35712 @chapter @value{GDBN} Annotations
35714 This chapter describes annotations in @value{GDBN}. Annotations were
35715 designed to interface @value{GDBN} to graphical user interfaces or other
35716 similar programs which want to interact with @value{GDBN} at a
35717 relatively high level.
35719 The annotation mechanism has largely been superseded by @sc{gdb/mi}
35723 This is Edition @value{EDITION}, @value{DATE}.
35727 * Annotations Overview:: What annotations are; the general syntax.
35728 * Server Prefix:: Issuing a command without affecting user state.
35729 * Prompting:: Annotations marking @value{GDBN}'s need for input.
35730 * Errors:: Annotations for error messages.
35731 * Invalidation:: Some annotations describe things now invalid.
35732 * Annotations for Running::
35733 Whether the program is running, how it stopped, etc.
35734 * Source Annotations:: Annotations describing source code.
35737 @node Annotations Overview
35738 @section What is an Annotation?
35739 @cindex annotations
35741 Annotations start with a newline character, two @samp{control-z}
35742 characters, and the name of the annotation. If there is no additional
35743 information associated with this annotation, the name of the annotation
35744 is followed immediately by a newline. If there is additional
35745 information, the name of the annotation is followed by a space, the
35746 additional information, and a newline. The additional information
35747 cannot contain newline characters.
35749 Any output not beginning with a newline and two @samp{control-z}
35750 characters denotes literal output from @value{GDBN}. Currently there is
35751 no need for @value{GDBN} to output a newline followed by two
35752 @samp{control-z} characters, but if there was such a need, the
35753 annotations could be extended with an @samp{escape} annotation which
35754 means those three characters as output.
35756 The annotation @var{level}, which is specified using the
35757 @option{--annotate} command line option (@pxref{Mode Options}), controls
35758 how much information @value{GDBN} prints together with its prompt,
35759 values of expressions, source lines, and other types of output. Level 0
35760 is for no annotations, level 1 is for use when @value{GDBN} is run as a
35761 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
35762 for programs that control @value{GDBN}, and level 2 annotations have
35763 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
35764 Interface, annotate, GDB's Obsolete Annotations}).
35767 @kindex set annotate
35768 @item set annotate @var{level}
35769 The @value{GDBN} command @code{set annotate} sets the level of
35770 annotations to the specified @var{level}.
35772 @item show annotate
35773 @kindex show annotate
35774 Show the current annotation level.
35777 This chapter describes level 3 annotations.
35779 A simple example of starting up @value{GDBN} with annotations is:
35782 $ @kbd{gdb --annotate=3}
35784 Copyright 2003 Free Software Foundation, Inc.
35785 GDB is free software, covered by the GNU General Public License,
35786 and you are welcome to change it and/or distribute copies of it
35787 under certain conditions.
35788 Type "show copying" to see the conditions.
35789 There is absolutely no warranty for GDB. Type "show warranty"
35791 This GDB was configured as "i386-pc-linux-gnu"
35802 Here @samp{quit} is input to @value{GDBN}; the rest is output from
35803 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
35804 denotes a @samp{control-z} character) are annotations; the rest is
35805 output from @value{GDBN}.
35807 @node Server Prefix
35808 @section The Server Prefix
35809 @cindex server prefix
35811 If you prefix a command with @samp{server } then it will not affect
35812 the command history, nor will it affect @value{GDBN}'s notion of which
35813 command to repeat if @key{RET} is pressed on a line by itself. This
35814 means that commands can be run behind a user's back by a front-end in
35815 a transparent manner.
35817 The @code{server } prefix does not affect the recording of values into
35818 the value history; to print a value without recording it into the
35819 value history, use the @code{output} command instead of the
35820 @code{print} command.
35822 Using this prefix also disables confirmation requests
35823 (@pxref{confirmation requests}).
35826 @section Annotation for @value{GDBN} Input
35828 @cindex annotations for prompts
35829 When @value{GDBN} prompts for input, it annotates this fact so it is possible
35830 to know when to send output, when the output from a given command is
35833 Different kinds of input each have a different @dfn{input type}. Each
35834 input type has three annotations: a @code{pre-} annotation, which
35835 denotes the beginning of any prompt which is being output, a plain
35836 annotation, which denotes the end of the prompt, and then a @code{post-}
35837 annotation which denotes the end of any echo which may (or may not) be
35838 associated with the input. For example, the @code{prompt} input type
35839 features the following annotations:
35847 The input types are
35850 @findex pre-prompt annotation
35851 @findex prompt annotation
35852 @findex post-prompt annotation
35854 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
35856 @findex pre-commands annotation
35857 @findex commands annotation
35858 @findex post-commands annotation
35860 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
35861 command. The annotations are repeated for each command which is input.
35863 @findex pre-overload-choice annotation
35864 @findex overload-choice annotation
35865 @findex post-overload-choice annotation
35866 @item overload-choice
35867 When @value{GDBN} wants the user to select between various overloaded functions.
35869 @findex pre-query annotation
35870 @findex query annotation
35871 @findex post-query annotation
35873 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
35875 @findex pre-prompt-for-continue annotation
35876 @findex prompt-for-continue annotation
35877 @findex post-prompt-for-continue annotation
35878 @item prompt-for-continue
35879 When @value{GDBN} is asking the user to press return to continue. Note: Don't
35880 expect this to work well; instead use @code{set height 0} to disable
35881 prompting. This is because the counting of lines is buggy in the
35882 presence of annotations.
35887 @cindex annotations for errors, warnings and interrupts
35889 @findex quit annotation
35894 This annotation occurs right before @value{GDBN} responds to an interrupt.
35896 @findex error annotation
35901 This annotation occurs right before @value{GDBN} responds to an error.
35903 Quit and error annotations indicate that any annotations which @value{GDBN} was
35904 in the middle of may end abruptly. For example, if a
35905 @code{value-history-begin} annotation is followed by a @code{error}, one
35906 cannot expect to receive the matching @code{value-history-end}. One
35907 cannot expect not to receive it either, however; an error annotation
35908 does not necessarily mean that @value{GDBN} is immediately returning all the way
35911 @findex error-begin annotation
35912 A quit or error annotation may be preceded by
35918 Any output between that and the quit or error annotation is the error
35921 Warning messages are not yet annotated.
35922 @c If we want to change that, need to fix warning(), type_error(),
35923 @c range_error(), and possibly other places.
35926 @section Invalidation Notices
35928 @cindex annotations for invalidation messages
35929 The following annotations say that certain pieces of state may have
35933 @findex frames-invalid annotation
35934 @item ^Z^Zframes-invalid
35936 The frames (for example, output from the @code{backtrace} command) may
35939 @findex breakpoints-invalid annotation
35940 @item ^Z^Zbreakpoints-invalid
35942 The breakpoints may have changed. For example, the user just added or
35943 deleted a breakpoint.
35946 @node Annotations for Running
35947 @section Running the Program
35948 @cindex annotations for running programs
35950 @findex starting annotation
35951 @findex stopping annotation
35952 When the program starts executing due to a @value{GDBN} command such as
35953 @code{step} or @code{continue},
35959 is output. When the program stops,
35965 is output. Before the @code{stopped} annotation, a variety of
35966 annotations describe how the program stopped.
35969 @findex exited annotation
35970 @item ^Z^Zexited @var{exit-status}
35971 The program exited, and @var{exit-status} is the exit status (zero for
35972 successful exit, otherwise nonzero).
35974 @findex signalled annotation
35975 @findex signal-name annotation
35976 @findex signal-name-end annotation
35977 @findex signal-string annotation
35978 @findex signal-string-end annotation
35979 @item ^Z^Zsignalled
35980 The program exited with a signal. After the @code{^Z^Zsignalled}, the
35981 annotation continues:
35987 ^Z^Zsignal-name-end
35991 ^Z^Zsignal-string-end
35996 where @var{name} is the name of the signal, such as @code{SIGILL} or
35997 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
35998 as @code{Illegal Instruction} or @code{Segmentation fault}.
35999 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
36000 user's benefit and have no particular format.
36002 @findex signal annotation
36004 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
36005 just saying that the program received the signal, not that it was
36006 terminated with it.
36008 @findex breakpoint annotation
36009 @item ^Z^Zbreakpoint @var{number}
36010 The program hit breakpoint number @var{number}.
36012 @findex watchpoint annotation
36013 @item ^Z^Zwatchpoint @var{number}
36014 The program hit watchpoint number @var{number}.
36017 @node Source Annotations
36018 @section Displaying Source
36019 @cindex annotations for source display
36021 @findex source annotation
36022 The following annotation is used instead of displaying source code:
36025 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
36028 where @var{filename} is an absolute file name indicating which source
36029 file, @var{line} is the line number within that file (where 1 is the
36030 first line in the file), @var{character} is the character position
36031 within the file (where 0 is the first character in the file) (for most
36032 debug formats this will necessarily point to the beginning of a line),
36033 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
36034 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
36035 @var{addr} is the address in the target program associated with the
36036 source which is being displayed. @var{addr} is in the form @samp{0x}
36037 followed by one or more lowercase hex digits (note that this does not
36038 depend on the language).
36040 @node JIT Interface
36041 @chapter JIT Compilation Interface
36042 @cindex just-in-time compilation
36043 @cindex JIT compilation interface
36045 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
36046 interface. A JIT compiler is a program or library that generates native
36047 executable code at runtime and executes it, usually in order to achieve good
36048 performance while maintaining platform independence.
36050 Programs that use JIT compilation are normally difficult to debug because
36051 portions of their code are generated at runtime, instead of being loaded from
36052 object files, which is where @value{GDBN} normally finds the program's symbols
36053 and debug information. In order to debug programs that use JIT compilation,
36054 @value{GDBN} has an interface that allows the program to register in-memory
36055 symbol files with @value{GDBN} at runtime.
36057 If you are using @value{GDBN} to debug a program that uses this interface, then
36058 it should work transparently so long as you have not stripped the binary. If
36059 you are developing a JIT compiler, then the interface is documented in the rest
36060 of this chapter. At this time, the only known client of this interface is the
36063 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
36064 JIT compiler communicates with @value{GDBN} by writing data into a global
36065 variable and calling a fuction at a well-known symbol. When @value{GDBN}
36066 attaches, it reads a linked list of symbol files from the global variable to
36067 find existing code, and puts a breakpoint in the function so that it can find
36068 out about additional code.
36071 * Declarations:: Relevant C struct declarations
36072 * Registering Code:: Steps to register code
36073 * Unregistering Code:: Steps to unregister code
36074 * Custom Debug Info:: Emit debug information in a custom format
36078 @section JIT Declarations
36080 These are the relevant struct declarations that a C program should include to
36081 implement the interface:
36091 struct jit_code_entry
36093 struct jit_code_entry *next_entry;
36094 struct jit_code_entry *prev_entry;
36095 const char *symfile_addr;
36096 uint64_t symfile_size;
36099 struct jit_descriptor
36102 /* This type should be jit_actions_t, but we use uint32_t
36103 to be explicit about the bitwidth. */
36104 uint32_t action_flag;
36105 struct jit_code_entry *relevant_entry;
36106 struct jit_code_entry *first_entry;
36109 /* GDB puts a breakpoint in this function. */
36110 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
36112 /* Make sure to specify the version statically, because the
36113 debugger may check the version before we can set it. */
36114 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
36117 If the JIT is multi-threaded, then it is important that the JIT synchronize any
36118 modifications to this global data properly, which can easily be done by putting
36119 a global mutex around modifications to these structures.
36121 @node Registering Code
36122 @section Registering Code
36124 To register code with @value{GDBN}, the JIT should follow this protocol:
36128 Generate an object file in memory with symbols and other desired debug
36129 information. The file must include the virtual addresses of the sections.
36132 Create a code entry for the file, which gives the start and size of the symbol
36136 Add it to the linked list in the JIT descriptor.
36139 Point the relevant_entry field of the descriptor at the entry.
36142 Set @code{action_flag} to @code{JIT_REGISTER} and call
36143 @code{__jit_debug_register_code}.
36146 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
36147 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
36148 new code. However, the linked list must still be maintained in order to allow
36149 @value{GDBN} to attach to a running process and still find the symbol files.
36151 @node Unregistering Code
36152 @section Unregistering Code
36154 If code is freed, then the JIT should use the following protocol:
36158 Remove the code entry corresponding to the code from the linked list.
36161 Point the @code{relevant_entry} field of the descriptor at the code entry.
36164 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
36165 @code{__jit_debug_register_code}.
36168 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
36169 and the JIT will leak the memory used for the associated symbol files.
36171 @node Custom Debug Info
36172 @section Custom Debug Info
36173 @cindex custom JIT debug info
36174 @cindex JIT debug info reader
36176 Generating debug information in platform-native file formats (like ELF
36177 or COFF) may be an overkill for JIT compilers; especially if all the
36178 debug info is used for is displaying a meaningful backtrace. The
36179 issue can be resolved by having the JIT writers decide on a debug info
36180 format and also provide a reader that parses the debug info generated
36181 by the JIT compiler. This section gives a brief overview on writing
36182 such a parser. More specific details can be found in the source file
36183 @file{gdb/jit-reader.in}, which is also installed as a header at
36184 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
36186 The reader is implemented as a shared object (so this functionality is
36187 not available on platforms which don't allow loading shared objects at
36188 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
36189 @code{jit-reader-unload} are provided, to be used to load and unload
36190 the readers from a preconfigured directory. Once loaded, the shared
36191 object is used the parse the debug information emitted by the JIT
36195 * Using JIT Debug Info Readers:: How to use supplied readers correctly
36196 * Writing JIT Debug Info Readers:: Creating a debug-info reader
36199 @node Using JIT Debug Info Readers
36200 @subsection Using JIT Debug Info Readers
36201 @kindex jit-reader-load
36202 @kindex jit-reader-unload
36204 Readers can be loaded and unloaded using the @code{jit-reader-load}
36205 and @code{jit-reader-unload} commands.
36208 @item jit-reader-load @var{reader}
36209 Load the JIT reader named @var{reader}. @var{reader} is a shared
36210 object specified as either an absolute or a relative file name. In
36211 the latter case, @value{GDBN} will try to load the reader from a
36212 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
36213 system (here @var{libdir} is the system library directory, often
36214 @file{/usr/local/lib}).
36216 Only one reader can be active at a time; trying to load a second
36217 reader when one is already loaded will result in @value{GDBN}
36218 reporting an error. A new JIT reader can be loaded by first unloading
36219 the current one using @code{jit-reader-unload} and then invoking
36220 @code{jit-reader-load}.
36222 @item jit-reader-unload
36223 Unload the currently loaded JIT reader.
36227 @node Writing JIT Debug Info Readers
36228 @subsection Writing JIT Debug Info Readers
36229 @cindex writing JIT debug info readers
36231 As mentioned, a reader is essentially a shared object conforming to a
36232 certain ABI. This ABI is described in @file{jit-reader.h}.
36234 @file{jit-reader.h} defines the structures, macros and functions
36235 required to write a reader. It is installed (along with
36236 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
36237 the system include directory.
36239 Readers need to be released under a GPL compatible license. A reader
36240 can be declared as released under such a license by placing the macro
36241 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
36243 The entry point for readers is the symbol @code{gdb_init_reader},
36244 which is expected to be a function with the prototype
36246 @findex gdb_init_reader
36248 extern struct gdb_reader_funcs *gdb_init_reader (void);
36251 @cindex @code{struct gdb_reader_funcs}
36253 @code{struct gdb_reader_funcs} contains a set of pointers to callback
36254 functions. These functions are executed to read the debug info
36255 generated by the JIT compiler (@code{read}), to unwind stack frames
36256 (@code{unwind}) and to create canonical frame IDs
36257 (@code{get_Frame_id}). It also has a callback that is called when the
36258 reader is being unloaded (@code{destroy}). The struct looks like this
36261 struct gdb_reader_funcs
36263 /* Must be set to GDB_READER_INTERFACE_VERSION. */
36264 int reader_version;
36266 /* For use by the reader. */
36269 gdb_read_debug_info *read;
36270 gdb_unwind_frame *unwind;
36271 gdb_get_frame_id *get_frame_id;
36272 gdb_destroy_reader *destroy;
36276 @cindex @code{struct gdb_symbol_callbacks}
36277 @cindex @code{struct gdb_unwind_callbacks}
36279 The callbacks are provided with another set of callbacks by
36280 @value{GDBN} to do their job. For @code{read}, these callbacks are
36281 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
36282 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
36283 @code{struct gdb_symbol_callbacks} has callbacks to create new object
36284 files and new symbol tables inside those object files. @code{struct
36285 gdb_unwind_callbacks} has callbacks to read registers off the current
36286 frame and to write out the values of the registers in the previous
36287 frame. Both have a callback (@code{target_read}) to read bytes off the
36288 target's address space.
36290 @node In-Process Agent
36291 @chapter In-Process Agent
36292 @cindex debugging agent
36293 The traditional debugging model is conceptually low-speed, but works fine,
36294 because most bugs can be reproduced in debugging-mode execution. However,
36295 as multi-core or many-core processors are becoming mainstream, and
36296 multi-threaded programs become more and more popular, there should be more
36297 and more bugs that only manifest themselves at normal-mode execution, for
36298 example, thread races, because debugger's interference with the program's
36299 timing may conceal the bugs. On the other hand, in some applications,
36300 it is not feasible for the debugger to interrupt the program's execution
36301 long enough for the developer to learn anything helpful about its behavior.
36302 If the program's correctness depends on its real-time behavior, delays
36303 introduced by a debugger might cause the program to fail, even when the
36304 code itself is correct. It is useful to be able to observe the program's
36305 behavior without interrupting it.
36307 Therefore, traditional debugging model is too intrusive to reproduce
36308 some bugs. In order to reduce the interference with the program, we can
36309 reduce the number of operations performed by debugger. The
36310 @dfn{In-Process Agent}, a shared library, is running within the same
36311 process with inferior, and is able to perform some debugging operations
36312 itself. As a result, debugger is only involved when necessary, and
36313 performance of debugging can be improved accordingly. Note that
36314 interference with program can be reduced but can't be removed completely,
36315 because the in-process agent will still stop or slow down the program.
36317 The in-process agent can interpret and execute Agent Expressions
36318 (@pxref{Agent Expressions}) during performing debugging operations. The
36319 agent expressions can be used for different purposes, such as collecting
36320 data in tracepoints, and condition evaluation in breakpoints.
36322 @anchor{Control Agent}
36323 You can control whether the in-process agent is used as an aid for
36324 debugging with the following commands:
36327 @kindex set agent on
36329 Causes the in-process agent to perform some operations on behalf of the
36330 debugger. Just which operations requested by the user will be done
36331 by the in-process agent depends on the its capabilities. For example,
36332 if you request to evaluate breakpoint conditions in the in-process agent,
36333 and the in-process agent has such capability as well, then breakpoint
36334 conditions will be evaluated in the in-process agent.
36336 @kindex set agent off
36337 @item set agent off
36338 Disables execution of debugging operations by the in-process agent. All
36339 of the operations will be performed by @value{GDBN}.
36343 Display the current setting of execution of debugging operations by
36344 the in-process agent.
36348 * In-Process Agent Protocol::
36351 @node In-Process Agent Protocol
36352 @section In-Process Agent Protocol
36353 @cindex in-process agent protocol
36355 The in-process agent is able to communicate with both @value{GDBN} and
36356 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
36357 used for communications between @value{GDBN} or GDBserver and the IPA.
36358 In general, @value{GDBN} or GDBserver sends commands
36359 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
36360 in-process agent replies back with the return result of the command, or
36361 some other information. The data sent to in-process agent is composed
36362 of primitive data types, such as 4-byte or 8-byte type, and composite
36363 types, which are called objects (@pxref{IPA Protocol Objects}).
36366 * IPA Protocol Objects::
36367 * IPA Protocol Commands::
36370 @node IPA Protocol Objects
36371 @subsection IPA Protocol Objects
36372 @cindex ipa protocol objects
36374 The commands sent to and results received from agent may contain some
36375 complex data types called @dfn{objects}.
36377 The in-process agent is running on the same machine with @value{GDBN}
36378 or GDBserver, so it doesn't have to handle as much differences between
36379 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
36380 However, there are still some differences of two ends in two processes:
36384 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
36385 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
36387 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
36388 GDBserver is compiled with one, and in-process agent is compiled with
36392 Here are the IPA Protocol Objects:
36396 agent expression object. It represents an agent expression
36397 (@pxref{Agent Expressions}).
36398 @anchor{agent expression object}
36400 tracepoint action object. It represents a tracepoint action
36401 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
36402 memory, static trace data and to evaluate expression.
36403 @anchor{tracepoint action object}
36405 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
36406 @anchor{tracepoint object}
36410 The following table describes important attributes of each IPA protocol
36413 @multitable @columnfractions .30 .20 .50
36414 @headitem Name @tab Size @tab Description
36415 @item @emph{agent expression object} @tab @tab
36416 @item length @tab 4 @tab length of bytes code
36417 @item byte code @tab @var{length} @tab contents of byte code
36418 @item @emph{tracepoint action for collecting memory} @tab @tab
36419 @item 'M' @tab 1 @tab type of tracepoint action
36420 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
36421 address of the lowest byte to collect, otherwise @var{addr} is the offset
36422 of @var{basereg} for memory collecting.
36423 @item len @tab 8 @tab length of memory for collecting
36424 @item basereg @tab 4 @tab the register number containing the starting
36425 memory address for collecting.
36426 @item @emph{tracepoint action for collecting registers} @tab @tab
36427 @item 'R' @tab 1 @tab type of tracepoint action
36428 @item @emph{tracepoint action for collecting static trace data} @tab @tab
36429 @item 'L' @tab 1 @tab type of tracepoint action
36430 @item @emph{tracepoint action for expression evaluation} @tab @tab
36431 @item 'X' @tab 1 @tab type of tracepoint action
36432 @item agent expression @tab length of @tab @ref{agent expression object}
36433 @item @emph{tracepoint object} @tab @tab
36434 @item number @tab 4 @tab number of tracepoint
36435 @item address @tab 8 @tab address of tracepoint inserted on
36436 @item type @tab 4 @tab type of tracepoint
36437 @item enabled @tab 1 @tab enable or disable of tracepoint
36438 @item step_count @tab 8 @tab step
36439 @item pass_count @tab 8 @tab pass
36440 @item numactions @tab 4 @tab number of tracepoint actions
36441 @item hit count @tab 8 @tab hit count
36442 @item trace frame usage @tab 8 @tab trace frame usage
36443 @item compiled_cond @tab 8 @tab compiled condition
36444 @item orig_size @tab 8 @tab orig size
36445 @item condition @tab 4 if condition is NULL otherwise length of
36446 @ref{agent expression object}
36447 @tab zero if condition is NULL, otherwise is
36448 @ref{agent expression object}
36449 @item actions @tab variable
36450 @tab numactions number of @ref{tracepoint action object}
36453 @node IPA Protocol Commands
36454 @subsection IPA Protocol Commands
36455 @cindex ipa protocol commands
36457 The spaces in each command are delimiters to ease reading this commands
36458 specification. They don't exist in real commands.
36462 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
36463 Installs a new fast tracepoint described by @var{tracepoint_object}
36464 (@pxref{tracepoint object}). @var{gdb_jump_pad_head}, 8-byte long, is the
36465 head of @dfn{jumppad}, which is used to jump to data collection routine
36470 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
36471 @var{target_address} is address of tracepoint in the inferior.
36472 @var{gdb_jump_pad_head} is updated head of jumppad. Both of
36473 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
36474 @var{fjump} contains a sequence of instructions jump to jumppad entry.
36475 @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
36482 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
36483 is about to kill inferiors.
36491 @item probe_marker_at:@var{address}
36492 Asks in-process agent to probe the marker at @var{address}.
36499 @item unprobe_marker_at:@var{address}
36500 Asks in-process agent to unprobe the marker at @var{address}.
36504 @chapter Reporting Bugs in @value{GDBN}
36505 @cindex bugs in @value{GDBN}
36506 @cindex reporting bugs in @value{GDBN}
36508 Your bug reports play an essential role in making @value{GDBN} reliable.
36510 Reporting a bug may help you by bringing a solution to your problem, or it
36511 may not. But in any case the principal function of a bug report is to help
36512 the entire community by making the next version of @value{GDBN} work better. Bug
36513 reports are your contribution to the maintenance of @value{GDBN}.
36515 In order for a bug report to serve its purpose, you must include the
36516 information that enables us to fix the bug.
36519 * Bug Criteria:: Have you found a bug?
36520 * Bug Reporting:: How to report bugs
36524 @section Have You Found a Bug?
36525 @cindex bug criteria
36527 If you are not sure whether you have found a bug, here are some guidelines:
36530 @cindex fatal signal
36531 @cindex debugger crash
36532 @cindex crash of debugger
36534 If the debugger gets a fatal signal, for any input whatever, that is a
36535 @value{GDBN} bug. Reliable debuggers never crash.
36537 @cindex error on valid input
36539 If @value{GDBN} produces an error message for valid input, that is a
36540 bug. (Note that if you're cross debugging, the problem may also be
36541 somewhere in the connection to the target.)
36543 @cindex invalid input
36545 If @value{GDBN} does not produce an error message for invalid input,
36546 that is a bug. However, you should note that your idea of
36547 ``invalid input'' might be our idea of ``an extension'' or ``support
36548 for traditional practice''.
36551 If you are an experienced user of debugging tools, your suggestions
36552 for improvement of @value{GDBN} are welcome in any case.
36555 @node Bug Reporting
36556 @section How to Report Bugs
36557 @cindex bug reports
36558 @cindex @value{GDBN} bugs, reporting
36560 A number of companies and individuals offer support for @sc{gnu} products.
36561 If you obtained @value{GDBN} from a support organization, we recommend you
36562 contact that organization first.
36564 You can find contact information for many support companies and
36565 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
36567 @c should add a web page ref...
36570 @ifset BUGURL_DEFAULT
36571 In any event, we also recommend that you submit bug reports for
36572 @value{GDBN}. The preferred method is to submit them directly using
36573 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
36574 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
36577 @strong{Do not send bug reports to @samp{info-gdb}, or to
36578 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
36579 not want to receive bug reports. Those that do have arranged to receive
36582 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
36583 serves as a repeater. The mailing list and the newsgroup carry exactly
36584 the same messages. Often people think of posting bug reports to the
36585 newsgroup instead of mailing them. This appears to work, but it has one
36586 problem which can be crucial: a newsgroup posting often lacks a mail
36587 path back to the sender. Thus, if we need to ask for more information,
36588 we may be unable to reach you. For this reason, it is better to send
36589 bug reports to the mailing list.
36591 @ifclear BUGURL_DEFAULT
36592 In any event, we also recommend that you submit bug reports for
36593 @value{GDBN} to @value{BUGURL}.
36597 The fundamental principle of reporting bugs usefully is this:
36598 @strong{report all the facts}. If you are not sure whether to state a
36599 fact or leave it out, state it!
36601 Often people omit facts because they think they know what causes the
36602 problem and assume that some details do not matter. Thus, you might
36603 assume that the name of the variable you use in an example does not matter.
36604 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
36605 stray memory reference which happens to fetch from the location where that
36606 name is stored in memory; perhaps, if the name were different, the contents
36607 of that location would fool the debugger into doing the right thing despite
36608 the bug. Play it safe and give a specific, complete example. That is the
36609 easiest thing for you to do, and the most helpful.
36611 Keep in mind that the purpose of a bug report is to enable us to fix the
36612 bug. It may be that the bug has been reported previously, but neither
36613 you nor we can know that unless your bug report is complete and
36616 Sometimes people give a few sketchy facts and ask, ``Does this ring a
36617 bell?'' Those bug reports are useless, and we urge everyone to
36618 @emph{refuse to respond to them} except to chide the sender to report
36621 To enable us to fix the bug, you should include all these things:
36625 The version of @value{GDBN}. @value{GDBN} announces it if you start
36626 with no arguments; you can also print it at any time using @code{show
36629 Without this, we will not know whether there is any point in looking for
36630 the bug in the current version of @value{GDBN}.
36633 The type of machine you are using, and the operating system name and
36637 The details of the @value{GDBN} build-time configuration.
36638 @value{GDBN} shows these details if you invoke it with the
36639 @option{--configuration} command-line option, or if you type
36640 @code{show configuration} at @value{GDBN}'s prompt.
36643 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
36644 ``@value{GCC}--2.8.1''.
36647 What compiler (and its version) was used to compile the program you are
36648 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
36649 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
36650 to get this information; for other compilers, see the documentation for
36654 The command arguments you gave the compiler to compile your example and
36655 observe the bug. For example, did you use @samp{-O}? To guarantee
36656 you will not omit something important, list them all. A copy of the
36657 Makefile (or the output from make) is sufficient.
36659 If we were to try to guess the arguments, we would probably guess wrong
36660 and then we might not encounter the bug.
36663 A complete input script, and all necessary source files, that will
36667 A description of what behavior you observe that you believe is
36668 incorrect. For example, ``It gets a fatal signal.''
36670 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
36671 will certainly notice it. But if the bug is incorrect output, we might
36672 not notice unless it is glaringly wrong. You might as well not give us
36673 a chance to make a mistake.
36675 Even if the problem you experience is a fatal signal, you should still
36676 say so explicitly. Suppose something strange is going on, such as, your
36677 copy of @value{GDBN} is out of synch, or you have encountered a bug in
36678 the C library on your system. (This has happened!) Your copy might
36679 crash and ours would not. If you told us to expect a crash, then when
36680 ours fails to crash, we would know that the bug was not happening for
36681 us. If you had not told us to expect a crash, then we would not be able
36682 to draw any conclusion from our observations.
36685 @cindex recording a session script
36686 To collect all this information, you can use a session recording program
36687 such as @command{script}, which is available on many Unix systems.
36688 Just run your @value{GDBN} session inside @command{script} and then
36689 include the @file{typescript} file with your bug report.
36691 Another way to record a @value{GDBN} session is to run @value{GDBN}
36692 inside Emacs and then save the entire buffer to a file.
36695 If you wish to suggest changes to the @value{GDBN} source, send us context
36696 diffs. If you even discuss something in the @value{GDBN} source, refer to
36697 it by context, not by line number.
36699 The line numbers in our development sources will not match those in your
36700 sources. Your line numbers would convey no useful information to us.
36704 Here are some things that are not necessary:
36708 A description of the envelope of the bug.
36710 Often people who encounter a bug spend a lot of time investigating
36711 which changes to the input file will make the bug go away and which
36712 changes will not affect it.
36714 This is often time consuming and not very useful, because the way we
36715 will find the bug is by running a single example under the debugger
36716 with breakpoints, not by pure deduction from a series of examples.
36717 We recommend that you save your time for something else.
36719 Of course, if you can find a simpler example to report @emph{instead}
36720 of the original one, that is a convenience for us. Errors in the
36721 output will be easier to spot, running under the debugger will take
36722 less time, and so on.
36724 However, simplification is not vital; if you do not want to do this,
36725 report the bug anyway and send us the entire test case you used.
36728 A patch for the bug.
36730 A patch for the bug does help us if it is a good one. But do not omit
36731 the necessary information, such as the test case, on the assumption that
36732 a patch is all we need. We might see problems with your patch and decide
36733 to fix the problem another way, or we might not understand it at all.
36735 Sometimes with a program as complicated as @value{GDBN} it is very hard to
36736 construct an example that will make the program follow a certain path
36737 through the code. If you do not send us the example, we will not be able
36738 to construct one, so we will not be able to verify that the bug is fixed.
36740 And if we cannot understand what bug you are trying to fix, or why your
36741 patch should be an improvement, we will not install it. A test case will
36742 help us to understand.
36745 A guess about what the bug is or what it depends on.
36747 Such guesses are usually wrong. Even we cannot guess right about such
36748 things without first using the debugger to find the facts.
36751 @c The readline documentation is distributed with the readline code
36752 @c and consists of the two following files:
36755 @c Use -I with makeinfo to point to the appropriate directory,
36756 @c environment var TEXINPUTS with TeX.
36757 @ifclear SYSTEM_READLINE
36758 @include rluser.texi
36759 @include hsuser.texi
36763 @appendix In Memoriam
36765 The @value{GDBN} project mourns the loss of the following long-time
36770 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
36771 to Free Software in general. Outside of @value{GDBN}, he was known in
36772 the Amiga world for his series of Fish Disks, and the GeekGadget project.
36774 @item Michael Snyder
36775 Michael was one of the Global Maintainers of the @value{GDBN} project,
36776 with contributions recorded as early as 1996, until 2011. In addition
36777 to his day to day participation, he was a large driving force behind
36778 adding Reverse Debugging to @value{GDBN}.
36781 Beyond their technical contributions to the project, they were also
36782 enjoyable members of the Free Software Community. We will miss them.
36784 @node Formatting Documentation
36785 @appendix Formatting Documentation
36787 @cindex @value{GDBN} reference card
36788 @cindex reference card
36789 The @value{GDBN} 4 release includes an already-formatted reference card, ready
36790 for printing with PostScript or Ghostscript, in the @file{gdb}
36791 subdirectory of the main source directory@footnote{In
36792 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
36793 release.}. If you can use PostScript or Ghostscript with your printer,
36794 you can print the reference card immediately with @file{refcard.ps}.
36796 The release also includes the source for the reference card. You
36797 can format it, using @TeX{}, by typing:
36803 The @value{GDBN} reference card is designed to print in @dfn{landscape}
36804 mode on US ``letter'' size paper;
36805 that is, on a sheet 11 inches wide by 8.5 inches
36806 high. You will need to specify this form of printing as an option to
36807 your @sc{dvi} output program.
36809 @cindex documentation
36811 All the documentation for @value{GDBN} comes as part of the machine-readable
36812 distribution. The documentation is written in Texinfo format, which is
36813 a documentation system that uses a single source file to produce both
36814 on-line information and a printed manual. You can use one of the Info
36815 formatting commands to create the on-line version of the documentation
36816 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
36818 @value{GDBN} includes an already formatted copy of the on-line Info
36819 version of this manual in the @file{gdb} subdirectory. The main Info
36820 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
36821 subordinate files matching @samp{gdb.info*} in the same directory. If
36822 necessary, you can print out these files, or read them with any editor;
36823 but they are easier to read using the @code{info} subsystem in @sc{gnu}
36824 Emacs or the standalone @code{info} program, available as part of the
36825 @sc{gnu} Texinfo distribution.
36827 If you want to format these Info files yourself, you need one of the
36828 Info formatting programs, such as @code{texinfo-format-buffer} or
36831 If you have @code{makeinfo} installed, and are in the top level
36832 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
36833 version @value{GDBVN}), you can make the Info file by typing:
36840 If you want to typeset and print copies of this manual, you need @TeX{},
36841 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
36842 Texinfo definitions file.
36844 @TeX{} is a typesetting program; it does not print files directly, but
36845 produces output files called @sc{dvi} files. To print a typeset
36846 document, you need a program to print @sc{dvi} files. If your system
36847 has @TeX{} installed, chances are it has such a program. The precise
36848 command to use depends on your system; @kbd{lpr -d} is common; another
36849 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
36850 require a file name without any extension or a @samp{.dvi} extension.
36852 @TeX{} also requires a macro definitions file called
36853 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
36854 written in Texinfo format. On its own, @TeX{} cannot either read or
36855 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
36856 and is located in the @file{gdb-@var{version-number}/texinfo}
36859 If you have @TeX{} and a @sc{dvi} printer program installed, you can
36860 typeset and print this manual. First switch to the @file{gdb}
36861 subdirectory of the main source directory (for example, to
36862 @file{gdb-@value{GDBVN}/gdb}) and type:
36868 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
36870 @node Installing GDB
36871 @appendix Installing @value{GDBN}
36872 @cindex installation
36875 * Requirements:: Requirements for building @value{GDBN}
36876 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
36877 * Separate Objdir:: Compiling @value{GDBN} in another directory
36878 * Config Names:: Specifying names for hosts and targets
36879 * Configure Options:: Summary of options for configure
36880 * System-wide configuration:: Having a system-wide init file
36884 @section Requirements for Building @value{GDBN}
36885 @cindex building @value{GDBN}, requirements for
36887 Building @value{GDBN} requires various tools and packages to be available.
36888 Other packages will be used only if they are found.
36890 @heading Tools/Packages Necessary for Building @value{GDBN}
36892 @item ISO C90 compiler
36893 @value{GDBN} is written in ISO C90. It should be buildable with any
36894 working C90 compiler, e.g.@: GCC.
36898 @heading Tools/Packages Optional for Building @value{GDBN}
36902 @value{GDBN} can use the Expat XML parsing library. This library may be
36903 included with your operating system distribution; if it is not, you
36904 can get the latest version from @url{http://expat.sourceforge.net}.
36905 The @file{configure} script will search for this library in several
36906 standard locations; if it is installed in an unusual path, you can
36907 use the @option{--with-libexpat-prefix} option to specify its location.
36913 Remote protocol memory maps (@pxref{Memory Map Format})
36915 Target descriptions (@pxref{Target Descriptions})
36917 Remote shared library lists (@xref{Library List Format},
36918 or alternatively @pxref{Library List Format for SVR4 Targets})
36920 MS-Windows shared libraries (@pxref{Shared Libraries})
36922 Traceframe info (@pxref{Traceframe Info Format})
36924 Branch trace (@pxref{Branch Trace Format})
36928 @cindex compressed debug sections
36929 @value{GDBN} will use the @samp{zlib} library, if available, to read
36930 compressed debug sections. Some linkers, such as GNU gold, are capable
36931 of producing binaries with compressed debug sections. If @value{GDBN}
36932 is compiled with @samp{zlib}, it will be able to read the debug
36933 information in such binaries.
36935 The @samp{zlib} library is likely included with your operating system
36936 distribution; if it is not, you can get the latest version from
36937 @url{http://zlib.net}.
36940 @value{GDBN}'s features related to character sets (@pxref{Character
36941 Sets}) require a functioning @code{iconv} implementation. If you are
36942 on a GNU system, then this is provided by the GNU C Library. Some
36943 other systems also provide a working @code{iconv}.
36945 If @value{GDBN} is using the @code{iconv} program which is installed
36946 in a non-standard place, you will need to tell @value{GDBN} where to find it.
36947 This is done with @option{--with-iconv-bin} which specifies the
36948 directory that contains the @code{iconv} program.
36950 On systems without @code{iconv}, you can install GNU Libiconv. If you
36951 have previously installed Libiconv, you can use the
36952 @option{--with-libiconv-prefix} option to configure.
36954 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
36955 arrange to build Libiconv if a directory named @file{libiconv} appears
36956 in the top-most source directory. If Libiconv is built this way, and
36957 if the operating system does not provide a suitable @code{iconv}
36958 implementation, then the just-built library will automatically be used
36959 by @value{GDBN}. One easy way to set this up is to download GNU
36960 Libiconv, unpack it, and then rename the directory holding the
36961 Libiconv source code to @samp{libiconv}.
36964 @node Running Configure
36965 @section Invoking the @value{GDBN} @file{configure} Script
36966 @cindex configuring @value{GDBN}
36967 @value{GDBN} comes with a @file{configure} script that automates the process
36968 of preparing @value{GDBN} for installation; you can then use @code{make} to
36969 build the @code{gdb} program.
36971 @c irrelevant in info file; it's as current as the code it lives with.
36972 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
36973 look at the @file{README} file in the sources; we may have improved the
36974 installation procedures since publishing this manual.}
36977 The @value{GDBN} distribution includes all the source code you need for
36978 @value{GDBN} in a single directory, whose name is usually composed by
36979 appending the version number to @samp{gdb}.
36981 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
36982 @file{gdb-@value{GDBVN}} directory. That directory contains:
36985 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
36986 script for configuring @value{GDBN} and all its supporting libraries
36988 @item gdb-@value{GDBVN}/gdb
36989 the source specific to @value{GDBN} itself
36991 @item gdb-@value{GDBVN}/bfd
36992 source for the Binary File Descriptor library
36994 @item gdb-@value{GDBVN}/include
36995 @sc{gnu} include files
36997 @item gdb-@value{GDBVN}/libiberty
36998 source for the @samp{-liberty} free software library
37000 @item gdb-@value{GDBVN}/opcodes
37001 source for the library of opcode tables and disassemblers
37003 @item gdb-@value{GDBVN}/readline
37004 source for the @sc{gnu} command-line interface
37006 @item gdb-@value{GDBVN}/glob
37007 source for the @sc{gnu} filename pattern-matching subroutine
37009 @item gdb-@value{GDBVN}/mmalloc
37010 source for the @sc{gnu} memory-mapped malloc package
37013 The simplest way to configure and build @value{GDBN} is to run @file{configure}
37014 from the @file{gdb-@var{version-number}} source directory, which in
37015 this example is the @file{gdb-@value{GDBVN}} directory.
37017 First switch to the @file{gdb-@var{version-number}} source directory
37018 if you are not already in it; then run @file{configure}. Pass the
37019 identifier for the platform on which @value{GDBN} will run as an
37025 cd gdb-@value{GDBVN}
37026 ./configure @var{host}
37031 where @var{host} is an identifier such as @samp{sun4} or
37032 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
37033 (You can often leave off @var{host}; @file{configure} tries to guess the
37034 correct value by examining your system.)
37036 Running @samp{configure @var{host}} and then running @code{make} builds the
37037 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
37038 libraries, then @code{gdb} itself. The configured source files, and the
37039 binaries, are left in the corresponding source directories.
37042 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
37043 system does not recognize this automatically when you run a different
37044 shell, you may need to run @code{sh} on it explicitly:
37047 sh configure @var{host}
37050 If you run @file{configure} from a directory that contains source
37051 directories for multiple libraries or programs, such as the
37052 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
37054 creates configuration files for every directory level underneath (unless
37055 you tell it not to, with the @samp{--norecursion} option).
37057 You should run the @file{configure} script from the top directory in the
37058 source tree, the @file{gdb-@var{version-number}} directory. If you run
37059 @file{configure} from one of the subdirectories, you will configure only
37060 that subdirectory. That is usually not what you want. In particular,
37061 if you run the first @file{configure} from the @file{gdb} subdirectory
37062 of the @file{gdb-@var{version-number}} directory, you will omit the
37063 configuration of @file{bfd}, @file{readline}, and other sibling
37064 directories of the @file{gdb} subdirectory. This leads to build errors
37065 about missing include files such as @file{bfd/bfd.h}.
37067 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
37068 However, you should make sure that the shell on your path (named by
37069 the @samp{SHELL} environment variable) is publicly readable. Remember
37070 that @value{GDBN} uses the shell to start your program---some systems refuse to
37071 let @value{GDBN} debug child processes whose programs are not readable.
37073 @node Separate Objdir
37074 @section Compiling @value{GDBN} in Another Directory
37076 If you want to run @value{GDBN} versions for several host or target machines,
37077 you need a different @code{gdb} compiled for each combination of
37078 host and target. @file{configure} is designed to make this easy by
37079 allowing you to generate each configuration in a separate subdirectory,
37080 rather than in the source directory. If your @code{make} program
37081 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
37082 @code{make} in each of these directories builds the @code{gdb}
37083 program specified there.
37085 To build @code{gdb} in a separate directory, run @file{configure}
37086 with the @samp{--srcdir} option to specify where to find the source.
37087 (You also need to specify a path to find @file{configure}
37088 itself from your working directory. If the path to @file{configure}
37089 would be the same as the argument to @samp{--srcdir}, you can leave out
37090 the @samp{--srcdir} option; it is assumed.)
37092 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
37093 separate directory for a Sun 4 like this:
37097 cd gdb-@value{GDBVN}
37100 ../gdb-@value{GDBVN}/configure sun4
37105 When @file{configure} builds a configuration using a remote source
37106 directory, it creates a tree for the binaries with the same structure
37107 (and using the same names) as the tree under the source directory. In
37108 the example, you'd find the Sun 4 library @file{libiberty.a} in the
37109 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
37110 @file{gdb-sun4/gdb}.
37112 Make sure that your path to the @file{configure} script has just one
37113 instance of @file{gdb} in it. If your path to @file{configure} looks
37114 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
37115 one subdirectory of @value{GDBN}, not the whole package. This leads to
37116 build errors about missing include files such as @file{bfd/bfd.h}.
37118 One popular reason to build several @value{GDBN} configurations in separate
37119 directories is to configure @value{GDBN} for cross-compiling (where
37120 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
37121 programs that run on another machine---the @dfn{target}).
37122 You specify a cross-debugging target by
37123 giving the @samp{--target=@var{target}} option to @file{configure}.
37125 When you run @code{make} to build a program or library, you must run
37126 it in a configured directory---whatever directory you were in when you
37127 called @file{configure} (or one of its subdirectories).
37129 The @code{Makefile} that @file{configure} generates in each source
37130 directory also runs recursively. If you type @code{make} in a source
37131 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
37132 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
37133 will build all the required libraries, and then build GDB.
37135 When you have multiple hosts or targets configured in separate
37136 directories, you can run @code{make} on them in parallel (for example,
37137 if they are NFS-mounted on each of the hosts); they will not interfere
37141 @section Specifying Names for Hosts and Targets
37143 The specifications used for hosts and targets in the @file{configure}
37144 script are based on a three-part naming scheme, but some short predefined
37145 aliases are also supported. The full naming scheme encodes three pieces
37146 of information in the following pattern:
37149 @var{architecture}-@var{vendor}-@var{os}
37152 For example, you can use the alias @code{sun4} as a @var{host} argument,
37153 or as the value for @var{target} in a @code{--target=@var{target}}
37154 option. The equivalent full name is @samp{sparc-sun-sunos4}.
37156 The @file{configure} script accompanying @value{GDBN} does not provide
37157 any query facility to list all supported host and target names or
37158 aliases. @file{configure} calls the Bourne shell script
37159 @code{config.sub} to map abbreviations to full names; you can read the
37160 script, if you wish, or you can use it to test your guesses on
37161 abbreviations---for example:
37164 % sh config.sub i386-linux
37166 % sh config.sub alpha-linux
37167 alpha-unknown-linux-gnu
37168 % sh config.sub hp9k700
37170 % sh config.sub sun4
37171 sparc-sun-sunos4.1.1
37172 % sh config.sub sun3
37173 m68k-sun-sunos4.1.1
37174 % sh config.sub i986v
37175 Invalid configuration `i986v': machine `i986v' not recognized
37179 @code{config.sub} is also distributed in the @value{GDBN} source
37180 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
37182 @node Configure Options
37183 @section @file{configure} Options
37185 Here is a summary of the @file{configure} options and arguments that
37186 are most often useful for building @value{GDBN}. @file{configure} also has
37187 several other options not listed here. @inforef{What Configure
37188 Does,,configure.info}, for a full explanation of @file{configure}.
37191 configure @r{[}--help@r{]}
37192 @r{[}--prefix=@var{dir}@r{]}
37193 @r{[}--exec-prefix=@var{dir}@r{]}
37194 @r{[}--srcdir=@var{dirname}@r{]}
37195 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
37196 @r{[}--target=@var{target}@r{]}
37201 You may introduce options with a single @samp{-} rather than
37202 @samp{--} if you prefer; but you may abbreviate option names if you use
37207 Display a quick summary of how to invoke @file{configure}.
37209 @item --prefix=@var{dir}
37210 Configure the source to install programs and files under directory
37213 @item --exec-prefix=@var{dir}
37214 Configure the source to install programs under directory
37217 @c avoid splitting the warning from the explanation:
37219 @item --srcdir=@var{dirname}
37220 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
37221 @code{make} that implements the @code{VPATH} feature.}@*
37222 Use this option to make configurations in directories separate from the
37223 @value{GDBN} source directories. Among other things, you can use this to
37224 build (or maintain) several configurations simultaneously, in separate
37225 directories. @file{configure} writes configuration-specific files in
37226 the current directory, but arranges for them to use the source in the
37227 directory @var{dirname}. @file{configure} creates directories under
37228 the working directory in parallel to the source directories below
37231 @item --norecursion
37232 Configure only the directory level where @file{configure} is executed; do not
37233 propagate configuration to subdirectories.
37235 @item --target=@var{target}
37236 Configure @value{GDBN} for cross-debugging programs running on the specified
37237 @var{target}. Without this option, @value{GDBN} is configured to debug
37238 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
37240 There is no convenient way to generate a list of all available targets.
37242 @item @var{host} @dots{}
37243 Configure @value{GDBN} to run on the specified @var{host}.
37245 There is no convenient way to generate a list of all available hosts.
37248 There are many other options available as well, but they are generally
37249 needed for special purposes only.
37251 @node System-wide configuration
37252 @section System-wide configuration and settings
37253 @cindex system-wide init file
37255 @value{GDBN} can be configured to have a system-wide init file;
37256 this file will be read and executed at startup (@pxref{Startup, , What
37257 @value{GDBN} does during startup}).
37259 Here is the corresponding configure option:
37262 @item --with-system-gdbinit=@var{file}
37263 Specify that the default location of the system-wide init file is
37267 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
37268 it may be subject to relocation. Two possible cases:
37272 If the default location of this init file contains @file{$prefix},
37273 it will be subject to relocation. Suppose that the configure options
37274 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
37275 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
37276 init file is looked for as @file{$install/etc/gdbinit} instead of
37277 @file{$prefix/etc/gdbinit}.
37280 By contrast, if the default location does not contain the prefix,
37281 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
37282 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
37283 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
37284 wherever @value{GDBN} is installed.
37287 If the configured location of the system-wide init file (as given by the
37288 @option{--with-system-gdbinit} option at configure time) is in the
37289 data-directory (as specified by @option{--with-gdb-datadir} at configure
37290 time) or in one of its subdirectories, then @value{GDBN} will look for the
37291 system-wide init file in the directory specified by the
37292 @option{--data-directory} command-line option.
37293 Note that the system-wide init file is only read once, during @value{GDBN}
37294 initialization. If the data-directory is changed after @value{GDBN} has
37295 started with the @code{set data-directory} command, the file will not be
37299 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
37302 @node System-wide Configuration Scripts
37303 @subsection Installed System-wide Configuration Scripts
37304 @cindex system-wide configuration scripts
37306 The @file{system-gdbinit} directory, located inside the data-directory
37307 (as specified by @option{--with-gdb-datadir} at configure time) contains
37308 a number of scripts which can be used as system-wide init files. To
37309 automatically source those scripts at startup, @value{GDBN} should be
37310 configured with @option{--with-system-gdbinit}. Otherwise, any user
37311 should be able to source them by hand as needed.
37313 The following scripts are currently available:
37316 @item @file{elinos.py}
37318 @cindex ELinOS system-wide configuration script
37319 This script is useful when debugging a program on an ELinOS target.
37320 It takes advantage of the environment variables defined in a standard
37321 ELinOS environment in order to determine the location of the system
37322 shared libraries, and then sets the @samp{solib-absolute-prefix}
37323 and @samp{solib-search-path} variables appropriately.
37325 @item @file{wrs-linux.py}
37326 @pindex wrs-linux.py
37327 @cindex Wind River Linux system-wide configuration script
37328 This script is useful when debugging a program on a target running
37329 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
37330 the host-side sysroot used by the target system.
37334 @node Maintenance Commands
37335 @appendix Maintenance Commands
37336 @cindex maintenance commands
37337 @cindex internal commands
37339 In addition to commands intended for @value{GDBN} users, @value{GDBN}
37340 includes a number of commands intended for @value{GDBN} developers,
37341 that are not documented elsewhere in this manual. These commands are
37342 provided here for reference. (For commands that turn on debugging
37343 messages, see @ref{Debugging Output}.)
37346 @kindex maint agent
37347 @kindex maint agent-eval
37348 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
37349 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
37350 Translate the given @var{expression} into remote agent bytecodes.
37351 This command is useful for debugging the Agent Expression mechanism
37352 (@pxref{Agent Expressions}). The @samp{agent} version produces an
37353 expression useful for data collection, such as by tracepoints, while
37354 @samp{maint agent-eval} produces an expression that evaluates directly
37355 to a result. For instance, a collection expression for @code{globa +
37356 globb} will include bytecodes to record four bytes of memory at each
37357 of the addresses of @code{globa} and @code{globb}, while discarding
37358 the result of the addition, while an evaluation expression will do the
37359 addition and return the sum.
37360 If @code{-at} is given, generate remote agent bytecode for @var{location}.
37361 If not, generate remote agent bytecode for current frame PC address.
37363 @kindex maint agent-printf
37364 @item maint agent-printf @var{format},@var{expr},...
37365 Translate the given format string and list of argument expressions
37366 into remote agent bytecodes and display them as a disassembled list.
37367 This command is useful for debugging the agent version of dynamic
37368 printf (@pxref{Dynamic Printf}).
37370 @kindex maint info breakpoints
37371 @item @anchor{maint info breakpoints}maint info breakpoints
37372 Using the same format as @samp{info breakpoints}, display both the
37373 breakpoints you've set explicitly, and those @value{GDBN} is using for
37374 internal purposes. Internal breakpoints are shown with negative
37375 breakpoint numbers. The type column identifies what kind of breakpoint
37380 Normal, explicitly set breakpoint.
37383 Normal, explicitly set watchpoint.
37386 Internal breakpoint, used to handle correctly stepping through
37387 @code{longjmp} calls.
37389 @item longjmp resume
37390 Internal breakpoint at the target of a @code{longjmp}.
37393 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
37396 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
37399 Shared library events.
37403 @kindex maint info bfds
37404 @item maint info bfds
37405 This prints information about each @code{bfd} object that is known to
37406 @value{GDBN}. @xref{Top, , BFD, bfd, The Binary File Descriptor Library}.
37408 @kindex set displaced-stepping
37409 @kindex show displaced-stepping
37410 @cindex displaced stepping support
37411 @cindex out-of-line single-stepping
37412 @item set displaced-stepping
37413 @itemx show displaced-stepping
37414 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
37415 if the target supports it. Displaced stepping is a way to single-step
37416 over breakpoints without removing them from the inferior, by executing
37417 an out-of-line copy of the instruction that was originally at the
37418 breakpoint location. It is also known as out-of-line single-stepping.
37421 @item set displaced-stepping on
37422 If the target architecture supports it, @value{GDBN} will use
37423 displaced stepping to step over breakpoints.
37425 @item set displaced-stepping off
37426 @value{GDBN} will not use displaced stepping to step over breakpoints,
37427 even if such is supported by the target architecture.
37429 @cindex non-stop mode, and @samp{set displaced-stepping}
37430 @item set displaced-stepping auto
37431 This is the default mode. @value{GDBN} will use displaced stepping
37432 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
37433 architecture supports displaced stepping.
37436 @kindex maint check-psymtabs
37437 @item maint check-psymtabs
37438 Check the consistency of currently expanded psymtabs versus symtabs.
37439 Use this to check, for example, whether a symbol is in one but not the other.
37441 @kindex maint check-symtabs
37442 @item maint check-symtabs
37443 Check the consistency of currently expanded symtabs.
37445 @kindex maint expand-symtabs
37446 @item maint expand-symtabs [@var{regexp}]
37447 Expand symbol tables.
37448 If @var{regexp} is specified, only expand symbol tables for file
37449 names matching @var{regexp}.
37451 @kindex maint cplus first_component
37452 @item maint cplus first_component @var{name}
37453 Print the first C@t{++} class/namespace component of @var{name}.
37455 @kindex maint cplus namespace
37456 @item maint cplus namespace
37457 Print the list of possible C@t{++} namespaces.
37459 @kindex maint demangle
37460 @item maint demangle @var{name}
37461 Demangle a C@t{++} or Objective-C mangled @var{name}.
37463 @kindex maint deprecate
37464 @kindex maint undeprecate
37465 @cindex deprecated commands
37466 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
37467 @itemx maint undeprecate @var{command}
37468 Deprecate or undeprecate the named @var{command}. Deprecated commands
37469 cause @value{GDBN} to issue a warning when you use them. The optional
37470 argument @var{replacement} says which newer command should be used in
37471 favor of the deprecated one; if it is given, @value{GDBN} will mention
37472 the replacement as part of the warning.
37474 @kindex maint dump-me
37475 @item maint dump-me
37476 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
37477 Cause a fatal signal in the debugger and force it to dump its core.
37478 This is supported only on systems which support aborting a program
37479 with the @code{SIGQUIT} signal.
37481 @kindex maint internal-error
37482 @kindex maint internal-warning
37483 @item maint internal-error @r{[}@var{message-text}@r{]}
37484 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
37485 Cause @value{GDBN} to call the internal function @code{internal_error}
37486 or @code{internal_warning} and hence behave as though an internal error
37487 or internal warning has been detected. In addition to reporting the
37488 internal problem, these functions give the user the opportunity to
37489 either quit @value{GDBN} or create a core file of the current
37490 @value{GDBN} session.
37492 These commands take an optional parameter @var{message-text} that is
37493 used as the text of the error or warning message.
37495 Here's an example of using @code{internal-error}:
37498 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
37499 @dots{}/maint.c:121: internal-error: testing, 1, 2
37500 A problem internal to GDB has been detected. Further
37501 debugging may prove unreliable.
37502 Quit this debugging session? (y or n) @kbd{n}
37503 Create a core file? (y or n) @kbd{n}
37507 @cindex @value{GDBN} internal error
37508 @cindex internal errors, control of @value{GDBN} behavior
37510 @kindex maint set internal-error
37511 @kindex maint show internal-error
37512 @kindex maint set internal-warning
37513 @kindex maint show internal-warning
37514 @item maint set internal-error @var{action} [ask|yes|no]
37515 @itemx maint show internal-error @var{action}
37516 @itemx maint set internal-warning @var{action} [ask|yes|no]
37517 @itemx maint show internal-warning @var{action}
37518 When @value{GDBN} reports an internal problem (error or warning) it
37519 gives the user the opportunity to both quit @value{GDBN} and create a
37520 core file of the current @value{GDBN} session. These commands let you
37521 override the default behaviour for each particular @var{action},
37522 described in the table below.
37526 You can specify that @value{GDBN} should always (yes) or never (no)
37527 quit. The default is to ask the user what to do.
37530 You can specify that @value{GDBN} should always (yes) or never (no)
37531 create a core file. The default is to ask the user what to do.
37534 @kindex maint packet
37535 @item maint packet @var{text}
37536 If @value{GDBN} is talking to an inferior via the serial protocol,
37537 then this command sends the string @var{text} to the inferior, and
37538 displays the response packet. @value{GDBN} supplies the initial
37539 @samp{$} character, the terminating @samp{#} character, and the
37542 @kindex maint print architecture
37543 @item maint print architecture @r{[}@var{file}@r{]}
37544 Print the entire architecture configuration. The optional argument
37545 @var{file} names the file where the output goes.
37547 @kindex maint print c-tdesc
37548 @item maint print c-tdesc
37549 Print the current target description (@pxref{Target Descriptions}) as
37550 a C source file. The created source file can be used in @value{GDBN}
37551 when an XML parser is not available to parse the description.
37553 @kindex maint print dummy-frames
37554 @item maint print dummy-frames
37555 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
37558 (@value{GDBP}) @kbd{b add}
37560 (@value{GDBP}) @kbd{print add(2,3)}
37561 Breakpoint 2, add (a=2, b=3) at @dots{}
37563 The program being debugged stopped while in a function called from GDB.
37565 (@value{GDBP}) @kbd{maint print dummy-frames}
37566 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
37567 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
37568 call_lo=0x01014000 call_hi=0x01014001
37572 Takes an optional file parameter.
37574 @kindex maint print registers
37575 @kindex maint print raw-registers
37576 @kindex maint print cooked-registers
37577 @kindex maint print register-groups
37578 @kindex maint print remote-registers
37579 @item maint print registers @r{[}@var{file}@r{]}
37580 @itemx maint print raw-registers @r{[}@var{file}@r{]}
37581 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
37582 @itemx maint print register-groups @r{[}@var{file}@r{]}
37583 @itemx maint print remote-registers @r{[}@var{file}@r{]}
37584 Print @value{GDBN}'s internal register data structures.
37586 The command @code{maint print raw-registers} includes the contents of
37587 the raw register cache; the command @code{maint print
37588 cooked-registers} includes the (cooked) value of all registers,
37589 including registers which aren't available on the target nor visible
37590 to user; the command @code{maint print register-groups} includes the
37591 groups that each register is a member of; and the command @code{maint
37592 print remote-registers} includes the remote target's register numbers
37593 and offsets in the `G' packets.
37595 These commands take an optional parameter, a file name to which to
37596 write the information.
37598 @kindex maint print reggroups
37599 @item maint print reggroups @r{[}@var{file}@r{]}
37600 Print @value{GDBN}'s internal register group data structures. The
37601 optional argument @var{file} tells to what file to write the
37604 The register groups info looks like this:
37607 (@value{GDBP}) @kbd{maint print reggroups}
37620 This command forces @value{GDBN} to flush its internal register cache.
37622 @kindex maint print objfiles
37623 @cindex info for known object files
37624 @item maint print objfiles @r{[}@var{regexp}@r{]}
37625 Print a dump of all known object files.
37626 If @var{regexp} is specified, only print object files whose names
37627 match @var{regexp}. For each object file, this command prints its name,
37628 address in memory, and all of its psymtabs and symtabs.
37630 @kindex maint print section-scripts
37631 @cindex info for known .debug_gdb_scripts-loaded scripts
37632 @item maint print section-scripts [@var{regexp}]
37633 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
37634 If @var{regexp} is specified, only print scripts loaded by object files
37635 matching @var{regexp}.
37636 For each script, this command prints its name as specified in the objfile,
37637 and the full path if known.
37638 @xref{dotdebug_gdb_scripts section}.
37640 @kindex maint print statistics
37641 @cindex bcache statistics
37642 @item maint print statistics
37643 This command prints, for each object file in the program, various data
37644 about that object file followed by the byte cache (@dfn{bcache})
37645 statistics for the object file. The objfile data includes the number
37646 of minimal, partial, full, and stabs symbols, the number of types
37647 defined by the objfile, the number of as yet unexpanded psym tables,
37648 the number of line tables and string tables, and the amount of memory
37649 used by the various tables. The bcache statistics include the counts,
37650 sizes, and counts of duplicates of all and unique objects, max,
37651 average, and median entry size, total memory used and its overhead and
37652 savings, and various measures of the hash table size and chain
37655 @kindex maint print target-stack
37656 @cindex target stack description
37657 @item maint print target-stack
37658 A @dfn{target} is an interface between the debugger and a particular
37659 kind of file or process. Targets can be stacked in @dfn{strata},
37660 so that more than one target can potentially respond to a request.
37661 In particular, memory accesses will walk down the stack of targets
37662 until they find a target that is interested in handling that particular
37665 This command prints a short description of each layer that was pushed on
37666 the @dfn{target stack}, starting from the top layer down to the bottom one.
37668 @kindex maint print type
37669 @cindex type chain of a data type
37670 @item maint print type @var{expr}
37671 Print the type chain for a type specified by @var{expr}. The argument
37672 can be either a type name or a symbol. If it is a symbol, the type of
37673 that symbol is described. The type chain produced by this command is
37674 a recursive definition of the data type as stored in @value{GDBN}'s
37675 data structures, including its flags and contained types.
37677 @kindex maint set dwarf2 always-disassemble
37678 @kindex maint show dwarf2 always-disassemble
37679 @item maint set dwarf2 always-disassemble
37680 @item maint show dwarf2 always-disassemble
37681 Control the behavior of @code{info address} when using DWARF debugging
37684 The default is @code{off}, which means that @value{GDBN} should try to
37685 describe a variable's location in an easily readable format. When
37686 @code{on}, @value{GDBN} will instead display the DWARF location
37687 expression in an assembly-like format. Note that some locations are
37688 too complex for @value{GDBN} to describe simply; in this case you will
37689 always see the disassembly form.
37691 Here is an example of the resulting disassembly:
37694 (gdb) info addr argc
37695 Symbol "argc" is a complex DWARF expression:
37699 For more information on these expressions, see
37700 @uref{http://www.dwarfstd.org/, the DWARF standard}.
37702 @kindex maint set dwarf2 max-cache-age
37703 @kindex maint show dwarf2 max-cache-age
37704 @item maint set dwarf2 max-cache-age
37705 @itemx maint show dwarf2 max-cache-age
37706 Control the DWARF 2 compilation unit cache.
37708 @cindex DWARF 2 compilation units cache
37709 In object files with inter-compilation-unit references, such as those
37710 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
37711 reader needs to frequently refer to previously read compilation units.
37712 This setting controls how long a compilation unit will remain in the
37713 cache if it is not referenced. A higher limit means that cached
37714 compilation units will be stored in memory longer, and more total
37715 memory will be used. Setting it to zero disables caching, which will
37716 slow down @value{GDBN} startup, but reduce memory consumption.
37718 @kindex maint set profile
37719 @kindex maint show profile
37720 @cindex profiling GDB
37721 @item maint set profile
37722 @itemx maint show profile
37723 Control profiling of @value{GDBN}.
37725 Profiling will be disabled until you use the @samp{maint set profile}
37726 command to enable it. When you enable profiling, the system will begin
37727 collecting timing and execution count data; when you disable profiling or
37728 exit @value{GDBN}, the results will be written to a log file. Remember that
37729 if you use profiling, @value{GDBN} will overwrite the profiling log file
37730 (often called @file{gmon.out}). If you have a record of important profiling
37731 data in a @file{gmon.out} file, be sure to move it to a safe location.
37733 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
37734 compiled with the @samp{-pg} compiler option.
37736 @kindex maint set show-debug-regs
37737 @kindex maint show show-debug-regs
37738 @cindex hardware debug registers
37739 @item maint set show-debug-regs
37740 @itemx maint show show-debug-regs
37741 Control whether to show variables that mirror the hardware debug
37742 registers. Use @code{on} to enable, @code{off} to disable. If
37743 enabled, the debug registers values are shown when @value{GDBN} inserts or
37744 removes a hardware breakpoint or watchpoint, and when the inferior
37745 triggers a hardware-assisted breakpoint or watchpoint.
37747 @kindex maint set show-all-tib
37748 @kindex maint show show-all-tib
37749 @item maint set show-all-tib
37750 @itemx maint show show-all-tib
37751 Control whether to show all non zero areas within a 1k block starting
37752 at thread local base, when using the @samp{info w32 thread-information-block}
37755 @kindex maint set per-command
37756 @kindex maint show per-command
37757 @item maint set per-command
37758 @itemx maint show per-command
37759 @cindex resources used by commands
37761 @value{GDBN} can display the resources used by each command.
37762 This is useful in debugging performance problems.
37765 @item maint set per-command space [on|off]
37766 @itemx maint show per-command space
37767 Enable or disable the printing of the memory used by GDB for each command.
37768 If enabled, @value{GDBN} will display how much memory each command
37769 took, following the command's own output.
37770 This can also be requested by invoking @value{GDBN} with the
37771 @option{--statistics} command-line switch (@pxref{Mode Options}).
37773 @item maint set per-command time [on|off]
37774 @itemx maint show per-command time
37775 Enable or disable the printing of the execution time of @value{GDBN}
37777 If enabled, @value{GDBN} will display how much time it
37778 took to execute each command, following the command's own output.
37779 Both CPU time and wallclock time are printed.
37780 Printing both is useful when trying to determine whether the cost is
37781 CPU or, e.g., disk/network latency.
37782 Note that the CPU time printed is for @value{GDBN} only, it does not include
37783 the execution time of the inferior because there's no mechanism currently
37784 to compute how much time was spent by @value{GDBN} and how much time was
37785 spent by the program been debugged.
37786 This can also be requested by invoking @value{GDBN} with the
37787 @option{--statistics} command-line switch (@pxref{Mode Options}).
37789 @item maint set per-command symtab [on|off]
37790 @itemx maint show per-command symtab
37791 Enable or disable the printing of basic symbol table statistics
37793 If enabled, @value{GDBN} will display the following information:
37797 number of symbol tables
37799 number of primary symbol tables
37801 number of blocks in the blockvector
37805 @kindex maint space
37806 @cindex memory used by commands
37807 @item maint space @var{value}
37808 An alias for @code{maint set per-command space}.
37809 A non-zero value enables it, zero disables it.
37812 @cindex time of command execution
37813 @item maint time @var{value}
37814 An alias for @code{maint set per-command time}.
37815 A non-zero value enables it, zero disables it.
37817 @kindex maint translate-address
37818 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
37819 Find the symbol stored at the location specified by the address
37820 @var{addr} and an optional section name @var{section}. If found,
37821 @value{GDBN} prints the name of the closest symbol and an offset from
37822 the symbol's location to the specified address. This is similar to
37823 the @code{info address} command (@pxref{Symbols}), except that this
37824 command also allows to find symbols in other sections.
37826 If section was not specified, the section in which the symbol was found
37827 is also printed. For dynamically linked executables, the name of
37828 executable or shared library containing the symbol is printed as well.
37832 The following command is useful for non-interactive invocations of
37833 @value{GDBN}, such as in the test suite.
37836 @item set watchdog @var{nsec}
37837 @kindex set watchdog
37838 @cindex watchdog timer
37839 @cindex timeout for commands
37840 Set the maximum number of seconds @value{GDBN} will wait for the
37841 target operation to finish. If this time expires, @value{GDBN}
37842 reports and error and the command is aborted.
37844 @item show watchdog
37845 Show the current setting of the target wait timeout.
37848 @node Remote Protocol
37849 @appendix @value{GDBN} Remote Serial Protocol
37854 * Stop Reply Packets::
37855 * General Query Packets::
37856 * Architecture-Specific Protocol Details::
37857 * Tracepoint Packets::
37858 * Host I/O Packets::
37860 * Notification Packets::
37861 * Remote Non-Stop::
37862 * Packet Acknowledgment::
37864 * File-I/O Remote Protocol Extension::
37865 * Library List Format::
37866 * Library List Format for SVR4 Targets::
37867 * Memory Map Format::
37868 * Thread List Format::
37869 * Traceframe Info Format::
37870 * Branch Trace Format::
37876 There may be occasions when you need to know something about the
37877 protocol---for example, if there is only one serial port to your target
37878 machine, you might want your program to do something special if it
37879 recognizes a packet meant for @value{GDBN}.
37881 In the examples below, @samp{->} and @samp{<-} are used to indicate
37882 transmitted and received data, respectively.
37884 @cindex protocol, @value{GDBN} remote serial
37885 @cindex serial protocol, @value{GDBN} remote
37886 @cindex remote serial protocol
37887 All @value{GDBN} commands and responses (other than acknowledgments
37888 and notifications, see @ref{Notification Packets}) are sent as a
37889 @var{packet}. A @var{packet} is introduced with the character
37890 @samp{$}, the actual @var{packet-data}, and the terminating character
37891 @samp{#} followed by a two-digit @var{checksum}:
37894 @code{$}@var{packet-data}@code{#}@var{checksum}
37898 @cindex checksum, for @value{GDBN} remote
37900 The two-digit @var{checksum} is computed as the modulo 256 sum of all
37901 characters between the leading @samp{$} and the trailing @samp{#} (an
37902 eight bit unsigned checksum).
37904 Implementors should note that prior to @value{GDBN} 5.0 the protocol
37905 specification also included an optional two-digit @var{sequence-id}:
37908 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
37911 @cindex sequence-id, for @value{GDBN} remote
37913 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
37914 has never output @var{sequence-id}s. Stubs that handle packets added
37915 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
37917 When either the host or the target machine receives a packet, the first
37918 response expected is an acknowledgment: either @samp{+} (to indicate
37919 the package was received correctly) or @samp{-} (to request
37923 -> @code{$}@var{packet-data}@code{#}@var{checksum}
37928 The @samp{+}/@samp{-} acknowledgments can be disabled
37929 once a connection is established.
37930 @xref{Packet Acknowledgment}, for details.
37932 The host (@value{GDBN}) sends @var{command}s, and the target (the
37933 debugging stub incorporated in your program) sends a @var{response}. In
37934 the case of step and continue @var{command}s, the response is only sent
37935 when the operation has completed, and the target has again stopped all
37936 threads in all attached processes. This is the default all-stop mode
37937 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
37938 execution mode; see @ref{Remote Non-Stop}, for details.
37940 @var{packet-data} consists of a sequence of characters with the
37941 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
37944 @cindex remote protocol, field separator
37945 Fields within the packet should be separated using @samp{,} @samp{;} or
37946 @samp{:}. Except where otherwise noted all numbers are represented in
37947 @sc{hex} with leading zeros suppressed.
37949 Implementors should note that prior to @value{GDBN} 5.0, the character
37950 @samp{:} could not appear as the third character in a packet (as it
37951 would potentially conflict with the @var{sequence-id}).
37953 @cindex remote protocol, binary data
37954 @anchor{Binary Data}
37955 Binary data in most packets is encoded either as two hexadecimal
37956 digits per byte of binary data. This allowed the traditional remote
37957 protocol to work over connections which were only seven-bit clean.
37958 Some packets designed more recently assume an eight-bit clean
37959 connection, and use a more efficient encoding to send and receive
37962 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
37963 as an escape character. Any escaped byte is transmitted as the escape
37964 character followed by the original character XORed with @code{0x20}.
37965 For example, the byte @code{0x7d} would be transmitted as the two
37966 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
37967 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
37968 @samp{@}}) must always be escaped. Responses sent by the stub
37969 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
37970 is not interpreted as the start of a run-length encoded sequence
37973 Response @var{data} can be run-length encoded to save space.
37974 Run-length encoding replaces runs of identical characters with one
37975 instance of the repeated character, followed by a @samp{*} and a
37976 repeat count. The repeat count is itself sent encoded, to avoid
37977 binary characters in @var{data}: a value of @var{n} is sent as
37978 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
37979 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
37980 code 32) for a repeat count of 3. (This is because run-length
37981 encoding starts to win for counts 3 or more.) Thus, for example,
37982 @samp{0* } is a run-length encoding of ``0000'': the space character
37983 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
37986 The printable characters @samp{#} and @samp{$} or with a numeric value
37987 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
37988 seven repeats (@samp{$}) can be expanded using a repeat count of only
37989 five (@samp{"}). For example, @samp{00000000} can be encoded as
37992 The error response returned for some packets includes a two character
37993 error number. That number is not well defined.
37995 @cindex empty response, for unsupported packets
37996 For any @var{command} not supported by the stub, an empty response
37997 (@samp{$#00}) should be returned. That way it is possible to extend the
37998 protocol. A newer @value{GDBN} can tell if a packet is supported based
38001 At a minimum, a stub is required to support the @samp{g} and @samp{G}
38002 commands for register access, and the @samp{m} and @samp{M} commands
38003 for memory access. Stubs that only control single-threaded targets
38004 can implement run control with the @samp{c} (continue), and @samp{s}
38005 (step) commands. Stubs that support multi-threading targets should
38006 support the @samp{vCont} command. All other commands are optional.
38011 The following table provides a complete list of all currently defined
38012 @var{command}s and their corresponding response @var{data}.
38013 @xref{File-I/O Remote Protocol Extension}, for details about the File
38014 I/O extension of the remote protocol.
38016 Each packet's description has a template showing the packet's overall
38017 syntax, followed by an explanation of the packet's meaning. We
38018 include spaces in some of the templates for clarity; these are not
38019 part of the packet's syntax. No @value{GDBN} packet uses spaces to
38020 separate its components. For example, a template like @samp{foo
38021 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
38022 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
38023 @var{baz}. @value{GDBN} does not transmit a space character between the
38024 @samp{foo} and the @var{bar}, or between the @var{bar} and the
38027 @cindex @var{thread-id}, in remote protocol
38028 @anchor{thread-id syntax}
38029 Several packets and replies include a @var{thread-id} field to identify
38030 a thread. Normally these are positive numbers with a target-specific
38031 interpretation, formatted as big-endian hex strings. A @var{thread-id}
38032 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
38035 In addition, the remote protocol supports a multiprocess feature in
38036 which the @var{thread-id} syntax is extended to optionally include both
38037 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
38038 The @var{pid} (process) and @var{tid} (thread) components each have the
38039 format described above: a positive number with target-specific
38040 interpretation formatted as a big-endian hex string, literal @samp{-1}
38041 to indicate all processes or threads (respectively), or @samp{0} to
38042 indicate an arbitrary process or thread. Specifying just a process, as
38043 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
38044 error to specify all processes but a specific thread, such as
38045 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
38046 for those packets and replies explicitly documented to include a process
38047 ID, rather than a @var{thread-id}.
38049 The multiprocess @var{thread-id} syntax extensions are only used if both
38050 @value{GDBN} and the stub report support for the @samp{multiprocess}
38051 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
38054 Note that all packet forms beginning with an upper- or lower-case
38055 letter, other than those described here, are reserved for future use.
38057 Here are the packet descriptions.
38062 @cindex @samp{!} packet
38063 @anchor{extended mode}
38064 Enable extended mode. In extended mode, the remote server is made
38065 persistent. The @samp{R} packet is used to restart the program being
38071 The remote target both supports and has enabled extended mode.
38075 @cindex @samp{?} packet
38076 Indicate the reason the target halted. The reply is the same as for
38077 step and continue. This packet has a special interpretation when the
38078 target is in non-stop mode; see @ref{Remote Non-Stop}.
38081 @xref{Stop Reply Packets}, for the reply specifications.
38083 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
38084 @cindex @samp{A} packet
38085 Initialized @code{argv[]} array passed into program. @var{arglen}
38086 specifies the number of bytes in the hex encoded byte stream
38087 @var{arg}. See @code{gdbserver} for more details.
38092 The arguments were set.
38098 @cindex @samp{b} packet
38099 (Don't use this packet; its behavior is not well-defined.)
38100 Change the serial line speed to @var{baud}.
38102 JTC: @emph{When does the transport layer state change? When it's
38103 received, or after the ACK is transmitted. In either case, there are
38104 problems if the command or the acknowledgment packet is dropped.}
38106 Stan: @emph{If people really wanted to add something like this, and get
38107 it working for the first time, they ought to modify ser-unix.c to send
38108 some kind of out-of-band message to a specially-setup stub and have the
38109 switch happen "in between" packets, so that from remote protocol's point
38110 of view, nothing actually happened.}
38112 @item B @var{addr},@var{mode}
38113 @cindex @samp{B} packet
38114 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
38115 breakpoint at @var{addr}.
38117 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
38118 (@pxref{insert breakpoint or watchpoint packet}).
38120 @cindex @samp{bc} packet
38123 Backward continue. Execute the target system in reverse. No parameter.
38124 @xref{Reverse Execution}, for more information.
38127 @xref{Stop Reply Packets}, for the reply specifications.
38129 @cindex @samp{bs} packet
38132 Backward single step. Execute one instruction in reverse. No parameter.
38133 @xref{Reverse Execution}, for more information.
38136 @xref{Stop Reply Packets}, for the reply specifications.
38138 @item c @r{[}@var{addr}@r{]}
38139 @cindex @samp{c} packet
38140 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
38141 resume at current address.
38143 This packet is deprecated for multi-threading support. @xref{vCont
38147 @xref{Stop Reply Packets}, for the reply specifications.
38149 @item C @var{sig}@r{[};@var{addr}@r{]}
38150 @cindex @samp{C} packet
38151 Continue with signal @var{sig} (hex signal number). If
38152 @samp{;@var{addr}} is omitted, resume at same address.
38154 This packet is deprecated for multi-threading support. @xref{vCont
38158 @xref{Stop Reply Packets}, for the reply specifications.
38161 @cindex @samp{d} packet
38164 Don't use this packet; instead, define a general set packet
38165 (@pxref{General Query Packets}).
38169 @cindex @samp{D} packet
38170 The first form of the packet is used to detach @value{GDBN} from the
38171 remote system. It is sent to the remote target
38172 before @value{GDBN} disconnects via the @code{detach} command.
38174 The second form, including a process ID, is used when multiprocess
38175 protocol extensions are enabled (@pxref{multiprocess extensions}), to
38176 detach only a specific process. The @var{pid} is specified as a
38177 big-endian hex string.
38187 @item F @var{RC},@var{EE},@var{CF};@var{XX}
38188 @cindex @samp{F} packet
38189 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
38190 This is part of the File-I/O protocol extension. @xref{File-I/O
38191 Remote Protocol Extension}, for the specification.
38194 @anchor{read registers packet}
38195 @cindex @samp{g} packet
38196 Read general registers.
38200 @item @var{XX@dots{}}
38201 Each byte of register data is described by two hex digits. The bytes
38202 with the register are transmitted in target byte order. The size of
38203 each register and their position within the @samp{g} packet are
38204 determined by the @value{GDBN} internal gdbarch functions
38205 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
38206 specification of several standard @samp{g} packets is specified below.
38208 When reading registers from a trace frame (@pxref{Analyze Collected
38209 Data,,Using the Collected Data}), the stub may also return a string of
38210 literal @samp{x}'s in place of the register data digits, to indicate
38211 that the corresponding register has not been collected, thus its value
38212 is unavailable. For example, for an architecture with 4 registers of
38213 4 bytes each, the following reply indicates to @value{GDBN} that
38214 registers 0 and 2 have not been collected, while registers 1 and 3
38215 have been collected, and both have zero value:
38219 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
38226 @item G @var{XX@dots{}}
38227 @cindex @samp{G} packet
38228 Write general registers. @xref{read registers packet}, for a
38229 description of the @var{XX@dots{}} data.
38239 @item H @var{op} @var{thread-id}
38240 @cindex @samp{H} packet
38241 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
38242 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
38243 it should be @samp{c} for step and continue operations (note that this
38244 is deprecated, supporting the @samp{vCont} command is a better
38245 option), @samp{g} for other operations. The thread designator
38246 @var{thread-id} has the format and interpretation described in
38247 @ref{thread-id syntax}.
38258 @c 'H': How restrictive (or permissive) is the thread model. If a
38259 @c thread is selected and stopped, are other threads allowed
38260 @c to continue to execute? As I mentioned above, I think the
38261 @c semantics of each command when a thread is selected must be
38262 @c described. For example:
38264 @c 'g': If the stub supports threads and a specific thread is
38265 @c selected, returns the register block from that thread;
38266 @c otherwise returns current registers.
38268 @c 'G' If the stub supports threads and a specific thread is
38269 @c selected, sets the registers of the register block of
38270 @c that thread; otherwise sets current registers.
38272 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
38273 @anchor{cycle step packet}
38274 @cindex @samp{i} packet
38275 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
38276 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
38277 step starting at that address.
38280 @cindex @samp{I} packet
38281 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
38285 @cindex @samp{k} packet
38288 FIXME: @emph{There is no description of how to operate when a specific
38289 thread context has been selected (i.e.@: does 'k' kill only that
38292 @item m @var{addr},@var{length}
38293 @cindex @samp{m} packet
38294 Read @var{length} bytes of memory starting at address @var{addr}.
38295 Note that @var{addr} may not be aligned to any particular boundary.
38297 The stub need not use any particular size or alignment when gathering
38298 data from memory for the response; even if @var{addr} is word-aligned
38299 and @var{length} is a multiple of the word size, the stub is free to
38300 use byte accesses, or not. For this reason, this packet may not be
38301 suitable for accessing memory-mapped I/O devices.
38302 @cindex alignment of remote memory accesses
38303 @cindex size of remote memory accesses
38304 @cindex memory, alignment and size of remote accesses
38308 @item @var{XX@dots{}}
38309 Memory contents; each byte is transmitted as a two-digit hexadecimal
38310 number. The reply may contain fewer bytes than requested if the
38311 server was able to read only part of the region of memory.
38316 @item M @var{addr},@var{length}:@var{XX@dots{}}
38317 @cindex @samp{M} packet
38318 Write @var{length} bytes of memory starting at address @var{addr}.
38319 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
38320 hexadecimal number.
38327 for an error (this includes the case where only part of the data was
38332 @cindex @samp{p} packet
38333 Read the value of register @var{n}; @var{n} is in hex.
38334 @xref{read registers packet}, for a description of how the returned
38335 register value is encoded.
38339 @item @var{XX@dots{}}
38340 the register's value
38344 Indicating an unrecognized @var{query}.
38347 @item P @var{n@dots{}}=@var{r@dots{}}
38348 @anchor{write register packet}
38349 @cindex @samp{P} packet
38350 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
38351 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
38352 digits for each byte in the register (target byte order).
38362 @item q @var{name} @var{params}@dots{}
38363 @itemx Q @var{name} @var{params}@dots{}
38364 @cindex @samp{q} packet
38365 @cindex @samp{Q} packet
38366 General query (@samp{q}) and set (@samp{Q}). These packets are
38367 described fully in @ref{General Query Packets}.
38370 @cindex @samp{r} packet
38371 Reset the entire system.
38373 Don't use this packet; use the @samp{R} packet instead.
38376 @cindex @samp{R} packet
38377 Restart the program being debugged. @var{XX}, while needed, is ignored.
38378 This packet is only available in extended mode (@pxref{extended mode}).
38380 The @samp{R} packet has no reply.
38382 @item s @r{[}@var{addr}@r{]}
38383 @cindex @samp{s} packet
38384 Single step. @var{addr} is the address at which to resume. If
38385 @var{addr} is omitted, resume at same address.
38387 This packet is deprecated for multi-threading support. @xref{vCont
38391 @xref{Stop Reply Packets}, for the reply specifications.
38393 @item S @var{sig}@r{[};@var{addr}@r{]}
38394 @anchor{step with signal packet}
38395 @cindex @samp{S} packet
38396 Step with signal. This is analogous to the @samp{C} packet, but
38397 requests a single-step, rather than a normal resumption of execution.
38399 This packet is deprecated for multi-threading support. @xref{vCont
38403 @xref{Stop Reply Packets}, for the reply specifications.
38405 @item t @var{addr}:@var{PP},@var{MM}
38406 @cindex @samp{t} packet
38407 Search backwards starting at address @var{addr} for a match with pattern
38408 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
38409 @var{addr} must be at least 3 digits.
38411 @item T @var{thread-id}
38412 @cindex @samp{T} packet
38413 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
38418 thread is still alive
38424 Packets starting with @samp{v} are identified by a multi-letter name,
38425 up to the first @samp{;} or @samp{?} (or the end of the packet).
38427 @item vAttach;@var{pid}
38428 @cindex @samp{vAttach} packet
38429 Attach to a new process with the specified process ID @var{pid}.
38430 The process ID is a
38431 hexadecimal integer identifying the process. In all-stop mode, all
38432 threads in the attached process are stopped; in non-stop mode, it may be
38433 attached without being stopped if that is supported by the target.
38435 @c In non-stop mode, on a successful vAttach, the stub should set the
38436 @c current thread to a thread of the newly-attached process. After
38437 @c attaching, GDB queries for the attached process's thread ID with qC.
38438 @c Also note that, from a user perspective, whether or not the
38439 @c target is stopped on attach in non-stop mode depends on whether you
38440 @c use the foreground or background version of the attach command, not
38441 @c on what vAttach does; GDB does the right thing with respect to either
38442 @c stopping or restarting threads.
38444 This packet is only available in extended mode (@pxref{extended mode}).
38450 @item @r{Any stop packet}
38451 for success in all-stop mode (@pxref{Stop Reply Packets})
38453 for success in non-stop mode (@pxref{Remote Non-Stop})
38456 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
38457 @cindex @samp{vCont} packet
38458 @anchor{vCont packet}
38459 Resume the inferior, specifying different actions for each thread.
38460 If an action is specified with no @var{thread-id}, then it is applied to any
38461 threads that don't have a specific action specified; if no default action is
38462 specified then other threads should remain stopped in all-stop mode and
38463 in their current state in non-stop mode.
38464 Specifying multiple
38465 default actions is an error; specifying no actions is also an error.
38466 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
38468 Currently supported actions are:
38474 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
38478 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
38481 @item r @var{start},@var{end}
38482 Step once, and then keep stepping as long as the thread stops at
38483 addresses between @var{start} (inclusive) and @var{end} (exclusive).
38484 The remote stub reports a stop reply when either the thread goes out
38485 of the range or is stopped due to an unrelated reason, such as hitting
38486 a breakpoint. @xref{range stepping}.
38488 If the range is empty (@var{start} == @var{end}), then the action
38489 becomes equivalent to the @samp{s} action. In other words,
38490 single-step once, and report the stop (even if the stepped instruction
38491 jumps to @var{start}).
38493 (A stop reply may be sent at any point even if the PC is still within
38494 the stepping range; for example, it is valid to implement this packet
38495 in a degenerate way as a single instruction step operation.)
38499 The optional argument @var{addr} normally associated with the
38500 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
38501 not supported in @samp{vCont}.
38503 The @samp{t} action is only relevant in non-stop mode
38504 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
38505 A stop reply should be generated for any affected thread not already stopped.
38506 When a thread is stopped by means of a @samp{t} action,
38507 the corresponding stop reply should indicate that the thread has stopped with
38508 signal @samp{0}, regardless of whether the target uses some other signal
38509 as an implementation detail.
38511 The stub must support @samp{vCont} if it reports support for
38512 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
38513 this case @samp{vCont} actions can be specified to apply to all threads
38514 in a process by using the @samp{p@var{pid}.-1} form of the
38518 @xref{Stop Reply Packets}, for the reply specifications.
38521 @cindex @samp{vCont?} packet
38522 Request a list of actions supported by the @samp{vCont} packet.
38526 @item vCont@r{[};@var{action}@dots{}@r{]}
38527 The @samp{vCont} packet is supported. Each @var{action} is a supported
38528 command in the @samp{vCont} packet.
38530 The @samp{vCont} packet is not supported.
38533 @item vFile:@var{operation}:@var{parameter}@dots{}
38534 @cindex @samp{vFile} packet
38535 Perform a file operation on the target system. For details,
38536 see @ref{Host I/O Packets}.
38538 @item vFlashErase:@var{addr},@var{length}
38539 @cindex @samp{vFlashErase} packet
38540 Direct the stub to erase @var{length} bytes of flash starting at
38541 @var{addr}. The region may enclose any number of flash blocks, but
38542 its start and end must fall on block boundaries, as indicated by the
38543 flash block size appearing in the memory map (@pxref{Memory Map
38544 Format}). @value{GDBN} groups flash memory programming operations
38545 together, and sends a @samp{vFlashDone} request after each group; the
38546 stub is allowed to delay erase operation until the @samp{vFlashDone}
38547 packet is received.
38557 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
38558 @cindex @samp{vFlashWrite} packet
38559 Direct the stub to write data to flash address @var{addr}. The data
38560 is passed in binary form using the same encoding as for the @samp{X}
38561 packet (@pxref{Binary Data}). The memory ranges specified by
38562 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
38563 not overlap, and must appear in order of increasing addresses
38564 (although @samp{vFlashErase} packets for higher addresses may already
38565 have been received; the ordering is guaranteed only between
38566 @samp{vFlashWrite} packets). If a packet writes to an address that was
38567 neither erased by a preceding @samp{vFlashErase} packet nor by some other
38568 target-specific method, the results are unpredictable.
38576 for vFlashWrite addressing non-flash memory
38582 @cindex @samp{vFlashDone} packet
38583 Indicate to the stub that flash programming operation is finished.
38584 The stub is permitted to delay or batch the effects of a group of
38585 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
38586 @samp{vFlashDone} packet is received. The contents of the affected
38587 regions of flash memory are unpredictable until the @samp{vFlashDone}
38588 request is completed.
38590 @item vKill;@var{pid}
38591 @cindex @samp{vKill} packet
38592 Kill the process with the specified process ID. @var{pid} is a
38593 hexadecimal integer identifying the process. This packet is used in
38594 preference to @samp{k} when multiprocess protocol extensions are
38595 supported; see @ref{multiprocess extensions}.
38605 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
38606 @cindex @samp{vRun} packet
38607 Run the program @var{filename}, passing it each @var{argument} on its
38608 command line. The file and arguments are hex-encoded strings. If
38609 @var{filename} is an empty string, the stub may use a default program
38610 (e.g.@: the last program run). The program is created in the stopped
38613 @c FIXME: What about non-stop mode?
38615 This packet is only available in extended mode (@pxref{extended mode}).
38621 @item @r{Any stop packet}
38622 for success (@pxref{Stop Reply Packets})
38626 @cindex @samp{vStopped} packet
38627 @xref{Notification Packets}.
38629 @item X @var{addr},@var{length}:@var{XX@dots{}}
38631 @cindex @samp{X} packet
38632 Write data to memory, where the data is transmitted in binary.
38633 @var{addr} is address, @var{length} is number of bytes,
38634 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
38644 @item z @var{type},@var{addr},@var{kind}
38645 @itemx Z @var{type},@var{addr},@var{kind}
38646 @anchor{insert breakpoint or watchpoint packet}
38647 @cindex @samp{z} packet
38648 @cindex @samp{Z} packets
38649 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
38650 watchpoint starting at address @var{address} of kind @var{kind}.
38652 Each breakpoint and watchpoint packet @var{type} is documented
38655 @emph{Implementation notes: A remote target shall return an empty string
38656 for an unrecognized breakpoint or watchpoint packet @var{type}. A
38657 remote target shall support either both or neither of a given
38658 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
38659 avoid potential problems with duplicate packets, the operations should
38660 be implemented in an idempotent way.}
38662 @item z0,@var{addr},@var{kind}
38663 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
38664 @cindex @samp{z0} packet
38665 @cindex @samp{Z0} packet
38666 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
38667 @var{addr} of type @var{kind}.
38669 A memory breakpoint is implemented by replacing the instruction at
38670 @var{addr} with a software breakpoint or trap instruction. The
38671 @var{kind} is target-specific and typically indicates the size of
38672 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
38673 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
38674 architectures have additional meanings for @var{kind};
38675 @var{cond_list} is an optional list of conditional expressions in bytecode
38676 form that should be evaluated on the target's side. These are the
38677 conditions that should be taken into consideration when deciding if
38678 the breakpoint trigger should be reported back to @var{GDBN}.
38680 The @var{cond_list} parameter is comprised of a series of expressions,
38681 concatenated without separators. Each expression has the following form:
38685 @item X @var{len},@var{expr}
38686 @var{len} is the length of the bytecode expression and @var{expr} is the
38687 actual conditional expression in bytecode form.
38691 The optional @var{cmd_list} parameter introduces commands that may be
38692 run on the target, rather than being reported back to @value{GDBN}.
38693 The parameter starts with a numeric flag @var{persist}; if the flag is
38694 nonzero, then the breakpoint may remain active and the commands
38695 continue to be run even when @value{GDBN} disconnects from the target.
38696 Following this flag is a series of expressions concatenated with no
38697 separators. Each expression has the following form:
38701 @item X @var{len},@var{expr}
38702 @var{len} is the length of the bytecode expression and @var{expr} is the
38703 actual conditional expression in bytecode form.
38707 see @ref{Architecture-Specific Protocol Details}.
38709 @emph{Implementation note: It is possible for a target to copy or move
38710 code that contains memory breakpoints (e.g., when implementing
38711 overlays). The behavior of this packet, in the presence of such a
38712 target, is not defined.}
38724 @item z1,@var{addr},@var{kind}
38725 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
38726 @cindex @samp{z1} packet
38727 @cindex @samp{Z1} packet
38728 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
38729 address @var{addr}.
38731 A hardware breakpoint is implemented using a mechanism that is not
38732 dependant on being able to modify the target's memory. @var{kind}
38733 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
38735 @emph{Implementation note: A hardware breakpoint is not affected by code
38748 @item z2,@var{addr},@var{kind}
38749 @itemx Z2,@var{addr},@var{kind}
38750 @cindex @samp{z2} packet
38751 @cindex @samp{Z2} packet
38752 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
38753 @var{kind} is interpreted as the number of bytes to watch.
38765 @item z3,@var{addr},@var{kind}
38766 @itemx Z3,@var{addr},@var{kind}
38767 @cindex @samp{z3} packet
38768 @cindex @samp{Z3} packet
38769 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
38770 @var{kind} is interpreted as the number of bytes to watch.
38782 @item z4,@var{addr},@var{kind}
38783 @itemx Z4,@var{addr},@var{kind}
38784 @cindex @samp{z4} packet
38785 @cindex @samp{Z4} packet
38786 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
38787 @var{kind} is interpreted as the number of bytes to watch.
38801 @node Stop Reply Packets
38802 @section Stop Reply Packets
38803 @cindex stop reply packets
38805 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
38806 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
38807 receive any of the below as a reply. Except for @samp{?}
38808 and @samp{vStopped}, that reply is only returned
38809 when the target halts. In the below the exact meaning of @dfn{signal
38810 number} is defined by the header @file{include/gdb/signals.h} in the
38811 @value{GDBN} source code.
38813 As in the description of request packets, we include spaces in the
38814 reply templates for clarity; these are not part of the reply packet's
38815 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
38821 The program received signal number @var{AA} (a two-digit hexadecimal
38822 number). This is equivalent to a @samp{T} response with no
38823 @var{n}:@var{r} pairs.
38825 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
38826 @cindex @samp{T} packet reply
38827 The program received signal number @var{AA} (a two-digit hexadecimal
38828 number). This is equivalent to an @samp{S} response, except that the
38829 @samp{@var{n}:@var{r}} pairs can carry values of important registers
38830 and other information directly in the stop reply packet, reducing
38831 round-trip latency. Single-step and breakpoint traps are reported
38832 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
38836 If @var{n} is a hexadecimal number, it is a register number, and the
38837 corresponding @var{r} gives that register's value. @var{r} is a
38838 series of bytes in target byte order, with each byte given by a
38839 two-digit hex number.
38842 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
38843 the stopped thread, as specified in @ref{thread-id syntax}.
38846 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
38847 the core on which the stop event was detected.
38850 If @var{n} is a recognized @dfn{stop reason}, it describes a more
38851 specific event that stopped the target. The currently defined stop
38852 reasons are listed below. @var{aa} should be @samp{05}, the trap
38853 signal. At most one stop reason should be present.
38856 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
38857 and go on to the next; this allows us to extend the protocol in the
38861 The currently defined stop reasons are:
38867 The packet indicates a watchpoint hit, and @var{r} is the data address, in
38870 @cindex shared library events, remote reply
38872 The packet indicates that the loaded libraries have changed.
38873 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
38874 list of loaded libraries. @var{r} is ignored.
38876 @cindex replay log events, remote reply
38878 The packet indicates that the target cannot continue replaying
38879 logged execution events, because it has reached the end (or the
38880 beginning when executing backward) of the log. The value of @var{r}
38881 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
38882 for more information.
38886 @itemx W @var{AA} ; process:@var{pid}
38887 The process exited, and @var{AA} is the exit status. This is only
38888 applicable to certain targets.
38890 The second form of the response, including the process ID of the exited
38891 process, can be used only when @value{GDBN} has reported support for
38892 multiprocess protocol extensions; see @ref{multiprocess extensions}.
38893 The @var{pid} is formatted as a big-endian hex string.
38896 @itemx X @var{AA} ; process:@var{pid}
38897 The process terminated with signal @var{AA}.
38899 The second form of the response, including the process ID of the
38900 terminated process, can be used only when @value{GDBN} has reported
38901 support for multiprocess protocol extensions; see @ref{multiprocess
38902 extensions}. The @var{pid} is formatted as a big-endian hex string.
38904 @item O @var{XX}@dots{}
38905 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
38906 written as the program's console output. This can happen at any time
38907 while the program is running and the debugger should continue to wait
38908 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
38910 @item F @var{call-id},@var{parameter}@dots{}
38911 @var{call-id} is the identifier which says which host system call should
38912 be called. This is just the name of the function. Translation into the
38913 correct system call is only applicable as it's defined in @value{GDBN}.
38914 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
38917 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
38918 this very system call.
38920 The target replies with this packet when it expects @value{GDBN} to
38921 call a host system call on behalf of the target. @value{GDBN} replies
38922 with an appropriate @samp{F} packet and keeps up waiting for the next
38923 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
38924 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
38925 Protocol Extension}, for more details.
38929 @node General Query Packets
38930 @section General Query Packets
38931 @cindex remote query requests
38933 Packets starting with @samp{q} are @dfn{general query packets};
38934 packets starting with @samp{Q} are @dfn{general set packets}. General
38935 query and set packets are a semi-unified form for retrieving and
38936 sending information to and from the stub.
38938 The initial letter of a query or set packet is followed by a name
38939 indicating what sort of thing the packet applies to. For example,
38940 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
38941 definitions with the stub. These packet names follow some
38946 The name must not contain commas, colons or semicolons.
38948 Most @value{GDBN} query and set packets have a leading upper case
38951 The names of custom vendor packets should use a company prefix, in
38952 lower case, followed by a period. For example, packets designed at
38953 the Acme Corporation might begin with @samp{qacme.foo} (for querying
38954 foos) or @samp{Qacme.bar} (for setting bars).
38957 The name of a query or set packet should be separated from any
38958 parameters by a @samp{:}; the parameters themselves should be
38959 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
38960 full packet name, and check for a separator or the end of the packet,
38961 in case two packet names share a common prefix. New packets should not begin
38962 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
38963 packets predate these conventions, and have arguments without any terminator
38964 for the packet name; we suspect they are in widespread use in places that
38965 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
38966 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
38969 Like the descriptions of the other packets, each description here
38970 has a template showing the packet's overall syntax, followed by an
38971 explanation of the packet's meaning. We include spaces in some of the
38972 templates for clarity; these are not part of the packet's syntax. No
38973 @value{GDBN} packet uses spaces to separate its components.
38975 Here are the currently defined query and set packets:
38981 Turn on or off the agent as a helper to perform some debugging operations
38982 delegated from @value{GDBN} (@pxref{Control Agent}).
38984 @item QAllow:@var{op}:@var{val}@dots{}
38985 @cindex @samp{QAllow} packet
38986 Specify which operations @value{GDBN} expects to request of the
38987 target, as a semicolon-separated list of operation name and value
38988 pairs. Possible values for @var{op} include @samp{WriteReg},
38989 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
38990 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
38991 indicating that @value{GDBN} will not request the operation, or 1,
38992 indicating that it may. (The target can then use this to set up its
38993 own internals optimally, for instance if the debugger never expects to
38994 insert breakpoints, it may not need to install its own trap handler.)
38997 @cindex current thread, remote request
38998 @cindex @samp{qC} packet
38999 Return the current thread ID.
39003 @item QC @var{thread-id}
39004 Where @var{thread-id} is a thread ID as documented in
39005 @ref{thread-id syntax}.
39006 @item @r{(anything else)}
39007 Any other reply implies the old thread ID.
39010 @item qCRC:@var{addr},@var{length}
39011 @cindex CRC of memory block, remote request
39012 @cindex @samp{qCRC} packet
39013 Compute the CRC checksum of a block of memory using CRC-32 defined in
39014 IEEE 802.3. The CRC is computed byte at a time, taking the most
39015 significant bit of each byte first. The initial pattern code
39016 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
39018 @emph{Note:} This is the same CRC used in validating separate debug
39019 files (@pxref{Separate Debug Files, , Debugging Information in Separate
39020 Files}). However the algorithm is slightly different. When validating
39021 separate debug files, the CRC is computed taking the @emph{least}
39022 significant bit of each byte first, and the final result is inverted to
39023 detect trailing zeros.
39028 An error (such as memory fault)
39029 @item C @var{crc32}
39030 The specified memory region's checksum is @var{crc32}.
39033 @item QDisableRandomization:@var{value}
39034 @cindex disable address space randomization, remote request
39035 @cindex @samp{QDisableRandomization} packet
39036 Some target operating systems will randomize the virtual address space
39037 of the inferior process as a security feature, but provide a feature
39038 to disable such randomization, e.g.@: to allow for a more deterministic
39039 debugging experience. On such systems, this packet with a @var{value}
39040 of 1 directs the target to disable address space randomization for
39041 processes subsequently started via @samp{vRun} packets, while a packet
39042 with a @var{value} of 0 tells the target to enable address space
39045 This packet is only available in extended mode (@pxref{extended mode}).
39050 The request succeeded.
39053 An error occurred. @var{nn} are hex digits.
39056 An empty reply indicates that @samp{QDisableRandomization} is not supported
39060 This packet is not probed by default; the remote stub must request it,
39061 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39062 This should only be done on targets that actually support disabling
39063 address space randomization.
39066 @itemx qsThreadInfo
39067 @cindex list active threads, remote request
39068 @cindex @samp{qfThreadInfo} packet
39069 @cindex @samp{qsThreadInfo} packet
39070 Obtain a list of all active thread IDs from the target (OS). Since there
39071 may be too many active threads to fit into one reply packet, this query
39072 works iteratively: it may require more than one query/reply sequence to
39073 obtain the entire list of threads. The first query of the sequence will
39074 be the @samp{qfThreadInfo} query; subsequent queries in the
39075 sequence will be the @samp{qsThreadInfo} query.
39077 NOTE: This packet replaces the @samp{qL} query (see below).
39081 @item m @var{thread-id}
39083 @item m @var{thread-id},@var{thread-id}@dots{}
39084 a comma-separated list of thread IDs
39086 (lower case letter @samp{L}) denotes end of list.
39089 In response to each query, the target will reply with a list of one or
39090 more thread IDs, separated by commas.
39091 @value{GDBN} will respond to each reply with a request for more thread
39092 ids (using the @samp{qs} form of the query), until the target responds
39093 with @samp{l} (lower-case ell, for @dfn{last}).
39094 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
39097 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
39098 @cindex get thread-local storage address, remote request
39099 @cindex @samp{qGetTLSAddr} packet
39100 Fetch the address associated with thread local storage specified
39101 by @var{thread-id}, @var{offset}, and @var{lm}.
39103 @var{thread-id} is the thread ID associated with the
39104 thread for which to fetch the TLS address. @xref{thread-id syntax}.
39106 @var{offset} is the (big endian, hex encoded) offset associated with the
39107 thread local variable. (This offset is obtained from the debug
39108 information associated with the variable.)
39110 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
39111 load module associated with the thread local storage. For example,
39112 a @sc{gnu}/Linux system will pass the link map address of the shared
39113 object associated with the thread local storage under consideration.
39114 Other operating environments may choose to represent the load module
39115 differently, so the precise meaning of this parameter will vary.
39119 @item @var{XX}@dots{}
39120 Hex encoded (big endian) bytes representing the address of the thread
39121 local storage requested.
39124 An error occurred. @var{nn} are hex digits.
39127 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
39130 @item qGetTIBAddr:@var{thread-id}
39131 @cindex get thread information block address
39132 @cindex @samp{qGetTIBAddr} packet
39133 Fetch address of the Windows OS specific Thread Information Block.
39135 @var{thread-id} is the thread ID associated with the thread.
39139 @item @var{XX}@dots{}
39140 Hex encoded (big endian) bytes representing the linear address of the
39141 thread information block.
39144 An error occured. This means that either the thread was not found, or the
39145 address could not be retrieved.
39148 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
39151 @item qL @var{startflag} @var{threadcount} @var{nextthread}
39152 Obtain thread information from RTOS. Where: @var{startflag} (one hex
39153 digit) is one to indicate the first query and zero to indicate a
39154 subsequent query; @var{threadcount} (two hex digits) is the maximum
39155 number of threads the response packet can contain; and @var{nextthread}
39156 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
39157 returned in the response as @var{argthread}.
39159 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
39163 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
39164 Where: @var{count} (two hex digits) is the number of threads being
39165 returned; @var{done} (one hex digit) is zero to indicate more threads
39166 and one indicates no further threads; @var{argthreadid} (eight hex
39167 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
39168 is a sequence of thread IDs from the target. @var{threadid} (eight hex
39169 digits). See @code{remote.c:parse_threadlist_response()}.
39173 @cindex section offsets, remote request
39174 @cindex @samp{qOffsets} packet
39175 Get section offsets that the target used when relocating the downloaded
39180 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
39181 Relocate the @code{Text} section by @var{xxx} from its original address.
39182 Relocate the @code{Data} section by @var{yyy} from its original address.
39183 If the object file format provides segment information (e.g.@: @sc{elf}
39184 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
39185 segments by the supplied offsets.
39187 @emph{Note: while a @code{Bss} offset may be included in the response,
39188 @value{GDBN} ignores this and instead applies the @code{Data} offset
39189 to the @code{Bss} section.}
39191 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
39192 Relocate the first segment of the object file, which conventionally
39193 contains program code, to a starting address of @var{xxx}. If
39194 @samp{DataSeg} is specified, relocate the second segment, which
39195 conventionally contains modifiable data, to a starting address of
39196 @var{yyy}. @value{GDBN} will report an error if the object file
39197 does not contain segment information, or does not contain at least
39198 as many segments as mentioned in the reply. Extra segments are
39199 kept at fixed offsets relative to the last relocated segment.
39202 @item qP @var{mode} @var{thread-id}
39203 @cindex thread information, remote request
39204 @cindex @samp{qP} packet
39205 Returns information on @var{thread-id}. Where: @var{mode} is a hex
39206 encoded 32 bit mode; @var{thread-id} is a thread ID
39207 (@pxref{thread-id syntax}).
39209 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
39212 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
39216 @cindex non-stop mode, remote request
39217 @cindex @samp{QNonStop} packet
39219 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
39220 @xref{Remote Non-Stop}, for more information.
39225 The request succeeded.
39228 An error occurred. @var{nn} are hex digits.
39231 An empty reply indicates that @samp{QNonStop} is not supported by
39235 This packet is not probed by default; the remote stub must request it,
39236 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39237 Use of this packet is controlled by the @code{set non-stop} command;
39238 @pxref{Non-Stop Mode}.
39240 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
39241 @cindex pass signals to inferior, remote request
39242 @cindex @samp{QPassSignals} packet
39243 @anchor{QPassSignals}
39244 Each listed @var{signal} should be passed directly to the inferior process.
39245 Signals are numbered identically to continue packets and stop replies
39246 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
39247 strictly greater than the previous item. These signals do not need to stop
39248 the inferior, or be reported to @value{GDBN}. All other signals should be
39249 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
39250 combine; any earlier @samp{QPassSignals} list is completely replaced by the
39251 new list. This packet improves performance when using @samp{handle
39252 @var{signal} nostop noprint pass}.
39257 The request succeeded.
39260 An error occurred. @var{nn} are hex digits.
39263 An empty reply indicates that @samp{QPassSignals} is not supported by
39267 Use of this packet is controlled by the @code{set remote pass-signals}
39268 command (@pxref{Remote Configuration, set remote pass-signals}).
39269 This packet is not probed by default; the remote stub must request it,
39270 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39272 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
39273 @cindex signals the inferior may see, remote request
39274 @cindex @samp{QProgramSignals} packet
39275 @anchor{QProgramSignals}
39276 Each listed @var{signal} may be delivered to the inferior process.
39277 Others should be silently discarded.
39279 In some cases, the remote stub may need to decide whether to deliver a
39280 signal to the program or not without @value{GDBN} involvement. One
39281 example of that is while detaching --- the program's threads may have
39282 stopped for signals that haven't yet had a chance of being reported to
39283 @value{GDBN}, and so the remote stub can use the signal list specified
39284 by this packet to know whether to deliver or ignore those pending
39287 This does not influence whether to deliver a signal as requested by a
39288 resumption packet (@pxref{vCont packet}).
39290 Signals are numbered identically to continue packets and stop replies
39291 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
39292 strictly greater than the previous item. Multiple
39293 @samp{QProgramSignals} packets do not combine; any earlier
39294 @samp{QProgramSignals} list is completely replaced by the new list.
39299 The request succeeded.
39302 An error occurred. @var{nn} are hex digits.
39305 An empty reply indicates that @samp{QProgramSignals} is not supported
39309 Use of this packet is controlled by the @code{set remote program-signals}
39310 command (@pxref{Remote Configuration, set remote program-signals}).
39311 This packet is not probed by default; the remote stub must request it,
39312 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39314 @item qRcmd,@var{command}
39315 @cindex execute remote command, remote request
39316 @cindex @samp{qRcmd} packet
39317 @var{command} (hex encoded) is passed to the local interpreter for
39318 execution. Invalid commands should be reported using the output
39319 string. Before the final result packet, the target may also respond
39320 with a number of intermediate @samp{O@var{output}} console output
39321 packets. @emph{Implementors should note that providing access to a
39322 stubs's interpreter may have security implications}.
39327 A command response with no output.
39329 A command response with the hex encoded output string @var{OUTPUT}.
39331 Indicate a badly formed request.
39333 An empty reply indicates that @samp{qRcmd} is not recognized.
39336 (Note that the @code{qRcmd} packet's name is separated from the
39337 command by a @samp{,}, not a @samp{:}, contrary to the naming
39338 conventions above. Please don't use this packet as a model for new
39341 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
39342 @cindex searching memory, in remote debugging
39344 @cindex @samp{qSearch:memory} packet
39346 @cindex @samp{qSearch memory} packet
39347 @anchor{qSearch memory}
39348 Search @var{length} bytes at @var{address} for @var{search-pattern}.
39349 @var{address} and @var{length} are encoded in hex.
39350 @var{search-pattern} is a sequence of bytes, hex encoded.
39355 The pattern was not found.
39357 The pattern was found at @var{address}.
39359 A badly formed request or an error was encountered while searching memory.
39361 An empty reply indicates that @samp{qSearch:memory} is not recognized.
39364 @item QStartNoAckMode
39365 @cindex @samp{QStartNoAckMode} packet
39366 @anchor{QStartNoAckMode}
39367 Request that the remote stub disable the normal @samp{+}/@samp{-}
39368 protocol acknowledgments (@pxref{Packet Acknowledgment}).
39373 The stub has switched to no-acknowledgment mode.
39374 @value{GDBN} acknowledges this reponse,
39375 but neither the stub nor @value{GDBN} shall send or expect further
39376 @samp{+}/@samp{-} acknowledgments in the current connection.
39378 An empty reply indicates that the stub does not support no-acknowledgment mode.
39381 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
39382 @cindex supported packets, remote query
39383 @cindex features of the remote protocol
39384 @cindex @samp{qSupported} packet
39385 @anchor{qSupported}
39386 Tell the remote stub about features supported by @value{GDBN}, and
39387 query the stub for features it supports. This packet allows
39388 @value{GDBN} and the remote stub to take advantage of each others'
39389 features. @samp{qSupported} also consolidates multiple feature probes
39390 at startup, to improve @value{GDBN} performance---a single larger
39391 packet performs better than multiple smaller probe packets on
39392 high-latency links. Some features may enable behavior which must not
39393 be on by default, e.g.@: because it would confuse older clients or
39394 stubs. Other features may describe packets which could be
39395 automatically probed for, but are not. These features must be
39396 reported before @value{GDBN} will use them. This ``default
39397 unsupported'' behavior is not appropriate for all packets, but it
39398 helps to keep the initial connection time under control with new
39399 versions of @value{GDBN} which support increasing numbers of packets.
39403 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
39404 The stub supports or does not support each returned @var{stubfeature},
39405 depending on the form of each @var{stubfeature} (see below for the
39408 An empty reply indicates that @samp{qSupported} is not recognized,
39409 or that no features needed to be reported to @value{GDBN}.
39412 The allowed forms for each feature (either a @var{gdbfeature} in the
39413 @samp{qSupported} packet, or a @var{stubfeature} in the response)
39417 @item @var{name}=@var{value}
39418 The remote protocol feature @var{name} is supported, and associated
39419 with the specified @var{value}. The format of @var{value} depends
39420 on the feature, but it must not include a semicolon.
39422 The remote protocol feature @var{name} is supported, and does not
39423 need an associated value.
39425 The remote protocol feature @var{name} is not supported.
39427 The remote protocol feature @var{name} may be supported, and
39428 @value{GDBN} should auto-detect support in some other way when it is
39429 needed. This form will not be used for @var{gdbfeature} notifications,
39430 but may be used for @var{stubfeature} responses.
39433 Whenever the stub receives a @samp{qSupported} request, the
39434 supplied set of @value{GDBN} features should override any previous
39435 request. This allows @value{GDBN} to put the stub in a known
39436 state, even if the stub had previously been communicating with
39437 a different version of @value{GDBN}.
39439 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
39444 This feature indicates whether @value{GDBN} supports multiprocess
39445 extensions to the remote protocol. @value{GDBN} does not use such
39446 extensions unless the stub also reports that it supports them by
39447 including @samp{multiprocess+} in its @samp{qSupported} reply.
39448 @xref{multiprocess extensions}, for details.
39451 This feature indicates that @value{GDBN} supports the XML target
39452 description. If the stub sees @samp{xmlRegisters=} with target
39453 specific strings separated by a comma, it will report register
39457 This feature indicates whether @value{GDBN} supports the
39458 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
39459 instruction reply packet}).
39462 Stubs should ignore any unknown values for
39463 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
39464 packet supports receiving packets of unlimited length (earlier
39465 versions of @value{GDBN} may reject overly long responses). Additional values
39466 for @var{gdbfeature} may be defined in the future to let the stub take
39467 advantage of new features in @value{GDBN}, e.g.@: incompatible
39468 improvements in the remote protocol---the @samp{multiprocess} feature is
39469 an example of such a feature. The stub's reply should be independent
39470 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
39471 describes all the features it supports, and then the stub replies with
39472 all the features it supports.
39474 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
39475 responses, as long as each response uses one of the standard forms.
39477 Some features are flags. A stub which supports a flag feature
39478 should respond with a @samp{+} form response. Other features
39479 require values, and the stub should respond with an @samp{=}
39482 Each feature has a default value, which @value{GDBN} will use if
39483 @samp{qSupported} is not available or if the feature is not mentioned
39484 in the @samp{qSupported} response. The default values are fixed; a
39485 stub is free to omit any feature responses that match the defaults.
39487 Not all features can be probed, but for those which can, the probing
39488 mechanism is useful: in some cases, a stub's internal
39489 architecture may not allow the protocol layer to know some information
39490 about the underlying target in advance. This is especially common in
39491 stubs which may be configured for multiple targets.
39493 These are the currently defined stub features and their properties:
39495 @multitable @columnfractions 0.35 0.2 0.12 0.2
39496 @c NOTE: The first row should be @headitem, but we do not yet require
39497 @c a new enough version of Texinfo (4.7) to use @headitem.
39499 @tab Value Required
39503 @item @samp{PacketSize}
39508 @item @samp{qXfer:auxv:read}
39513 @item @samp{qXfer:btrace:read}
39518 @item @samp{qXfer:features:read}
39523 @item @samp{qXfer:libraries:read}
39528 @item @samp{qXfer:libraries-svr4:read}
39533 @item @samp{augmented-libraries-svr4-read}
39538 @item @samp{qXfer:memory-map:read}
39543 @item @samp{qXfer:sdata:read}
39548 @item @samp{qXfer:spu:read}
39553 @item @samp{qXfer:spu:write}
39558 @item @samp{qXfer:siginfo:read}
39563 @item @samp{qXfer:siginfo:write}
39568 @item @samp{qXfer:threads:read}
39573 @item @samp{qXfer:traceframe-info:read}
39578 @item @samp{qXfer:uib:read}
39583 @item @samp{qXfer:fdpic:read}
39588 @item @samp{Qbtrace:off}
39593 @item @samp{Qbtrace:bts}
39598 @item @samp{QNonStop}
39603 @item @samp{QPassSignals}
39608 @item @samp{QStartNoAckMode}
39613 @item @samp{multiprocess}
39618 @item @samp{ConditionalBreakpoints}
39623 @item @samp{ConditionalTracepoints}
39628 @item @samp{ReverseContinue}
39633 @item @samp{ReverseStep}
39638 @item @samp{TracepointSource}
39643 @item @samp{QAgent}
39648 @item @samp{QAllow}
39653 @item @samp{QDisableRandomization}
39658 @item @samp{EnableDisableTracepoints}
39663 @item @samp{QTBuffer:size}
39668 @item @samp{tracenz}
39673 @item @samp{BreakpointCommands}
39680 These are the currently defined stub features, in more detail:
39683 @cindex packet size, remote protocol
39684 @item PacketSize=@var{bytes}
39685 The remote stub can accept packets up to at least @var{bytes} in
39686 length. @value{GDBN} will send packets up to this size for bulk
39687 transfers, and will never send larger packets. This is a limit on the
39688 data characters in the packet, including the frame and checksum.
39689 There is no trailing NUL byte in a remote protocol packet; if the stub
39690 stores packets in a NUL-terminated format, it should allow an extra
39691 byte in its buffer for the NUL. If this stub feature is not supported,
39692 @value{GDBN} guesses based on the size of the @samp{g} packet response.
39694 @item qXfer:auxv:read
39695 The remote stub understands the @samp{qXfer:auxv:read} packet
39696 (@pxref{qXfer auxiliary vector read}).
39698 @item qXfer:btrace:read
39699 The remote stub understands the @samp{qXfer:btrace:read}
39700 packet (@pxref{qXfer btrace read}).
39702 @item qXfer:features:read
39703 The remote stub understands the @samp{qXfer:features:read} packet
39704 (@pxref{qXfer target description read}).
39706 @item qXfer:libraries:read
39707 The remote stub understands the @samp{qXfer:libraries:read} packet
39708 (@pxref{qXfer library list read}).
39710 @item qXfer:libraries-svr4:read
39711 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
39712 (@pxref{qXfer svr4 library list read}).
39714 @item augmented-libraries-svr4-read
39715 The remote stub understands the augmented form of the
39716 @samp{qXfer:libraries-svr4:read} packet
39717 (@pxref{qXfer svr4 library list read}).
39719 @item qXfer:memory-map:read
39720 The remote stub understands the @samp{qXfer:memory-map:read} packet
39721 (@pxref{qXfer memory map read}).
39723 @item qXfer:sdata:read
39724 The remote stub understands the @samp{qXfer:sdata:read} packet
39725 (@pxref{qXfer sdata read}).
39727 @item qXfer:spu:read
39728 The remote stub understands the @samp{qXfer:spu:read} packet
39729 (@pxref{qXfer spu read}).
39731 @item qXfer:spu:write
39732 The remote stub understands the @samp{qXfer:spu:write} packet
39733 (@pxref{qXfer spu write}).
39735 @item qXfer:siginfo:read
39736 The remote stub understands the @samp{qXfer:siginfo:read} packet
39737 (@pxref{qXfer siginfo read}).
39739 @item qXfer:siginfo:write
39740 The remote stub understands the @samp{qXfer:siginfo:write} packet
39741 (@pxref{qXfer siginfo write}).
39743 @item qXfer:threads:read
39744 The remote stub understands the @samp{qXfer:threads:read} packet
39745 (@pxref{qXfer threads read}).
39747 @item qXfer:traceframe-info:read
39748 The remote stub understands the @samp{qXfer:traceframe-info:read}
39749 packet (@pxref{qXfer traceframe info read}).
39751 @item qXfer:uib:read
39752 The remote stub understands the @samp{qXfer:uib:read}
39753 packet (@pxref{qXfer unwind info block}).
39755 @item qXfer:fdpic:read
39756 The remote stub understands the @samp{qXfer:fdpic:read}
39757 packet (@pxref{qXfer fdpic loadmap read}).
39760 The remote stub understands the @samp{QNonStop} packet
39761 (@pxref{QNonStop}).
39764 The remote stub understands the @samp{QPassSignals} packet
39765 (@pxref{QPassSignals}).
39767 @item QStartNoAckMode
39768 The remote stub understands the @samp{QStartNoAckMode} packet and
39769 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
39772 @anchor{multiprocess extensions}
39773 @cindex multiprocess extensions, in remote protocol
39774 The remote stub understands the multiprocess extensions to the remote
39775 protocol syntax. The multiprocess extensions affect the syntax of
39776 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
39777 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
39778 replies. Note that reporting this feature indicates support for the
39779 syntactic extensions only, not that the stub necessarily supports
39780 debugging of more than one process at a time. The stub must not use
39781 multiprocess extensions in packet replies unless @value{GDBN} has also
39782 indicated it supports them in its @samp{qSupported} request.
39784 @item qXfer:osdata:read
39785 The remote stub understands the @samp{qXfer:osdata:read} packet
39786 ((@pxref{qXfer osdata read}).
39788 @item ConditionalBreakpoints
39789 The target accepts and implements evaluation of conditional expressions
39790 defined for breakpoints. The target will only report breakpoint triggers
39791 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
39793 @item ConditionalTracepoints
39794 The remote stub accepts and implements conditional expressions defined
39795 for tracepoints (@pxref{Tracepoint Conditions}).
39797 @item ReverseContinue
39798 The remote stub accepts and implements the reverse continue packet
39802 The remote stub accepts and implements the reverse step packet
39805 @item TracepointSource
39806 The remote stub understands the @samp{QTDPsrc} packet that supplies
39807 the source form of tracepoint definitions.
39810 The remote stub understands the @samp{QAgent} packet.
39813 The remote stub understands the @samp{QAllow} packet.
39815 @item QDisableRandomization
39816 The remote stub understands the @samp{QDisableRandomization} packet.
39818 @item StaticTracepoint
39819 @cindex static tracepoints, in remote protocol
39820 The remote stub supports static tracepoints.
39822 @item InstallInTrace
39823 @anchor{install tracepoint in tracing}
39824 The remote stub supports installing tracepoint in tracing.
39826 @item EnableDisableTracepoints
39827 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
39828 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
39829 to be enabled and disabled while a trace experiment is running.
39831 @item QTBuffer:size
39832 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
39833 packet that allows to change the size of the trace buffer.
39836 @cindex string tracing, in remote protocol
39837 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
39838 See @ref{Bytecode Descriptions} for details about the bytecode.
39840 @item BreakpointCommands
39841 @cindex breakpoint commands, in remote protocol
39842 The remote stub supports running a breakpoint's command list itself,
39843 rather than reporting the hit to @value{GDBN}.
39846 The remote stub understands the @samp{Qbtrace:off} packet.
39849 The remote stub understands the @samp{Qbtrace:bts} packet.
39854 @cindex symbol lookup, remote request
39855 @cindex @samp{qSymbol} packet
39856 Notify the target that @value{GDBN} is prepared to serve symbol lookup
39857 requests. Accept requests from the target for the values of symbols.
39862 The target does not need to look up any (more) symbols.
39863 @item qSymbol:@var{sym_name}
39864 The target requests the value of symbol @var{sym_name} (hex encoded).
39865 @value{GDBN} may provide the value by using the
39866 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
39870 @item qSymbol:@var{sym_value}:@var{sym_name}
39871 Set the value of @var{sym_name} to @var{sym_value}.
39873 @var{sym_name} (hex encoded) is the name of a symbol whose value the
39874 target has previously requested.
39876 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
39877 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
39883 The target does not need to look up any (more) symbols.
39884 @item qSymbol:@var{sym_name}
39885 The target requests the value of a new symbol @var{sym_name} (hex
39886 encoded). @value{GDBN} will continue to supply the values of symbols
39887 (if available), until the target ceases to request them.
39892 @itemx QTDisconnected
39899 @itemx qTMinFTPILen
39901 @xref{Tracepoint Packets}.
39903 @item qThreadExtraInfo,@var{thread-id}
39904 @cindex thread attributes info, remote request
39905 @cindex @samp{qThreadExtraInfo} packet
39906 Obtain a printable string description of a thread's attributes from
39907 the target OS. @var{thread-id} is a thread ID;
39908 see @ref{thread-id syntax}. This
39909 string may contain anything that the target OS thinks is interesting
39910 for @value{GDBN} to tell the user about the thread. The string is
39911 displayed in @value{GDBN}'s @code{info threads} display. Some
39912 examples of possible thread extra info strings are @samp{Runnable}, or
39913 @samp{Blocked on Mutex}.
39917 @item @var{XX}@dots{}
39918 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
39919 comprising the printable string containing the extra information about
39920 the thread's attributes.
39923 (Note that the @code{qThreadExtraInfo} packet's name is separated from
39924 the command by a @samp{,}, not a @samp{:}, contrary to the naming
39925 conventions above. Please don't use this packet as a model for new
39944 @xref{Tracepoint Packets}.
39946 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
39947 @cindex read special object, remote request
39948 @cindex @samp{qXfer} packet
39949 @anchor{qXfer read}
39950 Read uninterpreted bytes from the target's special data area
39951 identified by the keyword @var{object}. Request @var{length} bytes
39952 starting at @var{offset} bytes into the data. The content and
39953 encoding of @var{annex} is specific to @var{object}; it can supply
39954 additional details about what data to access.
39956 Here are the specific requests of this form defined so far. All
39957 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
39958 formats, listed below.
39961 @item qXfer:auxv:read::@var{offset},@var{length}
39962 @anchor{qXfer auxiliary vector read}
39963 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
39964 auxiliary vector}. Note @var{annex} must be empty.
39966 This packet is not probed by default; the remote stub must request it,
39967 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39969 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
39970 @anchor{qXfer btrace read}
39972 Return a description of the current branch trace.
39973 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
39974 packet may have one of the following values:
39978 Returns all available branch trace.
39981 Returns all available branch trace if the branch trace changed since
39982 the last read request.
39985 Returns the new branch trace since the last read request. Adds a new
39986 block to the end of the trace that begins at zero and ends at the source
39987 location of the first branch in the trace buffer. This extra block is
39988 used to stitch traces together.
39990 If the trace buffer overflowed, returns an error indicating the overflow.
39993 This packet is not probed by default; the remote stub must request it
39994 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39996 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
39997 @anchor{qXfer target description read}
39998 Access the @dfn{target description}. @xref{Target Descriptions}. The
39999 annex specifies which XML document to access. The main description is
40000 always loaded from the @samp{target.xml} annex.
40002 This packet is not probed by default; the remote stub must request it,
40003 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40005 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
40006 @anchor{qXfer library list read}
40007 Access the target's list of loaded libraries. @xref{Library List Format}.
40008 The annex part of the generic @samp{qXfer} packet must be empty
40009 (@pxref{qXfer read}).
40011 Targets which maintain a list of libraries in the program's memory do
40012 not need to implement this packet; it is designed for platforms where
40013 the operating system manages the list of loaded libraries.
40015 This packet is not probed by default; the remote stub must request it,
40016 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40018 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
40019 @anchor{qXfer svr4 library list read}
40020 Access the target's list of loaded libraries when the target is an SVR4
40021 platform. @xref{Library List Format for SVR4 Targets}. The annex part
40022 of the generic @samp{qXfer} packet must be empty unless the remote
40023 stub indicated it supports the augmented form of this packet
40024 by supplying an appropriate @samp{qSupported} response
40025 (@pxref{qXfer read}, @ref{qSupported}).
40027 This packet is optional for better performance on SVR4 targets.
40028 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
40030 This packet is not probed by default; the remote stub must request it,
40031 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40033 If the remote stub indicates it supports the augmented form of this
40034 packet then the annex part of the generic @samp{qXfer} packet may
40035 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
40036 arguments. The currently supported arguments are:
40039 @item start=@var{address}
40040 A hexadecimal number specifying the address of the @samp{struct
40041 link_map} to start reading the library list from. If unset or zero
40042 then the first @samp{struct link_map} in the library list will be
40043 chosen as the starting point.
40045 @item prev=@var{address}
40046 A hexadecimal number specifying the address of the @samp{struct
40047 link_map} immediately preceding the @samp{struct link_map}
40048 specified by the @samp{start} argument. If unset or zero then
40049 the remote stub will expect that no @samp{struct link_map}
40050 exists prior to the starting point.
40054 Arguments that are not understood by the remote stub will be silently
40057 @item qXfer:memory-map:read::@var{offset},@var{length}
40058 @anchor{qXfer memory map read}
40059 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
40060 annex part of the generic @samp{qXfer} packet must be empty
40061 (@pxref{qXfer read}).
40063 This packet is not probed by default; the remote stub must request it,
40064 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40066 @item qXfer:sdata:read::@var{offset},@var{length}
40067 @anchor{qXfer sdata read}
40069 Read contents of the extra collected static tracepoint marker
40070 information. The annex part of the generic @samp{qXfer} packet must
40071 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
40074 This packet is not probed by default; the remote stub must request it,
40075 by supplying an appropriate @samp{qSupported} response
40076 (@pxref{qSupported}).
40078 @item qXfer:siginfo:read::@var{offset},@var{length}
40079 @anchor{qXfer siginfo read}
40080 Read contents of the extra signal information on the target
40081 system. The annex part of the generic @samp{qXfer} packet must be
40082 empty (@pxref{qXfer read}).
40084 This packet is not probed by default; the remote stub must request it,
40085 by supplying an appropriate @samp{qSupported} response
40086 (@pxref{qSupported}).
40088 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
40089 @anchor{qXfer spu read}
40090 Read contents of an @code{spufs} file on the target system. The
40091 annex specifies which file to read; it must be of the form
40092 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
40093 in the target process, and @var{name} identifes the @code{spufs} file
40094 in that context to be accessed.
40096 This packet is not probed by default; the remote stub must request it,
40097 by supplying an appropriate @samp{qSupported} response
40098 (@pxref{qSupported}).
40100 @item qXfer:threads:read::@var{offset},@var{length}
40101 @anchor{qXfer threads read}
40102 Access the list of threads on target. @xref{Thread List Format}. The
40103 annex part of the generic @samp{qXfer} packet must be empty
40104 (@pxref{qXfer read}).
40106 This packet is not probed by default; the remote stub must request it,
40107 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40109 @item qXfer:traceframe-info:read::@var{offset},@var{length}
40110 @anchor{qXfer traceframe info read}
40112 Return a description of the current traceframe's contents.
40113 @xref{Traceframe Info Format}. The annex part of the generic
40114 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
40116 This packet is not probed by default; the remote stub must request it,
40117 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40119 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
40120 @anchor{qXfer unwind info block}
40122 Return the unwind information block for @var{pc}. This packet is used
40123 on OpenVMS/ia64 to ask the kernel unwind information.
40125 This packet is not probed by default.
40127 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
40128 @anchor{qXfer fdpic loadmap read}
40129 Read contents of @code{loadmap}s on the target system. The
40130 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
40131 executable @code{loadmap} or interpreter @code{loadmap} to read.
40133 This packet is not probed by default; the remote stub must request it,
40134 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40136 @item qXfer:osdata:read::@var{offset},@var{length}
40137 @anchor{qXfer osdata read}
40138 Access the target's @dfn{operating system information}.
40139 @xref{Operating System Information}.
40146 Data @var{data} (@pxref{Binary Data}) has been read from the
40147 target. There may be more data at a higher address (although
40148 it is permitted to return @samp{m} even for the last valid
40149 block of data, as long as at least one byte of data was read).
40150 @var{data} may have fewer bytes than the @var{length} in the
40154 Data @var{data} (@pxref{Binary Data}) has been read from the target.
40155 There is no more data to be read. @var{data} may have fewer bytes
40156 than the @var{length} in the request.
40159 The @var{offset} in the request is at the end of the data.
40160 There is no more data to be read.
40163 The request was malformed, or @var{annex} was invalid.
40166 The offset was invalid, or there was an error encountered reading the data.
40167 @var{nn} is a hex-encoded @code{errno} value.
40170 An empty reply indicates the @var{object} string was not recognized by
40171 the stub, or that the object does not support reading.
40174 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
40175 @cindex write data into object, remote request
40176 @anchor{qXfer write}
40177 Write uninterpreted bytes into the target's special data area
40178 identified by the keyword @var{object}, starting at @var{offset} bytes
40179 into the data. @var{data}@dots{} is the binary-encoded data
40180 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
40181 is specific to @var{object}; it can supply additional details about what data
40184 Here are the specific requests of this form defined so far. All
40185 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
40186 formats, listed below.
40189 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
40190 @anchor{qXfer siginfo write}
40191 Write @var{data} to the extra signal information on the target system.
40192 The annex part of the generic @samp{qXfer} packet must be
40193 empty (@pxref{qXfer write}).
40195 This packet is not probed by default; the remote stub must request it,
40196 by supplying an appropriate @samp{qSupported} response
40197 (@pxref{qSupported}).
40199 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
40200 @anchor{qXfer spu write}
40201 Write @var{data} to an @code{spufs} file on the target system. The
40202 annex specifies which file to write; it must be of the form
40203 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
40204 in the target process, and @var{name} identifes the @code{spufs} file
40205 in that context to be accessed.
40207 This packet is not probed by default; the remote stub must request it,
40208 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40214 @var{nn} (hex encoded) is the number of bytes written.
40215 This may be fewer bytes than supplied in the request.
40218 The request was malformed, or @var{annex} was invalid.
40221 The offset was invalid, or there was an error encountered writing the data.
40222 @var{nn} is a hex-encoded @code{errno} value.
40225 An empty reply indicates the @var{object} string was not
40226 recognized by the stub, or that the object does not support writing.
40229 @item qXfer:@var{object}:@var{operation}:@dots{}
40230 Requests of this form may be added in the future. When a stub does
40231 not recognize the @var{object} keyword, or its support for
40232 @var{object} does not recognize the @var{operation} keyword, the stub
40233 must respond with an empty packet.
40235 @item qAttached:@var{pid}
40236 @cindex query attached, remote request
40237 @cindex @samp{qAttached} packet
40238 Return an indication of whether the remote server attached to an
40239 existing process or created a new process. When the multiprocess
40240 protocol extensions are supported (@pxref{multiprocess extensions}),
40241 @var{pid} is an integer in hexadecimal format identifying the target
40242 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
40243 the query packet will be simplified as @samp{qAttached}.
40245 This query is used, for example, to know whether the remote process
40246 should be detached or killed when a @value{GDBN} session is ended with
40247 the @code{quit} command.
40252 The remote server attached to an existing process.
40254 The remote server created a new process.
40256 A badly formed request or an error was encountered.
40260 Enable branch tracing for the current thread using bts tracing.
40265 Branch tracing has been enabled.
40267 A badly formed request or an error was encountered.
40271 Disable branch tracing for the current thread.
40276 Branch tracing has been disabled.
40278 A badly formed request or an error was encountered.
40283 @node Architecture-Specific Protocol Details
40284 @section Architecture-Specific Protocol Details
40286 This section describes how the remote protocol is applied to specific
40287 target architectures. Also see @ref{Standard Target Features}, for
40288 details of XML target descriptions for each architecture.
40291 * ARM-Specific Protocol Details::
40292 * MIPS-Specific Protocol Details::
40295 @node ARM-Specific Protocol Details
40296 @subsection @acronym{ARM}-specific Protocol Details
40299 * ARM Breakpoint Kinds::
40302 @node ARM Breakpoint Kinds
40303 @subsubsection @acronym{ARM} Breakpoint Kinds
40304 @cindex breakpoint kinds, @acronym{ARM}
40306 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
40311 16-bit Thumb mode breakpoint.
40314 32-bit Thumb mode (Thumb-2) breakpoint.
40317 32-bit @acronym{ARM} mode breakpoint.
40321 @node MIPS-Specific Protocol Details
40322 @subsection @acronym{MIPS}-specific Protocol Details
40325 * MIPS Register packet Format::
40326 * MIPS Breakpoint Kinds::
40329 @node MIPS Register packet Format
40330 @subsubsection @acronym{MIPS} Register Packet Format
40331 @cindex register packet format, @acronym{MIPS}
40333 The following @code{g}/@code{G} packets have previously been defined.
40334 In the below, some thirty-two bit registers are transferred as
40335 sixty-four bits. Those registers should be zero/sign extended (which?)
40336 to fill the space allocated. Register bytes are transferred in target
40337 byte order. The two nibbles within a register byte are transferred
40338 most-significant -- least-significant.
40343 All registers are transferred as thirty-two bit quantities in the order:
40344 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
40345 registers; fsr; fir; fp.
40348 All registers are transferred as sixty-four bit quantities (including
40349 thirty-two bit registers such as @code{sr}). The ordering is the same
40354 @node MIPS Breakpoint Kinds
40355 @subsubsection @acronym{MIPS} Breakpoint Kinds
40356 @cindex breakpoint kinds, @acronym{MIPS}
40358 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
40363 16-bit @acronym{MIPS16} mode breakpoint.
40366 16-bit @acronym{microMIPS} mode breakpoint.
40369 32-bit standard @acronym{MIPS} mode breakpoint.
40372 32-bit @acronym{microMIPS} mode breakpoint.
40376 @node Tracepoint Packets
40377 @section Tracepoint Packets
40378 @cindex tracepoint packets
40379 @cindex packets, tracepoint
40381 Here we describe the packets @value{GDBN} uses to implement
40382 tracepoints (@pxref{Tracepoints}).
40386 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
40387 @cindex @samp{QTDP} packet
40388 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
40389 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
40390 the tracepoint is disabled. @var{step} is the tracepoint's step
40391 count, and @var{pass} is its pass count. If an @samp{F} is present,
40392 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
40393 the number of bytes that the target should copy elsewhere to make room
40394 for the tracepoint. If an @samp{X} is present, it introduces a
40395 tracepoint condition, which consists of a hexadecimal length, followed
40396 by a comma and hex-encoded bytes, in a manner similar to action
40397 encodings as described below. If the trailing @samp{-} is present,
40398 further @samp{QTDP} packets will follow to specify this tracepoint's
40404 The packet was understood and carried out.
40406 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
40408 The packet was not recognized.
40411 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
40412 Define actions to be taken when a tracepoint is hit. @var{n} and
40413 @var{addr} must be the same as in the initial @samp{QTDP} packet for
40414 this tracepoint. This packet may only be sent immediately after
40415 another @samp{QTDP} packet that ended with a @samp{-}. If the
40416 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
40417 specifying more actions for this tracepoint.
40419 In the series of action packets for a given tracepoint, at most one
40420 can have an @samp{S} before its first @var{action}. If such a packet
40421 is sent, it and the following packets define ``while-stepping''
40422 actions. Any prior packets define ordinary actions --- that is, those
40423 taken when the tracepoint is first hit. If no action packet has an
40424 @samp{S}, then all the packets in the series specify ordinary
40425 tracepoint actions.
40427 The @samp{@var{action}@dots{}} portion of the packet is a series of
40428 actions, concatenated without separators. Each action has one of the
40434 Collect the registers whose bits are set in @var{mask}. @var{mask} is
40435 a hexadecimal number whose @var{i}'th bit is set if register number
40436 @var{i} should be collected. (The least significant bit is numbered
40437 zero.) Note that @var{mask} may be any number of digits long; it may
40438 not fit in a 32-bit word.
40440 @item M @var{basereg},@var{offset},@var{len}
40441 Collect @var{len} bytes of memory starting at the address in register
40442 number @var{basereg}, plus @var{offset}. If @var{basereg} is
40443 @samp{-1}, then the range has a fixed address: @var{offset} is the
40444 address of the lowest byte to collect. The @var{basereg},
40445 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
40446 values (the @samp{-1} value for @var{basereg} is a special case).
40448 @item X @var{len},@var{expr}
40449 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
40450 it directs. @var{expr} is an agent expression, as described in
40451 @ref{Agent Expressions}. Each byte of the expression is encoded as a
40452 two-digit hex number in the packet; @var{len} is the number of bytes
40453 in the expression (and thus one-half the number of hex digits in the
40458 Any number of actions may be packed together in a single @samp{QTDP}
40459 packet, as long as the packet does not exceed the maximum packet
40460 length (400 bytes, for many stubs). There may be only one @samp{R}
40461 action per tracepoint, and it must precede any @samp{M} or @samp{X}
40462 actions. Any registers referred to by @samp{M} and @samp{X} actions
40463 must be collected by a preceding @samp{R} action. (The
40464 ``while-stepping'' actions are treated as if they were attached to a
40465 separate tracepoint, as far as these restrictions are concerned.)
40470 The packet was understood and carried out.
40472 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
40474 The packet was not recognized.
40477 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
40478 @cindex @samp{QTDPsrc} packet
40479 Specify a source string of tracepoint @var{n} at address @var{addr}.
40480 This is useful to get accurate reproduction of the tracepoints
40481 originally downloaded at the beginning of the trace run. @var{type}
40482 is the name of the tracepoint part, such as @samp{cond} for the
40483 tracepoint's conditional expression (see below for a list of types), while
40484 @var{bytes} is the string, encoded in hexadecimal.
40486 @var{start} is the offset of the @var{bytes} within the overall source
40487 string, while @var{slen} is the total length of the source string.
40488 This is intended for handling source strings that are longer than will
40489 fit in a single packet.
40490 @c Add detailed example when this info is moved into a dedicated
40491 @c tracepoint descriptions section.
40493 The available string types are @samp{at} for the location,
40494 @samp{cond} for the conditional, and @samp{cmd} for an action command.
40495 @value{GDBN} sends a separate packet for each command in the action
40496 list, in the same order in which the commands are stored in the list.
40498 The target does not need to do anything with source strings except
40499 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
40502 Although this packet is optional, and @value{GDBN} will only send it
40503 if the target replies with @samp{TracepointSource} @xref{General
40504 Query Packets}, it makes both disconnected tracing and trace files
40505 much easier to use. Otherwise the user must be careful that the
40506 tracepoints in effect while looking at trace frames are identical to
40507 the ones in effect during the trace run; even a small discrepancy
40508 could cause @samp{tdump} not to work, or a particular trace frame not
40511 @item QTDV:@var{n}:@var{value}
40512 @cindex define trace state variable, remote request
40513 @cindex @samp{QTDV} packet
40514 Create a new trace state variable, number @var{n}, with an initial
40515 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
40516 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
40517 the option of not using this packet for initial values of zero; the
40518 target should simply create the trace state variables as they are
40519 mentioned in expressions.
40521 @item QTFrame:@var{n}
40522 @cindex @samp{QTFrame} packet
40523 Select the @var{n}'th tracepoint frame from the buffer, and use the
40524 register and memory contents recorded there to answer subsequent
40525 request packets from @value{GDBN}.
40527 A successful reply from the stub indicates that the stub has found the
40528 requested frame. The response is a series of parts, concatenated
40529 without separators, describing the frame we selected. Each part has
40530 one of the following forms:
40534 The selected frame is number @var{n} in the trace frame buffer;
40535 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
40536 was no frame matching the criteria in the request packet.
40539 The selected trace frame records a hit of tracepoint number @var{t};
40540 @var{t} is a hexadecimal number.
40544 @item QTFrame:pc:@var{addr}
40545 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40546 currently selected frame whose PC is @var{addr};
40547 @var{addr} is a hexadecimal number.
40549 @item QTFrame:tdp:@var{t}
40550 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40551 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
40552 is a hexadecimal number.
40554 @item QTFrame:range:@var{start}:@var{end}
40555 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40556 currently selected frame whose PC is between @var{start} (inclusive)
40557 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
40560 @item QTFrame:outside:@var{start}:@var{end}
40561 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
40562 frame @emph{outside} the given range of addresses (exclusive).
40565 @cindex @samp{qTMinFTPILen} packet
40566 This packet requests the minimum length of instruction at which a fast
40567 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
40568 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
40569 it depends on the target system being able to create trampolines in
40570 the first 64K of memory, which might or might not be possible for that
40571 system. So the reply to this packet will be 4 if it is able to
40578 The minimum instruction length is currently unknown.
40580 The minimum instruction length is @var{length}, where @var{length} is greater
40581 or equal to 1. @var{length} is a hexadecimal number. A reply of 1 means
40582 that a fast tracepoint may be placed on any instruction regardless of size.
40584 An error has occurred.
40586 An empty reply indicates that the request is not supported by the stub.
40590 @cindex @samp{QTStart} packet
40591 Begin the tracepoint experiment. Begin collecting data from
40592 tracepoint hits in the trace frame buffer. This packet supports the
40593 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
40594 instruction reply packet}).
40597 @cindex @samp{QTStop} packet
40598 End the tracepoint experiment. Stop collecting trace frames.
40600 @item QTEnable:@var{n}:@var{addr}
40602 @cindex @samp{QTEnable} packet
40603 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
40604 experiment. If the tracepoint was previously disabled, then collection
40605 of data from it will resume.
40607 @item QTDisable:@var{n}:@var{addr}
40609 @cindex @samp{QTDisable} packet
40610 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
40611 experiment. No more data will be collected from the tracepoint unless
40612 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
40615 @cindex @samp{QTinit} packet
40616 Clear the table of tracepoints, and empty the trace frame buffer.
40618 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
40619 @cindex @samp{QTro} packet
40620 Establish the given ranges of memory as ``transparent''. The stub
40621 will answer requests for these ranges from memory's current contents,
40622 if they were not collected as part of the tracepoint hit.
40624 @value{GDBN} uses this to mark read-only regions of memory, like those
40625 containing program code. Since these areas never change, they should
40626 still have the same contents they did when the tracepoint was hit, so
40627 there's no reason for the stub to refuse to provide their contents.
40629 @item QTDisconnected:@var{value}
40630 @cindex @samp{QTDisconnected} packet
40631 Set the choice to what to do with the tracing run when @value{GDBN}
40632 disconnects from the target. A @var{value} of 1 directs the target to
40633 continue the tracing run, while 0 tells the target to stop tracing if
40634 @value{GDBN} is no longer in the picture.
40637 @cindex @samp{qTStatus} packet
40638 Ask the stub if there is a trace experiment running right now.
40640 The reply has the form:
40644 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
40645 @var{running} is a single digit @code{1} if the trace is presently
40646 running, or @code{0} if not. It is followed by semicolon-separated
40647 optional fields that an agent may use to report additional status.
40651 If the trace is not running, the agent may report any of several
40652 explanations as one of the optional fields:
40657 No trace has been run yet.
40659 @item tstop[:@var{text}]:0
40660 The trace was stopped by a user-originated stop command. The optional
40661 @var{text} field is a user-supplied string supplied as part of the
40662 stop command (for instance, an explanation of why the trace was
40663 stopped manually). It is hex-encoded.
40666 The trace stopped because the trace buffer filled up.
40668 @item tdisconnected:0
40669 The trace stopped because @value{GDBN} disconnected from the target.
40671 @item tpasscount:@var{tpnum}
40672 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
40674 @item terror:@var{text}:@var{tpnum}
40675 The trace stopped because tracepoint @var{tpnum} had an error. The
40676 string @var{text} is available to describe the nature of the error
40677 (for instance, a divide by zero in the condition expression).
40678 @var{text} is hex encoded.
40681 The trace stopped for some other reason.
40685 Additional optional fields supply statistical and other information.
40686 Although not required, they are extremely useful for users monitoring
40687 the progress of a trace run. If a trace has stopped, and these
40688 numbers are reported, they must reflect the state of the just-stopped
40693 @item tframes:@var{n}
40694 The number of trace frames in the buffer.
40696 @item tcreated:@var{n}
40697 The total number of trace frames created during the run. This may
40698 be larger than the trace frame count, if the buffer is circular.
40700 @item tsize:@var{n}
40701 The total size of the trace buffer, in bytes.
40703 @item tfree:@var{n}
40704 The number of bytes still unused in the buffer.
40706 @item circular:@var{n}
40707 The value of the circular trace buffer flag. @code{1} means that the
40708 trace buffer is circular and old trace frames will be discarded if
40709 necessary to make room, @code{0} means that the trace buffer is linear
40712 @item disconn:@var{n}
40713 The value of the disconnected tracing flag. @code{1} means that
40714 tracing will continue after @value{GDBN} disconnects, @code{0} means
40715 that the trace run will stop.
40719 @item qTP:@var{tp}:@var{addr}
40720 @cindex tracepoint status, remote request
40721 @cindex @samp{qTP} packet
40722 Ask the stub for the current state of tracepoint number @var{tp} at
40723 address @var{addr}.
40727 @item V@var{hits}:@var{usage}
40728 The tracepoint has been hit @var{hits} times so far during the trace
40729 run, and accounts for @var{usage} in the trace buffer. Note that
40730 @code{while-stepping} steps are not counted as separate hits, but the
40731 steps' space consumption is added into the usage number.
40735 @item qTV:@var{var}
40736 @cindex trace state variable value, remote request
40737 @cindex @samp{qTV} packet
40738 Ask the stub for the value of the trace state variable number @var{var}.
40743 The value of the variable is @var{value}. This will be the current
40744 value of the variable if the user is examining a running target, or a
40745 saved value if the variable was collected in the trace frame that the
40746 user is looking at. Note that multiple requests may result in
40747 different reply values, such as when requesting values while the
40748 program is running.
40751 The value of the variable is unknown. This would occur, for example,
40752 if the user is examining a trace frame in which the requested variable
40757 @cindex @samp{qTfP} packet
40759 @cindex @samp{qTsP} packet
40760 These packets request data about tracepoints that are being used by
40761 the target. @value{GDBN} sends @code{qTfP} to get the first piece
40762 of data, and multiple @code{qTsP} to get additional pieces. Replies
40763 to these packets generally take the form of the @code{QTDP} packets
40764 that define tracepoints. (FIXME add detailed syntax)
40767 @cindex @samp{qTfV} packet
40769 @cindex @samp{qTsV} packet
40770 These packets request data about trace state variables that are on the
40771 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
40772 and multiple @code{qTsV} to get additional variables. Replies to
40773 these packets follow the syntax of the @code{QTDV} packets that define
40774 trace state variables.
40780 @cindex @samp{qTfSTM} packet
40781 @cindex @samp{qTsSTM} packet
40782 These packets request data about static tracepoint markers that exist
40783 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
40784 first piece of data, and multiple @code{qTsSTM} to get additional
40785 pieces. Replies to these packets take the following form:
40789 @item m @var{address}:@var{id}:@var{extra}
40791 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
40792 a comma-separated list of markers
40794 (lower case letter @samp{L}) denotes end of list.
40796 An error occurred. @var{nn} are hex digits.
40798 An empty reply indicates that the request is not supported by the
40802 @var{address} is encoded in hex.
40803 @var{id} and @var{extra} are strings encoded in hex.
40805 In response to each query, the target will reply with a list of one or
40806 more markers, separated by commas. @value{GDBN} will respond to each
40807 reply with a request for more markers (using the @samp{qs} form of the
40808 query), until the target responds with @samp{l} (lower-case ell, for
40811 @item qTSTMat:@var{address}
40813 @cindex @samp{qTSTMat} packet
40814 This packets requests data about static tracepoint markers in the
40815 target program at @var{address}. Replies to this packet follow the
40816 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
40817 tracepoint markers.
40819 @item QTSave:@var{filename}
40820 @cindex @samp{QTSave} packet
40821 This packet directs the target to save trace data to the file name
40822 @var{filename} in the target's filesystem. @var{filename} is encoded
40823 as a hex string; the interpretation of the file name (relative vs
40824 absolute, wild cards, etc) is up to the target.
40826 @item qTBuffer:@var{offset},@var{len}
40827 @cindex @samp{qTBuffer} packet
40828 Return up to @var{len} bytes of the current contents of trace buffer,
40829 starting at @var{offset}. The trace buffer is treated as if it were
40830 a contiguous collection of traceframes, as per the trace file format.
40831 The reply consists as many hex-encoded bytes as the target can deliver
40832 in a packet; it is not an error to return fewer than were asked for.
40833 A reply consisting of just @code{l} indicates that no bytes are
40836 @item QTBuffer:circular:@var{value}
40837 This packet directs the target to use a circular trace buffer if
40838 @var{value} is 1, or a linear buffer if the value is 0.
40840 @item QTBuffer:size:@var{size}
40841 @anchor{QTBuffer-size}
40842 @cindex @samp{QTBuffer size} packet
40843 This packet directs the target to make the trace buffer be of size
40844 @var{size} if possible. A value of @code{-1} tells the target to
40845 use whatever size it prefers.
40847 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
40848 @cindex @samp{QTNotes} packet
40849 This packet adds optional textual notes to the trace run. Allowable
40850 types include @code{user}, @code{notes}, and @code{tstop}, the
40851 @var{text} fields are arbitrary strings, hex-encoded.
40855 @subsection Relocate instruction reply packet
40856 When installing fast tracepoints in memory, the target may need to
40857 relocate the instruction currently at the tracepoint address to a
40858 different address in memory. For most instructions, a simple copy is
40859 enough, but, for example, call instructions that implicitly push the
40860 return address on the stack, and relative branches or other
40861 PC-relative instructions require offset adjustment, so that the effect
40862 of executing the instruction at a different address is the same as if
40863 it had executed in the original location.
40865 In response to several of the tracepoint packets, the target may also
40866 respond with a number of intermediate @samp{qRelocInsn} request
40867 packets before the final result packet, to have @value{GDBN} handle
40868 this relocation operation. If a packet supports this mechanism, its
40869 documentation will explicitly say so. See for example the above
40870 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
40871 format of the request is:
40874 @item qRelocInsn:@var{from};@var{to}
40876 This requests @value{GDBN} to copy instruction at address @var{from}
40877 to address @var{to}, possibly adjusted so that executing the
40878 instruction at @var{to} has the same effect as executing it at
40879 @var{from}. @value{GDBN} writes the adjusted instruction to target
40880 memory starting at @var{to}.
40885 @item qRelocInsn:@var{adjusted_size}
40886 Informs the stub the relocation is complete. @var{adjusted_size} is
40887 the length in bytes of resulting relocated instruction sequence.
40889 A badly formed request was detected, or an error was encountered while
40890 relocating the instruction.
40893 @node Host I/O Packets
40894 @section Host I/O Packets
40895 @cindex Host I/O, remote protocol
40896 @cindex file transfer, remote protocol
40898 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
40899 operations on the far side of a remote link. For example, Host I/O is
40900 used to upload and download files to a remote target with its own
40901 filesystem. Host I/O uses the same constant values and data structure
40902 layout as the target-initiated File-I/O protocol. However, the
40903 Host I/O packets are structured differently. The target-initiated
40904 protocol relies on target memory to store parameters and buffers.
40905 Host I/O requests are initiated by @value{GDBN}, and the
40906 target's memory is not involved. @xref{File-I/O Remote Protocol
40907 Extension}, for more details on the target-initiated protocol.
40909 The Host I/O request packets all encode a single operation along with
40910 its arguments. They have this format:
40914 @item vFile:@var{operation}: @var{parameter}@dots{}
40915 @var{operation} is the name of the particular request; the target
40916 should compare the entire packet name up to the second colon when checking
40917 for a supported operation. The format of @var{parameter} depends on
40918 the operation. Numbers are always passed in hexadecimal. Negative
40919 numbers have an explicit minus sign (i.e.@: two's complement is not
40920 used). Strings (e.g.@: filenames) are encoded as a series of
40921 hexadecimal bytes. The last argument to a system call may be a
40922 buffer of escaped binary data (@pxref{Binary Data}).
40926 The valid responses to Host I/O packets are:
40930 @item F @var{result} [, @var{errno}] [; @var{attachment}]
40931 @var{result} is the integer value returned by this operation, usually
40932 non-negative for success and -1 for errors. If an error has occured,
40933 @var{errno} will be included in the result. @var{errno} will have a
40934 value defined by the File-I/O protocol (@pxref{Errno Values}). For
40935 operations which return data, @var{attachment} supplies the data as a
40936 binary buffer. Binary buffers in response packets are escaped in the
40937 normal way (@pxref{Binary Data}). See the individual packet
40938 documentation for the interpretation of @var{result} and
40942 An empty response indicates that this operation is not recognized.
40946 These are the supported Host I/O operations:
40949 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
40950 Open a file at @var{pathname} and return a file descriptor for it, or
40951 return -1 if an error occurs. @var{pathname} is a string,
40952 @var{flags} is an integer indicating a mask of open flags
40953 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
40954 of mode bits to use if the file is created (@pxref{mode_t Values}).
40955 @xref{open}, for details of the open flags and mode values.
40957 @item vFile:close: @var{fd}
40958 Close the open file corresponding to @var{fd} and return 0, or
40959 -1 if an error occurs.
40961 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
40962 Read data from the open file corresponding to @var{fd}. Up to
40963 @var{count} bytes will be read from the file, starting at @var{offset}
40964 relative to the start of the file. The target may read fewer bytes;
40965 common reasons include packet size limits and an end-of-file
40966 condition. The number of bytes read is returned. Zero should only be
40967 returned for a successful read at the end of the file, or if
40968 @var{count} was zero.
40970 The data read should be returned as a binary attachment on success.
40971 If zero bytes were read, the response should include an empty binary
40972 attachment (i.e.@: a trailing semicolon). The return value is the
40973 number of target bytes read; the binary attachment may be longer if
40974 some characters were escaped.
40976 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
40977 Write @var{data} (a binary buffer) to the open file corresponding
40978 to @var{fd}. Start the write at @var{offset} from the start of the
40979 file. Unlike many @code{write} system calls, there is no
40980 separate @var{count} argument; the length of @var{data} in the
40981 packet is used. @samp{vFile:write} returns the number of bytes written,
40982 which may be shorter than the length of @var{data}, or -1 if an
40985 @item vFile:unlink: @var{pathname}
40986 Delete the file at @var{pathname} on the target. Return 0,
40987 or -1 if an error occurs. @var{pathname} is a string.
40989 @item vFile:readlink: @var{filename}
40990 Read value of symbolic link @var{filename} on the target. Return
40991 the number of bytes read, or -1 if an error occurs.
40993 The data read should be returned as a binary attachment on success.
40994 If zero bytes were read, the response should include an empty binary
40995 attachment (i.e.@: a trailing semicolon). The return value is the
40996 number of target bytes read; the binary attachment may be longer if
40997 some characters were escaped.
41002 @section Interrupts
41003 @cindex interrupts (remote protocol)
41005 When a program on the remote target is running, @value{GDBN} may
41006 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
41007 a @code{BREAK} followed by @code{g},
41008 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
41010 The precise meaning of @code{BREAK} is defined by the transport
41011 mechanism and may, in fact, be undefined. @value{GDBN} does not
41012 currently define a @code{BREAK} mechanism for any of the network
41013 interfaces except for TCP, in which case @value{GDBN} sends the
41014 @code{telnet} BREAK sequence.
41016 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
41017 transport mechanisms. It is represented by sending the single byte
41018 @code{0x03} without any of the usual packet overhead described in
41019 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
41020 transmitted as part of a packet, it is considered to be packet data
41021 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
41022 (@pxref{X packet}), used for binary downloads, may include an unescaped
41023 @code{0x03} as part of its packet.
41025 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
41026 When Linux kernel receives this sequence from serial port,
41027 it stops execution and connects to gdb.
41029 Stubs are not required to recognize these interrupt mechanisms and the
41030 precise meaning associated with receipt of the interrupt is
41031 implementation defined. If the target supports debugging of multiple
41032 threads and/or processes, it should attempt to interrupt all
41033 currently-executing threads and processes.
41034 If the stub is successful at interrupting the
41035 running program, it should send one of the stop
41036 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
41037 of successfully stopping the program in all-stop mode, and a stop reply
41038 for each stopped thread in non-stop mode.
41039 Interrupts received while the
41040 program is stopped are discarded.
41042 @node Notification Packets
41043 @section Notification Packets
41044 @cindex notification packets
41045 @cindex packets, notification
41047 The @value{GDBN} remote serial protocol includes @dfn{notifications},
41048 packets that require no acknowledgment. Both the GDB and the stub
41049 may send notifications (although the only notifications defined at
41050 present are sent by the stub). Notifications carry information
41051 without incurring the round-trip latency of an acknowledgment, and so
41052 are useful for low-impact communications where occasional packet loss
41055 A notification packet has the form @samp{% @var{data} #
41056 @var{checksum}}, where @var{data} is the content of the notification,
41057 and @var{checksum} is a checksum of @var{data}, computed and formatted
41058 as for ordinary @value{GDBN} packets. A notification's @var{data}
41059 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
41060 receiving a notification, the recipient sends no @samp{+} or @samp{-}
41061 to acknowledge the notification's receipt or to report its corruption.
41063 Every notification's @var{data} begins with a name, which contains no
41064 colon characters, followed by a colon character.
41066 Recipients should silently ignore corrupted notifications and
41067 notifications they do not understand. Recipients should restart
41068 timeout periods on receipt of a well-formed notification, whether or
41069 not they understand it.
41071 Senders should only send the notifications described here when this
41072 protocol description specifies that they are permitted. In the
41073 future, we may extend the protocol to permit existing notifications in
41074 new contexts; this rule helps older senders avoid confusing newer
41077 (Older versions of @value{GDBN} ignore bytes received until they see
41078 the @samp{$} byte that begins an ordinary packet, so new stubs may
41079 transmit notifications without fear of confusing older clients. There
41080 are no notifications defined for @value{GDBN} to send at the moment, but we
41081 assume that most older stubs would ignore them, as well.)
41083 Each notification is comprised of three parts:
41085 @item @var{name}:@var{event}
41086 The notification packet is sent by the side that initiates the
41087 exchange (currently, only the stub does that), with @var{event}
41088 carrying the specific information about the notification.
41089 @var{name} is the name of the notification.
41091 The acknowledge sent by the other side, usually @value{GDBN}, to
41092 acknowledge the exchange and request the event.
41095 The purpose of an asynchronous notification mechanism is to report to
41096 @value{GDBN} that something interesting happened in the remote stub.
41098 The remote stub may send notification @var{name}:@var{event}
41099 at any time, but @value{GDBN} acknowledges the notification when
41100 appropriate. The notification event is pending before @value{GDBN}
41101 acknowledges. Only one notification at a time may be pending; if
41102 additional events occur before @value{GDBN} has acknowledged the
41103 previous notification, they must be queued by the stub for later
41104 synchronous transmission in response to @var{ack} packets from
41105 @value{GDBN}. Because the notification mechanism is unreliable,
41106 the stub is permitted to resend a notification if it believes
41107 @value{GDBN} may not have received it.
41109 Specifically, notifications may appear when @value{GDBN} is not
41110 otherwise reading input from the stub, or when @value{GDBN} is
41111 expecting to read a normal synchronous response or a
41112 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
41113 Notification packets are distinct from any other communication from
41114 the stub so there is no ambiguity.
41116 After receiving a notification, @value{GDBN} shall acknowledge it by
41117 sending a @var{ack} packet as a regular, synchronous request to the
41118 stub. Such acknowledgment is not required to happen immediately, as
41119 @value{GDBN} is permitted to send other, unrelated packets to the
41120 stub first, which the stub should process normally.
41122 Upon receiving a @var{ack} packet, if the stub has other queued
41123 events to report to @value{GDBN}, it shall respond by sending a
41124 normal @var{event}. @value{GDBN} shall then send another @var{ack}
41125 packet to solicit further responses; again, it is permitted to send
41126 other, unrelated packets as well which the stub should process
41129 If the stub receives a @var{ack} packet and there are no additional
41130 @var{event} to report, the stub shall return an @samp{OK} response.
41131 At this point, @value{GDBN} has finished processing a notification
41132 and the stub has completed sending any queued events. @value{GDBN}
41133 won't accept any new notifications until the final @samp{OK} is
41134 received . If further notification events occur, the stub shall send
41135 a new notification, @value{GDBN} shall accept the notification, and
41136 the process shall be repeated.
41138 The process of asynchronous notification can be illustrated by the
41141 <- @code{%%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
41144 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
41146 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
41151 The following notifications are defined:
41152 @multitable @columnfractions 0.12 0.12 0.38 0.38
41161 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
41162 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
41163 for information on how these notifications are acknowledged by
41165 @tab Report an asynchronous stop event in non-stop mode.
41169 @node Remote Non-Stop
41170 @section Remote Protocol Support for Non-Stop Mode
41172 @value{GDBN}'s remote protocol supports non-stop debugging of
41173 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
41174 supports non-stop mode, it should report that to @value{GDBN} by including
41175 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
41177 @value{GDBN} typically sends a @samp{QNonStop} packet only when
41178 establishing a new connection with the stub. Entering non-stop mode
41179 does not alter the state of any currently-running threads, but targets
41180 must stop all threads in any already-attached processes when entering
41181 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
41182 probe the target state after a mode change.
41184 In non-stop mode, when an attached process encounters an event that
41185 would otherwise be reported with a stop reply, it uses the
41186 asynchronous notification mechanism (@pxref{Notification Packets}) to
41187 inform @value{GDBN}. In contrast to all-stop mode, where all threads
41188 in all processes are stopped when a stop reply is sent, in non-stop
41189 mode only the thread reporting the stop event is stopped. That is,
41190 when reporting a @samp{S} or @samp{T} response to indicate completion
41191 of a step operation, hitting a breakpoint, or a fault, only the
41192 affected thread is stopped; any other still-running threads continue
41193 to run. When reporting a @samp{W} or @samp{X} response, all running
41194 threads belonging to other attached processes continue to run.
41196 In non-stop mode, the target shall respond to the @samp{?} packet as
41197 follows. First, any incomplete stop reply notification/@samp{vStopped}
41198 sequence in progress is abandoned. The target must begin a new
41199 sequence reporting stop events for all stopped threads, whether or not
41200 it has previously reported those events to @value{GDBN}. The first
41201 stop reply is sent as a synchronous reply to the @samp{?} packet, and
41202 subsequent stop replies are sent as responses to @samp{vStopped} packets
41203 using the mechanism described above. The target must not send
41204 asynchronous stop reply notifications until the sequence is complete.
41205 If all threads are running when the target receives the @samp{?} packet,
41206 or if the target is not attached to any process, it shall respond
41209 @node Packet Acknowledgment
41210 @section Packet Acknowledgment
41212 @cindex acknowledgment, for @value{GDBN} remote
41213 @cindex packet acknowledgment, for @value{GDBN} remote
41214 By default, when either the host or the target machine receives a packet,
41215 the first response expected is an acknowledgment: either @samp{+} (to indicate
41216 the package was received correctly) or @samp{-} (to request retransmission).
41217 This mechanism allows the @value{GDBN} remote protocol to operate over
41218 unreliable transport mechanisms, such as a serial line.
41220 In cases where the transport mechanism is itself reliable (such as a pipe or
41221 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
41222 It may be desirable to disable them in that case to reduce communication
41223 overhead, or for other reasons. This can be accomplished by means of the
41224 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
41226 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
41227 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
41228 and response format still includes the normal checksum, as described in
41229 @ref{Overview}, but the checksum may be ignored by the receiver.
41231 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
41232 no-acknowledgment mode, it should report that to @value{GDBN}
41233 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
41234 @pxref{qSupported}.
41235 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
41236 disabled via the @code{set remote noack-packet off} command
41237 (@pxref{Remote Configuration}),
41238 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
41239 Only then may the stub actually turn off packet acknowledgments.
41240 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
41241 response, which can be safely ignored by the stub.
41243 Note that @code{set remote noack-packet} command only affects negotiation
41244 between @value{GDBN} and the stub when subsequent connections are made;
41245 it does not affect the protocol acknowledgment state for any current
41247 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
41248 new connection is established,
41249 there is also no protocol request to re-enable the acknowledgments
41250 for the current connection, once disabled.
41255 Example sequence of a target being re-started. Notice how the restart
41256 does not get any direct output:
41261 @emph{target restarts}
41264 <- @code{T001:1234123412341234}
41268 Example sequence of a target being stepped by a single instruction:
41271 -> @code{G1445@dots{}}
41276 <- @code{T001:1234123412341234}
41280 <- @code{1455@dots{}}
41284 @node File-I/O Remote Protocol Extension
41285 @section File-I/O Remote Protocol Extension
41286 @cindex File-I/O remote protocol extension
41289 * File-I/O Overview::
41290 * Protocol Basics::
41291 * The F Request Packet::
41292 * The F Reply Packet::
41293 * The Ctrl-C Message::
41295 * List of Supported Calls::
41296 * Protocol-specific Representation of Datatypes::
41298 * File-I/O Examples::
41301 @node File-I/O Overview
41302 @subsection File-I/O Overview
41303 @cindex file-i/o overview
41305 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
41306 target to use the host's file system and console I/O to perform various
41307 system calls. System calls on the target system are translated into a
41308 remote protocol packet to the host system, which then performs the needed
41309 actions and returns a response packet to the target system.
41310 This simulates file system operations even on targets that lack file systems.
41312 The protocol is defined to be independent of both the host and target systems.
41313 It uses its own internal representation of datatypes and values. Both
41314 @value{GDBN} and the target's @value{GDBN} stub are responsible for
41315 translating the system-dependent value representations into the internal
41316 protocol representations when data is transmitted.
41318 The communication is synchronous. A system call is possible only when
41319 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
41320 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
41321 the target is stopped to allow deterministic access to the target's
41322 memory. Therefore File-I/O is not interruptible by target signals. On
41323 the other hand, it is possible to interrupt File-I/O by a user interrupt
41324 (@samp{Ctrl-C}) within @value{GDBN}.
41326 The target's request to perform a host system call does not finish
41327 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
41328 after finishing the system call, the target returns to continuing the
41329 previous activity (continue, step). No additional continue or step
41330 request from @value{GDBN} is required.
41333 (@value{GDBP}) continue
41334 <- target requests 'system call X'
41335 target is stopped, @value{GDBN} executes system call
41336 -> @value{GDBN} returns result
41337 ... target continues, @value{GDBN} returns to wait for the target
41338 <- target hits breakpoint and sends a Txx packet
41341 The protocol only supports I/O on the console and to regular files on
41342 the host file system. Character or block special devices, pipes,
41343 named pipes, sockets or any other communication method on the host
41344 system are not supported by this protocol.
41346 File I/O is not supported in non-stop mode.
41348 @node Protocol Basics
41349 @subsection Protocol Basics
41350 @cindex protocol basics, file-i/o
41352 The File-I/O protocol uses the @code{F} packet as the request as well
41353 as reply packet. Since a File-I/O system call can only occur when
41354 @value{GDBN} is waiting for a response from the continuing or stepping target,
41355 the File-I/O request is a reply that @value{GDBN} has to expect as a result
41356 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
41357 This @code{F} packet contains all information needed to allow @value{GDBN}
41358 to call the appropriate host system call:
41362 A unique identifier for the requested system call.
41365 All parameters to the system call. Pointers are given as addresses
41366 in the target memory address space. Pointers to strings are given as
41367 pointer/length pair. Numerical values are given as they are.
41368 Numerical control flags are given in a protocol-specific representation.
41372 At this point, @value{GDBN} has to perform the following actions.
41376 If the parameters include pointer values to data needed as input to a
41377 system call, @value{GDBN} requests this data from the target with a
41378 standard @code{m} packet request. This additional communication has to be
41379 expected by the target implementation and is handled as any other @code{m}
41383 @value{GDBN} translates all value from protocol representation to host
41384 representation as needed. Datatypes are coerced into the host types.
41387 @value{GDBN} calls the system call.
41390 It then coerces datatypes back to protocol representation.
41393 If the system call is expected to return data in buffer space specified
41394 by pointer parameters to the call, the data is transmitted to the
41395 target using a @code{M} or @code{X} packet. This packet has to be expected
41396 by the target implementation and is handled as any other @code{M} or @code{X}
41401 Eventually @value{GDBN} replies with another @code{F} packet which contains all
41402 necessary information for the target to continue. This at least contains
41409 @code{errno}, if has been changed by the system call.
41416 After having done the needed type and value coercion, the target continues
41417 the latest continue or step action.
41419 @node The F Request Packet
41420 @subsection The @code{F} Request Packet
41421 @cindex file-i/o request packet
41422 @cindex @code{F} request packet
41424 The @code{F} request packet has the following format:
41427 @item F@var{call-id},@var{parameter@dots{}}
41429 @var{call-id} is the identifier to indicate the host system call to be called.
41430 This is just the name of the function.
41432 @var{parameter@dots{}} are the parameters to the system call.
41433 Parameters are hexadecimal integer values, either the actual values in case
41434 of scalar datatypes, pointers to target buffer space in case of compound
41435 datatypes and unspecified memory areas, or pointer/length pairs in case
41436 of string parameters. These are appended to the @var{call-id} as a
41437 comma-delimited list. All values are transmitted in ASCII
41438 string representation, pointer/length pairs separated by a slash.
41444 @node The F Reply Packet
41445 @subsection The @code{F} Reply Packet
41446 @cindex file-i/o reply packet
41447 @cindex @code{F} reply packet
41449 The @code{F} reply packet has the following format:
41453 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
41455 @var{retcode} is the return code of the system call as hexadecimal value.
41457 @var{errno} is the @code{errno} set by the call, in protocol-specific
41459 This parameter can be omitted if the call was successful.
41461 @var{Ctrl-C flag} is only sent if the user requested a break. In this
41462 case, @var{errno} must be sent as well, even if the call was successful.
41463 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
41470 or, if the call was interrupted before the host call has been performed:
41477 assuming 4 is the protocol-specific representation of @code{EINTR}.
41482 @node The Ctrl-C Message
41483 @subsection The @samp{Ctrl-C} Message
41484 @cindex ctrl-c message, in file-i/o protocol
41486 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
41487 reply packet (@pxref{The F Reply Packet}),
41488 the target should behave as if it had
41489 gotten a break message. The meaning for the target is ``system call
41490 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
41491 (as with a break message) and return to @value{GDBN} with a @code{T02}
41494 It's important for the target to know in which
41495 state the system call was interrupted. There are two possible cases:
41499 The system call hasn't been performed on the host yet.
41502 The system call on the host has been finished.
41506 These two states can be distinguished by the target by the value of the
41507 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
41508 call hasn't been performed. This is equivalent to the @code{EINTR} handling
41509 on POSIX systems. In any other case, the target may presume that the
41510 system call has been finished --- successfully or not --- and should behave
41511 as if the break message arrived right after the system call.
41513 @value{GDBN} must behave reliably. If the system call has not been called
41514 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
41515 @code{errno} in the packet. If the system call on the host has been finished
41516 before the user requests a break, the full action must be finished by
41517 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
41518 The @code{F} packet may only be sent when either nothing has happened
41519 or the full action has been completed.
41522 @subsection Console I/O
41523 @cindex console i/o as part of file-i/o
41525 By default and if not explicitly closed by the target system, the file
41526 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
41527 on the @value{GDBN} console is handled as any other file output operation
41528 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
41529 by @value{GDBN} so that after the target read request from file descriptor
41530 0 all following typing is buffered until either one of the following
41535 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
41537 system call is treated as finished.
41540 The user presses @key{RET}. This is treated as end of input with a trailing
41544 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
41545 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
41549 If the user has typed more characters than fit in the buffer given to
41550 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
41551 either another @code{read(0, @dots{})} is requested by the target, or debugging
41552 is stopped at the user's request.
41555 @node List of Supported Calls
41556 @subsection List of Supported Calls
41557 @cindex list of supported file-i/o calls
41574 @unnumberedsubsubsec open
41575 @cindex open, file-i/o system call
41580 int open(const char *pathname, int flags);
41581 int open(const char *pathname, int flags, mode_t mode);
41585 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
41588 @var{flags} is the bitwise @code{OR} of the following values:
41592 If the file does not exist it will be created. The host
41593 rules apply as far as file ownership and time stamps
41597 When used with @code{O_CREAT}, if the file already exists it is
41598 an error and open() fails.
41601 If the file already exists and the open mode allows
41602 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
41603 truncated to zero length.
41606 The file is opened in append mode.
41609 The file is opened for reading only.
41612 The file is opened for writing only.
41615 The file is opened for reading and writing.
41619 Other bits are silently ignored.
41623 @var{mode} is the bitwise @code{OR} of the following values:
41627 User has read permission.
41630 User has write permission.
41633 Group has read permission.
41636 Group has write permission.
41639 Others have read permission.
41642 Others have write permission.
41646 Other bits are silently ignored.
41649 @item Return value:
41650 @code{open} returns the new file descriptor or -1 if an error
41657 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
41660 @var{pathname} refers to a directory.
41663 The requested access is not allowed.
41666 @var{pathname} was too long.
41669 A directory component in @var{pathname} does not exist.
41672 @var{pathname} refers to a device, pipe, named pipe or socket.
41675 @var{pathname} refers to a file on a read-only filesystem and
41676 write access was requested.
41679 @var{pathname} is an invalid pointer value.
41682 No space on device to create the file.
41685 The process already has the maximum number of files open.
41688 The limit on the total number of files open on the system
41692 The call was interrupted by the user.
41698 @unnumberedsubsubsec close
41699 @cindex close, file-i/o system call
41708 @samp{Fclose,@var{fd}}
41710 @item Return value:
41711 @code{close} returns zero on success, or -1 if an error occurred.
41717 @var{fd} isn't a valid open file descriptor.
41720 The call was interrupted by the user.
41726 @unnumberedsubsubsec read
41727 @cindex read, file-i/o system call
41732 int read(int fd, void *buf, unsigned int count);
41736 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
41738 @item Return value:
41739 On success, the number of bytes read is returned.
41740 Zero indicates end of file. If count is zero, read
41741 returns zero as well. On error, -1 is returned.
41747 @var{fd} is not a valid file descriptor or is not open for
41751 @var{bufptr} is an invalid pointer value.
41754 The call was interrupted by the user.
41760 @unnumberedsubsubsec write
41761 @cindex write, file-i/o system call
41766 int write(int fd, const void *buf, unsigned int count);
41770 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
41772 @item Return value:
41773 On success, the number of bytes written are returned.
41774 Zero indicates nothing was written. On error, -1
41781 @var{fd} is not a valid file descriptor or is not open for
41785 @var{bufptr} is an invalid pointer value.
41788 An attempt was made to write a file that exceeds the
41789 host-specific maximum file size allowed.
41792 No space on device to write the data.
41795 The call was interrupted by the user.
41801 @unnumberedsubsubsec lseek
41802 @cindex lseek, file-i/o system call
41807 long lseek (int fd, long offset, int flag);
41811 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
41813 @var{flag} is one of:
41817 The offset is set to @var{offset} bytes.
41820 The offset is set to its current location plus @var{offset}
41824 The offset is set to the size of the file plus @var{offset}
41828 @item Return value:
41829 On success, the resulting unsigned offset in bytes from
41830 the beginning of the file is returned. Otherwise, a
41831 value of -1 is returned.
41837 @var{fd} is not a valid open file descriptor.
41840 @var{fd} is associated with the @value{GDBN} console.
41843 @var{flag} is not a proper value.
41846 The call was interrupted by the user.
41852 @unnumberedsubsubsec rename
41853 @cindex rename, file-i/o system call
41858 int rename(const char *oldpath, const char *newpath);
41862 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
41864 @item Return value:
41865 On success, zero is returned. On error, -1 is returned.
41871 @var{newpath} is an existing directory, but @var{oldpath} is not a
41875 @var{newpath} is a non-empty directory.
41878 @var{oldpath} or @var{newpath} is a directory that is in use by some
41882 An attempt was made to make a directory a subdirectory
41886 A component used as a directory in @var{oldpath} or new
41887 path is not a directory. Or @var{oldpath} is a directory
41888 and @var{newpath} exists but is not a directory.
41891 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
41894 No access to the file or the path of the file.
41898 @var{oldpath} or @var{newpath} was too long.
41901 A directory component in @var{oldpath} or @var{newpath} does not exist.
41904 The file is on a read-only filesystem.
41907 The device containing the file has no room for the new
41911 The call was interrupted by the user.
41917 @unnumberedsubsubsec unlink
41918 @cindex unlink, file-i/o system call
41923 int unlink(const char *pathname);
41927 @samp{Funlink,@var{pathnameptr}/@var{len}}
41929 @item Return value:
41930 On success, zero is returned. On error, -1 is returned.
41936 No access to the file or the path of the file.
41939 The system does not allow unlinking of directories.
41942 The file @var{pathname} cannot be unlinked because it's
41943 being used by another process.
41946 @var{pathnameptr} is an invalid pointer value.
41949 @var{pathname} was too long.
41952 A directory component in @var{pathname} does not exist.
41955 A component of the path is not a directory.
41958 The file is on a read-only filesystem.
41961 The call was interrupted by the user.
41967 @unnumberedsubsubsec stat/fstat
41968 @cindex fstat, file-i/o system call
41969 @cindex stat, file-i/o system call
41974 int stat(const char *pathname, struct stat *buf);
41975 int fstat(int fd, struct stat *buf);
41979 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
41980 @samp{Ffstat,@var{fd},@var{bufptr}}
41982 @item Return value:
41983 On success, zero is returned. On error, -1 is returned.
41989 @var{fd} is not a valid open file.
41992 A directory component in @var{pathname} does not exist or the
41993 path is an empty string.
41996 A component of the path is not a directory.
41999 @var{pathnameptr} is an invalid pointer value.
42002 No access to the file or the path of the file.
42005 @var{pathname} was too long.
42008 The call was interrupted by the user.
42014 @unnumberedsubsubsec gettimeofday
42015 @cindex gettimeofday, file-i/o system call
42020 int gettimeofday(struct timeval *tv, void *tz);
42024 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
42026 @item Return value:
42027 On success, 0 is returned, -1 otherwise.
42033 @var{tz} is a non-NULL pointer.
42036 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
42042 @unnumberedsubsubsec isatty
42043 @cindex isatty, file-i/o system call
42048 int isatty(int fd);
42052 @samp{Fisatty,@var{fd}}
42054 @item Return value:
42055 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
42061 The call was interrupted by the user.
42066 Note that the @code{isatty} call is treated as a special case: it returns
42067 1 to the target if the file descriptor is attached
42068 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
42069 would require implementing @code{ioctl} and would be more complex than
42074 @unnumberedsubsubsec system
42075 @cindex system, file-i/o system call
42080 int system(const char *command);
42084 @samp{Fsystem,@var{commandptr}/@var{len}}
42086 @item Return value:
42087 If @var{len} is zero, the return value indicates whether a shell is
42088 available. A zero return value indicates a shell is not available.
42089 For non-zero @var{len}, the value returned is -1 on error and the
42090 return status of the command otherwise. Only the exit status of the
42091 command is returned, which is extracted from the host's @code{system}
42092 return value by calling @code{WEXITSTATUS(retval)}. In case
42093 @file{/bin/sh} could not be executed, 127 is returned.
42099 The call was interrupted by the user.
42104 @value{GDBN} takes over the full task of calling the necessary host calls
42105 to perform the @code{system} call. The return value of @code{system} on
42106 the host is simplified before it's returned
42107 to the target. Any termination signal information from the child process
42108 is discarded, and the return value consists
42109 entirely of the exit status of the called command.
42111 Due to security concerns, the @code{system} call is by default refused
42112 by @value{GDBN}. The user has to allow this call explicitly with the
42113 @code{set remote system-call-allowed 1} command.
42116 @item set remote system-call-allowed
42117 @kindex set remote system-call-allowed
42118 Control whether to allow the @code{system} calls in the File I/O
42119 protocol for the remote target. The default is zero (disabled).
42121 @item show remote system-call-allowed
42122 @kindex show remote system-call-allowed
42123 Show whether the @code{system} calls are allowed in the File I/O
42127 @node Protocol-specific Representation of Datatypes
42128 @subsection Protocol-specific Representation of Datatypes
42129 @cindex protocol-specific representation of datatypes, in file-i/o protocol
42132 * Integral Datatypes::
42134 * Memory Transfer::
42139 @node Integral Datatypes
42140 @unnumberedsubsubsec Integral Datatypes
42141 @cindex integral datatypes, in file-i/o protocol
42143 The integral datatypes used in the system calls are @code{int},
42144 @code{unsigned int}, @code{long}, @code{unsigned long},
42145 @code{mode_t}, and @code{time_t}.
42147 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
42148 implemented as 32 bit values in this protocol.
42150 @code{long} and @code{unsigned long} are implemented as 64 bit types.
42152 @xref{Limits}, for corresponding MIN and MAX values (similar to those
42153 in @file{limits.h}) to allow range checking on host and target.
42155 @code{time_t} datatypes are defined as seconds since the Epoch.
42157 All integral datatypes transferred as part of a memory read or write of a
42158 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
42161 @node Pointer Values
42162 @unnumberedsubsubsec Pointer Values
42163 @cindex pointer values, in file-i/o protocol
42165 Pointers to target data are transmitted as they are. An exception
42166 is made for pointers to buffers for which the length isn't
42167 transmitted as part of the function call, namely strings. Strings
42168 are transmitted as a pointer/length pair, both as hex values, e.g.@:
42175 which is a pointer to data of length 18 bytes at position 0x1aaf.
42176 The length is defined as the full string length in bytes, including
42177 the trailing null byte. For example, the string @code{"hello world"}
42178 at address 0x123456 is transmitted as
42184 @node Memory Transfer
42185 @unnumberedsubsubsec Memory Transfer
42186 @cindex memory transfer, in file-i/o protocol
42188 Structured data which is transferred using a memory read or write (for
42189 example, a @code{struct stat}) is expected to be in a protocol-specific format
42190 with all scalar multibyte datatypes being big endian. Translation to
42191 this representation needs to be done both by the target before the @code{F}
42192 packet is sent, and by @value{GDBN} before
42193 it transfers memory to the target. Transferred pointers to structured
42194 data should point to the already-coerced data at any time.
42198 @unnumberedsubsubsec struct stat
42199 @cindex struct stat, in file-i/o protocol
42201 The buffer of type @code{struct stat} used by the target and @value{GDBN}
42202 is defined as follows:
42206 unsigned int st_dev; /* device */
42207 unsigned int st_ino; /* inode */
42208 mode_t st_mode; /* protection */
42209 unsigned int st_nlink; /* number of hard links */
42210 unsigned int st_uid; /* user ID of owner */
42211 unsigned int st_gid; /* group ID of owner */
42212 unsigned int st_rdev; /* device type (if inode device) */
42213 unsigned long st_size; /* total size, in bytes */
42214 unsigned long st_blksize; /* blocksize for filesystem I/O */
42215 unsigned long st_blocks; /* number of blocks allocated */
42216 time_t st_atime; /* time of last access */
42217 time_t st_mtime; /* time of last modification */
42218 time_t st_ctime; /* time of last change */
42222 The integral datatypes conform to the definitions given in the
42223 appropriate section (see @ref{Integral Datatypes}, for details) so this
42224 structure is of size 64 bytes.
42226 The values of several fields have a restricted meaning and/or
42232 A value of 0 represents a file, 1 the console.
42235 No valid meaning for the target. Transmitted unchanged.
42238 Valid mode bits are described in @ref{Constants}. Any other
42239 bits have currently no meaning for the target.
42244 No valid meaning for the target. Transmitted unchanged.
42249 These values have a host and file system dependent
42250 accuracy. Especially on Windows hosts, the file system may not
42251 support exact timing values.
42254 The target gets a @code{struct stat} of the above representation and is
42255 responsible for coercing it to the target representation before
42258 Note that due to size differences between the host, target, and protocol
42259 representations of @code{struct stat} members, these members could eventually
42260 get truncated on the target.
42262 @node struct timeval
42263 @unnumberedsubsubsec struct timeval
42264 @cindex struct timeval, in file-i/o protocol
42266 The buffer of type @code{struct timeval} used by the File-I/O protocol
42267 is defined as follows:
42271 time_t tv_sec; /* second */
42272 long tv_usec; /* microsecond */
42276 The integral datatypes conform to the definitions given in the
42277 appropriate section (see @ref{Integral Datatypes}, for details) so this
42278 structure is of size 8 bytes.
42281 @subsection Constants
42282 @cindex constants, in file-i/o protocol
42284 The following values are used for the constants inside of the
42285 protocol. @value{GDBN} and target are responsible for translating these
42286 values before and after the call as needed.
42297 @unnumberedsubsubsec Open Flags
42298 @cindex open flags, in file-i/o protocol
42300 All values are given in hexadecimal representation.
42312 @node mode_t Values
42313 @unnumberedsubsubsec mode_t Values
42314 @cindex mode_t values, in file-i/o protocol
42316 All values are given in octal representation.
42333 @unnumberedsubsubsec Errno Values
42334 @cindex errno values, in file-i/o protocol
42336 All values are given in decimal representation.
42361 @code{EUNKNOWN} is used as a fallback error value if a host system returns
42362 any error value not in the list of supported error numbers.
42365 @unnumberedsubsubsec Lseek Flags
42366 @cindex lseek flags, in file-i/o protocol
42375 @unnumberedsubsubsec Limits
42376 @cindex limits, in file-i/o protocol
42378 All values are given in decimal representation.
42381 INT_MIN -2147483648
42383 UINT_MAX 4294967295
42384 LONG_MIN -9223372036854775808
42385 LONG_MAX 9223372036854775807
42386 ULONG_MAX 18446744073709551615
42389 @node File-I/O Examples
42390 @subsection File-I/O Examples
42391 @cindex file-i/o examples
42393 Example sequence of a write call, file descriptor 3, buffer is at target
42394 address 0x1234, 6 bytes should be written:
42397 <- @code{Fwrite,3,1234,6}
42398 @emph{request memory read from target}
42401 @emph{return "6 bytes written"}
42405 Example sequence of a read call, file descriptor 3, buffer is at target
42406 address 0x1234, 6 bytes should be read:
42409 <- @code{Fread,3,1234,6}
42410 @emph{request memory write to target}
42411 -> @code{X1234,6:XXXXXX}
42412 @emph{return "6 bytes read"}
42416 Example sequence of a read call, call fails on the host due to invalid
42417 file descriptor (@code{EBADF}):
42420 <- @code{Fread,3,1234,6}
42424 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
42428 <- @code{Fread,3,1234,6}
42433 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
42437 <- @code{Fread,3,1234,6}
42438 -> @code{X1234,6:XXXXXX}
42442 @node Library List Format
42443 @section Library List Format
42444 @cindex library list format, remote protocol
42446 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
42447 same process as your application to manage libraries. In this case,
42448 @value{GDBN} can use the loader's symbol table and normal memory
42449 operations to maintain a list of shared libraries. On other
42450 platforms, the operating system manages loaded libraries.
42451 @value{GDBN} can not retrieve the list of currently loaded libraries
42452 through memory operations, so it uses the @samp{qXfer:libraries:read}
42453 packet (@pxref{qXfer library list read}) instead. The remote stub
42454 queries the target's operating system and reports which libraries
42457 The @samp{qXfer:libraries:read} packet returns an XML document which
42458 lists loaded libraries and their offsets. Each library has an
42459 associated name and one or more segment or section base addresses,
42460 which report where the library was loaded in memory.
42462 For the common case of libraries that are fully linked binaries, the
42463 library should have a list of segments. If the target supports
42464 dynamic linking of a relocatable object file, its library XML element
42465 should instead include a list of allocated sections. The segment or
42466 section bases are start addresses, not relocation offsets; they do not
42467 depend on the library's link-time base addresses.
42469 @value{GDBN} must be linked with the Expat library to support XML
42470 library lists. @xref{Expat}.
42472 A simple memory map, with one loaded library relocated by a single
42473 offset, looks like this:
42477 <library name="/lib/libc.so.6">
42478 <segment address="0x10000000"/>
42483 Another simple memory map, with one loaded library with three
42484 allocated sections (.text, .data, .bss), looks like this:
42488 <library name="sharedlib.o">
42489 <section address="0x10000000"/>
42490 <section address="0x20000000"/>
42491 <section address="0x30000000"/>
42496 The format of a library list is described by this DTD:
42499 <!-- library-list: Root element with versioning -->
42500 <!ELEMENT library-list (library)*>
42501 <!ATTLIST library-list version CDATA #FIXED "1.0">
42502 <!ELEMENT library (segment*, section*)>
42503 <!ATTLIST library name CDATA #REQUIRED>
42504 <!ELEMENT segment EMPTY>
42505 <!ATTLIST segment address CDATA #REQUIRED>
42506 <!ELEMENT section EMPTY>
42507 <!ATTLIST section address CDATA #REQUIRED>
42510 In addition, segments and section descriptors cannot be mixed within a
42511 single library element, and you must supply at least one segment or
42512 section for each library.
42514 @node Library List Format for SVR4 Targets
42515 @section Library List Format for SVR4 Targets
42516 @cindex library list format, remote protocol
42518 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
42519 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
42520 shared libraries. Still a special library list provided by this packet is
42521 more efficient for the @value{GDBN} remote protocol.
42523 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
42524 loaded libraries and their SVR4 linker parameters. For each library on SVR4
42525 target, the following parameters are reported:
42529 @code{name}, the absolute file name from the @code{l_name} field of
42530 @code{struct link_map}.
42532 @code{lm} with address of @code{struct link_map} used for TLS
42533 (Thread Local Storage) access.
42535 @code{l_addr}, the displacement as read from the field @code{l_addr} of
42536 @code{struct link_map}. For prelinked libraries this is not an absolute
42537 memory address. It is a displacement of absolute memory address against
42538 address the file was prelinked to during the library load.
42540 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
42543 Additionally the single @code{main-lm} attribute specifies address of
42544 @code{struct link_map} used for the main executable. This parameter is used
42545 for TLS access and its presence is optional.
42547 @value{GDBN} must be linked with the Expat library to support XML
42548 SVR4 library lists. @xref{Expat}.
42550 A simple memory map, with two loaded libraries (which do not use prelink),
42554 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
42555 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
42557 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
42559 </library-list-svr>
42562 The format of an SVR4 library list is described by this DTD:
42565 <!-- library-list-svr4: Root element with versioning -->
42566 <!ELEMENT library-list-svr4 (library)*>
42567 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
42568 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
42569 <!ELEMENT library EMPTY>
42570 <!ATTLIST library name CDATA #REQUIRED>
42571 <!ATTLIST library lm CDATA #REQUIRED>
42572 <!ATTLIST library l_addr CDATA #REQUIRED>
42573 <!ATTLIST library l_ld CDATA #REQUIRED>
42576 @node Memory Map Format
42577 @section Memory Map Format
42578 @cindex memory map format
42580 To be able to write into flash memory, @value{GDBN} needs to obtain a
42581 memory map from the target. This section describes the format of the
42584 The memory map is obtained using the @samp{qXfer:memory-map:read}
42585 (@pxref{qXfer memory map read}) packet and is an XML document that
42586 lists memory regions.
42588 @value{GDBN} must be linked with the Expat library to support XML
42589 memory maps. @xref{Expat}.
42591 The top-level structure of the document is shown below:
42594 <?xml version="1.0"?>
42595 <!DOCTYPE memory-map
42596 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
42597 "http://sourceware.org/gdb/gdb-memory-map.dtd">
42603 Each region can be either:
42608 A region of RAM starting at @var{addr} and extending for @var{length}
42612 <memory type="ram" start="@var{addr}" length="@var{length}"/>
42617 A region of read-only memory:
42620 <memory type="rom" start="@var{addr}" length="@var{length}"/>
42625 A region of flash memory, with erasure blocks @var{blocksize}
42629 <memory type="flash" start="@var{addr}" length="@var{length}">
42630 <property name="blocksize">@var{blocksize}</property>
42636 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
42637 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
42638 packets to write to addresses in such ranges.
42640 The formal DTD for memory map format is given below:
42643 <!-- ................................................... -->
42644 <!-- Memory Map XML DTD ................................ -->
42645 <!-- File: memory-map.dtd .............................. -->
42646 <!-- .................................... .............. -->
42647 <!-- memory-map.dtd -->
42648 <!-- memory-map: Root element with versioning -->
42649 <!ELEMENT memory-map (memory | property)>
42650 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
42651 <!ELEMENT memory (property)>
42652 <!-- memory: Specifies a memory region,
42653 and its type, or device. -->
42654 <!ATTLIST memory type CDATA #REQUIRED
42655 start CDATA #REQUIRED
42656 length CDATA #REQUIRED
42657 device CDATA #IMPLIED>
42658 <!-- property: Generic attribute tag -->
42659 <!ELEMENT property (#PCDATA | property)*>
42660 <!ATTLIST property name CDATA #REQUIRED>
42663 @node Thread List Format
42664 @section Thread List Format
42665 @cindex thread list format
42667 To efficiently update the list of threads and their attributes,
42668 @value{GDBN} issues the @samp{qXfer:threads:read} packet
42669 (@pxref{qXfer threads read}) and obtains the XML document with
42670 the following structure:
42673 <?xml version="1.0"?>
42675 <thread id="id" core="0">
42676 ... description ...
42681 Each @samp{thread} element must have the @samp{id} attribute that
42682 identifies the thread (@pxref{thread-id syntax}). The
42683 @samp{core} attribute, if present, specifies which processor core
42684 the thread was last executing on. The content of the of @samp{thread}
42685 element is interpreted as human-readable auxilliary information.
42687 @node Traceframe Info Format
42688 @section Traceframe Info Format
42689 @cindex traceframe info format
42691 To be able to know which objects in the inferior can be examined when
42692 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
42693 memory ranges, registers and trace state variables that have been
42694 collected in a traceframe.
42696 This list is obtained using the @samp{qXfer:traceframe-info:read}
42697 (@pxref{qXfer traceframe info read}) packet and is an XML document.
42699 @value{GDBN} must be linked with the Expat library to support XML
42700 traceframe info discovery. @xref{Expat}.
42702 The top-level structure of the document is shown below:
42705 <?xml version="1.0"?>
42706 <!DOCTYPE traceframe-info
42707 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
42708 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
42714 Each traceframe block can be either:
42719 A region of collected memory starting at @var{addr} and extending for
42720 @var{length} bytes from there:
42723 <memory start="@var{addr}" length="@var{length}"/>
42727 A block indicating trace state variable numbered @var{number} has been
42731 <tvar id="@var{number}"/>
42736 The formal DTD for the traceframe info format is given below:
42739 <!ELEMENT traceframe-info (memory | tvar)* >
42740 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
42742 <!ELEMENT memory EMPTY>
42743 <!ATTLIST memory start CDATA #REQUIRED
42744 length CDATA #REQUIRED>
42746 <!ATTLIST tvar id CDATA #REQUIRED>
42749 @node Branch Trace Format
42750 @section Branch Trace Format
42751 @cindex branch trace format
42753 In order to display the branch trace of an inferior thread,
42754 @value{GDBN} needs to obtain the list of branches. This list is
42755 represented as list of sequential code blocks that are connected via
42756 branches. The code in each block has been executed sequentially.
42758 This list is obtained using the @samp{qXfer:btrace:read}
42759 (@pxref{qXfer btrace read}) packet and is an XML document.
42761 @value{GDBN} must be linked with the Expat library to support XML
42762 traceframe info discovery. @xref{Expat}.
42764 The top-level structure of the document is shown below:
42767 <?xml version="1.0"?>
42769 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
42770 "http://sourceware.org/gdb/gdb-btrace.dtd">
42779 A block of sequentially executed instructions starting at @var{begin}
42780 and ending at @var{end}:
42783 <block begin="@var{begin}" end="@var{end}"/>
42788 The formal DTD for the branch trace format is given below:
42791 <!ELEMENT btrace (block)* >
42792 <!ATTLIST btrace version CDATA #FIXED "1.0">
42794 <!ELEMENT block EMPTY>
42795 <!ATTLIST block begin CDATA #REQUIRED
42796 end CDATA #REQUIRED>
42799 @include agentexpr.texi
42801 @node Target Descriptions
42802 @appendix Target Descriptions
42803 @cindex target descriptions
42805 One of the challenges of using @value{GDBN} to debug embedded systems
42806 is that there are so many minor variants of each processor
42807 architecture in use. It is common practice for vendors to start with
42808 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
42809 and then make changes to adapt it to a particular market niche. Some
42810 architectures have hundreds of variants, available from dozens of
42811 vendors. This leads to a number of problems:
42815 With so many different customized processors, it is difficult for
42816 the @value{GDBN} maintainers to keep up with the changes.
42818 Since individual variants may have short lifetimes or limited
42819 audiences, it may not be worthwhile to carry information about every
42820 variant in the @value{GDBN} source tree.
42822 When @value{GDBN} does support the architecture of the embedded system
42823 at hand, the task of finding the correct architecture name to give the
42824 @command{set architecture} command can be error-prone.
42827 To address these problems, the @value{GDBN} remote protocol allows a
42828 target system to not only identify itself to @value{GDBN}, but to
42829 actually describe its own features. This lets @value{GDBN} support
42830 processor variants it has never seen before --- to the extent that the
42831 descriptions are accurate, and that @value{GDBN} understands them.
42833 @value{GDBN} must be linked with the Expat library to support XML
42834 target descriptions. @xref{Expat}.
42837 * Retrieving Descriptions:: How descriptions are fetched from a target.
42838 * Target Description Format:: The contents of a target description.
42839 * Predefined Target Types:: Standard types available for target
42841 * Standard Target Features:: Features @value{GDBN} knows about.
42844 @node Retrieving Descriptions
42845 @section Retrieving Descriptions
42847 Target descriptions can be read from the target automatically, or
42848 specified by the user manually. The default behavior is to read the
42849 description from the target. @value{GDBN} retrieves it via the remote
42850 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
42851 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
42852 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
42853 XML document, of the form described in @ref{Target Description
42856 Alternatively, you can specify a file to read for the target description.
42857 If a file is set, the target will not be queried. The commands to
42858 specify a file are:
42861 @cindex set tdesc filename
42862 @item set tdesc filename @var{path}
42863 Read the target description from @var{path}.
42865 @cindex unset tdesc filename
42866 @item unset tdesc filename
42867 Do not read the XML target description from a file. @value{GDBN}
42868 will use the description supplied by the current target.
42870 @cindex show tdesc filename
42871 @item show tdesc filename
42872 Show the filename to read for a target description, if any.
42876 @node Target Description Format
42877 @section Target Description Format
42878 @cindex target descriptions, XML format
42880 A target description annex is an @uref{http://www.w3.org/XML/, XML}
42881 document which complies with the Document Type Definition provided in
42882 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
42883 means you can use generally available tools like @command{xmllint} to
42884 check that your feature descriptions are well-formed and valid.
42885 However, to help people unfamiliar with XML write descriptions for
42886 their targets, we also describe the grammar here.
42888 Target descriptions can identify the architecture of the remote target
42889 and (for some architectures) provide information about custom register
42890 sets. They can also identify the OS ABI of the remote target.
42891 @value{GDBN} can use this information to autoconfigure for your
42892 target, or to warn you if you connect to an unsupported target.
42894 Here is a simple target description:
42897 <target version="1.0">
42898 <architecture>i386:x86-64</architecture>
42903 This minimal description only says that the target uses
42904 the x86-64 architecture.
42906 A target description has the following overall form, with [ ] marking
42907 optional elements and @dots{} marking repeatable elements. The elements
42908 are explained further below.
42911 <?xml version="1.0"?>
42912 <!DOCTYPE target SYSTEM "gdb-target.dtd">
42913 <target version="1.0">
42914 @r{[}@var{architecture}@r{]}
42915 @r{[}@var{osabi}@r{]}
42916 @r{[}@var{compatible}@r{]}
42917 @r{[}@var{feature}@dots{}@r{]}
42922 The description is generally insensitive to whitespace and line
42923 breaks, under the usual common-sense rules. The XML version
42924 declaration and document type declaration can generally be omitted
42925 (@value{GDBN} does not require them), but specifying them may be
42926 useful for XML validation tools. The @samp{version} attribute for
42927 @samp{<target>} may also be omitted, but we recommend
42928 including it; if future versions of @value{GDBN} use an incompatible
42929 revision of @file{gdb-target.dtd}, they will detect and report
42930 the version mismatch.
42932 @subsection Inclusion
42933 @cindex target descriptions, inclusion
42936 @cindex <xi:include>
42939 It can sometimes be valuable to split a target description up into
42940 several different annexes, either for organizational purposes, or to
42941 share files between different possible target descriptions. You can
42942 divide a description into multiple files by replacing any element of
42943 the target description with an inclusion directive of the form:
42946 <xi:include href="@var{document}"/>
42950 When @value{GDBN} encounters an element of this form, it will retrieve
42951 the named XML @var{document}, and replace the inclusion directive with
42952 the contents of that document. If the current description was read
42953 using @samp{qXfer}, then so will be the included document;
42954 @var{document} will be interpreted as the name of an annex. If the
42955 current description was read from a file, @value{GDBN} will look for
42956 @var{document} as a file in the same directory where it found the
42957 original description.
42959 @subsection Architecture
42960 @cindex <architecture>
42962 An @samp{<architecture>} element has this form:
42965 <architecture>@var{arch}</architecture>
42968 @var{arch} is one of the architectures from the set accepted by
42969 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
42972 @cindex @code{<osabi>}
42974 This optional field was introduced in @value{GDBN} version 7.0.
42975 Previous versions of @value{GDBN} ignore it.
42977 An @samp{<osabi>} element has this form:
42980 <osabi>@var{abi-name}</osabi>
42983 @var{abi-name} is an OS ABI name from the same selection accepted by
42984 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
42986 @subsection Compatible Architecture
42987 @cindex @code{<compatible>}
42989 This optional field was introduced in @value{GDBN} version 7.0.
42990 Previous versions of @value{GDBN} ignore it.
42992 A @samp{<compatible>} element has this form:
42995 <compatible>@var{arch}</compatible>
42998 @var{arch} is one of the architectures from the set accepted by
42999 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
43001 A @samp{<compatible>} element is used to specify that the target
43002 is able to run binaries in some other than the main target architecture
43003 given by the @samp{<architecture>} element. For example, on the
43004 Cell Broadband Engine, the main architecture is @code{powerpc:common}
43005 or @code{powerpc:common64}, but the system is able to run binaries
43006 in the @code{spu} architecture as well. The way to describe this
43007 capability with @samp{<compatible>} is as follows:
43010 <architecture>powerpc:common</architecture>
43011 <compatible>spu</compatible>
43014 @subsection Features
43017 Each @samp{<feature>} describes some logical portion of the target
43018 system. Features are currently used to describe available CPU
43019 registers and the types of their contents. A @samp{<feature>} element
43023 <feature name="@var{name}">
43024 @r{[}@var{type}@dots{}@r{]}
43030 Each feature's name should be unique within the description. The name
43031 of a feature does not matter unless @value{GDBN} has some special
43032 knowledge of the contents of that feature; if it does, the feature
43033 should have its standard name. @xref{Standard Target Features}.
43037 Any register's value is a collection of bits which @value{GDBN} must
43038 interpret. The default interpretation is a two's complement integer,
43039 but other types can be requested by name in the register description.
43040 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
43041 Target Types}), and the description can define additional composite types.
43043 Each type element must have an @samp{id} attribute, which gives
43044 a unique (within the containing @samp{<feature>}) name to the type.
43045 Types must be defined before they are used.
43048 Some targets offer vector registers, which can be treated as arrays
43049 of scalar elements. These types are written as @samp{<vector>} elements,
43050 specifying the array element type, @var{type}, and the number of elements,
43054 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
43058 If a register's value is usefully viewed in multiple ways, define it
43059 with a union type containing the useful representations. The
43060 @samp{<union>} element contains one or more @samp{<field>} elements,
43061 each of which has a @var{name} and a @var{type}:
43064 <union id="@var{id}">
43065 <field name="@var{name}" type="@var{type}"/>
43071 If a register's value is composed from several separate values, define
43072 it with a structure type. There are two forms of the @samp{<struct>}
43073 element; a @samp{<struct>} element must either contain only bitfields
43074 or contain no bitfields. If the structure contains only bitfields,
43075 its total size in bytes must be specified, each bitfield must have an
43076 explicit start and end, and bitfields are automatically assigned an
43077 integer type. The field's @var{start} should be less than or
43078 equal to its @var{end}, and zero represents the least significant bit.
43081 <struct id="@var{id}" size="@var{size}">
43082 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
43087 If the structure contains no bitfields, then each field has an
43088 explicit type, and no implicit padding is added.
43091 <struct id="@var{id}">
43092 <field name="@var{name}" type="@var{type}"/>
43098 If a register's value is a series of single-bit flags, define it with
43099 a flags type. The @samp{<flags>} element has an explicit @var{size}
43100 and contains one or more @samp{<field>} elements. Each field has a
43101 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
43105 <flags id="@var{id}" size="@var{size}">
43106 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
43111 @subsection Registers
43114 Each register is represented as an element with this form:
43117 <reg name="@var{name}"
43118 bitsize="@var{size}"
43119 @r{[}regnum="@var{num}"@r{]}
43120 @r{[}save-restore="@var{save-restore}"@r{]}
43121 @r{[}type="@var{type}"@r{]}
43122 @r{[}group="@var{group}"@r{]}/>
43126 The components are as follows:
43131 The register's name; it must be unique within the target description.
43134 The register's size, in bits.
43137 The register's number. If omitted, a register's number is one greater
43138 than that of the previous register (either in the current feature or in
43139 a preceding feature); the first register in the target description
43140 defaults to zero. This register number is used to read or write
43141 the register; e.g.@: it is used in the remote @code{p} and @code{P}
43142 packets, and registers appear in the @code{g} and @code{G} packets
43143 in order of increasing register number.
43146 Whether the register should be preserved across inferior function
43147 calls; this must be either @code{yes} or @code{no}. The default is
43148 @code{yes}, which is appropriate for most registers except for
43149 some system control registers; this is not related to the target's
43153 The type of the register. @var{type} may be a predefined type, a type
43154 defined in the current feature, or one of the special types @code{int}
43155 and @code{float}. @code{int} is an integer type of the correct size
43156 for @var{bitsize}, and @code{float} is a floating point type (in the
43157 architecture's normal floating point format) of the correct size for
43158 @var{bitsize}. The default is @code{int}.
43161 The register group to which this register belongs. @var{group} must
43162 be either @code{general}, @code{float}, or @code{vector}. If no
43163 @var{group} is specified, @value{GDBN} will not display the register
43164 in @code{info registers}.
43168 @node Predefined Target Types
43169 @section Predefined Target Types
43170 @cindex target descriptions, predefined types
43172 Type definitions in the self-description can build up composite types
43173 from basic building blocks, but can not define fundamental types. Instead,
43174 standard identifiers are provided by @value{GDBN} for the fundamental
43175 types. The currently supported types are:
43184 Signed integer types holding the specified number of bits.
43191 Unsigned integer types holding the specified number of bits.
43195 Pointers to unspecified code and data. The program counter and
43196 any dedicated return address register may be marked as code
43197 pointers; printing a code pointer converts it into a symbolic
43198 address. The stack pointer and any dedicated address registers
43199 may be marked as data pointers.
43202 Single precision IEEE floating point.
43205 Double precision IEEE floating point.
43208 The 12-byte extended precision format used by ARM FPA registers.
43211 The 10-byte extended precision format used by x87 registers.
43214 32bit @sc{eflags} register used by x86.
43217 32bit @sc{mxcsr} register used by x86.
43221 @node Standard Target Features
43222 @section Standard Target Features
43223 @cindex target descriptions, standard features
43225 A target description must contain either no registers or all the
43226 target's registers. If the description contains no registers, then
43227 @value{GDBN} will assume a default register layout, selected based on
43228 the architecture. If the description contains any registers, the
43229 default layout will not be used; the standard registers must be
43230 described in the target description, in such a way that @value{GDBN}
43231 can recognize them.
43233 This is accomplished by giving specific names to feature elements
43234 which contain standard registers. @value{GDBN} will look for features
43235 with those names and verify that they contain the expected registers;
43236 if any known feature is missing required registers, or if any required
43237 feature is missing, @value{GDBN} will reject the target
43238 description. You can add additional registers to any of the
43239 standard features --- @value{GDBN} will display them just as if
43240 they were added to an unrecognized feature.
43242 This section lists the known features and their expected contents.
43243 Sample XML documents for these features are included in the
43244 @value{GDBN} source tree, in the directory @file{gdb/features}.
43246 Names recognized by @value{GDBN} should include the name of the
43247 company or organization which selected the name, and the overall
43248 architecture to which the feature applies; so e.g.@: the feature
43249 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
43251 The names of registers are not case sensitive for the purpose
43252 of recognizing standard features, but @value{GDBN} will only display
43253 registers using the capitalization used in the description.
43256 * AArch64 Features::
43261 * Nios II Features::
43262 * PowerPC Features::
43263 * S/390 and System z Features::
43268 @node AArch64 Features
43269 @subsection AArch64 Features
43270 @cindex target descriptions, AArch64 features
43272 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
43273 targets. It should contain registers @samp{x0} through @samp{x30},
43274 @samp{sp}, @samp{pc}, and @samp{cpsr}.
43276 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
43277 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
43281 @subsection ARM Features
43282 @cindex target descriptions, ARM features
43284 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
43286 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
43287 @samp{lr}, @samp{pc}, and @samp{cpsr}.
43289 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
43290 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
43291 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
43294 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
43295 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
43297 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
43298 it should contain at least registers @samp{wR0} through @samp{wR15} and
43299 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
43300 @samp{wCSSF}, and @samp{wCASF} registers are optional.
43302 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
43303 should contain at least registers @samp{d0} through @samp{d15}. If
43304 they are present, @samp{d16} through @samp{d31} should also be included.
43305 @value{GDBN} will synthesize the single-precision registers from
43306 halves of the double-precision registers.
43308 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
43309 need to contain registers; it instructs @value{GDBN} to display the
43310 VFP double-precision registers as vectors and to synthesize the
43311 quad-precision registers from pairs of double-precision registers.
43312 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
43313 be present and include 32 double-precision registers.
43315 @node i386 Features
43316 @subsection i386 Features
43317 @cindex target descriptions, i386 features
43319 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
43320 targets. It should describe the following registers:
43324 @samp{eax} through @samp{edi} plus @samp{eip} for i386
43326 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
43328 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
43329 @samp{fs}, @samp{gs}
43331 @samp{st0} through @samp{st7}
43333 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
43334 @samp{foseg}, @samp{fooff} and @samp{fop}
43337 The register sets may be different, depending on the target.
43339 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
43340 describe registers:
43344 @samp{xmm0} through @samp{xmm7} for i386
43346 @samp{xmm0} through @samp{xmm15} for amd64
43351 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
43352 @samp{org.gnu.gdb.i386.sse} feature. It should
43353 describe the upper 128 bits of @sc{ymm} registers:
43357 @samp{ymm0h} through @samp{ymm7h} for i386
43359 @samp{ymm0h} through @samp{ymm15h} for amd64
43362 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel(R)
43363 Memory Protection Extension (MPX). It should describe the following registers:
43367 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
43369 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
43372 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
43373 describe a single register, @samp{orig_eax}.
43375 @node MIPS Features
43376 @subsection @acronym{MIPS} Features
43377 @cindex target descriptions, @acronym{MIPS} features
43379 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
43380 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
43381 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
43384 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
43385 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
43386 registers. They may be 32-bit or 64-bit depending on the target.
43388 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
43389 it may be optional in a future version of @value{GDBN}. It should
43390 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
43391 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
43393 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
43394 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
43395 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
43396 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
43398 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
43399 contain a single register, @samp{restart}, which is used by the
43400 Linux kernel to control restartable syscalls.
43402 @node M68K Features
43403 @subsection M68K Features
43404 @cindex target descriptions, M68K features
43407 @item @samp{org.gnu.gdb.m68k.core}
43408 @itemx @samp{org.gnu.gdb.coldfire.core}
43409 @itemx @samp{org.gnu.gdb.fido.core}
43410 One of those features must be always present.
43411 The feature that is present determines which flavor of m68k is
43412 used. The feature that is present should contain registers
43413 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
43414 @samp{sp}, @samp{ps} and @samp{pc}.
43416 @item @samp{org.gnu.gdb.coldfire.fp}
43417 This feature is optional. If present, it should contain registers
43418 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
43422 @node Nios II Features
43423 @subsection Nios II Features
43424 @cindex target descriptions, Nios II features
43426 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
43427 targets. It should contain the 32 core registers (@samp{zero},
43428 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
43429 @samp{pc}, and the 16 control registers (@samp{status} through
43432 @node PowerPC Features
43433 @subsection PowerPC Features
43434 @cindex target descriptions, PowerPC features
43436 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
43437 targets. It should contain registers @samp{r0} through @samp{r31},
43438 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
43439 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
43441 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
43442 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
43444 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
43445 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
43448 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
43449 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
43450 will combine these registers with the floating point registers
43451 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
43452 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
43453 through @samp{vs63}, the set of vector registers for POWER7.
43455 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
43456 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
43457 @samp{spefscr}. SPE targets should provide 32-bit registers in
43458 @samp{org.gnu.gdb.power.core} and provide the upper halves in
43459 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
43460 these to present registers @samp{ev0} through @samp{ev31} to the
43463 @node S/390 and System z Features
43464 @subsection S/390 and System z Features
43465 @cindex target descriptions, S/390 features
43466 @cindex target descriptions, System z features
43468 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
43469 System z targets. It should contain the PSW and the 16 general
43470 registers. In particular, System z targets should provide the 64-bit
43471 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
43472 S/390 targets should provide the 32-bit versions of these registers.
43473 A System z target that runs in 31-bit addressing mode should provide
43474 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
43475 register's upper halves @samp{r0h} through @samp{r15h}, and their
43476 lower halves @samp{r0l} through @samp{r15l}.
43478 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
43479 contain the 64-bit registers @samp{f0} through @samp{f15}, and
43482 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
43483 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
43485 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
43486 contain the register @samp{orig_r2}, which is 64-bit wide on System z
43487 targets and 32-bit otherwise. In addition, the feature may contain
43488 the @samp{last_break} register, whose width depends on the addressing
43489 mode, as well as the @samp{system_call} register, which is always
43492 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
43493 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
43494 @samp{atia}, and @samp{tr0} through @samp{tr15}.
43496 @node TIC6x Features
43497 @subsection TMS320C6x Features
43498 @cindex target descriptions, TIC6x features
43499 @cindex target descriptions, TMS320C6x features
43500 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
43501 targets. It should contain registers @samp{A0} through @samp{A15},
43502 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
43504 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
43505 contain registers @samp{A16} through @samp{A31} and @samp{B16}
43506 through @samp{B31}.
43508 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
43509 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
43511 @node Operating System Information
43512 @appendix Operating System Information
43513 @cindex operating system information
43519 Users of @value{GDBN} often wish to obtain information about the state of
43520 the operating system running on the target---for example the list of
43521 processes, or the list of open files. This section describes the
43522 mechanism that makes it possible. This mechanism is similar to the
43523 target features mechanism (@pxref{Target Descriptions}), but focuses
43524 on a different aspect of target.
43526 Operating system information is retrived from the target via the
43527 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
43528 read}). The object name in the request should be @samp{osdata}, and
43529 the @var{annex} identifies the data to be fetched.
43532 @appendixsection Process list
43533 @cindex operating system information, process list
43535 When requesting the process list, the @var{annex} field in the
43536 @samp{qXfer} request should be @samp{processes}. The returned data is
43537 an XML document. The formal syntax of this document is defined in
43538 @file{gdb/features/osdata.dtd}.
43540 An example document is:
43543 <?xml version="1.0"?>
43544 <!DOCTYPE target SYSTEM "osdata.dtd">
43545 <osdata type="processes">
43547 <column name="pid">1</column>
43548 <column name="user">root</column>
43549 <column name="command">/sbin/init</column>
43550 <column name="cores">1,2,3</column>
43555 Each item should include a column whose name is @samp{pid}. The value
43556 of that column should identify the process on the target. The
43557 @samp{user} and @samp{command} columns are optional, and will be
43558 displayed by @value{GDBN}. The @samp{cores} column, if present,
43559 should contain a comma-separated list of cores that this process
43560 is running on. Target may provide additional columns,
43561 which @value{GDBN} currently ignores.
43563 @node Trace File Format
43564 @appendix Trace File Format
43565 @cindex trace file format
43567 The trace file comes in three parts: a header, a textual description
43568 section, and a trace frame section with binary data.
43570 The header has the form @code{\x7fTRACE0\n}. The first byte is
43571 @code{0x7f} so as to indicate that the file contains binary data,
43572 while the @code{0} is a version number that may have different values
43575 The description section consists of multiple lines of @sc{ascii} text
43576 separated by newline characters (@code{0xa}). The lines may include a
43577 variety of optional descriptive or context-setting information, such
43578 as tracepoint definitions or register set size. @value{GDBN} will
43579 ignore any line that it does not recognize. An empty line marks the end
43582 @c FIXME add some specific types of data
43584 The trace frame section consists of a number of consecutive frames.
43585 Each frame begins with a two-byte tracepoint number, followed by a
43586 four-byte size giving the amount of data in the frame. The data in
43587 the frame consists of a number of blocks, each introduced by a
43588 character indicating its type (at least register, memory, and trace
43589 state variable). The data in this section is raw binary, not a
43590 hexadecimal or other encoding; its endianness matches the target's
43593 @c FIXME bi-arch may require endianness/arch info in description section
43596 @item R @var{bytes}
43597 Register block. The number and ordering of bytes matches that of a
43598 @code{g} packet in the remote protocol. Note that these are the
43599 actual bytes, in target order and @value{GDBN} register order, not a
43600 hexadecimal encoding.
43602 @item M @var{address} @var{length} @var{bytes}...
43603 Memory block. This is a contiguous block of memory, at the 8-byte
43604 address @var{address}, with a 2-byte length @var{length}, followed by
43605 @var{length} bytes.
43607 @item V @var{number} @var{value}
43608 Trace state variable block. This records the 8-byte signed value
43609 @var{value} of trace state variable numbered @var{number}.
43613 Future enhancements of the trace file format may include additional types
43616 @node Index Section Format
43617 @appendix @code{.gdb_index} section format
43618 @cindex .gdb_index section format
43619 @cindex index section format
43621 This section documents the index section that is created by @code{save
43622 gdb-index} (@pxref{Index Files}). The index section is
43623 DWARF-specific; some knowledge of DWARF is assumed in this
43626 The mapped index file format is designed to be directly
43627 @code{mmap}able on any architecture. In most cases, a datum is
43628 represented using a little-endian 32-bit integer value, called an
43629 @code{offset_type}. Big endian machines must byte-swap the values
43630 before using them. Exceptions to this rule are noted. The data is
43631 laid out such that alignment is always respected.
43633 A mapped index consists of several areas, laid out in order.
43637 The file header. This is a sequence of values, of @code{offset_type}
43638 unless otherwise noted:
43642 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
43643 Version 4 uses a different hashing function from versions 5 and 6.
43644 Version 6 includes symbols for inlined functions, whereas versions 4
43645 and 5 do not. Version 7 adds attributes to the CU indices in the
43646 symbol table. Version 8 specifies that symbols from DWARF type units
43647 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
43648 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
43650 @value{GDBN} will only read version 4, 5, or 6 indices
43651 by specifying @code{set use-deprecated-index-sections on}.
43652 GDB has a workaround for potentially broken version 7 indices so it is
43653 currently not flagged as deprecated.
43656 The offset, from the start of the file, of the CU list.
43659 The offset, from the start of the file, of the types CU list. Note
43660 that this area can be empty, in which case this offset will be equal
43661 to the next offset.
43664 The offset, from the start of the file, of the address area.
43667 The offset, from the start of the file, of the symbol table.
43670 The offset, from the start of the file, of the constant pool.
43674 The CU list. This is a sequence of pairs of 64-bit little-endian
43675 values, sorted by the CU offset. The first element in each pair is
43676 the offset of a CU in the @code{.debug_info} section. The second
43677 element in each pair is the length of that CU. References to a CU
43678 elsewhere in the map are done using a CU index, which is just the
43679 0-based index into this table. Note that if there are type CUs, then
43680 conceptually CUs and type CUs form a single list for the purposes of
43684 The types CU list. This is a sequence of triplets of 64-bit
43685 little-endian values. In a triplet, the first value is the CU offset,
43686 the second value is the type offset in the CU, and the third value is
43687 the type signature. The types CU list is not sorted.
43690 The address area. The address area consists of a sequence of address
43691 entries. Each address entry has three elements:
43695 The low address. This is a 64-bit little-endian value.
43698 The high address. This is a 64-bit little-endian value. Like
43699 @code{DW_AT_high_pc}, the value is one byte beyond the end.
43702 The CU index. This is an @code{offset_type} value.
43706 The symbol table. This is an open-addressed hash table. The size of
43707 the hash table is always a power of 2.
43709 Each slot in the hash table consists of a pair of @code{offset_type}
43710 values. The first value is the offset of the symbol's name in the
43711 constant pool. The second value is the offset of the CU vector in the
43714 If both values are 0, then this slot in the hash table is empty. This
43715 is ok because while 0 is a valid constant pool index, it cannot be a
43716 valid index for both a string and a CU vector.
43718 The hash value for a table entry is computed by applying an
43719 iterative hash function to the symbol's name. Starting with an
43720 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
43721 the string is incorporated into the hash using the formula depending on the
43726 The formula is @code{r = r * 67 + c - 113}.
43728 @item Versions 5 to 7
43729 The formula is @code{r = r * 67 + tolower (c) - 113}.
43732 The terminating @samp{\0} is not incorporated into the hash.
43734 The step size used in the hash table is computed via
43735 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
43736 value, and @samp{size} is the size of the hash table. The step size
43737 is used to find the next candidate slot when handling a hash
43740 The names of C@t{++} symbols in the hash table are canonicalized. We
43741 don't currently have a simple description of the canonicalization
43742 algorithm; if you intend to create new index sections, you must read
43746 The constant pool. This is simply a bunch of bytes. It is organized
43747 so that alignment is correct: CU vectors are stored first, followed by
43750 A CU vector in the constant pool is a sequence of @code{offset_type}
43751 values. The first value is the number of CU indices in the vector.
43752 Each subsequent value is the index and symbol attributes of a CU in
43753 the CU list. This element in the hash table is used to indicate which
43754 CUs define the symbol and how the symbol is used.
43755 See below for the format of each CU index+attributes entry.
43757 A string in the constant pool is zero-terminated.
43760 Attributes were added to CU index values in @code{.gdb_index} version 7.
43761 If a symbol has multiple uses within a CU then there is one
43762 CU index+attributes value for each use.
43764 The format of each CU index+attributes entry is as follows
43770 This is the index of the CU in the CU list.
43772 These bits are reserved for future purposes and must be zero.
43774 The kind of the symbol in the CU.
43778 This value is reserved and should not be used.
43779 By reserving zero the full @code{offset_type} value is backwards compatible
43780 with previous versions of the index.
43782 The symbol is a type.
43784 The symbol is a variable or an enum value.
43786 The symbol is a function.
43788 Any other kind of symbol.
43790 These values are reserved.
43794 This bit is zero if the value is global and one if it is static.
43796 The determination of whether a symbol is global or static is complicated.
43797 The authorative reference is the file @file{dwarf2read.c} in
43798 @value{GDBN} sources.
43802 This pseudo-code describes the computation of a symbol's kind and
43803 global/static attributes in the index.
43806 is_external = get_attribute (die, DW_AT_external);
43807 language = get_attribute (cu_die, DW_AT_language);
43810 case DW_TAG_typedef:
43811 case DW_TAG_base_type:
43812 case DW_TAG_subrange_type:
43816 case DW_TAG_enumerator:
43818 is_static = (language != CPLUS && language != JAVA);
43820 case DW_TAG_subprogram:
43822 is_static = ! (is_external || language == ADA);
43824 case DW_TAG_constant:
43826 is_static = ! is_external;
43828 case DW_TAG_variable:
43830 is_static = ! is_external;
43832 case DW_TAG_namespace:
43836 case DW_TAG_class_type:
43837 case DW_TAG_interface_type:
43838 case DW_TAG_structure_type:
43839 case DW_TAG_union_type:
43840 case DW_TAG_enumeration_type:
43842 is_static = (language != CPLUS && language != JAVA);
43850 @appendix Manual pages
43854 * gdb man:: The GNU Debugger man page
43855 * gdbserver man:: Remote Server for the GNU Debugger man page
43856 * gcore man:: Generate a core file of a running program
43857 * gdbinit man:: gdbinit scripts
43863 @c man title gdb The GNU Debugger
43865 @c man begin SYNOPSIS gdb
43866 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
43867 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
43868 [@option{-b}@w{ }@var{bps}]
43869 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
43870 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
43871 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
43872 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
43873 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
43876 @c man begin DESCRIPTION gdb
43877 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
43878 going on ``inside'' another program while it executes -- or what another
43879 program was doing at the moment it crashed.
43881 @value{GDBN} can do four main kinds of things (plus other things in support of
43882 these) to help you catch bugs in the act:
43886 Start your program, specifying anything that might affect its behavior.
43889 Make your program stop on specified conditions.
43892 Examine what has happened, when your program has stopped.
43895 Change things in your program, so you can experiment with correcting the
43896 effects of one bug and go on to learn about another.
43899 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
43902 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
43903 commands from the terminal until you tell it to exit with the @value{GDBN}
43904 command @code{quit}. You can get online help from @value{GDBN} itself
43905 by using the command @code{help}.
43907 You can run @code{gdb} with no arguments or options; but the most
43908 usual way to start @value{GDBN} is with one argument or two, specifying an
43909 executable program as the argument:
43915 You can also start with both an executable program and a core file specified:
43921 You can, instead, specify a process ID as a second argument, if you want
43922 to debug a running process:
43930 would attach @value{GDBN} to process @code{1234} (unless you also have a file
43931 named @file{1234}; @value{GDBN} does check for a core file first).
43932 With option @option{-p} you can omit the @var{program} filename.
43934 Here are some of the most frequently needed @value{GDBN} commands:
43936 @c pod2man highlights the right hand side of the @item lines.
43938 @item break [@var{file}:]@var{functiop}
43939 Set a breakpoint at @var{function} (in @var{file}).
43941 @item run [@var{arglist}]
43942 Start your program (with @var{arglist}, if specified).
43945 Backtrace: display the program stack.
43947 @item print @var{expr}
43948 Display the value of an expression.
43951 Continue running your program (after stopping, e.g. at a breakpoint).
43954 Execute next program line (after stopping); step @emph{over} any
43955 function calls in the line.
43957 @item edit [@var{file}:]@var{function}
43958 look at the program line where it is presently stopped.
43960 @item list [@var{file}:]@var{function}
43961 type the text of the program in the vicinity of where it is presently stopped.
43964 Execute next program line (after stopping); step @emph{into} any
43965 function calls in the line.
43967 @item help [@var{name}]
43968 Show information about @value{GDBN} command @var{name}, or general information
43969 about using @value{GDBN}.
43972 Exit from @value{GDBN}.
43976 For full details on @value{GDBN},
43977 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43978 by Richard M. Stallman and Roland H. Pesch. The same text is available online
43979 as the @code{gdb} entry in the @code{info} program.
43983 @c man begin OPTIONS gdb
43984 Any arguments other than options specify an executable
43985 file and core file (or process ID); that is, the first argument
43986 encountered with no
43987 associated option flag is equivalent to a @option{-se} option, and the second,
43988 if any, is equivalent to a @option{-c} option if it's the name of a file.
43990 both long and short forms; both are shown here. The long forms are also
43991 recognized if you truncate them, so long as enough of the option is
43992 present to be unambiguous. (If you prefer, you can flag option
43993 arguments with @option{+} rather than @option{-}, though we illustrate the
43994 more usual convention.)
43996 All the options and command line arguments you give are processed
43997 in sequential order. The order makes a difference when the @option{-x}
44003 List all options, with brief explanations.
44005 @item -symbols=@var{file}
44006 @itemx -s @var{file}
44007 Read symbol table from file @var{file}.
44010 Enable writing into executable and core files.
44012 @item -exec=@var{file}
44013 @itemx -e @var{file}
44014 Use file @var{file} as the executable file to execute when
44015 appropriate, and for examining pure data in conjunction with a core
44018 @item -se=@var{file}
44019 Read symbol table from file @var{file} and use it as the executable
44022 @item -core=@var{file}
44023 @itemx -c @var{file}
44024 Use file @var{file} as a core dump to examine.
44026 @item -command=@var{file}
44027 @itemx -x @var{file}
44028 Execute @value{GDBN} commands from file @var{file}.
44030 @item -ex @var{command}
44031 Execute given @value{GDBN} @var{command}.
44033 @item -directory=@var{directory}
44034 @itemx -d @var{directory}
44035 Add @var{directory} to the path to search for source files.
44038 Do not execute commands from @file{~/.gdbinit}.
44042 Do not execute commands from any @file{.gdbinit} initialization files.
44046 ``Quiet''. Do not print the introductory and copyright messages. These
44047 messages are also suppressed in batch mode.
44050 Run in batch mode. Exit with status @code{0} after processing all the command
44051 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
44052 Exit with nonzero status if an error occurs in executing the @value{GDBN}
44053 commands in the command files.
44055 Batch mode may be useful for running @value{GDBN} as a filter, for example to
44056 download and run a program on another computer; in order to make this
44057 more useful, the message
44060 Program exited normally.
44064 (which is ordinarily issued whenever a program running under @value{GDBN} control
44065 terminates) is not issued when running in batch mode.
44067 @item -cd=@var{directory}
44068 Run @value{GDBN} using @var{directory} as its working directory,
44069 instead of the current directory.
44073 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
44074 @value{GDBN} to output the full file name and line number in a standard,
44075 recognizable fashion each time a stack frame is displayed (which
44076 includes each time the program stops). This recognizable format looks
44077 like two @samp{\032} characters, followed by the file name, line number
44078 and character position separated by colons, and a newline. The
44079 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
44080 characters as a signal to display the source code for the frame.
44083 Set the line speed (baud rate or bits per second) of any serial
44084 interface used by @value{GDBN} for remote debugging.
44086 @item -tty=@var{device}
44087 Run using @var{device} for your program's standard input and output.
44091 @c man begin SEEALSO gdb
44093 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44094 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44095 documentation are properly installed at your site, the command
44102 should give you access to the complete manual.
44104 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44105 Richard M. Stallman and Roland H. Pesch, July 1991.
44109 @node gdbserver man
44110 @heading gdbserver man
44112 @c man title gdbserver Remote Server for the GNU Debugger
44114 @c man begin SYNOPSIS gdbserver
44115 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
44117 gdbserver --attach @var{comm} @var{pid}
44119 gdbserver --multi @var{comm}
44123 @c man begin DESCRIPTION gdbserver
44124 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
44125 than the one which is running the program being debugged.
44128 @subheading Usage (server (target) side)
44131 Usage (server (target) side):
44134 First, you need to have a copy of the program you want to debug put onto
44135 the target system. The program can be stripped to save space if needed, as
44136 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
44137 the @value{GDBN} running on the host system.
44139 To use the server, you log on to the target system, and run the @command{gdbserver}
44140 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
44141 your program, and (c) its arguments. The general syntax is:
44144 target> gdbserver @var{comm} @var{program} [@var{args} ...]
44147 For example, using a serial port, you might say:
44151 @c @file would wrap it as F</dev/com1>.
44152 target> gdbserver /dev/com1 emacs foo.txt
44155 target> gdbserver @file{/dev/com1} emacs foo.txt
44159 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
44160 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
44161 waits patiently for the host @value{GDBN} to communicate with it.
44163 To use a TCP connection, you could say:
44166 target> gdbserver host:2345 emacs foo.txt
44169 This says pretty much the same thing as the last example, except that we are
44170 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
44171 that we are expecting to see a TCP connection from @code{host} to local TCP port
44172 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
44173 want for the port number as long as it does not conflict with any existing TCP
44174 ports on the target system. This same port number must be used in the host
44175 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
44176 you chose a port number that conflicts with another service, @command{gdbserver} will
44177 print an error message and exit.
44179 @command{gdbserver} can also attach to running programs.
44180 This is accomplished via the @option{--attach} argument. The syntax is:
44183 target> gdbserver --attach @var{comm} @var{pid}
44186 @var{pid} is the process ID of a currently running process. It isn't
44187 necessary to point @command{gdbserver} at a binary for the running process.
44189 To start @code{gdbserver} without supplying an initial command to run
44190 or process ID to attach, use the @option{--multi} command line option.
44191 In such case you should connect using @kbd{target extended-remote} to start
44192 the program you want to debug.
44195 target> gdbserver --multi @var{comm}
44199 @subheading Usage (host side)
44205 You need an unstripped copy of the target program on your host system, since
44206 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
44207 would, with the target program as the first argument. (You may need to use the
44208 @option{--baud} option if the serial line is running at anything except 9600 baud.)
44209 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
44210 new command you need to know about is @code{target remote}
44211 (or @code{target extended-remote}). Its argument is either
44212 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
44213 descriptor. For example:
44217 @c @file would wrap it as F</dev/ttyb>.
44218 (gdb) target remote /dev/ttyb
44221 (gdb) target remote @file{/dev/ttyb}
44226 communicates with the server via serial line @file{/dev/ttyb}, and:
44229 (gdb) target remote the-target:2345
44233 communicates via a TCP connection to port 2345 on host `the-target', where
44234 you previously started up @command{gdbserver} with the same port number. Note that for
44235 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
44236 command, otherwise you may get an error that looks something like
44237 `Connection refused'.
44239 @command{gdbserver} can also debug multiple inferiors at once,
44242 the @value{GDBN} manual in node @code{Inferiors and Programs}
44243 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
44246 @ref{Inferiors and Programs}.
44248 In such case use the @code{extended-remote} @value{GDBN} command variant:
44251 (gdb) target extended-remote the-target:2345
44254 The @command{gdbserver} option @option{--multi} may or may not be used in such
44258 @c man begin OPTIONS gdbserver
44259 There are three different modes for invoking @command{gdbserver}:
44264 Debug a specific program specified by its program name:
44267 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
44270 The @var{comm} parameter specifies how should the server communicate
44271 with @value{GDBN}; it is either a device name (to use a serial line),
44272 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
44273 stdin/stdout of @code{gdbserver}. Specify the name of the program to
44274 debug in @var{prog}. Any remaining arguments will be passed to the
44275 program verbatim. When the program exits, @value{GDBN} will close the
44276 connection, and @code{gdbserver} will exit.
44279 Debug a specific program by specifying the process ID of a running
44283 gdbserver --attach @var{comm} @var{pid}
44286 The @var{comm} parameter is as described above. Supply the process ID
44287 of a running program in @var{pid}; @value{GDBN} will do everything
44288 else. Like with the previous mode, when the process @var{pid} exits,
44289 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
44292 Multi-process mode -- debug more than one program/process:
44295 gdbserver --multi @var{comm}
44298 In this mode, @value{GDBN} can instruct @command{gdbserver} which
44299 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
44300 close the connection when a process being debugged exits, so you can
44301 debug several processes in the same session.
44304 In each of the modes you may specify these options:
44309 List all options, with brief explanations.
44312 This option causes @command{gdbserver} to print its version number and exit.
44315 @command{gdbserver} will attach to a running program. The syntax is:
44318 target> gdbserver --attach @var{comm} @var{pid}
44321 @var{pid} is the process ID of a currently running process. It isn't
44322 necessary to point @command{gdbserver} at a binary for the running process.
44325 To start @code{gdbserver} without supplying an initial command to run
44326 or process ID to attach, use this command line option.
44327 Then you can connect using @kbd{target extended-remote} and start
44328 the program you want to debug. The syntax is:
44331 target> gdbserver --multi @var{comm}
44335 Instruct @code{gdbserver} to display extra status information about the debugging
44337 This option is intended for @code{gdbserver} development and for bug reports to
44340 @item --remote-debug
44341 Instruct @code{gdbserver} to display remote protocol debug output.
44342 This option is intended for @code{gdbserver} development and for bug reports to
44346 Specify a wrapper to launch programs
44347 for debugging. The option should be followed by the name of the
44348 wrapper, then any command-line arguments to pass to the wrapper, then
44349 @kbd{--} indicating the end of the wrapper arguments.
44352 By default, @command{gdbserver} keeps the listening TCP port open, so that
44353 additional connections are possible. However, if you start @code{gdbserver}
44354 with the @option{--once} option, it will stop listening for any further
44355 connection attempts after connecting to the first @value{GDBN} session.
44357 @c --disable-packet is not documented for users.
44359 @c --disable-randomization and --no-disable-randomization are superseded by
44360 @c QDisableRandomization.
44365 @c man begin SEEALSO gdbserver
44367 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44368 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44369 documentation are properly installed at your site, the command
44375 should give you access to the complete manual.
44377 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44378 Richard M. Stallman and Roland H. Pesch, July 1991.
44385 @c man title gcore Generate a core file of a running program
44388 @c man begin SYNOPSIS gcore
44389 gcore [-o @var{filename}] @var{pid}
44393 @c man begin DESCRIPTION gcore
44394 Generate a core dump of a running program with process ID @var{pid}.
44395 Produced file is equivalent to a kernel produced core file as if the process
44396 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
44397 limit). Unlike after a crash, after @command{gcore} the program remains
44398 running without any change.
44401 @c man begin OPTIONS gcore
44403 @item -o @var{filename}
44404 The optional argument
44405 @var{filename} specifies the file name where to put the core dump.
44406 If not specified, the file name defaults to @file{core.@var{pid}},
44407 where @var{pid} is the running program process ID.
44411 @c man begin SEEALSO gcore
44413 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44414 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44415 documentation are properly installed at your site, the command
44422 should give you access to the complete manual.
44424 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44425 Richard M. Stallman and Roland H. Pesch, July 1991.
44432 @c man title gdbinit GDB initialization scripts
44435 @c man begin SYNOPSIS gdbinit
44436 @ifset SYSTEM_GDBINIT
44437 @value{SYSTEM_GDBINIT}
44446 @c man begin DESCRIPTION gdbinit
44447 These files contain @value{GDBN} commands to automatically execute during
44448 @value{GDBN} startup. The lines of contents are canned sequences of commands,
44451 the @value{GDBN} manual in node @code{Sequences}
44452 -- shell command @code{info -f gdb -n Sequences}.
44458 Please read more in
44460 the @value{GDBN} manual in node @code{Startup}
44461 -- shell command @code{info -f gdb -n Startup}.
44468 @ifset SYSTEM_GDBINIT
44469 @item @value{SYSTEM_GDBINIT}
44471 @ifclear SYSTEM_GDBINIT
44472 @item (not enabled with @code{--with-system-gdbinit} during compilation)
44474 System-wide initialization file. It is executed unless user specified
44475 @value{GDBN} option @code{-nx} or @code{-n}.
44478 the @value{GDBN} manual in node @code{System-wide configuration}
44479 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
44482 @ref{System-wide configuration}.
44486 User initialization file. It is executed unless user specified
44487 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
44490 Initialization file for current directory. It may need to be enabled with
44491 @value{GDBN} security command @code{set auto-load local-gdbinit}.
44494 the @value{GDBN} manual in node @code{Init File in the Current Directory}
44495 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
44498 @ref{Init File in the Current Directory}.
44503 @c man begin SEEALSO gdbinit
44505 gdb(1), @code{info -f gdb -n Startup}
44507 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44508 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44509 documentation are properly installed at your site, the command
44515 should give you access to the complete manual.
44517 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44518 Richard M. Stallman and Roland H. Pesch, July 1991.
44524 @node GNU Free Documentation License
44525 @appendix GNU Free Documentation License
44528 @node Concept Index
44529 @unnumbered Concept Index
44533 @node Command and Variable Index
44534 @unnumbered Command, Variable, and Function Index
44539 % I think something like @@colophon should be in texinfo. In the
44541 \long\def\colophon{\hbox to0pt{}\vfill
44542 \centerline{The body of this manual is set in}
44543 \centerline{\fontname\tenrm,}
44544 \centerline{with headings in {\bf\fontname\tenbf}}
44545 \centerline{and examples in {\tt\fontname\tentt}.}
44546 \centerline{{\it\fontname\tenit\/},}
44547 \centerline{{\bf\fontname\tenbf}, and}
44548 \centerline{{\sl\fontname\tensl\/}}
44549 \centerline{are used for emphasis.}\vfill}
44551 % Blame: doc@@cygnus.com, 1991.