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 allow
6267 replaying and reverse execution.
6269 This recording method may not be available on all processors.
6272 The process record and replay target can only debug a process that is
6273 already running. Therefore, you need first to start the process with
6274 the @kbd{run} or @kbd{start} commands, and then start the recording
6275 with the @kbd{record @var{method}} command.
6277 Both @code{record @var{method}} and @code{rec @var{method}} are
6278 aliases of @code{target record-@var{method}}.
6280 @cindex displaced stepping, and process record and replay
6281 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6282 will be automatically disabled when process record and replay target
6283 is started. That's because the process record and replay target
6284 doesn't support displaced stepping.
6286 @cindex non-stop mode, and process record and replay
6287 @cindex asynchronous execution, and process record and replay
6288 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6289 the asynchronous execution mode (@pxref{Background Execution}), not
6290 all recording methods are available. The @code{full} recording method
6291 does not support these two modes.
6296 Stop the process record and replay target. When process record and
6297 replay target stops, the entire execution log will be deleted and the
6298 inferior will either be terminated, or will remain in its final state.
6300 When you stop the process record and replay target in record mode (at
6301 the end of the execution log), the inferior will be stopped at the
6302 next instruction that would have been recorded. In other words, if
6303 you record for a while and then stop recording, the inferior process
6304 will be left in the same state as if the recording never happened.
6306 On the other hand, if the process record and replay target is stopped
6307 while in replay mode (that is, not at the end of the execution log,
6308 but at some earlier point), the inferior process will become ``live''
6309 at that earlier state, and it will then be possible to continue the
6310 usual ``live'' debugging of the process from that state.
6312 When the inferior process exits, or @value{GDBN} detaches from it,
6313 process record and replay target will automatically stop itself.
6317 Go to a specific location in the execution log. There are several
6318 ways to specify the location to go to:
6321 @item record goto begin
6322 @itemx record goto start
6323 Go to the beginning of the execution log.
6325 @item record goto end
6326 Go to the end of the execution log.
6328 @item record goto @var{n}
6329 Go to instruction number @var{n} in the execution log.
6333 @item record save @var{filename}
6334 Save the execution log to a file @file{@var{filename}}.
6335 Default filename is @file{gdb_record.@var{process_id}}, where
6336 @var{process_id} is the process ID of the inferior.
6338 This command may not be available for all recording methods.
6340 @kindex record restore
6341 @item record restore @var{filename}
6342 Restore the execution log from a file @file{@var{filename}}.
6343 File must have been created with @code{record save}.
6345 @kindex set record full
6346 @item set record full insn-number-max @var{limit}
6347 @itemx set record full insn-number-max unlimited
6348 Set the limit of instructions to be recorded for the @code{full}
6349 recording method. Default value is 200000.
6351 If @var{limit} is a positive number, then @value{GDBN} will start
6352 deleting instructions from the log once the number of the record
6353 instructions becomes greater than @var{limit}. For every new recorded
6354 instruction, @value{GDBN} will delete the earliest recorded
6355 instruction to keep the number of recorded instructions at the limit.
6356 (Since deleting recorded instructions loses information, @value{GDBN}
6357 lets you control what happens when the limit is reached, by means of
6358 the @code{stop-at-limit} option, described below.)
6360 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6361 delete recorded instructions from the execution log. The number of
6362 recorded instructions is limited only by the available memory.
6364 @kindex show record full
6365 @item show record full insn-number-max
6366 Show the limit of instructions to be recorded with the @code{full}
6369 @item set record full stop-at-limit
6370 Control the behavior of the @code{full} recording method when the
6371 number of recorded instructions reaches the limit. If ON (the
6372 default), @value{GDBN} will stop when the limit is reached for the
6373 first time and ask you whether you want to stop the inferior or
6374 continue running it and recording the execution log. If you decide
6375 to continue recording, each new recorded instruction will cause the
6376 oldest one to be deleted.
6378 If this option is OFF, @value{GDBN} will automatically delete the
6379 oldest record to make room for each new one, without asking.
6381 @item show record full stop-at-limit
6382 Show the current setting of @code{stop-at-limit}.
6384 @item set record full memory-query
6385 Control the behavior when @value{GDBN} is unable to record memory
6386 changes caused by an instruction for the @code{full} recording method.
6387 If ON, @value{GDBN} will query whether to stop the inferior in that
6390 If this option is OFF (the default), @value{GDBN} will automatically
6391 ignore the effect of such instructions on memory. Later, when
6392 @value{GDBN} replays this execution log, it will mark the log of this
6393 instruction as not accessible, and it will not affect the replay
6396 @item show record full memory-query
6397 Show the current setting of @code{memory-query}.
6401 Show various statistics about the recording depending on the recording
6406 For the @code{full} recording method, it shows the state of process
6407 record and its in-memory execution log buffer, including:
6411 Whether in record mode or replay mode.
6413 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6415 Highest recorded instruction number.
6417 Current instruction about to be replayed (if in replay mode).
6419 Number of instructions contained in the execution log.
6421 Maximum number of instructions that may be contained in the execution log.
6425 For the @code{btrace} recording method, it shows the number of
6426 instructions that have been recorded and the number of blocks of
6427 sequential control-flow that is formed by the recorded instructions.
6430 @kindex record delete
6433 When record target runs in replay mode (``in the past''), delete the
6434 subsequent execution log and begin to record a new execution log starting
6435 from the current address. This means you will abandon the previously
6436 recorded ``future'' and begin recording a new ``future''.
6438 @kindex record instruction-history
6439 @kindex rec instruction-history
6440 @item record instruction-history
6441 Disassembles instructions from the recorded execution log. By
6442 default, ten instructions are disassembled. This can be changed using
6443 the @code{set record instruction-history-size} command. Instructions
6444 are printed in execution order. There are several ways to specify
6445 what part of the execution log to disassemble:
6448 @item record instruction-history @var{insn}
6449 Disassembles ten instructions starting from instruction number
6452 @item record instruction-history @var{insn}, +/-@var{n}
6453 Disassembles @var{n} instructions around instruction number
6454 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
6455 @var{n} instructions after instruction number @var{insn}. If
6456 @var{n} is preceded with @code{-}, disassembles @var{n}
6457 instructions before instruction number @var{insn}.
6459 @item record instruction-history
6460 Disassembles ten more instructions after the last disassembly.
6462 @item record instruction-history -
6463 Disassembles ten more instructions before the last disassembly.
6465 @item record instruction-history @var{begin} @var{end}
6466 Disassembles instructions beginning with instruction number
6467 @var{begin} until instruction number @var{end}. The instruction
6468 number @var{end} is included.
6471 This command may not be available for all recording methods.
6474 @item set record instruction-history-size @var{size}
6475 @itemx set record instruction-history-size unlimited
6476 Define how many instructions to disassemble in the @code{record
6477 instruction-history} command. The default value is 10.
6478 A @var{size} of @code{unlimited} means unlimited instructions.
6481 @item show record instruction-history-size
6482 Show how many instructions to disassemble in the @code{record
6483 instruction-history} command.
6485 @kindex record function-call-history
6486 @kindex rec function-call-history
6487 @item record function-call-history
6488 Prints the execution history at function granularity. It prints one
6489 line for each sequence of instructions that belong to the same
6490 function giving the name of that function, the source lines
6491 for this instruction sequence (if the @code{/l} modifier is
6492 specified), and the instructions numbers that form the sequence (if
6493 the @code{/i} modifier is specified). The function names are indented
6494 to reflect the call stack depth if the @code{/c} modifier is
6495 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
6499 (@value{GDBP}) @b{list 1, 10}
6510 (@value{GDBP}) @b{record function-call-history /ilc}
6511 1 bar inst 1,4 at foo.c:6,8
6512 2 foo inst 5,10 at foo.c:2,3
6513 3 bar inst 11,13 at foo.c:9,10
6516 By default, ten lines are printed. This can be changed using the
6517 @code{set record function-call-history-size} command. Functions are
6518 printed in execution order. There are several ways to specify what
6522 @item record function-call-history @var{func}
6523 Prints ten functions starting from function number @var{func}.
6525 @item record function-call-history @var{func}, +/-@var{n}
6526 Prints @var{n} functions around function number @var{func}. If
6527 @var{n} is preceded with @code{+}, prints @var{n} functions after
6528 function number @var{func}. If @var{n} is preceded with @code{-},
6529 prints @var{n} functions before function number @var{func}.
6531 @item record function-call-history
6532 Prints ten more functions after the last ten-line print.
6534 @item record function-call-history -
6535 Prints ten more functions before the last ten-line print.
6537 @item record function-call-history @var{begin} @var{end}
6538 Prints functions beginning with function number @var{begin} until
6539 function number @var{end}. The function number @var{end} is included.
6542 This command may not be available for all recording methods.
6544 @item set record function-call-history-size @var{size}
6545 @itemx set record function-call-history-size unlimited
6546 Define how many lines to print in the
6547 @code{record function-call-history} command. The default value is 10.
6548 A size of @code{unlimited} means unlimited lines.
6550 @item show record function-call-history-size
6551 Show how many lines to print in the
6552 @code{record function-call-history} command.
6557 @chapter Examining the Stack
6559 When your program has stopped, the first thing you need to know is where it
6560 stopped and how it got there.
6563 Each time your program performs a function call, information about the call
6565 That information includes the location of the call in your program,
6566 the arguments of the call,
6567 and the local variables of the function being called.
6568 The information is saved in a block of data called a @dfn{stack frame}.
6569 The stack frames are allocated in a region of memory called the @dfn{call
6572 When your program stops, the @value{GDBN} commands for examining the
6573 stack allow you to see all of this information.
6575 @cindex selected frame
6576 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6577 @value{GDBN} commands refer implicitly to the selected frame. In
6578 particular, whenever you ask @value{GDBN} for the value of a variable in
6579 your program, the value is found in the selected frame. There are
6580 special @value{GDBN} commands to select whichever frame you are
6581 interested in. @xref{Selection, ,Selecting a Frame}.
6583 When your program stops, @value{GDBN} automatically selects the
6584 currently executing frame and describes it briefly, similar to the
6585 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6588 * Frames:: Stack frames
6589 * Backtrace:: Backtraces
6590 * Frame Filter Management:: Managing frame filters
6591 * Selection:: Selecting a frame
6592 * Frame Info:: Information on a frame
6597 @section Stack Frames
6599 @cindex frame, definition
6601 The call stack is divided up into contiguous pieces called @dfn{stack
6602 frames}, or @dfn{frames} for short; each frame is the data associated
6603 with one call to one function. The frame contains the arguments given
6604 to the function, the function's local variables, and the address at
6605 which the function is executing.
6607 @cindex initial frame
6608 @cindex outermost frame
6609 @cindex innermost frame
6610 When your program is started, the stack has only one frame, that of the
6611 function @code{main}. This is called the @dfn{initial} frame or the
6612 @dfn{outermost} frame. Each time a function is called, a new frame is
6613 made. Each time a function returns, the frame for that function invocation
6614 is eliminated. If a function is recursive, there can be many frames for
6615 the same function. The frame for the function in which execution is
6616 actually occurring is called the @dfn{innermost} frame. This is the most
6617 recently created of all the stack frames that still exist.
6619 @cindex frame pointer
6620 Inside your program, stack frames are identified by their addresses. A
6621 stack frame consists of many bytes, each of which has its own address; each
6622 kind of computer has a convention for choosing one byte whose
6623 address serves as the address of the frame. Usually this address is kept
6624 in a register called the @dfn{frame pointer register}
6625 (@pxref{Registers, $fp}) while execution is going on in that frame.
6627 @cindex frame number
6628 @value{GDBN} assigns numbers to all existing stack frames, starting with
6629 zero for the innermost frame, one for the frame that called it,
6630 and so on upward. These numbers do not really exist in your program;
6631 they are assigned by @value{GDBN} to give you a way of designating stack
6632 frames in @value{GDBN} commands.
6634 @c The -fomit-frame-pointer below perennially causes hbox overflow
6635 @c underflow problems.
6636 @cindex frameless execution
6637 Some compilers provide a way to compile functions so that they operate
6638 without stack frames. (For example, the @value{NGCC} option
6640 @samp{-fomit-frame-pointer}
6642 generates functions without a frame.)
6643 This is occasionally done with heavily used library functions to save
6644 the frame setup time. @value{GDBN} has limited facilities for dealing
6645 with these function invocations. If the innermost function invocation
6646 has no stack frame, @value{GDBN} nevertheless regards it as though
6647 it had a separate frame, which is numbered zero as usual, allowing
6648 correct tracing of the function call chain. However, @value{GDBN} has
6649 no provision for frameless functions elsewhere in the stack.
6652 @kindex frame@r{, command}
6653 @cindex current stack frame
6654 @item frame @var{args}
6655 The @code{frame} command allows you to move from one stack frame to another,
6656 and to print the stack frame you select. @var{args} may be either the
6657 address of the frame or the stack frame number. Without an argument,
6658 @code{frame} prints the current stack frame.
6660 @kindex select-frame
6661 @cindex selecting frame silently
6663 The @code{select-frame} command allows you to move from one stack frame
6664 to another without printing the frame. This is the silent version of
6672 @cindex call stack traces
6673 A backtrace is a summary of how your program got where it is. It shows one
6674 line per frame, for many frames, starting with the currently executing
6675 frame (frame zero), followed by its caller (frame one), and on up the
6678 @anchor{backtrace-command}
6681 @kindex bt @r{(@code{backtrace})}
6684 Print a backtrace of the entire stack: one line per frame for all
6685 frames in the stack.
6687 You can stop the backtrace at any time by typing the system interrupt
6688 character, normally @kbd{Ctrl-c}.
6690 @item backtrace @var{n}
6692 Similar, but print only the innermost @var{n} frames.
6694 @item backtrace -@var{n}
6696 Similar, but print only the outermost @var{n} frames.
6698 @item backtrace full
6700 @itemx bt full @var{n}
6701 @itemx bt full -@var{n}
6702 Print the values of the local variables also. @var{n} specifies the
6703 number of frames to print, as described above.
6705 @item backtrace no-filters
6706 @itemx bt no-filters
6707 @itemx bt no-filters @var{n}
6708 @itemx bt no-filters -@var{n}
6709 @itemx bt no-filters full
6710 @itemx bt no-filters full @var{n}
6711 @itemx bt no-filters full -@var{n}
6712 Do not run Python frame filters on this backtrace. @xref{Frame
6713 Filter API}, for more information. Additionally use @ref{disable
6714 frame-filter all} to turn off all frame filters. This is only
6715 relevant when @value{GDBN} has been configured with @code{Python}
6721 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6722 are additional aliases for @code{backtrace}.
6724 @cindex multiple threads, backtrace
6725 In a multi-threaded program, @value{GDBN} by default shows the
6726 backtrace only for the current thread. To display the backtrace for
6727 several or all of the threads, use the command @code{thread apply}
6728 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6729 apply all backtrace}, @value{GDBN} will display the backtrace for all
6730 the threads; this is handy when you debug a core dump of a
6731 multi-threaded program.
6733 Each line in the backtrace shows the frame number and the function name.
6734 The program counter value is also shown---unless you use @code{set
6735 print address off}. The backtrace also shows the source file name and
6736 line number, as well as the arguments to the function. The program
6737 counter value is omitted if it is at the beginning of the code for that
6740 Here is an example of a backtrace. It was made with the command
6741 @samp{bt 3}, so it shows the innermost three frames.
6745 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6747 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
6748 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
6750 (More stack frames follow...)
6755 The display for frame zero does not begin with a program counter
6756 value, indicating that your program has stopped at the beginning of the
6757 code for line @code{993} of @code{builtin.c}.
6760 The value of parameter @code{data} in frame 1 has been replaced by
6761 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
6762 only if it is a scalar (integer, pointer, enumeration, etc). See command
6763 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
6764 on how to configure the way function parameter values are printed.
6766 @cindex optimized out, in backtrace
6767 @cindex function call arguments, optimized out
6768 If your program was compiled with optimizations, some compilers will
6769 optimize away arguments passed to functions if those arguments are
6770 never used after the call. Such optimizations generate code that
6771 passes arguments through registers, but doesn't store those arguments
6772 in the stack frame. @value{GDBN} has no way of displaying such
6773 arguments in stack frames other than the innermost one. Here's what
6774 such a backtrace might look like:
6778 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6780 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6781 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6783 (More stack frames follow...)
6788 The values of arguments that were not saved in their stack frames are
6789 shown as @samp{<optimized out>}.
6791 If you need to display the values of such optimized-out arguments,
6792 either deduce that from other variables whose values depend on the one
6793 you are interested in, or recompile without optimizations.
6795 @cindex backtrace beyond @code{main} function
6796 @cindex program entry point
6797 @cindex startup code, and backtrace
6798 Most programs have a standard user entry point---a place where system
6799 libraries and startup code transition into user code. For C this is
6800 @code{main}@footnote{
6801 Note that embedded programs (the so-called ``free-standing''
6802 environment) are not required to have a @code{main} function as the
6803 entry point. They could even have multiple entry points.}.
6804 When @value{GDBN} finds the entry function in a backtrace
6805 it will terminate the backtrace, to avoid tracing into highly
6806 system-specific (and generally uninteresting) code.
6808 If you need to examine the startup code, or limit the number of levels
6809 in a backtrace, you can change this behavior:
6812 @item set backtrace past-main
6813 @itemx set backtrace past-main on
6814 @kindex set backtrace
6815 Backtraces will continue past the user entry point.
6817 @item set backtrace past-main off
6818 Backtraces will stop when they encounter the user entry point. This is the
6821 @item show backtrace past-main
6822 @kindex show backtrace
6823 Display the current user entry point backtrace policy.
6825 @item set backtrace past-entry
6826 @itemx set backtrace past-entry on
6827 Backtraces will continue past the internal entry point of an application.
6828 This entry point is encoded by the linker when the application is built,
6829 and is likely before the user entry point @code{main} (or equivalent) is called.
6831 @item set backtrace past-entry off
6832 Backtraces will stop when they encounter the internal entry point of an
6833 application. This is the default.
6835 @item show backtrace past-entry
6836 Display the current internal entry point backtrace policy.
6838 @item set backtrace limit @var{n}
6839 @itemx set backtrace limit 0
6840 @itemx set backtrace limit unlimited
6841 @cindex backtrace limit
6842 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
6843 or zero means unlimited levels.
6845 @item show backtrace limit
6846 Display the current limit on backtrace levels.
6849 You can control how file names are displayed.
6852 @item set filename-display
6853 @itemx set filename-display relative
6854 @cindex filename-display
6855 Display file names relative to the compilation directory. This is the default.
6857 @item set filename-display basename
6858 Display only basename of a filename.
6860 @item set filename-display absolute
6861 Display an absolute filename.
6863 @item show filename-display
6864 Show the current way to display filenames.
6867 @node Frame Filter Management
6868 @section Management of Frame Filters.
6869 @cindex managing frame filters
6871 Frame filters are Python based utilities to manage and decorate the
6872 output of frames. @xref{Frame Filter API}, for further information.
6874 Managing frame filters is performed by several commands available
6875 within @value{GDBN}, detailed here.
6878 @kindex info frame-filter
6879 @item info frame-filter
6880 Print a list of installed frame filters from all dictionaries, showing
6881 their name, priority and enabled status.
6883 @kindex disable frame-filter
6884 @anchor{disable frame-filter all}
6885 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
6886 Disable a frame filter in the dictionary matching
6887 @var{filter-dictionary}, or @code{all}, and @var{filter-name}.
6888 @var{filter-dictionary} may be @code{all}, @code{global},
6889 @code{progspace} or the name of the object file where the frame filter
6890 dictionary resides. When @code{all} is specified, all frame filters
6891 across all dictionaries are disabled. @var{filter-name} is the name
6892 of the frame filter and is used when @code{all} is not the option for
6893 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
6894 may be enabled again later.
6896 @kindex enable frame-filter
6897 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
6898 Enable a frame filter in the dictionary matching
6899 @var{filter-dictionary}, or @code{all}, and @var{filter-name}.
6900 @var{filter-dictionary} may be @code{all}, @code{global},
6901 @code{progspace} or the name of the object file where the frame filter
6902 dictionary resides. When @code{all} is specified, all frame filters across
6903 all dictionaries are enabled. @var{filter-name} is the name of the frame
6904 filter and is used when @code{all} is not the option for
6905 @var{filter-dictionary}.
6910 (gdb) info frame-filter
6912 global frame-filters:
6913 Priority Enabled Name
6914 1000 No PrimaryFunctionFilter
6917 progspace /build/test frame-filters:
6918 Priority Enabled Name
6919 100 Yes ProgspaceFilter
6921 objfile /build/test frame-filters:
6922 Priority Enabled Name
6923 999 Yes BuildProgra Filter
6925 (gdb) disable frame-filter /build/test BuildProgramFilter
6926 (gdb) info frame-filter
6928 global frame-filters:
6929 Priority Enabled Name
6930 1000 No PrimaryFunctionFilter
6933 progspace /build/test frame-filters:
6934 Priority Enabled Name
6935 100 Yes ProgspaceFilter
6937 objfile /build/test frame-filters:
6938 Priority Enabled Name
6939 999 No BuildProgramFilter
6941 (gdb) enable frame-filter global PrimaryFunctionFilter
6942 (gdb) info frame-filter
6944 global frame-filters:
6945 Priority Enabled Name
6946 1000 Yes PrimaryFunctionFilter
6949 progspace /build/test frame-filters:
6950 Priority Enabled Name
6951 100 Yes ProgspaceFilter
6953 objfile /build/test frame-filters:
6954 Priority Enabled Name
6955 999 No BuildProgramFilter
6958 @kindex set frame-filter priority
6959 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
6960 Set the @var{priority} of a frame filter in the dictionary matching
6961 @var{filter-dictionary}, and the frame filter name matching
6962 @var{filter-name}. @var{filter-dictionary} may be @code{global},
6963 @code{progspace} or the name of the object file where the frame filter
6964 dictionary resides. @var{priority} is an integer.
6966 @kindex show frame-filter priority
6967 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
6968 Show the @var{priority} of a frame filter in the dictionary matching
6969 @var{filter-dictionary}, and the frame filter name matching
6970 @var{filter-name}. @var{filter-dictionary} may be @code{global},
6971 @code{progspace} or the name of the object file where the frame filter
6977 (gdb) info frame-filter
6979 global frame-filters:
6980 Priority Enabled Name
6981 1000 Yes PrimaryFunctionFilter
6984 progspace /build/test frame-filters:
6985 Priority Enabled Name
6986 100 Yes ProgspaceFilter
6988 objfile /build/test frame-filters:
6989 Priority Enabled Name
6990 999 No BuildProgramFilter
6992 (gdb) set frame-filter priority global Reverse 50
6993 (gdb) info frame-filter
6995 global frame-filters:
6996 Priority Enabled Name
6997 1000 Yes PrimaryFunctionFilter
7000 progspace /build/test frame-filters:
7001 Priority Enabled Name
7002 100 Yes ProgspaceFilter
7004 objfile /build/test frame-filters:
7005 Priority Enabled Name
7006 999 No BuildProgramFilter
7011 @section Selecting a Frame
7013 Most commands for examining the stack and other data in your program work on
7014 whichever stack frame is selected at the moment. Here are the commands for
7015 selecting a stack frame; all of them finish by printing a brief description
7016 of the stack frame just selected.
7019 @kindex frame@r{, selecting}
7020 @kindex f @r{(@code{frame})}
7023 Select frame number @var{n}. Recall that frame zero is the innermost
7024 (currently executing) frame, frame one is the frame that called the
7025 innermost one, and so on. The highest-numbered frame is the one for
7028 @item frame @var{addr}
7030 Select the frame at address @var{addr}. This is useful mainly if the
7031 chaining of stack frames has been damaged by a bug, making it
7032 impossible for @value{GDBN} to assign numbers properly to all frames. In
7033 addition, this can be useful when your program has multiple stacks and
7034 switches between them.
7036 On the SPARC architecture, @code{frame} needs two addresses to
7037 select an arbitrary frame: a frame pointer and a stack pointer.
7039 On the @acronym{MIPS} and Alpha architecture, it needs two addresses: a stack
7040 pointer and a program counter.
7042 On the 29k architecture, it needs three addresses: a register stack
7043 pointer, a program counter, and a memory stack pointer.
7047 Move @var{n} frames up the stack. For positive numbers @var{n}, this
7048 advances toward the outermost frame, to higher frame numbers, to frames
7049 that have existed longer. @var{n} defaults to one.
7052 @kindex do @r{(@code{down})}
7054 Move @var{n} frames down the stack. For positive numbers @var{n}, this
7055 advances toward the innermost frame, to lower frame numbers, to frames
7056 that were created more recently. @var{n} defaults to one. You may
7057 abbreviate @code{down} as @code{do}.
7060 All of these commands end by printing two lines of output describing the
7061 frame. The first line shows the frame number, the function name, the
7062 arguments, and the source file and line number of execution in that
7063 frame. The second line shows the text of that source line.
7071 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7073 10 read_input_file (argv[i]);
7077 After such a printout, the @code{list} command with no arguments
7078 prints ten lines centered on the point of execution in the frame.
7079 You can also edit the program at the point of execution with your favorite
7080 editing program by typing @code{edit}.
7081 @xref{List, ,Printing Source Lines},
7085 @kindex down-silently
7087 @item up-silently @var{n}
7088 @itemx down-silently @var{n}
7089 These two commands are variants of @code{up} and @code{down},
7090 respectively; they differ in that they do their work silently, without
7091 causing display of the new frame. They are intended primarily for use
7092 in @value{GDBN} command scripts, where the output might be unnecessary and
7097 @section Information About a Frame
7099 There are several other commands to print information about the selected
7105 When used without any argument, this command does not change which
7106 frame is selected, but prints a brief description of the currently
7107 selected stack frame. It can be abbreviated @code{f}. With an
7108 argument, this command is used to select a stack frame.
7109 @xref{Selection, ,Selecting a Frame}.
7112 @kindex info f @r{(@code{info frame})}
7115 This command prints a verbose description of the selected stack frame,
7120 the address of the frame
7122 the address of the next frame down (called by this frame)
7124 the address of the next frame up (caller of this frame)
7126 the language in which the source code corresponding to this frame is written
7128 the address of the frame's arguments
7130 the address of the frame's local variables
7132 the program counter saved in it (the address of execution in the caller frame)
7134 which registers were saved in the frame
7137 @noindent The verbose description is useful when
7138 something has gone wrong that has made the stack format fail to fit
7139 the usual conventions.
7141 @item info frame @var{addr}
7142 @itemx info f @var{addr}
7143 Print a verbose description of the frame at address @var{addr}, without
7144 selecting that frame. The selected frame remains unchanged by this
7145 command. This requires the same kind of address (more than one for some
7146 architectures) that you specify in the @code{frame} command.
7147 @xref{Selection, ,Selecting a Frame}.
7151 Print the arguments of the selected frame, each on a separate line.
7155 Print the local variables of the selected frame, each on a separate
7156 line. These are all variables (declared either static or automatic)
7157 accessible at the point of execution of the selected frame.
7163 @chapter Examining Source Files
7165 @value{GDBN} can print parts of your program's source, since the debugging
7166 information recorded in the program tells @value{GDBN} what source files were
7167 used to build it. When your program stops, @value{GDBN} spontaneously prints
7168 the line where it stopped. Likewise, when you select a stack frame
7169 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
7170 execution in that frame has stopped. You can print other portions of
7171 source files by explicit command.
7173 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
7174 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
7175 @value{GDBN} under @sc{gnu} Emacs}.
7178 * List:: Printing source lines
7179 * Specify Location:: How to specify code locations
7180 * Edit:: Editing source files
7181 * Search:: Searching source files
7182 * Source Path:: Specifying source directories
7183 * Machine Code:: Source and machine code
7187 @section Printing Source Lines
7190 @kindex l @r{(@code{list})}
7191 To print lines from a source file, use the @code{list} command
7192 (abbreviated @code{l}). By default, ten lines are printed.
7193 There are several ways to specify what part of the file you want to
7194 print; see @ref{Specify Location}, for the full list.
7196 Here are the forms of the @code{list} command most commonly used:
7199 @item list @var{linenum}
7200 Print lines centered around line number @var{linenum} in the
7201 current source file.
7203 @item list @var{function}
7204 Print lines centered around the beginning of function
7208 Print more lines. If the last lines printed were printed with a
7209 @code{list} command, this prints lines following the last lines
7210 printed; however, if the last line printed was a solitary line printed
7211 as part of displaying a stack frame (@pxref{Stack, ,Examining the
7212 Stack}), this prints lines centered around that line.
7215 Print lines just before the lines last printed.
7218 @cindex @code{list}, how many lines to display
7219 By default, @value{GDBN} prints ten source lines with any of these forms of
7220 the @code{list} command. You can change this using @code{set listsize}:
7223 @kindex set listsize
7224 @item set listsize @var{count}
7225 @itemx set listsize unlimited
7226 Make the @code{list} command display @var{count} source lines (unless
7227 the @code{list} argument explicitly specifies some other number).
7228 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
7230 @kindex show listsize
7232 Display the number of lines that @code{list} prints.
7235 Repeating a @code{list} command with @key{RET} discards the argument,
7236 so it is equivalent to typing just @code{list}. This is more useful
7237 than listing the same lines again. An exception is made for an
7238 argument of @samp{-}; that argument is preserved in repetition so that
7239 each repetition moves up in the source file.
7241 In general, the @code{list} command expects you to supply zero, one or two
7242 @dfn{linespecs}. Linespecs specify source lines; there are several ways
7243 of writing them (@pxref{Specify Location}), but the effect is always
7244 to specify some source line.
7246 Here is a complete description of the possible arguments for @code{list}:
7249 @item list @var{linespec}
7250 Print lines centered around the line specified by @var{linespec}.
7252 @item list @var{first},@var{last}
7253 Print lines from @var{first} to @var{last}. Both arguments are
7254 linespecs. When a @code{list} command has two linespecs, and the
7255 source file of the second linespec is omitted, this refers to
7256 the same source file as the first linespec.
7258 @item list ,@var{last}
7259 Print lines ending with @var{last}.
7261 @item list @var{first},
7262 Print lines starting with @var{first}.
7265 Print lines just after the lines last printed.
7268 Print lines just before the lines last printed.
7271 As described in the preceding table.
7274 @node Specify Location
7275 @section Specifying a Location
7276 @cindex specifying location
7279 Several @value{GDBN} commands accept arguments that specify a location
7280 of your program's code. Since @value{GDBN} is a source-level
7281 debugger, a location usually specifies some line in the source code;
7282 for that reason, locations are also known as @dfn{linespecs}.
7284 Here are all the different ways of specifying a code location that
7285 @value{GDBN} understands:
7289 Specifies the line number @var{linenum} of the current source file.
7292 @itemx +@var{offset}
7293 Specifies the line @var{offset} lines before or after the @dfn{current
7294 line}. For the @code{list} command, the current line is the last one
7295 printed; for the breakpoint commands, this is the line at which
7296 execution stopped in the currently selected @dfn{stack frame}
7297 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7298 used as the second of the two linespecs in a @code{list} command,
7299 this specifies the line @var{offset} lines up or down from the first
7302 @item @var{filename}:@var{linenum}
7303 Specifies the line @var{linenum} in the source file @var{filename}.
7304 If @var{filename} is a relative file name, then it will match any
7305 source file name with the same trailing components. For example, if
7306 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7307 name of @file{/build/trunk/gcc/expr.c}, but not
7308 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7310 @item @var{function}
7311 Specifies the line that begins the body of the function @var{function}.
7312 For example, in C, this is the line with the open brace.
7314 @item @var{function}:@var{label}
7315 Specifies the line where @var{label} appears in @var{function}.
7317 @item @var{filename}:@var{function}
7318 Specifies the line that begins the body of the function @var{function}
7319 in the file @var{filename}. You only need the file name with a
7320 function name to avoid ambiguity when there are identically named
7321 functions in different source files.
7324 Specifies the line at which the label named @var{label} appears.
7325 @value{GDBN} searches for the label in the function corresponding to
7326 the currently selected stack frame. If there is no current selected
7327 stack frame (for instance, if the inferior is not running), then
7328 @value{GDBN} will not search for a label.
7330 @item *@var{address}
7331 Specifies the program address @var{address}. For line-oriented
7332 commands, such as @code{list} and @code{edit}, this specifies a source
7333 line that contains @var{address}. For @code{break} and other
7334 breakpoint oriented commands, this can be used to set breakpoints in
7335 parts of your program which do not have debugging information or
7338 Here @var{address} may be any expression valid in the current working
7339 language (@pxref{Languages, working language}) that specifies a code
7340 address. In addition, as a convenience, @value{GDBN} extends the
7341 semantics of expressions used in locations to cover the situations
7342 that frequently happen during debugging. Here are the various forms
7346 @item @var{expression}
7347 Any expression valid in the current working language.
7349 @item @var{funcaddr}
7350 An address of a function or procedure derived from its name. In C,
7351 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
7352 simply the function's name @var{function} (and actually a special case
7353 of a valid expression). In Pascal and Modula-2, this is
7354 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
7355 (although the Pascal form also works).
7357 This form specifies the address of the function's first instruction,
7358 before the stack frame and arguments have been set up.
7360 @item '@var{filename}'::@var{funcaddr}
7361 Like @var{funcaddr} above, but also specifies the name of the source
7362 file explicitly. This is useful if the name of the function does not
7363 specify the function unambiguously, e.g., if there are several
7364 functions with identical names in different source files.
7367 @cindex breakpoint at static probe point
7368 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7369 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7370 applications to embed static probes. @xref{Static Probe Points}, for more
7371 information on finding and using static probes. This form of linespec
7372 specifies the location of such a static probe.
7374 If @var{objfile} is given, only probes coming from that shared library
7375 or executable matching @var{objfile} as a regular expression are considered.
7376 If @var{provider} is given, then only probes from that provider are considered.
7377 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7378 each one of those probes.
7384 @section Editing Source Files
7385 @cindex editing source files
7388 @kindex e @r{(@code{edit})}
7389 To edit the lines in a source file, use the @code{edit} command.
7390 The editing program of your choice
7391 is invoked with the current line set to
7392 the active line in the program.
7393 Alternatively, there are several ways to specify what part of the file you
7394 want to print if you want to see other parts of the program:
7397 @item edit @var{location}
7398 Edit the source file specified by @code{location}. Editing starts at
7399 that @var{location}, e.g., at the specified source line of the
7400 specified file. @xref{Specify Location}, for all the possible forms
7401 of the @var{location} argument; here are the forms of the @code{edit}
7402 command most commonly used:
7405 @item edit @var{number}
7406 Edit the current source file with @var{number} as the active line number.
7408 @item edit @var{function}
7409 Edit the file containing @var{function} at the beginning of its definition.
7414 @subsection Choosing your Editor
7415 You can customize @value{GDBN} to use any editor you want
7417 The only restriction is that your editor (say @code{ex}), recognizes the
7418 following command-line syntax:
7420 ex +@var{number} file
7422 The optional numeric value +@var{number} specifies the number of the line in
7423 the file where to start editing.}.
7424 By default, it is @file{@value{EDITOR}}, but you can change this
7425 by setting the environment variable @code{EDITOR} before using
7426 @value{GDBN}. For example, to configure @value{GDBN} to use the
7427 @code{vi} editor, you could use these commands with the @code{sh} shell:
7433 or in the @code{csh} shell,
7435 setenv EDITOR /usr/bin/vi
7440 @section Searching Source Files
7441 @cindex searching source files
7443 There are two commands for searching through the current source file for a
7448 @kindex forward-search
7449 @kindex fo @r{(@code{forward-search})}
7450 @item forward-search @var{regexp}
7451 @itemx search @var{regexp}
7452 The command @samp{forward-search @var{regexp}} checks each line,
7453 starting with the one following the last line listed, for a match for
7454 @var{regexp}. It lists the line that is found. You can use the
7455 synonym @samp{search @var{regexp}} or abbreviate the command name as
7458 @kindex reverse-search
7459 @item reverse-search @var{regexp}
7460 The command @samp{reverse-search @var{regexp}} checks each line, starting
7461 with the one before the last line listed and going backward, for a match
7462 for @var{regexp}. It lists the line that is found. You can abbreviate
7463 this command as @code{rev}.
7467 @section Specifying Source Directories
7470 @cindex directories for source files
7471 Executable programs sometimes do not record the directories of the source
7472 files from which they were compiled, just the names. Even when they do,
7473 the directories could be moved between the compilation and your debugging
7474 session. @value{GDBN} has a list of directories to search for source files;
7475 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
7476 it tries all the directories in the list, in the order they are present
7477 in the list, until it finds a file with the desired name.
7479 For example, suppose an executable references the file
7480 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
7481 @file{/mnt/cross}. The file is first looked up literally; if this
7482 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
7483 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
7484 message is printed. @value{GDBN} does not look up the parts of the
7485 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
7486 Likewise, the subdirectories of the source path are not searched: if
7487 the source path is @file{/mnt/cross}, and the binary refers to
7488 @file{foo.c}, @value{GDBN} would not find it under
7489 @file{/mnt/cross/usr/src/foo-1.0/lib}.
7491 Plain file names, relative file names with leading directories, file
7492 names containing dots, etc.@: are all treated as described above; for
7493 instance, if the source path is @file{/mnt/cross}, and the source file
7494 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
7495 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
7496 that---@file{/mnt/cross/foo.c}.
7498 Note that the executable search path is @emph{not} used to locate the
7501 Whenever you reset or rearrange the source path, @value{GDBN} clears out
7502 any information it has cached about where source files are found and where
7503 each line is in the file.
7507 When you start @value{GDBN}, its source path includes only @samp{cdir}
7508 and @samp{cwd}, in that order.
7509 To add other directories, use the @code{directory} command.
7511 The search path is used to find both program source files and @value{GDBN}
7512 script files (read using the @samp{-command} option and @samp{source} command).
7514 In addition to the source path, @value{GDBN} provides a set of commands
7515 that manage a list of source path substitution rules. A @dfn{substitution
7516 rule} specifies how to rewrite source directories stored in the program's
7517 debug information in case the sources were moved to a different
7518 directory between compilation and debugging. A rule is made of
7519 two strings, the first specifying what needs to be rewritten in
7520 the path, and the second specifying how it should be rewritten.
7521 In @ref{set substitute-path}, we name these two parts @var{from} and
7522 @var{to} respectively. @value{GDBN} does a simple string replacement
7523 of @var{from} with @var{to} at the start of the directory part of the
7524 source file name, and uses that result instead of the original file
7525 name to look up the sources.
7527 Using the previous example, suppose the @file{foo-1.0} tree has been
7528 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
7529 @value{GDBN} to replace @file{/usr/src} in all source path names with
7530 @file{/mnt/cross}. The first lookup will then be
7531 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
7532 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
7533 substitution rule, use the @code{set substitute-path} command
7534 (@pxref{set substitute-path}).
7536 To avoid unexpected substitution results, a rule is applied only if the
7537 @var{from} part of the directory name ends at a directory separator.
7538 For instance, a rule substituting @file{/usr/source} into
7539 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
7540 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
7541 is applied only at the beginning of the directory name, this rule will
7542 not be applied to @file{/root/usr/source/baz.c} either.
7544 In many cases, you can achieve the same result using the @code{directory}
7545 command. However, @code{set substitute-path} can be more efficient in
7546 the case where the sources are organized in a complex tree with multiple
7547 subdirectories. With the @code{directory} command, you need to add each
7548 subdirectory of your project. If you moved the entire tree while
7549 preserving its internal organization, then @code{set substitute-path}
7550 allows you to direct the debugger to all the sources with one single
7553 @code{set substitute-path} is also more than just a shortcut command.
7554 The source path is only used if the file at the original location no
7555 longer exists. On the other hand, @code{set substitute-path} modifies
7556 the debugger behavior to look at the rewritten location instead. So, if
7557 for any reason a source file that is not relevant to your executable is
7558 located at the original location, a substitution rule is the only
7559 method available to point @value{GDBN} at the new location.
7561 @cindex @samp{--with-relocated-sources}
7562 @cindex default source path substitution
7563 You can configure a default source path substitution rule by
7564 configuring @value{GDBN} with the
7565 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
7566 should be the name of a directory under @value{GDBN}'s configured
7567 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
7568 directory names in debug information under @var{dir} will be adjusted
7569 automatically if the installed @value{GDBN} is moved to a new
7570 location. This is useful if @value{GDBN}, libraries or executables
7571 with debug information and corresponding source code are being moved
7575 @item directory @var{dirname} @dots{}
7576 @item dir @var{dirname} @dots{}
7577 Add directory @var{dirname} to the front of the source path. Several
7578 directory names may be given to this command, separated by @samp{:}
7579 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
7580 part of absolute file names) or
7581 whitespace. You may specify a directory that is already in the source
7582 path; this moves it forward, so @value{GDBN} searches it sooner.
7586 @vindex $cdir@r{, convenience variable}
7587 @vindex $cwd@r{, convenience variable}
7588 @cindex compilation directory
7589 @cindex current directory
7590 @cindex working directory
7591 @cindex directory, current
7592 @cindex directory, compilation
7593 You can use the string @samp{$cdir} to refer to the compilation
7594 directory (if one is recorded), and @samp{$cwd} to refer to the current
7595 working directory. @samp{$cwd} is not the same as @samp{.}---the former
7596 tracks the current working directory as it changes during your @value{GDBN}
7597 session, while the latter is immediately expanded to the current
7598 directory at the time you add an entry to the source path.
7601 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
7603 @c RET-repeat for @code{directory} is explicitly disabled, but since
7604 @c repeating it would be a no-op we do not say that. (thanks to RMS)
7606 @item set directories @var{path-list}
7607 @kindex set directories
7608 Set the source path to @var{path-list}.
7609 @samp{$cdir:$cwd} are added if missing.
7611 @item show directories
7612 @kindex show directories
7613 Print the source path: show which directories it contains.
7615 @anchor{set substitute-path}
7616 @item set substitute-path @var{from} @var{to}
7617 @kindex set substitute-path
7618 Define a source path substitution rule, and add it at the end of the
7619 current list of existing substitution rules. If a rule with the same
7620 @var{from} was already defined, then the old rule is also deleted.
7622 For example, if the file @file{/foo/bar/baz.c} was moved to
7623 @file{/mnt/cross/baz.c}, then the command
7626 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
7630 will tell @value{GDBN} to replace @samp{/usr/src} with
7631 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
7632 @file{baz.c} even though it was moved.
7634 In the case when more than one substitution rule have been defined,
7635 the rules are evaluated one by one in the order where they have been
7636 defined. The first one matching, if any, is selected to perform
7639 For instance, if we had entered the following commands:
7642 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
7643 (@value{GDBP}) set substitute-path /usr/src /mnt/src
7647 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
7648 @file{/mnt/include/defs.h} by using the first rule. However, it would
7649 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
7650 @file{/mnt/src/lib/foo.c}.
7653 @item unset substitute-path [path]
7654 @kindex unset substitute-path
7655 If a path is specified, search the current list of substitution rules
7656 for a rule that would rewrite that path. Delete that rule if found.
7657 A warning is emitted by the debugger if no rule could be found.
7659 If no path is specified, then all substitution rules are deleted.
7661 @item show substitute-path [path]
7662 @kindex show substitute-path
7663 If a path is specified, then print the source path substitution rule
7664 which would rewrite that path, if any.
7666 If no path is specified, then print all existing source path substitution
7671 If your source path is cluttered with directories that are no longer of
7672 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
7673 versions of source. You can correct the situation as follows:
7677 Use @code{directory} with no argument to reset the source path to its default value.
7680 Use @code{directory} with suitable arguments to reinstall the
7681 directories you want in the source path. You can add all the
7682 directories in one command.
7686 @section Source and Machine Code
7687 @cindex source line and its code address
7689 You can use the command @code{info line} to map source lines to program
7690 addresses (and vice versa), and the command @code{disassemble} to display
7691 a range of addresses as machine instructions. You can use the command
7692 @code{set disassemble-next-line} to set whether to disassemble next
7693 source line when execution stops. When run under @sc{gnu} Emacs
7694 mode, the @code{info line} command causes the arrow to point to the
7695 line specified. Also, @code{info line} prints addresses in symbolic form as
7700 @item info line @var{linespec}
7701 Print the starting and ending addresses of the compiled code for
7702 source line @var{linespec}. You can specify source lines in any of
7703 the ways documented in @ref{Specify Location}.
7706 For example, we can use @code{info line} to discover the location of
7707 the object code for the first line of function
7708 @code{m4_changequote}:
7710 @c FIXME: I think this example should also show the addresses in
7711 @c symbolic form, as they usually would be displayed.
7713 (@value{GDBP}) info line m4_changequote
7714 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
7718 @cindex code address and its source line
7719 We can also inquire (using @code{*@var{addr}} as the form for
7720 @var{linespec}) what source line covers a particular address:
7722 (@value{GDBP}) info line *0x63ff
7723 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
7726 @cindex @code{$_} and @code{info line}
7727 @cindex @code{x} command, default address
7728 @kindex x@r{(examine), and} info line
7729 After @code{info line}, the default address for the @code{x} command
7730 is changed to the starting address of the line, so that @samp{x/i} is
7731 sufficient to begin examining the machine code (@pxref{Memory,
7732 ,Examining Memory}). Also, this address is saved as the value of the
7733 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
7738 @cindex assembly instructions
7739 @cindex instructions, assembly
7740 @cindex machine instructions
7741 @cindex listing machine instructions
7743 @itemx disassemble /m
7744 @itemx disassemble /r
7745 This specialized command dumps a range of memory as machine
7746 instructions. It can also print mixed source+disassembly by specifying
7747 the @code{/m} modifier and print the raw instructions in hex as well as
7748 in symbolic form by specifying the @code{/r}.
7749 The default memory range is the function surrounding the
7750 program counter of the selected frame. A single argument to this
7751 command is a program counter value; @value{GDBN} dumps the function
7752 surrounding this value. When two arguments are given, they should
7753 be separated by a comma, possibly surrounded by whitespace. The
7754 arguments specify a range of addresses to dump, in one of two forms:
7757 @item @var{start},@var{end}
7758 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
7759 @item @var{start},+@var{length}
7760 the addresses from @var{start} (inclusive) to
7761 @code{@var{start}+@var{length}} (exclusive).
7765 When 2 arguments are specified, the name of the function is also
7766 printed (since there could be several functions in the given range).
7768 The argument(s) can be any expression yielding a numeric value, such as
7769 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
7771 If the range of memory being disassembled contains current program counter,
7772 the instruction at that location is shown with a @code{=>} marker.
7775 The following example shows the disassembly of a range of addresses of
7776 HP PA-RISC 2.0 code:
7779 (@value{GDBP}) disas 0x32c4, 0x32e4
7780 Dump of assembler code from 0x32c4 to 0x32e4:
7781 0x32c4 <main+204>: addil 0,dp
7782 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
7783 0x32cc <main+212>: ldil 0x3000,r31
7784 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
7785 0x32d4 <main+220>: ldo 0(r31),rp
7786 0x32d8 <main+224>: addil -0x800,dp
7787 0x32dc <main+228>: ldo 0x588(r1),r26
7788 0x32e0 <main+232>: ldil 0x3000,r31
7789 End of assembler dump.
7792 Here is an example showing mixed source+assembly for Intel x86, when the
7793 program is stopped just after function prologue:
7796 (@value{GDBP}) disas /m main
7797 Dump of assembler code for function main:
7799 0x08048330 <+0>: push %ebp
7800 0x08048331 <+1>: mov %esp,%ebp
7801 0x08048333 <+3>: sub $0x8,%esp
7802 0x08048336 <+6>: and $0xfffffff0,%esp
7803 0x08048339 <+9>: sub $0x10,%esp
7805 6 printf ("Hello.\n");
7806 => 0x0804833c <+12>: movl $0x8048440,(%esp)
7807 0x08048343 <+19>: call 0x8048284 <puts@@plt>
7811 0x08048348 <+24>: mov $0x0,%eax
7812 0x0804834d <+29>: leave
7813 0x0804834e <+30>: ret
7815 End of assembler dump.
7818 Here is another example showing raw instructions in hex for AMD x86-64,
7821 (gdb) disas /r 0x400281,+10
7822 Dump of assembler code from 0x400281 to 0x40028b:
7823 0x0000000000400281: 38 36 cmp %dh,(%rsi)
7824 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
7825 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
7826 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
7827 End of assembler dump.
7830 Addresses cannot be specified as a linespec (@pxref{Specify Location}).
7831 So, for example, if you want to disassemble function @code{bar}
7832 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
7833 and not @samp{disassemble foo.c:bar}.
7835 Some architectures have more than one commonly-used set of instruction
7836 mnemonics or other syntax.
7838 For programs that were dynamically linked and use shared libraries,
7839 instructions that call functions or branch to locations in the shared
7840 libraries might show a seemingly bogus location---it's actually a
7841 location of the relocation table. On some architectures, @value{GDBN}
7842 might be able to resolve these to actual function names.
7845 @kindex set disassembly-flavor
7846 @cindex Intel disassembly flavor
7847 @cindex AT&T disassembly flavor
7848 @item set disassembly-flavor @var{instruction-set}
7849 Select the instruction set to use when disassembling the
7850 program via the @code{disassemble} or @code{x/i} commands.
7852 Currently this command is only defined for the Intel x86 family. You
7853 can set @var{instruction-set} to either @code{intel} or @code{att}.
7854 The default is @code{att}, the AT&T flavor used by default by Unix
7855 assemblers for x86-based targets.
7857 @kindex show disassembly-flavor
7858 @item show disassembly-flavor
7859 Show the current setting of the disassembly flavor.
7863 @kindex set disassemble-next-line
7864 @kindex show disassemble-next-line
7865 @item set disassemble-next-line
7866 @itemx show disassemble-next-line
7867 Control whether or not @value{GDBN} will disassemble the next source
7868 line or instruction when execution stops. If ON, @value{GDBN} will
7869 display disassembly of the next source line when execution of the
7870 program being debugged stops. This is @emph{in addition} to
7871 displaying the source line itself, which @value{GDBN} always does if
7872 possible. If the next source line cannot be displayed for some reason
7873 (e.g., if @value{GDBN} cannot find the source file, or there's no line
7874 info in the debug info), @value{GDBN} will display disassembly of the
7875 next @emph{instruction} instead of showing the next source line. If
7876 AUTO, @value{GDBN} will display disassembly of next instruction only
7877 if the source line cannot be displayed. This setting causes
7878 @value{GDBN} to display some feedback when you step through a function
7879 with no line info or whose source file is unavailable. The default is
7880 OFF, which means never display the disassembly of the next line or
7886 @chapter Examining Data
7888 @cindex printing data
7889 @cindex examining data
7892 The usual way to examine data in your program is with the @code{print}
7893 command (abbreviated @code{p}), or its synonym @code{inspect}. It
7894 evaluates and prints the value of an expression of the language your
7895 program is written in (@pxref{Languages, ,Using @value{GDBN} with
7896 Different Languages}). It may also print the expression using a
7897 Python-based pretty-printer (@pxref{Pretty Printing}).
7900 @item print @var{expr}
7901 @itemx print /@var{f} @var{expr}
7902 @var{expr} is an expression (in the source language). By default the
7903 value of @var{expr} is printed in a format appropriate to its data type;
7904 you can choose a different format by specifying @samp{/@var{f}}, where
7905 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
7909 @itemx print /@var{f}
7910 @cindex reprint the last value
7911 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
7912 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
7913 conveniently inspect the same value in an alternative format.
7916 A more low-level way of examining data is with the @code{x} command.
7917 It examines data in memory at a specified address and prints it in a
7918 specified format. @xref{Memory, ,Examining Memory}.
7920 If you are interested in information about types, or about how the
7921 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
7922 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
7925 @cindex exploring hierarchical data structures
7927 Another way of examining values of expressions and type information is
7928 through the Python extension command @code{explore} (available only if
7929 the @value{GDBN} build is configured with @code{--with-python}). It
7930 offers an interactive way to start at the highest level (or, the most
7931 abstract level) of the data type of an expression (or, the data type
7932 itself) and explore all the way down to leaf scalar values/fields
7933 embedded in the higher level data types.
7936 @item explore @var{arg}
7937 @var{arg} is either an expression (in the source language), or a type
7938 visible in the current context of the program being debugged.
7941 The working of the @code{explore} command can be illustrated with an
7942 example. If a data type @code{struct ComplexStruct} is defined in your
7952 struct ComplexStruct
7954 struct SimpleStruct *ss_p;
7960 followed by variable declarations as
7963 struct SimpleStruct ss = @{ 10, 1.11 @};
7964 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
7968 then, the value of the variable @code{cs} can be explored using the
7969 @code{explore} command as follows.
7973 The value of `cs' is a struct/class of type `struct ComplexStruct' with
7974 the following fields:
7976 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
7977 arr = <Enter 1 to explore this field of type `int [10]'>
7979 Enter the field number of choice:
7983 Since the fields of @code{cs} are not scalar values, you are being
7984 prompted to chose the field you want to explore. Let's say you choose
7985 the field @code{ss_p} by entering @code{0}. Then, since this field is a
7986 pointer, you will be asked if it is pointing to a single value. From
7987 the declaration of @code{cs} above, it is indeed pointing to a single
7988 value, hence you enter @code{y}. If you enter @code{n}, then you will
7989 be asked if it were pointing to an array of values, in which case this
7990 field will be explored as if it were an array.
7993 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
7994 Continue exploring it as a pointer to a single value [y/n]: y
7995 The value of `*(cs.ss_p)' is a struct/class of type `struct
7996 SimpleStruct' with the following fields:
7998 i = 10 .. (Value of type `int')
7999 d = 1.1100000000000001 .. (Value of type `double')
8001 Press enter to return to parent value:
8005 If the field @code{arr} of @code{cs} was chosen for exploration by
8006 entering @code{1} earlier, then since it is as array, you will be
8007 prompted to enter the index of the element in the array that you want
8011 `cs.arr' is an array of `int'.
8012 Enter the index of the element you want to explore in `cs.arr': 5
8014 `(cs.arr)[5]' is a scalar value of type `int'.
8018 Press enter to return to parent value:
8021 In general, at any stage of exploration, you can go deeper towards the
8022 leaf values by responding to the prompts appropriately, or hit the
8023 return key to return to the enclosing data structure (the @i{higher}
8024 level data structure).
8026 Similar to exploring values, you can use the @code{explore} command to
8027 explore types. Instead of specifying a value (which is typically a
8028 variable name or an expression valid in the current context of the
8029 program being debugged), you specify a type name. If you consider the
8030 same example as above, your can explore the type
8031 @code{struct ComplexStruct} by passing the argument
8032 @code{struct ComplexStruct} to the @code{explore} command.
8035 (gdb) explore struct ComplexStruct
8039 By responding to the prompts appropriately in the subsequent interactive
8040 session, you can explore the type @code{struct ComplexStruct} in a
8041 manner similar to how the value @code{cs} was explored in the above
8044 The @code{explore} command also has two sub-commands,
8045 @code{explore value} and @code{explore type}. The former sub-command is
8046 a way to explicitly specify that value exploration of the argument is
8047 being invoked, while the latter is a way to explicitly specify that type
8048 exploration of the argument is being invoked.
8051 @item explore value @var{expr}
8052 @cindex explore value
8053 This sub-command of @code{explore} explores the value of the
8054 expression @var{expr} (if @var{expr} is an expression valid in the
8055 current context of the program being debugged). The behavior of this
8056 command is identical to that of the behavior of the @code{explore}
8057 command being passed the argument @var{expr}.
8059 @item explore type @var{arg}
8060 @cindex explore type
8061 This sub-command of @code{explore} explores the type of @var{arg} (if
8062 @var{arg} is a type visible in the current context of program being
8063 debugged), or the type of the value/expression @var{arg} (if @var{arg}
8064 is an expression valid in the current context of the program being
8065 debugged). If @var{arg} is a type, then the behavior of this command is
8066 identical to that of the @code{explore} command being passed the
8067 argument @var{arg}. If @var{arg} is an expression, then the behavior of
8068 this command will be identical to that of the @code{explore} command
8069 being passed the type of @var{arg} as the argument.
8073 * Expressions:: Expressions
8074 * Ambiguous Expressions:: Ambiguous Expressions
8075 * Variables:: Program variables
8076 * Arrays:: Artificial arrays
8077 * Output Formats:: Output formats
8078 * Memory:: Examining memory
8079 * Auto Display:: Automatic display
8080 * Print Settings:: Print settings
8081 * Pretty Printing:: Python pretty printing
8082 * Value History:: Value history
8083 * Convenience Vars:: Convenience variables
8084 * Convenience Funs:: Convenience functions
8085 * Registers:: Registers
8086 * Floating Point Hardware:: Floating point hardware
8087 * Vector Unit:: Vector Unit
8088 * OS Information:: Auxiliary data provided by operating system
8089 * Memory Region Attributes:: Memory region attributes
8090 * Dump/Restore Files:: Copy between memory and a file
8091 * Core File Generation:: Cause a program dump its core
8092 * Character Sets:: Debugging programs that use a different
8093 character set than GDB does
8094 * Caching Target Data:: Data caching for targets
8095 * Searching Memory:: Searching memory for a sequence of bytes
8099 @section Expressions
8102 @code{print} and many other @value{GDBN} commands accept an expression and
8103 compute its value. Any kind of constant, variable or operator defined
8104 by the programming language you are using is valid in an expression in
8105 @value{GDBN}. This includes conditional expressions, function calls,
8106 casts, and string constants. It also includes preprocessor macros, if
8107 you compiled your program to include this information; see
8110 @cindex arrays in expressions
8111 @value{GDBN} supports array constants in expressions input by
8112 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
8113 you can use the command @code{print @{1, 2, 3@}} to create an array
8114 of three integers. If you pass an array to a function or assign it
8115 to a program variable, @value{GDBN} copies the array to memory that
8116 is @code{malloc}ed in the target program.
8118 Because C is so widespread, most of the expressions shown in examples in
8119 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
8120 Languages}, for information on how to use expressions in other
8123 In this section, we discuss operators that you can use in @value{GDBN}
8124 expressions regardless of your programming language.
8126 @cindex casts, in expressions
8127 Casts are supported in all languages, not just in C, because it is so
8128 useful to cast a number into a pointer in order to examine a structure
8129 at that address in memory.
8130 @c FIXME: casts supported---Mod2 true?
8132 @value{GDBN} supports these operators, in addition to those common
8133 to programming languages:
8137 @samp{@@} is a binary operator for treating parts of memory as arrays.
8138 @xref{Arrays, ,Artificial Arrays}, for more information.
8141 @samp{::} allows you to specify a variable in terms of the file or
8142 function where it is defined. @xref{Variables, ,Program Variables}.
8144 @cindex @{@var{type}@}
8145 @cindex type casting memory
8146 @cindex memory, viewing as typed object
8147 @cindex casts, to view memory
8148 @item @{@var{type}@} @var{addr}
8149 Refers to an object of type @var{type} stored at address @var{addr} in
8150 memory. @var{addr} may be any expression whose value is an integer or
8151 pointer (but parentheses are required around binary operators, just as in
8152 a cast). This construct is allowed regardless of what kind of data is
8153 normally supposed to reside at @var{addr}.
8156 @node Ambiguous Expressions
8157 @section Ambiguous Expressions
8158 @cindex ambiguous expressions
8160 Expressions can sometimes contain some ambiguous elements. For instance,
8161 some programming languages (notably Ada, C@t{++} and Objective-C) permit
8162 a single function name to be defined several times, for application in
8163 different contexts. This is called @dfn{overloading}. Another example
8164 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
8165 templates and is typically instantiated several times, resulting in
8166 the same function name being defined in different contexts.
8168 In some cases and depending on the language, it is possible to adjust
8169 the expression to remove the ambiguity. For instance in C@t{++}, you
8170 can specify the signature of the function you want to break on, as in
8171 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
8172 qualified name of your function often makes the expression unambiguous
8175 When an ambiguity that needs to be resolved is detected, the debugger
8176 has the capability to display a menu of numbered choices for each
8177 possibility, and then waits for the selection with the prompt @samp{>}.
8178 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
8179 aborts the current command. If the command in which the expression was
8180 used allows more than one choice to be selected, the next option in the
8181 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
8184 For example, the following session excerpt shows an attempt to set a
8185 breakpoint at the overloaded symbol @code{String::after}.
8186 We choose three particular definitions of that function name:
8188 @c FIXME! This is likely to change to show arg type lists, at least
8191 (@value{GDBP}) b String::after
8194 [2] file:String.cc; line number:867
8195 [3] file:String.cc; line number:860
8196 [4] file:String.cc; line number:875
8197 [5] file:String.cc; line number:853
8198 [6] file:String.cc; line number:846
8199 [7] file:String.cc; line number:735
8201 Breakpoint 1 at 0xb26c: file String.cc, line 867.
8202 Breakpoint 2 at 0xb344: file String.cc, line 875.
8203 Breakpoint 3 at 0xafcc: file String.cc, line 846.
8204 Multiple breakpoints were set.
8205 Use the "delete" command to delete unwanted
8212 @kindex set multiple-symbols
8213 @item set multiple-symbols @var{mode}
8214 @cindex multiple-symbols menu
8216 This option allows you to adjust the debugger behavior when an expression
8219 By default, @var{mode} is set to @code{all}. If the command with which
8220 the expression is used allows more than one choice, then @value{GDBN}
8221 automatically selects all possible choices. For instance, inserting
8222 a breakpoint on a function using an ambiguous name results in a breakpoint
8223 inserted on each possible match. However, if a unique choice must be made,
8224 then @value{GDBN} uses the menu to help you disambiguate the expression.
8225 For instance, printing the address of an overloaded function will result
8226 in the use of the menu.
8228 When @var{mode} is set to @code{ask}, the debugger always uses the menu
8229 when an ambiguity is detected.
8231 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
8232 an error due to the ambiguity and the command is aborted.
8234 @kindex show multiple-symbols
8235 @item show multiple-symbols
8236 Show the current value of the @code{multiple-symbols} setting.
8240 @section Program Variables
8242 The most common kind of expression to use is the name of a variable
8245 Variables in expressions are understood in the selected stack frame
8246 (@pxref{Selection, ,Selecting a Frame}); they must be either:
8250 global (or file-static)
8257 visible according to the scope rules of the
8258 programming language from the point of execution in that frame
8261 @noindent This means that in the function
8276 you can examine and use the variable @code{a} whenever your program is
8277 executing within the function @code{foo}, but you can only use or
8278 examine the variable @code{b} while your program is executing inside
8279 the block where @code{b} is declared.
8281 @cindex variable name conflict
8282 There is an exception: you can refer to a variable or function whose
8283 scope is a single source file even if the current execution point is not
8284 in this file. But it is possible to have more than one such variable or
8285 function with the same name (in different source files). If that
8286 happens, referring to that name has unpredictable effects. If you wish,
8287 you can specify a static variable in a particular function or file by
8288 using the colon-colon (@code{::}) notation:
8290 @cindex colon-colon, context for variables/functions
8292 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
8293 @cindex @code{::}, context for variables/functions
8296 @var{file}::@var{variable}
8297 @var{function}::@var{variable}
8301 Here @var{file} or @var{function} is the name of the context for the
8302 static @var{variable}. In the case of file names, you can use quotes to
8303 make sure @value{GDBN} parses the file name as a single word---for example,
8304 to print a global value of @code{x} defined in @file{f2.c}:
8307 (@value{GDBP}) p 'f2.c'::x
8310 The @code{::} notation is normally used for referring to
8311 static variables, since you typically disambiguate uses of local variables
8312 in functions by selecting the appropriate frame and using the
8313 simple name of the variable. However, you may also use this notation
8314 to refer to local variables in frames enclosing the selected frame:
8323 process (a); /* Stop here */
8334 For example, if there is a breakpoint at the commented line,
8335 here is what you might see
8336 when the program stops after executing the call @code{bar(0)}:
8341 (@value{GDBP}) p bar::a
8344 #2 0x080483d0 in foo (a=5) at foobar.c:12
8347 (@value{GDBP}) p bar::a
8351 @cindex C@t{++} scope resolution
8352 These uses of @samp{::} are very rarely in conflict with the very
8353 similar use of the same notation in C@t{++}. When they are in
8354 conflict, the C@t{++} meaning takes precedence; however, this can be
8355 overridden by quoting the file or function name with single quotes.
8357 For example, suppose the program is stopped in a method of a class
8358 that has a field named @code{includefile}, and there is also an
8359 include file named @file{includefile} that defines a variable,
8363 (@value{GDBP}) p includefile
8365 (@value{GDBP}) p includefile::some_global
8366 A syntax error in expression, near `'.
8367 (@value{GDBP}) p 'includefile'::some_global
8371 @cindex wrong values
8372 @cindex variable values, wrong
8373 @cindex function entry/exit, wrong values of variables
8374 @cindex optimized code, wrong values of variables
8376 @emph{Warning:} Occasionally, a local variable may appear to have the
8377 wrong value at certain points in a function---just after entry to a new
8378 scope, and just before exit.
8380 You may see this problem when you are stepping by machine instructions.
8381 This is because, on most machines, it takes more than one instruction to
8382 set up a stack frame (including local variable definitions); if you are
8383 stepping by machine instructions, variables may appear to have the wrong
8384 values until the stack frame is completely built. On exit, it usually
8385 also takes more than one machine instruction to destroy a stack frame;
8386 after you begin stepping through that group of instructions, local
8387 variable definitions may be gone.
8389 This may also happen when the compiler does significant optimizations.
8390 To be sure of always seeing accurate values, turn off all optimization
8393 @cindex ``No symbol "foo" in current context''
8394 Another possible effect of compiler optimizations is to optimize
8395 unused variables out of existence, or assign variables to registers (as
8396 opposed to memory addresses). Depending on the support for such cases
8397 offered by the debug info format used by the compiler, @value{GDBN}
8398 might not be able to display values for such local variables. If that
8399 happens, @value{GDBN} will print a message like this:
8402 No symbol "foo" in current context.
8405 To solve such problems, either recompile without optimizations, or use a
8406 different debug info format, if the compiler supports several such
8407 formats. @xref{Compilation}, for more information on choosing compiler
8408 options. @xref{C, ,C and C@t{++}}, for more information about debug
8409 info formats that are best suited to C@t{++} programs.
8411 If you ask to print an object whose contents are unknown to
8412 @value{GDBN}, e.g., because its data type is not completely specified
8413 by the debug information, @value{GDBN} will say @samp{<incomplete
8414 type>}. @xref{Symbols, incomplete type}, for more about this.
8416 If you append @kbd{@@entry} string to a function parameter name you get its
8417 value at the time the function got called. If the value is not available an
8418 error message is printed. Entry values are available only with some compilers.
8419 Entry values are normally also printed at the function parameter list according
8420 to @ref{set print entry-values}.
8423 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
8429 (gdb) print i@@entry
8433 Strings are identified as arrays of @code{char} values without specified
8434 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
8435 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
8436 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
8437 defines literal string type @code{"char"} as @code{char} without a sign.
8442 signed char var1[] = "A";
8445 You get during debugging
8450 $2 = @{65 'A', 0 '\0'@}
8454 @section Artificial Arrays
8456 @cindex artificial array
8458 @kindex @@@r{, referencing memory as an array}
8459 It is often useful to print out several successive objects of the
8460 same type in memory; a section of an array, or an array of
8461 dynamically determined size for which only a pointer exists in the
8464 You can do this by referring to a contiguous span of memory as an
8465 @dfn{artificial array}, using the binary operator @samp{@@}. The left
8466 operand of @samp{@@} should be the first element of the desired array
8467 and be an individual object. The right operand should be the desired length
8468 of the array. The result is an array value whose elements are all of
8469 the type of the left argument. The first element is actually the left
8470 argument; the second element comes from bytes of memory immediately
8471 following those that hold the first element, and so on. Here is an
8472 example. If a program says
8475 int *array = (int *) malloc (len * sizeof (int));
8479 you can print the contents of @code{array} with
8485 The left operand of @samp{@@} must reside in memory. Array values made
8486 with @samp{@@} in this way behave just like other arrays in terms of
8487 subscripting, and are coerced to pointers when used in expressions.
8488 Artificial arrays most often appear in expressions via the value history
8489 (@pxref{Value History, ,Value History}), after printing one out.
8491 Another way to create an artificial array is to use a cast.
8492 This re-interprets a value as if it were an array.
8493 The value need not be in memory:
8495 (@value{GDBP}) p/x (short[2])0x12345678
8496 $1 = @{0x1234, 0x5678@}
8499 As a convenience, if you leave the array length out (as in
8500 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
8501 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
8503 (@value{GDBP}) p/x (short[])0x12345678
8504 $2 = @{0x1234, 0x5678@}
8507 Sometimes the artificial array mechanism is not quite enough; in
8508 moderately complex data structures, the elements of interest may not
8509 actually be adjacent---for example, if you are interested in the values
8510 of pointers in an array. One useful work-around in this situation is
8511 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
8512 Variables}) as a counter in an expression that prints the first
8513 interesting value, and then repeat that expression via @key{RET}. For
8514 instance, suppose you have an array @code{dtab} of pointers to
8515 structures, and you are interested in the values of a field @code{fv}
8516 in each structure. Here is an example of what you might type:
8526 @node Output Formats
8527 @section Output Formats
8529 @cindex formatted output
8530 @cindex output formats
8531 By default, @value{GDBN} prints a value according to its data type. Sometimes
8532 this is not what you want. For example, you might want to print a number
8533 in hex, or a pointer in decimal. Or you might want to view data in memory
8534 at a certain address as a character string or as an instruction. To do
8535 these things, specify an @dfn{output format} when you print a value.
8537 The simplest use of output formats is to say how to print a value
8538 already computed. This is done by starting the arguments of the
8539 @code{print} command with a slash and a format letter. The format
8540 letters supported are:
8544 Regard the bits of the value as an integer, and print the integer in
8548 Print as integer in signed decimal.
8551 Print as integer in unsigned decimal.
8554 Print as integer in octal.
8557 Print as integer in binary. The letter @samp{t} stands for ``two''.
8558 @footnote{@samp{b} cannot be used because these format letters are also
8559 used with the @code{x} command, where @samp{b} stands for ``byte'';
8560 see @ref{Memory,,Examining Memory}.}
8563 @cindex unknown address, locating
8564 @cindex locate address
8565 Print as an address, both absolute in hexadecimal and as an offset from
8566 the nearest preceding symbol. You can use this format used to discover
8567 where (in what function) an unknown address is located:
8570 (@value{GDBP}) p/a 0x54320
8571 $3 = 0x54320 <_initialize_vx+396>
8575 The command @code{info symbol 0x54320} yields similar results.
8576 @xref{Symbols, info symbol}.
8579 Regard as an integer and print it as a character constant. This
8580 prints both the numerical value and its character representation. The
8581 character representation is replaced with the octal escape @samp{\nnn}
8582 for characters outside the 7-bit @sc{ascii} range.
8584 Without this format, @value{GDBN} displays @code{char},
8585 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
8586 constants. Single-byte members of vectors are displayed as integer
8590 Regard the bits of the value as a floating point number and print
8591 using typical floating point syntax.
8594 @cindex printing strings
8595 @cindex printing byte arrays
8596 Regard as a string, if possible. With this format, pointers to single-byte
8597 data are displayed as null-terminated strings and arrays of single-byte data
8598 are displayed as fixed-length strings. Other values are displayed in their
8601 Without this format, @value{GDBN} displays pointers to and arrays of
8602 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
8603 strings. Single-byte members of a vector are displayed as an integer
8607 Like @samp{x} formatting, the value is treated as an integer and
8608 printed as hexadecimal, but leading zeros are printed to pad the value
8609 to the size of the integer type.
8612 @cindex raw printing
8613 Print using the @samp{raw} formatting. By default, @value{GDBN} will
8614 use a Python-based pretty-printer, if one is available (@pxref{Pretty
8615 Printing}). This typically results in a higher-level display of the
8616 value's contents. The @samp{r} format bypasses any Python
8617 pretty-printer which might exist.
8620 For example, to print the program counter in hex (@pxref{Registers}), type
8627 Note that no space is required before the slash; this is because command
8628 names in @value{GDBN} cannot contain a slash.
8630 To reprint the last value in the value history with a different format,
8631 you can use the @code{print} command with just a format and no
8632 expression. For example, @samp{p/x} reprints the last value in hex.
8635 @section Examining Memory
8637 You can use the command @code{x} (for ``examine'') to examine memory in
8638 any of several formats, independently of your program's data types.
8640 @cindex examining memory
8642 @kindex x @r{(examine memory)}
8643 @item x/@var{nfu} @var{addr}
8646 Use the @code{x} command to examine memory.
8649 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
8650 much memory to display and how to format it; @var{addr} is an
8651 expression giving the address where you want to start displaying memory.
8652 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
8653 Several commands set convenient defaults for @var{addr}.
8656 @item @var{n}, the repeat count
8657 The repeat count is a decimal integer; the default is 1. It specifies
8658 how much memory (counting by units @var{u}) to display.
8659 @c This really is **decimal**; unaffected by 'set radix' as of GDB
8662 @item @var{f}, the display format
8663 The display format is one of the formats used by @code{print}
8664 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
8665 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
8666 The default is @samp{x} (hexadecimal) initially. The default changes
8667 each time you use either @code{x} or @code{print}.
8669 @item @var{u}, the unit size
8670 The unit size is any of
8676 Halfwords (two bytes).
8678 Words (four bytes). This is the initial default.
8680 Giant words (eight bytes).
8683 Each time you specify a unit size with @code{x}, that size becomes the
8684 default unit the next time you use @code{x}. For the @samp{i} format,
8685 the unit size is ignored and is normally not written. For the @samp{s} format,
8686 the unit size defaults to @samp{b}, unless it is explicitly given.
8687 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
8688 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
8689 Note that the results depend on the programming language of the
8690 current compilation unit. If the language is C, the @samp{s}
8691 modifier will use the UTF-16 encoding while @samp{w} will use
8692 UTF-32. The encoding is set by the programming language and cannot
8695 @item @var{addr}, starting display address
8696 @var{addr} is the address where you want @value{GDBN} to begin displaying
8697 memory. The expression need not have a pointer value (though it may);
8698 it is always interpreted as an integer address of a byte of memory.
8699 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
8700 @var{addr} is usually just after the last address examined---but several
8701 other commands also set the default address: @code{info breakpoints} (to
8702 the address of the last breakpoint listed), @code{info line} (to the
8703 starting address of a line), and @code{print} (if you use it to display
8704 a value from memory).
8707 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
8708 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
8709 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
8710 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
8711 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
8713 Since the letters indicating unit sizes are all distinct from the
8714 letters specifying output formats, you do not have to remember whether
8715 unit size or format comes first; either order works. The output
8716 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
8717 (However, the count @var{n} must come first; @samp{wx4} does not work.)
8719 Even though the unit size @var{u} is ignored for the formats @samp{s}
8720 and @samp{i}, you might still want to use a count @var{n}; for example,
8721 @samp{3i} specifies that you want to see three machine instructions,
8722 including any operands. For convenience, especially when used with
8723 the @code{display} command, the @samp{i} format also prints branch delay
8724 slot instructions, if any, beyond the count specified, which immediately
8725 follow the last instruction that is within the count. The command
8726 @code{disassemble} gives an alternative way of inspecting machine
8727 instructions; see @ref{Machine Code,,Source and Machine Code}.
8729 All the defaults for the arguments to @code{x} are designed to make it
8730 easy to continue scanning memory with minimal specifications each time
8731 you use @code{x}. For example, after you have inspected three machine
8732 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
8733 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
8734 the repeat count @var{n} is used again; the other arguments default as
8735 for successive uses of @code{x}.
8737 When examining machine instructions, the instruction at current program
8738 counter is shown with a @code{=>} marker. For example:
8741 (@value{GDBP}) x/5i $pc-6
8742 0x804837f <main+11>: mov %esp,%ebp
8743 0x8048381 <main+13>: push %ecx
8744 0x8048382 <main+14>: sub $0x4,%esp
8745 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
8746 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
8749 @cindex @code{$_}, @code{$__}, and value history
8750 The addresses and contents printed by the @code{x} command are not saved
8751 in the value history because there is often too much of them and they
8752 would get in the way. Instead, @value{GDBN} makes these values available for
8753 subsequent use in expressions as values of the convenience variables
8754 @code{$_} and @code{$__}. After an @code{x} command, the last address
8755 examined is available for use in expressions in the convenience variable
8756 @code{$_}. The contents of that address, as examined, are available in
8757 the convenience variable @code{$__}.
8759 If the @code{x} command has a repeat count, the address and contents saved
8760 are from the last memory unit printed; this is not the same as the last
8761 address printed if several units were printed on the last line of output.
8763 @cindex remote memory comparison
8764 @cindex verify remote memory image
8765 When you are debugging a program running on a remote target machine
8766 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
8767 remote machine's memory against the executable file you downloaded to
8768 the target. The @code{compare-sections} command is provided for such
8772 @kindex compare-sections
8773 @item compare-sections @r{[}@var{section-name}@r{]}
8774 Compare the data of a loadable section @var{section-name} in the
8775 executable file of the program being debugged with the same section in
8776 the remote machine's memory, and report any mismatches. With no
8777 arguments, compares all loadable sections. This command's
8778 availability depends on the target's support for the @code{"qCRC"}
8783 @section Automatic Display
8784 @cindex automatic display
8785 @cindex display of expressions
8787 If you find that you want to print the value of an expression frequently
8788 (to see how it changes), you might want to add it to the @dfn{automatic
8789 display list} so that @value{GDBN} prints its value each time your program stops.
8790 Each expression added to the list is given a number to identify it;
8791 to remove an expression from the list, you specify that number.
8792 The automatic display looks like this:
8796 3: bar[5] = (struct hack *) 0x3804
8800 This display shows item numbers, expressions and their current values. As with
8801 displays you request manually using @code{x} or @code{print}, you can
8802 specify the output format you prefer; in fact, @code{display} decides
8803 whether to use @code{print} or @code{x} depending your format
8804 specification---it uses @code{x} if you specify either the @samp{i}
8805 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
8809 @item display @var{expr}
8810 Add the expression @var{expr} to the list of expressions to display
8811 each time your program stops. @xref{Expressions, ,Expressions}.
8813 @code{display} does not repeat if you press @key{RET} again after using it.
8815 @item display/@var{fmt} @var{expr}
8816 For @var{fmt} specifying only a display format and not a size or
8817 count, add the expression @var{expr} to the auto-display list but
8818 arrange to display it each time in the specified format @var{fmt}.
8819 @xref{Output Formats,,Output Formats}.
8821 @item display/@var{fmt} @var{addr}
8822 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
8823 number of units, add the expression @var{addr} as a memory address to
8824 be examined each time your program stops. Examining means in effect
8825 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
8828 For example, @samp{display/i $pc} can be helpful, to see the machine
8829 instruction about to be executed each time execution stops (@samp{$pc}
8830 is a common name for the program counter; @pxref{Registers, ,Registers}).
8833 @kindex delete display
8835 @item undisplay @var{dnums}@dots{}
8836 @itemx delete display @var{dnums}@dots{}
8837 Remove items from the list of expressions to display. Specify the
8838 numbers of the displays that you want affected with the command
8839 argument @var{dnums}. It can be a single display number, one of the
8840 numbers shown in the first field of the @samp{info display} display;
8841 or it could be a range of display numbers, as in @code{2-4}.
8843 @code{undisplay} does not repeat if you press @key{RET} after using it.
8844 (Otherwise you would just get the error @samp{No display number @dots{}}.)
8846 @kindex disable display
8847 @item disable display @var{dnums}@dots{}
8848 Disable the display of item numbers @var{dnums}. A disabled display
8849 item is not printed automatically, but is not forgotten. It may be
8850 enabled again later. Specify the numbers of the displays that you
8851 want affected with the command argument @var{dnums}. It can be a
8852 single display number, one of the numbers shown in the first field of
8853 the @samp{info display} display; or it could be a range of display
8854 numbers, as in @code{2-4}.
8856 @kindex enable display
8857 @item enable display @var{dnums}@dots{}
8858 Enable display of item numbers @var{dnums}. It becomes effective once
8859 again in auto display of its expression, until you specify otherwise.
8860 Specify the numbers of the displays that you want affected with the
8861 command argument @var{dnums}. It can be a single display number, one
8862 of the numbers shown in the first field of the @samp{info display}
8863 display; or it could be a range of display numbers, as in @code{2-4}.
8866 Display the current values of the expressions on the list, just as is
8867 done when your program stops.
8869 @kindex info display
8871 Print the list of expressions previously set up to display
8872 automatically, each one with its item number, but without showing the
8873 values. This includes disabled expressions, which are marked as such.
8874 It also includes expressions which would not be displayed right now
8875 because they refer to automatic variables not currently available.
8878 @cindex display disabled out of scope
8879 If a display expression refers to local variables, then it does not make
8880 sense outside the lexical context for which it was set up. Such an
8881 expression is disabled when execution enters a context where one of its
8882 variables is not defined. For example, if you give the command
8883 @code{display last_char} while inside a function with an argument
8884 @code{last_char}, @value{GDBN} displays this argument while your program
8885 continues to stop inside that function. When it stops elsewhere---where
8886 there is no variable @code{last_char}---the display is disabled
8887 automatically. The next time your program stops where @code{last_char}
8888 is meaningful, you can enable the display expression once again.
8890 @node Print Settings
8891 @section Print Settings
8893 @cindex format options
8894 @cindex print settings
8895 @value{GDBN} provides the following ways to control how arrays, structures,
8896 and symbols are printed.
8899 These settings are useful for debugging programs in any language:
8903 @item set print address
8904 @itemx set print address on
8905 @cindex print/don't print memory addresses
8906 @value{GDBN} prints memory addresses showing the location of stack
8907 traces, structure values, pointer values, breakpoints, and so forth,
8908 even when it also displays the contents of those addresses. The default
8909 is @code{on}. For example, this is what a stack frame display looks like with
8910 @code{set print address on}:
8915 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
8917 530 if (lquote != def_lquote)
8921 @item set print address off
8922 Do not print addresses when displaying their contents. For example,
8923 this is the same stack frame displayed with @code{set print address off}:
8927 (@value{GDBP}) set print addr off
8929 #0 set_quotes (lq="<<", rq=">>") at input.c:530
8930 530 if (lquote != def_lquote)
8934 You can use @samp{set print address off} to eliminate all machine
8935 dependent displays from the @value{GDBN} interface. For example, with
8936 @code{print address off}, you should get the same text for backtraces on
8937 all machines---whether or not they involve pointer arguments.
8940 @item show print address
8941 Show whether or not addresses are to be printed.
8944 When @value{GDBN} prints a symbolic address, it normally prints the
8945 closest earlier symbol plus an offset. If that symbol does not uniquely
8946 identify the address (for example, it is a name whose scope is a single
8947 source file), you may need to clarify. One way to do this is with
8948 @code{info line}, for example @samp{info line *0x4537}. Alternately,
8949 you can set @value{GDBN} to print the source file and line number when
8950 it prints a symbolic address:
8953 @item set print symbol-filename on
8954 @cindex source file and line of a symbol
8955 @cindex symbol, source file and line
8956 Tell @value{GDBN} to print the source file name and line number of a
8957 symbol in the symbolic form of an address.
8959 @item set print symbol-filename off
8960 Do not print source file name and line number of a symbol. This is the
8963 @item show print symbol-filename
8964 Show whether or not @value{GDBN} will print the source file name and
8965 line number of a symbol in the symbolic form of an address.
8968 Another situation where it is helpful to show symbol filenames and line
8969 numbers is when disassembling code; @value{GDBN} shows you the line
8970 number and source file that corresponds to each instruction.
8972 Also, you may wish to see the symbolic form only if the address being
8973 printed is reasonably close to the closest earlier symbol:
8976 @item set print max-symbolic-offset @var{max-offset}
8977 @itemx set print max-symbolic-offset unlimited
8978 @cindex maximum value for offset of closest symbol
8979 Tell @value{GDBN} to only display the symbolic form of an address if the
8980 offset between the closest earlier symbol and the address is less than
8981 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
8982 to always print the symbolic form of an address if any symbol precedes
8983 it. Zero is equivalent to @code{unlimited}.
8985 @item show print max-symbolic-offset
8986 Ask how large the maximum offset is that @value{GDBN} prints in a
8990 @cindex wild pointer, interpreting
8991 @cindex pointer, finding referent
8992 If you have a pointer and you are not sure where it points, try
8993 @samp{set print symbol-filename on}. Then you can determine the name
8994 and source file location of the variable where it points, using
8995 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
8996 For example, here @value{GDBN} shows that a variable @code{ptt} points
8997 at another variable @code{t}, defined in @file{hi2.c}:
9000 (@value{GDBP}) set print symbol-filename on
9001 (@value{GDBP}) p/a ptt
9002 $4 = 0xe008 <t in hi2.c>
9006 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
9007 does not show the symbol name and filename of the referent, even with
9008 the appropriate @code{set print} options turned on.
9011 You can also enable @samp{/a}-like formatting all the time using
9012 @samp{set print symbol on}:
9015 @item set print symbol on
9016 Tell @value{GDBN} to print the symbol corresponding to an address, if
9019 @item set print symbol off
9020 Tell @value{GDBN} not to print the symbol corresponding to an
9021 address. In this mode, @value{GDBN} will still print the symbol
9022 corresponding to pointers to functions. This is the default.
9024 @item show print symbol
9025 Show whether @value{GDBN} will display the symbol corresponding to an
9029 Other settings control how different kinds of objects are printed:
9032 @item set print array
9033 @itemx set print array on
9034 @cindex pretty print arrays
9035 Pretty print arrays. This format is more convenient to read,
9036 but uses more space. The default is off.
9038 @item set print array off
9039 Return to compressed format for arrays.
9041 @item show print array
9042 Show whether compressed or pretty format is selected for displaying
9045 @cindex print array indexes
9046 @item set print array-indexes
9047 @itemx set print array-indexes on
9048 Print the index of each element when displaying arrays. May be more
9049 convenient to locate a given element in the array or quickly find the
9050 index of a given element in that printed array. The default is off.
9052 @item set print array-indexes off
9053 Stop printing element indexes when displaying arrays.
9055 @item show print array-indexes
9056 Show whether the index of each element is printed when displaying
9059 @item set print elements @var{number-of-elements}
9060 @itemx set print elements unlimited
9061 @cindex number of array elements to print
9062 @cindex limit on number of printed array elements
9063 Set a limit on how many elements of an array @value{GDBN} will print.
9064 If @value{GDBN} is printing a large array, it stops printing after it has
9065 printed the number of elements set by the @code{set print elements} command.
9066 This limit also applies to the display of strings.
9067 When @value{GDBN} starts, this limit is set to 200.
9068 Setting @var{number-of-elements} to @code{unlimited} or zero means
9069 that the number of elements to print is unlimited.
9071 @item show print elements
9072 Display the number of elements of a large array that @value{GDBN} will print.
9073 If the number is 0, then the printing is unlimited.
9075 @item set print frame-arguments @var{value}
9076 @kindex set print frame-arguments
9077 @cindex printing frame argument values
9078 @cindex print all frame argument values
9079 @cindex print frame argument values for scalars only
9080 @cindex do not print frame argument values
9081 This command allows to control how the values of arguments are printed
9082 when the debugger prints a frame (@pxref{Frames}). The possible
9087 The values of all arguments are printed.
9090 Print the value of an argument only if it is a scalar. The value of more
9091 complex arguments such as arrays, structures, unions, etc, is replaced
9092 by @code{@dots{}}. This is the default. Here is an example where
9093 only scalar arguments are shown:
9096 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
9101 None of the argument values are printed. Instead, the value of each argument
9102 is replaced by @code{@dots{}}. In this case, the example above now becomes:
9105 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
9110 By default, only scalar arguments are printed. This command can be used
9111 to configure the debugger to print the value of all arguments, regardless
9112 of their type. However, it is often advantageous to not print the value
9113 of more complex parameters. For instance, it reduces the amount of
9114 information printed in each frame, making the backtrace more readable.
9115 Also, it improves performance when displaying Ada frames, because
9116 the computation of large arguments can sometimes be CPU-intensive,
9117 especially in large applications. Setting @code{print frame-arguments}
9118 to @code{scalars} (the default) or @code{none} avoids this computation,
9119 thus speeding up the display of each Ada frame.
9121 @item show print frame-arguments
9122 Show how the value of arguments should be displayed when printing a frame.
9124 @item set print raw frame-arguments on
9125 Print frame arguments in raw, non pretty-printed, form.
9127 @item set print raw frame-arguments off
9128 Print frame arguments in pretty-printed form, if there is a pretty-printer
9129 for the value (@pxref{Pretty Printing}),
9130 otherwise print the value in raw form.
9131 This is the default.
9133 @item show print raw frame-arguments
9134 Show whether to print frame arguments in raw form.
9136 @anchor{set print entry-values}
9137 @item set print entry-values @var{value}
9138 @kindex set print entry-values
9139 Set printing of frame argument values at function entry. In some cases
9140 @value{GDBN} can determine the value of function argument which was passed by
9141 the function caller, even if the value was modified inside the called function
9142 and therefore is different. With optimized code, the current value could be
9143 unavailable, but the entry value may still be known.
9145 The default value is @code{default} (see below for its description). Older
9146 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
9147 this feature will behave in the @code{default} setting the same way as with the
9150 This functionality is currently supported only by DWARF 2 debugging format and
9151 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9152 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9155 The @var{value} parameter can be one of the following:
9159 Print only actual parameter values, never print values from function entry
9163 #0 different (val=6)
9164 #0 lost (val=<optimized out>)
9166 #0 invalid (val=<optimized out>)
9170 Print only parameter values from function entry point. The actual parameter
9171 values are never printed.
9173 #0 equal (val@@entry=5)
9174 #0 different (val@@entry=5)
9175 #0 lost (val@@entry=5)
9176 #0 born (val@@entry=<optimized out>)
9177 #0 invalid (val@@entry=<optimized out>)
9181 Print only parameter values from function entry point. If value from function
9182 entry point is not known while the actual value is known, print the actual
9183 value for such parameter.
9185 #0 equal (val@@entry=5)
9186 #0 different (val@@entry=5)
9187 #0 lost (val@@entry=5)
9189 #0 invalid (val@@entry=<optimized out>)
9193 Print actual parameter values. If actual parameter value is not known while
9194 value from function entry point is known, print the entry point value for such
9198 #0 different (val=6)
9199 #0 lost (val@@entry=5)
9201 #0 invalid (val=<optimized out>)
9205 Always print both the actual parameter value and its value from function entry
9206 point, even if values of one or both are not available due to compiler
9209 #0 equal (val=5, val@@entry=5)
9210 #0 different (val=6, val@@entry=5)
9211 #0 lost (val=<optimized out>, val@@entry=5)
9212 #0 born (val=10, val@@entry=<optimized out>)
9213 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
9217 Print the actual parameter value if it is known and also its value from
9218 function entry point if it is known. If neither is known, print for the actual
9219 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
9220 values are known and identical, print the shortened
9221 @code{param=param@@entry=VALUE} notation.
9223 #0 equal (val=val@@entry=5)
9224 #0 different (val=6, val@@entry=5)
9225 #0 lost (val@@entry=5)
9227 #0 invalid (val=<optimized out>)
9231 Always print the actual parameter value. Print also its value from function
9232 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
9233 if both values are known and identical, print the shortened
9234 @code{param=param@@entry=VALUE} notation.
9236 #0 equal (val=val@@entry=5)
9237 #0 different (val=6, val@@entry=5)
9238 #0 lost (val=<optimized out>, val@@entry=5)
9240 #0 invalid (val=<optimized out>)
9244 For analysis messages on possible failures of frame argument values at function
9245 entry resolution see @ref{set debug entry-values}.
9247 @item show print entry-values
9248 Show the method being used for printing of frame argument values at function
9251 @item set print repeats @var{number-of-repeats}
9252 @itemx set print repeats unlimited
9253 @cindex repeated array elements
9254 Set the threshold for suppressing display of repeated array
9255 elements. When the number of consecutive identical elements of an
9256 array exceeds the threshold, @value{GDBN} prints the string
9257 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
9258 identical repetitions, instead of displaying the identical elements
9259 themselves. Setting the threshold to @code{unlimited} or zero will
9260 cause all elements to be individually printed. The default threshold
9263 @item show print repeats
9264 Display the current threshold for printing repeated identical
9267 @item set print null-stop
9268 @cindex @sc{null} elements in arrays
9269 Cause @value{GDBN} to stop printing the characters of an array when the first
9270 @sc{null} is encountered. This is useful when large arrays actually
9271 contain only short strings.
9274 @item show print null-stop
9275 Show whether @value{GDBN} stops printing an array on the first
9276 @sc{null} character.
9278 @item set print pretty on
9279 @cindex print structures in indented form
9280 @cindex indentation in structure display
9281 Cause @value{GDBN} to print structures in an indented format with one member
9282 per line, like this:
9297 @item set print pretty off
9298 Cause @value{GDBN} to print structures in a compact format, like this:
9302 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
9303 meat = 0x54 "Pork"@}
9308 This is the default format.
9310 @item show print pretty
9311 Show which format @value{GDBN} is using to print structures.
9313 @item set print sevenbit-strings on
9314 @cindex eight-bit characters in strings
9315 @cindex octal escapes in strings
9316 Print using only seven-bit characters; if this option is set,
9317 @value{GDBN} displays any eight-bit characters (in strings or
9318 character values) using the notation @code{\}@var{nnn}. This setting is
9319 best if you are working in English (@sc{ascii}) and you use the
9320 high-order bit of characters as a marker or ``meta'' bit.
9322 @item set print sevenbit-strings off
9323 Print full eight-bit characters. This allows the use of more
9324 international character sets, and is the default.
9326 @item show print sevenbit-strings
9327 Show whether or not @value{GDBN} is printing only seven-bit characters.
9329 @item set print union on
9330 @cindex unions in structures, printing
9331 Tell @value{GDBN} to print unions which are contained in structures
9332 and other unions. This is the default setting.
9334 @item set print union off
9335 Tell @value{GDBN} not to print unions which are contained in
9336 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
9339 @item show print union
9340 Ask @value{GDBN} whether or not it will print unions which are contained in
9341 structures and other unions.
9343 For example, given the declarations
9346 typedef enum @{Tree, Bug@} Species;
9347 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
9348 typedef enum @{Caterpillar, Cocoon, Butterfly@}
9359 struct thing foo = @{Tree, @{Acorn@}@};
9363 with @code{set print union on} in effect @samp{p foo} would print
9366 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
9370 and with @code{set print union off} in effect it would print
9373 $1 = @{it = Tree, form = @{...@}@}
9377 @code{set print union} affects programs written in C-like languages
9383 These settings are of interest when debugging C@t{++} programs:
9386 @cindex demangling C@t{++} names
9387 @item set print demangle
9388 @itemx set print demangle on
9389 Print C@t{++} names in their source form rather than in the encoded
9390 (``mangled'') form passed to the assembler and linker for type-safe
9391 linkage. The default is on.
9393 @item show print demangle
9394 Show whether C@t{++} names are printed in mangled or demangled form.
9396 @item set print asm-demangle
9397 @itemx set print asm-demangle on
9398 Print C@t{++} names in their source form rather than their mangled form, even
9399 in assembler code printouts such as instruction disassemblies.
9402 @item show print asm-demangle
9403 Show whether C@t{++} names in assembly listings are printed in mangled
9406 @cindex C@t{++} symbol decoding style
9407 @cindex symbol decoding style, C@t{++}
9408 @kindex set demangle-style
9409 @item set demangle-style @var{style}
9410 Choose among several encoding schemes used by different compilers to
9411 represent C@t{++} names. The choices for @var{style} are currently:
9415 Allow @value{GDBN} to choose a decoding style by inspecting your program.
9416 This is the default.
9419 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
9422 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
9425 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
9428 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
9429 @strong{Warning:} this setting alone is not sufficient to allow
9430 debugging @code{cfront}-generated executables. @value{GDBN} would
9431 require further enhancement to permit that.
9434 If you omit @var{style}, you will see a list of possible formats.
9436 @item show demangle-style
9437 Display the encoding style currently in use for decoding C@t{++} symbols.
9439 @item set print object
9440 @itemx set print object on
9441 @cindex derived type of an object, printing
9442 @cindex display derived types
9443 When displaying a pointer to an object, identify the @emph{actual}
9444 (derived) type of the object rather than the @emph{declared} type, using
9445 the virtual function table. Note that the virtual function table is
9446 required---this feature can only work for objects that have run-time
9447 type identification; a single virtual method in the object's declared
9448 type is sufficient. Note that this setting is also taken into account when
9449 working with variable objects via MI (@pxref{GDB/MI}).
9451 @item set print object off
9452 Display only the declared type of objects, without reference to the
9453 virtual function table. This is the default setting.
9455 @item show print object
9456 Show whether actual, or declared, object types are displayed.
9458 @item set print static-members
9459 @itemx set print static-members on
9460 @cindex static members of C@t{++} objects
9461 Print static members when displaying a C@t{++} object. The default is on.
9463 @item set print static-members off
9464 Do not print static members when displaying a C@t{++} object.
9466 @item show print static-members
9467 Show whether C@t{++} static members are printed or not.
9469 @item set print pascal_static-members
9470 @itemx set print pascal_static-members on
9471 @cindex static members of Pascal objects
9472 @cindex Pascal objects, static members display
9473 Print static members when displaying a Pascal object. The default is on.
9475 @item set print pascal_static-members off
9476 Do not print static members when displaying a Pascal object.
9478 @item show print pascal_static-members
9479 Show whether Pascal static members are printed or not.
9481 @c These don't work with HP ANSI C++ yet.
9482 @item set print vtbl
9483 @itemx set print vtbl on
9484 @cindex pretty print C@t{++} virtual function tables
9485 @cindex virtual functions (C@t{++}) display
9486 @cindex VTBL display
9487 Pretty print C@t{++} virtual function tables. The default is off.
9488 (The @code{vtbl} commands do not work on programs compiled with the HP
9489 ANSI C@t{++} compiler (@code{aCC}).)
9491 @item set print vtbl off
9492 Do not pretty print C@t{++} virtual function tables.
9494 @item show print vtbl
9495 Show whether C@t{++} virtual function tables are pretty printed, or not.
9498 @node Pretty Printing
9499 @section Pretty Printing
9501 @value{GDBN} provides a mechanism to allow pretty-printing of values using
9502 Python code. It greatly simplifies the display of complex objects. This
9503 mechanism works for both MI and the CLI.
9506 * Pretty-Printer Introduction:: Introduction to pretty-printers
9507 * Pretty-Printer Example:: An example pretty-printer
9508 * Pretty-Printer Commands:: Pretty-printer commands
9511 @node Pretty-Printer Introduction
9512 @subsection Pretty-Printer Introduction
9514 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
9515 registered for the value. If there is then @value{GDBN} invokes the
9516 pretty-printer to print the value. Otherwise the value is printed normally.
9518 Pretty-printers are normally named. This makes them easy to manage.
9519 The @samp{info pretty-printer} command will list all the installed
9520 pretty-printers with their names.
9521 If a pretty-printer can handle multiple data types, then its
9522 @dfn{subprinters} are the printers for the individual data types.
9523 Each such subprinter has its own name.
9524 The format of the name is @var{printer-name};@var{subprinter-name}.
9526 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
9527 Typically they are automatically loaded and registered when the corresponding
9528 debug information is loaded, thus making them available without having to
9529 do anything special.
9531 There are three places where a pretty-printer can be registered.
9535 Pretty-printers registered globally are available when debugging
9539 Pretty-printers registered with a program space are available only
9540 when debugging that program.
9541 @xref{Progspaces In Python}, for more details on program spaces in Python.
9544 Pretty-printers registered with an objfile are loaded and unloaded
9545 with the corresponding objfile (e.g., shared library).
9546 @xref{Objfiles In Python}, for more details on objfiles in Python.
9549 @xref{Selecting Pretty-Printers}, for further information on how
9550 pretty-printers are selected,
9552 @xref{Writing a Pretty-Printer}, for implementing pretty printers
9555 @node Pretty-Printer Example
9556 @subsection Pretty-Printer Example
9558 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
9561 (@value{GDBP}) print s
9563 static npos = 4294967295,
9565 <std::allocator<char>> = @{
9566 <__gnu_cxx::new_allocator<char>> = @{
9567 <No data fields>@}, <No data fields>
9569 members of std::basic_string<char, std::char_traits<char>,
9570 std::allocator<char> >::_Alloc_hider:
9571 _M_p = 0x804a014 "abcd"
9576 With a pretty-printer for @code{std::string} only the contents are printed:
9579 (@value{GDBP}) print s
9583 @node Pretty-Printer Commands
9584 @subsection Pretty-Printer Commands
9585 @cindex pretty-printer commands
9588 @kindex info pretty-printer
9589 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9590 Print the list of installed pretty-printers.
9591 This includes disabled pretty-printers, which are marked as such.
9593 @var{object-regexp} is a regular expression matching the objects
9594 whose pretty-printers to list.
9595 Objects can be @code{global}, the program space's file
9596 (@pxref{Progspaces In Python}),
9597 and the object files within that program space (@pxref{Objfiles In Python}).
9598 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
9599 looks up a printer from these three objects.
9601 @var{name-regexp} is a regular expression matching the name of the printers
9604 @kindex disable pretty-printer
9605 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9606 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9607 A disabled pretty-printer is not forgotten, it may be enabled again later.
9609 @kindex enable pretty-printer
9610 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9611 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9616 Suppose we have three pretty-printers installed: one from library1.so
9617 named @code{foo} that prints objects of type @code{foo}, and
9618 another from library2.so named @code{bar} that prints two types of objects,
9619 @code{bar1} and @code{bar2}.
9622 (gdb) info pretty-printer
9629 (gdb) info pretty-printer library2
9634 (gdb) disable pretty-printer library1
9636 2 of 3 printers enabled
9637 (gdb) info pretty-printer
9644 (gdb) disable pretty-printer library2 bar:bar1
9646 1 of 3 printers enabled
9647 (gdb) info pretty-printer library2
9654 (gdb) disable pretty-printer library2 bar
9656 0 of 3 printers enabled
9657 (gdb) info pretty-printer library2
9666 Note that for @code{bar} the entire printer can be disabled,
9667 as can each individual subprinter.
9670 @section Value History
9672 @cindex value history
9673 @cindex history of values printed by @value{GDBN}
9674 Values printed by the @code{print} command are saved in the @value{GDBN}
9675 @dfn{value history}. This allows you to refer to them in other expressions.
9676 Values are kept until the symbol table is re-read or discarded
9677 (for example with the @code{file} or @code{symbol-file} commands).
9678 When the symbol table changes, the value history is discarded,
9679 since the values may contain pointers back to the types defined in the
9684 @cindex history number
9685 The values printed are given @dfn{history numbers} by which you can
9686 refer to them. These are successive integers starting with one.
9687 @code{print} shows you the history number assigned to a value by
9688 printing @samp{$@var{num} = } before the value; here @var{num} is the
9691 To refer to any previous value, use @samp{$} followed by the value's
9692 history number. The way @code{print} labels its output is designed to
9693 remind you of this. Just @code{$} refers to the most recent value in
9694 the history, and @code{$$} refers to the value before that.
9695 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
9696 is the value just prior to @code{$$}, @code{$$1} is equivalent to
9697 @code{$$}, and @code{$$0} is equivalent to @code{$}.
9699 For example, suppose you have just printed a pointer to a structure and
9700 want to see the contents of the structure. It suffices to type
9706 If you have a chain of structures where the component @code{next} points
9707 to the next one, you can print the contents of the next one with this:
9714 You can print successive links in the chain by repeating this
9715 command---which you can do by just typing @key{RET}.
9717 Note that the history records values, not expressions. If the value of
9718 @code{x} is 4 and you type these commands:
9726 then the value recorded in the value history by the @code{print} command
9727 remains 4 even though the value of @code{x} has changed.
9732 Print the last ten values in the value history, with their item numbers.
9733 This is like @samp{p@ $$9} repeated ten times, except that @code{show
9734 values} does not change the history.
9736 @item show values @var{n}
9737 Print ten history values centered on history item number @var{n}.
9740 Print ten history values just after the values last printed. If no more
9741 values are available, @code{show values +} produces no display.
9744 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
9745 same effect as @samp{show values +}.
9747 @node Convenience Vars
9748 @section Convenience Variables
9750 @cindex convenience variables
9751 @cindex user-defined variables
9752 @value{GDBN} provides @dfn{convenience variables} that you can use within
9753 @value{GDBN} to hold on to a value and refer to it later. These variables
9754 exist entirely within @value{GDBN}; they are not part of your program, and
9755 setting a convenience variable has no direct effect on further execution
9756 of your program. That is why you can use them freely.
9758 Convenience variables are prefixed with @samp{$}. Any name preceded by
9759 @samp{$} can be used for a convenience variable, unless it is one of
9760 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
9761 (Value history references, in contrast, are @emph{numbers} preceded
9762 by @samp{$}. @xref{Value History, ,Value History}.)
9764 You can save a value in a convenience variable with an assignment
9765 expression, just as you would set a variable in your program.
9769 set $foo = *object_ptr
9773 would save in @code{$foo} the value contained in the object pointed to by
9776 Using a convenience variable for the first time creates it, but its
9777 value is @code{void} until you assign a new value. You can alter the
9778 value with another assignment at any time.
9780 Convenience variables have no fixed types. You can assign a convenience
9781 variable any type of value, including structures and arrays, even if
9782 that variable already has a value of a different type. The convenience
9783 variable, when used as an expression, has the type of its current value.
9786 @kindex show convenience
9787 @cindex show all user variables and functions
9788 @item show convenience
9789 Print a list of convenience variables used so far, and their values,
9790 as well as a list of the convenience functions.
9791 Abbreviated @code{show conv}.
9793 @kindex init-if-undefined
9794 @cindex convenience variables, initializing
9795 @item init-if-undefined $@var{variable} = @var{expression}
9796 Set a convenience variable if it has not already been set. This is useful
9797 for user-defined commands that keep some state. It is similar, in concept,
9798 to using local static variables with initializers in C (except that
9799 convenience variables are global). It can also be used to allow users to
9800 override default values used in a command script.
9802 If the variable is already defined then the expression is not evaluated so
9803 any side-effects do not occur.
9806 One of the ways to use a convenience variable is as a counter to be
9807 incremented or a pointer to be advanced. For example, to print
9808 a field from successive elements of an array of structures:
9812 print bar[$i++]->contents
9816 Repeat that command by typing @key{RET}.
9818 Some convenience variables are created automatically by @value{GDBN} and given
9819 values likely to be useful.
9822 @vindex $_@r{, convenience variable}
9824 The variable @code{$_} is automatically set by the @code{x} command to
9825 the last address examined (@pxref{Memory, ,Examining Memory}). Other
9826 commands which provide a default address for @code{x} to examine also
9827 set @code{$_} to that address; these commands include @code{info line}
9828 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
9829 except when set by the @code{x} command, in which case it is a pointer
9830 to the type of @code{$__}.
9832 @vindex $__@r{, convenience variable}
9834 The variable @code{$__} is automatically set by the @code{x} command
9835 to the value found in the last address examined. Its type is chosen
9836 to match the format in which the data was printed.
9839 @vindex $_exitcode@r{, convenience variable}
9840 When the program being debugged terminates normally, @value{GDBN}
9841 automatically sets this variable to the exit code of the program, and
9842 resets @code{$_exitsignal} to @code{void}.
9845 @vindex $_exitsignal@r{, convenience variable}
9846 When the program being debugged dies due to an uncaught signal,
9847 @value{GDBN} automatically sets this variable to that signal's number,
9848 and resets @code{$_exitcode} to @code{void}.
9850 To distinguish between whether the program being debugged has exited
9851 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
9852 @code{$_exitsignal} is not @code{void}), the convenience function
9853 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
9854 Functions}). For example, considering the following source code:
9860 main (int argc, char *argv[])
9867 A valid way of telling whether the program being debugged has exited
9868 or signalled would be:
9871 (@value{GDBP}) define has_exited_or_signalled
9872 Type commands for definition of ``has_exited_or_signalled''.
9873 End with a line saying just ``end''.
9874 >if $_isvoid ($_exitsignal)
9875 >echo The program has exited\n
9877 >echo The program has signalled\n
9883 Program terminated with signal SIGALRM, Alarm clock.
9884 The program no longer exists.
9885 (@value{GDBP}) has_exited_or_signalled
9886 The program has signalled
9889 As can be seen, @value{GDBN} correctly informs that the program being
9890 debugged has signalled, since it calls @code{raise} and raises a
9891 @code{SIGALRM} signal. If the program being debugged had not called
9892 @code{raise}, then @value{GDBN} would report a normal exit:
9895 (@value{GDBP}) has_exited_or_signalled
9896 The program has exited
9900 The variable @code{$_exception} is set to the exception object being
9901 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
9904 @itemx $_probe_arg0@dots{}$_probe_arg11
9905 Arguments to a static probe. @xref{Static Probe Points}.
9908 @vindex $_sdata@r{, inspect, convenience variable}
9909 The variable @code{$_sdata} contains extra collected static tracepoint
9910 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
9911 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
9912 if extra static tracepoint data has not been collected.
9915 @vindex $_siginfo@r{, convenience variable}
9916 The variable @code{$_siginfo} contains extra signal information
9917 (@pxref{extra signal information}). Note that @code{$_siginfo}
9918 could be empty, if the application has not yet received any signals.
9919 For example, it will be empty before you execute the @code{run} command.
9922 @vindex $_tlb@r{, convenience variable}
9923 The variable @code{$_tlb} is automatically set when debugging
9924 applications running on MS-Windows in native mode or connected to
9925 gdbserver that supports the @code{qGetTIBAddr} request.
9926 @xref{General Query Packets}.
9927 This variable contains the address of the thread information block.
9931 On HP-UX systems, if you refer to a function or variable name that
9932 begins with a dollar sign, @value{GDBN} searches for a user or system
9933 name first, before it searches for a convenience variable.
9935 @node Convenience Funs
9936 @section Convenience Functions
9938 @cindex convenience functions
9939 @value{GDBN} also supplies some @dfn{convenience functions}. These
9940 have a syntax similar to convenience variables. A convenience
9941 function can be used in an expression just like an ordinary function;
9942 however, a convenience function is implemented internally to
9945 These functions do not require @value{GDBN} to be configured with
9946 @code{Python} support, which means that they are always available.
9950 @item $_isvoid (@var{expr})
9951 @findex $_isvoid@r{, convenience function}
9952 Return one if the expression @var{expr} is @code{void}. Otherwise it
9955 A @code{void} expression is an expression where the type of the result
9956 is @code{void}. For example, you can examine a convenience variable
9957 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
9961 (@value{GDBP}) print $_exitcode
9963 (@value{GDBP}) print $_isvoid ($_exitcode)
9966 Starting program: ./a.out
9967 [Inferior 1 (process 29572) exited normally]
9968 (@value{GDBP}) print $_exitcode
9970 (@value{GDBP}) print $_isvoid ($_exitcode)
9974 In the example above, we used @code{$_isvoid} to check whether
9975 @code{$_exitcode} is @code{void} before and after the execution of the
9976 program being debugged. Before the execution there is no exit code to
9977 be examined, therefore @code{$_exitcode} is @code{void}. After the
9978 execution the program being debugged returned zero, therefore
9979 @code{$_exitcode} is zero, which means that it is not @code{void}
9982 The @code{void} expression can also be a call of a function from the
9983 program being debugged. For example, given the following function:
9992 The result of calling it inside @value{GDBN} is @code{void}:
9995 (@value{GDBP}) print foo ()
9997 (@value{GDBP}) print $_isvoid (foo ())
9999 (@value{GDBP}) set $v = foo ()
10000 (@value{GDBP}) print $v
10002 (@value{GDBP}) print $_isvoid ($v)
10008 These functions require @value{GDBN} to be configured with
10009 @code{Python} support.
10013 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
10014 @findex $_memeq@r{, convenience function}
10015 Returns one if the @var{length} bytes at the addresses given by
10016 @var{buf1} and @var{buf2} are equal.
10017 Otherwise it returns zero.
10019 @item $_regex(@var{str}, @var{regex})
10020 @findex $_regex@r{, convenience function}
10021 Returns one if the string @var{str} matches the regular expression
10022 @var{regex}. Otherwise it returns zero.
10023 The syntax of the regular expression is that specified by @code{Python}'s
10024 regular expression support.
10026 @item $_streq(@var{str1}, @var{str2})
10027 @findex $_streq@r{, convenience function}
10028 Returns one if the strings @var{str1} and @var{str2} are equal.
10029 Otherwise it returns zero.
10031 @item $_strlen(@var{str})
10032 @findex $_strlen@r{, convenience function}
10033 Returns the length of string @var{str}.
10037 @value{GDBN} provides the ability to list and get help on
10038 convenience functions.
10041 @item help function
10042 @kindex help function
10043 @cindex show all convenience functions
10044 Print a list of all convenience functions.
10051 You can refer to machine register contents, in expressions, as variables
10052 with names starting with @samp{$}. The names of registers are different
10053 for each machine; use @code{info registers} to see the names used on
10057 @kindex info registers
10058 @item info registers
10059 Print the names and values of all registers except floating-point
10060 and vector registers (in the selected stack frame).
10062 @kindex info all-registers
10063 @cindex floating point registers
10064 @item info all-registers
10065 Print the names and values of all registers, including floating-point
10066 and vector registers (in the selected stack frame).
10068 @item info registers @var{regname} @dots{}
10069 Print the @dfn{relativized} value of each specified register @var{regname}.
10070 As discussed in detail below, register values are normally relative to
10071 the selected stack frame. @var{regname} may be any register name valid on
10072 the machine you are using, with or without the initial @samp{$}.
10075 @cindex stack pointer register
10076 @cindex program counter register
10077 @cindex process status register
10078 @cindex frame pointer register
10079 @cindex standard registers
10080 @value{GDBN} has four ``standard'' register names that are available (in
10081 expressions) on most machines---whenever they do not conflict with an
10082 architecture's canonical mnemonics for registers. The register names
10083 @code{$pc} and @code{$sp} are used for the program counter register and
10084 the stack pointer. @code{$fp} is used for a register that contains a
10085 pointer to the current stack frame, and @code{$ps} is used for a
10086 register that contains the processor status. For example,
10087 you could print the program counter in hex with
10094 or print the instruction to be executed next with
10101 or add four to the stack pointer@footnote{This is a way of removing
10102 one word from the stack, on machines where stacks grow downward in
10103 memory (most machines, nowadays). This assumes that the innermost
10104 stack frame is selected; setting @code{$sp} is not allowed when other
10105 stack frames are selected. To pop entire frames off the stack,
10106 regardless of machine architecture, use @code{return};
10107 see @ref{Returning, ,Returning from a Function}.} with
10113 Whenever possible, these four standard register names are available on
10114 your machine even though the machine has different canonical mnemonics,
10115 so long as there is no conflict. The @code{info registers} command
10116 shows the canonical names. For example, on the SPARC, @code{info
10117 registers} displays the processor status register as @code{$psr} but you
10118 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
10119 is an alias for the @sc{eflags} register.
10121 @value{GDBN} always considers the contents of an ordinary register as an
10122 integer when the register is examined in this way. Some machines have
10123 special registers which can hold nothing but floating point; these
10124 registers are considered to have floating point values. There is no way
10125 to refer to the contents of an ordinary register as floating point value
10126 (although you can @emph{print} it as a floating point value with
10127 @samp{print/f $@var{regname}}).
10129 Some registers have distinct ``raw'' and ``virtual'' data formats. This
10130 means that the data format in which the register contents are saved by
10131 the operating system is not the same one that your program normally
10132 sees. For example, the registers of the 68881 floating point
10133 coprocessor are always saved in ``extended'' (raw) format, but all C
10134 programs expect to work with ``double'' (virtual) format. In such
10135 cases, @value{GDBN} normally works with the virtual format only (the format
10136 that makes sense for your program), but the @code{info registers} command
10137 prints the data in both formats.
10139 @cindex SSE registers (x86)
10140 @cindex MMX registers (x86)
10141 Some machines have special registers whose contents can be interpreted
10142 in several different ways. For example, modern x86-based machines
10143 have SSE and MMX registers that can hold several values packed
10144 together in several different formats. @value{GDBN} refers to such
10145 registers in @code{struct} notation:
10148 (@value{GDBP}) print $xmm1
10150 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
10151 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
10152 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
10153 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
10154 v4_int32 = @{0, 20657912, 11, 13@},
10155 v2_int64 = @{88725056443645952, 55834574859@},
10156 uint128 = 0x0000000d0000000b013b36f800000000
10161 To set values of such registers, you need to tell @value{GDBN} which
10162 view of the register you wish to change, as if you were assigning
10163 value to a @code{struct} member:
10166 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
10169 Normally, register values are relative to the selected stack frame
10170 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
10171 value that the register would contain if all stack frames farther in
10172 were exited and their saved registers restored. In order to see the
10173 true contents of hardware registers, you must select the innermost
10174 frame (with @samp{frame 0}).
10176 @cindex caller-saved registers
10177 @cindex call-clobbered registers
10178 @cindex volatile registers
10179 @cindex <not saved> values
10180 Usually ABIs reserve some registers as not needed to be saved by the
10181 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
10182 registers). It may therefore not be possible for @value{GDBN} to know
10183 the value a register had before the call (in other words, in the outer
10184 frame), if the register value has since been changed by the callee.
10185 @value{GDBN} tries to deduce where the inner frame saved
10186 (``callee-saved'') registers, from the debug info, unwind info, or the
10187 machine code generated by your compiler. If some register is not
10188 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
10189 its own knowledge of the ABI, or because the debug/unwind info
10190 explicitly says the register's value is undefined), @value{GDBN}
10191 displays @w{@samp{<not saved>}} as the register's value. With targets
10192 that @value{GDBN} has no knowledge of the register saving convention,
10193 if a register was not saved by the callee, then its value and location
10194 in the outer frame are assumed to be the same of the inner frame.
10195 This is usually harmless, because if the register is call-clobbered,
10196 the caller either does not care what is in the register after the
10197 call, or has code to restore the value that it does care about. Note,
10198 however, that if you change such a register in the outer frame, you
10199 may also be affecting the inner frame. Also, the more ``outer'' the
10200 frame is you're looking at, the more likely a call-clobbered
10201 register's value is to be wrong, in the sense that it doesn't actually
10202 represent the value the register had just before the call.
10204 @node Floating Point Hardware
10205 @section Floating Point Hardware
10206 @cindex floating point
10208 Depending on the configuration, @value{GDBN} may be able to give
10209 you more information about the status of the floating point hardware.
10214 Display hardware-dependent information about the floating
10215 point unit. The exact contents and layout vary depending on the
10216 floating point chip. Currently, @samp{info float} is supported on
10217 the ARM and x86 machines.
10221 @section Vector Unit
10222 @cindex vector unit
10224 Depending on the configuration, @value{GDBN} may be able to give you
10225 more information about the status of the vector unit.
10228 @kindex info vector
10230 Display information about the vector unit. The exact contents and
10231 layout vary depending on the hardware.
10234 @node OS Information
10235 @section Operating System Auxiliary Information
10236 @cindex OS information
10238 @value{GDBN} provides interfaces to useful OS facilities that can help
10239 you debug your program.
10241 @cindex auxiliary vector
10242 @cindex vector, auxiliary
10243 Some operating systems supply an @dfn{auxiliary vector} to programs at
10244 startup. This is akin to the arguments and environment that you
10245 specify for a program, but contains a system-dependent variety of
10246 binary values that tell system libraries important details about the
10247 hardware, operating system, and process. Each value's purpose is
10248 identified by an integer tag; the meanings are well-known but system-specific.
10249 Depending on the configuration and operating system facilities,
10250 @value{GDBN} may be able to show you this information. For remote
10251 targets, this functionality may further depend on the remote stub's
10252 support of the @samp{qXfer:auxv:read} packet, see
10253 @ref{qXfer auxiliary vector read}.
10258 Display the auxiliary vector of the inferior, which can be either a
10259 live process or a core dump file. @value{GDBN} prints each tag value
10260 numerically, and also shows names and text descriptions for recognized
10261 tags. Some values in the vector are numbers, some bit masks, and some
10262 pointers to strings or other data. @value{GDBN} displays each value in the
10263 most appropriate form for a recognized tag, and in hexadecimal for
10264 an unrecognized tag.
10267 On some targets, @value{GDBN} can access operating system-specific
10268 information and show it to you. The types of information available
10269 will differ depending on the type of operating system running on the
10270 target. The mechanism used to fetch the data is described in
10271 @ref{Operating System Information}. For remote targets, this
10272 functionality depends on the remote stub's support of the
10273 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
10277 @item info os @var{infotype}
10279 Display OS information of the requested type.
10281 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
10283 @anchor{linux info os infotypes}
10285 @kindex info os processes
10287 Display the list of processes on the target. For each process,
10288 @value{GDBN} prints the process identifier, the name of the user, the
10289 command corresponding to the process, and the list of processor cores
10290 that the process is currently running on. (To understand what these
10291 properties mean, for this and the following info types, please consult
10292 the general @sc{gnu}/Linux documentation.)
10294 @kindex info os procgroups
10296 Display the list of process groups on the target. For each process,
10297 @value{GDBN} prints the identifier of the process group that it belongs
10298 to, the command corresponding to the process group leader, the process
10299 identifier, and the command line of the process. The list is sorted
10300 first by the process group identifier, then by the process identifier,
10301 so that processes belonging to the same process group are grouped together
10302 and the process group leader is listed first.
10304 @kindex info os threads
10306 Display the list of threads running on the target. For each thread,
10307 @value{GDBN} prints the identifier of the process that the thread
10308 belongs to, the command of the process, the thread identifier, and the
10309 processor core that it is currently running on. The main thread of a
10310 process is not listed.
10312 @kindex info os files
10314 Display the list of open file descriptors on the target. For each
10315 file descriptor, @value{GDBN} prints the identifier of the process
10316 owning the descriptor, the command of the owning process, the value
10317 of the descriptor, and the target of the descriptor.
10319 @kindex info os sockets
10321 Display the list of Internet-domain sockets on the target. For each
10322 socket, @value{GDBN} prints the address and port of the local and
10323 remote endpoints, the current state of the connection, the creator of
10324 the socket, the IP address family of the socket, and the type of the
10327 @kindex info os shm
10329 Display the list of all System V shared-memory regions on the target.
10330 For each shared-memory region, @value{GDBN} prints the region key,
10331 the shared-memory identifier, the access permissions, the size of the
10332 region, the process that created the region, the process that last
10333 attached to or detached from the region, the current number of live
10334 attaches to the region, and the times at which the region was last
10335 attached to, detach from, and changed.
10337 @kindex info os semaphores
10339 Display the list of all System V semaphore sets on the target. For each
10340 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
10341 set identifier, the access permissions, the number of semaphores in the
10342 set, the user and group of the owner and creator of the semaphore set,
10343 and the times at which the semaphore set was operated upon and changed.
10345 @kindex info os msg
10347 Display the list of all System V message queues on the target. For each
10348 message queue, @value{GDBN} prints the message queue key, the message
10349 queue identifier, the access permissions, the current number of bytes
10350 on the queue, the current number of messages on the queue, the processes
10351 that last sent and received a message on the queue, the user and group
10352 of the owner and creator of the message queue, the times at which a
10353 message was last sent and received on the queue, and the time at which
10354 the message queue was last changed.
10356 @kindex info os modules
10358 Display the list of all loaded kernel modules on the target. For each
10359 module, @value{GDBN} prints the module name, the size of the module in
10360 bytes, the number of times the module is used, the dependencies of the
10361 module, the status of the module, and the address of the loaded module
10366 If @var{infotype} is omitted, then list the possible values for
10367 @var{infotype} and the kind of OS information available for each
10368 @var{infotype}. If the target does not return a list of possible
10369 types, this command will report an error.
10372 @node Memory Region Attributes
10373 @section Memory Region Attributes
10374 @cindex memory region attributes
10376 @dfn{Memory region attributes} allow you to describe special handling
10377 required by regions of your target's memory. @value{GDBN} uses
10378 attributes to determine whether to allow certain types of memory
10379 accesses; whether to use specific width accesses; and whether to cache
10380 target memory. By default the description of memory regions is
10381 fetched from the target (if the current target supports this), but the
10382 user can override the fetched regions.
10384 Defined memory regions can be individually enabled and disabled. When a
10385 memory region is disabled, @value{GDBN} uses the default attributes when
10386 accessing memory in that region. Similarly, if no memory regions have
10387 been defined, @value{GDBN} uses the default attributes when accessing
10390 When a memory region is defined, it is given a number to identify it;
10391 to enable, disable, or remove a memory region, you specify that number.
10395 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
10396 Define a memory region bounded by @var{lower} and @var{upper} with
10397 attributes @var{attributes}@dots{}, and add it to the list of regions
10398 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
10399 case: it is treated as the target's maximum memory address.
10400 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
10403 Discard any user changes to the memory regions and use target-supplied
10404 regions, if available, or no regions if the target does not support.
10407 @item delete mem @var{nums}@dots{}
10408 Remove memory regions @var{nums}@dots{} from the list of regions
10409 monitored by @value{GDBN}.
10411 @kindex disable mem
10412 @item disable mem @var{nums}@dots{}
10413 Disable monitoring of memory regions @var{nums}@dots{}.
10414 A disabled memory region is not forgotten.
10415 It may be enabled again later.
10418 @item enable mem @var{nums}@dots{}
10419 Enable monitoring of memory regions @var{nums}@dots{}.
10423 Print a table of all defined memory regions, with the following columns
10427 @item Memory Region Number
10428 @item Enabled or Disabled.
10429 Enabled memory regions are marked with @samp{y}.
10430 Disabled memory regions are marked with @samp{n}.
10433 The address defining the inclusive lower bound of the memory region.
10436 The address defining the exclusive upper bound of the memory region.
10439 The list of attributes set for this memory region.
10444 @subsection Attributes
10446 @subsubsection Memory Access Mode
10447 The access mode attributes set whether @value{GDBN} may make read or
10448 write accesses to a memory region.
10450 While these attributes prevent @value{GDBN} from performing invalid
10451 memory accesses, they do nothing to prevent the target system, I/O DMA,
10452 etc.@: from accessing memory.
10456 Memory is read only.
10458 Memory is write only.
10460 Memory is read/write. This is the default.
10463 @subsubsection Memory Access Size
10464 The access size attribute tells @value{GDBN} to use specific sized
10465 accesses in the memory region. Often memory mapped device registers
10466 require specific sized accesses. If no access size attribute is
10467 specified, @value{GDBN} may use accesses of any size.
10471 Use 8 bit memory accesses.
10473 Use 16 bit memory accesses.
10475 Use 32 bit memory accesses.
10477 Use 64 bit memory accesses.
10480 @c @subsubsection Hardware/Software Breakpoints
10481 @c The hardware/software breakpoint attributes set whether @value{GDBN}
10482 @c will use hardware or software breakpoints for the internal breakpoints
10483 @c used by the step, next, finish, until, etc. commands.
10487 @c Always use hardware breakpoints
10488 @c @item swbreak (default)
10491 @subsubsection Data Cache
10492 The data cache attributes set whether @value{GDBN} will cache target
10493 memory. While this generally improves performance by reducing debug
10494 protocol overhead, it can lead to incorrect results because @value{GDBN}
10495 does not know about volatile variables or memory mapped device
10500 Enable @value{GDBN} to cache target memory.
10502 Disable @value{GDBN} from caching target memory. This is the default.
10505 @subsection Memory Access Checking
10506 @value{GDBN} can be instructed to refuse accesses to memory that is
10507 not explicitly described. This can be useful if accessing such
10508 regions has undesired effects for a specific target, or to provide
10509 better error checking. The following commands control this behaviour.
10512 @kindex set mem inaccessible-by-default
10513 @item set mem inaccessible-by-default [on|off]
10514 If @code{on} is specified, make @value{GDBN} treat memory not
10515 explicitly described by the memory ranges as non-existent and refuse accesses
10516 to such memory. The checks are only performed if there's at least one
10517 memory range defined. If @code{off} is specified, make @value{GDBN}
10518 treat the memory not explicitly described by the memory ranges as RAM.
10519 The default value is @code{on}.
10520 @kindex show mem inaccessible-by-default
10521 @item show mem inaccessible-by-default
10522 Show the current handling of accesses to unknown memory.
10526 @c @subsubsection Memory Write Verification
10527 @c The memory write verification attributes set whether @value{GDBN}
10528 @c will re-reads data after each write to verify the write was successful.
10532 @c @item noverify (default)
10535 @node Dump/Restore Files
10536 @section Copy Between Memory and a File
10537 @cindex dump/restore files
10538 @cindex append data to a file
10539 @cindex dump data to a file
10540 @cindex restore data from a file
10542 You can use the commands @code{dump}, @code{append}, and
10543 @code{restore} to copy data between target memory and a file. The
10544 @code{dump} and @code{append} commands write data to a file, and the
10545 @code{restore} command reads data from a file back into the inferior's
10546 memory. Files may be in binary, Motorola S-record, Intel hex, or
10547 Tektronix Hex format; however, @value{GDBN} can only append to binary
10553 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10554 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
10555 Dump the contents of memory from @var{start_addr} to @var{end_addr},
10556 or the value of @var{expr}, to @var{filename} in the given format.
10558 The @var{format} parameter may be any one of:
10565 Motorola S-record format.
10567 Tektronix Hex format.
10570 @value{GDBN} uses the same definitions of these formats as the
10571 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
10572 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
10576 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10577 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
10578 Append the contents of memory from @var{start_addr} to @var{end_addr},
10579 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
10580 (@value{GDBN} can only append data to files in raw binary form.)
10583 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
10584 Restore the contents of file @var{filename} into memory. The
10585 @code{restore} command can automatically recognize any known @sc{bfd}
10586 file format, except for raw binary. To restore a raw binary file you
10587 must specify the optional keyword @code{binary} after the filename.
10589 If @var{bias} is non-zero, its value will be added to the addresses
10590 contained in the file. Binary files always start at address zero, so
10591 they will be restored at address @var{bias}. Other bfd files have
10592 a built-in location; they will be restored at offset @var{bias}
10593 from that location.
10595 If @var{start} and/or @var{end} are non-zero, then only data between
10596 file offset @var{start} and file offset @var{end} will be restored.
10597 These offsets are relative to the addresses in the file, before
10598 the @var{bias} argument is applied.
10602 @node Core File Generation
10603 @section How to Produce a Core File from Your Program
10604 @cindex dump core from inferior
10606 A @dfn{core file} or @dfn{core dump} is a file that records the memory
10607 image of a running process and its process status (register values
10608 etc.). Its primary use is post-mortem debugging of a program that
10609 crashed while it ran outside a debugger. A program that crashes
10610 automatically produces a core file, unless this feature is disabled by
10611 the user. @xref{Files}, for information on invoking @value{GDBN} in
10612 the post-mortem debugging mode.
10614 Occasionally, you may wish to produce a core file of the program you
10615 are debugging in order to preserve a snapshot of its state.
10616 @value{GDBN} has a special command for that.
10620 @kindex generate-core-file
10621 @item generate-core-file [@var{file}]
10622 @itemx gcore [@var{file}]
10623 Produce a core dump of the inferior process. The optional argument
10624 @var{file} specifies the file name where to put the core dump. If not
10625 specified, the file name defaults to @file{core.@var{pid}}, where
10626 @var{pid} is the inferior process ID.
10628 Note that this command is implemented only for some systems (as of
10629 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
10632 @node Character Sets
10633 @section Character Sets
10634 @cindex character sets
10636 @cindex translating between character sets
10637 @cindex host character set
10638 @cindex target character set
10640 If the program you are debugging uses a different character set to
10641 represent characters and strings than the one @value{GDBN} uses itself,
10642 @value{GDBN} can automatically translate between the character sets for
10643 you. The character set @value{GDBN} uses we call the @dfn{host
10644 character set}; the one the inferior program uses we call the
10645 @dfn{target character set}.
10647 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
10648 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
10649 remote protocol (@pxref{Remote Debugging}) to debug a program
10650 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
10651 then the host character set is Latin-1, and the target character set is
10652 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
10653 target-charset EBCDIC-US}, then @value{GDBN} translates between
10654 @sc{ebcdic} and Latin 1 as you print character or string values, or use
10655 character and string literals in expressions.
10657 @value{GDBN} has no way to automatically recognize which character set
10658 the inferior program uses; you must tell it, using the @code{set
10659 target-charset} command, described below.
10661 Here are the commands for controlling @value{GDBN}'s character set
10665 @item set target-charset @var{charset}
10666 @kindex set target-charset
10667 Set the current target character set to @var{charset}. To display the
10668 list of supported target character sets, type
10669 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
10671 @item set host-charset @var{charset}
10672 @kindex set host-charset
10673 Set the current host character set to @var{charset}.
10675 By default, @value{GDBN} uses a host character set appropriate to the
10676 system it is running on; you can override that default using the
10677 @code{set host-charset} command. On some systems, @value{GDBN} cannot
10678 automatically determine the appropriate host character set. In this
10679 case, @value{GDBN} uses @samp{UTF-8}.
10681 @value{GDBN} can only use certain character sets as its host character
10682 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
10683 @value{GDBN} will list the host character sets it supports.
10685 @item set charset @var{charset}
10686 @kindex set charset
10687 Set the current host and target character sets to @var{charset}. As
10688 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
10689 @value{GDBN} will list the names of the character sets that can be used
10690 for both host and target.
10693 @kindex show charset
10694 Show the names of the current host and target character sets.
10696 @item show host-charset
10697 @kindex show host-charset
10698 Show the name of the current host character set.
10700 @item show target-charset
10701 @kindex show target-charset
10702 Show the name of the current target character set.
10704 @item set target-wide-charset @var{charset}
10705 @kindex set target-wide-charset
10706 Set the current target's wide character set to @var{charset}. This is
10707 the character set used by the target's @code{wchar_t} type. To
10708 display the list of supported wide character sets, type
10709 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
10711 @item show target-wide-charset
10712 @kindex show target-wide-charset
10713 Show the name of the current target's wide character set.
10716 Here is an example of @value{GDBN}'s character set support in action.
10717 Assume that the following source code has been placed in the file
10718 @file{charset-test.c}:
10724 = @{72, 101, 108, 108, 111, 44, 32, 119,
10725 111, 114, 108, 100, 33, 10, 0@};
10726 char ibm1047_hello[]
10727 = @{200, 133, 147, 147, 150, 107, 64, 166,
10728 150, 153, 147, 132, 90, 37, 0@};
10732 printf ("Hello, world!\n");
10736 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
10737 containing the string @samp{Hello, world!} followed by a newline,
10738 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
10740 We compile the program, and invoke the debugger on it:
10743 $ gcc -g charset-test.c -o charset-test
10744 $ gdb -nw charset-test
10745 GNU gdb 2001-12-19-cvs
10746 Copyright 2001 Free Software Foundation, Inc.
10751 We can use the @code{show charset} command to see what character sets
10752 @value{GDBN} is currently using to interpret and display characters and
10756 (@value{GDBP}) show charset
10757 The current host and target character set is `ISO-8859-1'.
10761 For the sake of printing this manual, let's use @sc{ascii} as our
10762 initial character set:
10764 (@value{GDBP}) set charset ASCII
10765 (@value{GDBP}) show charset
10766 The current host and target character set is `ASCII'.
10770 Let's assume that @sc{ascii} is indeed the correct character set for our
10771 host system --- in other words, let's assume that if @value{GDBN} prints
10772 characters using the @sc{ascii} character set, our terminal will display
10773 them properly. Since our current target character set is also
10774 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
10777 (@value{GDBP}) print ascii_hello
10778 $1 = 0x401698 "Hello, world!\n"
10779 (@value{GDBP}) print ascii_hello[0]
10784 @value{GDBN} uses the target character set for character and string
10785 literals you use in expressions:
10788 (@value{GDBP}) print '+'
10793 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
10796 @value{GDBN} relies on the user to tell it which character set the
10797 target program uses. If we print @code{ibm1047_hello} while our target
10798 character set is still @sc{ascii}, we get jibberish:
10801 (@value{GDBP}) print ibm1047_hello
10802 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
10803 (@value{GDBP}) print ibm1047_hello[0]
10808 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
10809 @value{GDBN} tells us the character sets it supports:
10812 (@value{GDBP}) set target-charset
10813 ASCII EBCDIC-US IBM1047 ISO-8859-1
10814 (@value{GDBP}) set target-charset
10817 We can select @sc{ibm1047} as our target character set, and examine the
10818 program's strings again. Now the @sc{ascii} string is wrong, but
10819 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
10820 target character set, @sc{ibm1047}, to the host character set,
10821 @sc{ascii}, and they display correctly:
10824 (@value{GDBP}) set target-charset IBM1047
10825 (@value{GDBP}) show charset
10826 The current host character set is `ASCII'.
10827 The current target character set is `IBM1047'.
10828 (@value{GDBP}) print ascii_hello
10829 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
10830 (@value{GDBP}) print ascii_hello[0]
10832 (@value{GDBP}) print ibm1047_hello
10833 $8 = 0x4016a8 "Hello, world!\n"
10834 (@value{GDBP}) print ibm1047_hello[0]
10839 As above, @value{GDBN} uses the target character set for character and
10840 string literals you use in expressions:
10843 (@value{GDBP}) print '+'
10848 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
10851 @node Caching Target Data
10852 @section Caching Data of Targets
10853 @cindex caching data of targets
10855 @value{GDBN} caches data exchanged between the debugger and a target.
10856 Each cache is associated with the address space of the inferior.
10857 @xref{Inferiors and Programs}, about inferior and address space.
10858 Such caching generally improves performance in remote debugging
10859 (@pxref{Remote Debugging}), because it reduces the overhead of the
10860 remote protocol by bundling memory reads and writes into large chunks.
10861 Unfortunately, simply caching everything would lead to incorrect results,
10862 since @value{GDBN} does not necessarily know anything about volatile
10863 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
10864 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
10866 Therefore, by default, @value{GDBN} only caches data
10867 known to be on the stack@footnote{In non-stop mode, it is moderately
10868 rare for a running thread to modify the stack of a stopped thread
10869 in a way that would interfere with a backtrace, and caching of
10870 stack reads provides a significant speed up of remote backtraces.} or
10871 in the code segment.
10872 Other regions of memory can be explicitly marked as
10873 cacheable; @pxref{Memory Region Attributes}.
10876 @kindex set remotecache
10877 @item set remotecache on
10878 @itemx set remotecache off
10879 This option no longer does anything; it exists for compatibility
10882 @kindex show remotecache
10883 @item show remotecache
10884 Show the current state of the obsolete remotecache flag.
10886 @kindex set stack-cache
10887 @item set stack-cache on
10888 @itemx set stack-cache off
10889 Enable or disable caching of stack accesses. When @code{on}, use
10890 caching. By default, this option is @code{on}.
10892 @kindex show stack-cache
10893 @item show stack-cache
10894 Show the current state of data caching for memory accesses.
10896 @kindex set code-cache
10897 @item set code-cache on
10898 @itemx set code-cache off
10899 Enable or disable caching of code segment accesses. When @code{on},
10900 use caching. By default, this option is @code{on}. This improves
10901 performance of disassembly in remote debugging.
10903 @kindex show code-cache
10904 @item show code-cache
10905 Show the current state of target memory cache for code segment
10908 @kindex info dcache
10909 @item info dcache @r{[}line@r{]}
10910 Print the information about the performance of data cache of the
10911 current inferior's address space. The information displayed
10912 includes the dcache width and depth, and for each cache line, its
10913 number, address, and how many times it was referenced. This
10914 command is useful for debugging the data cache operation.
10916 If a line number is specified, the contents of that line will be
10919 @item set dcache size @var{size}
10920 @cindex dcache size
10921 @kindex set dcache size
10922 Set maximum number of entries in dcache (dcache depth above).
10924 @item set dcache line-size @var{line-size}
10925 @cindex dcache line-size
10926 @kindex set dcache line-size
10927 Set number of bytes each dcache entry caches (dcache width above).
10928 Must be a power of 2.
10930 @item show dcache size
10931 @kindex show dcache size
10932 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
10934 @item show dcache line-size
10935 @kindex show dcache line-size
10936 Show default size of dcache lines.
10940 @node Searching Memory
10941 @section Search Memory
10942 @cindex searching memory
10944 Memory can be searched for a particular sequence of bytes with the
10945 @code{find} command.
10949 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10950 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10951 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
10952 etc. The search begins at address @var{start_addr} and continues for either
10953 @var{len} bytes or through to @var{end_addr} inclusive.
10956 @var{s} and @var{n} are optional parameters.
10957 They may be specified in either order, apart or together.
10960 @item @var{s}, search query size
10961 The size of each search query value.
10967 halfwords (two bytes)
10971 giant words (eight bytes)
10974 All values are interpreted in the current language.
10975 This means, for example, that if the current source language is C/C@t{++}
10976 then searching for the string ``hello'' includes the trailing '\0'.
10978 If the value size is not specified, it is taken from the
10979 value's type in the current language.
10980 This is useful when one wants to specify the search
10981 pattern as a mixture of types.
10982 Note that this means, for example, that in the case of C-like languages
10983 a search for an untyped 0x42 will search for @samp{(int) 0x42}
10984 which is typically four bytes.
10986 @item @var{n}, maximum number of finds
10987 The maximum number of matches to print. The default is to print all finds.
10990 You can use strings as search values. Quote them with double-quotes
10992 The string value is copied into the search pattern byte by byte,
10993 regardless of the endianness of the target and the size specification.
10995 The address of each match found is printed as well as a count of the
10996 number of matches found.
10998 The address of the last value found is stored in convenience variable
11000 A count of the number of matches is stored in @samp{$numfound}.
11002 For example, if stopped at the @code{printf} in this function:
11008 static char hello[] = "hello-hello";
11009 static struct @{ char c; short s; int i; @}
11010 __attribute__ ((packed)) mixed
11011 = @{ 'c', 0x1234, 0x87654321 @};
11012 printf ("%s\n", hello);
11017 you get during debugging:
11020 (gdb) find &hello[0], +sizeof(hello), "hello"
11021 0x804956d <hello.1620+6>
11023 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
11024 0x8049567 <hello.1620>
11025 0x804956d <hello.1620+6>
11027 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
11028 0x8049567 <hello.1620>
11030 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
11031 0x8049560 <mixed.1625>
11033 (gdb) print $numfound
11036 $2 = (void *) 0x8049560
11039 @node Optimized Code
11040 @chapter Debugging Optimized Code
11041 @cindex optimized code, debugging
11042 @cindex debugging optimized code
11044 Almost all compilers support optimization. With optimization
11045 disabled, the compiler generates assembly code that corresponds
11046 directly to your source code, in a simplistic way. As the compiler
11047 applies more powerful optimizations, the generated assembly code
11048 diverges from your original source code. With help from debugging
11049 information generated by the compiler, @value{GDBN} can map from
11050 the running program back to constructs from your original source.
11052 @value{GDBN} is more accurate with optimization disabled. If you
11053 can recompile without optimization, it is easier to follow the
11054 progress of your program during debugging. But, there are many cases
11055 where you may need to debug an optimized version.
11057 When you debug a program compiled with @samp{-g -O}, remember that the
11058 optimizer has rearranged your code; the debugger shows you what is
11059 really there. Do not be too surprised when the execution path does not
11060 exactly match your source file! An extreme example: if you define a
11061 variable, but never use it, @value{GDBN} never sees that
11062 variable---because the compiler optimizes it out of existence.
11064 Some things do not work as well with @samp{-g -O} as with just
11065 @samp{-g}, particularly on machines with instruction scheduling. If in
11066 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
11067 please report it to us as a bug (including a test case!).
11068 @xref{Variables}, for more information about debugging optimized code.
11071 * Inline Functions:: How @value{GDBN} presents inlining
11072 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
11075 @node Inline Functions
11076 @section Inline Functions
11077 @cindex inline functions, debugging
11079 @dfn{Inlining} is an optimization that inserts a copy of the function
11080 body directly at each call site, instead of jumping to a shared
11081 routine. @value{GDBN} displays inlined functions just like
11082 non-inlined functions. They appear in backtraces. You can view their
11083 arguments and local variables, step into them with @code{step}, skip
11084 them with @code{next}, and escape from them with @code{finish}.
11085 You can check whether a function was inlined by using the
11086 @code{info frame} command.
11088 For @value{GDBN} to support inlined functions, the compiler must
11089 record information about inlining in the debug information ---
11090 @value{NGCC} using the @sc{dwarf 2} format does this, and several
11091 other compilers do also. @value{GDBN} only supports inlined functions
11092 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
11093 do not emit two required attributes (@samp{DW_AT_call_file} and
11094 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
11095 function calls with earlier versions of @value{NGCC}. It instead
11096 displays the arguments and local variables of inlined functions as
11097 local variables in the caller.
11099 The body of an inlined function is directly included at its call site;
11100 unlike a non-inlined function, there are no instructions devoted to
11101 the call. @value{GDBN} still pretends that the call site and the
11102 start of the inlined function are different instructions. Stepping to
11103 the call site shows the call site, and then stepping again shows
11104 the first line of the inlined function, even though no additional
11105 instructions are executed.
11107 This makes source-level debugging much clearer; you can see both the
11108 context of the call and then the effect of the call. Only stepping by
11109 a single instruction using @code{stepi} or @code{nexti} does not do
11110 this; single instruction steps always show the inlined body.
11112 There are some ways that @value{GDBN} does not pretend that inlined
11113 function calls are the same as normal calls:
11117 Setting breakpoints at the call site of an inlined function may not
11118 work, because the call site does not contain any code. @value{GDBN}
11119 may incorrectly move the breakpoint to the next line of the enclosing
11120 function, after the call. This limitation will be removed in a future
11121 version of @value{GDBN}; until then, set a breakpoint on an earlier line
11122 or inside the inlined function instead.
11125 @value{GDBN} cannot locate the return value of inlined calls after
11126 using the @code{finish} command. This is a limitation of compiler-generated
11127 debugging information; after @code{finish}, you can step to the next line
11128 and print a variable where your program stored the return value.
11132 @node Tail Call Frames
11133 @section Tail Call Frames
11134 @cindex tail call frames, debugging
11136 Function @code{B} can call function @code{C} in its very last statement. In
11137 unoptimized compilation the call of @code{C} is immediately followed by return
11138 instruction at the end of @code{B} code. Optimizing compiler may replace the
11139 call and return in function @code{B} into one jump to function @code{C}
11140 instead. Such use of a jump instruction is called @dfn{tail call}.
11142 During execution of function @code{C}, there will be no indication in the
11143 function call stack frames that it was tail-called from @code{B}. If function
11144 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
11145 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
11146 some cases @value{GDBN} can determine that @code{C} was tail-called from
11147 @code{B}, and it will then create fictitious call frame for that, with the
11148 return address set up as if @code{B} called @code{C} normally.
11150 This functionality is currently supported only by DWARF 2 debugging format and
11151 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
11152 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
11155 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
11156 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
11160 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
11162 Stack level 1, frame at 0x7fffffffda30:
11163 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
11164 tail call frame, caller of frame at 0x7fffffffda30
11165 source language c++.
11166 Arglist at unknown address.
11167 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
11170 The detection of all the possible code path executions can find them ambiguous.
11171 There is no execution history stored (possible @ref{Reverse Execution} is never
11172 used for this purpose) and the last known caller could have reached the known
11173 callee by multiple different jump sequences. In such case @value{GDBN} still
11174 tries to show at least all the unambiguous top tail callers and all the
11175 unambiguous bottom tail calees, if any.
11178 @anchor{set debug entry-values}
11179 @item set debug entry-values
11180 @kindex set debug entry-values
11181 When set to on, enables printing of analysis messages for both frame argument
11182 values at function entry and tail calls. It will show all the possible valid
11183 tail calls code paths it has considered. It will also print the intersection
11184 of them with the final unambiguous (possibly partial or even empty) code path
11187 @item show debug entry-values
11188 @kindex show debug entry-values
11189 Show the current state of analysis messages printing for both frame argument
11190 values at function entry and tail calls.
11193 The analysis messages for tail calls can for example show why the virtual tail
11194 call frame for function @code{c} has not been recognized (due to the indirect
11195 reference by variable @code{x}):
11198 static void __attribute__((noinline, noclone)) c (void);
11199 void (*x) (void) = c;
11200 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11201 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
11202 int main (void) @{ x (); return 0; @}
11204 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
11205 DW_TAG_GNU_call_site 0x40039a in main
11207 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11210 #1 0x000000000040039a in main () at t.c:5
11213 Another possibility is an ambiguous virtual tail call frames resolution:
11217 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
11218 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
11219 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
11220 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
11221 static void __attribute__((noinline, noclone)) b (void)
11222 @{ if (i) c (); else e (); @}
11223 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
11224 int main (void) @{ a (); return 0; @}
11226 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
11227 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
11228 tailcall: reduced: 0x4004d2(a) |
11231 #1 0x00000000004004d2 in a () at t.c:8
11232 #2 0x0000000000400395 in main () at t.c:9
11235 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
11236 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
11238 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
11239 @ifset HAVE_MAKEINFO_CLICK
11240 @set ARROW @click{}
11241 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
11242 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
11244 @ifclear HAVE_MAKEINFO_CLICK
11246 @set CALLSEQ1B @value{CALLSEQ1A}
11247 @set CALLSEQ2B @value{CALLSEQ2A}
11250 Frames #0 and #2 are real, #1 is a virtual tail call frame.
11251 The code can have possible execution paths @value{CALLSEQ1B} or
11252 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
11254 @code{initial:} state shows some random possible calling sequence @value{GDBN}
11255 has found. It then finds another possible calling sequcen - that one is
11256 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
11257 printed as the @code{reduced:} calling sequence. That one could have many
11258 futher @code{compare:} and @code{reduced:} statements as long as there remain
11259 any non-ambiguous sequence entries.
11261 For the frame of function @code{b} in both cases there are different possible
11262 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
11263 also ambigous. The only non-ambiguous frame is the one for function @code{a},
11264 therefore this one is displayed to the user while the ambiguous frames are
11267 There can be also reasons why printing of frame argument values at function
11272 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
11273 static void __attribute__((noinline, noclone)) a (int i);
11274 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
11275 static void __attribute__((noinline, noclone)) a (int i)
11276 @{ if (i) b (i - 1); else c (0); @}
11277 int main (void) @{ a (5); return 0; @}
11280 #0 c (i=i@@entry=0) at t.c:2
11281 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
11282 function "a" at 0x400420 can call itself via tail calls
11283 i=<optimized out>) at t.c:6
11284 #2 0x000000000040036e in main () at t.c:7
11287 @value{GDBN} cannot find out from the inferior state if and how many times did
11288 function @code{a} call itself (via function @code{b}) as these calls would be
11289 tail calls. Such tail calls would modify thue @code{i} variable, therefore
11290 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
11291 prints @code{<optimized out>} instead.
11294 @chapter C Preprocessor Macros
11296 Some languages, such as C and C@t{++}, provide a way to define and invoke
11297 ``preprocessor macros'' which expand into strings of tokens.
11298 @value{GDBN} can evaluate expressions containing macro invocations, show
11299 the result of macro expansion, and show a macro's definition, including
11300 where it was defined.
11302 You may need to compile your program specially to provide @value{GDBN}
11303 with information about preprocessor macros. Most compilers do not
11304 include macros in their debugging information, even when you compile
11305 with the @option{-g} flag. @xref{Compilation}.
11307 A program may define a macro at one point, remove that definition later,
11308 and then provide a different definition after that. Thus, at different
11309 points in the program, a macro may have different definitions, or have
11310 no definition at all. If there is a current stack frame, @value{GDBN}
11311 uses the macros in scope at that frame's source code line. Otherwise,
11312 @value{GDBN} uses the macros in scope at the current listing location;
11315 Whenever @value{GDBN} evaluates an expression, it always expands any
11316 macro invocations present in the expression. @value{GDBN} also provides
11317 the following commands for working with macros explicitly.
11321 @kindex macro expand
11322 @cindex macro expansion, showing the results of preprocessor
11323 @cindex preprocessor macro expansion, showing the results of
11324 @cindex expanding preprocessor macros
11325 @item macro expand @var{expression}
11326 @itemx macro exp @var{expression}
11327 Show the results of expanding all preprocessor macro invocations in
11328 @var{expression}. Since @value{GDBN} simply expands macros, but does
11329 not parse the result, @var{expression} need not be a valid expression;
11330 it can be any string of tokens.
11333 @item macro expand-once @var{expression}
11334 @itemx macro exp1 @var{expression}
11335 @cindex expand macro once
11336 @i{(This command is not yet implemented.)} Show the results of
11337 expanding those preprocessor macro invocations that appear explicitly in
11338 @var{expression}. Macro invocations appearing in that expansion are
11339 left unchanged. This command allows you to see the effect of a
11340 particular macro more clearly, without being confused by further
11341 expansions. Since @value{GDBN} simply expands macros, but does not
11342 parse the result, @var{expression} need not be a valid expression; it
11343 can be any string of tokens.
11346 @cindex macro definition, showing
11347 @cindex definition of a macro, showing
11348 @cindex macros, from debug info
11349 @item info macro [-a|-all] [--] @var{macro}
11350 Show the current definition or all definitions of the named @var{macro},
11351 and describe the source location or compiler command-line where that
11352 definition was established. The optional double dash is to signify the end of
11353 argument processing and the beginning of @var{macro} for non C-like macros where
11354 the macro may begin with a hyphen.
11356 @kindex info macros
11357 @item info macros @var{linespec}
11358 Show all macro definitions that are in effect at the location specified
11359 by @var{linespec}, and describe the source location or compiler
11360 command-line where those definitions were established.
11362 @kindex macro define
11363 @cindex user-defined macros
11364 @cindex defining macros interactively
11365 @cindex macros, user-defined
11366 @item macro define @var{macro} @var{replacement-list}
11367 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
11368 Introduce a definition for a preprocessor macro named @var{macro},
11369 invocations of which are replaced by the tokens given in
11370 @var{replacement-list}. The first form of this command defines an
11371 ``object-like'' macro, which takes no arguments; the second form
11372 defines a ``function-like'' macro, which takes the arguments given in
11375 A definition introduced by this command is in scope in every
11376 expression evaluated in @value{GDBN}, until it is removed with the
11377 @code{macro undef} command, described below. The definition overrides
11378 all definitions for @var{macro} present in the program being debugged,
11379 as well as any previous user-supplied definition.
11381 @kindex macro undef
11382 @item macro undef @var{macro}
11383 Remove any user-supplied definition for the macro named @var{macro}.
11384 This command only affects definitions provided with the @code{macro
11385 define} command, described above; it cannot remove definitions present
11386 in the program being debugged.
11390 List all the macros defined using the @code{macro define} command.
11393 @cindex macros, example of debugging with
11394 Here is a transcript showing the above commands in action. First, we
11395 show our source files:
11400 #include "sample.h"
11403 #define ADD(x) (M + x)
11408 printf ("Hello, world!\n");
11410 printf ("We're so creative.\n");
11412 printf ("Goodbye, world!\n");
11419 Now, we compile the program using the @sc{gnu} C compiler,
11420 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
11421 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
11422 and @option{-gdwarf-4}; we recommend always choosing the most recent
11423 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
11424 includes information about preprocessor macros in the debugging
11428 $ gcc -gdwarf-2 -g3 sample.c -o sample
11432 Now, we start @value{GDBN} on our sample program:
11436 GNU gdb 2002-05-06-cvs
11437 Copyright 2002 Free Software Foundation, Inc.
11438 GDB is free software, @dots{}
11442 We can expand macros and examine their definitions, even when the
11443 program is not running. @value{GDBN} uses the current listing position
11444 to decide which macro definitions are in scope:
11447 (@value{GDBP}) list main
11450 5 #define ADD(x) (M + x)
11455 10 printf ("Hello, world!\n");
11457 12 printf ("We're so creative.\n");
11458 (@value{GDBP}) info macro ADD
11459 Defined at /home/jimb/gdb/macros/play/sample.c:5
11460 #define ADD(x) (M + x)
11461 (@value{GDBP}) info macro Q
11462 Defined at /home/jimb/gdb/macros/play/sample.h:1
11463 included at /home/jimb/gdb/macros/play/sample.c:2
11465 (@value{GDBP}) macro expand ADD(1)
11466 expands to: (42 + 1)
11467 (@value{GDBP}) macro expand-once ADD(1)
11468 expands to: once (M + 1)
11472 In the example above, note that @code{macro expand-once} expands only
11473 the macro invocation explicit in the original text --- the invocation of
11474 @code{ADD} --- but does not expand the invocation of the macro @code{M},
11475 which was introduced by @code{ADD}.
11477 Once the program is running, @value{GDBN} uses the macro definitions in
11478 force at the source line of the current stack frame:
11481 (@value{GDBP}) break main
11482 Breakpoint 1 at 0x8048370: file sample.c, line 10.
11484 Starting program: /home/jimb/gdb/macros/play/sample
11486 Breakpoint 1, main () at sample.c:10
11487 10 printf ("Hello, world!\n");
11491 At line 10, the definition of the macro @code{N} at line 9 is in force:
11494 (@value{GDBP}) info macro N
11495 Defined at /home/jimb/gdb/macros/play/sample.c:9
11497 (@value{GDBP}) macro expand N Q M
11498 expands to: 28 < 42
11499 (@value{GDBP}) print N Q M
11504 As we step over directives that remove @code{N}'s definition, and then
11505 give it a new definition, @value{GDBN} finds the definition (or lack
11506 thereof) in force at each point:
11509 (@value{GDBP}) next
11511 12 printf ("We're so creative.\n");
11512 (@value{GDBP}) info macro N
11513 The symbol `N' has no definition as a C/C++ preprocessor macro
11514 at /home/jimb/gdb/macros/play/sample.c:12
11515 (@value{GDBP}) next
11517 14 printf ("Goodbye, world!\n");
11518 (@value{GDBP}) info macro N
11519 Defined at /home/jimb/gdb/macros/play/sample.c:13
11521 (@value{GDBP}) macro expand N Q M
11522 expands to: 1729 < 42
11523 (@value{GDBP}) print N Q M
11528 In addition to source files, macros can be defined on the compilation command
11529 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
11530 such a way, @value{GDBN} displays the location of their definition as line zero
11531 of the source file submitted to the compiler.
11534 (@value{GDBP}) info macro __STDC__
11535 Defined at /home/jimb/gdb/macros/play/sample.c:0
11542 @chapter Tracepoints
11543 @c This chapter is based on the documentation written by Michael
11544 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
11546 @cindex tracepoints
11547 In some applications, it is not feasible for the debugger to interrupt
11548 the program's execution long enough for the developer to learn
11549 anything helpful about its behavior. If the program's correctness
11550 depends on its real-time behavior, delays introduced by a debugger
11551 might cause the program to change its behavior drastically, or perhaps
11552 fail, even when the code itself is correct. It is useful to be able
11553 to observe the program's behavior without interrupting it.
11555 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
11556 specify locations in the program, called @dfn{tracepoints}, and
11557 arbitrary expressions to evaluate when those tracepoints are reached.
11558 Later, using the @code{tfind} command, you can examine the values
11559 those expressions had when the program hit the tracepoints. The
11560 expressions may also denote objects in memory---structures or arrays,
11561 for example---whose values @value{GDBN} should record; while visiting
11562 a particular tracepoint, you may inspect those objects as if they were
11563 in memory at that moment. However, because @value{GDBN} records these
11564 values without interacting with you, it can do so quickly and
11565 unobtrusively, hopefully not disturbing the program's behavior.
11567 The tracepoint facility is currently available only for remote
11568 targets. @xref{Targets}. In addition, your remote target must know
11569 how to collect trace data. This functionality is implemented in the
11570 remote stub; however, none of the stubs distributed with @value{GDBN}
11571 support tracepoints as of this writing. The format of the remote
11572 packets used to implement tracepoints are described in @ref{Tracepoint
11575 It is also possible to get trace data from a file, in a manner reminiscent
11576 of corefiles; you specify the filename, and use @code{tfind} to search
11577 through the file. @xref{Trace Files}, for more details.
11579 This chapter describes the tracepoint commands and features.
11582 * Set Tracepoints::
11583 * Analyze Collected Data::
11584 * Tracepoint Variables::
11588 @node Set Tracepoints
11589 @section Commands to Set Tracepoints
11591 Before running such a @dfn{trace experiment}, an arbitrary number of
11592 tracepoints can be set. A tracepoint is actually a special type of
11593 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
11594 standard breakpoint commands. For instance, as with breakpoints,
11595 tracepoint numbers are successive integers starting from one, and many
11596 of the commands associated with tracepoints take the tracepoint number
11597 as their argument, to identify which tracepoint to work on.
11599 For each tracepoint, you can specify, in advance, some arbitrary set
11600 of data that you want the target to collect in the trace buffer when
11601 it hits that tracepoint. The collected data can include registers,
11602 local variables, or global data. Later, you can use @value{GDBN}
11603 commands to examine the values these data had at the time the
11604 tracepoint was hit.
11606 Tracepoints do not support every breakpoint feature. Ignore counts on
11607 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
11608 commands when they are hit. Tracepoints may not be thread-specific
11611 @cindex fast tracepoints
11612 Some targets may support @dfn{fast tracepoints}, which are inserted in
11613 a different way (such as with a jump instead of a trap), that is
11614 faster but possibly restricted in where they may be installed.
11616 @cindex static tracepoints
11617 @cindex markers, static tracepoints
11618 @cindex probing markers, static tracepoints
11619 Regular and fast tracepoints are dynamic tracing facilities, meaning
11620 that they can be used to insert tracepoints at (almost) any location
11621 in the target. Some targets may also support controlling @dfn{static
11622 tracepoints} from @value{GDBN}. With static tracing, a set of
11623 instrumentation points, also known as @dfn{markers}, are embedded in
11624 the target program, and can be activated or deactivated by name or
11625 address. These are usually placed at locations which facilitate
11626 investigating what the target is actually doing. @value{GDBN}'s
11627 support for static tracing includes being able to list instrumentation
11628 points, and attach them with @value{GDBN} defined high level
11629 tracepoints that expose the whole range of convenience of
11630 @value{GDBN}'s tracepoints support. Namely, support for collecting
11631 registers values and values of global or local (to the instrumentation
11632 point) variables; tracepoint conditions and trace state variables.
11633 The act of installing a @value{GDBN} static tracepoint on an
11634 instrumentation point, or marker, is referred to as @dfn{probing} a
11635 static tracepoint marker.
11637 @code{gdbserver} supports tracepoints on some target systems.
11638 @xref{Server,,Tracepoints support in @code{gdbserver}}.
11640 This section describes commands to set tracepoints and associated
11641 conditions and actions.
11644 * Create and Delete Tracepoints::
11645 * Enable and Disable Tracepoints::
11646 * Tracepoint Passcounts::
11647 * Tracepoint Conditions::
11648 * Trace State Variables::
11649 * Tracepoint Actions::
11650 * Listing Tracepoints::
11651 * Listing Static Tracepoint Markers::
11652 * Starting and Stopping Trace Experiments::
11653 * Tracepoint Restrictions::
11656 @node Create and Delete Tracepoints
11657 @subsection Create and Delete Tracepoints
11660 @cindex set tracepoint
11662 @item trace @var{location}
11663 The @code{trace} command is very similar to the @code{break} command.
11664 Its argument @var{location} can be a source line, a function name, or
11665 an address in the target program. @xref{Specify Location}. The
11666 @code{trace} command defines a tracepoint, which is a point in the
11667 target program where the debugger will briefly stop, collect some
11668 data, and then allow the program to continue. Setting a tracepoint or
11669 changing its actions takes effect immediately if the remote stub
11670 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
11672 If remote stub doesn't support the @samp{InstallInTrace} feature, all
11673 these changes don't take effect until the next @code{tstart}
11674 command, and once a trace experiment is running, further changes will
11675 not have any effect until the next trace experiment starts. In addition,
11676 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
11677 address is not yet resolved. (This is similar to pending breakpoints.)
11678 Pending tracepoints are not downloaded to the target and not installed
11679 until they are resolved. The resolution of pending tracepoints requires
11680 @value{GDBN} support---when debugging with the remote target, and
11681 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
11682 tracing}), pending tracepoints can not be resolved (and downloaded to
11683 the remote stub) while @value{GDBN} is disconnected.
11685 Here are some examples of using the @code{trace} command:
11688 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
11690 (@value{GDBP}) @b{trace +2} // 2 lines forward
11692 (@value{GDBP}) @b{trace my_function} // first source line of function
11694 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
11696 (@value{GDBP}) @b{trace *0x2117c4} // an address
11700 You can abbreviate @code{trace} as @code{tr}.
11702 @item trace @var{location} if @var{cond}
11703 Set a tracepoint with condition @var{cond}; evaluate the expression
11704 @var{cond} each time the tracepoint is reached, and collect data only
11705 if the value is nonzero---that is, if @var{cond} evaluates as true.
11706 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
11707 information on tracepoint conditions.
11709 @item ftrace @var{location} [ if @var{cond} ]
11710 @cindex set fast tracepoint
11711 @cindex fast tracepoints, setting
11713 The @code{ftrace} command sets a fast tracepoint. For targets that
11714 support them, fast tracepoints will use a more efficient but possibly
11715 less general technique to trigger data collection, such as a jump
11716 instruction instead of a trap, or some sort of hardware support. It
11717 may not be possible to create a fast tracepoint at the desired
11718 location, in which case the command will exit with an explanatory
11721 @value{GDBN} handles arguments to @code{ftrace} exactly as for
11724 On 32-bit x86-architecture systems, fast tracepoints normally need to
11725 be placed at an instruction that is 5 bytes or longer, but can be
11726 placed at 4-byte instructions if the low 64K of memory of the target
11727 program is available to install trampolines. Some Unix-type systems,
11728 such as @sc{gnu}/Linux, exclude low addresses from the program's
11729 address space; but for instance with the Linux kernel it is possible
11730 to let @value{GDBN} use this area by doing a @command{sysctl} command
11731 to set the @code{mmap_min_addr} kernel parameter, as in
11734 sudo sysctl -w vm.mmap_min_addr=32768
11738 which sets the low address to 32K, which leaves plenty of room for
11739 trampolines. The minimum address should be set to a page boundary.
11741 @item strace @var{location} [ if @var{cond} ]
11742 @cindex set static tracepoint
11743 @cindex static tracepoints, setting
11744 @cindex probe static tracepoint marker
11746 The @code{strace} command sets a static tracepoint. For targets that
11747 support it, setting a static tracepoint probes a static
11748 instrumentation point, or marker, found at @var{location}. It may not
11749 be possible to set a static tracepoint at the desired location, in
11750 which case the command will exit with an explanatory message.
11752 @value{GDBN} handles arguments to @code{strace} exactly as for
11753 @code{trace}, with the addition that the user can also specify
11754 @code{-m @var{marker}} as @var{location}. This probes the marker
11755 identified by the @var{marker} string identifier. This identifier
11756 depends on the static tracepoint backend library your program is
11757 using. You can find all the marker identifiers in the @samp{ID} field
11758 of the @code{info static-tracepoint-markers} command output.
11759 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
11760 Markers}. For example, in the following small program using the UST
11766 trace_mark(ust, bar33, "str %s", "FOOBAZ");
11771 the marker id is composed of joining the first two arguments to the
11772 @code{trace_mark} call with a slash, which translates to:
11775 (@value{GDBP}) info static-tracepoint-markers
11776 Cnt Enb ID Address What
11777 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
11783 so you may probe the marker above with:
11786 (@value{GDBP}) strace -m ust/bar33
11789 Static tracepoints accept an extra collect action --- @code{collect
11790 $_sdata}. This collects arbitrary user data passed in the probe point
11791 call to the tracing library. In the UST example above, you'll see
11792 that the third argument to @code{trace_mark} is a printf-like format
11793 string. The user data is then the result of running that formating
11794 string against the following arguments. Note that @code{info
11795 static-tracepoint-markers} command output lists that format string in
11796 the @samp{Data:} field.
11798 You can inspect this data when analyzing the trace buffer, by printing
11799 the $_sdata variable like any other variable available to
11800 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
11803 @cindex last tracepoint number
11804 @cindex recent tracepoint number
11805 @cindex tracepoint number
11806 The convenience variable @code{$tpnum} records the tracepoint number
11807 of the most recently set tracepoint.
11809 @kindex delete tracepoint
11810 @cindex tracepoint deletion
11811 @item delete tracepoint @r{[}@var{num}@r{]}
11812 Permanently delete one or more tracepoints. With no argument, the
11813 default is to delete all tracepoints. Note that the regular
11814 @code{delete} command can remove tracepoints also.
11819 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
11821 (@value{GDBP}) @b{delete trace} // remove all tracepoints
11825 You can abbreviate this command as @code{del tr}.
11828 @node Enable and Disable Tracepoints
11829 @subsection Enable and Disable Tracepoints
11831 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
11834 @kindex disable tracepoint
11835 @item disable tracepoint @r{[}@var{num}@r{]}
11836 Disable tracepoint @var{num}, or all tracepoints if no argument
11837 @var{num} is given. A disabled tracepoint will have no effect during
11838 a trace experiment, but it is not forgotten. You can re-enable
11839 a disabled tracepoint using the @code{enable tracepoint} command.
11840 If the command is issued during a trace experiment and the debug target
11841 has support for disabling tracepoints during a trace experiment, then the
11842 change will be effective immediately. Otherwise, it will be applied to the
11843 next trace experiment.
11845 @kindex enable tracepoint
11846 @item enable tracepoint @r{[}@var{num}@r{]}
11847 Enable tracepoint @var{num}, or all tracepoints. If this command is
11848 issued during a trace experiment and the debug target supports enabling
11849 tracepoints during a trace experiment, then the enabled tracepoints will
11850 become effective immediately. Otherwise, they will become effective the
11851 next time a trace experiment is run.
11854 @node Tracepoint Passcounts
11855 @subsection Tracepoint Passcounts
11859 @cindex tracepoint pass count
11860 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
11861 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
11862 automatically stop a trace experiment. If a tracepoint's passcount is
11863 @var{n}, then the trace experiment will be automatically stopped on
11864 the @var{n}'th time that tracepoint is hit. If the tracepoint number
11865 @var{num} is not specified, the @code{passcount} command sets the
11866 passcount of the most recently defined tracepoint. If no passcount is
11867 given, the trace experiment will run until stopped explicitly by the
11873 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
11874 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
11876 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
11877 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
11878 (@value{GDBP}) @b{trace foo}
11879 (@value{GDBP}) @b{pass 3}
11880 (@value{GDBP}) @b{trace bar}
11881 (@value{GDBP}) @b{pass 2}
11882 (@value{GDBP}) @b{trace baz}
11883 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
11884 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
11885 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
11886 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
11890 @node Tracepoint Conditions
11891 @subsection Tracepoint Conditions
11892 @cindex conditional tracepoints
11893 @cindex tracepoint conditions
11895 The simplest sort of tracepoint collects data every time your program
11896 reaches a specified place. You can also specify a @dfn{condition} for
11897 a tracepoint. A condition is just a Boolean expression in your
11898 programming language (@pxref{Expressions, ,Expressions}). A
11899 tracepoint with a condition evaluates the expression each time your
11900 program reaches it, and data collection happens only if the condition
11903 Tracepoint conditions can be specified when a tracepoint is set, by
11904 using @samp{if} in the arguments to the @code{trace} command.
11905 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
11906 also be set or changed at any time with the @code{condition} command,
11907 just as with breakpoints.
11909 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
11910 the conditional expression itself. Instead, @value{GDBN} encodes the
11911 expression into an agent expression (@pxref{Agent Expressions})
11912 suitable for execution on the target, independently of @value{GDBN}.
11913 Global variables become raw memory locations, locals become stack
11914 accesses, and so forth.
11916 For instance, suppose you have a function that is usually called
11917 frequently, but should not be called after an error has occurred. You
11918 could use the following tracepoint command to collect data about calls
11919 of that function that happen while the error code is propagating
11920 through the program; an unconditional tracepoint could end up
11921 collecting thousands of useless trace frames that you would have to
11925 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
11928 @node Trace State Variables
11929 @subsection Trace State Variables
11930 @cindex trace state variables
11932 A @dfn{trace state variable} is a special type of variable that is
11933 created and managed by target-side code. The syntax is the same as
11934 that for GDB's convenience variables (a string prefixed with ``$''),
11935 but they are stored on the target. They must be created explicitly,
11936 using a @code{tvariable} command. They are always 64-bit signed
11939 Trace state variables are remembered by @value{GDBN}, and downloaded
11940 to the target along with tracepoint information when the trace
11941 experiment starts. There are no intrinsic limits on the number of
11942 trace state variables, beyond memory limitations of the target.
11944 @cindex convenience variables, and trace state variables
11945 Although trace state variables are managed by the target, you can use
11946 them in print commands and expressions as if they were convenience
11947 variables; @value{GDBN} will get the current value from the target
11948 while the trace experiment is running. Trace state variables share
11949 the same namespace as other ``$'' variables, which means that you
11950 cannot have trace state variables with names like @code{$23} or
11951 @code{$pc}, nor can you have a trace state variable and a convenience
11952 variable with the same name.
11956 @item tvariable $@var{name} [ = @var{expression} ]
11958 The @code{tvariable} command creates a new trace state variable named
11959 @code{$@var{name}}, and optionally gives it an initial value of
11960 @var{expression}. @var{expression} is evaluated when this command is
11961 entered; the result will be converted to an integer if possible,
11962 otherwise @value{GDBN} will report an error. A subsequent
11963 @code{tvariable} command specifying the same name does not create a
11964 variable, but instead assigns the supplied initial value to the
11965 existing variable of that name, overwriting any previous initial
11966 value. The default initial value is 0.
11968 @item info tvariables
11969 @kindex info tvariables
11970 List all the trace state variables along with their initial values.
11971 Their current values may also be displayed, if the trace experiment is
11974 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
11975 @kindex delete tvariable
11976 Delete the given trace state variables, or all of them if no arguments
11981 @node Tracepoint Actions
11982 @subsection Tracepoint Action Lists
11986 @cindex tracepoint actions
11987 @item actions @r{[}@var{num}@r{]}
11988 This command will prompt for a list of actions to be taken when the
11989 tracepoint is hit. If the tracepoint number @var{num} is not
11990 specified, this command sets the actions for the one that was most
11991 recently defined (so that you can define a tracepoint and then say
11992 @code{actions} without bothering about its number). You specify the
11993 actions themselves on the following lines, one action at a time, and
11994 terminate the actions list with a line containing just @code{end}. So
11995 far, the only defined actions are @code{collect}, @code{teval}, and
11996 @code{while-stepping}.
11998 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
11999 Commands, ,Breakpoint Command Lists}), except that only the defined
12000 actions are allowed; any other @value{GDBN} command is rejected.
12002 @cindex remove actions from a tracepoint
12003 To remove all actions from a tracepoint, type @samp{actions @var{num}}
12004 and follow it immediately with @samp{end}.
12007 (@value{GDBP}) @b{collect @var{data}} // collect some data
12009 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
12011 (@value{GDBP}) @b{end} // signals the end of actions.
12014 In the following example, the action list begins with @code{collect}
12015 commands indicating the things to be collected when the tracepoint is
12016 hit. Then, in order to single-step and collect additional data
12017 following the tracepoint, a @code{while-stepping} command is used,
12018 followed by the list of things to be collected after each step in a
12019 sequence of single steps. The @code{while-stepping} command is
12020 terminated by its own separate @code{end} command. Lastly, the action
12021 list is terminated by an @code{end} command.
12024 (@value{GDBP}) @b{trace foo}
12025 (@value{GDBP}) @b{actions}
12026 Enter actions for tracepoint 1, one per line:
12029 > while-stepping 12
12030 > collect $pc, arr[i]
12035 @kindex collect @r{(tracepoints)}
12036 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
12037 Collect values of the given expressions when the tracepoint is hit.
12038 This command accepts a comma-separated list of any valid expressions.
12039 In addition to global, static, or local variables, the following
12040 special arguments are supported:
12044 Collect all registers.
12047 Collect all function arguments.
12050 Collect all local variables.
12053 Collect the return address. This is helpful if you want to see more
12057 Collects the number of arguments from the static probe at which the
12058 tracepoint is located.
12059 @xref{Static Probe Points}.
12061 @item $_probe_arg@var{n}
12062 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
12063 from the static probe at which the tracepoint is located.
12064 @xref{Static Probe Points}.
12067 @vindex $_sdata@r{, collect}
12068 Collect static tracepoint marker specific data. Only available for
12069 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
12070 Lists}. On the UST static tracepoints library backend, an
12071 instrumentation point resembles a @code{printf} function call. The
12072 tracing library is able to collect user specified data formatted to a
12073 character string using the format provided by the programmer that
12074 instrumented the program. Other backends have similar mechanisms.
12075 Here's an example of a UST marker call:
12078 const char master_name[] = "$your_name";
12079 trace_mark(channel1, marker1, "hello %s", master_name)
12082 In this case, collecting @code{$_sdata} collects the string
12083 @samp{hello $yourname}. When analyzing the trace buffer, you can
12084 inspect @samp{$_sdata} like any other variable available to
12088 You can give several consecutive @code{collect} commands, each one
12089 with a single argument, or one @code{collect} command with several
12090 arguments separated by commas; the effect is the same.
12092 The optional @var{mods} changes the usual handling of the arguments.
12093 @code{s} requests that pointers to chars be handled as strings, in
12094 particular collecting the contents of the memory being pointed at, up
12095 to the first zero. The upper bound is by default the value of the
12096 @code{print elements} variable; if @code{s} is followed by a decimal
12097 number, that is the upper bound instead. So for instance
12098 @samp{collect/s25 mystr} collects as many as 25 characters at
12101 The command @code{info scope} (@pxref{Symbols, info scope}) is
12102 particularly useful for figuring out what data to collect.
12104 @kindex teval @r{(tracepoints)}
12105 @item teval @var{expr1}, @var{expr2}, @dots{}
12106 Evaluate the given expressions when the tracepoint is hit. This
12107 command accepts a comma-separated list of expressions. The results
12108 are discarded, so this is mainly useful for assigning values to trace
12109 state variables (@pxref{Trace State Variables}) without adding those
12110 values to the trace buffer, as would be the case if the @code{collect}
12113 @kindex while-stepping @r{(tracepoints)}
12114 @item while-stepping @var{n}
12115 Perform @var{n} single-step instruction traces after the tracepoint,
12116 collecting new data after each step. The @code{while-stepping}
12117 command is followed by the list of what to collect while stepping
12118 (followed by its own @code{end} command):
12121 > while-stepping 12
12122 > collect $regs, myglobal
12128 Note that @code{$pc} is not automatically collected by
12129 @code{while-stepping}; you need to explicitly collect that register if
12130 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
12133 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
12134 @kindex set default-collect
12135 @cindex default collection action
12136 This variable is a list of expressions to collect at each tracepoint
12137 hit. It is effectively an additional @code{collect} action prepended
12138 to every tracepoint action list. The expressions are parsed
12139 individually for each tracepoint, so for instance a variable named
12140 @code{xyz} may be interpreted as a global for one tracepoint, and a
12141 local for another, as appropriate to the tracepoint's location.
12143 @item show default-collect
12144 @kindex show default-collect
12145 Show the list of expressions that are collected by default at each
12150 @node Listing Tracepoints
12151 @subsection Listing Tracepoints
12154 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
12155 @kindex info tp @r{[}@var{n}@dots{}@r{]}
12156 @cindex information about tracepoints
12157 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
12158 Display information about the tracepoint @var{num}. If you don't
12159 specify a tracepoint number, displays information about all the
12160 tracepoints defined so far. The format is similar to that used for
12161 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
12162 command, simply restricting itself to tracepoints.
12164 A tracepoint's listing may include additional information specific to
12169 its passcount as given by the @code{passcount @var{n}} command
12172 the state about installed on target of each location
12176 (@value{GDBP}) @b{info trace}
12177 Num Type Disp Enb Address What
12178 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
12180 collect globfoo, $regs
12185 2 tracepoint keep y <MULTIPLE>
12187 2.1 y 0x0804859c in func4 at change-loc.h:35
12188 installed on target
12189 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
12190 installed on target
12191 2.3 y <PENDING> set_tracepoint
12192 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
12193 not installed on target
12198 This command can be abbreviated @code{info tp}.
12201 @node Listing Static Tracepoint Markers
12202 @subsection Listing Static Tracepoint Markers
12205 @kindex info static-tracepoint-markers
12206 @cindex information about static tracepoint markers
12207 @item info static-tracepoint-markers
12208 Display information about all static tracepoint markers defined in the
12211 For each marker, the following columns are printed:
12215 An incrementing counter, output to help readability. This is not a
12218 The marker ID, as reported by the target.
12219 @item Enabled or Disabled
12220 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
12221 that are not enabled.
12223 Where the marker is in your program, as a memory address.
12225 Where the marker is in the source for your program, as a file and line
12226 number. If the debug information included in the program does not
12227 allow @value{GDBN} to locate the source of the marker, this column
12228 will be left blank.
12232 In addition, the following information may be printed for each marker:
12236 User data passed to the tracing library by the marker call. In the
12237 UST backend, this is the format string passed as argument to the
12239 @item Static tracepoints probing the marker
12240 The list of static tracepoints attached to the marker.
12244 (@value{GDBP}) info static-tracepoint-markers
12245 Cnt ID Enb Address What
12246 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
12247 Data: number1 %d number2 %d
12248 Probed by static tracepoints: #2
12249 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
12255 @node Starting and Stopping Trace Experiments
12256 @subsection Starting and Stopping Trace Experiments
12259 @kindex tstart [ @var{notes} ]
12260 @cindex start a new trace experiment
12261 @cindex collected data discarded
12263 This command starts the trace experiment, and begins collecting data.
12264 It has the side effect of discarding all the data collected in the
12265 trace buffer during the previous trace experiment. If any arguments
12266 are supplied, they are taken as a note and stored with the trace
12267 experiment's state. The notes may be arbitrary text, and are
12268 especially useful with disconnected tracing in a multi-user context;
12269 the notes can explain what the trace is doing, supply user contact
12270 information, and so forth.
12272 @kindex tstop [ @var{notes} ]
12273 @cindex stop a running trace experiment
12275 This command stops the trace experiment. If any arguments are
12276 supplied, they are recorded with the experiment as a note. This is
12277 useful if you are stopping a trace started by someone else, for
12278 instance if the trace is interfering with the system's behavior and
12279 needs to be stopped quickly.
12281 @strong{Note}: a trace experiment and data collection may stop
12282 automatically if any tracepoint's passcount is reached
12283 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
12286 @cindex status of trace data collection
12287 @cindex trace experiment, status of
12289 This command displays the status of the current trace data
12293 Here is an example of the commands we described so far:
12296 (@value{GDBP}) @b{trace gdb_c_test}
12297 (@value{GDBP}) @b{actions}
12298 Enter actions for tracepoint #1, one per line.
12299 > collect $regs,$locals,$args
12300 > while-stepping 11
12304 (@value{GDBP}) @b{tstart}
12305 [time passes @dots{}]
12306 (@value{GDBP}) @b{tstop}
12309 @anchor{disconnected tracing}
12310 @cindex disconnected tracing
12311 You can choose to continue running the trace experiment even if
12312 @value{GDBN} disconnects from the target, voluntarily or
12313 involuntarily. For commands such as @code{detach}, the debugger will
12314 ask what you want to do with the trace. But for unexpected
12315 terminations (@value{GDBN} crash, network outage), it would be
12316 unfortunate to lose hard-won trace data, so the variable
12317 @code{disconnected-tracing} lets you decide whether the trace should
12318 continue running without @value{GDBN}.
12321 @item set disconnected-tracing on
12322 @itemx set disconnected-tracing off
12323 @kindex set disconnected-tracing
12324 Choose whether a tracing run should continue to run if @value{GDBN}
12325 has disconnected from the target. Note that @code{detach} or
12326 @code{quit} will ask you directly what to do about a running trace no
12327 matter what this variable's setting, so the variable is mainly useful
12328 for handling unexpected situations, such as loss of the network.
12330 @item show disconnected-tracing
12331 @kindex show disconnected-tracing
12332 Show the current choice for disconnected tracing.
12336 When you reconnect to the target, the trace experiment may or may not
12337 still be running; it might have filled the trace buffer in the
12338 meantime, or stopped for one of the other reasons. If it is running,
12339 it will continue after reconnection.
12341 Upon reconnection, the target will upload information about the
12342 tracepoints in effect. @value{GDBN} will then compare that
12343 information to the set of tracepoints currently defined, and attempt
12344 to match them up, allowing for the possibility that the numbers may
12345 have changed due to creation and deletion in the meantime. If one of
12346 the target's tracepoints does not match any in @value{GDBN}, the
12347 debugger will create a new tracepoint, so that you have a number with
12348 which to specify that tracepoint. This matching-up process is
12349 necessarily heuristic, and it may result in useless tracepoints being
12350 created; you may simply delete them if they are of no use.
12352 @cindex circular trace buffer
12353 If your target agent supports a @dfn{circular trace buffer}, then you
12354 can run a trace experiment indefinitely without filling the trace
12355 buffer; when space runs out, the agent deletes already-collected trace
12356 frames, oldest first, until there is enough room to continue
12357 collecting. This is especially useful if your tracepoints are being
12358 hit too often, and your trace gets terminated prematurely because the
12359 buffer is full. To ask for a circular trace buffer, simply set
12360 @samp{circular-trace-buffer} to on. You can set this at any time,
12361 including during tracing; if the agent can do it, it will change
12362 buffer handling on the fly, otherwise it will not take effect until
12366 @item set circular-trace-buffer on
12367 @itemx set circular-trace-buffer off
12368 @kindex set circular-trace-buffer
12369 Choose whether a tracing run should use a linear or circular buffer
12370 for trace data. A linear buffer will not lose any trace data, but may
12371 fill up prematurely, while a circular buffer will discard old trace
12372 data, but it will have always room for the latest tracepoint hits.
12374 @item show circular-trace-buffer
12375 @kindex show circular-trace-buffer
12376 Show the current choice for the trace buffer. Note that this may not
12377 match the agent's current buffer handling, nor is it guaranteed to
12378 match the setting that might have been in effect during a past run,
12379 for instance if you are looking at frames from a trace file.
12384 @item set trace-buffer-size @var{n}
12385 @itemx set trace-buffer-size unlimited
12386 @kindex set trace-buffer-size
12387 Request that the target use a trace buffer of @var{n} bytes. Not all
12388 targets will honor the request; they may have a compiled-in size for
12389 the trace buffer, or some other limitation. Set to a value of
12390 @code{unlimited} or @code{-1} to let the target use whatever size it
12391 likes. This is also the default.
12393 @item show trace-buffer-size
12394 @kindex show trace-buffer-size
12395 Show the current requested size for the trace buffer. Note that this
12396 will only match the actual size if the target supports size-setting,
12397 and was able to handle the requested size. For instance, if the
12398 target can only change buffer size between runs, this variable will
12399 not reflect the change until the next run starts. Use @code{tstatus}
12400 to get a report of the actual buffer size.
12404 @item set trace-user @var{text}
12405 @kindex set trace-user
12407 @item show trace-user
12408 @kindex show trace-user
12410 @item set trace-notes @var{text}
12411 @kindex set trace-notes
12412 Set the trace run's notes.
12414 @item show trace-notes
12415 @kindex show trace-notes
12416 Show the trace run's notes.
12418 @item set trace-stop-notes @var{text}
12419 @kindex set trace-stop-notes
12420 Set the trace run's stop notes. The handling of the note is as for
12421 @code{tstop} arguments; the set command is convenient way to fix a
12422 stop note that is mistaken or incomplete.
12424 @item show trace-stop-notes
12425 @kindex show trace-stop-notes
12426 Show the trace run's stop notes.
12430 @node Tracepoint Restrictions
12431 @subsection Tracepoint Restrictions
12433 @cindex tracepoint restrictions
12434 There are a number of restrictions on the use of tracepoints. As
12435 described above, tracepoint data gathering occurs on the target
12436 without interaction from @value{GDBN}. Thus the full capabilities of
12437 the debugger are not available during data gathering, and then at data
12438 examination time, you will be limited by only having what was
12439 collected. The following items describe some common problems, but it
12440 is not exhaustive, and you may run into additional difficulties not
12446 Tracepoint expressions are intended to gather objects (lvalues). Thus
12447 the full flexibility of GDB's expression evaluator is not available.
12448 You cannot call functions, cast objects to aggregate types, access
12449 convenience variables or modify values (except by assignment to trace
12450 state variables). Some language features may implicitly call
12451 functions (for instance Objective-C fields with accessors), and therefore
12452 cannot be collected either.
12455 Collection of local variables, either individually or in bulk with
12456 @code{$locals} or @code{$args}, during @code{while-stepping} may
12457 behave erratically. The stepping action may enter a new scope (for
12458 instance by stepping into a function), or the location of the variable
12459 may change (for instance it is loaded into a register). The
12460 tracepoint data recorded uses the location information for the
12461 variables that is correct for the tracepoint location. When the
12462 tracepoint is created, it is not possible, in general, to determine
12463 where the steps of a @code{while-stepping} sequence will advance the
12464 program---particularly if a conditional branch is stepped.
12467 Collection of an incompletely-initialized or partially-destroyed object
12468 may result in something that @value{GDBN} cannot display, or displays
12469 in a misleading way.
12472 When @value{GDBN} displays a pointer to character it automatically
12473 dereferences the pointer to also display characters of the string
12474 being pointed to. However, collecting the pointer during tracing does
12475 not automatically collect the string. You need to explicitly
12476 dereference the pointer and provide size information if you want to
12477 collect not only the pointer, but the memory pointed to. For example,
12478 @code{*ptr@@50} can be used to collect the 50 element array pointed to
12482 It is not possible to collect a complete stack backtrace at a
12483 tracepoint. Instead, you may collect the registers and a few hundred
12484 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
12485 (adjust to use the name of the actual stack pointer register on your
12486 target architecture, and the amount of stack you wish to capture).
12487 Then the @code{backtrace} command will show a partial backtrace when
12488 using a trace frame. The number of stack frames that can be examined
12489 depends on the sizes of the frames in the collected stack. Note that
12490 if you ask for a block so large that it goes past the bottom of the
12491 stack, the target agent may report an error trying to read from an
12495 If you do not collect registers at a tracepoint, @value{GDBN} can
12496 infer that the value of @code{$pc} must be the same as the address of
12497 the tracepoint and use that when you are looking at a trace frame
12498 for that tracepoint. However, this cannot work if the tracepoint has
12499 multiple locations (for instance if it was set in a function that was
12500 inlined), or if it has a @code{while-stepping} loop. In those cases
12501 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
12506 @node Analyze Collected Data
12507 @section Using the Collected Data
12509 After the tracepoint experiment ends, you use @value{GDBN} commands
12510 for examining the trace data. The basic idea is that each tracepoint
12511 collects a trace @dfn{snapshot} every time it is hit and another
12512 snapshot every time it single-steps. All these snapshots are
12513 consecutively numbered from zero and go into a buffer, and you can
12514 examine them later. The way you examine them is to @dfn{focus} on a
12515 specific trace snapshot. When the remote stub is focused on a trace
12516 snapshot, it will respond to all @value{GDBN} requests for memory and
12517 registers by reading from the buffer which belongs to that snapshot,
12518 rather than from @emph{real} memory or registers of the program being
12519 debugged. This means that @strong{all} @value{GDBN} commands
12520 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
12521 behave as if we were currently debugging the program state as it was
12522 when the tracepoint occurred. Any requests for data that are not in
12523 the buffer will fail.
12526 * tfind:: How to select a trace snapshot
12527 * tdump:: How to display all data for a snapshot
12528 * save tracepoints:: How to save tracepoints for a future run
12532 @subsection @code{tfind @var{n}}
12535 @cindex select trace snapshot
12536 @cindex find trace snapshot
12537 The basic command for selecting a trace snapshot from the buffer is
12538 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
12539 counting from zero. If no argument @var{n} is given, the next
12540 snapshot is selected.
12542 Here are the various forms of using the @code{tfind} command.
12546 Find the first snapshot in the buffer. This is a synonym for
12547 @code{tfind 0} (since 0 is the number of the first snapshot).
12550 Stop debugging trace snapshots, resume @emph{live} debugging.
12553 Same as @samp{tfind none}.
12556 No argument means find the next trace snapshot.
12559 Find the previous trace snapshot before the current one. This permits
12560 retracing earlier steps.
12562 @item tfind tracepoint @var{num}
12563 Find the next snapshot associated with tracepoint @var{num}. Search
12564 proceeds forward from the last examined trace snapshot. If no
12565 argument @var{num} is given, it means find the next snapshot collected
12566 for the same tracepoint as the current snapshot.
12568 @item tfind pc @var{addr}
12569 Find the next snapshot associated with the value @var{addr} of the
12570 program counter. Search proceeds forward from the last examined trace
12571 snapshot. If no argument @var{addr} is given, it means find the next
12572 snapshot with the same value of PC as the current snapshot.
12574 @item tfind outside @var{addr1}, @var{addr2}
12575 Find the next snapshot whose PC is outside the given range of
12576 addresses (exclusive).
12578 @item tfind range @var{addr1}, @var{addr2}
12579 Find the next snapshot whose PC is between @var{addr1} and
12580 @var{addr2} (inclusive).
12582 @item tfind line @r{[}@var{file}:@r{]}@var{n}
12583 Find the next snapshot associated with the source line @var{n}. If
12584 the optional argument @var{file} is given, refer to line @var{n} in
12585 that source file. Search proceeds forward from the last examined
12586 trace snapshot. If no argument @var{n} is given, it means find the
12587 next line other than the one currently being examined; thus saying
12588 @code{tfind line} repeatedly can appear to have the same effect as
12589 stepping from line to line in a @emph{live} debugging session.
12592 The default arguments for the @code{tfind} commands are specifically
12593 designed to make it easy to scan through the trace buffer. For
12594 instance, @code{tfind} with no argument selects the next trace
12595 snapshot, and @code{tfind -} with no argument selects the previous
12596 trace snapshot. So, by giving one @code{tfind} command, and then
12597 simply hitting @key{RET} repeatedly you can examine all the trace
12598 snapshots in order. Or, by saying @code{tfind -} and then hitting
12599 @key{RET} repeatedly you can examine the snapshots in reverse order.
12600 The @code{tfind line} command with no argument selects the snapshot
12601 for the next source line executed. The @code{tfind pc} command with
12602 no argument selects the next snapshot with the same program counter
12603 (PC) as the current frame. The @code{tfind tracepoint} command with
12604 no argument selects the next trace snapshot collected by the same
12605 tracepoint as the current one.
12607 In addition to letting you scan through the trace buffer manually,
12608 these commands make it easy to construct @value{GDBN} scripts that
12609 scan through the trace buffer and print out whatever collected data
12610 you are interested in. Thus, if we want to examine the PC, FP, and SP
12611 registers from each trace frame in the buffer, we can say this:
12614 (@value{GDBP}) @b{tfind start}
12615 (@value{GDBP}) @b{while ($trace_frame != -1)}
12616 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
12617 $trace_frame, $pc, $sp, $fp
12621 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
12622 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
12623 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
12624 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
12625 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
12626 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
12627 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
12628 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
12629 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
12630 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
12631 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
12634 Or, if we want to examine the variable @code{X} at each source line in
12638 (@value{GDBP}) @b{tfind start}
12639 (@value{GDBP}) @b{while ($trace_frame != -1)}
12640 > printf "Frame %d, X == %d\n", $trace_frame, X
12650 @subsection @code{tdump}
12652 @cindex dump all data collected at tracepoint
12653 @cindex tracepoint data, display
12655 This command takes no arguments. It prints all the data collected at
12656 the current trace snapshot.
12659 (@value{GDBP}) @b{trace 444}
12660 (@value{GDBP}) @b{actions}
12661 Enter actions for tracepoint #2, one per line:
12662 > collect $regs, $locals, $args, gdb_long_test
12665 (@value{GDBP}) @b{tstart}
12667 (@value{GDBP}) @b{tfind line 444}
12668 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
12670 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
12672 (@value{GDBP}) @b{tdump}
12673 Data collected at tracepoint 2, trace frame 1:
12674 d0 0xc4aa0085 -995491707
12678 d4 0x71aea3d 119204413
12681 d7 0x380035 3670069
12682 a0 0x19e24a 1696330
12683 a1 0x3000668 50333288
12685 a3 0x322000 3284992
12686 a4 0x3000698 50333336
12687 a5 0x1ad3cc 1758156
12688 fp 0x30bf3c 0x30bf3c
12689 sp 0x30bf34 0x30bf34
12691 pc 0x20b2c8 0x20b2c8
12695 p = 0x20e5b4 "gdb-test"
12702 gdb_long_test = 17 '\021'
12707 @code{tdump} works by scanning the tracepoint's current collection
12708 actions and printing the value of each expression listed. So
12709 @code{tdump} can fail, if after a run, you change the tracepoint's
12710 actions to mention variables that were not collected during the run.
12712 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
12713 uses the collected value of @code{$pc} to distinguish between trace
12714 frames that were collected at the tracepoint hit, and frames that were
12715 collected while stepping. This allows it to correctly choose whether
12716 to display the basic list of collections, or the collections from the
12717 body of the while-stepping loop. However, if @code{$pc} was not collected,
12718 then @code{tdump} will always attempt to dump using the basic collection
12719 list, and may fail if a while-stepping frame does not include all the
12720 same data that is collected at the tracepoint hit.
12721 @c This is getting pretty arcane, example would be good.
12723 @node save tracepoints
12724 @subsection @code{save tracepoints @var{filename}}
12725 @kindex save tracepoints
12726 @kindex save-tracepoints
12727 @cindex save tracepoints for future sessions
12729 This command saves all current tracepoint definitions together with
12730 their actions and passcounts, into a file @file{@var{filename}}
12731 suitable for use in a later debugging session. To read the saved
12732 tracepoint definitions, use the @code{source} command (@pxref{Command
12733 Files}). The @w{@code{save-tracepoints}} command is a deprecated
12734 alias for @w{@code{save tracepoints}}
12736 @node Tracepoint Variables
12737 @section Convenience Variables for Tracepoints
12738 @cindex tracepoint variables
12739 @cindex convenience variables for tracepoints
12742 @vindex $trace_frame
12743 @item (int) $trace_frame
12744 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
12745 snapshot is selected.
12747 @vindex $tracepoint
12748 @item (int) $tracepoint
12749 The tracepoint for the current trace snapshot.
12751 @vindex $trace_line
12752 @item (int) $trace_line
12753 The line number for the current trace snapshot.
12755 @vindex $trace_file
12756 @item (char []) $trace_file
12757 The source file for the current trace snapshot.
12759 @vindex $trace_func
12760 @item (char []) $trace_func
12761 The name of the function containing @code{$tracepoint}.
12764 Note: @code{$trace_file} is not suitable for use in @code{printf},
12765 use @code{output} instead.
12767 Here's a simple example of using these convenience variables for
12768 stepping through all the trace snapshots and printing some of their
12769 data. Note that these are not the same as trace state variables,
12770 which are managed by the target.
12773 (@value{GDBP}) @b{tfind start}
12775 (@value{GDBP}) @b{while $trace_frame != -1}
12776 > output $trace_file
12777 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
12783 @section Using Trace Files
12784 @cindex trace files
12786 In some situations, the target running a trace experiment may no
12787 longer be available; perhaps it crashed, or the hardware was needed
12788 for a different activity. To handle these cases, you can arrange to
12789 dump the trace data into a file, and later use that file as a source
12790 of trace data, via the @code{target tfile} command.
12795 @item tsave [ -r ] @var{filename}
12796 @itemx tsave [-ctf] @var{dirname}
12797 Save the trace data to @var{filename}. By default, this command
12798 assumes that @var{filename} refers to the host filesystem, so if
12799 necessary @value{GDBN} will copy raw trace data up from the target and
12800 then save it. If the target supports it, you can also supply the
12801 optional argument @code{-r} (``remote'') to direct the target to save
12802 the data directly into @var{filename} in its own filesystem, which may be
12803 more efficient if the trace buffer is very large. (Note, however, that
12804 @code{target tfile} can only read from files accessible to the host.)
12805 By default, this command will save trace frame in tfile format.
12806 You can supply the optional argument @code{-ctf} to save date in CTF
12807 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
12808 that can be shared by multiple debugging and tracing tools. Please go to
12809 @indicateurl{http://www.efficios.com/ctf} to get more information.
12811 @kindex target tfile
12815 @item target tfile @var{filename}
12816 @itemx target ctf @var{dirname}
12817 Use the file named @var{filename} or directory named @var{dirname} as
12818 a source of trace data. Commands that examine data work as they do with
12819 a live target, but it is not possible to run any new trace experiments.
12820 @code{tstatus} will report the state of the trace run at the moment
12821 the data was saved, as well as the current trace frame you are examining.
12822 @var{filename} or @var{dirname} must be on a filesystem accessible to
12826 (@value{GDBP}) target ctf ctf.ctf
12827 (@value{GDBP}) tfind
12828 Found trace frame 0, tracepoint 2
12829 39 ++a; /* set tracepoint 1 here */
12830 (@value{GDBP}) tdump
12831 Data collected at tracepoint 2, trace frame 0:
12835 c = @{"123", "456", "789", "123", "456", "789"@}
12836 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
12844 @chapter Debugging Programs That Use Overlays
12847 If your program is too large to fit completely in your target system's
12848 memory, you can sometimes use @dfn{overlays} to work around this
12849 problem. @value{GDBN} provides some support for debugging programs that
12853 * How Overlays Work:: A general explanation of overlays.
12854 * Overlay Commands:: Managing overlays in @value{GDBN}.
12855 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
12856 mapped by asking the inferior.
12857 * Overlay Sample Program:: A sample program using overlays.
12860 @node How Overlays Work
12861 @section How Overlays Work
12862 @cindex mapped overlays
12863 @cindex unmapped overlays
12864 @cindex load address, overlay's
12865 @cindex mapped address
12866 @cindex overlay area
12868 Suppose you have a computer whose instruction address space is only 64
12869 kilobytes long, but which has much more memory which can be accessed by
12870 other means: special instructions, segment registers, or memory
12871 management hardware, for example. Suppose further that you want to
12872 adapt a program which is larger than 64 kilobytes to run on this system.
12874 One solution is to identify modules of your program which are relatively
12875 independent, and need not call each other directly; call these modules
12876 @dfn{overlays}. Separate the overlays from the main program, and place
12877 their machine code in the larger memory. Place your main program in
12878 instruction memory, but leave at least enough space there to hold the
12879 largest overlay as well.
12881 Now, to call a function located in an overlay, you must first copy that
12882 overlay's machine code from the large memory into the space set aside
12883 for it in the instruction memory, and then jump to its entry point
12886 @c NB: In the below the mapped area's size is greater or equal to the
12887 @c size of all overlays. This is intentional to remind the developer
12888 @c that overlays don't necessarily need to be the same size.
12892 Data Instruction Larger
12893 Address Space Address Space Address Space
12894 +-----------+ +-----------+ +-----------+
12896 +-----------+ +-----------+ +-----------+<-- overlay 1
12897 | program | | main | .----| overlay 1 | load address
12898 | variables | | program | | +-----------+
12899 | and heap | | | | | |
12900 +-----------+ | | | +-----------+<-- overlay 2
12901 | | +-----------+ | | | load address
12902 +-----------+ | | | .-| overlay 2 |
12904 mapped --->+-----------+ | | +-----------+
12905 address | | | | | |
12906 | overlay | <-' | | |
12907 | area | <---' +-----------+<-- overlay 3
12908 | | <---. | | load address
12909 +-----------+ `--| overlay 3 |
12916 @anchor{A code overlay}A code overlay
12920 The diagram (@pxref{A code overlay}) shows a system with separate data
12921 and instruction address spaces. To map an overlay, the program copies
12922 its code from the larger address space to the instruction address space.
12923 Since the overlays shown here all use the same mapped address, only one
12924 may be mapped at a time. For a system with a single address space for
12925 data and instructions, the diagram would be similar, except that the
12926 program variables and heap would share an address space with the main
12927 program and the overlay area.
12929 An overlay loaded into instruction memory and ready for use is called a
12930 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
12931 instruction memory. An overlay not present (or only partially present)
12932 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
12933 is its address in the larger memory. The mapped address is also called
12934 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
12935 called the @dfn{load memory address}, or @dfn{LMA}.
12937 Unfortunately, overlays are not a completely transparent way to adapt a
12938 program to limited instruction memory. They introduce a new set of
12939 global constraints you must keep in mind as you design your program:
12944 Before calling or returning to a function in an overlay, your program
12945 must make sure that overlay is actually mapped. Otherwise, the call or
12946 return will transfer control to the right address, but in the wrong
12947 overlay, and your program will probably crash.
12950 If the process of mapping an overlay is expensive on your system, you
12951 will need to choose your overlays carefully to minimize their effect on
12952 your program's performance.
12955 The executable file you load onto your system must contain each
12956 overlay's instructions, appearing at the overlay's load address, not its
12957 mapped address. However, each overlay's instructions must be relocated
12958 and its symbols defined as if the overlay were at its mapped address.
12959 You can use GNU linker scripts to specify different load and relocation
12960 addresses for pieces of your program; see @ref{Overlay Description,,,
12961 ld.info, Using ld: the GNU linker}.
12964 The procedure for loading executable files onto your system must be able
12965 to load their contents into the larger address space as well as the
12966 instruction and data spaces.
12970 The overlay system described above is rather simple, and could be
12971 improved in many ways:
12976 If your system has suitable bank switch registers or memory management
12977 hardware, you could use those facilities to make an overlay's load area
12978 contents simply appear at their mapped address in instruction space.
12979 This would probably be faster than copying the overlay to its mapped
12980 area in the usual way.
12983 If your overlays are small enough, you could set aside more than one
12984 overlay area, and have more than one overlay mapped at a time.
12987 You can use overlays to manage data, as well as instructions. In
12988 general, data overlays are even less transparent to your design than
12989 code overlays: whereas code overlays only require care when you call or
12990 return to functions, data overlays require care every time you access
12991 the data. Also, if you change the contents of a data overlay, you
12992 must copy its contents back out to its load address before you can copy a
12993 different data overlay into the same mapped area.
12998 @node Overlay Commands
12999 @section Overlay Commands
13001 To use @value{GDBN}'s overlay support, each overlay in your program must
13002 correspond to a separate section of the executable file. The section's
13003 virtual memory address and load memory address must be the overlay's
13004 mapped and load addresses. Identifying overlays with sections allows
13005 @value{GDBN} to determine the appropriate address of a function or
13006 variable, depending on whether the overlay is mapped or not.
13008 @value{GDBN}'s overlay commands all start with the word @code{overlay};
13009 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
13014 Disable @value{GDBN}'s overlay support. When overlay support is
13015 disabled, @value{GDBN} assumes that all functions and variables are
13016 always present at their mapped addresses. By default, @value{GDBN}'s
13017 overlay support is disabled.
13019 @item overlay manual
13020 @cindex manual overlay debugging
13021 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
13022 relies on you to tell it which overlays are mapped, and which are not,
13023 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
13024 commands described below.
13026 @item overlay map-overlay @var{overlay}
13027 @itemx overlay map @var{overlay}
13028 @cindex map an overlay
13029 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
13030 be the name of the object file section containing the overlay. When an
13031 overlay is mapped, @value{GDBN} assumes it can find the overlay's
13032 functions and variables at their mapped addresses. @value{GDBN} assumes
13033 that any other overlays whose mapped ranges overlap that of
13034 @var{overlay} are now unmapped.
13036 @item overlay unmap-overlay @var{overlay}
13037 @itemx overlay unmap @var{overlay}
13038 @cindex unmap an overlay
13039 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
13040 must be the name of the object file section containing the overlay.
13041 When an overlay is unmapped, @value{GDBN} assumes it can find the
13042 overlay's functions and variables at their load addresses.
13045 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
13046 consults a data structure the overlay manager maintains in the inferior
13047 to see which overlays are mapped. For details, see @ref{Automatic
13048 Overlay Debugging}.
13050 @item overlay load-target
13051 @itemx overlay load
13052 @cindex reloading the overlay table
13053 Re-read the overlay table from the inferior. Normally, @value{GDBN}
13054 re-reads the table @value{GDBN} automatically each time the inferior
13055 stops, so this command should only be necessary if you have changed the
13056 overlay mapping yourself using @value{GDBN}. This command is only
13057 useful when using automatic overlay debugging.
13059 @item overlay list-overlays
13060 @itemx overlay list
13061 @cindex listing mapped overlays
13062 Display a list of the overlays currently mapped, along with their mapped
13063 addresses, load addresses, and sizes.
13067 Normally, when @value{GDBN} prints a code address, it includes the name
13068 of the function the address falls in:
13071 (@value{GDBP}) print main
13072 $3 = @{int ()@} 0x11a0 <main>
13075 When overlay debugging is enabled, @value{GDBN} recognizes code in
13076 unmapped overlays, and prints the names of unmapped functions with
13077 asterisks around them. For example, if @code{foo} is a function in an
13078 unmapped overlay, @value{GDBN} prints it this way:
13081 (@value{GDBP}) overlay list
13082 No sections are mapped.
13083 (@value{GDBP}) print foo
13084 $5 = @{int (int)@} 0x100000 <*foo*>
13087 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
13091 (@value{GDBP}) overlay list
13092 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
13093 mapped at 0x1016 - 0x104a
13094 (@value{GDBP}) print foo
13095 $6 = @{int (int)@} 0x1016 <foo>
13098 When overlay debugging is enabled, @value{GDBN} can find the correct
13099 address for functions and variables in an overlay, whether or not the
13100 overlay is mapped. This allows most @value{GDBN} commands, like
13101 @code{break} and @code{disassemble}, to work normally, even on unmapped
13102 code. However, @value{GDBN}'s breakpoint support has some limitations:
13106 @cindex breakpoints in overlays
13107 @cindex overlays, setting breakpoints in
13108 You can set breakpoints in functions in unmapped overlays, as long as
13109 @value{GDBN} can write to the overlay at its load address.
13111 @value{GDBN} can not set hardware or simulator-based breakpoints in
13112 unmapped overlays. However, if you set a breakpoint at the end of your
13113 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
13114 you are using manual overlay management), @value{GDBN} will re-set its
13115 breakpoints properly.
13119 @node Automatic Overlay Debugging
13120 @section Automatic Overlay Debugging
13121 @cindex automatic overlay debugging
13123 @value{GDBN} can automatically track which overlays are mapped and which
13124 are not, given some simple co-operation from the overlay manager in the
13125 inferior. If you enable automatic overlay debugging with the
13126 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
13127 looks in the inferior's memory for certain variables describing the
13128 current state of the overlays.
13130 Here are the variables your overlay manager must define to support
13131 @value{GDBN}'s automatic overlay debugging:
13135 @item @code{_ovly_table}:
13136 This variable must be an array of the following structures:
13141 /* The overlay's mapped address. */
13144 /* The size of the overlay, in bytes. */
13145 unsigned long size;
13147 /* The overlay's load address. */
13150 /* Non-zero if the overlay is currently mapped;
13152 unsigned long mapped;
13156 @item @code{_novlys}:
13157 This variable must be a four-byte signed integer, holding the total
13158 number of elements in @code{_ovly_table}.
13162 To decide whether a particular overlay is mapped or not, @value{GDBN}
13163 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
13164 @code{lma} members equal the VMA and LMA of the overlay's section in the
13165 executable file. When @value{GDBN} finds a matching entry, it consults
13166 the entry's @code{mapped} member to determine whether the overlay is
13169 In addition, your overlay manager may define a function called
13170 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
13171 will silently set a breakpoint there. If the overlay manager then
13172 calls this function whenever it has changed the overlay table, this
13173 will enable @value{GDBN} to accurately keep track of which overlays
13174 are in program memory, and update any breakpoints that may be set
13175 in overlays. This will allow breakpoints to work even if the
13176 overlays are kept in ROM or other non-writable memory while they
13177 are not being executed.
13179 @node Overlay Sample Program
13180 @section Overlay Sample Program
13181 @cindex overlay example program
13183 When linking a program which uses overlays, you must place the overlays
13184 at their load addresses, while relocating them to run at their mapped
13185 addresses. To do this, you must write a linker script (@pxref{Overlay
13186 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
13187 since linker scripts are specific to a particular host system, target
13188 architecture, and target memory layout, this manual cannot provide
13189 portable sample code demonstrating @value{GDBN}'s overlay support.
13191 However, the @value{GDBN} source distribution does contain an overlaid
13192 program, with linker scripts for a few systems, as part of its test
13193 suite. The program consists of the following files from
13194 @file{gdb/testsuite/gdb.base}:
13198 The main program file.
13200 A simple overlay manager, used by @file{overlays.c}.
13205 Overlay modules, loaded and used by @file{overlays.c}.
13208 Linker scripts for linking the test program on the @code{d10v-elf}
13209 and @code{m32r-elf} targets.
13212 You can build the test program using the @code{d10v-elf} GCC
13213 cross-compiler like this:
13216 $ d10v-elf-gcc -g -c overlays.c
13217 $ d10v-elf-gcc -g -c ovlymgr.c
13218 $ d10v-elf-gcc -g -c foo.c
13219 $ d10v-elf-gcc -g -c bar.c
13220 $ d10v-elf-gcc -g -c baz.c
13221 $ d10v-elf-gcc -g -c grbx.c
13222 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
13223 baz.o grbx.o -Wl,-Td10v.ld -o overlays
13226 The build process is identical for any other architecture, except that
13227 you must substitute the appropriate compiler and linker script for the
13228 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
13232 @chapter Using @value{GDBN} with Different Languages
13235 Although programming languages generally have common aspects, they are
13236 rarely expressed in the same manner. For instance, in ANSI C,
13237 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
13238 Modula-2, it is accomplished by @code{p^}. Values can also be
13239 represented (and displayed) differently. Hex numbers in C appear as
13240 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
13242 @cindex working language
13243 Language-specific information is built into @value{GDBN} for some languages,
13244 allowing you to express operations like the above in your program's
13245 native language, and allowing @value{GDBN} to output values in a manner
13246 consistent with the syntax of your program's native language. The
13247 language you use to build expressions is called the @dfn{working
13251 * Setting:: Switching between source languages
13252 * Show:: Displaying the language
13253 * Checks:: Type and range checks
13254 * Supported Languages:: Supported languages
13255 * Unsupported Languages:: Unsupported languages
13259 @section Switching Between Source Languages
13261 There are two ways to control the working language---either have @value{GDBN}
13262 set it automatically, or select it manually yourself. You can use the
13263 @code{set language} command for either purpose. On startup, @value{GDBN}
13264 defaults to setting the language automatically. The working language is
13265 used to determine how expressions you type are interpreted, how values
13268 In addition to the working language, every source file that
13269 @value{GDBN} knows about has its own working language. For some object
13270 file formats, the compiler might indicate which language a particular
13271 source file is in. However, most of the time @value{GDBN} infers the
13272 language from the name of the file. The language of a source file
13273 controls whether C@t{++} names are demangled---this way @code{backtrace} can
13274 show each frame appropriately for its own language. There is no way to
13275 set the language of a source file from within @value{GDBN}, but you can
13276 set the language associated with a filename extension. @xref{Show, ,
13277 Displaying the Language}.
13279 This is most commonly a problem when you use a program, such
13280 as @code{cfront} or @code{f2c}, that generates C but is written in
13281 another language. In that case, make the
13282 program use @code{#line} directives in its C output; that way
13283 @value{GDBN} will know the correct language of the source code of the original
13284 program, and will display that source code, not the generated C code.
13287 * Filenames:: Filename extensions and languages.
13288 * Manually:: Setting the working language manually
13289 * Automatically:: Having @value{GDBN} infer the source language
13293 @subsection List of Filename Extensions and Languages
13295 If a source file name ends in one of the following extensions, then
13296 @value{GDBN} infers that its language is the one indicated.
13314 C@t{++} source file
13320 Objective-C source file
13324 Fortran source file
13327 Modula-2 source file
13331 Assembler source file. This actually behaves almost like C, but
13332 @value{GDBN} does not skip over function prologues when stepping.
13335 In addition, you may set the language associated with a filename
13336 extension. @xref{Show, , Displaying the Language}.
13339 @subsection Setting the Working Language
13341 If you allow @value{GDBN} to set the language automatically,
13342 expressions are interpreted the same way in your debugging session and
13345 @kindex set language
13346 If you wish, you may set the language manually. To do this, issue the
13347 command @samp{set language @var{lang}}, where @var{lang} is the name of
13348 a language, such as
13349 @code{c} or @code{modula-2}.
13350 For a list of the supported languages, type @samp{set language}.
13352 Setting the language manually prevents @value{GDBN} from updating the working
13353 language automatically. This can lead to confusion if you try
13354 to debug a program when the working language is not the same as the
13355 source language, when an expression is acceptable to both
13356 languages---but means different things. For instance, if the current
13357 source file were written in C, and @value{GDBN} was parsing Modula-2, a
13365 might not have the effect you intended. In C, this means to add
13366 @code{b} and @code{c} and place the result in @code{a}. The result
13367 printed would be the value of @code{a}. In Modula-2, this means to compare
13368 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
13370 @node Automatically
13371 @subsection Having @value{GDBN} Infer the Source Language
13373 To have @value{GDBN} set the working language automatically, use
13374 @samp{set language local} or @samp{set language auto}. @value{GDBN}
13375 then infers the working language. That is, when your program stops in a
13376 frame (usually by encountering a breakpoint), @value{GDBN} sets the
13377 working language to the language recorded for the function in that
13378 frame. If the language for a frame is unknown (that is, if the function
13379 or block corresponding to the frame was defined in a source file that
13380 does not have a recognized extension), the current working language is
13381 not changed, and @value{GDBN} issues a warning.
13383 This may not seem necessary for most programs, which are written
13384 entirely in one source language. However, program modules and libraries
13385 written in one source language can be used by a main program written in
13386 a different source language. Using @samp{set language auto} in this
13387 case frees you from having to set the working language manually.
13390 @section Displaying the Language
13392 The following commands help you find out which language is the
13393 working language, and also what language source files were written in.
13396 @item show language
13397 @anchor{show language}
13398 @kindex show language
13399 Display the current working language. This is the
13400 language you can use with commands such as @code{print} to
13401 build and compute expressions that may involve variables in your program.
13404 @kindex info frame@r{, show the source language}
13405 Display the source language for this frame. This language becomes the
13406 working language if you use an identifier from this frame.
13407 @xref{Frame Info, ,Information about a Frame}, to identify the other
13408 information listed here.
13411 @kindex info source@r{, show the source language}
13412 Display the source language of this source file.
13413 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
13414 information listed here.
13417 In unusual circumstances, you may have source files with extensions
13418 not in the standard list. You can then set the extension associated
13419 with a language explicitly:
13422 @item set extension-language @var{ext} @var{language}
13423 @kindex set extension-language
13424 Tell @value{GDBN} that source files with extension @var{ext} are to be
13425 assumed as written in the source language @var{language}.
13427 @item info extensions
13428 @kindex info extensions
13429 List all the filename extensions and the associated languages.
13433 @section Type and Range Checking
13435 Some languages are designed to guard you against making seemingly common
13436 errors through a series of compile- and run-time checks. These include
13437 checking the type of arguments to functions and operators and making
13438 sure mathematical overflows are caught at run time. Checks such as
13439 these help to ensure a program's correctness once it has been compiled
13440 by eliminating type mismatches and providing active checks for range
13441 errors when your program is running.
13443 By default @value{GDBN} checks for these errors according to the
13444 rules of the current source language. Although @value{GDBN} does not check
13445 the statements in your program, it can check expressions entered directly
13446 into @value{GDBN} for evaluation via the @code{print} command, for example.
13449 * Type Checking:: An overview of type checking
13450 * Range Checking:: An overview of range checking
13453 @cindex type checking
13454 @cindex checks, type
13455 @node Type Checking
13456 @subsection An Overview of Type Checking
13458 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
13459 arguments to operators and functions have to be of the correct type,
13460 otherwise an error occurs. These checks prevent type mismatch
13461 errors from ever causing any run-time problems. For example,
13464 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
13466 (@value{GDBP}) print obj.my_method (0)
13469 (@value{GDBP}) print obj.my_method (0x1234)
13470 Cannot resolve method klass::my_method to any overloaded instance
13473 The second example fails because in C@t{++} the integer constant
13474 @samp{0x1234} is not type-compatible with the pointer parameter type.
13476 For the expressions you use in @value{GDBN} commands, you can tell
13477 @value{GDBN} to not enforce strict type checking or
13478 to treat any mismatches as errors and abandon the expression;
13479 When type checking is disabled, @value{GDBN} successfully evaluates
13480 expressions like the second example above.
13482 Even if type checking is off, there may be other reasons
13483 related to type that prevent @value{GDBN} from evaluating an expression.
13484 For instance, @value{GDBN} does not know how to add an @code{int} and
13485 a @code{struct foo}. These particular type errors have nothing to do
13486 with the language in use and usually arise from expressions which make
13487 little sense to evaluate anyway.
13489 @value{GDBN} provides some additional commands for controlling type checking:
13491 @kindex set check type
13492 @kindex show check type
13494 @item set check type on
13495 @itemx set check type off
13496 Set strict type checking on or off. If any type mismatches occur in
13497 evaluating an expression while type checking is on, @value{GDBN} prints a
13498 message and aborts evaluation of the expression.
13500 @item show check type
13501 Show the current setting of type checking and whether @value{GDBN}
13502 is enforcing strict type checking rules.
13505 @cindex range checking
13506 @cindex checks, range
13507 @node Range Checking
13508 @subsection An Overview of Range Checking
13510 In some languages (such as Modula-2), it is an error to exceed the
13511 bounds of a type; this is enforced with run-time checks. Such range
13512 checking is meant to ensure program correctness by making sure
13513 computations do not overflow, or indices on an array element access do
13514 not exceed the bounds of the array.
13516 For expressions you use in @value{GDBN} commands, you can tell
13517 @value{GDBN} to treat range errors in one of three ways: ignore them,
13518 always treat them as errors and abandon the expression, or issue
13519 warnings but evaluate the expression anyway.
13521 A range error can result from numerical overflow, from exceeding an
13522 array index bound, or when you type a constant that is not a member
13523 of any type. Some languages, however, do not treat overflows as an
13524 error. In many implementations of C, mathematical overflow causes the
13525 result to ``wrap around'' to lower values---for example, if @var{m} is
13526 the largest integer value, and @var{s} is the smallest, then
13529 @var{m} + 1 @result{} @var{s}
13532 This, too, is specific to individual languages, and in some cases
13533 specific to individual compilers or machines. @xref{Supported Languages, ,
13534 Supported Languages}, for further details on specific languages.
13536 @value{GDBN} provides some additional commands for controlling the range checker:
13538 @kindex set check range
13539 @kindex show check range
13541 @item set check range auto
13542 Set range checking on or off based on the current working language.
13543 @xref{Supported Languages, ,Supported Languages}, for the default settings for
13546 @item set check range on
13547 @itemx set check range off
13548 Set range checking on or off, overriding the default setting for the
13549 current working language. A warning is issued if the setting does not
13550 match the language default. If a range error occurs and range checking is on,
13551 then a message is printed and evaluation of the expression is aborted.
13553 @item set check range warn
13554 Output messages when the @value{GDBN} range checker detects a range error,
13555 but attempt to evaluate the expression anyway. Evaluating the
13556 expression may still be impossible for other reasons, such as accessing
13557 memory that the process does not own (a typical example from many Unix
13561 Show the current setting of the range checker, and whether or not it is
13562 being set automatically by @value{GDBN}.
13565 @node Supported Languages
13566 @section Supported Languages
13568 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
13569 OpenCL C, Pascal, assembly, Modula-2, and Ada.
13570 @c This is false ...
13571 Some @value{GDBN} features may be used in expressions regardless of the
13572 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
13573 and the @samp{@{type@}addr} construct (@pxref{Expressions,
13574 ,Expressions}) can be used with the constructs of any supported
13577 The following sections detail to what degree each source language is
13578 supported by @value{GDBN}. These sections are not meant to be language
13579 tutorials or references, but serve only as a reference guide to what the
13580 @value{GDBN} expression parser accepts, and what input and output
13581 formats should look like for different languages. There are many good
13582 books written on each of these languages; please look to these for a
13583 language reference or tutorial.
13586 * C:: C and C@t{++}
13589 * Objective-C:: Objective-C
13590 * OpenCL C:: OpenCL C
13591 * Fortran:: Fortran
13593 * Modula-2:: Modula-2
13598 @subsection C and C@t{++}
13600 @cindex C and C@t{++}
13601 @cindex expressions in C or C@t{++}
13603 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
13604 to both languages. Whenever this is the case, we discuss those languages
13608 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
13609 @cindex @sc{gnu} C@t{++}
13610 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
13611 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
13612 effectively, you must compile your C@t{++} programs with a supported
13613 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
13614 compiler (@code{aCC}).
13617 * C Operators:: C and C@t{++} operators
13618 * C Constants:: C and C@t{++} constants
13619 * C Plus Plus Expressions:: C@t{++} expressions
13620 * C Defaults:: Default settings for C and C@t{++}
13621 * C Checks:: C and C@t{++} type and range checks
13622 * Debugging C:: @value{GDBN} and C
13623 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
13624 * Decimal Floating Point:: Numbers in Decimal Floating Point format
13628 @subsubsection C and C@t{++} Operators
13630 @cindex C and C@t{++} operators
13632 Operators must be defined on values of specific types. For instance,
13633 @code{+} is defined on numbers, but not on structures. Operators are
13634 often defined on groups of types.
13636 For the purposes of C and C@t{++}, the following definitions hold:
13641 @emph{Integral types} include @code{int} with any of its storage-class
13642 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
13645 @emph{Floating-point types} include @code{float}, @code{double}, and
13646 @code{long double} (if supported by the target platform).
13649 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
13652 @emph{Scalar types} include all of the above.
13657 The following operators are supported. They are listed here
13658 in order of increasing precedence:
13662 The comma or sequencing operator. Expressions in a comma-separated list
13663 are evaluated from left to right, with the result of the entire
13664 expression being the last expression evaluated.
13667 Assignment. The value of an assignment expression is the value
13668 assigned. Defined on scalar types.
13671 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
13672 and translated to @w{@code{@var{a} = @var{a op b}}}.
13673 @w{@code{@var{op}=}} and @code{=} have the same precedence.
13674 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
13675 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
13678 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
13679 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
13683 Logical @sc{or}. Defined on integral types.
13686 Logical @sc{and}. Defined on integral types.
13689 Bitwise @sc{or}. Defined on integral types.
13692 Bitwise exclusive-@sc{or}. Defined on integral types.
13695 Bitwise @sc{and}. Defined on integral types.
13698 Equality and inequality. Defined on scalar types. The value of these
13699 expressions is 0 for false and non-zero for true.
13701 @item <@r{, }>@r{, }<=@r{, }>=
13702 Less than, greater than, less than or equal, greater than or equal.
13703 Defined on scalar types. The value of these expressions is 0 for false
13704 and non-zero for true.
13707 left shift, and right shift. Defined on integral types.
13710 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13713 Addition and subtraction. Defined on integral types, floating-point types and
13716 @item *@r{, }/@r{, }%
13717 Multiplication, division, and modulus. Multiplication and division are
13718 defined on integral and floating-point types. Modulus is defined on
13722 Increment and decrement. When appearing before a variable, the
13723 operation is performed before the variable is used in an expression;
13724 when appearing after it, the variable's value is used before the
13725 operation takes place.
13728 Pointer dereferencing. Defined on pointer types. Same precedence as
13732 Address operator. Defined on variables. Same precedence as @code{++}.
13734 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
13735 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
13736 to examine the address
13737 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
13741 Negative. Defined on integral and floating-point types. Same
13742 precedence as @code{++}.
13745 Logical negation. Defined on integral types. Same precedence as
13749 Bitwise complement operator. Defined on integral types. Same precedence as
13754 Structure member, and pointer-to-structure member. For convenience,
13755 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
13756 pointer based on the stored type information.
13757 Defined on @code{struct} and @code{union} data.
13760 Dereferences of pointers to members.
13763 Array indexing. @code{@var{a}[@var{i}]} is defined as
13764 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
13767 Function parameter list. Same precedence as @code{->}.
13770 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
13771 and @code{class} types.
13774 Doubled colons also represent the @value{GDBN} scope operator
13775 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
13779 If an operator is redefined in the user code, @value{GDBN} usually
13780 attempts to invoke the redefined version instead of using the operator's
13781 predefined meaning.
13784 @subsubsection C and C@t{++} Constants
13786 @cindex C and C@t{++} constants
13788 @value{GDBN} allows you to express the constants of C and C@t{++} in the
13793 Integer constants are a sequence of digits. Octal constants are
13794 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
13795 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
13796 @samp{l}, specifying that the constant should be treated as a
13800 Floating point constants are a sequence of digits, followed by a decimal
13801 point, followed by a sequence of digits, and optionally followed by an
13802 exponent. An exponent is of the form:
13803 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
13804 sequence of digits. The @samp{+} is optional for positive exponents.
13805 A floating-point constant may also end with a letter @samp{f} or
13806 @samp{F}, specifying that the constant should be treated as being of
13807 the @code{float} (as opposed to the default @code{double}) type; or with
13808 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
13812 Enumerated constants consist of enumerated identifiers, or their
13813 integral equivalents.
13816 Character constants are a single character surrounded by single quotes
13817 (@code{'}), or a number---the ordinal value of the corresponding character
13818 (usually its @sc{ascii} value). Within quotes, the single character may
13819 be represented by a letter or by @dfn{escape sequences}, which are of
13820 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
13821 of the character's ordinal value; or of the form @samp{\@var{x}}, where
13822 @samp{@var{x}} is a predefined special character---for example,
13823 @samp{\n} for newline.
13825 Wide character constants can be written by prefixing a character
13826 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
13827 form of @samp{x}. The target wide character set is used when
13828 computing the value of this constant (@pxref{Character Sets}).
13831 String constants are a sequence of character constants surrounded by
13832 double quotes (@code{"}). Any valid character constant (as described
13833 above) may appear. Double quotes within the string must be preceded by
13834 a backslash, so for instance @samp{"a\"b'c"} is a string of five
13837 Wide string constants can be written by prefixing a string constant
13838 with @samp{L}, as in C. The target wide character set is used when
13839 computing the value of this constant (@pxref{Character Sets}).
13842 Pointer constants are an integral value. You can also write pointers
13843 to constants using the C operator @samp{&}.
13846 Array constants are comma-separated lists surrounded by braces @samp{@{}
13847 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
13848 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
13849 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
13852 @node C Plus Plus Expressions
13853 @subsubsection C@t{++} Expressions
13855 @cindex expressions in C@t{++}
13856 @value{GDBN} expression handling can interpret most C@t{++} expressions.
13858 @cindex debugging C@t{++} programs
13859 @cindex C@t{++} compilers
13860 @cindex debug formats and C@t{++}
13861 @cindex @value{NGCC} and C@t{++}
13863 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
13864 the proper compiler and the proper debug format. Currently,
13865 @value{GDBN} works best when debugging C@t{++} code that is compiled
13866 with the most recent version of @value{NGCC} possible. The DWARF
13867 debugging format is preferred; @value{NGCC} defaults to this on most
13868 popular platforms. Other compilers and/or debug formats are likely to
13869 work badly or not at all when using @value{GDBN} to debug C@t{++}
13870 code. @xref{Compilation}.
13875 @cindex member functions
13877 Member function calls are allowed; you can use expressions like
13880 count = aml->GetOriginal(x, y)
13883 @vindex this@r{, inside C@t{++} member functions}
13884 @cindex namespace in C@t{++}
13886 While a member function is active (in the selected stack frame), your
13887 expressions have the same namespace available as the member function;
13888 that is, @value{GDBN} allows implicit references to the class instance
13889 pointer @code{this} following the same rules as C@t{++}. @code{using}
13890 declarations in the current scope are also respected by @value{GDBN}.
13892 @cindex call overloaded functions
13893 @cindex overloaded functions, calling
13894 @cindex type conversions in C@t{++}
13896 You can call overloaded functions; @value{GDBN} resolves the function
13897 call to the right definition, with some restrictions. @value{GDBN} does not
13898 perform overload resolution involving user-defined type conversions,
13899 calls to constructors, or instantiations of templates that do not exist
13900 in the program. It also cannot handle ellipsis argument lists or
13903 It does perform integral conversions and promotions, floating-point
13904 promotions, arithmetic conversions, pointer conversions, conversions of
13905 class objects to base classes, and standard conversions such as those of
13906 functions or arrays to pointers; it requires an exact match on the
13907 number of function arguments.
13909 Overload resolution is always performed, unless you have specified
13910 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
13911 ,@value{GDBN} Features for C@t{++}}.
13913 You must specify @code{set overload-resolution off} in order to use an
13914 explicit function signature to call an overloaded function, as in
13916 p 'foo(char,int)'('x', 13)
13919 The @value{GDBN} command-completion facility can simplify this;
13920 see @ref{Completion, ,Command Completion}.
13922 @cindex reference declarations
13924 @value{GDBN} understands variables declared as C@t{++} references; you can use
13925 them in expressions just as you do in C@t{++} source---they are automatically
13928 In the parameter list shown when @value{GDBN} displays a frame, the values of
13929 reference variables are not displayed (unlike other variables); this
13930 avoids clutter, since references are often used for large structures.
13931 The @emph{address} of a reference variable is always shown, unless
13932 you have specified @samp{set print address off}.
13935 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
13936 expressions can use it just as expressions in your program do. Since
13937 one scope may be defined in another, you can use @code{::} repeatedly if
13938 necessary, for example in an expression like
13939 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
13940 resolving name scope by reference to source files, in both C and C@t{++}
13941 debugging (@pxref{Variables, ,Program Variables}).
13944 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
13949 @subsubsection C and C@t{++} Defaults
13951 @cindex C and C@t{++} defaults
13953 If you allow @value{GDBN} to set range checking automatically, it
13954 defaults to @code{off} whenever the working language changes to
13955 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
13956 selects the working language.
13958 If you allow @value{GDBN} to set the language automatically, it
13959 recognizes source files whose names end with @file{.c}, @file{.C}, or
13960 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
13961 these files, it sets the working language to C or C@t{++}.
13962 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
13963 for further details.
13966 @subsubsection C and C@t{++} Type and Range Checks
13968 @cindex C and C@t{++} checks
13970 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
13971 checking is used. However, if you turn type checking off, @value{GDBN}
13972 will allow certain non-standard conversions, such as promoting integer
13973 constants to pointers.
13975 Range checking, if turned on, is done on mathematical operations. Array
13976 indices are not checked, since they are often used to index a pointer
13977 that is not itself an array.
13980 @subsubsection @value{GDBN} and C
13982 The @code{set print union} and @code{show print union} commands apply to
13983 the @code{union} type. When set to @samp{on}, any @code{union} that is
13984 inside a @code{struct} or @code{class} is also printed. Otherwise, it
13985 appears as @samp{@{...@}}.
13987 The @code{@@} operator aids in the debugging of dynamic arrays, formed
13988 with pointers and a memory allocation function. @xref{Expressions,
13991 @node Debugging C Plus Plus
13992 @subsubsection @value{GDBN} Features for C@t{++}
13994 @cindex commands for C@t{++}
13996 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
13997 designed specifically for use with C@t{++}. Here is a summary:
14000 @cindex break in overloaded functions
14001 @item @r{breakpoint menus}
14002 When you want a breakpoint in a function whose name is overloaded,
14003 @value{GDBN} has the capability to display a menu of possible breakpoint
14004 locations to help you specify which function definition you want.
14005 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
14007 @cindex overloading in C@t{++}
14008 @item rbreak @var{regex}
14009 Setting breakpoints using regular expressions is helpful for setting
14010 breakpoints on overloaded functions that are not members of any special
14012 @xref{Set Breaks, ,Setting Breakpoints}.
14014 @cindex C@t{++} exception handling
14016 @itemx catch rethrow
14018 Debug C@t{++} exception handling using these commands. @xref{Set
14019 Catchpoints, , Setting Catchpoints}.
14021 @cindex inheritance
14022 @item ptype @var{typename}
14023 Print inheritance relationships as well as other information for type
14025 @xref{Symbols, ,Examining the Symbol Table}.
14027 @item info vtbl @var{expression}.
14028 The @code{info vtbl} command can be used to display the virtual
14029 method tables of the object computed by @var{expression}. This shows
14030 one entry per virtual table; there may be multiple virtual tables when
14031 multiple inheritance is in use.
14033 @cindex C@t{++} symbol display
14034 @item set print demangle
14035 @itemx show print demangle
14036 @itemx set print asm-demangle
14037 @itemx show print asm-demangle
14038 Control whether C@t{++} symbols display in their source form, both when
14039 displaying code as C@t{++} source and when displaying disassemblies.
14040 @xref{Print Settings, ,Print Settings}.
14042 @item set print object
14043 @itemx show print object
14044 Choose whether to print derived (actual) or declared types of objects.
14045 @xref{Print Settings, ,Print Settings}.
14047 @item set print vtbl
14048 @itemx show print vtbl
14049 Control the format for printing virtual function tables.
14050 @xref{Print Settings, ,Print Settings}.
14051 (The @code{vtbl} commands do not work on programs compiled with the HP
14052 ANSI C@t{++} compiler (@code{aCC}).)
14054 @kindex set overload-resolution
14055 @cindex overloaded functions, overload resolution
14056 @item set overload-resolution on
14057 Enable overload resolution for C@t{++} expression evaluation. The default
14058 is on. For overloaded functions, @value{GDBN} evaluates the arguments
14059 and searches for a function whose signature matches the argument types,
14060 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
14061 Expressions, ,C@t{++} Expressions}, for details).
14062 If it cannot find a match, it emits a message.
14064 @item set overload-resolution off
14065 Disable overload resolution for C@t{++} expression evaluation. For
14066 overloaded functions that are not class member functions, @value{GDBN}
14067 chooses the first function of the specified name that it finds in the
14068 symbol table, whether or not its arguments are of the correct type. For
14069 overloaded functions that are class member functions, @value{GDBN}
14070 searches for a function whose signature @emph{exactly} matches the
14073 @kindex show overload-resolution
14074 @item show overload-resolution
14075 Show the current setting of overload resolution.
14077 @item @r{Overloaded symbol names}
14078 You can specify a particular definition of an overloaded symbol, using
14079 the same notation that is used to declare such symbols in C@t{++}: type
14080 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
14081 also use the @value{GDBN} command-line word completion facilities to list the
14082 available choices, or to finish the type list for you.
14083 @xref{Completion,, Command Completion}, for details on how to do this.
14086 @node Decimal Floating Point
14087 @subsubsection Decimal Floating Point format
14088 @cindex decimal floating point format
14090 @value{GDBN} can examine, set and perform computations with numbers in
14091 decimal floating point format, which in the C language correspond to the
14092 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
14093 specified by the extension to support decimal floating-point arithmetic.
14095 There are two encodings in use, depending on the architecture: BID (Binary
14096 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
14097 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
14100 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
14101 to manipulate decimal floating point numbers, it is not possible to convert
14102 (using a cast, for example) integers wider than 32-bit to decimal float.
14104 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
14105 point computations, error checking in decimal float operations ignores
14106 underflow, overflow and divide by zero exceptions.
14108 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
14109 to inspect @code{_Decimal128} values stored in floating point registers.
14110 See @ref{PowerPC,,PowerPC} for more details.
14116 @value{GDBN} can be used to debug programs written in D and compiled with
14117 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
14118 specific feature --- dynamic arrays.
14123 @cindex Go (programming language)
14124 @value{GDBN} can be used to debug programs written in Go and compiled with
14125 @file{gccgo} or @file{6g} compilers.
14127 Here is a summary of the Go-specific features and restrictions:
14130 @cindex current Go package
14131 @item The current Go package
14132 The name of the current package does not need to be specified when
14133 specifying global variables and functions.
14135 For example, given the program:
14139 var myglob = "Shall we?"
14145 When stopped inside @code{main} either of these work:
14149 (gdb) p main.myglob
14152 @cindex builtin Go types
14153 @item Builtin Go types
14154 The @code{string} type is recognized by @value{GDBN} and is printed
14157 @cindex builtin Go functions
14158 @item Builtin Go functions
14159 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
14160 function and handles it internally.
14162 @cindex restrictions on Go expressions
14163 @item Restrictions on Go expressions
14164 All Go operators are supported except @code{&^}.
14165 The Go @code{_} ``blank identifier'' is not supported.
14166 Automatic dereferencing of pointers is not supported.
14170 @subsection Objective-C
14172 @cindex Objective-C
14173 This section provides information about some commands and command
14174 options that are useful for debugging Objective-C code. See also
14175 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
14176 few more commands specific to Objective-C support.
14179 * Method Names in Commands::
14180 * The Print Command with Objective-C::
14183 @node Method Names in Commands
14184 @subsubsection Method Names in Commands
14186 The following commands have been extended to accept Objective-C method
14187 names as line specifications:
14189 @kindex clear@r{, and Objective-C}
14190 @kindex break@r{, and Objective-C}
14191 @kindex info line@r{, and Objective-C}
14192 @kindex jump@r{, and Objective-C}
14193 @kindex list@r{, and Objective-C}
14197 @item @code{info line}
14202 A fully qualified Objective-C method name is specified as
14205 -[@var{Class} @var{methodName}]
14208 where the minus sign is used to indicate an instance method and a
14209 plus sign (not shown) is used to indicate a class method. The class
14210 name @var{Class} and method name @var{methodName} are enclosed in
14211 brackets, similar to the way messages are specified in Objective-C
14212 source code. For example, to set a breakpoint at the @code{create}
14213 instance method of class @code{Fruit} in the program currently being
14217 break -[Fruit create]
14220 To list ten program lines around the @code{initialize} class method,
14224 list +[NSText initialize]
14227 In the current version of @value{GDBN}, the plus or minus sign is
14228 required. In future versions of @value{GDBN}, the plus or minus
14229 sign will be optional, but you can use it to narrow the search. It
14230 is also possible to specify just a method name:
14236 You must specify the complete method name, including any colons. If
14237 your program's source files contain more than one @code{create} method,
14238 you'll be presented with a numbered list of classes that implement that
14239 method. Indicate your choice by number, or type @samp{0} to exit if
14242 As another example, to clear a breakpoint established at the
14243 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
14246 clear -[NSWindow makeKeyAndOrderFront:]
14249 @node The Print Command with Objective-C
14250 @subsubsection The Print Command With Objective-C
14251 @cindex Objective-C, print objects
14252 @kindex print-object
14253 @kindex po @r{(@code{print-object})}
14255 The print command has also been extended to accept methods. For example:
14258 print -[@var{object} hash]
14261 @cindex print an Objective-C object description
14262 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
14264 will tell @value{GDBN} to send the @code{hash} message to @var{object}
14265 and print the result. Also, an additional command has been added,
14266 @code{print-object} or @code{po} for short, which is meant to print
14267 the description of an object. However, this command may only work
14268 with certain Objective-C libraries that have a particular hook
14269 function, @code{_NSPrintForDebugger}, defined.
14272 @subsection OpenCL C
14275 This section provides information about @value{GDBN}s OpenCL C support.
14278 * OpenCL C Datatypes::
14279 * OpenCL C Expressions::
14280 * OpenCL C Operators::
14283 @node OpenCL C Datatypes
14284 @subsubsection OpenCL C Datatypes
14286 @cindex OpenCL C Datatypes
14287 @value{GDBN} supports the builtin scalar and vector datatypes specified
14288 by OpenCL 1.1. In addition the half- and double-precision floating point
14289 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
14290 extensions are also known to @value{GDBN}.
14292 @node OpenCL C Expressions
14293 @subsubsection OpenCL C Expressions
14295 @cindex OpenCL C Expressions
14296 @value{GDBN} supports accesses to vector components including the access as
14297 lvalue where possible. Since OpenCL C is based on C99 most C expressions
14298 supported by @value{GDBN} can be used as well.
14300 @node OpenCL C Operators
14301 @subsubsection OpenCL C Operators
14303 @cindex OpenCL C Operators
14304 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
14308 @subsection Fortran
14309 @cindex Fortran-specific support in @value{GDBN}
14311 @value{GDBN} can be used to debug programs written in Fortran, but it
14312 currently supports only the features of Fortran 77 language.
14314 @cindex trailing underscore, in Fortran symbols
14315 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
14316 among them) append an underscore to the names of variables and
14317 functions. When you debug programs compiled by those compilers, you
14318 will need to refer to variables and functions with a trailing
14322 * Fortran Operators:: Fortran operators and expressions
14323 * Fortran Defaults:: Default settings for Fortran
14324 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
14327 @node Fortran Operators
14328 @subsubsection Fortran Operators and Expressions
14330 @cindex Fortran operators and expressions
14332 Operators must be defined on values of specific types. For instance,
14333 @code{+} is defined on numbers, but not on characters or other non-
14334 arithmetic types. Operators are often defined on groups of types.
14338 The exponentiation operator. It raises the first operand to the power
14342 The range operator. Normally used in the form of array(low:high) to
14343 represent a section of array.
14346 The access component operator. Normally used to access elements in derived
14347 types. Also suitable for unions. As unions aren't part of regular Fortran,
14348 this can only happen when accessing a register that uses a gdbarch-defined
14352 @node Fortran Defaults
14353 @subsubsection Fortran Defaults
14355 @cindex Fortran Defaults
14357 Fortran symbols are usually case-insensitive, so @value{GDBN} by
14358 default uses case-insensitive matches for Fortran symbols. You can
14359 change that with the @samp{set case-insensitive} command, see
14360 @ref{Symbols}, for the details.
14362 @node Special Fortran Commands
14363 @subsubsection Special Fortran Commands
14365 @cindex Special Fortran commands
14367 @value{GDBN} has some commands to support Fortran-specific features,
14368 such as displaying common blocks.
14371 @cindex @code{COMMON} blocks, Fortran
14372 @kindex info common
14373 @item info common @r{[}@var{common-name}@r{]}
14374 This command prints the values contained in the Fortran @code{COMMON}
14375 block whose name is @var{common-name}. With no argument, the names of
14376 all @code{COMMON} blocks visible at the current program location are
14383 @cindex Pascal support in @value{GDBN}, limitations
14384 Debugging Pascal programs which use sets, subranges, file variables, or
14385 nested functions does not currently work. @value{GDBN} does not support
14386 entering expressions, printing values, or similar features using Pascal
14389 The Pascal-specific command @code{set print pascal_static-members}
14390 controls whether static members of Pascal objects are displayed.
14391 @xref{Print Settings, pascal_static-members}.
14394 @subsection Modula-2
14396 @cindex Modula-2, @value{GDBN} support
14398 The extensions made to @value{GDBN} to support Modula-2 only support
14399 output from the @sc{gnu} Modula-2 compiler (which is currently being
14400 developed). Other Modula-2 compilers are not currently supported, and
14401 attempting to debug executables produced by them is most likely
14402 to give an error as @value{GDBN} reads in the executable's symbol
14405 @cindex expressions in Modula-2
14407 * M2 Operators:: Built-in operators
14408 * Built-In Func/Proc:: Built-in functions and procedures
14409 * M2 Constants:: Modula-2 constants
14410 * M2 Types:: Modula-2 types
14411 * M2 Defaults:: Default settings for Modula-2
14412 * Deviations:: Deviations from standard Modula-2
14413 * M2 Checks:: Modula-2 type and range checks
14414 * M2 Scope:: The scope operators @code{::} and @code{.}
14415 * GDB/M2:: @value{GDBN} and Modula-2
14419 @subsubsection Operators
14420 @cindex Modula-2 operators
14422 Operators must be defined on values of specific types. For instance,
14423 @code{+} is defined on numbers, but not on structures. Operators are
14424 often defined on groups of types. For the purposes of Modula-2, the
14425 following definitions hold:
14430 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
14434 @emph{Character types} consist of @code{CHAR} and its subranges.
14437 @emph{Floating-point types} consist of @code{REAL}.
14440 @emph{Pointer types} consist of anything declared as @code{POINTER TO
14444 @emph{Scalar types} consist of all of the above.
14447 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
14450 @emph{Boolean types} consist of @code{BOOLEAN}.
14454 The following operators are supported, and appear in order of
14455 increasing precedence:
14459 Function argument or array index separator.
14462 Assignment. The value of @var{var} @code{:=} @var{value} is
14466 Less than, greater than on integral, floating-point, or enumerated
14470 Less than or equal to, greater than or equal to
14471 on integral, floating-point and enumerated types, or set inclusion on
14472 set types. Same precedence as @code{<}.
14474 @item =@r{, }<>@r{, }#
14475 Equality and two ways of expressing inequality, valid on scalar types.
14476 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
14477 available for inequality, since @code{#} conflicts with the script
14481 Set membership. Defined on set types and the types of their members.
14482 Same precedence as @code{<}.
14485 Boolean disjunction. Defined on boolean types.
14488 Boolean conjunction. Defined on boolean types.
14491 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14494 Addition and subtraction on integral and floating-point types, or union
14495 and difference on set types.
14498 Multiplication on integral and floating-point types, or set intersection
14502 Division on floating-point types, or symmetric set difference on set
14503 types. Same precedence as @code{*}.
14506 Integer division and remainder. Defined on integral types. Same
14507 precedence as @code{*}.
14510 Negative. Defined on @code{INTEGER} and @code{REAL} data.
14513 Pointer dereferencing. Defined on pointer types.
14516 Boolean negation. Defined on boolean types. Same precedence as
14520 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
14521 precedence as @code{^}.
14524 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
14527 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
14531 @value{GDBN} and Modula-2 scope operators.
14535 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
14536 treats the use of the operator @code{IN}, or the use of operators
14537 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
14538 @code{<=}, and @code{>=} on sets as an error.
14542 @node Built-In Func/Proc
14543 @subsubsection Built-in Functions and Procedures
14544 @cindex Modula-2 built-ins
14546 Modula-2 also makes available several built-in procedures and functions.
14547 In describing these, the following metavariables are used:
14552 represents an @code{ARRAY} variable.
14555 represents a @code{CHAR} constant or variable.
14558 represents a variable or constant of integral type.
14561 represents an identifier that belongs to a set. Generally used in the
14562 same function with the metavariable @var{s}. The type of @var{s} should
14563 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
14566 represents a variable or constant of integral or floating-point type.
14569 represents a variable or constant of floating-point type.
14575 represents a variable.
14578 represents a variable or constant of one of many types. See the
14579 explanation of the function for details.
14582 All Modula-2 built-in procedures also return a result, described below.
14586 Returns the absolute value of @var{n}.
14589 If @var{c} is a lower case letter, it returns its upper case
14590 equivalent, otherwise it returns its argument.
14593 Returns the character whose ordinal value is @var{i}.
14596 Decrements the value in the variable @var{v} by one. Returns the new value.
14598 @item DEC(@var{v},@var{i})
14599 Decrements the value in the variable @var{v} by @var{i}. Returns the
14602 @item EXCL(@var{m},@var{s})
14603 Removes the element @var{m} from the set @var{s}. Returns the new
14606 @item FLOAT(@var{i})
14607 Returns the floating point equivalent of the integer @var{i}.
14609 @item HIGH(@var{a})
14610 Returns the index of the last member of @var{a}.
14613 Increments the value in the variable @var{v} by one. Returns the new value.
14615 @item INC(@var{v},@var{i})
14616 Increments the value in the variable @var{v} by @var{i}. Returns the
14619 @item INCL(@var{m},@var{s})
14620 Adds the element @var{m} to the set @var{s} if it is not already
14621 there. Returns the new set.
14624 Returns the maximum value of the type @var{t}.
14627 Returns the minimum value of the type @var{t}.
14630 Returns boolean TRUE if @var{i} is an odd number.
14633 Returns the ordinal value of its argument. For example, the ordinal
14634 value of a character is its @sc{ascii} value (on machines supporting the
14635 @sc{ascii} character set). @var{x} must be of an ordered type, which include
14636 integral, character and enumerated types.
14638 @item SIZE(@var{x})
14639 Returns the size of its argument. @var{x} can be a variable or a type.
14641 @item TRUNC(@var{r})
14642 Returns the integral part of @var{r}.
14644 @item TSIZE(@var{x})
14645 Returns the size of its argument. @var{x} can be a variable or a type.
14647 @item VAL(@var{t},@var{i})
14648 Returns the member of the type @var{t} whose ordinal value is @var{i}.
14652 @emph{Warning:} Sets and their operations are not yet supported, so
14653 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
14657 @cindex Modula-2 constants
14659 @subsubsection Constants
14661 @value{GDBN} allows you to express the constants of Modula-2 in the following
14667 Integer constants are simply a sequence of digits. When used in an
14668 expression, a constant is interpreted to be type-compatible with the
14669 rest of the expression. Hexadecimal integers are specified by a
14670 trailing @samp{H}, and octal integers by a trailing @samp{B}.
14673 Floating point constants appear as a sequence of digits, followed by a
14674 decimal point and another sequence of digits. An optional exponent can
14675 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
14676 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
14677 digits of the floating point constant must be valid decimal (base 10)
14681 Character constants consist of a single character enclosed by a pair of
14682 like quotes, either single (@code{'}) or double (@code{"}). They may
14683 also be expressed by their ordinal value (their @sc{ascii} value, usually)
14684 followed by a @samp{C}.
14687 String constants consist of a sequence of characters enclosed by a
14688 pair of like quotes, either single (@code{'}) or double (@code{"}).
14689 Escape sequences in the style of C are also allowed. @xref{C
14690 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
14694 Enumerated constants consist of an enumerated identifier.
14697 Boolean constants consist of the identifiers @code{TRUE} and
14701 Pointer constants consist of integral values only.
14704 Set constants are not yet supported.
14708 @subsubsection Modula-2 Types
14709 @cindex Modula-2 types
14711 Currently @value{GDBN} can print the following data types in Modula-2
14712 syntax: array types, record types, set types, pointer types, procedure
14713 types, enumerated types, subrange types and base types. You can also
14714 print the contents of variables declared using these type.
14715 This section gives a number of simple source code examples together with
14716 sample @value{GDBN} sessions.
14718 The first example contains the following section of code:
14727 and you can request @value{GDBN} to interrogate the type and value of
14728 @code{r} and @code{s}.
14731 (@value{GDBP}) print s
14733 (@value{GDBP}) ptype s
14735 (@value{GDBP}) print r
14737 (@value{GDBP}) ptype r
14742 Likewise if your source code declares @code{s} as:
14746 s: SET ['A'..'Z'] ;
14750 then you may query the type of @code{s} by:
14753 (@value{GDBP}) ptype s
14754 type = SET ['A'..'Z']
14758 Note that at present you cannot interactively manipulate set
14759 expressions using the debugger.
14761 The following example shows how you might declare an array in Modula-2
14762 and how you can interact with @value{GDBN} to print its type and contents:
14766 s: ARRAY [-10..10] OF CHAR ;
14770 (@value{GDBP}) ptype s
14771 ARRAY [-10..10] OF CHAR
14774 Note that the array handling is not yet complete and although the type
14775 is printed correctly, expression handling still assumes that all
14776 arrays have a lower bound of zero and not @code{-10} as in the example
14779 Here are some more type related Modula-2 examples:
14783 colour = (blue, red, yellow, green) ;
14784 t = [blue..yellow] ;
14792 The @value{GDBN} interaction shows how you can query the data type
14793 and value of a variable.
14796 (@value{GDBP}) print s
14798 (@value{GDBP}) ptype t
14799 type = [blue..yellow]
14803 In this example a Modula-2 array is declared and its contents
14804 displayed. Observe that the contents are written in the same way as
14805 their @code{C} counterparts.
14809 s: ARRAY [1..5] OF CARDINAL ;
14815 (@value{GDBP}) print s
14816 $1 = @{1, 0, 0, 0, 0@}
14817 (@value{GDBP}) ptype s
14818 type = ARRAY [1..5] OF CARDINAL
14821 The Modula-2 language interface to @value{GDBN} also understands
14822 pointer types as shown in this example:
14826 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
14833 and you can request that @value{GDBN} describes the type of @code{s}.
14836 (@value{GDBP}) ptype s
14837 type = POINTER TO ARRAY [1..5] OF CARDINAL
14840 @value{GDBN} handles compound types as we can see in this example.
14841 Here we combine array types, record types, pointer types and subrange
14852 myarray = ARRAY myrange OF CARDINAL ;
14853 myrange = [-2..2] ;
14855 s: POINTER TO ARRAY myrange OF foo ;
14859 and you can ask @value{GDBN} to describe the type of @code{s} as shown
14863 (@value{GDBP}) ptype s
14864 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
14867 f3 : ARRAY [-2..2] OF CARDINAL;
14872 @subsubsection Modula-2 Defaults
14873 @cindex Modula-2 defaults
14875 If type and range checking are set automatically by @value{GDBN}, they
14876 both default to @code{on} whenever the working language changes to
14877 Modula-2. This happens regardless of whether you or @value{GDBN}
14878 selected the working language.
14880 If you allow @value{GDBN} to set the language automatically, then entering
14881 code compiled from a file whose name ends with @file{.mod} sets the
14882 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
14883 Infer the Source Language}, for further details.
14886 @subsubsection Deviations from Standard Modula-2
14887 @cindex Modula-2, deviations from
14889 A few changes have been made to make Modula-2 programs easier to debug.
14890 This is done primarily via loosening its type strictness:
14894 Unlike in standard Modula-2, pointer constants can be formed by
14895 integers. This allows you to modify pointer variables during
14896 debugging. (In standard Modula-2, the actual address contained in a
14897 pointer variable is hidden from you; it can only be modified
14898 through direct assignment to another pointer variable or expression that
14899 returned a pointer.)
14902 C escape sequences can be used in strings and characters to represent
14903 non-printable characters. @value{GDBN} prints out strings with these
14904 escape sequences embedded. Single non-printable characters are
14905 printed using the @samp{CHR(@var{nnn})} format.
14908 The assignment operator (@code{:=}) returns the value of its right-hand
14912 All built-in procedures both modify @emph{and} return their argument.
14916 @subsubsection Modula-2 Type and Range Checks
14917 @cindex Modula-2 checks
14920 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
14923 @c FIXME remove warning when type/range checks added
14925 @value{GDBN} considers two Modula-2 variables type equivalent if:
14929 They are of types that have been declared equivalent via a @code{TYPE
14930 @var{t1} = @var{t2}} statement
14933 They have been declared on the same line. (Note: This is true of the
14934 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
14937 As long as type checking is enabled, any attempt to combine variables
14938 whose types are not equivalent is an error.
14940 Range checking is done on all mathematical operations, assignment, array
14941 index bounds, and all built-in functions and procedures.
14944 @subsubsection The Scope Operators @code{::} and @code{.}
14946 @cindex @code{.}, Modula-2 scope operator
14947 @cindex colon, doubled as scope operator
14949 @vindex colon-colon@r{, in Modula-2}
14950 @c Info cannot handle :: but TeX can.
14953 @vindex ::@r{, in Modula-2}
14956 There are a few subtle differences between the Modula-2 scope operator
14957 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
14962 @var{module} . @var{id}
14963 @var{scope} :: @var{id}
14967 where @var{scope} is the name of a module or a procedure,
14968 @var{module} the name of a module, and @var{id} is any declared
14969 identifier within your program, except another module.
14971 Using the @code{::} operator makes @value{GDBN} search the scope
14972 specified by @var{scope} for the identifier @var{id}. If it is not
14973 found in the specified scope, then @value{GDBN} searches all scopes
14974 enclosing the one specified by @var{scope}.
14976 Using the @code{.} operator makes @value{GDBN} search the current scope for
14977 the identifier specified by @var{id} that was imported from the
14978 definition module specified by @var{module}. With this operator, it is
14979 an error if the identifier @var{id} was not imported from definition
14980 module @var{module}, or if @var{id} is not an identifier in
14984 @subsubsection @value{GDBN} and Modula-2
14986 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
14987 Five subcommands of @code{set print} and @code{show print} apply
14988 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
14989 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
14990 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
14991 analogue in Modula-2.
14993 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
14994 with any language, is not useful with Modula-2. Its
14995 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
14996 created in Modula-2 as they can in C or C@t{++}. However, because an
14997 address can be specified by an integral constant, the construct
14998 @samp{@{@var{type}@}@var{adrexp}} is still useful.
15000 @cindex @code{#} in Modula-2
15001 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
15002 interpreted as the beginning of a comment. Use @code{<>} instead.
15008 The extensions made to @value{GDBN} for Ada only support
15009 output from the @sc{gnu} Ada (GNAT) compiler.
15010 Other Ada compilers are not currently supported, and
15011 attempting to debug executables produced by them is most likely
15015 @cindex expressions in Ada
15017 * Ada Mode Intro:: General remarks on the Ada syntax
15018 and semantics supported by Ada mode
15020 * Omissions from Ada:: Restrictions on the Ada expression syntax.
15021 * Additions to Ada:: Extensions of the Ada expression syntax.
15022 * Stopping Before Main Program:: Debugging the program during elaboration.
15023 * Ada Exceptions:: Ada Exceptions
15024 * Ada Tasks:: Listing and setting breakpoints in tasks.
15025 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
15026 * Ravenscar Profile:: Tasking Support when using the Ravenscar
15028 * Ada Glitches:: Known peculiarities of Ada mode.
15031 @node Ada Mode Intro
15032 @subsubsection Introduction
15033 @cindex Ada mode, general
15035 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
15036 syntax, with some extensions.
15037 The philosophy behind the design of this subset is
15041 That @value{GDBN} should provide basic literals and access to operations for
15042 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
15043 leaving more sophisticated computations to subprograms written into the
15044 program (which therefore may be called from @value{GDBN}).
15047 That type safety and strict adherence to Ada language restrictions
15048 are not particularly important to the @value{GDBN} user.
15051 That brevity is important to the @value{GDBN} user.
15054 Thus, for brevity, the debugger acts as if all names declared in
15055 user-written packages are directly visible, even if they are not visible
15056 according to Ada rules, thus making it unnecessary to fully qualify most
15057 names with their packages, regardless of context. Where this causes
15058 ambiguity, @value{GDBN} asks the user's intent.
15060 The debugger will start in Ada mode if it detects an Ada main program.
15061 As for other languages, it will enter Ada mode when stopped in a program that
15062 was translated from an Ada source file.
15064 While in Ada mode, you may use `@t{--}' for comments. This is useful
15065 mostly for documenting command files. The standard @value{GDBN} comment
15066 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
15067 middle (to allow based literals).
15069 The debugger supports limited overloading. Given a subprogram call in which
15070 the function symbol has multiple definitions, it will use the number of
15071 actual parameters and some information about their types to attempt to narrow
15072 the set of definitions. It also makes very limited use of context, preferring
15073 procedures to functions in the context of the @code{call} command, and
15074 functions to procedures elsewhere.
15076 @node Omissions from Ada
15077 @subsubsection Omissions from Ada
15078 @cindex Ada, omissions from
15080 Here are the notable omissions from the subset:
15084 Only a subset of the attributes are supported:
15088 @t{'First}, @t{'Last}, and @t{'Length}
15089 on array objects (not on types and subtypes).
15092 @t{'Min} and @t{'Max}.
15095 @t{'Pos} and @t{'Val}.
15101 @t{'Range} on array objects (not subtypes), but only as the right
15102 operand of the membership (@code{in}) operator.
15105 @t{'Access}, @t{'Unchecked_Access}, and
15106 @t{'Unrestricted_Access} (a GNAT extension).
15114 @code{Characters.Latin_1} are not available and
15115 concatenation is not implemented. Thus, escape characters in strings are
15116 not currently available.
15119 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
15120 equality of representations. They will generally work correctly
15121 for strings and arrays whose elements have integer or enumeration types.
15122 They may not work correctly for arrays whose element
15123 types have user-defined equality, for arrays of real values
15124 (in particular, IEEE-conformant floating point, because of negative
15125 zeroes and NaNs), and for arrays whose elements contain unused bits with
15126 indeterminate values.
15129 The other component-by-component array operations (@code{and}, @code{or},
15130 @code{xor}, @code{not}, and relational tests other than equality)
15131 are not implemented.
15134 @cindex array aggregates (Ada)
15135 @cindex record aggregates (Ada)
15136 @cindex aggregates (Ada)
15137 There is limited support for array and record aggregates. They are
15138 permitted only on the right sides of assignments, as in these examples:
15141 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
15142 (@value{GDBP}) set An_Array := (1, others => 0)
15143 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
15144 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
15145 (@value{GDBP}) set A_Record := (1, "Peter", True);
15146 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
15150 discriminant's value by assigning an aggregate has an
15151 undefined effect if that discriminant is used within the record.
15152 However, you can first modify discriminants by directly assigning to
15153 them (which normally would not be allowed in Ada), and then performing an
15154 aggregate assignment. For example, given a variable @code{A_Rec}
15155 declared to have a type such as:
15158 type Rec (Len : Small_Integer := 0) is record
15160 Vals : IntArray (1 .. Len);
15164 you can assign a value with a different size of @code{Vals} with two
15168 (@value{GDBP}) set A_Rec.Len := 4
15169 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
15172 As this example also illustrates, @value{GDBN} is very loose about the usual
15173 rules concerning aggregates. You may leave out some of the
15174 components of an array or record aggregate (such as the @code{Len}
15175 component in the assignment to @code{A_Rec} above); they will retain their
15176 original values upon assignment. You may freely use dynamic values as
15177 indices in component associations. You may even use overlapping or
15178 redundant component associations, although which component values are
15179 assigned in such cases is not defined.
15182 Calls to dispatching subprograms are not implemented.
15185 The overloading algorithm is much more limited (i.e., less selective)
15186 than that of real Ada. It makes only limited use of the context in
15187 which a subexpression appears to resolve its meaning, and it is much
15188 looser in its rules for allowing type matches. As a result, some
15189 function calls will be ambiguous, and the user will be asked to choose
15190 the proper resolution.
15193 The @code{new} operator is not implemented.
15196 Entry calls are not implemented.
15199 Aside from printing, arithmetic operations on the native VAX floating-point
15200 formats are not supported.
15203 It is not possible to slice a packed array.
15206 The names @code{True} and @code{False}, when not part of a qualified name,
15207 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
15209 Should your program
15210 redefine these names in a package or procedure (at best a dubious practice),
15211 you will have to use fully qualified names to access their new definitions.
15214 @node Additions to Ada
15215 @subsubsection Additions to Ada
15216 @cindex Ada, deviations from
15218 As it does for other languages, @value{GDBN} makes certain generic
15219 extensions to Ada (@pxref{Expressions}):
15223 If the expression @var{E} is a variable residing in memory (typically
15224 a local variable or array element) and @var{N} is a positive integer,
15225 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
15226 @var{N}-1 adjacent variables following it in memory as an array. In
15227 Ada, this operator is generally not necessary, since its prime use is
15228 in displaying parts of an array, and slicing will usually do this in
15229 Ada. However, there are occasional uses when debugging programs in
15230 which certain debugging information has been optimized away.
15233 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
15234 appears in function or file @var{B}.'' When @var{B} is a file name,
15235 you must typically surround it in single quotes.
15238 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
15239 @var{type} that appears at address @var{addr}.''
15242 A name starting with @samp{$} is a convenience variable
15243 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
15246 In addition, @value{GDBN} provides a few other shortcuts and outright
15247 additions specific to Ada:
15251 The assignment statement is allowed as an expression, returning
15252 its right-hand operand as its value. Thus, you may enter
15255 (@value{GDBP}) set x := y + 3
15256 (@value{GDBP}) print A(tmp := y + 1)
15260 The semicolon is allowed as an ``operator,'' returning as its value
15261 the value of its right-hand operand.
15262 This allows, for example,
15263 complex conditional breaks:
15266 (@value{GDBP}) break f
15267 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
15271 Rather than use catenation and symbolic character names to introduce special
15272 characters into strings, one may instead use a special bracket notation,
15273 which is also used to print strings. A sequence of characters of the form
15274 @samp{["@var{XX}"]} within a string or character literal denotes the
15275 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
15276 sequence of characters @samp{["""]} also denotes a single quotation mark
15277 in strings. For example,
15279 "One line.["0a"]Next line.["0a"]"
15282 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
15286 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
15287 @t{'Max} is optional (and is ignored in any case). For example, it is valid
15291 (@value{GDBP}) print 'max(x, y)
15295 When printing arrays, @value{GDBN} uses positional notation when the
15296 array has a lower bound of 1, and uses a modified named notation otherwise.
15297 For example, a one-dimensional array of three integers with a lower bound
15298 of 3 might print as
15305 That is, in contrast to valid Ada, only the first component has a @code{=>}
15309 You may abbreviate attributes in expressions with any unique,
15310 multi-character subsequence of
15311 their names (an exact match gets preference).
15312 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
15313 in place of @t{a'length}.
15316 @cindex quoting Ada internal identifiers
15317 Since Ada is case-insensitive, the debugger normally maps identifiers you type
15318 to lower case. The GNAT compiler uses upper-case characters for
15319 some of its internal identifiers, which are normally of no interest to users.
15320 For the rare occasions when you actually have to look at them,
15321 enclose them in angle brackets to avoid the lower-case mapping.
15324 (@value{GDBP}) print <JMPBUF_SAVE>[0]
15328 Printing an object of class-wide type or dereferencing an
15329 access-to-class-wide value will display all the components of the object's
15330 specific type (as indicated by its run-time tag). Likewise, component
15331 selection on such a value will operate on the specific type of the
15336 @node Stopping Before Main Program
15337 @subsubsection Stopping at the Very Beginning
15339 @cindex breakpointing Ada elaboration code
15340 It is sometimes necessary to debug the program during elaboration, and
15341 before reaching the main procedure.
15342 As defined in the Ada Reference
15343 Manual, the elaboration code is invoked from a procedure called
15344 @code{adainit}. To run your program up to the beginning of
15345 elaboration, simply use the following two commands:
15346 @code{tbreak adainit} and @code{run}.
15348 @node Ada Exceptions
15349 @subsubsection Ada Exceptions
15351 A command is provided to list all Ada exceptions:
15354 @kindex info exceptions
15355 @item info exceptions
15356 @itemx info exceptions @var{regexp}
15357 The @code{info exceptions} command allows you to list all Ada exceptions
15358 defined within the program being debugged, as well as their addresses.
15359 With a regular expression, @var{regexp}, as argument, only those exceptions
15360 whose names match @var{regexp} are listed.
15363 Below is a small example, showing how the command can be used, first
15364 without argument, and next with a regular expression passed as an
15368 (@value{GDBP}) info exceptions
15369 All defined Ada exceptions:
15370 constraint_error: 0x613da0
15371 program_error: 0x613d20
15372 storage_error: 0x613ce0
15373 tasking_error: 0x613ca0
15374 const.aint_global_e: 0x613b00
15375 (@value{GDBP}) info exceptions const.aint
15376 All Ada exceptions matching regular expression "const.aint":
15377 constraint_error: 0x613da0
15378 const.aint_global_e: 0x613b00
15381 It is also possible to ask @value{GDBN} to stop your program's execution
15382 when an exception is raised. For more details, see @ref{Set Catchpoints}.
15385 @subsubsection Extensions for Ada Tasks
15386 @cindex Ada, tasking
15388 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
15389 @value{GDBN} provides the following task-related commands:
15394 This command shows a list of current Ada tasks, as in the following example:
15401 (@value{GDBP}) info tasks
15402 ID TID P-ID Pri State Name
15403 1 8088000 0 15 Child Activation Wait main_task
15404 2 80a4000 1 15 Accept Statement b
15405 3 809a800 1 15 Child Activation Wait a
15406 * 4 80ae800 3 15 Runnable c
15411 In this listing, the asterisk before the last task indicates it to be the
15412 task currently being inspected.
15416 Represents @value{GDBN}'s internal task number.
15422 The parent's task ID (@value{GDBN}'s internal task number).
15425 The base priority of the task.
15428 Current state of the task.
15432 The task has been created but has not been activated. It cannot be
15436 The task is not blocked for any reason known to Ada. (It may be waiting
15437 for a mutex, though.) It is conceptually "executing" in normal mode.
15440 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
15441 that were waiting on terminate alternatives have been awakened and have
15442 terminated themselves.
15444 @item Child Activation Wait
15445 The task is waiting for created tasks to complete activation.
15447 @item Accept Statement
15448 The task is waiting on an accept or selective wait statement.
15450 @item Waiting on entry call
15451 The task is waiting on an entry call.
15453 @item Async Select Wait
15454 The task is waiting to start the abortable part of an asynchronous
15458 The task is waiting on a select statement with only a delay
15461 @item Child Termination Wait
15462 The task is sleeping having completed a master within itself, and is
15463 waiting for the tasks dependent on that master to become terminated or
15464 waiting on a terminate Phase.
15466 @item Wait Child in Term Alt
15467 The task is sleeping waiting for tasks on terminate alternatives to
15468 finish terminating.
15470 @item Accepting RV with @var{taskno}
15471 The task is accepting a rendez-vous with the task @var{taskno}.
15475 Name of the task in the program.
15479 @kindex info task @var{taskno}
15480 @item info task @var{taskno}
15481 This command shows detailled informations on the specified task, as in
15482 the following example:
15487 (@value{GDBP}) info tasks
15488 ID TID P-ID Pri State Name
15489 1 8077880 0 15 Child Activation Wait main_task
15490 * 2 807c468 1 15 Runnable task_1
15491 (@value{GDBP}) info task 2
15492 Ada Task: 0x807c468
15495 Parent: 1 (main_task)
15501 @kindex task@r{ (Ada)}
15502 @cindex current Ada task ID
15503 This command prints the ID of the current task.
15509 (@value{GDBP}) info tasks
15510 ID TID P-ID Pri State Name
15511 1 8077870 0 15 Child Activation Wait main_task
15512 * 2 807c458 1 15 Runnable t
15513 (@value{GDBP}) task
15514 [Current task is 2]
15517 @item task @var{taskno}
15518 @cindex Ada task switching
15519 This command is like the @code{thread @var{threadno}}
15520 command (@pxref{Threads}). It switches the context of debugging
15521 from the current task to the given task.
15527 (@value{GDBP}) info tasks
15528 ID TID P-ID Pri State Name
15529 1 8077870 0 15 Child Activation Wait main_task
15530 * 2 807c458 1 15 Runnable t
15531 (@value{GDBP}) task 1
15532 [Switching to task 1]
15533 #0 0x8067726 in pthread_cond_wait ()
15535 #0 0x8067726 in pthread_cond_wait ()
15536 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
15537 #2 0x805cb63 in system.task_primitives.operations.sleep ()
15538 #3 0x806153e in system.tasking.stages.activate_tasks ()
15539 #4 0x804aacc in un () at un.adb:5
15542 @item break @var{linespec} task @var{taskno}
15543 @itemx break @var{linespec} task @var{taskno} if @dots{}
15544 @cindex breakpoints and tasks, in Ada
15545 @cindex task breakpoints, in Ada
15546 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
15547 These commands are like the @code{break @dots{} thread @dots{}}
15548 command (@pxref{Thread Stops}).
15549 @var{linespec} specifies source lines, as described
15550 in @ref{Specify Location}.
15552 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
15553 to specify that you only want @value{GDBN} to stop the program when a
15554 particular Ada task reaches this breakpoint. @var{taskno} is one of the
15555 numeric task identifiers assigned by @value{GDBN}, shown in the first
15556 column of the @samp{info tasks} display.
15558 If you do not specify @samp{task @var{taskno}} when you set a
15559 breakpoint, the breakpoint applies to @emph{all} tasks of your
15562 You can use the @code{task} qualifier on conditional breakpoints as
15563 well; in this case, place @samp{task @var{taskno}} before the
15564 breakpoint condition (before the @code{if}).
15572 (@value{GDBP}) info tasks
15573 ID TID P-ID Pri State Name
15574 1 140022020 0 15 Child Activation Wait main_task
15575 2 140045060 1 15 Accept/Select Wait t2
15576 3 140044840 1 15 Runnable t1
15577 * 4 140056040 1 15 Runnable t3
15578 (@value{GDBP}) b 15 task 2
15579 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
15580 (@value{GDBP}) cont
15585 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
15587 (@value{GDBP}) info tasks
15588 ID TID P-ID Pri State Name
15589 1 140022020 0 15 Child Activation Wait main_task
15590 * 2 140045060 1 15 Runnable t2
15591 3 140044840 1 15 Runnable t1
15592 4 140056040 1 15 Delay Sleep t3
15596 @node Ada Tasks and Core Files
15597 @subsubsection Tasking Support when Debugging Core Files
15598 @cindex Ada tasking and core file debugging
15600 When inspecting a core file, as opposed to debugging a live program,
15601 tasking support may be limited or even unavailable, depending on
15602 the platform being used.
15603 For instance, on x86-linux, the list of tasks is available, but task
15604 switching is not supported. On Tru64, however, task switching will work
15607 On certain platforms, including Tru64, the debugger needs to perform some
15608 memory writes in order to provide Ada tasking support. When inspecting
15609 a core file, this means that the core file must be opened with read-write
15610 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
15611 Under these circumstances, you should make a backup copy of the core
15612 file before inspecting it with @value{GDBN}.
15614 @node Ravenscar Profile
15615 @subsubsection Tasking Support when using the Ravenscar Profile
15616 @cindex Ravenscar Profile
15618 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
15619 specifically designed for systems with safety-critical real-time
15623 @kindex set ravenscar task-switching on
15624 @cindex task switching with program using Ravenscar Profile
15625 @item set ravenscar task-switching on
15626 Allows task switching when debugging a program that uses the Ravenscar
15627 Profile. This is the default.
15629 @kindex set ravenscar task-switching off
15630 @item set ravenscar task-switching off
15631 Turn off task switching when debugging a program that uses the Ravenscar
15632 Profile. This is mostly intended to disable the code that adds support
15633 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
15634 the Ravenscar runtime is preventing @value{GDBN} from working properly.
15635 To be effective, this command should be run before the program is started.
15637 @kindex show ravenscar task-switching
15638 @item show ravenscar task-switching
15639 Show whether it is possible to switch from task to task in a program
15640 using the Ravenscar Profile.
15645 @subsubsection Known Peculiarities of Ada Mode
15646 @cindex Ada, problems
15648 Besides the omissions listed previously (@pxref{Omissions from Ada}),
15649 we know of several problems with and limitations of Ada mode in
15651 some of which will be fixed with planned future releases of the debugger
15652 and the GNU Ada compiler.
15656 Static constants that the compiler chooses not to materialize as objects in
15657 storage are invisible to the debugger.
15660 Named parameter associations in function argument lists are ignored (the
15661 argument lists are treated as positional).
15664 Many useful library packages are currently invisible to the debugger.
15667 Fixed-point arithmetic, conversions, input, and output is carried out using
15668 floating-point arithmetic, and may give results that only approximate those on
15672 The GNAT compiler never generates the prefix @code{Standard} for any of
15673 the standard symbols defined by the Ada language. @value{GDBN} knows about
15674 this: it will strip the prefix from names when you use it, and will never
15675 look for a name you have so qualified among local symbols, nor match against
15676 symbols in other packages or subprograms. If you have
15677 defined entities anywhere in your program other than parameters and
15678 local variables whose simple names match names in @code{Standard},
15679 GNAT's lack of qualification here can cause confusion. When this happens,
15680 you can usually resolve the confusion
15681 by qualifying the problematic names with package
15682 @code{Standard} explicitly.
15685 Older versions of the compiler sometimes generate erroneous debugging
15686 information, resulting in the debugger incorrectly printing the value
15687 of affected entities. In some cases, the debugger is able to work
15688 around an issue automatically. In other cases, the debugger is able
15689 to work around the issue, but the work-around has to be specifically
15692 @kindex set ada trust-PAD-over-XVS
15693 @kindex show ada trust-PAD-over-XVS
15696 @item set ada trust-PAD-over-XVS on
15697 Configure GDB to strictly follow the GNAT encoding when computing the
15698 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
15699 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
15700 a complete description of the encoding used by the GNAT compiler).
15701 This is the default.
15703 @item set ada trust-PAD-over-XVS off
15704 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
15705 sometimes prints the wrong value for certain entities, changing @code{ada
15706 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
15707 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
15708 @code{off}, but this incurs a slight performance penalty, so it is
15709 recommended to leave this setting to @code{on} unless necessary.
15713 @node Unsupported Languages
15714 @section Unsupported Languages
15716 @cindex unsupported languages
15717 @cindex minimal language
15718 In addition to the other fully-supported programming languages,
15719 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
15720 It does not represent a real programming language, but provides a set
15721 of capabilities close to what the C or assembly languages provide.
15722 This should allow most simple operations to be performed while debugging
15723 an application that uses a language currently not supported by @value{GDBN}.
15725 If the language is set to @code{auto}, @value{GDBN} will automatically
15726 select this language if the current frame corresponds to an unsupported
15730 @chapter Examining the Symbol Table
15732 The commands described in this chapter allow you to inquire about the
15733 symbols (names of variables, functions and types) defined in your
15734 program. This information is inherent in the text of your program and
15735 does not change as your program executes. @value{GDBN} finds it in your
15736 program's symbol table, in the file indicated when you started @value{GDBN}
15737 (@pxref{File Options, ,Choosing Files}), or by one of the
15738 file-management commands (@pxref{Files, ,Commands to Specify Files}).
15740 @cindex symbol names
15741 @cindex names of symbols
15742 @cindex quoting names
15743 Occasionally, you may need to refer to symbols that contain unusual
15744 characters, which @value{GDBN} ordinarily treats as word delimiters. The
15745 most frequent case is in referring to static variables in other
15746 source files (@pxref{Variables,,Program Variables}). File names
15747 are recorded in object files as debugging symbols, but @value{GDBN} would
15748 ordinarily parse a typical file name, like @file{foo.c}, as the three words
15749 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
15750 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
15757 looks up the value of @code{x} in the scope of the file @file{foo.c}.
15760 @cindex case-insensitive symbol names
15761 @cindex case sensitivity in symbol names
15762 @kindex set case-sensitive
15763 @item set case-sensitive on
15764 @itemx set case-sensitive off
15765 @itemx set case-sensitive auto
15766 Normally, when @value{GDBN} looks up symbols, it matches their names
15767 with case sensitivity determined by the current source language.
15768 Occasionally, you may wish to control that. The command @code{set
15769 case-sensitive} lets you do that by specifying @code{on} for
15770 case-sensitive matches or @code{off} for case-insensitive ones. If
15771 you specify @code{auto}, case sensitivity is reset to the default
15772 suitable for the source language. The default is case-sensitive
15773 matches for all languages except for Fortran, for which the default is
15774 case-insensitive matches.
15776 @kindex show case-sensitive
15777 @item show case-sensitive
15778 This command shows the current setting of case sensitivity for symbols
15781 @kindex set print type methods
15782 @item set print type methods
15783 @itemx set print type methods on
15784 @itemx set print type methods off
15785 Normally, when @value{GDBN} prints a class, it displays any methods
15786 declared in that class. You can control this behavior either by
15787 passing the appropriate flag to @code{ptype}, or using @command{set
15788 print type methods}. Specifying @code{on} will cause @value{GDBN} to
15789 display the methods; this is the default. Specifying @code{off} will
15790 cause @value{GDBN} to omit the methods.
15792 @kindex show print type methods
15793 @item show print type methods
15794 This command shows the current setting of method display when printing
15797 @kindex set print type typedefs
15798 @item set print type typedefs
15799 @itemx set print type typedefs on
15800 @itemx set print type typedefs off
15802 Normally, when @value{GDBN} prints a class, it displays any typedefs
15803 defined in that class. You can control this behavior either by
15804 passing the appropriate flag to @code{ptype}, or using @command{set
15805 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
15806 display the typedef definitions; this is the default. Specifying
15807 @code{off} will cause @value{GDBN} to omit the typedef definitions.
15808 Note that this controls whether the typedef definition itself is
15809 printed, not whether typedef names are substituted when printing other
15812 @kindex show print type typedefs
15813 @item show print type typedefs
15814 This command shows the current setting of typedef display when
15817 @kindex info address
15818 @cindex address of a symbol
15819 @item info address @var{symbol}
15820 Describe where the data for @var{symbol} is stored. For a register
15821 variable, this says which register it is kept in. For a non-register
15822 local variable, this prints the stack-frame offset at which the variable
15825 Note the contrast with @samp{print &@var{symbol}}, which does not work
15826 at all for a register variable, and for a stack local variable prints
15827 the exact address of the current instantiation of the variable.
15829 @kindex info symbol
15830 @cindex symbol from address
15831 @cindex closest symbol and offset for an address
15832 @item info symbol @var{addr}
15833 Print the name of a symbol which is stored at the address @var{addr}.
15834 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
15835 nearest symbol and an offset from it:
15838 (@value{GDBP}) info symbol 0x54320
15839 _initialize_vx + 396 in section .text
15843 This is the opposite of the @code{info address} command. You can use
15844 it to find out the name of a variable or a function given its address.
15846 For dynamically linked executables, the name of executable or shared
15847 library containing the symbol is also printed:
15850 (@value{GDBP}) info symbol 0x400225
15851 _start + 5 in section .text of /tmp/a.out
15852 (@value{GDBP}) info symbol 0x2aaaac2811cf
15853 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
15857 @item whatis[/@var{flags}] [@var{arg}]
15858 Print the data type of @var{arg}, which can be either an expression
15859 or a name of a data type. With no argument, print the data type of
15860 @code{$}, the last value in the value history.
15862 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
15863 is not actually evaluated, and any side-effecting operations (such as
15864 assignments or function calls) inside it do not take place.
15866 If @var{arg} is a variable or an expression, @code{whatis} prints its
15867 literal type as it is used in the source code. If the type was
15868 defined using a @code{typedef}, @code{whatis} will @emph{not} print
15869 the data type underlying the @code{typedef}. If the type of the
15870 variable or the expression is a compound data type, such as
15871 @code{struct} or @code{class}, @code{whatis} never prints their
15872 fields or methods. It just prints the @code{struct}/@code{class}
15873 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
15874 such a compound data type, use @code{ptype}.
15876 If @var{arg} is a type name that was defined using @code{typedef},
15877 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
15878 Unrolling means that @code{whatis} will show the underlying type used
15879 in the @code{typedef} declaration of @var{arg}. However, if that
15880 underlying type is also a @code{typedef}, @code{whatis} will not
15883 For C code, the type names may also have the form @samp{class
15884 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
15885 @var{union-tag}} or @samp{enum @var{enum-tag}}.
15887 @var{flags} can be used to modify how the type is displayed.
15888 Available flags are:
15892 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
15893 parameters and typedefs defined in a class when printing the class'
15894 members. The @code{/r} flag disables this.
15897 Do not print methods defined in the class.
15900 Print methods defined in the class. This is the default, but the flag
15901 exists in case you change the default with @command{set print type methods}.
15904 Do not print typedefs defined in the class. Note that this controls
15905 whether the typedef definition itself is printed, not whether typedef
15906 names are substituted when printing other types.
15909 Print typedefs defined in the class. This is the default, but the flag
15910 exists in case you change the default with @command{set print type typedefs}.
15914 @item ptype[/@var{flags}] [@var{arg}]
15915 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
15916 detailed description of the type, instead of just the name of the type.
15917 @xref{Expressions, ,Expressions}.
15919 Contrary to @code{whatis}, @code{ptype} always unrolls any
15920 @code{typedef}s in its argument declaration, whether the argument is
15921 a variable, expression, or a data type. This means that @code{ptype}
15922 of a variable or an expression will not print literally its type as
15923 present in the source code---use @code{whatis} for that. @code{typedef}s at
15924 the pointer or reference targets are also unrolled. Only @code{typedef}s of
15925 fields, methods and inner @code{class typedef}s of @code{struct}s,
15926 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
15928 For example, for this variable declaration:
15931 typedef double real_t;
15932 struct complex @{ real_t real; double imag; @};
15933 typedef struct complex complex_t;
15935 real_t *real_pointer_var;
15939 the two commands give this output:
15943 (@value{GDBP}) whatis var
15945 (@value{GDBP}) ptype var
15946 type = struct complex @{
15950 (@value{GDBP}) whatis complex_t
15951 type = struct complex
15952 (@value{GDBP}) whatis struct complex
15953 type = struct complex
15954 (@value{GDBP}) ptype struct complex
15955 type = struct complex @{
15959 (@value{GDBP}) whatis real_pointer_var
15961 (@value{GDBP}) ptype real_pointer_var
15967 As with @code{whatis}, using @code{ptype} without an argument refers to
15968 the type of @code{$}, the last value in the value history.
15970 @cindex incomplete type
15971 Sometimes, programs use opaque data types or incomplete specifications
15972 of complex data structure. If the debug information included in the
15973 program does not allow @value{GDBN} to display a full declaration of
15974 the data type, it will say @samp{<incomplete type>}. For example,
15975 given these declarations:
15979 struct foo *fooptr;
15983 but no definition for @code{struct foo} itself, @value{GDBN} will say:
15986 (@value{GDBP}) ptype foo
15987 $1 = <incomplete type>
15991 ``Incomplete type'' is C terminology for data types that are not
15992 completely specified.
15995 @item info types @var{regexp}
15997 Print a brief description of all types whose names match the regular
15998 expression @var{regexp} (or all types in your program, if you supply
15999 no argument). Each complete typename is matched as though it were a
16000 complete line; thus, @samp{i type value} gives information on all
16001 types in your program whose names include the string @code{value}, but
16002 @samp{i type ^value$} gives information only on types whose complete
16003 name is @code{value}.
16005 This command differs from @code{ptype} in two ways: first, like
16006 @code{whatis}, it does not print a detailed description; second, it
16007 lists all source files where a type is defined.
16009 @kindex info type-printers
16010 @item info type-printers
16011 Versions of @value{GDBN} that ship with Python scripting enabled may
16012 have ``type printers'' available. When using @command{ptype} or
16013 @command{whatis}, these printers are consulted when the name of a type
16014 is needed. @xref{Type Printing API}, for more information on writing
16017 @code{info type-printers} displays all the available type printers.
16019 @kindex enable type-printer
16020 @kindex disable type-printer
16021 @item enable type-printer @var{name}@dots{}
16022 @item disable type-printer @var{name}@dots{}
16023 These commands can be used to enable or disable type printers.
16026 @cindex local variables
16027 @item info scope @var{location}
16028 List all the variables local to a particular scope. This command
16029 accepts a @var{location} argument---a function name, a source line, or
16030 an address preceded by a @samp{*}, and prints all the variables local
16031 to the scope defined by that location. (@xref{Specify Location}, for
16032 details about supported forms of @var{location}.) For example:
16035 (@value{GDBP}) @b{info scope command_line_handler}
16036 Scope for command_line_handler:
16037 Symbol rl is an argument at stack/frame offset 8, length 4.
16038 Symbol linebuffer is in static storage at address 0x150a18, length 4.
16039 Symbol linelength is in static storage at address 0x150a1c, length 4.
16040 Symbol p is a local variable in register $esi, length 4.
16041 Symbol p1 is a local variable in register $ebx, length 4.
16042 Symbol nline is a local variable in register $edx, length 4.
16043 Symbol repeat is a local variable at frame offset -8, length 4.
16047 This command is especially useful for determining what data to collect
16048 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
16051 @kindex info source
16053 Show information about the current source file---that is, the source file for
16054 the function containing the current point of execution:
16057 the name of the source file, and the directory containing it,
16059 the directory it was compiled in,
16061 its length, in lines,
16063 which programming language it is written in,
16065 whether the executable includes debugging information for that file, and
16066 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
16068 whether the debugging information includes information about
16069 preprocessor macros.
16073 @kindex info sources
16075 Print the names of all source files in your program for which there is
16076 debugging information, organized into two lists: files whose symbols
16077 have already been read, and files whose symbols will be read when needed.
16079 @kindex info functions
16080 @item info functions
16081 Print the names and data types of all defined functions.
16083 @item info functions @var{regexp}
16084 Print the names and data types of all defined functions
16085 whose names contain a match for regular expression @var{regexp}.
16086 Thus, @samp{info fun step} finds all functions whose names
16087 include @code{step}; @samp{info fun ^step} finds those whose names
16088 start with @code{step}. If a function name contains characters
16089 that conflict with the regular expression language (e.g.@:
16090 @samp{operator*()}), they may be quoted with a backslash.
16092 @kindex info variables
16093 @item info variables
16094 Print the names and data types of all variables that are defined
16095 outside of functions (i.e.@: excluding local variables).
16097 @item info variables @var{regexp}
16098 Print the names and data types of all variables (except for local
16099 variables) whose names contain a match for regular expression
16102 @kindex info classes
16103 @cindex Objective-C, classes and selectors
16105 @itemx info classes @var{regexp}
16106 Display all Objective-C classes in your program, or
16107 (with the @var{regexp} argument) all those matching a particular regular
16110 @kindex info selectors
16111 @item info selectors
16112 @itemx info selectors @var{regexp}
16113 Display all Objective-C selectors in your program, or
16114 (with the @var{regexp} argument) all those matching a particular regular
16118 This was never implemented.
16119 @kindex info methods
16121 @itemx info methods @var{regexp}
16122 The @code{info methods} command permits the user to examine all defined
16123 methods within C@t{++} program, or (with the @var{regexp} argument) a
16124 specific set of methods found in the various C@t{++} classes. Many
16125 C@t{++} classes provide a large number of methods. Thus, the output
16126 from the @code{ptype} command can be overwhelming and hard to use. The
16127 @code{info-methods} command filters the methods, printing only those
16128 which match the regular-expression @var{regexp}.
16131 @cindex opaque data types
16132 @kindex set opaque-type-resolution
16133 @item set opaque-type-resolution on
16134 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
16135 declared as a pointer to a @code{struct}, @code{class}, or
16136 @code{union}---for example, @code{struct MyType *}---that is used in one
16137 source file although the full declaration of @code{struct MyType} is in
16138 another source file. The default is on.
16140 A change in the setting of this subcommand will not take effect until
16141 the next time symbols for a file are loaded.
16143 @item set opaque-type-resolution off
16144 Tell @value{GDBN} not to resolve opaque types. In this case, the type
16145 is printed as follows:
16147 @{<no data fields>@}
16150 @kindex show opaque-type-resolution
16151 @item show opaque-type-resolution
16152 Show whether opaque types are resolved or not.
16154 @kindex maint print symbols
16155 @cindex symbol dump
16156 @kindex maint print psymbols
16157 @cindex partial symbol dump
16158 @kindex maint print msymbols
16159 @cindex minimal symbol dump
16160 @item maint print symbols @var{filename}
16161 @itemx maint print psymbols @var{filename}
16162 @itemx maint print msymbols @var{filename}
16163 Write a dump of debugging symbol data into the file @var{filename}.
16164 These commands are used to debug the @value{GDBN} symbol-reading code. Only
16165 symbols with debugging data are included. If you use @samp{maint print
16166 symbols}, @value{GDBN} includes all the symbols for which it has already
16167 collected full details: that is, @var{filename} reflects symbols for
16168 only those files whose symbols @value{GDBN} has read. You can use the
16169 command @code{info sources} to find out which files these are. If you
16170 use @samp{maint print psymbols} instead, the dump shows information about
16171 symbols that @value{GDBN} only knows partially---that is, symbols defined in
16172 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
16173 @samp{maint print msymbols} dumps just the minimal symbol information
16174 required for each object file from which @value{GDBN} has read some symbols.
16175 @xref{Files, ,Commands to Specify Files}, for a discussion of how
16176 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
16178 @kindex maint info symtabs
16179 @kindex maint info psymtabs
16180 @cindex listing @value{GDBN}'s internal symbol tables
16181 @cindex symbol tables, listing @value{GDBN}'s internal
16182 @cindex full symbol tables, listing @value{GDBN}'s internal
16183 @cindex partial symbol tables, listing @value{GDBN}'s internal
16184 @item maint info symtabs @r{[} @var{regexp} @r{]}
16185 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
16187 List the @code{struct symtab} or @code{struct partial_symtab}
16188 structures whose names match @var{regexp}. If @var{regexp} is not
16189 given, list them all. The output includes expressions which you can
16190 copy into a @value{GDBN} debugging this one to examine a particular
16191 structure in more detail. For example:
16194 (@value{GDBP}) maint info psymtabs dwarf2read
16195 @{ objfile /home/gnu/build/gdb/gdb
16196 ((struct objfile *) 0x82e69d0)
16197 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
16198 ((struct partial_symtab *) 0x8474b10)
16201 text addresses 0x814d3c8 -- 0x8158074
16202 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
16203 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
16204 dependencies (none)
16207 (@value{GDBP}) maint info symtabs
16211 We see that there is one partial symbol table whose filename contains
16212 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
16213 and we see that @value{GDBN} has not read in any symtabs yet at all.
16214 If we set a breakpoint on a function, that will cause @value{GDBN} to
16215 read the symtab for the compilation unit containing that function:
16218 (@value{GDBP}) break dwarf2_psymtab_to_symtab
16219 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
16221 (@value{GDBP}) maint info symtabs
16222 @{ objfile /home/gnu/build/gdb/gdb
16223 ((struct objfile *) 0x82e69d0)
16224 @{ symtab /home/gnu/src/gdb/dwarf2read.c
16225 ((struct symtab *) 0x86c1f38)
16228 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
16229 linetable ((struct linetable *) 0x8370fa0)
16230 debugformat DWARF 2
16239 @chapter Altering Execution
16241 Once you think you have found an error in your program, you might want to
16242 find out for certain whether correcting the apparent error would lead to
16243 correct results in the rest of the run. You can find the answer by
16244 experiment, using the @value{GDBN} features for altering execution of the
16247 For example, you can store new values into variables or memory
16248 locations, give your program a signal, restart it at a different
16249 address, or even return prematurely from a function.
16252 * Assignment:: Assignment to variables
16253 * Jumping:: Continuing at a different address
16254 * Signaling:: Giving your program a signal
16255 * Returning:: Returning from a function
16256 * Calling:: Calling your program's functions
16257 * Patching:: Patching your program
16261 @section Assignment to Variables
16264 @cindex setting variables
16265 To alter the value of a variable, evaluate an assignment expression.
16266 @xref{Expressions, ,Expressions}. For example,
16273 stores the value 4 into the variable @code{x}, and then prints the
16274 value of the assignment expression (which is 4).
16275 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
16276 information on operators in supported languages.
16278 @kindex set variable
16279 @cindex variables, setting
16280 If you are not interested in seeing the value of the assignment, use the
16281 @code{set} command instead of the @code{print} command. @code{set} is
16282 really the same as @code{print} except that the expression's value is
16283 not printed and is not put in the value history (@pxref{Value History,
16284 ,Value History}). The expression is evaluated only for its effects.
16286 If the beginning of the argument string of the @code{set} command
16287 appears identical to a @code{set} subcommand, use the @code{set
16288 variable} command instead of just @code{set}. This command is identical
16289 to @code{set} except for its lack of subcommands. For example, if your
16290 program has a variable @code{width}, you get an error if you try to set
16291 a new value with just @samp{set width=13}, because @value{GDBN} has the
16292 command @code{set width}:
16295 (@value{GDBP}) whatis width
16297 (@value{GDBP}) p width
16299 (@value{GDBP}) set width=47
16300 Invalid syntax in expression.
16304 The invalid expression, of course, is @samp{=47}. In
16305 order to actually set the program's variable @code{width}, use
16308 (@value{GDBP}) set var width=47
16311 Because the @code{set} command has many subcommands that can conflict
16312 with the names of program variables, it is a good idea to use the
16313 @code{set variable} command instead of just @code{set}. For example, if
16314 your program has a variable @code{g}, you run into problems if you try
16315 to set a new value with just @samp{set g=4}, because @value{GDBN} has
16316 the command @code{set gnutarget}, abbreviated @code{set g}:
16320 (@value{GDBP}) whatis g
16324 (@value{GDBP}) set g=4
16328 The program being debugged has been started already.
16329 Start it from the beginning? (y or n) y
16330 Starting program: /home/smith/cc_progs/a.out
16331 "/home/smith/cc_progs/a.out": can't open to read symbols:
16332 Invalid bfd target.
16333 (@value{GDBP}) show g
16334 The current BFD target is "=4".
16339 The program variable @code{g} did not change, and you silently set the
16340 @code{gnutarget} to an invalid value. In order to set the variable
16344 (@value{GDBP}) set var g=4
16347 @value{GDBN} allows more implicit conversions in assignments than C; you can
16348 freely store an integer value into a pointer variable or vice versa,
16349 and you can convert any structure to any other structure that is the
16350 same length or shorter.
16351 @comment FIXME: how do structs align/pad in these conversions?
16352 @comment /doc@cygnus.com 18dec1990
16354 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
16355 construct to generate a value of specified type at a specified address
16356 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
16357 to memory location @code{0x83040} as an integer (which implies a certain size
16358 and representation in memory), and
16361 set @{int@}0x83040 = 4
16365 stores the value 4 into that memory location.
16368 @section Continuing at a Different Address
16370 Ordinarily, when you continue your program, you do so at the place where
16371 it stopped, with the @code{continue} command. You can instead continue at
16372 an address of your own choosing, with the following commands:
16376 @kindex j @r{(@code{jump})}
16377 @item jump @var{linespec}
16378 @itemx j @var{linespec}
16379 @itemx jump @var{location}
16380 @itemx j @var{location}
16381 Resume execution at line @var{linespec} or at address given by
16382 @var{location}. Execution stops again immediately if there is a
16383 breakpoint there. @xref{Specify Location}, for a description of the
16384 different forms of @var{linespec} and @var{location}. It is common
16385 practice to use the @code{tbreak} command in conjunction with
16386 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
16388 The @code{jump} command does not change the current stack frame, or
16389 the stack pointer, or the contents of any memory location or any
16390 register other than the program counter. If line @var{linespec} is in
16391 a different function from the one currently executing, the results may
16392 be bizarre if the two functions expect different patterns of arguments or
16393 of local variables. For this reason, the @code{jump} command requests
16394 confirmation if the specified line is not in the function currently
16395 executing. However, even bizarre results are predictable if you are
16396 well acquainted with the machine-language code of your program.
16399 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
16400 On many systems, you can get much the same effect as the @code{jump}
16401 command by storing a new value into the register @code{$pc}. The
16402 difference is that this does not start your program running; it only
16403 changes the address of where it @emph{will} run when you continue. For
16411 makes the next @code{continue} command or stepping command execute at
16412 address @code{0x485}, rather than at the address where your program stopped.
16413 @xref{Continuing and Stepping, ,Continuing and Stepping}.
16415 The most common occasion to use the @code{jump} command is to back
16416 up---perhaps with more breakpoints set---over a portion of a program
16417 that has already executed, in order to examine its execution in more
16422 @section Giving your Program a Signal
16423 @cindex deliver a signal to a program
16427 @item signal @var{signal}
16428 Resume execution where your program stopped, but immediately give it the
16429 signal @var{signal}. @var{signal} can be the name or the number of a
16430 signal. For example, on many systems @code{signal 2} and @code{signal
16431 SIGINT} are both ways of sending an interrupt signal.
16433 Alternatively, if @var{signal} is zero, continue execution without
16434 giving a signal. This is useful when your program stopped on account of
16435 a signal and would ordinarily see the signal when resumed with the
16436 @code{continue} command; @samp{signal 0} causes it to resume without a
16439 @code{signal} does not repeat when you press @key{RET} a second time
16440 after executing the command.
16444 Invoking the @code{signal} command is not the same as invoking the
16445 @code{kill} utility from the shell. Sending a signal with @code{kill}
16446 causes @value{GDBN} to decide what to do with the signal depending on
16447 the signal handling tables (@pxref{Signals}). The @code{signal} command
16448 passes the signal directly to your program.
16452 @section Returning from a Function
16455 @cindex returning from a function
16458 @itemx return @var{expression}
16459 You can cancel execution of a function call with the @code{return}
16460 command. If you give an
16461 @var{expression} argument, its value is used as the function's return
16465 When you use @code{return}, @value{GDBN} discards the selected stack frame
16466 (and all frames within it). You can think of this as making the
16467 discarded frame return prematurely. If you wish to specify a value to
16468 be returned, give that value as the argument to @code{return}.
16470 This pops the selected stack frame (@pxref{Selection, ,Selecting a
16471 Frame}), and any other frames inside of it, leaving its caller as the
16472 innermost remaining frame. That frame becomes selected. The
16473 specified value is stored in the registers used for returning values
16476 The @code{return} command does not resume execution; it leaves the
16477 program stopped in the state that would exist if the function had just
16478 returned. In contrast, the @code{finish} command (@pxref{Continuing
16479 and Stepping, ,Continuing and Stepping}) resumes execution until the
16480 selected stack frame returns naturally.
16482 @value{GDBN} needs to know how the @var{expression} argument should be set for
16483 the inferior. The concrete registers assignment depends on the OS ABI and the
16484 type being returned by the selected stack frame. For example it is common for
16485 OS ABI to return floating point values in FPU registers while integer values in
16486 CPU registers. Still some ABIs return even floating point values in CPU
16487 registers. Larger integer widths (such as @code{long long int}) also have
16488 specific placement rules. @value{GDBN} already knows the OS ABI from its
16489 current target so it needs to find out also the type being returned to make the
16490 assignment into the right register(s).
16492 Normally, the selected stack frame has debug info. @value{GDBN} will always
16493 use the debug info instead of the implicit type of @var{expression} when the
16494 debug info is available. For example, if you type @kbd{return -1}, and the
16495 function in the current stack frame is declared to return a @code{long long
16496 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
16497 into a @code{long long int}:
16500 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
16502 (@value{GDBP}) return -1
16503 Make func return now? (y or n) y
16504 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
16505 43 printf ("result=%lld\n", func ());
16509 However, if the selected stack frame does not have a debug info, e.g., if the
16510 function was compiled without debug info, @value{GDBN} has to find out the type
16511 to return from user. Specifying a different type by mistake may set the value
16512 in different inferior registers than the caller code expects. For example,
16513 typing @kbd{return -1} with its implicit type @code{int} would set only a part
16514 of a @code{long long int} result for a debug info less function (on 32-bit
16515 architectures). Therefore the user is required to specify the return type by
16516 an appropriate cast explicitly:
16519 Breakpoint 2, 0x0040050b in func ()
16520 (@value{GDBP}) return -1
16521 Return value type not available for selected stack frame.
16522 Please use an explicit cast of the value to return.
16523 (@value{GDBP}) return (long long int) -1
16524 Make selected stack frame return now? (y or n) y
16525 #0 0x00400526 in main ()
16530 @section Calling Program Functions
16533 @cindex calling functions
16534 @cindex inferior functions, calling
16535 @item print @var{expr}
16536 Evaluate the expression @var{expr} and display the resulting value.
16537 @var{expr} may include calls to functions in the program being
16541 @item call @var{expr}
16542 Evaluate the expression @var{expr} without displaying @code{void}
16545 You can use this variant of the @code{print} command if you want to
16546 execute a function from your program that does not return anything
16547 (a.k.a.@: @dfn{a void function}), but without cluttering the output
16548 with @code{void} returned values that @value{GDBN} will otherwise
16549 print. If the result is not void, it is printed and saved in the
16553 It is possible for the function you call via the @code{print} or
16554 @code{call} command to generate a signal (e.g., if there's a bug in
16555 the function, or if you passed it incorrect arguments). What happens
16556 in that case is controlled by the @code{set unwindonsignal} command.
16558 Similarly, with a C@t{++} program it is possible for the function you
16559 call via the @code{print} or @code{call} command to generate an
16560 exception that is not handled due to the constraints of the dummy
16561 frame. In this case, any exception that is raised in the frame, but has
16562 an out-of-frame exception handler will not be found. GDB builds a
16563 dummy-frame for the inferior function call, and the unwinder cannot
16564 seek for exception handlers outside of this dummy-frame. What happens
16565 in that case is controlled by the
16566 @code{set unwind-on-terminating-exception} command.
16569 @item set unwindonsignal
16570 @kindex set unwindonsignal
16571 @cindex unwind stack in called functions
16572 @cindex call dummy stack unwinding
16573 Set unwinding of the stack if a signal is received while in a function
16574 that @value{GDBN} called in the program being debugged. If set to on,
16575 @value{GDBN} unwinds the stack it created for the call and restores
16576 the context to what it was before the call. If set to off (the
16577 default), @value{GDBN} stops in the frame where the signal was
16580 @item show unwindonsignal
16581 @kindex show unwindonsignal
16582 Show the current setting of stack unwinding in the functions called by
16585 @item set unwind-on-terminating-exception
16586 @kindex set unwind-on-terminating-exception
16587 @cindex unwind stack in called functions with unhandled exceptions
16588 @cindex call dummy stack unwinding on unhandled exception.
16589 Set unwinding of the stack if a C@t{++} exception is raised, but left
16590 unhandled while in a function that @value{GDBN} called in the program being
16591 debugged. If set to on (the default), @value{GDBN} unwinds the stack
16592 it created for the call and restores the context to what it was before
16593 the call. If set to off, @value{GDBN} the exception is delivered to
16594 the default C@t{++} exception handler and the inferior terminated.
16596 @item show unwind-on-terminating-exception
16597 @kindex show unwind-on-terminating-exception
16598 Show the current setting of stack unwinding in the functions called by
16603 @cindex weak alias functions
16604 Sometimes, a function you wish to call is actually a @dfn{weak alias}
16605 for another function. In such case, @value{GDBN} might not pick up
16606 the type information, including the types of the function arguments,
16607 which causes @value{GDBN} to call the inferior function incorrectly.
16608 As a result, the called function will function erroneously and may
16609 even crash. A solution to that is to use the name of the aliased
16613 @section Patching Programs
16615 @cindex patching binaries
16616 @cindex writing into executables
16617 @cindex writing into corefiles
16619 By default, @value{GDBN} opens the file containing your program's
16620 executable code (or the corefile) read-only. This prevents accidental
16621 alterations to machine code; but it also prevents you from intentionally
16622 patching your program's binary.
16624 If you'd like to be able to patch the binary, you can specify that
16625 explicitly with the @code{set write} command. For example, you might
16626 want to turn on internal debugging flags, or even to make emergency
16632 @itemx set write off
16633 If you specify @samp{set write on}, @value{GDBN} opens executable and
16634 core files for both reading and writing; if you specify @kbd{set write
16635 off} (the default), @value{GDBN} opens them read-only.
16637 If you have already loaded a file, you must load it again (using the
16638 @code{exec-file} or @code{core-file} command) after changing @code{set
16639 write}, for your new setting to take effect.
16643 Display whether executable files and core files are opened for writing
16644 as well as reading.
16648 @chapter @value{GDBN} Files
16650 @value{GDBN} needs to know the file name of the program to be debugged,
16651 both in order to read its symbol table and in order to start your
16652 program. To debug a core dump of a previous run, you must also tell
16653 @value{GDBN} the name of the core dump file.
16656 * Files:: Commands to specify files
16657 * Separate Debug Files:: Debugging information in separate files
16658 * MiniDebugInfo:: Debugging information in a special section
16659 * Index Files:: Index files speed up GDB
16660 * Symbol Errors:: Errors reading symbol files
16661 * Data Files:: GDB data files
16665 @section Commands to Specify Files
16667 @cindex symbol table
16668 @cindex core dump file
16670 You may want to specify executable and core dump file names. The usual
16671 way to do this is at start-up time, using the arguments to
16672 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
16673 Out of @value{GDBN}}).
16675 Occasionally it is necessary to change to a different file during a
16676 @value{GDBN} session. Or you may run @value{GDBN} and forget to
16677 specify a file you want to use. Or you are debugging a remote target
16678 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
16679 Program}). In these situations the @value{GDBN} commands to specify
16680 new files are useful.
16683 @cindex executable file
16685 @item file @var{filename}
16686 Use @var{filename} as the program to be debugged. It is read for its
16687 symbols and for the contents of pure memory. It is also the program
16688 executed when you use the @code{run} command. If you do not specify a
16689 directory and the file is not found in the @value{GDBN} working directory,
16690 @value{GDBN} uses the environment variable @code{PATH} as a list of
16691 directories to search, just as the shell does when looking for a program
16692 to run. You can change the value of this variable, for both @value{GDBN}
16693 and your program, using the @code{path} command.
16695 @cindex unlinked object files
16696 @cindex patching object files
16697 You can load unlinked object @file{.o} files into @value{GDBN} using
16698 the @code{file} command. You will not be able to ``run'' an object
16699 file, but you can disassemble functions and inspect variables. Also,
16700 if the underlying BFD functionality supports it, you could use
16701 @kbd{gdb -write} to patch object files using this technique. Note
16702 that @value{GDBN} can neither interpret nor modify relocations in this
16703 case, so branches and some initialized variables will appear to go to
16704 the wrong place. But this feature is still handy from time to time.
16707 @code{file} with no argument makes @value{GDBN} discard any information it
16708 has on both executable file and the symbol table.
16711 @item exec-file @r{[} @var{filename} @r{]}
16712 Specify that the program to be run (but not the symbol table) is found
16713 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
16714 if necessary to locate your program. Omitting @var{filename} means to
16715 discard information on the executable file.
16717 @kindex symbol-file
16718 @item symbol-file @r{[} @var{filename} @r{]}
16719 Read symbol table information from file @var{filename}. @code{PATH} is
16720 searched when necessary. Use the @code{file} command to get both symbol
16721 table and program to run from the same file.
16723 @code{symbol-file} with no argument clears out @value{GDBN} information on your
16724 program's symbol table.
16726 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
16727 some breakpoints and auto-display expressions. This is because they may
16728 contain pointers to the internal data recording symbols and data types,
16729 which are part of the old symbol table data being discarded inside
16732 @code{symbol-file} does not repeat if you press @key{RET} again after
16735 When @value{GDBN} is configured for a particular environment, it
16736 understands debugging information in whatever format is the standard
16737 generated for that environment; you may use either a @sc{gnu} compiler, or
16738 other compilers that adhere to the local conventions.
16739 Best results are usually obtained from @sc{gnu} compilers; for example,
16740 using @code{@value{NGCC}} you can generate debugging information for
16743 For most kinds of object files, with the exception of old SVR3 systems
16744 using COFF, the @code{symbol-file} command does not normally read the
16745 symbol table in full right away. Instead, it scans the symbol table
16746 quickly to find which source files and which symbols are present. The
16747 details are read later, one source file at a time, as they are needed.
16749 The purpose of this two-stage reading strategy is to make @value{GDBN}
16750 start up faster. For the most part, it is invisible except for
16751 occasional pauses while the symbol table details for a particular source
16752 file are being read. (The @code{set verbose} command can turn these
16753 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
16754 Warnings and Messages}.)
16756 We have not implemented the two-stage strategy for COFF yet. When the
16757 symbol table is stored in COFF format, @code{symbol-file} reads the
16758 symbol table data in full right away. Note that ``stabs-in-COFF''
16759 still does the two-stage strategy, since the debug info is actually
16763 @cindex reading symbols immediately
16764 @cindex symbols, reading immediately
16765 @item symbol-file @r{[} -readnow @r{]} @var{filename}
16766 @itemx file @r{[} -readnow @r{]} @var{filename}
16767 You can override the @value{GDBN} two-stage strategy for reading symbol
16768 tables by using the @samp{-readnow} option with any of the commands that
16769 load symbol table information, if you want to be sure @value{GDBN} has the
16770 entire symbol table available.
16772 @c FIXME: for now no mention of directories, since this seems to be in
16773 @c flux. 13mar1992 status is that in theory GDB would look either in
16774 @c current dir or in same dir as myprog; but issues like competing
16775 @c GDB's, or clutter in system dirs, mean that in practice right now
16776 @c only current dir is used. FFish says maybe a special GDB hierarchy
16777 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
16781 @item core-file @r{[}@var{filename}@r{]}
16783 Specify the whereabouts of a core dump file to be used as the ``contents
16784 of memory''. Traditionally, core files contain only some parts of the
16785 address space of the process that generated them; @value{GDBN} can access the
16786 executable file itself for other parts.
16788 @code{core-file} with no argument specifies that no core file is
16791 Note that the core file is ignored when your program is actually running
16792 under @value{GDBN}. So, if you have been running your program and you
16793 wish to debug a core file instead, you must kill the subprocess in which
16794 the program is running. To do this, use the @code{kill} command
16795 (@pxref{Kill Process, ,Killing the Child Process}).
16797 @kindex add-symbol-file
16798 @cindex dynamic linking
16799 @item add-symbol-file @var{filename} @var{address}
16800 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
16801 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
16802 The @code{add-symbol-file} command reads additional symbol table
16803 information from the file @var{filename}. You would use this command
16804 when @var{filename} has been dynamically loaded (by some other means)
16805 into the program that is running. @var{address} should be the memory
16806 address at which the file has been loaded; @value{GDBN} cannot figure
16807 this out for itself. You can additionally specify an arbitrary number
16808 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
16809 section name and base address for that section. You can specify any
16810 @var{address} as an expression.
16812 The symbol table of the file @var{filename} is added to the symbol table
16813 originally read with the @code{symbol-file} command. You can use the
16814 @code{add-symbol-file} command any number of times; the new symbol data
16815 thus read is kept in addition to the old.
16817 Changes can be reverted using the command @code{remove-symbol-file}.
16819 @cindex relocatable object files, reading symbols from
16820 @cindex object files, relocatable, reading symbols from
16821 @cindex reading symbols from relocatable object files
16822 @cindex symbols, reading from relocatable object files
16823 @cindex @file{.o} files, reading symbols from
16824 Although @var{filename} is typically a shared library file, an
16825 executable file, or some other object file which has been fully
16826 relocated for loading into a process, you can also load symbolic
16827 information from relocatable @file{.o} files, as long as:
16831 the file's symbolic information refers only to linker symbols defined in
16832 that file, not to symbols defined by other object files,
16834 every section the file's symbolic information refers to has actually
16835 been loaded into the inferior, as it appears in the file, and
16837 you can determine the address at which every section was loaded, and
16838 provide these to the @code{add-symbol-file} command.
16842 Some embedded operating systems, like Sun Chorus and VxWorks, can load
16843 relocatable files into an already running program; such systems
16844 typically make the requirements above easy to meet. However, it's
16845 important to recognize that many native systems use complex link
16846 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
16847 assembly, for example) that make the requirements difficult to meet. In
16848 general, one cannot assume that using @code{add-symbol-file} to read a
16849 relocatable object file's symbolic information will have the same effect
16850 as linking the relocatable object file into the program in the normal
16853 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
16855 @kindex remove-symbol-file
16856 @item remove-symbol-file @var{filename}
16857 @item remove-symbol-file -a @var{address}
16858 Remove a symbol file added via the @code{add-symbol-file} command. The
16859 file to remove can be identified by its @var{filename} or by an @var{address}
16860 that lies within the boundaries of this symbol file in memory. Example:
16863 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
16864 add symbol table from file "/home/user/gdb/mylib.so" at
16865 .text_addr = 0x7ffff7ff9480
16867 Reading symbols from /home/user/gdb/mylib.so...done.
16868 (gdb) remove-symbol-file -a 0x7ffff7ff9480
16869 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
16874 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
16876 @kindex add-symbol-file-from-memory
16877 @cindex @code{syscall DSO}
16878 @cindex load symbols from memory
16879 @item add-symbol-file-from-memory @var{address}
16880 Load symbols from the given @var{address} in a dynamically loaded
16881 object file whose image is mapped directly into the inferior's memory.
16882 For example, the Linux kernel maps a @code{syscall DSO} into each
16883 process's address space; this DSO provides kernel-specific code for
16884 some system calls. The argument can be any expression whose
16885 evaluation yields the address of the file's shared object file header.
16886 For this command to work, you must have used @code{symbol-file} or
16887 @code{exec-file} commands in advance.
16889 @kindex add-shared-symbol-files
16891 @item add-shared-symbol-files @var{library-file}
16892 @itemx assf @var{library-file}
16893 The @code{add-shared-symbol-files} command can currently be used only
16894 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
16895 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
16896 @value{GDBN} automatically looks for shared libraries, however if
16897 @value{GDBN} does not find yours, you can invoke
16898 @code{add-shared-symbol-files}. It takes one argument: the shared
16899 library's file name. @code{assf} is a shorthand alias for
16900 @code{add-shared-symbol-files}.
16903 @item section @var{section} @var{addr}
16904 The @code{section} command changes the base address of the named
16905 @var{section} of the exec file to @var{addr}. This can be used if the
16906 exec file does not contain section addresses, (such as in the
16907 @code{a.out} format), or when the addresses specified in the file
16908 itself are wrong. Each section must be changed separately. The
16909 @code{info files} command, described below, lists all the sections and
16913 @kindex info target
16916 @code{info files} and @code{info target} are synonymous; both print the
16917 current target (@pxref{Targets, ,Specifying a Debugging Target}),
16918 including the names of the executable and core dump files currently in
16919 use by @value{GDBN}, and the files from which symbols were loaded. The
16920 command @code{help target} lists all possible targets rather than
16923 @kindex maint info sections
16924 @item maint info sections
16925 Another command that can give you extra information about program sections
16926 is @code{maint info sections}. In addition to the section information
16927 displayed by @code{info files}, this command displays the flags and file
16928 offset of each section in the executable and core dump files. In addition,
16929 @code{maint info sections} provides the following command options (which
16930 may be arbitrarily combined):
16934 Display sections for all loaded object files, including shared libraries.
16935 @item @var{sections}
16936 Display info only for named @var{sections}.
16937 @item @var{section-flags}
16938 Display info only for sections for which @var{section-flags} are true.
16939 The section flags that @value{GDBN} currently knows about are:
16942 Section will have space allocated in the process when loaded.
16943 Set for all sections except those containing debug information.
16945 Section will be loaded from the file into the child process memory.
16946 Set for pre-initialized code and data, clear for @code{.bss} sections.
16948 Section needs to be relocated before loading.
16950 Section cannot be modified by the child process.
16952 Section contains executable code only.
16954 Section contains data only (no executable code).
16956 Section will reside in ROM.
16958 Section contains data for constructor/destructor lists.
16960 Section is not empty.
16962 An instruction to the linker to not output the section.
16963 @item COFF_SHARED_LIBRARY
16964 A notification to the linker that the section contains
16965 COFF shared library information.
16967 Section contains common symbols.
16970 @kindex set trust-readonly-sections
16971 @cindex read-only sections
16972 @item set trust-readonly-sections on
16973 Tell @value{GDBN} that readonly sections in your object file
16974 really are read-only (i.e.@: that their contents will not change).
16975 In that case, @value{GDBN} can fetch values from these sections
16976 out of the object file, rather than from the target program.
16977 For some targets (notably embedded ones), this can be a significant
16978 enhancement to debugging performance.
16980 The default is off.
16982 @item set trust-readonly-sections off
16983 Tell @value{GDBN} not to trust readonly sections. This means that
16984 the contents of the section might change while the program is running,
16985 and must therefore be fetched from the target when needed.
16987 @item show trust-readonly-sections
16988 Show the current setting of trusting readonly sections.
16991 All file-specifying commands allow both absolute and relative file names
16992 as arguments. @value{GDBN} always converts the file name to an absolute file
16993 name and remembers it that way.
16995 @cindex shared libraries
16996 @anchor{Shared Libraries}
16997 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
16998 and IBM RS/6000 AIX shared libraries.
17000 On MS-Windows @value{GDBN} must be linked with the Expat library to support
17001 shared libraries. @xref{Expat}.
17003 @value{GDBN} automatically loads symbol definitions from shared libraries
17004 when you use the @code{run} command, or when you examine a core file.
17005 (Before you issue the @code{run} command, @value{GDBN} does not understand
17006 references to a function in a shared library, however---unless you are
17007 debugging a core file).
17009 On HP-UX, if the program loads a library explicitly, @value{GDBN}
17010 automatically loads the symbols at the time of the @code{shl_load} call.
17012 @c FIXME: some @value{GDBN} release may permit some refs to undef
17013 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
17014 @c FIXME...lib; check this from time to time when updating manual
17016 There are times, however, when you may wish to not automatically load
17017 symbol definitions from shared libraries, such as when they are
17018 particularly large or there are many of them.
17020 To control the automatic loading of shared library symbols, use the
17024 @kindex set auto-solib-add
17025 @item set auto-solib-add @var{mode}
17026 If @var{mode} is @code{on}, symbols from all shared object libraries
17027 will be loaded automatically when the inferior begins execution, you
17028 attach to an independently started inferior, or when the dynamic linker
17029 informs @value{GDBN} that a new library has been loaded. If @var{mode}
17030 is @code{off}, symbols must be loaded manually, using the
17031 @code{sharedlibrary} command. The default value is @code{on}.
17033 @cindex memory used for symbol tables
17034 If your program uses lots of shared libraries with debug info that
17035 takes large amounts of memory, you can decrease the @value{GDBN}
17036 memory footprint by preventing it from automatically loading the
17037 symbols from shared libraries. To that end, type @kbd{set
17038 auto-solib-add off} before running the inferior, then load each
17039 library whose debug symbols you do need with @kbd{sharedlibrary
17040 @var{regexp}}, where @var{regexp} is a regular expression that matches
17041 the libraries whose symbols you want to be loaded.
17043 @kindex show auto-solib-add
17044 @item show auto-solib-add
17045 Display the current autoloading mode.
17048 @cindex load shared library
17049 To explicitly load shared library symbols, use the @code{sharedlibrary}
17053 @kindex info sharedlibrary
17055 @item info share @var{regex}
17056 @itemx info sharedlibrary @var{regex}
17057 Print the names of the shared libraries which are currently loaded
17058 that match @var{regex}. If @var{regex} is omitted then print
17059 all shared libraries that are loaded.
17061 @kindex sharedlibrary
17063 @item sharedlibrary @var{regex}
17064 @itemx share @var{regex}
17065 Load shared object library symbols for files matching a
17066 Unix regular expression.
17067 As with files loaded automatically, it only loads shared libraries
17068 required by your program for a core file or after typing @code{run}. If
17069 @var{regex} is omitted all shared libraries required by your program are
17072 @item nosharedlibrary
17073 @kindex nosharedlibrary
17074 @cindex unload symbols from shared libraries
17075 Unload all shared object library symbols. This discards all symbols
17076 that have been loaded from all shared libraries. Symbols from shared
17077 libraries that were loaded by explicit user requests are not
17081 Sometimes you may wish that @value{GDBN} stops and gives you control
17082 when any of shared library events happen. The best way to do this is
17083 to use @code{catch load} and @code{catch unload} (@pxref{Set
17086 @value{GDBN} also supports the the @code{set stop-on-solib-events}
17087 command for this. This command exists for historical reasons. It is
17088 less useful than setting a catchpoint, because it does not allow for
17089 conditions or commands as a catchpoint does.
17092 @item set stop-on-solib-events
17093 @kindex set stop-on-solib-events
17094 This command controls whether @value{GDBN} should give you control
17095 when the dynamic linker notifies it about some shared library event.
17096 The most common event of interest is loading or unloading of a new
17099 @item show stop-on-solib-events
17100 @kindex show stop-on-solib-events
17101 Show whether @value{GDBN} stops and gives you control when shared
17102 library events happen.
17105 Shared libraries are also supported in many cross or remote debugging
17106 configurations. @value{GDBN} needs to have access to the target's libraries;
17107 this can be accomplished either by providing copies of the libraries
17108 on the host system, or by asking @value{GDBN} to automatically retrieve the
17109 libraries from the target. If copies of the target libraries are
17110 provided, they need to be the same as the target libraries, although the
17111 copies on the target can be stripped as long as the copies on the host are
17114 @cindex where to look for shared libraries
17115 For remote debugging, you need to tell @value{GDBN} where the target
17116 libraries are, so that it can load the correct copies---otherwise, it
17117 may try to load the host's libraries. @value{GDBN} has two variables
17118 to specify the search directories for target libraries.
17121 @cindex prefix for shared library file names
17122 @cindex system root, alternate
17123 @kindex set solib-absolute-prefix
17124 @kindex set sysroot
17125 @item set sysroot @var{path}
17126 Use @var{path} as the system root for the program being debugged. Any
17127 absolute shared library paths will be prefixed with @var{path}; many
17128 runtime loaders store the absolute paths to the shared library in the
17129 target program's memory. If you use @code{set sysroot} to find shared
17130 libraries, they need to be laid out in the same way that they are on
17131 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
17134 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
17135 retrieve the target libraries from the remote system. This is only
17136 supported when using a remote target that supports the @code{remote get}
17137 command (@pxref{File Transfer,,Sending files to a remote system}).
17138 The part of @var{path} following the initial @file{remote:}
17139 (if present) is used as system root prefix on the remote file system.
17140 @footnote{If you want to specify a local system root using a directory
17141 that happens to be named @file{remote:}, you need to use some equivalent
17142 variant of the name like @file{./remote:}.}
17144 For targets with an MS-DOS based filesystem, such as MS-Windows and
17145 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
17146 absolute file name with @var{path}. But first, on Unix hosts,
17147 @value{GDBN} converts all backslash directory separators into forward
17148 slashes, because the backslash is not a directory separator on Unix:
17151 c:\foo\bar.dll @result{} c:/foo/bar.dll
17154 Then, @value{GDBN} attempts prefixing the target file name with
17155 @var{path}, and looks for the resulting file name in the host file
17159 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
17162 If that does not find the shared library, @value{GDBN} tries removing
17163 the @samp{:} character from the drive spec, both for convenience, and,
17164 for the case of the host file system not supporting file names with
17168 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
17171 This makes it possible to have a system root that mirrors a target
17172 with more than one drive. E.g., you may want to setup your local
17173 copies of the target system shared libraries like so (note @samp{c} vs
17177 @file{/path/to/sysroot/c/sys/bin/foo.dll}
17178 @file{/path/to/sysroot/c/sys/bin/bar.dll}
17179 @file{/path/to/sysroot/z/sys/bin/bar.dll}
17183 and point the system root at @file{/path/to/sysroot}, so that
17184 @value{GDBN} can find the correct copies of both
17185 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
17187 If that still does not find the shared library, @value{GDBN} tries
17188 removing the whole drive spec from the target file name:
17191 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
17194 This last lookup makes it possible to not care about the drive name,
17195 if you don't want or need to.
17197 The @code{set solib-absolute-prefix} command is an alias for @code{set
17200 @cindex default system root
17201 @cindex @samp{--with-sysroot}
17202 You can set the default system root by using the configure-time
17203 @samp{--with-sysroot} option. If the system root is inside
17204 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
17205 @samp{--exec-prefix}), then the default system root will be updated
17206 automatically if the installed @value{GDBN} is moved to a new
17209 @kindex show sysroot
17211 Display the current shared library prefix.
17213 @kindex set solib-search-path
17214 @item set solib-search-path @var{path}
17215 If this variable is set, @var{path} is a colon-separated list of
17216 directories to search for shared libraries. @samp{solib-search-path}
17217 is used after @samp{sysroot} fails to locate the library, or if the
17218 path to the library is relative instead of absolute. If you want to
17219 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
17220 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
17221 finding your host's libraries. @samp{sysroot} is preferred; setting
17222 it to a nonexistent directory may interfere with automatic loading
17223 of shared library symbols.
17225 @kindex show solib-search-path
17226 @item show solib-search-path
17227 Display the current shared library search path.
17229 @cindex DOS file-name semantics of file names.
17230 @kindex set target-file-system-kind (unix|dos-based|auto)
17231 @kindex show target-file-system-kind
17232 @item set target-file-system-kind @var{kind}
17233 Set assumed file system kind for target reported file names.
17235 Shared library file names as reported by the target system may not
17236 make sense as is on the system @value{GDBN} is running on. For
17237 example, when remote debugging a target that has MS-DOS based file
17238 system semantics, from a Unix host, the target may be reporting to
17239 @value{GDBN} a list of loaded shared libraries with file names such as
17240 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
17241 drive letters, so the @samp{c:\} prefix is not normally understood as
17242 indicating an absolute file name, and neither is the backslash
17243 normally considered a directory separator character. In that case,
17244 the native file system would interpret this whole absolute file name
17245 as a relative file name with no directory components. This would make
17246 it impossible to point @value{GDBN} at a copy of the remote target's
17247 shared libraries on the host using @code{set sysroot}, and impractical
17248 with @code{set solib-search-path}. Setting
17249 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
17250 to interpret such file names similarly to how the target would, and to
17251 map them to file names valid on @value{GDBN}'s native file system
17252 semantics. The value of @var{kind} can be @code{"auto"}, in addition
17253 to one of the supported file system kinds. In that case, @value{GDBN}
17254 tries to determine the appropriate file system variant based on the
17255 current target's operating system (@pxref{ABI, ,Configuring the
17256 Current ABI}). The supported file system settings are:
17260 Instruct @value{GDBN} to assume the target file system is of Unix
17261 kind. Only file names starting the forward slash (@samp{/}) character
17262 are considered absolute, and the directory separator character is also
17266 Instruct @value{GDBN} to assume the target file system is DOS based.
17267 File names starting with either a forward slash, or a drive letter
17268 followed by a colon (e.g., @samp{c:}), are considered absolute, and
17269 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
17270 considered directory separators.
17273 Instruct @value{GDBN} to use the file system kind associated with the
17274 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
17275 This is the default.
17279 @cindex file name canonicalization
17280 @cindex base name differences
17281 When processing file names provided by the user, @value{GDBN}
17282 frequently needs to compare them to the file names recorded in the
17283 program's debug info. Normally, @value{GDBN} compares just the
17284 @dfn{base names} of the files as strings, which is reasonably fast
17285 even for very large programs. (The base name of a file is the last
17286 portion of its name, after stripping all the leading directories.)
17287 This shortcut in comparison is based upon the assumption that files
17288 cannot have more than one base name. This is usually true, but
17289 references to files that use symlinks or similar filesystem
17290 facilities violate that assumption. If your program records files
17291 using such facilities, or if you provide file names to @value{GDBN}
17292 using symlinks etc., you can set @code{basenames-may-differ} to
17293 @code{true} to instruct @value{GDBN} to completely canonicalize each
17294 pair of file names it needs to compare. This will make file-name
17295 comparisons accurate, but at a price of a significant slowdown.
17298 @item set basenames-may-differ
17299 @kindex set basenames-may-differ
17300 Set whether a source file may have multiple base names.
17302 @item show basenames-may-differ
17303 @kindex show basenames-may-differ
17304 Show whether a source file may have multiple base names.
17307 @node Separate Debug Files
17308 @section Debugging Information in Separate Files
17309 @cindex separate debugging information files
17310 @cindex debugging information in separate files
17311 @cindex @file{.debug} subdirectories
17312 @cindex debugging information directory, global
17313 @cindex global debugging information directories
17314 @cindex build ID, and separate debugging files
17315 @cindex @file{.build-id} directory
17317 @value{GDBN} allows you to put a program's debugging information in a
17318 file separate from the executable itself, in a way that allows
17319 @value{GDBN} to find and load the debugging information automatically.
17320 Since debugging information can be very large---sometimes larger
17321 than the executable code itself---some systems distribute debugging
17322 information for their executables in separate files, which users can
17323 install only when they need to debug a problem.
17325 @value{GDBN} supports two ways of specifying the separate debug info
17330 The executable contains a @dfn{debug link} that specifies the name of
17331 the separate debug info file. The separate debug file's name is
17332 usually @file{@var{executable}.debug}, where @var{executable} is the
17333 name of the corresponding executable file without leading directories
17334 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
17335 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
17336 checksum for the debug file, which @value{GDBN} uses to validate that
17337 the executable and the debug file came from the same build.
17340 The executable contains a @dfn{build ID}, a unique bit string that is
17341 also present in the corresponding debug info file. (This is supported
17342 only on some operating systems, notably those which use the ELF format
17343 for binary files and the @sc{gnu} Binutils.) For more details about
17344 this feature, see the description of the @option{--build-id}
17345 command-line option in @ref{Options, , Command Line Options, ld.info,
17346 The GNU Linker}. The debug info file's name is not specified
17347 explicitly by the build ID, but can be computed from the build ID, see
17351 Depending on the way the debug info file is specified, @value{GDBN}
17352 uses two different methods of looking for the debug file:
17356 For the ``debug link'' method, @value{GDBN} looks up the named file in
17357 the directory of the executable file, then in a subdirectory of that
17358 directory named @file{.debug}, and finally under each one of the global debug
17359 directories, in a subdirectory whose name is identical to the leading
17360 directories of the executable's absolute file name.
17363 For the ``build ID'' method, @value{GDBN} looks in the
17364 @file{.build-id} subdirectory of each one of the global debug directories for
17365 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
17366 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
17367 are the rest of the bit string. (Real build ID strings are 32 or more
17368 hex characters, not 10.)
17371 So, for example, suppose you ask @value{GDBN} to debug
17372 @file{/usr/bin/ls}, which has a debug link that specifies the
17373 file @file{ls.debug}, and a build ID whose value in hex is
17374 @code{abcdef1234}. If the list of the global debug directories includes
17375 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
17376 debug information files, in the indicated order:
17380 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
17382 @file{/usr/bin/ls.debug}
17384 @file{/usr/bin/.debug/ls.debug}
17386 @file{/usr/lib/debug/usr/bin/ls.debug}.
17389 @anchor{debug-file-directory}
17390 Global debugging info directories default to what is set by @value{GDBN}
17391 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
17392 you can also set the global debugging info directories, and view the list
17393 @value{GDBN} is currently using.
17397 @kindex set debug-file-directory
17398 @item set debug-file-directory @var{directories}
17399 Set the directories which @value{GDBN} searches for separate debugging
17400 information files to @var{directory}. Multiple path components can be set
17401 concatenating them by a path separator.
17403 @kindex show debug-file-directory
17404 @item show debug-file-directory
17405 Show the directories @value{GDBN} searches for separate debugging
17410 @cindex @code{.gnu_debuglink} sections
17411 @cindex debug link sections
17412 A debug link is a special section of the executable file named
17413 @code{.gnu_debuglink}. The section must contain:
17417 A filename, with any leading directory components removed, followed by
17420 zero to three bytes of padding, as needed to reach the next four-byte
17421 boundary within the section, and
17423 a four-byte CRC checksum, stored in the same endianness used for the
17424 executable file itself. The checksum is computed on the debugging
17425 information file's full contents by the function given below, passing
17426 zero as the @var{crc} argument.
17429 Any executable file format can carry a debug link, as long as it can
17430 contain a section named @code{.gnu_debuglink} with the contents
17433 @cindex @code{.note.gnu.build-id} sections
17434 @cindex build ID sections
17435 The build ID is a special section in the executable file (and in other
17436 ELF binary files that @value{GDBN} may consider). This section is
17437 often named @code{.note.gnu.build-id}, but that name is not mandatory.
17438 It contains unique identification for the built files---the ID remains
17439 the same across multiple builds of the same build tree. The default
17440 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
17441 content for the build ID string. The same section with an identical
17442 value is present in the original built binary with symbols, in its
17443 stripped variant, and in the separate debugging information file.
17445 The debugging information file itself should be an ordinary
17446 executable, containing a full set of linker symbols, sections, and
17447 debugging information. The sections of the debugging information file
17448 should have the same names, addresses, and sizes as the original file,
17449 but they need not contain any data---much like a @code{.bss} section
17450 in an ordinary executable.
17452 The @sc{gnu} binary utilities (Binutils) package includes the
17453 @samp{objcopy} utility that can produce
17454 the separated executable / debugging information file pairs using the
17455 following commands:
17458 @kbd{objcopy --only-keep-debug foo foo.debug}
17463 These commands remove the debugging
17464 information from the executable file @file{foo} and place it in the file
17465 @file{foo.debug}. You can use the first, second or both methods to link the
17470 The debug link method needs the following additional command to also leave
17471 behind a debug link in @file{foo}:
17474 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
17477 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
17478 a version of the @code{strip} command such that the command @kbd{strip foo -f
17479 foo.debug} has the same functionality as the two @code{objcopy} commands and
17480 the @code{ln -s} command above, together.
17483 Build ID gets embedded into the main executable using @code{ld --build-id} or
17484 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
17485 compatibility fixes for debug files separation are present in @sc{gnu} binary
17486 utilities (Binutils) package since version 2.18.
17491 @cindex CRC algorithm definition
17492 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
17493 IEEE 802.3 using the polynomial:
17495 @c TexInfo requires naked braces for multi-digit exponents for Tex
17496 @c output, but this causes HTML output to barf. HTML has to be set using
17497 @c raw commands. So we end up having to specify this equation in 2
17502 <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>
17503 + <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
17509 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
17510 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
17514 The function is computed byte at a time, taking the least
17515 significant bit of each byte first. The initial pattern
17516 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
17517 the final result is inverted to ensure trailing zeros also affect the
17520 @emph{Note:} This is the same CRC polynomial as used in handling the
17521 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
17522 , @value{GDBN} Remote Serial Protocol}). However in the
17523 case of the Remote Serial Protocol, the CRC is computed @emph{most}
17524 significant bit first, and the result is not inverted, so trailing
17525 zeros have no effect on the CRC value.
17527 To complete the description, we show below the code of the function
17528 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
17529 initially supplied @code{crc} argument means that an initial call to
17530 this function passing in zero will start computing the CRC using
17533 @kindex gnu_debuglink_crc32
17536 gnu_debuglink_crc32 (unsigned long crc,
17537 unsigned char *buf, size_t len)
17539 static const unsigned long crc32_table[256] =
17541 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
17542 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
17543 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
17544 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
17545 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
17546 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
17547 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
17548 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
17549 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
17550 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
17551 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
17552 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
17553 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
17554 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
17555 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
17556 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
17557 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
17558 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
17559 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
17560 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
17561 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
17562 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
17563 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
17564 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
17565 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
17566 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
17567 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
17568 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
17569 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
17570 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
17571 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
17572 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
17573 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
17574 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
17575 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
17576 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
17577 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
17578 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
17579 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
17580 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
17581 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
17582 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
17583 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
17584 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
17585 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
17586 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
17587 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
17588 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
17589 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
17590 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
17591 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
17594 unsigned char *end;
17596 crc = ~crc & 0xffffffff;
17597 for (end = buf + len; buf < end; ++buf)
17598 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
17599 return ~crc & 0xffffffff;
17604 This computation does not apply to the ``build ID'' method.
17606 @node MiniDebugInfo
17607 @section Debugging information in a special section
17608 @cindex separate debug sections
17609 @cindex @samp{.gnu_debugdata} section
17611 Some systems ship pre-built executables and libraries that have a
17612 special @samp{.gnu_debugdata} section. This feature is called
17613 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
17614 is used to supply extra symbols for backtraces.
17616 The intent of this section is to provide extra minimal debugging
17617 information for use in simple backtraces. It is not intended to be a
17618 replacement for full separate debugging information (@pxref{Separate
17619 Debug Files}). The example below shows the intended use; however,
17620 @value{GDBN} does not currently put restrictions on what sort of
17621 debugging information might be included in the section.
17623 @value{GDBN} has support for this extension. If the section exists,
17624 then it is used provided that no other source of debugging information
17625 can be found, and that @value{GDBN} was configured with LZMA support.
17627 This section can be easily created using @command{objcopy} and other
17628 standard utilities:
17631 # Extract the dynamic symbols from the main binary, there is no need
17632 # to also have these in the normal symbol table.
17633 nm -D @var{binary} --format=posix --defined-only \
17634 | awk '@{ print $1 @}' | sort > dynsyms
17636 # Extract all the text (i.e. function) symbols from the debuginfo.
17637 # (Note that we actually also accept "D" symbols, for the benefit
17638 # of platforms like PowerPC64 that use function descriptors.)
17639 nm @var{binary} --format=posix --defined-only \
17640 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
17643 # Keep all the function symbols not already in the dynamic symbol
17645 comm -13 dynsyms funcsyms > keep_symbols
17647 # Separate full debug info into debug binary.
17648 objcopy --only-keep-debug @var{binary} debug
17650 # Copy the full debuginfo, keeping only a minimal set of symbols and
17651 # removing some unnecessary sections.
17652 objcopy -S --remove-section .gdb_index --remove-section .comment \
17653 --keep-symbols=keep_symbols debug mini_debuginfo
17655 # Drop the full debug info from the original binary.
17656 strip --strip-all -R .comment @var{binary}
17658 # Inject the compressed data into the .gnu_debugdata section of the
17661 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
17665 @section Index Files Speed Up @value{GDBN}
17666 @cindex index files
17667 @cindex @samp{.gdb_index} section
17669 When @value{GDBN} finds a symbol file, it scans the symbols in the
17670 file in order to construct an internal symbol table. This lets most
17671 @value{GDBN} operations work quickly---at the cost of a delay early
17672 on. For large programs, this delay can be quite lengthy, so
17673 @value{GDBN} provides a way to build an index, which speeds up
17676 The index is stored as a section in the symbol file. @value{GDBN} can
17677 write the index to a file, then you can put it into the symbol file
17678 using @command{objcopy}.
17680 To create an index file, use the @code{save gdb-index} command:
17683 @item save gdb-index @var{directory}
17684 @kindex save gdb-index
17685 Create an index file for each symbol file currently known by
17686 @value{GDBN}. Each file is named after its corresponding symbol file,
17687 with @samp{.gdb-index} appended, and is written into the given
17691 Once you have created an index file you can merge it into your symbol
17692 file, here named @file{symfile}, using @command{objcopy}:
17695 $ objcopy --add-section .gdb_index=symfile.gdb-index \
17696 --set-section-flags .gdb_index=readonly symfile symfile
17699 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
17700 sections that have been deprecated. Usually they are deprecated because
17701 they are missing a new feature or have performance issues.
17702 To tell @value{GDBN} to use a deprecated index section anyway
17703 specify @code{set use-deprecated-index-sections on}.
17704 The default is @code{off}.
17705 This can speed up startup, but may result in some functionality being lost.
17706 @xref{Index Section Format}.
17708 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
17709 must be done before gdb reads the file. The following will not work:
17712 $ gdb -ex "set use-deprecated-index-sections on" <program>
17715 Instead you must do, for example,
17718 $ gdb -iex "set use-deprecated-index-sections on" <program>
17721 There are currently some limitation on indices. They only work when
17722 for DWARF debugging information, not stabs. And, they do not
17723 currently work for programs using Ada.
17725 @node Symbol Errors
17726 @section Errors Reading Symbol Files
17728 While reading a symbol file, @value{GDBN} occasionally encounters problems,
17729 such as symbol types it does not recognize, or known bugs in compiler
17730 output. By default, @value{GDBN} does not notify you of such problems, since
17731 they are relatively common and primarily of interest to people
17732 debugging compilers. If you are interested in seeing information
17733 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
17734 only one message about each such type of problem, no matter how many
17735 times the problem occurs; or you can ask @value{GDBN} to print more messages,
17736 to see how many times the problems occur, with the @code{set
17737 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
17740 The messages currently printed, and their meanings, include:
17743 @item inner block not inside outer block in @var{symbol}
17745 The symbol information shows where symbol scopes begin and end
17746 (such as at the start of a function or a block of statements). This
17747 error indicates that an inner scope block is not fully contained
17748 in its outer scope blocks.
17750 @value{GDBN} circumvents the problem by treating the inner block as if it had
17751 the same scope as the outer block. In the error message, @var{symbol}
17752 may be shown as ``@code{(don't know)}'' if the outer block is not a
17755 @item block at @var{address} out of order
17757 The symbol information for symbol scope blocks should occur in
17758 order of increasing addresses. This error indicates that it does not
17761 @value{GDBN} does not circumvent this problem, and has trouble
17762 locating symbols in the source file whose symbols it is reading. (You
17763 can often determine what source file is affected by specifying
17764 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
17767 @item bad block start address patched
17769 The symbol information for a symbol scope block has a start address
17770 smaller than the address of the preceding source line. This is known
17771 to occur in the SunOS 4.1.1 (and earlier) C compiler.
17773 @value{GDBN} circumvents the problem by treating the symbol scope block as
17774 starting on the previous source line.
17776 @item bad string table offset in symbol @var{n}
17779 Symbol number @var{n} contains a pointer into the string table which is
17780 larger than the size of the string table.
17782 @value{GDBN} circumvents the problem by considering the symbol to have the
17783 name @code{foo}, which may cause other problems if many symbols end up
17786 @item unknown symbol type @code{0x@var{nn}}
17788 The symbol information contains new data types that @value{GDBN} does
17789 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
17790 uncomprehended information, in hexadecimal.
17792 @value{GDBN} circumvents the error by ignoring this symbol information.
17793 This usually allows you to debug your program, though certain symbols
17794 are not accessible. If you encounter such a problem and feel like
17795 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
17796 on @code{complain}, then go up to the function @code{read_dbx_symtab}
17797 and examine @code{*bufp} to see the symbol.
17799 @item stub type has NULL name
17801 @value{GDBN} could not find the full definition for a struct or class.
17803 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
17804 The symbol information for a C@t{++} member function is missing some
17805 information that recent versions of the compiler should have output for
17808 @item info mismatch between compiler and debugger
17810 @value{GDBN} could not parse a type specification output by the compiler.
17815 @section GDB Data Files
17817 @cindex prefix for data files
17818 @value{GDBN} will sometimes read an auxiliary data file. These files
17819 are kept in a directory known as the @dfn{data directory}.
17821 You can set the data directory's name, and view the name @value{GDBN}
17822 is currently using.
17825 @kindex set data-directory
17826 @item set data-directory @var{directory}
17827 Set the directory which @value{GDBN} searches for auxiliary data files
17828 to @var{directory}.
17830 @kindex show data-directory
17831 @item show data-directory
17832 Show the directory @value{GDBN} searches for auxiliary data files.
17835 @cindex default data directory
17836 @cindex @samp{--with-gdb-datadir}
17837 You can set the default data directory by using the configure-time
17838 @samp{--with-gdb-datadir} option. If the data directory is inside
17839 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
17840 @samp{--exec-prefix}), then the default data directory will be updated
17841 automatically if the installed @value{GDBN} is moved to a new
17844 The data directory may also be specified with the
17845 @code{--data-directory} command line option.
17846 @xref{Mode Options}.
17849 @chapter Specifying a Debugging Target
17851 @cindex debugging target
17852 A @dfn{target} is the execution environment occupied by your program.
17854 Often, @value{GDBN} runs in the same host environment as your program;
17855 in that case, the debugging target is specified as a side effect when
17856 you use the @code{file} or @code{core} commands. When you need more
17857 flexibility---for example, running @value{GDBN} on a physically separate
17858 host, or controlling a standalone system over a serial port or a
17859 realtime system over a TCP/IP connection---you can use the @code{target}
17860 command to specify one of the target types configured for @value{GDBN}
17861 (@pxref{Target Commands, ,Commands for Managing Targets}).
17863 @cindex target architecture
17864 It is possible to build @value{GDBN} for several different @dfn{target
17865 architectures}. When @value{GDBN} is built like that, you can choose
17866 one of the available architectures with the @kbd{set architecture}
17870 @kindex set architecture
17871 @kindex show architecture
17872 @item set architecture @var{arch}
17873 This command sets the current target architecture to @var{arch}. The
17874 value of @var{arch} can be @code{"auto"}, in addition to one of the
17875 supported architectures.
17877 @item show architecture
17878 Show the current target architecture.
17880 @item set processor
17882 @kindex set processor
17883 @kindex show processor
17884 These are alias commands for, respectively, @code{set architecture}
17885 and @code{show architecture}.
17889 * Active Targets:: Active targets
17890 * Target Commands:: Commands for managing targets
17891 * Byte Order:: Choosing target byte order
17894 @node Active Targets
17895 @section Active Targets
17897 @cindex stacking targets
17898 @cindex active targets
17899 @cindex multiple targets
17901 There are multiple classes of targets such as: processes, executable files or
17902 recording sessions. Core files belong to the process class, making core file
17903 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
17904 on multiple active targets, one in each class. This allows you to (for
17905 example) start a process and inspect its activity, while still having access to
17906 the executable file after the process finishes. Or if you start process
17907 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
17908 presented a virtual layer of the recording target, while the process target
17909 remains stopped at the chronologically last point of the process execution.
17911 Use the @code{core-file} and @code{exec-file} commands to select a new core
17912 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
17913 specify as a target a process that is already running, use the @code{attach}
17914 command (@pxref{Attach, ,Debugging an Already-running Process}).
17916 @node Target Commands
17917 @section Commands for Managing Targets
17920 @item target @var{type} @var{parameters}
17921 Connects the @value{GDBN} host environment to a target machine or
17922 process. A target is typically a protocol for talking to debugging
17923 facilities. You use the argument @var{type} to specify the type or
17924 protocol of the target machine.
17926 Further @var{parameters} are interpreted by the target protocol, but
17927 typically include things like device names or host names to connect
17928 with, process numbers, and baud rates.
17930 The @code{target} command does not repeat if you press @key{RET} again
17931 after executing the command.
17933 @kindex help target
17935 Displays the names of all targets available. To display targets
17936 currently selected, use either @code{info target} or @code{info files}
17937 (@pxref{Files, ,Commands to Specify Files}).
17939 @item help target @var{name}
17940 Describe a particular target, including any parameters necessary to
17943 @kindex set gnutarget
17944 @item set gnutarget @var{args}
17945 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
17946 knows whether it is reading an @dfn{executable},
17947 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
17948 with the @code{set gnutarget} command. Unlike most @code{target} commands,
17949 with @code{gnutarget} the @code{target} refers to a program, not a machine.
17952 @emph{Warning:} To specify a file format with @code{set gnutarget},
17953 you must know the actual BFD name.
17957 @xref{Files, , Commands to Specify Files}.
17959 @kindex show gnutarget
17960 @item show gnutarget
17961 Use the @code{show gnutarget} command to display what file format
17962 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
17963 @value{GDBN} will determine the file format for each file automatically,
17964 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
17967 @cindex common targets
17968 Here are some common targets (available, or not, depending on the GDB
17973 @item target exec @var{program}
17974 @cindex executable file target
17975 An executable file. @samp{target exec @var{program}} is the same as
17976 @samp{exec-file @var{program}}.
17978 @item target core @var{filename}
17979 @cindex core dump file target
17980 A core dump file. @samp{target core @var{filename}} is the same as
17981 @samp{core-file @var{filename}}.
17983 @item target remote @var{medium}
17984 @cindex remote target
17985 A remote system connected to @value{GDBN} via a serial line or network
17986 connection. This command tells @value{GDBN} to use its own remote
17987 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
17989 For example, if you have a board connected to @file{/dev/ttya} on the
17990 machine running @value{GDBN}, you could say:
17993 target remote /dev/ttya
17996 @code{target remote} supports the @code{load} command. This is only
17997 useful if you have some other way of getting the stub to the target
17998 system, and you can put it somewhere in memory where it won't get
17999 clobbered by the download.
18001 @item target sim @r{[}@var{simargs}@r{]} @dots{}
18002 @cindex built-in simulator target
18003 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
18011 works; however, you cannot assume that a specific memory map, device
18012 drivers, or even basic I/O is available, although some simulators do
18013 provide these. For info about any processor-specific simulator details,
18014 see the appropriate section in @ref{Embedded Processors, ,Embedded
18019 Different targets are available on different configurations of @value{GDBN};
18020 your configuration may have more or fewer targets.
18022 Many remote targets require you to download the executable's code once
18023 you've successfully established a connection. You may wish to control
18024 various aspects of this process.
18029 @kindex set hash@r{, for remote monitors}
18030 @cindex hash mark while downloading
18031 This command controls whether a hash mark @samp{#} is displayed while
18032 downloading a file to the remote monitor. If on, a hash mark is
18033 displayed after each S-record is successfully downloaded to the
18037 @kindex show hash@r{, for remote monitors}
18038 Show the current status of displaying the hash mark.
18040 @item set debug monitor
18041 @kindex set debug monitor
18042 @cindex display remote monitor communications
18043 Enable or disable display of communications messages between
18044 @value{GDBN} and the remote monitor.
18046 @item show debug monitor
18047 @kindex show debug monitor
18048 Show the current status of displaying communications between
18049 @value{GDBN} and the remote monitor.
18054 @kindex load @var{filename}
18055 @item load @var{filename}
18057 Depending on what remote debugging facilities are configured into
18058 @value{GDBN}, the @code{load} command may be available. Where it exists, it
18059 is meant to make @var{filename} (an executable) available for debugging
18060 on the remote system---by downloading, or dynamic linking, for example.
18061 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
18062 the @code{add-symbol-file} command.
18064 If your @value{GDBN} does not have a @code{load} command, attempting to
18065 execute it gets the error message ``@code{You can't do that when your
18066 target is @dots{}}''
18068 The file is loaded at whatever address is specified in the executable.
18069 For some object file formats, you can specify the load address when you
18070 link the program; for other formats, like a.out, the object file format
18071 specifies a fixed address.
18072 @c FIXME! This would be a good place for an xref to the GNU linker doc.
18074 Depending on the remote side capabilities, @value{GDBN} may be able to
18075 load programs into flash memory.
18077 @code{load} does not repeat if you press @key{RET} again after using it.
18081 @section Choosing Target Byte Order
18083 @cindex choosing target byte order
18084 @cindex target byte order
18086 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
18087 offer the ability to run either big-endian or little-endian byte
18088 orders. Usually the executable or symbol will include a bit to
18089 designate the endian-ness, and you will not need to worry about
18090 which to use. However, you may still find it useful to adjust
18091 @value{GDBN}'s idea of processor endian-ness manually.
18095 @item set endian big
18096 Instruct @value{GDBN} to assume the target is big-endian.
18098 @item set endian little
18099 Instruct @value{GDBN} to assume the target is little-endian.
18101 @item set endian auto
18102 Instruct @value{GDBN} to use the byte order associated with the
18106 Display @value{GDBN}'s current idea of the target byte order.
18110 Note that these commands merely adjust interpretation of symbolic
18111 data on the host, and that they have absolutely no effect on the
18115 @node Remote Debugging
18116 @chapter Debugging Remote Programs
18117 @cindex remote debugging
18119 If you are trying to debug a program running on a machine that cannot run
18120 @value{GDBN} in the usual way, it is often useful to use remote debugging.
18121 For example, you might use remote debugging on an operating system kernel,
18122 or on a small system which does not have a general purpose operating system
18123 powerful enough to run a full-featured debugger.
18125 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
18126 to make this work with particular debugging targets. In addition,
18127 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
18128 but not specific to any particular target system) which you can use if you
18129 write the remote stubs---the code that runs on the remote system to
18130 communicate with @value{GDBN}.
18132 Other remote targets may be available in your
18133 configuration of @value{GDBN}; use @code{help target} to list them.
18136 * Connecting:: Connecting to a remote target
18137 * File Transfer:: Sending files to a remote system
18138 * Server:: Using the gdbserver program
18139 * Remote Configuration:: Remote configuration
18140 * Remote Stub:: Implementing a remote stub
18144 @section Connecting to a Remote Target
18146 On the @value{GDBN} host machine, you will need an unstripped copy of
18147 your program, since @value{GDBN} needs symbol and debugging information.
18148 Start up @value{GDBN} as usual, using the name of the local copy of your
18149 program as the first argument.
18151 @cindex @code{target remote}
18152 @value{GDBN} can communicate with the target over a serial line, or
18153 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
18154 each case, @value{GDBN} uses the same protocol for debugging your
18155 program; only the medium carrying the debugging packets varies. The
18156 @code{target remote} command establishes a connection to the target.
18157 Its arguments indicate which medium to use:
18161 @item target remote @var{serial-device}
18162 @cindex serial line, @code{target remote}
18163 Use @var{serial-device} to communicate with the target. For example,
18164 to use a serial line connected to the device named @file{/dev/ttyb}:
18167 target remote /dev/ttyb
18170 If you're using a serial line, you may want to give @value{GDBN} the
18171 @samp{--baud} option, or use the @code{set serial baud} command
18172 (@pxref{Remote Configuration, set serial baud}) before the
18173 @code{target} command.
18175 @item target remote @code{@var{host}:@var{port}}
18176 @itemx target remote @code{tcp:@var{host}:@var{port}}
18177 @cindex @acronym{TCP} port, @code{target remote}
18178 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
18179 The @var{host} may be either a host name or a numeric @acronym{IP}
18180 address; @var{port} must be a decimal number. The @var{host} could be
18181 the target machine itself, if it is directly connected to the net, or
18182 it might be a terminal server which in turn has a serial line to the
18185 For example, to connect to port 2828 on a terminal server named
18189 target remote manyfarms:2828
18192 If your remote target is actually running on the same machine as your
18193 debugger session (e.g.@: a simulator for your target running on the
18194 same host), you can omit the hostname. For example, to connect to
18195 port 1234 on your local machine:
18198 target remote :1234
18202 Note that the colon is still required here.
18204 @item target remote @code{udp:@var{host}:@var{port}}
18205 @cindex @acronym{UDP} port, @code{target remote}
18206 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
18207 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
18210 target remote udp:manyfarms:2828
18213 When using a @acronym{UDP} connection for remote debugging, you should
18214 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
18215 can silently drop packets on busy or unreliable networks, which will
18216 cause havoc with your debugging session.
18218 @item target remote | @var{command}
18219 @cindex pipe, @code{target remote} to
18220 Run @var{command} in the background and communicate with it using a
18221 pipe. The @var{command} is a shell command, to be parsed and expanded
18222 by the system's command shell, @code{/bin/sh}; it should expect remote
18223 protocol packets on its standard input, and send replies on its
18224 standard output. You could use this to run a stand-alone simulator
18225 that speaks the remote debugging protocol, to make net connections
18226 using programs like @code{ssh}, or for other similar tricks.
18228 If @var{command} closes its standard output (perhaps by exiting),
18229 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
18230 program has already exited, this will have no effect.)
18234 Once the connection has been established, you can use all the usual
18235 commands to examine and change data. The remote program is already
18236 running; you can use @kbd{step} and @kbd{continue}, and you do not
18237 need to use @kbd{run}.
18239 @cindex interrupting remote programs
18240 @cindex remote programs, interrupting
18241 Whenever @value{GDBN} is waiting for the remote program, if you type the
18242 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
18243 program. This may or may not succeed, depending in part on the hardware
18244 and the serial drivers the remote system uses. If you type the
18245 interrupt character once again, @value{GDBN} displays this prompt:
18248 Interrupted while waiting for the program.
18249 Give up (and stop debugging it)? (y or n)
18252 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
18253 (If you decide you want to try again later, you can use @samp{target
18254 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
18255 goes back to waiting.
18258 @kindex detach (remote)
18260 When you have finished debugging the remote program, you can use the
18261 @code{detach} command to release it from @value{GDBN} control.
18262 Detaching from the target normally resumes its execution, but the results
18263 will depend on your particular remote stub. After the @code{detach}
18264 command, @value{GDBN} is free to connect to another target.
18268 The @code{disconnect} command behaves like @code{detach}, except that
18269 the target is generally not resumed. It will wait for @value{GDBN}
18270 (this instance or another one) to connect and continue debugging. After
18271 the @code{disconnect} command, @value{GDBN} is again free to connect to
18274 @cindex send command to remote monitor
18275 @cindex extend @value{GDBN} for remote targets
18276 @cindex add new commands for external monitor
18278 @item monitor @var{cmd}
18279 This command allows you to send arbitrary commands directly to the
18280 remote monitor. Since @value{GDBN} doesn't care about the commands it
18281 sends like this, this command is the way to extend @value{GDBN}---you
18282 can add new commands that only the external monitor will understand
18286 @node File Transfer
18287 @section Sending files to a remote system
18288 @cindex remote target, file transfer
18289 @cindex file transfer
18290 @cindex sending files to remote systems
18292 Some remote targets offer the ability to transfer files over the same
18293 connection used to communicate with @value{GDBN}. This is convenient
18294 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
18295 running @code{gdbserver} over a network interface. For other targets,
18296 e.g.@: embedded devices with only a single serial port, this may be
18297 the only way to upload or download files.
18299 Not all remote targets support these commands.
18303 @item remote put @var{hostfile} @var{targetfile}
18304 Copy file @var{hostfile} from the host system (the machine running
18305 @value{GDBN}) to @var{targetfile} on the target system.
18308 @item remote get @var{targetfile} @var{hostfile}
18309 Copy file @var{targetfile} from the target system to @var{hostfile}
18310 on the host system.
18312 @kindex remote delete
18313 @item remote delete @var{targetfile}
18314 Delete @var{targetfile} from the target system.
18319 @section Using the @code{gdbserver} Program
18322 @cindex remote connection without stubs
18323 @code{gdbserver} is a control program for Unix-like systems, which
18324 allows you to connect your program with a remote @value{GDBN} via
18325 @code{target remote}---but without linking in the usual debugging stub.
18327 @code{gdbserver} is not a complete replacement for the debugging stubs,
18328 because it requires essentially the same operating-system facilities
18329 that @value{GDBN} itself does. In fact, a system that can run
18330 @code{gdbserver} to connect to a remote @value{GDBN} could also run
18331 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
18332 because it is a much smaller program than @value{GDBN} itself. It is
18333 also easier to port than all of @value{GDBN}, so you may be able to get
18334 started more quickly on a new system by using @code{gdbserver}.
18335 Finally, if you develop code for real-time systems, you may find that
18336 the tradeoffs involved in real-time operation make it more convenient to
18337 do as much development work as possible on another system, for example
18338 by cross-compiling. You can use @code{gdbserver} to make a similar
18339 choice for debugging.
18341 @value{GDBN} and @code{gdbserver} communicate via either a serial line
18342 or a TCP connection, using the standard @value{GDBN} remote serial
18346 @emph{Warning:} @code{gdbserver} does not have any built-in security.
18347 Do not run @code{gdbserver} connected to any public network; a
18348 @value{GDBN} connection to @code{gdbserver} provides access to the
18349 target system with the same privileges as the user running
18353 @subsection Running @code{gdbserver}
18354 @cindex arguments, to @code{gdbserver}
18355 @cindex @code{gdbserver}, command-line arguments
18357 Run @code{gdbserver} on the target system. You need a copy of the
18358 program you want to debug, including any libraries it requires.
18359 @code{gdbserver} does not need your program's symbol table, so you can
18360 strip the program if necessary to save space. @value{GDBN} on the host
18361 system does all the symbol handling.
18363 To use the server, you must tell it how to communicate with @value{GDBN};
18364 the name of your program; and the arguments for your program. The usual
18368 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
18371 @var{comm} is either a device name (to use a serial line), or a TCP
18372 hostname and portnumber, or @code{-} or @code{stdio} to use
18373 stdin/stdout of @code{gdbserver}.
18374 For example, to debug Emacs with the argument
18375 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
18379 target> gdbserver /dev/com1 emacs foo.txt
18382 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
18385 To use a TCP connection instead of a serial line:
18388 target> gdbserver host:2345 emacs foo.txt
18391 The only difference from the previous example is the first argument,
18392 specifying that you are communicating with the host @value{GDBN} via
18393 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
18394 expect a TCP connection from machine @samp{host} to local TCP port 2345.
18395 (Currently, the @samp{host} part is ignored.) You can choose any number
18396 you want for the port number as long as it does not conflict with any
18397 TCP ports already in use on the target system (for example, @code{23} is
18398 reserved for @code{telnet}).@footnote{If you choose a port number that
18399 conflicts with another service, @code{gdbserver} prints an error message
18400 and exits.} You must use the same port number with the host @value{GDBN}
18401 @code{target remote} command.
18403 The @code{stdio} connection is useful when starting @code{gdbserver}
18407 (gdb) target remote | ssh -T hostname gdbserver - hello
18410 The @samp{-T} option to ssh is provided because we don't need a remote pty,
18411 and we don't want escape-character handling. Ssh does this by default when
18412 a command is provided, the flag is provided to make it explicit.
18413 You could elide it if you want to.
18415 Programs started with stdio-connected gdbserver have @file{/dev/null} for
18416 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
18417 display through a pipe connected to gdbserver.
18418 Both @code{stdout} and @code{stderr} use the same pipe.
18420 @subsubsection Attaching to a Running Program
18421 @cindex attach to a program, @code{gdbserver}
18422 @cindex @option{--attach}, @code{gdbserver} option
18424 On some targets, @code{gdbserver} can also attach to running programs.
18425 This is accomplished via the @code{--attach} argument. The syntax is:
18428 target> gdbserver --attach @var{comm} @var{pid}
18431 @var{pid} is the process ID of a currently running process. It isn't necessary
18432 to point @code{gdbserver} at a binary for the running process.
18435 You can debug processes by name instead of process ID if your target has the
18436 @code{pidof} utility:
18439 target> gdbserver --attach @var{comm} `pidof @var{program}`
18442 In case more than one copy of @var{program} is running, or @var{program}
18443 has multiple threads, most versions of @code{pidof} support the
18444 @code{-s} option to only return the first process ID.
18446 @subsubsection Multi-Process Mode for @code{gdbserver}
18447 @cindex @code{gdbserver}, multiple processes
18448 @cindex multiple processes with @code{gdbserver}
18450 When you connect to @code{gdbserver} using @code{target remote},
18451 @code{gdbserver} debugs the specified program only once. When the
18452 program exits, or you detach from it, @value{GDBN} closes the connection
18453 and @code{gdbserver} exits.
18455 If you connect using @kbd{target extended-remote}, @code{gdbserver}
18456 enters multi-process mode. When the debugged program exits, or you
18457 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
18458 though no program is running. The @code{run} and @code{attach}
18459 commands instruct @code{gdbserver} to run or attach to a new program.
18460 The @code{run} command uses @code{set remote exec-file} (@pxref{set
18461 remote exec-file}) to select the program to run. Command line
18462 arguments are supported, except for wildcard expansion and I/O
18463 redirection (@pxref{Arguments}).
18465 @cindex @option{--multi}, @code{gdbserver} option
18466 To start @code{gdbserver} without supplying an initial command to run
18467 or process ID to attach, use the @option{--multi} command line option.
18468 Then you can connect using @kbd{target extended-remote} and start
18469 the program you want to debug.
18471 In multi-process mode @code{gdbserver} does not automatically exit unless you
18472 use the option @option{--once}. You can terminate it by using
18473 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
18474 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
18475 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
18476 @option{--multi} option to @code{gdbserver} has no influence on that.
18478 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
18480 This section applies only when @code{gdbserver} is run to listen on a TCP port.
18482 @code{gdbserver} normally terminates after all of its debugged processes have
18483 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
18484 extended-remote}, @code{gdbserver} stays running even with no processes left.
18485 @value{GDBN} normally terminates the spawned debugged process on its exit,
18486 which normally also terminates @code{gdbserver} in the @kbd{target remote}
18487 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
18488 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
18489 stays running even in the @kbd{target remote} mode.
18491 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
18492 Such reconnecting is useful for features like @ref{disconnected tracing}. For
18493 completeness, at most one @value{GDBN} can be connected at a time.
18495 @cindex @option{--once}, @code{gdbserver} option
18496 By default, @code{gdbserver} keeps the listening TCP port open, so that
18497 subsequent connections are possible. However, if you start @code{gdbserver}
18498 with the @option{--once} option, it will stop listening for any further
18499 connection attempts after connecting to the first @value{GDBN} session. This
18500 means no further connections to @code{gdbserver} will be possible after the
18501 first one. It also means @code{gdbserver} will terminate after the first
18502 connection with remote @value{GDBN} has closed, even for unexpectedly closed
18503 connections and even in the @kbd{target extended-remote} mode. The
18504 @option{--once} option allows reusing the same port number for connecting to
18505 multiple instances of @code{gdbserver} running on the same host, since each
18506 instance closes its port after the first connection.
18508 @subsubsection Other Command-Line Arguments for @code{gdbserver}
18510 @cindex @option{--debug}, @code{gdbserver} option
18511 The @option{--debug} option tells @code{gdbserver} to display extra
18512 status information about the debugging process.
18513 @cindex @option{--remote-debug}, @code{gdbserver} option
18514 The @option{--remote-debug} option tells @code{gdbserver} to display
18515 remote protocol debug output. These options are intended for
18516 @code{gdbserver} development and for bug reports to the developers.
18518 @cindex @option{--wrapper}, @code{gdbserver} option
18519 The @option{--wrapper} option specifies a wrapper to launch programs
18520 for debugging. The option should be followed by the name of the
18521 wrapper, then any command-line arguments to pass to the wrapper, then
18522 @kbd{--} indicating the end of the wrapper arguments.
18524 @code{gdbserver} runs the specified wrapper program with a combined
18525 command line including the wrapper arguments, then the name of the
18526 program to debug, then any arguments to the program. The wrapper
18527 runs until it executes your program, and then @value{GDBN} gains control.
18529 You can use any program that eventually calls @code{execve} with
18530 its arguments as a wrapper. Several standard Unix utilities do
18531 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
18532 with @code{exec "$@@"} will also work.
18534 For example, you can use @code{env} to pass an environment variable to
18535 the debugged program, without setting the variable in @code{gdbserver}'s
18539 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
18542 @subsection Connecting to @code{gdbserver}
18544 Run @value{GDBN} on the host system.
18546 First make sure you have the necessary symbol files. Load symbols for
18547 your application using the @code{file} command before you connect. Use
18548 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
18549 was compiled with the correct sysroot using @code{--with-sysroot}).
18551 The symbol file and target libraries must exactly match the executable
18552 and libraries on the target, with one exception: the files on the host
18553 system should not be stripped, even if the files on the target system
18554 are. Mismatched or missing files will lead to confusing results
18555 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
18556 files may also prevent @code{gdbserver} from debugging multi-threaded
18559 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
18560 For TCP connections, you must start up @code{gdbserver} prior to using
18561 the @code{target remote} command. Otherwise you may get an error whose
18562 text depends on the host system, but which usually looks something like
18563 @samp{Connection refused}. Don't use the @code{load}
18564 command in @value{GDBN} when using @code{gdbserver}, since the program is
18565 already on the target.
18567 @subsection Monitor Commands for @code{gdbserver}
18568 @cindex monitor commands, for @code{gdbserver}
18569 @anchor{Monitor Commands for gdbserver}
18571 During a @value{GDBN} session using @code{gdbserver}, you can use the
18572 @code{monitor} command to send special requests to @code{gdbserver}.
18573 Here are the available commands.
18577 List the available monitor commands.
18579 @item monitor set debug 0
18580 @itemx monitor set debug 1
18581 Disable or enable general debugging messages.
18583 @item monitor set remote-debug 0
18584 @itemx monitor set remote-debug 1
18585 Disable or enable specific debugging messages associated with the remote
18586 protocol (@pxref{Remote Protocol}).
18588 @item monitor set libthread-db-search-path [PATH]
18589 @cindex gdbserver, search path for @code{libthread_db}
18590 When this command is issued, @var{path} is a colon-separated list of
18591 directories to search for @code{libthread_db} (@pxref{Threads,,set
18592 libthread-db-search-path}). If you omit @var{path},
18593 @samp{libthread-db-search-path} will be reset to its default value.
18595 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
18596 not supported in @code{gdbserver}.
18599 Tell gdbserver to exit immediately. This command should be followed by
18600 @code{disconnect} to close the debugging session. @code{gdbserver} will
18601 detach from any attached processes and kill any processes it created.
18602 Use @code{monitor exit} to terminate @code{gdbserver} at the end
18603 of a multi-process mode debug session.
18607 @subsection Tracepoints support in @code{gdbserver}
18608 @cindex tracepoints support in @code{gdbserver}
18610 On some targets, @code{gdbserver} supports tracepoints, fast
18611 tracepoints and static tracepoints.
18613 For fast or static tracepoints to work, a special library called the
18614 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
18615 This library is built and distributed as an integral part of
18616 @code{gdbserver}. In addition, support for static tracepoints
18617 requires building the in-process agent library with static tracepoints
18618 support. At present, the UST (LTTng Userspace Tracer,
18619 @url{http://lttng.org/ust}) tracing engine is supported. This support
18620 is automatically available if UST development headers are found in the
18621 standard include path when @code{gdbserver} is built, or if
18622 @code{gdbserver} was explicitly configured using @option{--with-ust}
18623 to point at such headers. You can explicitly disable the support
18624 using @option{--with-ust=no}.
18626 There are several ways to load the in-process agent in your program:
18629 @item Specifying it as dependency at link time
18631 You can link your program dynamically with the in-process agent
18632 library. On most systems, this is accomplished by adding
18633 @code{-linproctrace} to the link command.
18635 @item Using the system's preloading mechanisms
18637 You can force loading the in-process agent at startup time by using
18638 your system's support for preloading shared libraries. Many Unixes
18639 support the concept of preloading user defined libraries. In most
18640 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
18641 in the environment. See also the description of @code{gdbserver}'s
18642 @option{--wrapper} command line option.
18644 @item Using @value{GDBN} to force loading the agent at run time
18646 On some systems, you can force the inferior to load a shared library,
18647 by calling a dynamic loader function in the inferior that takes care
18648 of dynamically looking up and loading a shared library. On most Unix
18649 systems, the function is @code{dlopen}. You'll use the @code{call}
18650 command for that. For example:
18653 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
18656 Note that on most Unix systems, for the @code{dlopen} function to be
18657 available, the program needs to be linked with @code{-ldl}.
18660 On systems that have a userspace dynamic loader, like most Unix
18661 systems, when you connect to @code{gdbserver} using @code{target
18662 remote}, you'll find that the program is stopped at the dynamic
18663 loader's entry point, and no shared library has been loaded in the
18664 program's address space yet, including the in-process agent. In that
18665 case, before being able to use any of the fast or static tracepoints
18666 features, you need to let the loader run and load the shared
18667 libraries. The simplest way to do that is to run the program to the
18668 main procedure. E.g., if debugging a C or C@t{++} program, start
18669 @code{gdbserver} like so:
18672 $ gdbserver :9999 myprogram
18675 Start GDB and connect to @code{gdbserver} like so, and run to main:
18679 (@value{GDBP}) target remote myhost:9999
18680 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
18681 (@value{GDBP}) b main
18682 (@value{GDBP}) continue
18685 The in-process tracing agent library should now be loaded into the
18686 process; you can confirm it with the @code{info sharedlibrary}
18687 command, which will list @file{libinproctrace.so} as loaded in the
18688 process. You are now ready to install fast tracepoints, list static
18689 tracepoint markers, probe static tracepoints markers, and start
18692 @node Remote Configuration
18693 @section Remote Configuration
18696 @kindex show remote
18697 This section documents the configuration options available when
18698 debugging remote programs. For the options related to the File I/O
18699 extensions of the remote protocol, see @ref{system,
18700 system-call-allowed}.
18703 @item set remoteaddresssize @var{bits}
18704 @cindex address size for remote targets
18705 @cindex bits in remote address
18706 Set the maximum size of address in a memory packet to the specified
18707 number of bits. @value{GDBN} will mask off the address bits above
18708 that number, when it passes addresses to the remote target. The
18709 default value is the number of bits in the target's address.
18711 @item show remoteaddresssize
18712 Show the current value of remote address size in bits.
18714 @item set serial baud @var{n}
18715 @cindex baud rate for remote targets
18716 Set the baud rate for the remote serial I/O to @var{n} baud. The
18717 value is used to set the speed of the serial port used for debugging
18720 @item show serial baud
18721 Show the current speed of the remote connection.
18723 @item set remotebreak
18724 @cindex interrupt remote programs
18725 @cindex BREAK signal instead of Ctrl-C
18726 @anchor{set remotebreak}
18727 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
18728 when you type @kbd{Ctrl-c} to interrupt the program running
18729 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
18730 character instead. The default is off, since most remote systems
18731 expect to see @samp{Ctrl-C} as the interrupt signal.
18733 @item show remotebreak
18734 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
18735 interrupt the remote program.
18737 @item set remoteflow on
18738 @itemx set remoteflow off
18739 @kindex set remoteflow
18740 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
18741 on the serial port used to communicate to the remote target.
18743 @item show remoteflow
18744 @kindex show remoteflow
18745 Show the current setting of hardware flow control.
18747 @item set remotelogbase @var{base}
18748 Set the base (a.k.a.@: radix) of logging serial protocol
18749 communications to @var{base}. Supported values of @var{base} are:
18750 @code{ascii}, @code{octal}, and @code{hex}. The default is
18753 @item show remotelogbase
18754 Show the current setting of the radix for logging remote serial
18757 @item set remotelogfile @var{file}
18758 @cindex record serial communications on file
18759 Record remote serial communications on the named @var{file}. The
18760 default is not to record at all.
18762 @item show remotelogfile.
18763 Show the current setting of the file name on which to record the
18764 serial communications.
18766 @item set remotetimeout @var{num}
18767 @cindex timeout for serial communications
18768 @cindex remote timeout
18769 Set the timeout limit to wait for the remote target to respond to
18770 @var{num} seconds. The default is 2 seconds.
18772 @item show remotetimeout
18773 Show the current number of seconds to wait for the remote target
18776 @cindex limit hardware breakpoints and watchpoints
18777 @cindex remote target, limit break- and watchpoints
18778 @anchor{set remote hardware-watchpoint-limit}
18779 @anchor{set remote hardware-breakpoint-limit}
18780 @item set remote hardware-watchpoint-limit @var{limit}
18781 @itemx set remote hardware-breakpoint-limit @var{limit}
18782 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
18783 watchpoints. A limit of -1, the default, is treated as unlimited.
18785 @cindex limit hardware watchpoints length
18786 @cindex remote target, limit watchpoints length
18787 @anchor{set remote hardware-watchpoint-length-limit}
18788 @item set remote hardware-watchpoint-length-limit @var{limit}
18789 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
18790 a remote hardware watchpoint. A limit of -1, the default, is treated
18793 @item show remote hardware-watchpoint-length-limit
18794 Show the current limit (in bytes) of the maximum length of
18795 a remote hardware watchpoint.
18797 @item set remote exec-file @var{filename}
18798 @itemx show remote exec-file
18799 @anchor{set remote exec-file}
18800 @cindex executable file, for remote target
18801 Select the file used for @code{run} with @code{target
18802 extended-remote}. This should be set to a filename valid on the
18803 target system. If it is not set, the target will use a default
18804 filename (e.g.@: the last program run).
18806 @item set remote interrupt-sequence
18807 @cindex interrupt remote programs
18808 @cindex select Ctrl-C, BREAK or BREAK-g
18809 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
18810 @samp{BREAK-g} as the
18811 sequence to the remote target in order to interrupt the execution.
18812 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
18813 is high level of serial line for some certain time.
18814 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
18815 It is @code{BREAK} signal followed by character @code{g}.
18817 @item show interrupt-sequence
18818 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
18819 is sent by @value{GDBN} to interrupt the remote program.
18820 @code{BREAK-g} is BREAK signal followed by @code{g} and
18821 also known as Magic SysRq g.
18823 @item set remote interrupt-on-connect
18824 @cindex send interrupt-sequence on start
18825 Specify whether interrupt-sequence is sent to remote target when
18826 @value{GDBN} connects to it. This is mostly needed when you debug
18827 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
18828 which is known as Magic SysRq g in order to connect @value{GDBN}.
18830 @item show interrupt-on-connect
18831 Show whether interrupt-sequence is sent
18832 to remote target when @value{GDBN} connects to it.
18836 @item set tcp auto-retry on
18837 @cindex auto-retry, for remote TCP target
18838 Enable auto-retry for remote TCP connections. This is useful if the remote
18839 debugging agent is launched in parallel with @value{GDBN}; there is a race
18840 condition because the agent may not become ready to accept the connection
18841 before @value{GDBN} attempts to connect. When auto-retry is
18842 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
18843 to establish the connection using the timeout specified by
18844 @code{set tcp connect-timeout}.
18846 @item set tcp auto-retry off
18847 Do not auto-retry failed TCP connections.
18849 @item show tcp auto-retry
18850 Show the current auto-retry setting.
18852 @item set tcp connect-timeout @var{seconds}
18853 @itemx set tcp connect-timeout unlimited
18854 @cindex connection timeout, for remote TCP target
18855 @cindex timeout, for remote target connection
18856 Set the timeout for establishing a TCP connection to the remote target to
18857 @var{seconds}. The timeout affects both polling to retry failed connections
18858 (enabled by @code{set tcp auto-retry on}) and waiting for connections
18859 that are merely slow to complete, and represents an approximate cumulative
18860 value. If @var{seconds} is @code{unlimited}, there is no timeout and
18861 @value{GDBN} will keep attempting to establish a connection forever,
18862 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
18864 @item show tcp connect-timeout
18865 Show the current connection timeout setting.
18868 @cindex remote packets, enabling and disabling
18869 The @value{GDBN} remote protocol autodetects the packets supported by
18870 your debugging stub. If you need to override the autodetection, you
18871 can use these commands to enable or disable individual packets. Each
18872 packet can be set to @samp{on} (the remote target supports this
18873 packet), @samp{off} (the remote target does not support this packet),
18874 or @samp{auto} (detect remote target support for this packet). They
18875 all default to @samp{auto}. For more information about each packet,
18876 see @ref{Remote Protocol}.
18878 During normal use, you should not have to use any of these commands.
18879 If you do, that may be a bug in your remote debugging stub, or a bug
18880 in @value{GDBN}. You may want to report the problem to the
18881 @value{GDBN} developers.
18883 For each packet @var{name}, the command to enable or disable the
18884 packet is @code{set remote @var{name}-packet}. The available settings
18887 @multitable @columnfractions 0.28 0.32 0.25
18890 @tab Related Features
18892 @item @code{fetch-register}
18894 @tab @code{info registers}
18896 @item @code{set-register}
18900 @item @code{binary-download}
18902 @tab @code{load}, @code{set}
18904 @item @code{read-aux-vector}
18905 @tab @code{qXfer:auxv:read}
18906 @tab @code{info auxv}
18908 @item @code{symbol-lookup}
18909 @tab @code{qSymbol}
18910 @tab Detecting multiple threads
18912 @item @code{attach}
18913 @tab @code{vAttach}
18916 @item @code{verbose-resume}
18918 @tab Stepping or resuming multiple threads
18924 @item @code{software-breakpoint}
18928 @item @code{hardware-breakpoint}
18932 @item @code{write-watchpoint}
18936 @item @code{read-watchpoint}
18940 @item @code{access-watchpoint}
18944 @item @code{target-features}
18945 @tab @code{qXfer:features:read}
18946 @tab @code{set architecture}
18948 @item @code{library-info}
18949 @tab @code{qXfer:libraries:read}
18950 @tab @code{info sharedlibrary}
18952 @item @code{memory-map}
18953 @tab @code{qXfer:memory-map:read}
18954 @tab @code{info mem}
18956 @item @code{read-sdata-object}
18957 @tab @code{qXfer:sdata:read}
18958 @tab @code{print $_sdata}
18960 @item @code{read-spu-object}
18961 @tab @code{qXfer:spu:read}
18962 @tab @code{info spu}
18964 @item @code{write-spu-object}
18965 @tab @code{qXfer:spu:write}
18966 @tab @code{info spu}
18968 @item @code{read-siginfo-object}
18969 @tab @code{qXfer:siginfo:read}
18970 @tab @code{print $_siginfo}
18972 @item @code{write-siginfo-object}
18973 @tab @code{qXfer:siginfo:write}
18974 @tab @code{set $_siginfo}
18976 @item @code{threads}
18977 @tab @code{qXfer:threads:read}
18978 @tab @code{info threads}
18980 @item @code{get-thread-local-@*storage-address}
18981 @tab @code{qGetTLSAddr}
18982 @tab Displaying @code{__thread} variables
18984 @item @code{get-thread-information-block-address}
18985 @tab @code{qGetTIBAddr}
18986 @tab Display MS-Windows Thread Information Block.
18988 @item @code{search-memory}
18989 @tab @code{qSearch:memory}
18992 @item @code{supported-packets}
18993 @tab @code{qSupported}
18994 @tab Remote communications parameters
18996 @item @code{pass-signals}
18997 @tab @code{QPassSignals}
18998 @tab @code{handle @var{signal}}
19000 @item @code{program-signals}
19001 @tab @code{QProgramSignals}
19002 @tab @code{handle @var{signal}}
19004 @item @code{hostio-close-packet}
19005 @tab @code{vFile:close}
19006 @tab @code{remote get}, @code{remote put}
19008 @item @code{hostio-open-packet}
19009 @tab @code{vFile:open}
19010 @tab @code{remote get}, @code{remote put}
19012 @item @code{hostio-pread-packet}
19013 @tab @code{vFile:pread}
19014 @tab @code{remote get}, @code{remote put}
19016 @item @code{hostio-pwrite-packet}
19017 @tab @code{vFile:pwrite}
19018 @tab @code{remote get}, @code{remote put}
19020 @item @code{hostio-unlink-packet}
19021 @tab @code{vFile:unlink}
19022 @tab @code{remote delete}
19024 @item @code{hostio-readlink-packet}
19025 @tab @code{vFile:readlink}
19028 @item @code{noack-packet}
19029 @tab @code{QStartNoAckMode}
19030 @tab Packet acknowledgment
19032 @item @code{osdata}
19033 @tab @code{qXfer:osdata:read}
19034 @tab @code{info os}
19036 @item @code{query-attached}
19037 @tab @code{qAttached}
19038 @tab Querying remote process attach state.
19040 @item @code{trace-buffer-size}
19041 @tab @code{QTBuffer:size}
19042 @tab @code{set trace-buffer-size}
19044 @item @code{trace-status}
19045 @tab @code{qTStatus}
19046 @tab @code{tstatus}
19048 @item @code{traceframe-info}
19049 @tab @code{qXfer:traceframe-info:read}
19050 @tab Traceframe info
19052 @item @code{install-in-trace}
19053 @tab @code{InstallInTrace}
19054 @tab Install tracepoint in tracing
19056 @item @code{disable-randomization}
19057 @tab @code{QDisableRandomization}
19058 @tab @code{set disable-randomization}
19060 @item @code{conditional-breakpoints-packet}
19061 @tab @code{Z0 and Z1}
19062 @tab @code{Support for target-side breakpoint condition evaluation}
19066 @section Implementing a Remote Stub
19068 @cindex debugging stub, example
19069 @cindex remote stub, example
19070 @cindex stub example, remote debugging
19071 The stub files provided with @value{GDBN} implement the target side of the
19072 communication protocol, and the @value{GDBN} side is implemented in the
19073 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
19074 these subroutines to communicate, and ignore the details. (If you're
19075 implementing your own stub file, you can still ignore the details: start
19076 with one of the existing stub files. @file{sparc-stub.c} is the best
19077 organized, and therefore the easiest to read.)
19079 @cindex remote serial debugging, overview
19080 To debug a program running on another machine (the debugging
19081 @dfn{target} machine), you must first arrange for all the usual
19082 prerequisites for the program to run by itself. For example, for a C
19087 A startup routine to set up the C runtime environment; these usually
19088 have a name like @file{crt0}. The startup routine may be supplied by
19089 your hardware supplier, or you may have to write your own.
19092 A C subroutine library to support your program's
19093 subroutine calls, notably managing input and output.
19096 A way of getting your program to the other machine---for example, a
19097 download program. These are often supplied by the hardware
19098 manufacturer, but you may have to write your own from hardware
19102 The next step is to arrange for your program to use a serial port to
19103 communicate with the machine where @value{GDBN} is running (the @dfn{host}
19104 machine). In general terms, the scheme looks like this:
19108 @value{GDBN} already understands how to use this protocol; when everything
19109 else is set up, you can simply use the @samp{target remote} command
19110 (@pxref{Targets,,Specifying a Debugging Target}).
19112 @item On the target,
19113 you must link with your program a few special-purpose subroutines that
19114 implement the @value{GDBN} remote serial protocol. The file containing these
19115 subroutines is called a @dfn{debugging stub}.
19117 On certain remote targets, you can use an auxiliary program
19118 @code{gdbserver} instead of linking a stub into your program.
19119 @xref{Server,,Using the @code{gdbserver} Program}, for details.
19122 The debugging stub is specific to the architecture of the remote
19123 machine; for example, use @file{sparc-stub.c} to debug programs on
19126 @cindex remote serial stub list
19127 These working remote stubs are distributed with @value{GDBN}:
19132 @cindex @file{i386-stub.c}
19135 For Intel 386 and compatible architectures.
19138 @cindex @file{m68k-stub.c}
19139 @cindex Motorola 680x0
19141 For Motorola 680x0 architectures.
19144 @cindex @file{sh-stub.c}
19147 For Renesas SH architectures.
19150 @cindex @file{sparc-stub.c}
19152 For @sc{sparc} architectures.
19154 @item sparcl-stub.c
19155 @cindex @file{sparcl-stub.c}
19158 For Fujitsu @sc{sparclite} architectures.
19162 The @file{README} file in the @value{GDBN} distribution may list other
19163 recently added stubs.
19166 * Stub Contents:: What the stub can do for you
19167 * Bootstrapping:: What you must do for the stub
19168 * Debug Session:: Putting it all together
19171 @node Stub Contents
19172 @subsection What the Stub Can Do for You
19174 @cindex remote serial stub
19175 The debugging stub for your architecture supplies these three
19179 @item set_debug_traps
19180 @findex set_debug_traps
19181 @cindex remote serial stub, initialization
19182 This routine arranges for @code{handle_exception} to run when your
19183 program stops. You must call this subroutine explicitly in your
19184 program's startup code.
19186 @item handle_exception
19187 @findex handle_exception
19188 @cindex remote serial stub, main routine
19189 This is the central workhorse, but your program never calls it
19190 explicitly---the setup code arranges for @code{handle_exception} to
19191 run when a trap is triggered.
19193 @code{handle_exception} takes control when your program stops during
19194 execution (for example, on a breakpoint), and mediates communications
19195 with @value{GDBN} on the host machine. This is where the communications
19196 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
19197 representative on the target machine. It begins by sending summary
19198 information on the state of your program, then continues to execute,
19199 retrieving and transmitting any information @value{GDBN} needs, until you
19200 execute a @value{GDBN} command that makes your program resume; at that point,
19201 @code{handle_exception} returns control to your own code on the target
19205 @cindex @code{breakpoint} subroutine, remote
19206 Use this auxiliary subroutine to make your program contain a
19207 breakpoint. Depending on the particular situation, this may be the only
19208 way for @value{GDBN} to get control. For instance, if your target
19209 machine has some sort of interrupt button, you won't need to call this;
19210 pressing the interrupt button transfers control to
19211 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
19212 simply receiving characters on the serial port may also trigger a trap;
19213 again, in that situation, you don't need to call @code{breakpoint} from
19214 your own program---simply running @samp{target remote} from the host
19215 @value{GDBN} session gets control.
19217 Call @code{breakpoint} if none of these is true, or if you simply want
19218 to make certain your program stops at a predetermined point for the
19219 start of your debugging session.
19222 @node Bootstrapping
19223 @subsection What You Must Do for the Stub
19225 @cindex remote stub, support routines
19226 The debugging stubs that come with @value{GDBN} are set up for a particular
19227 chip architecture, but they have no information about the rest of your
19228 debugging target machine.
19230 First of all you need to tell the stub how to communicate with the
19234 @item int getDebugChar()
19235 @findex getDebugChar
19236 Write this subroutine to read a single character from the serial port.
19237 It may be identical to @code{getchar} for your target system; a
19238 different name is used to allow you to distinguish the two if you wish.
19240 @item void putDebugChar(int)
19241 @findex putDebugChar
19242 Write this subroutine to write a single character to the serial port.
19243 It may be identical to @code{putchar} for your target system; a
19244 different name is used to allow you to distinguish the two if you wish.
19247 @cindex control C, and remote debugging
19248 @cindex interrupting remote targets
19249 If you want @value{GDBN} to be able to stop your program while it is
19250 running, you need to use an interrupt-driven serial driver, and arrange
19251 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
19252 character). That is the character which @value{GDBN} uses to tell the
19253 remote system to stop.
19255 Getting the debugging target to return the proper status to @value{GDBN}
19256 probably requires changes to the standard stub; one quick and dirty way
19257 is to just execute a breakpoint instruction (the ``dirty'' part is that
19258 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
19260 Other routines you need to supply are:
19263 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
19264 @findex exceptionHandler
19265 Write this function to install @var{exception_address} in the exception
19266 handling tables. You need to do this because the stub does not have any
19267 way of knowing what the exception handling tables on your target system
19268 are like (for example, the processor's table might be in @sc{rom},
19269 containing entries which point to a table in @sc{ram}).
19270 @var{exception_number} is the exception number which should be changed;
19271 its meaning is architecture-dependent (for example, different numbers
19272 might represent divide by zero, misaligned access, etc). When this
19273 exception occurs, control should be transferred directly to
19274 @var{exception_address}, and the processor state (stack, registers,
19275 and so on) should be just as it is when a processor exception occurs. So if
19276 you want to use a jump instruction to reach @var{exception_address}, it
19277 should be a simple jump, not a jump to subroutine.
19279 For the 386, @var{exception_address} should be installed as an interrupt
19280 gate so that interrupts are masked while the handler runs. The gate
19281 should be at privilege level 0 (the most privileged level). The
19282 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
19283 help from @code{exceptionHandler}.
19285 @item void flush_i_cache()
19286 @findex flush_i_cache
19287 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
19288 instruction cache, if any, on your target machine. If there is no
19289 instruction cache, this subroutine may be a no-op.
19291 On target machines that have instruction caches, @value{GDBN} requires this
19292 function to make certain that the state of your program is stable.
19296 You must also make sure this library routine is available:
19299 @item void *memset(void *, int, int)
19301 This is the standard library function @code{memset} that sets an area of
19302 memory to a known value. If you have one of the free versions of
19303 @code{libc.a}, @code{memset} can be found there; otherwise, you must
19304 either obtain it from your hardware manufacturer, or write your own.
19307 If you do not use the GNU C compiler, you may need other standard
19308 library subroutines as well; this varies from one stub to another,
19309 but in general the stubs are likely to use any of the common library
19310 subroutines which @code{@value{NGCC}} generates as inline code.
19313 @node Debug Session
19314 @subsection Putting it All Together
19316 @cindex remote serial debugging summary
19317 In summary, when your program is ready to debug, you must follow these
19322 Make sure you have defined the supporting low-level routines
19323 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
19325 @code{getDebugChar}, @code{putDebugChar},
19326 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
19330 Insert these lines in your program's startup code, before the main
19331 procedure is called:
19338 On some machines, when a breakpoint trap is raised, the hardware
19339 automatically makes the PC point to the instruction after the
19340 breakpoint. If your machine doesn't do that, you may need to adjust
19341 @code{handle_exception} to arrange for it to return to the instruction
19342 after the breakpoint on this first invocation, so that your program
19343 doesn't keep hitting the initial breakpoint instead of making
19347 For the 680x0 stub only, you need to provide a variable called
19348 @code{exceptionHook}. Normally you just use:
19351 void (*exceptionHook)() = 0;
19355 but if before calling @code{set_debug_traps}, you set it to point to a
19356 function in your program, that function is called when
19357 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
19358 error). The function indicated by @code{exceptionHook} is called with
19359 one parameter: an @code{int} which is the exception number.
19362 Compile and link together: your program, the @value{GDBN} debugging stub for
19363 your target architecture, and the supporting subroutines.
19366 Make sure you have a serial connection between your target machine and
19367 the @value{GDBN} host, and identify the serial port on the host.
19370 @c The "remote" target now provides a `load' command, so we should
19371 @c document that. FIXME.
19372 Download your program to your target machine (or get it there by
19373 whatever means the manufacturer provides), and start it.
19376 Start @value{GDBN} on the host, and connect to the target
19377 (@pxref{Connecting,,Connecting to a Remote Target}).
19381 @node Configurations
19382 @chapter Configuration-Specific Information
19384 While nearly all @value{GDBN} commands are available for all native and
19385 cross versions of the debugger, there are some exceptions. This chapter
19386 describes things that are only available in certain configurations.
19388 There are three major categories of configurations: native
19389 configurations, where the host and target are the same, embedded
19390 operating system configurations, which are usually the same for several
19391 different processor architectures, and bare embedded processors, which
19392 are quite different from each other.
19397 * Embedded Processors::
19404 This section describes details specific to particular native
19409 * BSD libkvm Interface:: Debugging BSD kernel memory images
19410 * SVR4 Process Information:: SVR4 process information
19411 * DJGPP Native:: Features specific to the DJGPP port
19412 * Cygwin Native:: Features specific to the Cygwin port
19413 * Hurd Native:: Features specific to @sc{gnu} Hurd
19414 * Darwin:: Features specific to Darwin
19420 On HP-UX systems, if you refer to a function or variable name that
19421 begins with a dollar sign, @value{GDBN} searches for a user or system
19422 name first, before it searches for a convenience variable.
19425 @node BSD libkvm Interface
19426 @subsection BSD libkvm Interface
19429 @cindex kernel memory image
19430 @cindex kernel crash dump
19432 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
19433 interface that provides a uniform interface for accessing kernel virtual
19434 memory images, including live systems and crash dumps. @value{GDBN}
19435 uses this interface to allow you to debug live kernels and kernel crash
19436 dumps on many native BSD configurations. This is implemented as a
19437 special @code{kvm} debugging target. For debugging a live system, load
19438 the currently running kernel into @value{GDBN} and connect to the
19442 (@value{GDBP}) @b{target kvm}
19445 For debugging crash dumps, provide the file name of the crash dump as an
19449 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
19452 Once connected to the @code{kvm} target, the following commands are
19458 Set current context from the @dfn{Process Control Block} (PCB) address.
19461 Set current context from proc address. This command isn't available on
19462 modern FreeBSD systems.
19465 @node SVR4 Process Information
19466 @subsection SVR4 Process Information
19468 @cindex examine process image
19469 @cindex process info via @file{/proc}
19471 Many versions of SVR4 and compatible systems provide a facility called
19472 @samp{/proc} that can be used to examine the image of a running
19473 process using file-system subroutines.
19475 If @value{GDBN} is configured for an operating system with this
19476 facility, the command @code{info proc} is available to report
19477 information about the process running your program, or about any
19478 process running on your system. This includes, as of this writing,
19479 @sc{gnu}/Linux, OSF/1 (Digital Unix), Solaris, and Irix, but
19480 not HP-UX, for example.
19482 This command may also work on core files that were created on a system
19483 that has the @samp{/proc} facility.
19489 @itemx info proc @var{process-id}
19490 Summarize available information about any running process. If a
19491 process ID is specified by @var{process-id}, display information about
19492 that process; otherwise display information about the program being
19493 debugged. The summary includes the debugged process ID, the command
19494 line used to invoke it, its current working directory, and its
19495 executable file's absolute file name.
19497 On some systems, @var{process-id} can be of the form
19498 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
19499 within a process. If the optional @var{pid} part is missing, it means
19500 a thread from the process being debugged (the leading @samp{/} still
19501 needs to be present, or else @value{GDBN} will interpret the number as
19502 a process ID rather than a thread ID).
19504 @item info proc cmdline
19505 @cindex info proc cmdline
19506 Show the original command line of the process. This command is
19507 specific to @sc{gnu}/Linux.
19509 @item info proc cwd
19510 @cindex info proc cwd
19511 Show the current working directory of the process. This command is
19512 specific to @sc{gnu}/Linux.
19514 @item info proc exe
19515 @cindex info proc exe
19516 Show the name of executable of the process. This command is specific
19519 @item info proc mappings
19520 @cindex memory address space mappings
19521 Report the memory address space ranges accessible in the program, with
19522 information on whether the process has read, write, or execute access
19523 rights to each range. On @sc{gnu}/Linux systems, each memory range
19524 includes the object file which is mapped to that range, instead of the
19525 memory access rights to that range.
19527 @item info proc stat
19528 @itemx info proc status
19529 @cindex process detailed status information
19530 These subcommands are specific to @sc{gnu}/Linux systems. They show
19531 the process-related information, including the user ID and group ID;
19532 how many threads are there in the process; its virtual memory usage;
19533 the signals that are pending, blocked, and ignored; its TTY; its
19534 consumption of system and user time; its stack size; its @samp{nice}
19535 value; etc. For more information, see the @samp{proc} man page
19536 (type @kbd{man 5 proc} from your shell prompt).
19538 @item info proc all
19539 Show all the information about the process described under all of the
19540 above @code{info proc} subcommands.
19543 @comment These sub-options of 'info proc' were not included when
19544 @comment procfs.c was re-written. Keep their descriptions around
19545 @comment against the day when someone finds the time to put them back in.
19546 @kindex info proc times
19547 @item info proc times
19548 Starting time, user CPU time, and system CPU time for your program and
19551 @kindex info proc id
19553 Report on the process IDs related to your program: its own process ID,
19554 the ID of its parent, the process group ID, and the session ID.
19557 @item set procfs-trace
19558 @kindex set procfs-trace
19559 @cindex @code{procfs} API calls
19560 This command enables and disables tracing of @code{procfs} API calls.
19562 @item show procfs-trace
19563 @kindex show procfs-trace
19564 Show the current state of @code{procfs} API call tracing.
19566 @item set procfs-file @var{file}
19567 @kindex set procfs-file
19568 Tell @value{GDBN} to write @code{procfs} API trace to the named
19569 @var{file}. @value{GDBN} appends the trace info to the previous
19570 contents of the file. The default is to display the trace on the
19573 @item show procfs-file
19574 @kindex show procfs-file
19575 Show the file to which @code{procfs} API trace is written.
19577 @item proc-trace-entry
19578 @itemx proc-trace-exit
19579 @itemx proc-untrace-entry
19580 @itemx proc-untrace-exit
19581 @kindex proc-trace-entry
19582 @kindex proc-trace-exit
19583 @kindex proc-untrace-entry
19584 @kindex proc-untrace-exit
19585 These commands enable and disable tracing of entries into and exits
19586 from the @code{syscall} interface.
19589 @kindex info pidlist
19590 @cindex process list, QNX Neutrino
19591 For QNX Neutrino only, this command displays the list of all the
19592 processes and all the threads within each process.
19595 @kindex info meminfo
19596 @cindex mapinfo list, QNX Neutrino
19597 For QNX Neutrino only, this command displays the list of all mapinfos.
19601 @subsection Features for Debugging @sc{djgpp} Programs
19602 @cindex @sc{djgpp} debugging
19603 @cindex native @sc{djgpp} debugging
19604 @cindex MS-DOS-specific commands
19607 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
19608 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
19609 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
19610 top of real-mode DOS systems and their emulations.
19612 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
19613 defines a few commands specific to the @sc{djgpp} port. This
19614 subsection describes those commands.
19619 This is a prefix of @sc{djgpp}-specific commands which print
19620 information about the target system and important OS structures.
19623 @cindex MS-DOS system info
19624 @cindex free memory information (MS-DOS)
19625 @item info dos sysinfo
19626 This command displays assorted information about the underlying
19627 platform: the CPU type and features, the OS version and flavor, the
19628 DPMI version, and the available conventional and DPMI memory.
19633 @cindex segment descriptor tables
19634 @cindex descriptor tables display
19636 @itemx info dos ldt
19637 @itemx info dos idt
19638 These 3 commands display entries from, respectively, Global, Local,
19639 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
19640 tables are data structures which store a descriptor for each segment
19641 that is currently in use. The segment's selector is an index into a
19642 descriptor table; the table entry for that index holds the
19643 descriptor's base address and limit, and its attributes and access
19646 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
19647 segment (used for both data and the stack), and a DOS segment (which
19648 allows access to DOS/BIOS data structures and absolute addresses in
19649 conventional memory). However, the DPMI host will usually define
19650 additional segments in order to support the DPMI environment.
19652 @cindex garbled pointers
19653 These commands allow to display entries from the descriptor tables.
19654 Without an argument, all entries from the specified table are
19655 displayed. An argument, which should be an integer expression, means
19656 display a single entry whose index is given by the argument. For
19657 example, here's a convenient way to display information about the
19658 debugged program's data segment:
19661 @exdent @code{(@value{GDBP}) info dos ldt $ds}
19662 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
19666 This comes in handy when you want to see whether a pointer is outside
19667 the data segment's limit (i.e.@: @dfn{garbled}).
19669 @cindex page tables display (MS-DOS)
19671 @itemx info dos pte
19672 These two commands display entries from, respectively, the Page
19673 Directory and the Page Tables. Page Directories and Page Tables are
19674 data structures which control how virtual memory addresses are mapped
19675 into physical addresses. A Page Table includes an entry for every
19676 page of memory that is mapped into the program's address space; there
19677 may be several Page Tables, each one holding up to 4096 entries. A
19678 Page Directory has up to 4096 entries, one each for every Page Table
19679 that is currently in use.
19681 Without an argument, @kbd{info dos pde} displays the entire Page
19682 Directory, and @kbd{info dos pte} displays all the entries in all of
19683 the Page Tables. An argument, an integer expression, given to the
19684 @kbd{info dos pde} command means display only that entry from the Page
19685 Directory table. An argument given to the @kbd{info dos pte} command
19686 means display entries from a single Page Table, the one pointed to by
19687 the specified entry in the Page Directory.
19689 @cindex direct memory access (DMA) on MS-DOS
19690 These commands are useful when your program uses @dfn{DMA} (Direct
19691 Memory Access), which needs physical addresses to program the DMA
19694 These commands are supported only with some DPMI servers.
19696 @cindex physical address from linear address
19697 @item info dos address-pte @var{addr}
19698 This command displays the Page Table entry for a specified linear
19699 address. The argument @var{addr} is a linear address which should
19700 already have the appropriate segment's base address added to it,
19701 because this command accepts addresses which may belong to @emph{any}
19702 segment. For example, here's how to display the Page Table entry for
19703 the page where a variable @code{i} is stored:
19706 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
19707 @exdent @code{Page Table entry for address 0x11a00d30:}
19708 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
19712 This says that @code{i} is stored at offset @code{0xd30} from the page
19713 whose physical base address is @code{0x02698000}, and shows all the
19714 attributes of that page.
19716 Note that you must cast the addresses of variables to a @code{char *},
19717 since otherwise the value of @code{__djgpp_base_address}, the base
19718 address of all variables and functions in a @sc{djgpp} program, will
19719 be added using the rules of C pointer arithmetics: if @code{i} is
19720 declared an @code{int}, @value{GDBN} will add 4 times the value of
19721 @code{__djgpp_base_address} to the address of @code{i}.
19723 Here's another example, it displays the Page Table entry for the
19727 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
19728 @exdent @code{Page Table entry for address 0x29110:}
19729 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
19733 (The @code{+ 3} offset is because the transfer buffer's address is the
19734 3rd member of the @code{_go32_info_block} structure.) The output
19735 clearly shows that this DPMI server maps the addresses in conventional
19736 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
19737 linear (@code{0x29110}) addresses are identical.
19739 This command is supported only with some DPMI servers.
19742 @cindex DOS serial data link, remote debugging
19743 In addition to native debugging, the DJGPP port supports remote
19744 debugging via a serial data link. The following commands are specific
19745 to remote serial debugging in the DJGPP port of @value{GDBN}.
19748 @kindex set com1base
19749 @kindex set com1irq
19750 @kindex set com2base
19751 @kindex set com2irq
19752 @kindex set com3base
19753 @kindex set com3irq
19754 @kindex set com4base
19755 @kindex set com4irq
19756 @item set com1base @var{addr}
19757 This command sets the base I/O port address of the @file{COM1} serial
19760 @item set com1irq @var{irq}
19761 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
19762 for the @file{COM1} serial port.
19764 There are similar commands @samp{set com2base}, @samp{set com3irq},
19765 etc.@: for setting the port address and the @code{IRQ} lines for the
19768 @kindex show com1base
19769 @kindex show com1irq
19770 @kindex show com2base
19771 @kindex show com2irq
19772 @kindex show com3base
19773 @kindex show com3irq
19774 @kindex show com4base
19775 @kindex show com4irq
19776 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
19777 display the current settings of the base address and the @code{IRQ}
19778 lines used by the COM ports.
19781 @kindex info serial
19782 @cindex DOS serial port status
19783 This command prints the status of the 4 DOS serial ports. For each
19784 port, it prints whether it's active or not, its I/O base address and
19785 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
19786 counts of various errors encountered so far.
19790 @node Cygwin Native
19791 @subsection Features for Debugging MS Windows PE Executables
19792 @cindex MS Windows debugging
19793 @cindex native Cygwin debugging
19794 @cindex Cygwin-specific commands
19796 @value{GDBN} supports native debugging of MS Windows programs, including
19797 DLLs with and without symbolic debugging information.
19799 @cindex Ctrl-BREAK, MS-Windows
19800 @cindex interrupt debuggee on MS-Windows
19801 MS-Windows programs that call @code{SetConsoleMode} to switch off the
19802 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
19803 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
19804 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
19805 sequence, which can be used to interrupt the debuggee even if it
19808 There are various additional Cygwin-specific commands, described in
19809 this section. Working with DLLs that have no debugging symbols is
19810 described in @ref{Non-debug DLL Symbols}.
19815 This is a prefix of MS Windows-specific commands which print
19816 information about the target system and important OS structures.
19818 @item info w32 selector
19819 This command displays information returned by
19820 the Win32 API @code{GetThreadSelectorEntry} function.
19821 It takes an optional argument that is evaluated to
19822 a long value to give the information about this given selector.
19823 Without argument, this command displays information
19824 about the six segment registers.
19826 @item info w32 thread-information-block
19827 This command displays thread specific information stored in the
19828 Thread Information Block (readable on the X86 CPU family using @code{$fs}
19829 selector for 32-bit programs and @code{$gs} for 64-bit programs).
19833 This is a Cygwin-specific alias of @code{info shared}.
19835 @kindex dll-symbols
19837 This command loads symbols from a dll similarly to
19838 add-sym command but without the need to specify a base address.
19840 @kindex set cygwin-exceptions
19841 @cindex debugging the Cygwin DLL
19842 @cindex Cygwin DLL, debugging
19843 @item set cygwin-exceptions @var{mode}
19844 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
19845 happen inside the Cygwin DLL. If @var{mode} is @code{off},
19846 @value{GDBN} will delay recognition of exceptions, and may ignore some
19847 exceptions which seem to be caused by internal Cygwin DLL
19848 ``bookkeeping''. This option is meant primarily for debugging the
19849 Cygwin DLL itself; the default value is @code{off} to avoid annoying
19850 @value{GDBN} users with false @code{SIGSEGV} signals.
19852 @kindex show cygwin-exceptions
19853 @item show cygwin-exceptions
19854 Displays whether @value{GDBN} will break on exceptions that happen
19855 inside the Cygwin DLL itself.
19857 @kindex set new-console
19858 @item set new-console @var{mode}
19859 If @var{mode} is @code{on} the debuggee will
19860 be started in a new console on next start.
19861 If @var{mode} is @code{off}, the debuggee will
19862 be started in the same console as the debugger.
19864 @kindex show new-console
19865 @item show new-console
19866 Displays whether a new console is used
19867 when the debuggee is started.
19869 @kindex set new-group
19870 @item set new-group @var{mode}
19871 This boolean value controls whether the debuggee should
19872 start a new group or stay in the same group as the debugger.
19873 This affects the way the Windows OS handles
19876 @kindex show new-group
19877 @item show new-group
19878 Displays current value of new-group boolean.
19880 @kindex set debugevents
19881 @item set debugevents
19882 This boolean value adds debug output concerning kernel events related
19883 to the debuggee seen by the debugger. This includes events that
19884 signal thread and process creation and exit, DLL loading and
19885 unloading, console interrupts, and debugging messages produced by the
19886 Windows @code{OutputDebugString} API call.
19888 @kindex set debugexec
19889 @item set debugexec
19890 This boolean value adds debug output concerning execute events
19891 (such as resume thread) seen by the debugger.
19893 @kindex set debugexceptions
19894 @item set debugexceptions
19895 This boolean value adds debug output concerning exceptions in the
19896 debuggee seen by the debugger.
19898 @kindex set debugmemory
19899 @item set debugmemory
19900 This boolean value adds debug output concerning debuggee memory reads
19901 and writes by the debugger.
19905 This boolean values specifies whether the debuggee is called
19906 via a shell or directly (default value is on).
19910 Displays if the debuggee will be started with a shell.
19915 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
19918 @node Non-debug DLL Symbols
19919 @subsubsection Support for DLLs without Debugging Symbols
19920 @cindex DLLs with no debugging symbols
19921 @cindex Minimal symbols and DLLs
19923 Very often on windows, some of the DLLs that your program relies on do
19924 not include symbolic debugging information (for example,
19925 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
19926 symbols in a DLL, it relies on the minimal amount of symbolic
19927 information contained in the DLL's export table. This section
19928 describes working with such symbols, known internally to @value{GDBN} as
19929 ``minimal symbols''.
19931 Note that before the debugged program has started execution, no DLLs
19932 will have been loaded. The easiest way around this problem is simply to
19933 start the program --- either by setting a breakpoint or letting the
19934 program run once to completion. It is also possible to force
19935 @value{GDBN} to load a particular DLL before starting the executable ---
19936 see the shared library information in @ref{Files}, or the
19937 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
19938 explicitly loading symbols from a DLL with no debugging information will
19939 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
19940 which may adversely affect symbol lookup performance.
19942 @subsubsection DLL Name Prefixes
19944 In keeping with the naming conventions used by the Microsoft debugging
19945 tools, DLL export symbols are made available with a prefix based on the
19946 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
19947 also entered into the symbol table, so @code{CreateFileA} is often
19948 sufficient. In some cases there will be name clashes within a program
19949 (particularly if the executable itself includes full debugging symbols)
19950 necessitating the use of the fully qualified name when referring to the
19951 contents of the DLL. Use single-quotes around the name to avoid the
19952 exclamation mark (``!'') being interpreted as a language operator.
19954 Note that the internal name of the DLL may be all upper-case, even
19955 though the file name of the DLL is lower-case, or vice-versa. Since
19956 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
19957 some confusion. If in doubt, try the @code{info functions} and
19958 @code{info variables} commands or even @code{maint print msymbols}
19959 (@pxref{Symbols}). Here's an example:
19962 (@value{GDBP}) info function CreateFileA
19963 All functions matching regular expression "CreateFileA":
19965 Non-debugging symbols:
19966 0x77e885f4 CreateFileA
19967 0x77e885f4 KERNEL32!CreateFileA
19971 (@value{GDBP}) info function !
19972 All functions matching regular expression "!":
19974 Non-debugging symbols:
19975 0x6100114c cygwin1!__assert
19976 0x61004034 cygwin1!_dll_crt0@@0
19977 0x61004240 cygwin1!dll_crt0(per_process *)
19981 @subsubsection Working with Minimal Symbols
19983 Symbols extracted from a DLL's export table do not contain very much
19984 type information. All that @value{GDBN} can do is guess whether a symbol
19985 refers to a function or variable depending on the linker section that
19986 contains the symbol. Also note that the actual contents of the memory
19987 contained in a DLL are not available unless the program is running. This
19988 means that you cannot examine the contents of a variable or disassemble
19989 a function within a DLL without a running program.
19991 Variables are generally treated as pointers and dereferenced
19992 automatically. For this reason, it is often necessary to prefix a
19993 variable name with the address-of operator (``&'') and provide explicit
19994 type information in the command. Here's an example of the type of
19998 (@value{GDBP}) print 'cygwin1!__argv'
20003 (@value{GDBP}) x 'cygwin1!__argv'
20004 0x10021610: "\230y\""
20007 And two possible solutions:
20010 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
20011 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
20015 (@value{GDBP}) x/2x &'cygwin1!__argv'
20016 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
20017 (@value{GDBP}) x/x 0x10021608
20018 0x10021608: 0x0022fd98
20019 (@value{GDBP}) x/s 0x0022fd98
20020 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
20023 Setting a break point within a DLL is possible even before the program
20024 starts execution. However, under these circumstances, @value{GDBN} can't
20025 examine the initial instructions of the function in order to skip the
20026 function's frame set-up code. You can work around this by using ``*&''
20027 to set the breakpoint at a raw memory address:
20030 (@value{GDBP}) break *&'python22!PyOS_Readline'
20031 Breakpoint 1 at 0x1e04eff0
20034 The author of these extensions is not entirely convinced that setting a
20035 break point within a shared DLL like @file{kernel32.dll} is completely
20039 @subsection Commands Specific to @sc{gnu} Hurd Systems
20040 @cindex @sc{gnu} Hurd debugging
20042 This subsection describes @value{GDBN} commands specific to the
20043 @sc{gnu} Hurd native debugging.
20048 @kindex set signals@r{, Hurd command}
20049 @kindex set sigs@r{, Hurd command}
20050 This command toggles the state of inferior signal interception by
20051 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
20052 affected by this command. @code{sigs} is a shorthand alias for
20057 @kindex show signals@r{, Hurd command}
20058 @kindex show sigs@r{, Hurd command}
20059 Show the current state of intercepting inferior's signals.
20061 @item set signal-thread
20062 @itemx set sigthread
20063 @kindex set signal-thread
20064 @kindex set sigthread
20065 This command tells @value{GDBN} which thread is the @code{libc} signal
20066 thread. That thread is run when a signal is delivered to a running
20067 process. @code{set sigthread} is the shorthand alias of @code{set
20070 @item show signal-thread
20071 @itemx show sigthread
20072 @kindex show signal-thread
20073 @kindex show sigthread
20074 These two commands show which thread will run when the inferior is
20075 delivered a signal.
20078 @kindex set stopped@r{, Hurd command}
20079 This commands tells @value{GDBN} that the inferior process is stopped,
20080 as with the @code{SIGSTOP} signal. The stopped process can be
20081 continued by delivering a signal to it.
20084 @kindex show stopped@r{, Hurd command}
20085 This command shows whether @value{GDBN} thinks the debuggee is
20088 @item set exceptions
20089 @kindex set exceptions@r{, Hurd command}
20090 Use this command to turn off trapping of exceptions in the inferior.
20091 When exception trapping is off, neither breakpoints nor
20092 single-stepping will work. To restore the default, set exception
20095 @item show exceptions
20096 @kindex show exceptions@r{, Hurd command}
20097 Show the current state of trapping exceptions in the inferior.
20099 @item set task pause
20100 @kindex set task@r{, Hurd commands}
20101 @cindex task attributes (@sc{gnu} Hurd)
20102 @cindex pause current task (@sc{gnu} Hurd)
20103 This command toggles task suspension when @value{GDBN} has control.
20104 Setting it to on takes effect immediately, and the task is suspended
20105 whenever @value{GDBN} gets control. Setting it to off will take
20106 effect the next time the inferior is continued. If this option is set
20107 to off, you can use @code{set thread default pause on} or @code{set
20108 thread pause on} (see below) to pause individual threads.
20110 @item show task pause
20111 @kindex show task@r{, Hurd commands}
20112 Show the current state of task suspension.
20114 @item set task detach-suspend-count
20115 @cindex task suspend count
20116 @cindex detach from task, @sc{gnu} Hurd
20117 This command sets the suspend count the task will be left with when
20118 @value{GDBN} detaches from it.
20120 @item show task detach-suspend-count
20121 Show the suspend count the task will be left with when detaching.
20123 @item set task exception-port
20124 @itemx set task excp
20125 @cindex task exception port, @sc{gnu} Hurd
20126 This command sets the task exception port to which @value{GDBN} will
20127 forward exceptions. The argument should be the value of the @dfn{send
20128 rights} of the task. @code{set task excp} is a shorthand alias.
20130 @item set noninvasive
20131 @cindex noninvasive task options
20132 This command switches @value{GDBN} to a mode that is the least
20133 invasive as far as interfering with the inferior is concerned. This
20134 is the same as using @code{set task pause}, @code{set exceptions}, and
20135 @code{set signals} to values opposite to the defaults.
20137 @item info send-rights
20138 @itemx info receive-rights
20139 @itemx info port-rights
20140 @itemx info port-sets
20141 @itemx info dead-names
20144 @cindex send rights, @sc{gnu} Hurd
20145 @cindex receive rights, @sc{gnu} Hurd
20146 @cindex port rights, @sc{gnu} Hurd
20147 @cindex port sets, @sc{gnu} Hurd
20148 @cindex dead names, @sc{gnu} Hurd
20149 These commands display information about, respectively, send rights,
20150 receive rights, port rights, port sets, and dead names of a task.
20151 There are also shorthand aliases: @code{info ports} for @code{info
20152 port-rights} and @code{info psets} for @code{info port-sets}.
20154 @item set thread pause
20155 @kindex set thread@r{, Hurd command}
20156 @cindex thread properties, @sc{gnu} Hurd
20157 @cindex pause current thread (@sc{gnu} Hurd)
20158 This command toggles current thread suspension when @value{GDBN} has
20159 control. Setting it to on takes effect immediately, and the current
20160 thread is suspended whenever @value{GDBN} gets control. Setting it to
20161 off will take effect the next time the inferior is continued.
20162 Normally, this command has no effect, since when @value{GDBN} has
20163 control, the whole task is suspended. However, if you used @code{set
20164 task pause off} (see above), this command comes in handy to suspend
20165 only the current thread.
20167 @item show thread pause
20168 @kindex show thread@r{, Hurd command}
20169 This command shows the state of current thread suspension.
20171 @item set thread run
20172 This command sets whether the current thread is allowed to run.
20174 @item show thread run
20175 Show whether the current thread is allowed to run.
20177 @item set thread detach-suspend-count
20178 @cindex thread suspend count, @sc{gnu} Hurd
20179 @cindex detach from thread, @sc{gnu} Hurd
20180 This command sets the suspend count @value{GDBN} will leave on a
20181 thread when detaching. This number is relative to the suspend count
20182 found by @value{GDBN} when it notices the thread; use @code{set thread
20183 takeover-suspend-count} to force it to an absolute value.
20185 @item show thread detach-suspend-count
20186 Show the suspend count @value{GDBN} will leave on the thread when
20189 @item set thread exception-port
20190 @itemx set thread excp
20191 Set the thread exception port to which to forward exceptions. This
20192 overrides the port set by @code{set task exception-port} (see above).
20193 @code{set thread excp} is the shorthand alias.
20195 @item set thread takeover-suspend-count
20196 Normally, @value{GDBN}'s thread suspend counts are relative to the
20197 value @value{GDBN} finds when it notices each thread. This command
20198 changes the suspend counts to be absolute instead.
20200 @item set thread default
20201 @itemx show thread default
20202 @cindex thread default settings, @sc{gnu} Hurd
20203 Each of the above @code{set thread} commands has a @code{set thread
20204 default} counterpart (e.g., @code{set thread default pause}, @code{set
20205 thread default exception-port}, etc.). The @code{thread default}
20206 variety of commands sets the default thread properties for all
20207 threads; you can then change the properties of individual threads with
20208 the non-default commands.
20215 @value{GDBN} provides the following commands specific to the Darwin target:
20218 @item set debug darwin @var{num}
20219 @kindex set debug darwin
20220 When set to a non zero value, enables debugging messages specific to
20221 the Darwin support. Higher values produce more verbose output.
20223 @item show debug darwin
20224 @kindex show debug darwin
20225 Show the current state of Darwin messages.
20227 @item set debug mach-o @var{num}
20228 @kindex set debug mach-o
20229 When set to a non zero value, enables debugging messages while
20230 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
20231 file format used on Darwin for object and executable files.) Higher
20232 values produce more verbose output. This is a command to diagnose
20233 problems internal to @value{GDBN} and should not be needed in normal
20236 @item show debug mach-o
20237 @kindex show debug mach-o
20238 Show the current state of Mach-O file messages.
20240 @item set mach-exceptions on
20241 @itemx set mach-exceptions off
20242 @kindex set mach-exceptions
20243 On Darwin, faults are first reported as a Mach exception and are then
20244 mapped to a Posix signal. Use this command to turn on trapping of
20245 Mach exceptions in the inferior. This might be sometimes useful to
20246 better understand the cause of a fault. The default is off.
20248 @item show mach-exceptions
20249 @kindex show mach-exceptions
20250 Show the current state of exceptions trapping.
20255 @section Embedded Operating Systems
20257 This section describes configurations involving the debugging of
20258 embedded operating systems that are available for several different
20262 * VxWorks:: Using @value{GDBN} with VxWorks
20265 @value{GDBN} includes the ability to debug programs running on
20266 various real-time operating systems.
20269 @subsection Using @value{GDBN} with VxWorks
20275 @kindex target vxworks
20276 @item target vxworks @var{machinename}
20277 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
20278 is the target system's machine name or IP address.
20282 On VxWorks, @code{load} links @var{filename} dynamically on the
20283 current target system as well as adding its symbols in @value{GDBN}.
20285 @value{GDBN} enables developers to spawn and debug tasks running on networked
20286 VxWorks targets from a Unix host. Already-running tasks spawned from
20287 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
20288 both the Unix host and on the VxWorks target. The program
20289 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
20290 installed with the name @code{vxgdb}, to distinguish it from a
20291 @value{GDBN} for debugging programs on the host itself.)
20294 @item VxWorks-timeout @var{args}
20295 @kindex vxworks-timeout
20296 All VxWorks-based targets now support the option @code{vxworks-timeout}.
20297 This option is set by the user, and @var{args} represents the number of
20298 seconds @value{GDBN} waits for responses to rpc's. You might use this if
20299 your VxWorks target is a slow software simulator or is on the far side
20300 of a thin network line.
20303 The following information on connecting to VxWorks was current when
20304 this manual was produced; newer releases of VxWorks may use revised
20307 @findex INCLUDE_RDB
20308 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
20309 to include the remote debugging interface routines in the VxWorks
20310 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
20311 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
20312 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
20313 source debugging task @code{tRdbTask} when VxWorks is booted. For more
20314 information on configuring and remaking VxWorks, see the manufacturer's
20316 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
20318 Once you have included @file{rdb.a} in your VxWorks system image and set
20319 your Unix execution search path to find @value{GDBN}, you are ready to
20320 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
20321 @code{vxgdb}, depending on your installation).
20323 @value{GDBN} comes up showing the prompt:
20330 * VxWorks Connection:: Connecting to VxWorks
20331 * VxWorks Download:: VxWorks download
20332 * VxWorks Attach:: Running tasks
20335 @node VxWorks Connection
20336 @subsubsection Connecting to VxWorks
20338 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
20339 network. To connect to a target whose host name is ``@code{tt}'', type:
20342 (vxgdb) target vxworks tt
20346 @value{GDBN} displays messages like these:
20349 Attaching remote machine across net...
20354 @value{GDBN} then attempts to read the symbol tables of any object modules
20355 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
20356 these files by searching the directories listed in the command search
20357 path (@pxref{Environment, ,Your Program's Environment}); if it fails
20358 to find an object file, it displays a message such as:
20361 prog.o: No such file or directory.
20364 When this happens, add the appropriate directory to the search path with
20365 the @value{GDBN} command @code{path}, and execute the @code{target}
20368 @node VxWorks Download
20369 @subsubsection VxWorks Download
20371 @cindex download to VxWorks
20372 If you have connected to the VxWorks target and you want to debug an
20373 object that has not yet been loaded, you can use the @value{GDBN}
20374 @code{load} command to download a file from Unix to VxWorks
20375 incrementally. The object file given as an argument to the @code{load}
20376 command is actually opened twice: first by the VxWorks target in order
20377 to download the code, then by @value{GDBN} in order to read the symbol
20378 table. This can lead to problems if the current working directories on
20379 the two systems differ. If both systems have NFS mounted the same
20380 filesystems, you can avoid these problems by using absolute paths.
20381 Otherwise, it is simplest to set the working directory on both systems
20382 to the directory in which the object file resides, and then to reference
20383 the file by its name, without any path. For instance, a program
20384 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
20385 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
20386 program, type this on VxWorks:
20389 -> cd "@var{vxpath}/vw/demo/rdb"
20393 Then, in @value{GDBN}, type:
20396 (vxgdb) cd @var{hostpath}/vw/demo/rdb
20397 (vxgdb) load prog.o
20400 @value{GDBN} displays a response similar to this:
20403 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
20406 You can also use the @code{load} command to reload an object module
20407 after editing and recompiling the corresponding source file. Note that
20408 this makes @value{GDBN} delete all currently-defined breakpoints,
20409 auto-displays, and convenience variables, and to clear the value
20410 history. (This is necessary in order to preserve the integrity of
20411 debugger's data structures that reference the target system's symbol
20414 @node VxWorks Attach
20415 @subsubsection Running Tasks
20417 @cindex running VxWorks tasks
20418 You can also attach to an existing task using the @code{attach} command as
20422 (vxgdb) attach @var{task}
20426 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
20427 or suspended when you attach to it. Running tasks are suspended at
20428 the time of attachment.
20430 @node Embedded Processors
20431 @section Embedded Processors
20433 This section goes into details specific to particular embedded
20436 @cindex send command to simulator
20437 Whenever a specific embedded processor has a simulator, @value{GDBN}
20438 allows to send an arbitrary command to the simulator.
20441 @item sim @var{command}
20442 @kindex sim@r{, a command}
20443 Send an arbitrary @var{command} string to the simulator. Consult the
20444 documentation for the specific simulator in use for information about
20445 acceptable commands.
20451 * M32R/D:: Renesas M32R/D
20452 * M68K:: Motorola M68K
20453 * MicroBlaze:: Xilinx MicroBlaze
20454 * MIPS Embedded:: MIPS Embedded
20455 * PowerPC Embedded:: PowerPC Embedded
20456 * PA:: HP PA Embedded
20457 * Sparclet:: Tsqware Sparclet
20458 * Sparclite:: Fujitsu Sparclite
20459 * Z8000:: Zilog Z8000
20462 * Super-H:: Renesas Super-H
20471 @item target rdi @var{dev}
20472 ARM Angel monitor, via RDI library interface to ADP protocol. You may
20473 use this target to communicate with both boards running the Angel
20474 monitor, or with the EmbeddedICE JTAG debug device.
20477 @item target rdp @var{dev}
20482 @value{GDBN} provides the following ARM-specific commands:
20485 @item set arm disassembler
20487 This commands selects from a list of disassembly styles. The
20488 @code{"std"} style is the standard style.
20490 @item show arm disassembler
20492 Show the current disassembly style.
20494 @item set arm apcs32
20495 @cindex ARM 32-bit mode
20496 This command toggles ARM operation mode between 32-bit and 26-bit.
20498 @item show arm apcs32
20499 Display the current usage of the ARM 32-bit mode.
20501 @item set arm fpu @var{fputype}
20502 This command sets the ARM floating-point unit (FPU) type. The
20503 argument @var{fputype} can be one of these:
20507 Determine the FPU type by querying the OS ABI.
20509 Software FPU, with mixed-endian doubles on little-endian ARM
20512 GCC-compiled FPA co-processor.
20514 Software FPU with pure-endian doubles.
20520 Show the current type of the FPU.
20523 This command forces @value{GDBN} to use the specified ABI.
20526 Show the currently used ABI.
20528 @item set arm fallback-mode (arm|thumb|auto)
20529 @value{GDBN} uses the symbol table, when available, to determine
20530 whether instructions are ARM or Thumb. This command controls
20531 @value{GDBN}'s default behavior when the symbol table is not
20532 available. The default is @samp{auto}, which causes @value{GDBN} to
20533 use the current execution mode (from the @code{T} bit in the @code{CPSR}
20536 @item show arm fallback-mode
20537 Show the current fallback instruction mode.
20539 @item set arm force-mode (arm|thumb|auto)
20540 This command overrides use of the symbol table to determine whether
20541 instructions are ARM or Thumb. The default is @samp{auto}, which
20542 causes @value{GDBN} to use the symbol table and then the setting
20543 of @samp{set arm fallback-mode}.
20545 @item show arm force-mode
20546 Show the current forced instruction mode.
20548 @item set debug arm
20549 Toggle whether to display ARM-specific debugging messages from the ARM
20550 target support subsystem.
20552 @item show debug arm
20553 Show whether ARM-specific debugging messages are enabled.
20556 The following commands are available when an ARM target is debugged
20557 using the RDI interface:
20560 @item rdilogfile @r{[}@var{file}@r{]}
20562 @cindex ADP (Angel Debugger Protocol) logging
20563 Set the filename for the ADP (Angel Debugger Protocol) packet log.
20564 With an argument, sets the log file to the specified @var{file}. With
20565 no argument, show the current log file name. The default log file is
20568 @item rdilogenable @r{[}@var{arg}@r{]}
20569 @kindex rdilogenable
20570 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
20571 enables logging, with an argument 0 or @code{"no"} disables it. With
20572 no arguments displays the current setting. When logging is enabled,
20573 ADP packets exchanged between @value{GDBN} and the RDI target device
20574 are logged to a file.
20576 @item set rdiromatzero
20577 @kindex set rdiromatzero
20578 @cindex ROM at zero address, RDI
20579 Tell @value{GDBN} whether the target has ROM at address 0. If on,
20580 vector catching is disabled, so that zero address can be used. If off
20581 (the default), vector catching is enabled. For this command to take
20582 effect, it needs to be invoked prior to the @code{target rdi} command.
20584 @item show rdiromatzero
20585 @kindex show rdiromatzero
20586 Show the current setting of ROM at zero address.
20588 @item set rdiheartbeat
20589 @kindex set rdiheartbeat
20590 @cindex RDI heartbeat
20591 Enable or disable RDI heartbeat packets. It is not recommended to
20592 turn on this option, since it confuses ARM and EPI JTAG interface, as
20593 well as the Angel monitor.
20595 @item show rdiheartbeat
20596 @kindex show rdiheartbeat
20597 Show the setting of RDI heartbeat packets.
20601 @item target sim @r{[}@var{simargs}@r{]} @dots{}
20602 The @value{GDBN} ARM simulator accepts the following optional arguments.
20605 @item --swi-support=@var{type}
20606 Tell the simulator which SWI interfaces to support.
20607 @var{type} may be a comma separated list of the following values.
20608 The default value is @code{all}.
20621 @subsection Renesas M32R/D and M32R/SDI
20624 @kindex target m32r
20625 @item target m32r @var{dev}
20626 Renesas M32R/D ROM monitor.
20628 @kindex target m32rsdi
20629 @item target m32rsdi @var{dev}
20630 Renesas M32R SDI server, connected via parallel port to the board.
20633 The following @value{GDBN} commands are specific to the M32R monitor:
20636 @item set download-path @var{path}
20637 @kindex set download-path
20638 @cindex find downloadable @sc{srec} files (M32R)
20639 Set the default path for finding downloadable @sc{srec} files.
20641 @item show download-path
20642 @kindex show download-path
20643 Show the default path for downloadable @sc{srec} files.
20645 @item set board-address @var{addr}
20646 @kindex set board-address
20647 @cindex M32-EVA target board address
20648 Set the IP address for the M32R-EVA target board.
20650 @item show board-address
20651 @kindex show board-address
20652 Show the current IP address of the target board.
20654 @item set server-address @var{addr}
20655 @kindex set server-address
20656 @cindex download server address (M32R)
20657 Set the IP address for the download server, which is the @value{GDBN}'s
20660 @item show server-address
20661 @kindex show server-address
20662 Display the IP address of the download server.
20664 @item upload @r{[}@var{file}@r{]}
20665 @kindex upload@r{, M32R}
20666 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
20667 upload capability. If no @var{file} argument is given, the current
20668 executable file is uploaded.
20670 @item tload @r{[}@var{file}@r{]}
20671 @kindex tload@r{, M32R}
20672 Test the @code{upload} command.
20675 The following commands are available for M32R/SDI:
20680 @cindex reset SDI connection, M32R
20681 This command resets the SDI connection.
20685 This command shows the SDI connection status.
20688 @kindex debug_chaos
20689 @cindex M32R/Chaos debugging
20690 Instructs the remote that M32R/Chaos debugging is to be used.
20692 @item use_debug_dma
20693 @kindex use_debug_dma
20694 Instructs the remote to use the DEBUG_DMA method of accessing memory.
20697 @kindex use_mon_code
20698 Instructs the remote to use the MON_CODE method of accessing memory.
20701 @kindex use_ib_break
20702 Instructs the remote to set breakpoints by IB break.
20704 @item use_dbt_break
20705 @kindex use_dbt_break
20706 Instructs the remote to set breakpoints by DBT.
20712 The Motorola m68k configuration includes ColdFire support, and a
20713 target command for the following ROM monitor.
20717 @kindex target dbug
20718 @item target dbug @var{dev}
20719 dBUG ROM monitor for Motorola ColdFire.
20724 @subsection MicroBlaze
20725 @cindex Xilinx MicroBlaze
20726 @cindex XMD, Xilinx Microprocessor Debugger
20728 The MicroBlaze is a soft-core processor supported on various Xilinx
20729 FPGAs, such as Spartan or Virtex series. Boards with these processors
20730 usually have JTAG ports which connect to a host system running the Xilinx
20731 Embedded Development Kit (EDK) or Software Development Kit (SDK).
20732 This host system is used to download the configuration bitstream to
20733 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
20734 communicates with the target board using the JTAG interface and
20735 presents a @code{gdbserver} interface to the board. By default
20736 @code{xmd} uses port @code{1234}. (While it is possible to change
20737 this default port, it requires the use of undocumented @code{xmd}
20738 commands. Contact Xilinx support if you need to do this.)
20740 Use these GDB commands to connect to the MicroBlaze target processor.
20743 @item target remote :1234
20744 Use this command to connect to the target if you are running @value{GDBN}
20745 on the same system as @code{xmd}.
20747 @item target remote @var{xmd-host}:1234
20748 Use this command to connect to the target if it is connected to @code{xmd}
20749 running on a different system named @var{xmd-host}.
20752 Use this command to download a program to the MicroBlaze target.
20754 @item set debug microblaze @var{n}
20755 Enable MicroBlaze-specific debugging messages if non-zero.
20757 @item show debug microblaze @var{n}
20758 Show MicroBlaze-specific debugging level.
20761 @node MIPS Embedded
20762 @subsection @acronym{MIPS} Embedded
20764 @cindex @acronym{MIPS} boards
20765 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
20766 @acronym{MIPS} board attached to a serial line. This is available when
20767 you configure @value{GDBN} with @samp{--target=mips-elf}.
20770 Use these @value{GDBN} commands to specify the connection to your target board:
20773 @item target mips @var{port}
20774 @kindex target mips @var{port}
20775 To run a program on the board, start up @code{@value{GDBP}} with the
20776 name of your program as the argument. To connect to the board, use the
20777 command @samp{target mips @var{port}}, where @var{port} is the name of
20778 the serial port connected to the board. If the program has not already
20779 been downloaded to the board, you may use the @code{load} command to
20780 download it. You can then use all the usual @value{GDBN} commands.
20782 For example, this sequence connects to the target board through a serial
20783 port, and loads and runs a program called @var{prog} through the
20787 host$ @value{GDBP} @var{prog}
20788 @value{GDBN} is free software and @dots{}
20789 (@value{GDBP}) target mips /dev/ttyb
20790 (@value{GDBP}) load @var{prog}
20794 @item target mips @var{hostname}:@var{portnumber}
20795 On some @value{GDBN} host configurations, you can specify a TCP
20796 connection (for instance, to a serial line managed by a terminal
20797 concentrator) instead of a serial port, using the syntax
20798 @samp{@var{hostname}:@var{portnumber}}.
20800 @item target pmon @var{port}
20801 @kindex target pmon @var{port}
20804 @item target ddb @var{port}
20805 @kindex target ddb @var{port}
20806 NEC's DDB variant of PMON for Vr4300.
20808 @item target lsi @var{port}
20809 @kindex target lsi @var{port}
20810 LSI variant of PMON.
20812 @kindex target r3900
20813 @item target r3900 @var{dev}
20814 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
20816 @kindex target array
20817 @item target array @var{dev}
20818 Array Tech LSI33K RAID controller board.
20824 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
20827 @item set mipsfpu double
20828 @itemx set mipsfpu single
20829 @itemx set mipsfpu none
20830 @itemx set mipsfpu auto
20831 @itemx show mipsfpu
20832 @kindex set mipsfpu
20833 @kindex show mipsfpu
20834 @cindex @acronym{MIPS} remote floating point
20835 @cindex floating point, @acronym{MIPS} remote
20836 If your target board does not support the @acronym{MIPS} floating point
20837 coprocessor, you should use the command @samp{set mipsfpu none} (if you
20838 need this, you may wish to put the command in your @value{GDBN} init
20839 file). This tells @value{GDBN} how to find the return value of
20840 functions which return floating point values. It also allows
20841 @value{GDBN} to avoid saving the floating point registers when calling
20842 functions on the board. If you are using a floating point coprocessor
20843 with only single precision floating point support, as on the @sc{r4650}
20844 processor, use the command @samp{set mipsfpu single}. The default
20845 double precision floating point coprocessor may be selected using
20846 @samp{set mipsfpu double}.
20848 In previous versions the only choices were double precision or no
20849 floating point, so @samp{set mipsfpu on} will select double precision
20850 and @samp{set mipsfpu off} will select no floating point.
20852 As usual, you can inquire about the @code{mipsfpu} variable with
20853 @samp{show mipsfpu}.
20855 @item set timeout @var{seconds}
20856 @itemx set retransmit-timeout @var{seconds}
20857 @itemx show timeout
20858 @itemx show retransmit-timeout
20859 @cindex @code{timeout}, @acronym{MIPS} protocol
20860 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
20861 @kindex set timeout
20862 @kindex show timeout
20863 @kindex set retransmit-timeout
20864 @kindex show retransmit-timeout
20865 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
20866 remote protocol, with the @code{set timeout @var{seconds}} command. The
20867 default is 5 seconds. Similarly, you can control the timeout used while
20868 waiting for an acknowledgment of a packet with the @code{set
20869 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
20870 You can inspect both values with @code{show timeout} and @code{show
20871 retransmit-timeout}. (These commands are @emph{only} available when
20872 @value{GDBN} is configured for @samp{--target=mips-elf}.)
20874 The timeout set by @code{set timeout} does not apply when @value{GDBN}
20875 is waiting for your program to stop. In that case, @value{GDBN} waits
20876 forever because it has no way of knowing how long the program is going
20877 to run before stopping.
20879 @item set syn-garbage-limit @var{num}
20880 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
20881 @cindex synchronize with remote @acronym{MIPS} target
20882 Limit the maximum number of characters @value{GDBN} should ignore when
20883 it tries to synchronize with the remote target. The default is 10
20884 characters. Setting the limit to -1 means there's no limit.
20886 @item show syn-garbage-limit
20887 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
20888 Show the current limit on the number of characters to ignore when
20889 trying to synchronize with the remote system.
20891 @item set monitor-prompt @var{prompt}
20892 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
20893 @cindex remote monitor prompt
20894 Tell @value{GDBN} to expect the specified @var{prompt} string from the
20895 remote monitor. The default depends on the target:
20905 @item show monitor-prompt
20906 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
20907 Show the current strings @value{GDBN} expects as the prompt from the
20910 @item set monitor-warnings
20911 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
20912 Enable or disable monitor warnings about hardware breakpoints. This
20913 has effect only for the @code{lsi} target. When on, @value{GDBN} will
20914 display warning messages whose codes are returned by the @code{lsi}
20915 PMON monitor for breakpoint commands.
20917 @item show monitor-warnings
20918 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
20919 Show the current setting of printing monitor warnings.
20921 @item pmon @var{command}
20922 @kindex pmon@r{, @acronym{MIPS} remote}
20923 @cindex send PMON command
20924 This command allows sending an arbitrary @var{command} string to the
20925 monitor. The monitor must be in debug mode for this to work.
20928 @node PowerPC Embedded
20929 @subsection PowerPC Embedded
20931 @cindex DVC register
20932 @value{GDBN} supports using the DVC (Data Value Compare) register to
20933 implement in hardware simple hardware watchpoint conditions of the form:
20936 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
20937 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
20940 The DVC register will be automatically used when @value{GDBN} detects
20941 such pattern in a condition expression, and the created watchpoint uses one
20942 debug register (either the @code{exact-watchpoints} option is on and the
20943 variable is scalar, or the variable has a length of one byte). This feature
20944 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
20947 When running on PowerPC embedded processors, @value{GDBN} automatically uses
20948 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
20949 in which case watchpoints using only one debug register are created when
20950 watching variables of scalar types.
20952 You can create an artificial array to watch an arbitrary memory
20953 region using one of the following commands (@pxref{Expressions}):
20956 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
20957 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
20960 PowerPC embedded processors support masked watchpoints. See the discussion
20961 about the @code{mask} argument in @ref{Set Watchpoints}.
20963 @cindex ranged breakpoint
20964 PowerPC embedded processors support hardware accelerated
20965 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
20966 the inferior whenever it executes an instruction at any address within
20967 the range it specifies. To set a ranged breakpoint in @value{GDBN},
20968 use the @code{break-range} command.
20970 @value{GDBN} provides the following PowerPC-specific commands:
20973 @kindex break-range
20974 @item break-range @var{start-location}, @var{end-location}
20975 Set a breakpoint for an address range.
20976 @var{start-location} and @var{end-location} can specify a function name,
20977 a line number, an offset of lines from the current line or from the start
20978 location, or an address of an instruction (see @ref{Specify Location},
20979 for a list of all the possible ways to specify a @var{location}.)
20980 The breakpoint will stop execution of the inferior whenever it
20981 executes an instruction at any address within the specified range,
20982 (including @var{start-location} and @var{end-location}.)
20984 @kindex set powerpc
20985 @item set powerpc soft-float
20986 @itemx show powerpc soft-float
20987 Force @value{GDBN} to use (or not use) a software floating point calling
20988 convention. By default, @value{GDBN} selects the calling convention based
20989 on the selected architecture and the provided executable file.
20991 @item set powerpc vector-abi
20992 @itemx show powerpc vector-abi
20993 Force @value{GDBN} to use the specified calling convention for vector
20994 arguments and return values. The valid options are @samp{auto};
20995 @samp{generic}, to avoid vector registers even if they are present;
20996 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
20997 registers. By default, @value{GDBN} selects the calling convention
20998 based on the selected architecture and the provided executable file.
21000 @item set powerpc exact-watchpoints
21001 @itemx show powerpc exact-watchpoints
21002 Allow @value{GDBN} to use only one debug register when watching a variable
21003 of scalar type, thus assuming that the variable is accessed through the
21004 address of its first byte.
21006 @kindex target dink32
21007 @item target dink32 @var{dev}
21008 DINK32 ROM monitor.
21010 @kindex target ppcbug
21011 @item target ppcbug @var{dev}
21012 @kindex target ppcbug1
21013 @item target ppcbug1 @var{dev}
21014 PPCBUG ROM monitor for PowerPC.
21017 @item target sds @var{dev}
21018 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
21021 @cindex SDS protocol
21022 The following commands specific to the SDS protocol are supported
21026 @item set sdstimeout @var{nsec}
21027 @kindex set sdstimeout
21028 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
21029 default is 2 seconds.
21031 @item show sdstimeout
21032 @kindex show sdstimeout
21033 Show the current value of the SDS timeout.
21035 @item sds @var{command}
21036 @kindex sds@r{, a command}
21037 Send the specified @var{command} string to the SDS monitor.
21042 @subsection HP PA Embedded
21046 @kindex target op50n
21047 @item target op50n @var{dev}
21048 OP50N monitor, running on an OKI HPPA board.
21050 @kindex target w89k
21051 @item target w89k @var{dev}
21052 W89K monitor, running on a Winbond HPPA board.
21057 @subsection Tsqware Sparclet
21061 @value{GDBN} enables developers to debug tasks running on
21062 Sparclet targets from a Unix host.
21063 @value{GDBN} uses code that runs on
21064 both the Unix host and on the Sparclet target. The program
21065 @code{@value{GDBP}} is installed and executed on the Unix host.
21068 @item remotetimeout @var{args}
21069 @kindex remotetimeout
21070 @value{GDBN} supports the option @code{remotetimeout}.
21071 This option is set by the user, and @var{args} represents the number of
21072 seconds @value{GDBN} waits for responses.
21075 @cindex compiling, on Sparclet
21076 When compiling for debugging, include the options @samp{-g} to get debug
21077 information and @samp{-Ttext} to relocate the program to where you wish to
21078 load it on the target. You may also want to add the options @samp{-n} or
21079 @samp{-N} in order to reduce the size of the sections. Example:
21082 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
21085 You can use @code{objdump} to verify that the addresses are what you intended:
21088 sparclet-aout-objdump --headers --syms prog
21091 @cindex running, on Sparclet
21093 your Unix execution search path to find @value{GDBN}, you are ready to
21094 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
21095 (or @code{sparclet-aout-gdb}, depending on your installation).
21097 @value{GDBN} comes up showing the prompt:
21104 * Sparclet File:: Setting the file to debug
21105 * Sparclet Connection:: Connecting to Sparclet
21106 * Sparclet Download:: Sparclet download
21107 * Sparclet Execution:: Running and debugging
21110 @node Sparclet File
21111 @subsubsection Setting File to Debug
21113 The @value{GDBN} command @code{file} lets you choose with program to debug.
21116 (gdbslet) file prog
21120 @value{GDBN} then attempts to read the symbol table of @file{prog}.
21121 @value{GDBN} locates
21122 the file by searching the directories listed in the command search
21124 If the file was compiled with debug information (option @samp{-g}), source
21125 files will be searched as well.
21126 @value{GDBN} locates
21127 the source files by searching the directories listed in the directory search
21128 path (@pxref{Environment, ,Your Program's Environment}).
21130 to find a file, it displays a message such as:
21133 prog: No such file or directory.
21136 When this happens, add the appropriate directories to the search paths with
21137 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
21138 @code{target} command again.
21140 @node Sparclet Connection
21141 @subsubsection Connecting to Sparclet
21143 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
21144 To connect to a target on serial port ``@code{ttya}'', type:
21147 (gdbslet) target sparclet /dev/ttya
21148 Remote target sparclet connected to /dev/ttya
21149 main () at ../prog.c:3
21153 @value{GDBN} displays messages like these:
21159 @node Sparclet Download
21160 @subsubsection Sparclet Download
21162 @cindex download to Sparclet
21163 Once connected to the Sparclet target,
21164 you can use the @value{GDBN}
21165 @code{load} command to download the file from the host to the target.
21166 The file name and load offset should be given as arguments to the @code{load}
21168 Since the file format is aout, the program must be loaded to the starting
21169 address. You can use @code{objdump} to find out what this value is. The load
21170 offset is an offset which is added to the VMA (virtual memory address)
21171 of each of the file's sections.
21172 For instance, if the program
21173 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
21174 and bss at 0x12010170, in @value{GDBN}, type:
21177 (gdbslet) load prog 0x12010000
21178 Loading section .text, size 0xdb0 vma 0x12010000
21181 If the code is loaded at a different address then what the program was linked
21182 to, you may need to use the @code{section} and @code{add-symbol-file} commands
21183 to tell @value{GDBN} where to map the symbol table.
21185 @node Sparclet Execution
21186 @subsubsection Running and Debugging
21188 @cindex running and debugging Sparclet programs
21189 You can now begin debugging the task using @value{GDBN}'s execution control
21190 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
21191 manual for the list of commands.
21195 Breakpoint 1 at 0x12010000: file prog.c, line 3.
21197 Starting program: prog
21198 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
21199 3 char *symarg = 0;
21201 4 char *execarg = "hello!";
21206 @subsection Fujitsu Sparclite
21210 @kindex target sparclite
21211 @item target sparclite @var{dev}
21212 Fujitsu sparclite boards, used only for the purpose of loading.
21213 You must use an additional command to debug the program.
21214 For example: target remote @var{dev} using @value{GDBN} standard
21220 @subsection Zilog Z8000
21223 @cindex simulator, Z8000
21224 @cindex Zilog Z8000 simulator
21226 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
21229 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
21230 unsegmented variant of the Z8000 architecture) or the Z8001 (the
21231 segmented variant). The simulator recognizes which architecture is
21232 appropriate by inspecting the object code.
21235 @item target sim @var{args}
21237 @kindex target sim@r{, with Z8000}
21238 Debug programs on a simulated CPU. If the simulator supports setup
21239 options, specify them via @var{args}.
21243 After specifying this target, you can debug programs for the simulated
21244 CPU in the same style as programs for your host computer; use the
21245 @code{file} command to load a new program image, the @code{run} command
21246 to run your program, and so on.
21248 As well as making available all the usual machine registers
21249 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
21250 additional items of information as specially named registers:
21255 Counts clock-ticks in the simulator.
21258 Counts instructions run in the simulator.
21261 Execution time in 60ths of a second.
21265 You can refer to these values in @value{GDBN} expressions with the usual
21266 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
21267 conditional breakpoint that suspends only after at least 5000
21268 simulated clock ticks.
21271 @subsection Atmel AVR
21274 When configured for debugging the Atmel AVR, @value{GDBN} supports the
21275 following AVR-specific commands:
21278 @item info io_registers
21279 @kindex info io_registers@r{, AVR}
21280 @cindex I/O registers (Atmel AVR)
21281 This command displays information about the AVR I/O registers. For
21282 each register, @value{GDBN} prints its number and value.
21289 When configured for debugging CRIS, @value{GDBN} provides the
21290 following CRIS-specific commands:
21293 @item set cris-version @var{ver}
21294 @cindex CRIS version
21295 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
21296 The CRIS version affects register names and sizes. This command is useful in
21297 case autodetection of the CRIS version fails.
21299 @item show cris-version
21300 Show the current CRIS version.
21302 @item set cris-dwarf2-cfi
21303 @cindex DWARF-2 CFI and CRIS
21304 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
21305 Change to @samp{off} when using @code{gcc-cris} whose version is below
21308 @item show cris-dwarf2-cfi
21309 Show the current state of using DWARF-2 CFI.
21311 @item set cris-mode @var{mode}
21313 Set the current CRIS mode to @var{mode}. It should only be changed when
21314 debugging in guru mode, in which case it should be set to
21315 @samp{guru} (the default is @samp{normal}).
21317 @item show cris-mode
21318 Show the current CRIS mode.
21322 @subsection Renesas Super-H
21325 For the Renesas Super-H processor, @value{GDBN} provides these
21329 @item set sh calling-convention @var{convention}
21330 @kindex set sh calling-convention
21331 Set the calling-convention used when calling functions from @value{GDBN}.
21332 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
21333 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
21334 convention. If the DWARF-2 information of the called function specifies
21335 that the function follows the Renesas calling convention, the function
21336 is called using the Renesas calling convention. If the calling convention
21337 is set to @samp{renesas}, the Renesas calling convention is always used,
21338 regardless of the DWARF-2 information. This can be used to override the
21339 default of @samp{gcc} if debug information is missing, or the compiler
21340 does not emit the DWARF-2 calling convention entry for a function.
21342 @item show sh calling-convention
21343 @kindex show sh calling-convention
21344 Show the current calling convention setting.
21349 @node Architectures
21350 @section Architectures
21352 This section describes characteristics of architectures that affect
21353 all uses of @value{GDBN} with the architecture, both native and cross.
21360 * HPPA:: HP PA architecture
21361 * SPU:: Cell Broadband Engine SPU architecture
21367 @subsection AArch64
21368 @cindex AArch64 support
21370 When @value{GDBN} is debugging the AArch64 architecture, it provides the
21371 following special commands:
21374 @item set debug aarch64
21375 @kindex set debug aarch64
21376 This command determines whether AArch64 architecture-specific debugging
21377 messages are to be displayed.
21379 @item show debug aarch64
21380 Show whether AArch64 debugging messages are displayed.
21385 @subsection x86 Architecture-specific Issues
21388 @item set struct-convention @var{mode}
21389 @kindex set struct-convention
21390 @cindex struct return convention
21391 @cindex struct/union returned in registers
21392 Set the convention used by the inferior to return @code{struct}s and
21393 @code{union}s from functions to @var{mode}. Possible values of
21394 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
21395 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
21396 are returned on the stack, while @code{"reg"} means that a
21397 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
21398 be returned in a register.
21400 @item show struct-convention
21401 @kindex show struct-convention
21402 Show the current setting of the convention to return @code{struct}s
21406 @subsubsection Intel(R) @dfn{Memory Protection Extensions} (MPX).
21407 @cindex Intel(R) Memory Protection Extensions (MPX).
21409 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
21410 @footnote{The register named with capital letters represent the architecture
21411 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
21412 which are the lower bound and upper bound. Bounds are effective addresses or
21413 memory locations. The upper bounds are architecturally represented in 1's
21414 complement form. A bound having lower bound = 0, and upper bound = 0
21415 (1's complement of all bits set) will allow access to the entire address space.
21417 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
21418 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
21419 display the upper bound performing the complement of one operation on the
21420 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
21421 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
21422 can also be noted that the upper bounds are inclusive.
21424 As an example, assume that the register BND0 holds bounds for a pointer having
21425 access allowed for the range between 0x32 and 0x71. The values present on
21426 bnd0raw and bnd registers are presented as follows:
21429 bnd0raw = @{0x32, 0xffffffff8e@}
21430 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
21433 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
21434 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
21435 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
21436 Python, the display includes the memory size, in bits, accessible to
21442 See the following section.
21445 @subsection @acronym{MIPS}
21447 @cindex stack on Alpha
21448 @cindex stack on @acronym{MIPS}
21449 @cindex Alpha stack
21450 @cindex @acronym{MIPS} stack
21451 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
21452 sometimes requires @value{GDBN} to search backward in the object code to
21453 find the beginning of a function.
21455 @cindex response time, @acronym{MIPS} debugging
21456 To improve response time (especially for embedded applications, where
21457 @value{GDBN} may be restricted to a slow serial line for this search)
21458 you may want to limit the size of this search, using one of these
21462 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
21463 @item set heuristic-fence-post @var{limit}
21464 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
21465 search for the beginning of a function. A value of @var{0} (the
21466 default) means there is no limit. However, except for @var{0}, the
21467 larger the limit the more bytes @code{heuristic-fence-post} must search
21468 and therefore the longer it takes to run. You should only need to use
21469 this command when debugging a stripped executable.
21471 @item show heuristic-fence-post
21472 Display the current limit.
21476 These commands are available @emph{only} when @value{GDBN} is configured
21477 for debugging programs on Alpha or @acronym{MIPS} processors.
21479 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
21483 @item set mips abi @var{arg}
21484 @kindex set mips abi
21485 @cindex set ABI for @acronym{MIPS}
21486 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
21487 values of @var{arg} are:
21491 The default ABI associated with the current binary (this is the
21501 @item show mips abi
21502 @kindex show mips abi
21503 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
21505 @item set mips compression @var{arg}
21506 @kindex set mips compression
21507 @cindex code compression, @acronym{MIPS}
21508 Tell @value{GDBN} which @acronym{MIPS} compressed
21509 @acronym{ISA, Instruction Set Architecture} encoding is used by the
21510 inferior. @value{GDBN} uses this for code disassembly and other
21511 internal interpretation purposes. This setting is only referred to
21512 when no executable has been associated with the debugging session or
21513 the executable does not provide information about the encoding it uses.
21514 Otherwise this setting is automatically updated from information
21515 provided by the executable.
21517 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
21518 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
21519 executables containing @acronym{MIPS16} code frequently are not
21520 identified as such.
21522 This setting is ``sticky''; that is, it retains its value across
21523 debugging sessions until reset either explicitly with this command or
21524 implicitly from an executable.
21526 The compiler and/or assembler typically add symbol table annotations to
21527 identify functions compiled for the @acronym{MIPS16} or
21528 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
21529 are present, @value{GDBN} uses them in preference to the global
21530 compressed @acronym{ISA} encoding setting.
21532 @item show mips compression
21533 @kindex show mips compression
21534 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
21535 @value{GDBN} to debug the inferior.
21538 @itemx show mipsfpu
21539 @xref{MIPS Embedded, set mipsfpu}.
21541 @item set mips mask-address @var{arg}
21542 @kindex set mips mask-address
21543 @cindex @acronym{MIPS} addresses, masking
21544 This command determines whether the most-significant 32 bits of 64-bit
21545 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
21546 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
21547 setting, which lets @value{GDBN} determine the correct value.
21549 @item show mips mask-address
21550 @kindex show mips mask-address
21551 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
21554 @item set remote-mips64-transfers-32bit-regs
21555 @kindex set remote-mips64-transfers-32bit-regs
21556 This command controls compatibility with 64-bit @acronym{MIPS} targets that
21557 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
21558 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
21559 and 64 bits for other registers, set this option to @samp{on}.
21561 @item show remote-mips64-transfers-32bit-regs
21562 @kindex show remote-mips64-transfers-32bit-regs
21563 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
21565 @item set debug mips
21566 @kindex set debug mips
21567 This command turns on and off debugging messages for the @acronym{MIPS}-specific
21568 target code in @value{GDBN}.
21570 @item show debug mips
21571 @kindex show debug mips
21572 Show the current setting of @acronym{MIPS} debugging messages.
21578 @cindex HPPA support
21580 When @value{GDBN} is debugging the HP PA architecture, it provides the
21581 following special commands:
21584 @item set debug hppa
21585 @kindex set debug hppa
21586 This command determines whether HPPA architecture-specific debugging
21587 messages are to be displayed.
21589 @item show debug hppa
21590 Show whether HPPA debugging messages are displayed.
21592 @item maint print unwind @var{address}
21593 @kindex maint print unwind@r{, HPPA}
21594 This command displays the contents of the unwind table entry at the
21595 given @var{address}.
21601 @subsection Cell Broadband Engine SPU architecture
21602 @cindex Cell Broadband Engine
21605 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
21606 it provides the following special commands:
21609 @item info spu event
21611 Display SPU event facility status. Shows current event mask
21612 and pending event status.
21614 @item info spu signal
21615 Display SPU signal notification facility status. Shows pending
21616 signal-control word and signal notification mode of both signal
21617 notification channels.
21619 @item info spu mailbox
21620 Display SPU mailbox facility status. Shows all pending entries,
21621 in order of processing, in each of the SPU Write Outbound,
21622 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
21625 Display MFC DMA status. Shows all pending commands in the MFC
21626 DMA queue. For each entry, opcode, tag, class IDs, effective
21627 and local store addresses and transfer size are shown.
21629 @item info spu proxydma
21630 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
21631 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
21632 and local store addresses and transfer size are shown.
21636 When @value{GDBN} is debugging a combined PowerPC/SPU application
21637 on the Cell Broadband Engine, it provides in addition the following
21641 @item set spu stop-on-load @var{arg}
21643 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
21644 will give control to the user when a new SPE thread enters its @code{main}
21645 function. The default is @code{off}.
21647 @item show spu stop-on-load
21649 Show whether to stop for new SPE threads.
21651 @item set spu auto-flush-cache @var{arg}
21652 Set whether to automatically flush the software-managed cache. When set to
21653 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
21654 cache to be flushed whenever SPE execution stops. This provides a consistent
21655 view of PowerPC memory that is accessed via the cache. If an application
21656 does not use the software-managed cache, this option has no effect.
21658 @item show spu auto-flush-cache
21659 Show whether to automatically flush the software-managed cache.
21664 @subsection PowerPC
21665 @cindex PowerPC architecture
21667 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
21668 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
21669 numbers stored in the floating point registers. These values must be stored
21670 in two consecutive registers, always starting at an even register like
21671 @code{f0} or @code{f2}.
21673 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
21674 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
21675 @code{f2} and @code{f3} for @code{$dl1} and so on.
21677 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
21678 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
21681 @subsection Nios II
21682 @cindex Nios II architecture
21684 When @value{GDBN} is debugging the Nios II architecture,
21685 it provides the following special commands:
21689 @item set debug nios2
21690 @kindex set debug nios2
21691 This command turns on and off debugging messages for the Nios II
21692 target code in @value{GDBN}.
21694 @item show debug nios2
21695 @kindex show debug nios2
21696 Show the current setting of Nios II debugging messages.
21699 @node Controlling GDB
21700 @chapter Controlling @value{GDBN}
21702 You can alter the way @value{GDBN} interacts with you by using the
21703 @code{set} command. For commands controlling how @value{GDBN} displays
21704 data, see @ref{Print Settings, ,Print Settings}. Other settings are
21709 * Editing:: Command editing
21710 * Command History:: Command history
21711 * Screen Size:: Screen size
21712 * Numbers:: Numbers
21713 * ABI:: Configuring the current ABI
21714 * Auto-loading:: Automatically loading associated files
21715 * Messages/Warnings:: Optional warnings and messages
21716 * Debugging Output:: Optional messages about internal happenings
21717 * Other Misc Settings:: Other Miscellaneous Settings
21725 @value{GDBN} indicates its readiness to read a command by printing a string
21726 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
21727 can change the prompt string with the @code{set prompt} command. For
21728 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
21729 the prompt in one of the @value{GDBN} sessions so that you can always tell
21730 which one you are talking to.
21732 @emph{Note:} @code{set prompt} does not add a space for you after the
21733 prompt you set. This allows you to set a prompt which ends in a space
21734 or a prompt that does not.
21738 @item set prompt @var{newprompt}
21739 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
21741 @kindex show prompt
21743 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
21746 Versions of @value{GDBN} that ship with Python scripting enabled have
21747 prompt extensions. The commands for interacting with these extensions
21751 @kindex set extended-prompt
21752 @item set extended-prompt @var{prompt}
21753 Set an extended prompt that allows for substitutions.
21754 @xref{gdb.prompt}, for a list of escape sequences that can be used for
21755 substitution. Any escape sequences specified as part of the prompt
21756 string are replaced with the corresponding strings each time the prompt
21762 set extended-prompt Current working directory: \w (gdb)
21765 Note that when an extended-prompt is set, it takes control of the
21766 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
21768 @kindex show extended-prompt
21769 @item show extended-prompt
21770 Prints the extended prompt. Any escape sequences specified as part of
21771 the prompt string with @code{set extended-prompt}, are replaced with the
21772 corresponding strings each time the prompt is displayed.
21776 @section Command Editing
21778 @cindex command line editing
21780 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
21781 @sc{gnu} library provides consistent behavior for programs which provide a
21782 command line interface to the user. Advantages are @sc{gnu} Emacs-style
21783 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
21784 substitution, and a storage and recall of command history across
21785 debugging sessions.
21787 You may control the behavior of command line editing in @value{GDBN} with the
21788 command @code{set}.
21791 @kindex set editing
21794 @itemx set editing on
21795 Enable command line editing (enabled by default).
21797 @item set editing off
21798 Disable command line editing.
21800 @kindex show editing
21802 Show whether command line editing is enabled.
21805 @ifset SYSTEM_READLINE
21806 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
21808 @ifclear SYSTEM_READLINE
21809 @xref{Command Line Editing},
21811 for more details about the Readline
21812 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
21813 encouraged to read that chapter.
21815 @node Command History
21816 @section Command History
21817 @cindex command history
21819 @value{GDBN} can keep track of the commands you type during your
21820 debugging sessions, so that you can be certain of precisely what
21821 happened. Use these commands to manage the @value{GDBN} command
21824 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
21825 package, to provide the history facility.
21826 @ifset SYSTEM_READLINE
21827 @xref{Using History Interactively, , , history, GNU History Library},
21829 @ifclear SYSTEM_READLINE
21830 @xref{Using History Interactively},
21832 for the detailed description of the History library.
21834 To issue a command to @value{GDBN} without affecting certain aspects of
21835 the state which is seen by users, prefix it with @samp{server }
21836 (@pxref{Server Prefix}). This
21837 means that this command will not affect the command history, nor will it
21838 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
21839 pressed on a line by itself.
21841 @cindex @code{server}, command prefix
21842 The server prefix does not affect the recording of values into the value
21843 history; to print a value without recording it into the value history,
21844 use the @code{output} command instead of the @code{print} command.
21846 Here is the description of @value{GDBN} commands related to command
21850 @cindex history substitution
21851 @cindex history file
21852 @kindex set history filename
21853 @cindex @env{GDBHISTFILE}, environment variable
21854 @item set history filename @var{fname}
21855 Set the name of the @value{GDBN} command history file to @var{fname}.
21856 This is the file where @value{GDBN} reads an initial command history
21857 list, and where it writes the command history from this session when it
21858 exits. You can access this list through history expansion or through
21859 the history command editing characters listed below. This file defaults
21860 to the value of the environment variable @code{GDBHISTFILE}, or to
21861 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
21864 @cindex save command history
21865 @kindex set history save
21866 @item set history save
21867 @itemx set history save on
21868 Record command history in a file, whose name may be specified with the
21869 @code{set history filename} command. By default, this option is disabled.
21871 @item set history save off
21872 Stop recording command history in a file.
21874 @cindex history size
21875 @kindex set history size
21876 @cindex @env{HISTSIZE}, environment variable
21877 @item set history size @var{size}
21878 @itemx set history size unlimited
21879 Set the number of commands which @value{GDBN} keeps in its history list.
21880 This defaults to the value of the environment variable
21881 @code{HISTSIZE}, or to 256 if this variable is not set. If @var{size}
21882 is @code{unlimited}, the number of commands @value{GDBN} keeps in the
21883 history list is unlimited.
21886 History expansion assigns special meaning to the character @kbd{!}.
21887 @ifset SYSTEM_READLINE
21888 @xref{Event Designators, , , history, GNU History Library},
21890 @ifclear SYSTEM_READLINE
21891 @xref{Event Designators},
21895 @cindex history expansion, turn on/off
21896 Since @kbd{!} is also the logical not operator in C, history expansion
21897 is off by default. If you decide to enable history expansion with the
21898 @code{set history expansion on} command, you may sometimes need to
21899 follow @kbd{!} (when it is used as logical not, in an expression) with
21900 a space or a tab to prevent it from being expanded. The readline
21901 history facilities do not attempt substitution on the strings
21902 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
21904 The commands to control history expansion are:
21907 @item set history expansion on
21908 @itemx set history expansion
21909 @kindex set history expansion
21910 Enable history expansion. History expansion is off by default.
21912 @item set history expansion off
21913 Disable history expansion.
21916 @kindex show history
21918 @itemx show history filename
21919 @itemx show history save
21920 @itemx show history size
21921 @itemx show history expansion
21922 These commands display the state of the @value{GDBN} history parameters.
21923 @code{show history} by itself displays all four states.
21928 @kindex show commands
21929 @cindex show last commands
21930 @cindex display command history
21931 @item show commands
21932 Display the last ten commands in the command history.
21934 @item show commands @var{n}
21935 Print ten commands centered on command number @var{n}.
21937 @item show commands +
21938 Print ten commands just after the commands last printed.
21942 @section Screen Size
21943 @cindex size of screen
21944 @cindex pauses in output
21946 Certain commands to @value{GDBN} may produce large amounts of
21947 information output to the screen. To help you read all of it,
21948 @value{GDBN} pauses and asks you for input at the end of each page of
21949 output. Type @key{RET} when you want to continue the output, or @kbd{q}
21950 to discard the remaining output. Also, the screen width setting
21951 determines when to wrap lines of output. Depending on what is being
21952 printed, @value{GDBN} tries to break the line at a readable place,
21953 rather than simply letting it overflow onto the following line.
21955 Normally @value{GDBN} knows the size of the screen from the terminal
21956 driver software. For example, on Unix @value{GDBN} uses the termcap data base
21957 together with the value of the @code{TERM} environment variable and the
21958 @code{stty rows} and @code{stty cols} settings. If this is not correct,
21959 you can override it with the @code{set height} and @code{set
21966 @kindex show height
21967 @item set height @var{lpp}
21968 @itemx set height unlimited
21970 @itemx set width @var{cpl}
21971 @itemx set width unlimited
21973 These @code{set} commands specify a screen height of @var{lpp} lines and
21974 a screen width of @var{cpl} characters. The associated @code{show}
21975 commands display the current settings.
21977 If you specify a height of either @code{unlimited} or zero lines,
21978 @value{GDBN} does not pause during output no matter how long the
21979 output is. This is useful if output is to a file or to an editor
21982 Likewise, you can specify @samp{set width unlimited} or @samp{set
21983 width 0} to prevent @value{GDBN} from wrapping its output.
21985 @item set pagination on
21986 @itemx set pagination off
21987 @kindex set pagination
21988 Turn the output pagination on or off; the default is on. Turning
21989 pagination off is the alternative to @code{set height unlimited}. Note that
21990 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
21991 Options, -batch}) also automatically disables pagination.
21993 @item show pagination
21994 @kindex show pagination
21995 Show the current pagination mode.
22000 @cindex number representation
22001 @cindex entering numbers
22003 You can always enter numbers in octal, decimal, or hexadecimal in
22004 @value{GDBN} by the usual conventions: octal numbers begin with
22005 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
22006 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
22007 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
22008 10; likewise, the default display for numbers---when no particular
22009 format is specified---is base 10. You can change the default base for
22010 both input and output with the commands described below.
22013 @kindex set input-radix
22014 @item set input-radix @var{base}
22015 Set the default base for numeric input. Supported choices
22016 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
22017 specified either unambiguously or using the current input radix; for
22021 set input-radix 012
22022 set input-radix 10.
22023 set input-radix 0xa
22027 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
22028 leaves the input radix unchanged, no matter what it was, since
22029 @samp{10}, being without any leading or trailing signs of its base, is
22030 interpreted in the current radix. Thus, if the current radix is 16,
22031 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
22034 @kindex set output-radix
22035 @item set output-radix @var{base}
22036 Set the default base for numeric display. Supported choices
22037 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
22038 specified either unambiguously or using the current input radix.
22040 @kindex show input-radix
22041 @item show input-radix
22042 Display the current default base for numeric input.
22044 @kindex show output-radix
22045 @item show output-radix
22046 Display the current default base for numeric display.
22048 @item set radix @r{[}@var{base}@r{]}
22052 These commands set and show the default base for both input and output
22053 of numbers. @code{set radix} sets the radix of input and output to
22054 the same base; without an argument, it resets the radix back to its
22055 default value of 10.
22060 @section Configuring the Current ABI
22062 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
22063 application automatically. However, sometimes you need to override its
22064 conclusions. Use these commands to manage @value{GDBN}'s view of the
22070 @cindex Newlib OS ABI and its influence on the longjmp handling
22072 One @value{GDBN} configuration can debug binaries for multiple operating
22073 system targets, either via remote debugging or native emulation.
22074 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
22075 but you can override its conclusion using the @code{set osabi} command.
22076 One example where this is useful is in debugging of binaries which use
22077 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
22078 not have the same identifying marks that the standard C library for your
22081 When @value{GDBN} is debugging the AArch64 architecture, it provides a
22082 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
22083 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
22084 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
22088 Show the OS ABI currently in use.
22091 With no argument, show the list of registered available OS ABI's.
22093 @item set osabi @var{abi}
22094 Set the current OS ABI to @var{abi}.
22097 @cindex float promotion
22099 Generally, the way that an argument of type @code{float} is passed to a
22100 function depends on whether the function is prototyped. For a prototyped
22101 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
22102 according to the architecture's convention for @code{float}. For unprototyped
22103 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
22104 @code{double} and then passed.
22106 Unfortunately, some forms of debug information do not reliably indicate whether
22107 a function is prototyped. If @value{GDBN} calls a function that is not marked
22108 as prototyped, it consults @kbd{set coerce-float-to-double}.
22111 @kindex set coerce-float-to-double
22112 @item set coerce-float-to-double
22113 @itemx set coerce-float-to-double on
22114 Arguments of type @code{float} will be promoted to @code{double} when passed
22115 to an unprototyped function. This is the default setting.
22117 @item set coerce-float-to-double off
22118 Arguments of type @code{float} will be passed directly to unprototyped
22121 @kindex show coerce-float-to-double
22122 @item show coerce-float-to-double
22123 Show the current setting of promoting @code{float} to @code{double}.
22127 @kindex show cp-abi
22128 @value{GDBN} needs to know the ABI used for your program's C@t{++}
22129 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
22130 used to build your application. @value{GDBN} only fully supports
22131 programs with a single C@t{++} ABI; if your program contains code using
22132 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
22133 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
22134 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
22135 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
22136 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
22137 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
22142 Show the C@t{++} ABI currently in use.
22145 With no argument, show the list of supported C@t{++} ABI's.
22147 @item set cp-abi @var{abi}
22148 @itemx set cp-abi auto
22149 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
22153 @section Automatically loading associated files
22154 @cindex auto-loading
22156 @value{GDBN} sometimes reads files with commands and settings automatically,
22157 without being explicitly told so by the user. We call this feature
22158 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
22159 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
22160 results or introduce security risks (e.g., if the file comes from untrusted
22164 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
22165 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
22167 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
22168 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
22171 There are various kinds of files @value{GDBN} can automatically load.
22172 In addition to these files, @value{GDBN} supports auto-loading code written
22173 in various extension languages. @xref{Auto-loading extensions}.
22175 Note that loading of these associated files (including the local @file{.gdbinit}
22176 file) requires accordingly configured @code{auto-load safe-path}
22177 (@pxref{Auto-loading safe path}).
22179 For these reasons, @value{GDBN} includes commands and options to let you
22180 control when to auto-load files and which files should be auto-loaded.
22183 @anchor{set auto-load off}
22184 @kindex set auto-load off
22185 @item set auto-load off
22186 Globally disable loading of all auto-loaded files.
22187 You may want to use this command with the @samp{-iex} option
22188 (@pxref{Option -init-eval-command}) such as:
22190 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
22193 Be aware that system init file (@pxref{System-wide configuration})
22194 and init files from your home directory (@pxref{Home Directory Init File})
22195 still get read (as they come from generally trusted directories).
22196 To prevent @value{GDBN} from auto-loading even those init files, use the
22197 @option{-nx} option (@pxref{Mode Options}), in addition to
22198 @code{set auto-load no}.
22200 @anchor{show auto-load}
22201 @kindex show auto-load
22202 @item show auto-load
22203 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
22207 (gdb) show auto-load
22208 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
22209 libthread-db: Auto-loading of inferior specific libthread_db is on.
22210 local-gdbinit: Auto-loading of .gdbinit script from current directory
22212 python-scripts: Auto-loading of Python scripts is on.
22213 safe-path: List of directories from which it is safe to auto-load files
22214 is $debugdir:$datadir/auto-load.
22215 scripts-directory: List of directories from which to load auto-loaded scripts
22216 is $debugdir:$datadir/auto-load.
22219 @anchor{info auto-load}
22220 @kindex info auto-load
22221 @item info auto-load
22222 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
22226 (gdb) info auto-load
22229 Yes /home/user/gdb/gdb-gdb.gdb
22230 libthread-db: No auto-loaded libthread-db.
22231 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
22235 Yes /home/user/gdb/gdb-gdb.py
22239 These are @value{GDBN} control commands for the auto-loading:
22241 @multitable @columnfractions .5 .5
22242 @item @xref{set auto-load off}.
22243 @tab Disable auto-loading globally.
22244 @item @xref{show auto-load}.
22245 @tab Show setting of all kinds of files.
22246 @item @xref{info auto-load}.
22247 @tab Show state of all kinds of files.
22248 @item @xref{set auto-load gdb-scripts}.
22249 @tab Control for @value{GDBN} command scripts.
22250 @item @xref{show auto-load gdb-scripts}.
22251 @tab Show setting of @value{GDBN} command scripts.
22252 @item @xref{info auto-load gdb-scripts}.
22253 @tab Show state of @value{GDBN} command scripts.
22254 @item @xref{set auto-load python-scripts}.
22255 @tab Control for @value{GDBN} Python scripts.
22256 @item @xref{show auto-load python-scripts}.
22257 @tab Show setting of @value{GDBN} Python scripts.
22258 @item @xref{info auto-load python-scripts}.
22259 @tab Show state of @value{GDBN} Python scripts.
22260 @item @xref{set auto-load scripts-directory}.
22261 @tab Control for @value{GDBN} auto-loaded scripts location.
22262 @item @xref{show auto-load scripts-directory}.
22263 @tab Show @value{GDBN} auto-loaded scripts location.
22264 @item @xref{set auto-load local-gdbinit}.
22265 @tab Control for init file in the current directory.
22266 @item @xref{show auto-load local-gdbinit}.
22267 @tab Show setting of init file in the current directory.
22268 @item @xref{info auto-load local-gdbinit}.
22269 @tab Show state of init file in the current directory.
22270 @item @xref{set auto-load libthread-db}.
22271 @tab Control for thread debugging library.
22272 @item @xref{show auto-load libthread-db}.
22273 @tab Show setting of thread debugging library.
22274 @item @xref{info auto-load libthread-db}.
22275 @tab Show state of thread debugging library.
22276 @item @xref{set auto-load safe-path}.
22277 @tab Control directories trusted for automatic loading.
22278 @item @xref{show auto-load safe-path}.
22279 @tab Show directories trusted for automatic loading.
22280 @item @xref{add-auto-load-safe-path}.
22281 @tab Add directory trusted for automatic loading.
22284 @node Init File in the Current Directory
22285 @subsection Automatically loading init file in the current directory
22286 @cindex auto-loading init file in the current directory
22288 By default, @value{GDBN} reads and executes the canned sequences of commands
22289 from init file (if any) in the current working directory,
22290 see @ref{Init File in the Current Directory during Startup}.
22292 Note that loading of this local @file{.gdbinit} file also requires accordingly
22293 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22296 @anchor{set auto-load local-gdbinit}
22297 @kindex set auto-load local-gdbinit
22298 @item set auto-load local-gdbinit [on|off]
22299 Enable or disable the auto-loading of canned sequences of commands
22300 (@pxref{Sequences}) found in init file in the current directory.
22302 @anchor{show auto-load local-gdbinit}
22303 @kindex show auto-load local-gdbinit
22304 @item show auto-load local-gdbinit
22305 Show whether auto-loading of canned sequences of commands from init file in the
22306 current directory is enabled or disabled.
22308 @anchor{info auto-load local-gdbinit}
22309 @kindex info auto-load local-gdbinit
22310 @item info auto-load local-gdbinit
22311 Print whether canned sequences of commands from init file in the
22312 current directory have been auto-loaded.
22315 @node libthread_db.so.1 file
22316 @subsection Automatically loading thread debugging library
22317 @cindex auto-loading libthread_db.so.1
22319 This feature is currently present only on @sc{gnu}/Linux native hosts.
22321 @value{GDBN} reads in some cases thread debugging library from places specific
22322 to the inferior (@pxref{set libthread-db-search-path}).
22324 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
22325 without checking this @samp{set auto-load libthread-db} switch as system
22326 libraries have to be trusted in general. In all other cases of
22327 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
22328 auto-load libthread-db} is enabled before trying to open such thread debugging
22331 Note that loading of this debugging library also requires accordingly configured
22332 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22335 @anchor{set auto-load libthread-db}
22336 @kindex set auto-load libthread-db
22337 @item set auto-load libthread-db [on|off]
22338 Enable or disable the auto-loading of inferior specific thread debugging library.
22340 @anchor{show auto-load libthread-db}
22341 @kindex show auto-load libthread-db
22342 @item show auto-load libthread-db
22343 Show whether auto-loading of inferior specific thread debugging library is
22344 enabled or disabled.
22346 @anchor{info auto-load libthread-db}
22347 @kindex info auto-load libthread-db
22348 @item info auto-load libthread-db
22349 Print the list of all loaded inferior specific thread debugging libraries and
22350 for each such library print list of inferior @var{pid}s using it.
22353 @node Auto-loading safe path
22354 @subsection Security restriction for auto-loading
22355 @cindex auto-loading safe-path
22357 As the files of inferior can come from untrusted source (such as submitted by
22358 an application user) @value{GDBN} does not always load any files automatically.
22359 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
22360 directories trusted for loading files not explicitly requested by user.
22361 Each directory can also be a shell wildcard pattern.
22363 If the path is not set properly you will see a warning and the file will not
22368 Reading symbols from /home/user/gdb/gdb...done.
22369 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
22370 declined by your `auto-load safe-path' set
22371 to "$debugdir:$datadir/auto-load".
22372 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
22373 declined by your `auto-load safe-path' set
22374 to "$debugdir:$datadir/auto-load".
22378 To instruct @value{GDBN} to go ahead and use the init files anyway,
22379 invoke @value{GDBN} like this:
22382 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
22385 The list of trusted directories is controlled by the following commands:
22388 @anchor{set auto-load safe-path}
22389 @kindex set auto-load safe-path
22390 @item set auto-load safe-path @r{[}@var{directories}@r{]}
22391 Set the list of directories (and their subdirectories) trusted for automatic
22392 loading and execution of scripts. You can also enter a specific trusted file.
22393 Each directory can also be a shell wildcard pattern; wildcards do not match
22394 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
22395 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
22396 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
22397 its default value as specified during @value{GDBN} compilation.
22399 The list of directories uses path separator (@samp{:} on GNU and Unix
22400 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
22401 to the @env{PATH} environment variable.
22403 @anchor{show auto-load safe-path}
22404 @kindex show auto-load safe-path
22405 @item show auto-load safe-path
22406 Show the list of directories trusted for automatic loading and execution of
22409 @anchor{add-auto-load-safe-path}
22410 @kindex add-auto-load-safe-path
22411 @item add-auto-load-safe-path
22412 Add an entry (or list of entries) the list of directories trusted for automatic
22413 loading and execution of scripts. Multiple entries may be delimited by the
22414 host platform path separator in use.
22417 This variable defaults to what @code{--with-auto-load-dir} has been configured
22418 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
22419 substitution applies the same as for @ref{set auto-load scripts-directory}.
22420 The default @code{set auto-load safe-path} value can be also overriden by
22421 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
22423 Setting this variable to @file{/} disables this security protection,
22424 corresponding @value{GDBN} configuration option is
22425 @option{--without-auto-load-safe-path}.
22426 This variable is supposed to be set to the system directories writable by the
22427 system superuser only. Users can add their source directories in init files in
22428 their home directories (@pxref{Home Directory Init File}). See also deprecated
22429 init file in the current directory
22430 (@pxref{Init File in the Current Directory during Startup}).
22432 To force @value{GDBN} to load the files it declined to load in the previous
22433 example, you could use one of the following ways:
22436 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
22437 Specify this trusted directory (or a file) as additional component of the list.
22438 You have to specify also any existing directories displayed by
22439 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
22441 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
22442 Specify this directory as in the previous case but just for a single
22443 @value{GDBN} session.
22445 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
22446 Disable auto-loading safety for a single @value{GDBN} session.
22447 This assumes all the files you debug during this @value{GDBN} session will come
22448 from trusted sources.
22450 @item @kbd{./configure --without-auto-load-safe-path}
22451 During compilation of @value{GDBN} you may disable any auto-loading safety.
22452 This assumes all the files you will ever debug with this @value{GDBN} come from
22456 On the other hand you can also explicitly forbid automatic files loading which
22457 also suppresses any such warning messages:
22460 @item @kbd{gdb -iex "set auto-load no" @dots{}}
22461 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
22463 @item @file{~/.gdbinit}: @samp{set auto-load no}
22464 Disable auto-loading globally for the user
22465 (@pxref{Home Directory Init File}). While it is improbable, you could also
22466 use system init file instead (@pxref{System-wide configuration}).
22469 This setting applies to the file names as entered by user. If no entry matches
22470 @value{GDBN} tries as a last resort to also resolve all the file names into
22471 their canonical form (typically resolving symbolic links) and compare the
22472 entries again. @value{GDBN} already canonicalizes most of the filenames on its
22473 own before starting the comparison so a canonical form of directories is
22474 recommended to be entered.
22476 @node Auto-loading verbose mode
22477 @subsection Displaying files tried for auto-load
22478 @cindex auto-loading verbose mode
22480 For better visibility of all the file locations where you can place scripts to
22481 be auto-loaded with inferior --- or to protect yourself against accidental
22482 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
22483 all the files attempted to be loaded. Both existing and non-existing files may
22486 For example the list of directories from which it is safe to auto-load files
22487 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
22488 may not be too obvious while setting it up.
22491 (gdb) set debug auto-load on
22492 (gdb) file ~/src/t/true
22493 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
22494 for objfile "/tmp/true".
22495 auto-load: Updating directories of "/usr:/opt".
22496 auto-load: Using directory "/usr".
22497 auto-load: Using directory "/opt".
22498 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
22499 by your `auto-load safe-path' set to "/usr:/opt".
22503 @anchor{set debug auto-load}
22504 @kindex set debug auto-load
22505 @item set debug auto-load [on|off]
22506 Set whether to print the filenames attempted to be auto-loaded.
22508 @anchor{show debug auto-load}
22509 @kindex show debug auto-load
22510 @item show debug auto-load
22511 Show whether printing of the filenames attempted to be auto-loaded is turned
22515 @node Messages/Warnings
22516 @section Optional Warnings and Messages
22518 @cindex verbose operation
22519 @cindex optional warnings
22520 By default, @value{GDBN} is silent about its inner workings. If you are
22521 running on a slow machine, you may want to use the @code{set verbose}
22522 command. This makes @value{GDBN} tell you when it does a lengthy
22523 internal operation, so you will not think it has crashed.
22525 Currently, the messages controlled by @code{set verbose} are those
22526 which announce that the symbol table for a source file is being read;
22527 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
22530 @kindex set verbose
22531 @item set verbose on
22532 Enables @value{GDBN} output of certain informational messages.
22534 @item set verbose off
22535 Disables @value{GDBN} output of certain informational messages.
22537 @kindex show verbose
22539 Displays whether @code{set verbose} is on or off.
22542 By default, if @value{GDBN} encounters bugs in the symbol table of an
22543 object file, it is silent; but if you are debugging a compiler, you may
22544 find this information useful (@pxref{Symbol Errors, ,Errors Reading
22549 @kindex set complaints
22550 @item set complaints @var{limit}
22551 Permits @value{GDBN} to output @var{limit} complaints about each type of
22552 unusual symbols before becoming silent about the problem. Set
22553 @var{limit} to zero to suppress all complaints; set it to a large number
22554 to prevent complaints from being suppressed.
22556 @kindex show complaints
22557 @item show complaints
22558 Displays how many symbol complaints @value{GDBN} is permitted to produce.
22562 @anchor{confirmation requests}
22563 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
22564 lot of stupid questions to confirm certain commands. For example, if
22565 you try to run a program which is already running:
22569 The program being debugged has been started already.
22570 Start it from the beginning? (y or n)
22573 If you are willing to unflinchingly face the consequences of your own
22574 commands, you can disable this ``feature'':
22578 @kindex set confirm
22580 @cindex confirmation
22581 @cindex stupid questions
22582 @item set confirm off
22583 Disables confirmation requests. Note that running @value{GDBN} with
22584 the @option{--batch} option (@pxref{Mode Options, -batch}) also
22585 automatically disables confirmation requests.
22587 @item set confirm on
22588 Enables confirmation requests (the default).
22590 @kindex show confirm
22592 Displays state of confirmation requests.
22596 @cindex command tracing
22597 If you need to debug user-defined commands or sourced files you may find it
22598 useful to enable @dfn{command tracing}. In this mode each command will be
22599 printed as it is executed, prefixed with one or more @samp{+} symbols, the
22600 quantity denoting the call depth of each command.
22603 @kindex set trace-commands
22604 @cindex command scripts, debugging
22605 @item set trace-commands on
22606 Enable command tracing.
22607 @item set trace-commands off
22608 Disable command tracing.
22609 @item show trace-commands
22610 Display the current state of command tracing.
22613 @node Debugging Output
22614 @section Optional Messages about Internal Happenings
22615 @cindex optional debugging messages
22617 @value{GDBN} has commands that enable optional debugging messages from
22618 various @value{GDBN} subsystems; normally these commands are of
22619 interest to @value{GDBN} maintainers, or when reporting a bug. This
22620 section documents those commands.
22623 @kindex set exec-done-display
22624 @item set exec-done-display
22625 Turns on or off the notification of asynchronous commands'
22626 completion. When on, @value{GDBN} will print a message when an
22627 asynchronous command finishes its execution. The default is off.
22628 @kindex show exec-done-display
22629 @item show exec-done-display
22630 Displays the current setting of asynchronous command completion
22633 @cindex ARM AArch64
22634 @item set debug aarch64
22635 Turns on or off display of debugging messages related to ARM AArch64.
22636 The default is off.
22638 @item show debug aarch64
22639 Displays the current state of displaying debugging messages related to
22641 @cindex gdbarch debugging info
22642 @cindex architecture debugging info
22643 @item set debug arch
22644 Turns on or off display of gdbarch debugging info. The default is off
22645 @item show debug arch
22646 Displays the current state of displaying gdbarch debugging info.
22647 @item set debug aix-solib
22648 @cindex AIX shared library debugging
22649 Control display of debugging messages from the AIX shared library
22650 support module. The default is off.
22651 @item show debug aix-thread
22652 Show the current state of displaying AIX shared library debugging messages.
22653 @item set debug aix-thread
22654 @cindex AIX threads
22655 Display debugging messages about inner workings of the AIX thread
22657 @item show debug aix-thread
22658 Show the current state of AIX thread debugging info display.
22659 @item set debug check-physname
22661 Check the results of the ``physname'' computation. When reading DWARF
22662 debugging information for C@t{++}, @value{GDBN} attempts to compute
22663 each entity's name. @value{GDBN} can do this computation in two
22664 different ways, depending on exactly what information is present.
22665 When enabled, this setting causes @value{GDBN} to compute the names
22666 both ways and display any discrepancies.
22667 @item show debug check-physname
22668 Show the current state of ``physname'' checking.
22669 @item set debug coff-pe-read
22670 @cindex COFF/PE exported symbols
22671 Control display of debugging messages related to reading of COFF/PE
22672 exported symbols. The default is off.
22673 @item show debug coff-pe-read
22674 Displays the current state of displaying debugging messages related to
22675 reading of COFF/PE exported symbols.
22676 @item set debug dwarf2-die
22677 @cindex DWARF2 DIEs
22678 Dump DWARF2 DIEs after they are read in.
22679 The value is the number of nesting levels to print.
22680 A value of zero turns off the display.
22681 @item show debug dwarf2-die
22682 Show the current state of DWARF2 DIE debugging.
22683 @item set debug dwarf2-read
22684 @cindex DWARF2 Reading
22685 Turns on or off display of debugging messages related to reading
22686 DWARF debug info. The default is 0 (off).
22687 A value of 1 provides basic information.
22688 A value greater than 1 provides more verbose information.
22689 @item show debug dwarf2-read
22690 Show the current state of DWARF2 reader debugging.
22691 @item set debug displaced
22692 @cindex displaced stepping debugging info
22693 Turns on or off display of @value{GDBN} debugging info for the
22694 displaced stepping support. The default is off.
22695 @item show debug displaced
22696 Displays the current state of displaying @value{GDBN} debugging info
22697 related to displaced stepping.
22698 @item set debug event
22699 @cindex event debugging info
22700 Turns on or off display of @value{GDBN} event debugging info. The
22702 @item show debug event
22703 Displays the current state of displaying @value{GDBN} event debugging
22705 @item set debug expression
22706 @cindex expression debugging info
22707 Turns on or off display of debugging info about @value{GDBN}
22708 expression parsing. The default is off.
22709 @item show debug expression
22710 Displays the current state of displaying debugging info about
22711 @value{GDBN} expression parsing.
22712 @item set debug frame
22713 @cindex frame debugging info
22714 Turns on or off display of @value{GDBN} frame debugging info. The
22716 @item show debug frame
22717 Displays the current state of displaying @value{GDBN} frame debugging
22719 @item set debug gnu-nat
22720 @cindex @sc{gnu}/Hurd debug messages
22721 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
22722 @item show debug gnu-nat
22723 Show the current state of @sc{gnu}/Hurd debugging messages.
22724 @item set debug infrun
22725 @cindex inferior debugging info
22726 Turns on or off display of @value{GDBN} debugging info for running the inferior.
22727 The default is off. @file{infrun.c} contains GDB's runtime state machine used
22728 for implementing operations such as single-stepping the inferior.
22729 @item show debug infrun
22730 Displays the current state of @value{GDBN} inferior debugging.
22731 @item set debug jit
22732 @cindex just-in-time compilation, debugging messages
22733 Turns on or off debugging messages from JIT debug support.
22734 @item show debug jit
22735 Displays the current state of @value{GDBN} JIT debugging.
22736 @item set debug lin-lwp
22737 @cindex @sc{gnu}/Linux LWP debug messages
22738 @cindex Linux lightweight processes
22739 Turns on or off debugging messages from the Linux LWP debug support.
22740 @item show debug lin-lwp
22741 Show the current state of Linux LWP debugging messages.
22742 @item set debug mach-o
22743 @cindex Mach-O symbols processing
22744 Control display of debugging messages related to Mach-O symbols
22745 processing. The default is off.
22746 @item show debug mach-o
22747 Displays the current state of displaying debugging messages related to
22748 reading of COFF/PE exported symbols.
22749 @item set debug notification
22750 @cindex remote async notification debugging info
22751 Turns on or off debugging messages about remote async notification.
22752 The default is off.
22753 @item show debug notification
22754 Displays the current state of remote async notification debugging messages.
22755 @item set debug observer
22756 @cindex observer debugging info
22757 Turns on or off display of @value{GDBN} observer debugging. This
22758 includes info such as the notification of observable events.
22759 @item show debug observer
22760 Displays the current state of observer debugging.
22761 @item set debug overload
22762 @cindex C@t{++} overload debugging info
22763 Turns on or off display of @value{GDBN} C@t{++} overload debugging
22764 info. This includes info such as ranking of functions, etc. The default
22766 @item show debug overload
22767 Displays the current state of displaying @value{GDBN} C@t{++} overload
22769 @cindex expression parser, debugging info
22770 @cindex debug expression parser
22771 @item set debug parser
22772 Turns on or off the display of expression parser debugging output.
22773 Internally, this sets the @code{yydebug} variable in the expression
22774 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
22775 details. The default is off.
22776 @item show debug parser
22777 Show the current state of expression parser debugging.
22778 @cindex packets, reporting on stdout
22779 @cindex serial connections, debugging
22780 @cindex debug remote protocol
22781 @cindex remote protocol debugging
22782 @cindex display remote packets
22783 @item set debug remote
22784 Turns on or off display of reports on all packets sent back and forth across
22785 the serial line to the remote machine. The info is printed on the
22786 @value{GDBN} standard output stream. The default is off.
22787 @item show debug remote
22788 Displays the state of display of remote packets.
22789 @item set debug serial
22790 Turns on or off display of @value{GDBN} serial debugging info. The
22792 @item show debug serial
22793 Displays the current state of displaying @value{GDBN} serial debugging
22795 @item set debug solib-frv
22796 @cindex FR-V shared-library debugging
22797 Turns on or off debugging messages for FR-V shared-library code.
22798 @item show debug solib-frv
22799 Display the current state of FR-V shared-library code debugging
22801 @item set debug symfile
22802 @cindex symbol file functions
22803 Turns on or off display of debugging messages related to symbol file functions.
22804 The default is off. @xref{Files}.
22805 @item show debug symfile
22806 Show the current state of symbol file debugging messages.
22807 @item set debug symtab-create
22808 @cindex symbol table creation
22809 Turns on or off display of debugging messages related to symbol table creation.
22810 The default is 0 (off).
22811 A value of 1 provides basic information.
22812 A value greater than 1 provides more verbose information.
22813 @item show debug symtab-create
22814 Show the current state of symbol table creation debugging.
22815 @item set debug target
22816 @cindex target debugging info
22817 Turns on or off display of @value{GDBN} target debugging info. This info
22818 includes what is going on at the target level of GDB, as it happens. The
22819 default is 0. Set it to 1 to track events, and to 2 to also track the
22820 value of large memory transfers. Changes to this flag do not take effect
22821 until the next time you connect to a target or use the @code{run} command.
22822 @item show debug target
22823 Displays the current state of displaying @value{GDBN} target debugging
22825 @item set debug timestamp
22826 @cindex timestampping debugging info
22827 Turns on or off display of timestamps with @value{GDBN} debugging info.
22828 When enabled, seconds and microseconds are displayed before each debugging
22830 @item show debug timestamp
22831 Displays the current state of displaying timestamps with @value{GDBN}
22833 @item set debugvarobj
22834 @cindex variable object debugging info
22835 Turns on or off display of @value{GDBN} variable object debugging
22836 info. The default is off.
22837 @item show debugvarobj
22838 Displays the current state of displaying @value{GDBN} variable object
22840 @item set debug xml
22841 @cindex XML parser debugging
22842 Turns on or off debugging messages for built-in XML parsers.
22843 @item show debug xml
22844 Displays the current state of XML debugging messages.
22847 @node Other Misc Settings
22848 @section Other Miscellaneous Settings
22849 @cindex miscellaneous settings
22852 @kindex set interactive-mode
22853 @item set interactive-mode
22854 If @code{on}, forces @value{GDBN} to assume that GDB was started
22855 in a terminal. In practice, this means that @value{GDBN} should wait
22856 for the user to answer queries generated by commands entered at
22857 the command prompt. If @code{off}, forces @value{GDBN} to operate
22858 in the opposite mode, and it uses the default answers to all queries.
22859 If @code{auto} (the default), @value{GDBN} tries to determine whether
22860 its standard input is a terminal, and works in interactive-mode if it
22861 is, non-interactively otherwise.
22863 In the vast majority of cases, the debugger should be able to guess
22864 correctly which mode should be used. But this setting can be useful
22865 in certain specific cases, such as running a MinGW @value{GDBN}
22866 inside a cygwin window.
22868 @kindex show interactive-mode
22869 @item show interactive-mode
22870 Displays whether the debugger is operating in interactive mode or not.
22873 @node Extending GDB
22874 @chapter Extending @value{GDBN}
22875 @cindex extending GDB
22877 @value{GDBN} provides several mechanisms for extension.
22878 @value{GDBN} also provides the ability to automatically load
22879 extensions when it reads a file for debugging. This allows the
22880 user to automatically customize @value{GDBN} for the program
22884 * Sequences:: Canned Sequences of @value{GDBN} Commands
22885 * Python:: Extending @value{GDBN} using Python
22886 * Auto-loading extensions:: Automatically loading extensions
22887 * Aliases:: Creating new spellings of existing commands
22890 To facilitate the use of extension languages, @value{GDBN} is capable
22891 of evaluating the contents of a file. When doing so, @value{GDBN}
22892 can recognize which extension language is being used by looking at
22893 the filename extension. Files with an unrecognized filename extension
22894 are always treated as a @value{GDBN} Command Files.
22895 @xref{Command Files,, Command files}.
22897 You can control how @value{GDBN} evaluates these files with the following
22901 @kindex set script-extension
22902 @kindex show script-extension
22903 @item set script-extension off
22904 All scripts are always evaluated as @value{GDBN} Command Files.
22906 @item set script-extension soft
22907 The debugger determines the scripting language based on filename
22908 extension. If this scripting language is supported, @value{GDBN}
22909 evaluates the script using that language. Otherwise, it evaluates
22910 the file as a @value{GDBN} Command File.
22912 @item set script-extension strict
22913 The debugger determines the scripting language based on filename
22914 extension, and evaluates the script using that language. If the
22915 language is not supported, then the evaluation fails.
22917 @item show script-extension
22918 Display the current value of the @code{script-extension} option.
22923 @section Canned Sequences of Commands
22925 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
22926 Command Lists}), @value{GDBN} provides two ways to store sequences of
22927 commands for execution as a unit: user-defined commands and command
22931 * Define:: How to define your own commands
22932 * Hooks:: Hooks for user-defined commands
22933 * Command Files:: How to write scripts of commands to be stored in a file
22934 * Output:: Commands for controlled output
22935 * Auto-loading sequences:: Controlling auto-loaded command files
22939 @subsection User-defined Commands
22941 @cindex user-defined command
22942 @cindex arguments, to user-defined commands
22943 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
22944 which you assign a new name as a command. This is done with the
22945 @code{define} command. User commands may accept up to 10 arguments
22946 separated by whitespace. Arguments are accessed within the user command
22947 via @code{$arg0@dots{}$arg9}. A trivial example:
22951 print $arg0 + $arg1 + $arg2
22956 To execute the command use:
22963 This defines the command @code{adder}, which prints the sum of
22964 its three arguments. Note the arguments are text substitutions, so they may
22965 reference variables, use complex expressions, or even perform inferior
22968 @cindex argument count in user-defined commands
22969 @cindex how many arguments (user-defined commands)
22970 In addition, @code{$argc} may be used to find out how many arguments have
22971 been passed. This expands to a number in the range 0@dots{}10.
22976 print $arg0 + $arg1
22979 print $arg0 + $arg1 + $arg2
22987 @item define @var{commandname}
22988 Define a command named @var{commandname}. If there is already a command
22989 by that name, you are asked to confirm that you want to redefine it.
22990 @var{commandname} may be a bare command name consisting of letters,
22991 numbers, dashes, and underscores. It may also start with any predefined
22992 prefix command. For example, @samp{define target my-target} creates
22993 a user-defined @samp{target my-target} command.
22995 The definition of the command is made up of other @value{GDBN} command lines,
22996 which are given following the @code{define} command. The end of these
22997 commands is marked by a line containing @code{end}.
23000 @kindex end@r{ (user-defined commands)}
23001 @item document @var{commandname}
23002 Document the user-defined command @var{commandname}, so that it can be
23003 accessed by @code{help}. The command @var{commandname} must already be
23004 defined. This command reads lines of documentation just as @code{define}
23005 reads the lines of the command definition, ending with @code{end}.
23006 After the @code{document} command is finished, @code{help} on command
23007 @var{commandname} displays the documentation you have written.
23009 You may use the @code{document} command again to change the
23010 documentation of a command. Redefining the command with @code{define}
23011 does not change the documentation.
23013 @kindex dont-repeat
23014 @cindex don't repeat command
23016 Used inside a user-defined command, this tells @value{GDBN} that this
23017 command should not be repeated when the user hits @key{RET}
23018 (@pxref{Command Syntax, repeat last command}).
23020 @kindex help user-defined
23021 @item help user-defined
23022 List all user-defined commands and all python commands defined in class
23023 COMAND_USER. The first line of the documentation or docstring is
23028 @itemx show user @var{commandname}
23029 Display the @value{GDBN} commands used to define @var{commandname} (but
23030 not its documentation). If no @var{commandname} is given, display the
23031 definitions for all user-defined commands.
23032 This does not work for user-defined python commands.
23034 @cindex infinite recursion in user-defined commands
23035 @kindex show max-user-call-depth
23036 @kindex set max-user-call-depth
23037 @item show max-user-call-depth
23038 @itemx set max-user-call-depth
23039 The value of @code{max-user-call-depth} controls how many recursion
23040 levels are allowed in user-defined commands before @value{GDBN} suspects an
23041 infinite recursion and aborts the command.
23042 This does not apply to user-defined python commands.
23045 In addition to the above commands, user-defined commands frequently
23046 use control flow commands, described in @ref{Command Files}.
23048 When user-defined commands are executed, the
23049 commands of the definition are not printed. An error in any command
23050 stops execution of the user-defined command.
23052 If used interactively, commands that would ask for confirmation proceed
23053 without asking when used inside a user-defined command. Many @value{GDBN}
23054 commands that normally print messages to say what they are doing omit the
23055 messages when used in a user-defined command.
23058 @subsection User-defined Command Hooks
23059 @cindex command hooks
23060 @cindex hooks, for commands
23061 @cindex hooks, pre-command
23064 You may define @dfn{hooks}, which are a special kind of user-defined
23065 command. Whenever you run the command @samp{foo}, if the user-defined
23066 command @samp{hook-foo} exists, it is executed (with no arguments)
23067 before that command.
23069 @cindex hooks, post-command
23071 A hook may also be defined which is run after the command you executed.
23072 Whenever you run the command @samp{foo}, if the user-defined command
23073 @samp{hookpost-foo} exists, it is executed (with no arguments) after
23074 that command. Post-execution hooks may exist simultaneously with
23075 pre-execution hooks, for the same command.
23077 It is valid for a hook to call the command which it hooks. If this
23078 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
23080 @c It would be nice if hookpost could be passed a parameter indicating
23081 @c if the command it hooks executed properly or not. FIXME!
23083 @kindex stop@r{, a pseudo-command}
23084 In addition, a pseudo-command, @samp{stop} exists. Defining
23085 (@samp{hook-stop}) makes the associated commands execute every time
23086 execution stops in your program: before breakpoint commands are run,
23087 displays are printed, or the stack frame is printed.
23089 For example, to ignore @code{SIGALRM} signals while
23090 single-stepping, but treat them normally during normal execution,
23095 handle SIGALRM nopass
23099 handle SIGALRM pass
23102 define hook-continue
23103 handle SIGALRM pass
23107 As a further example, to hook at the beginning and end of the @code{echo}
23108 command, and to add extra text to the beginning and end of the message,
23116 define hookpost-echo
23120 (@value{GDBP}) echo Hello World
23121 <<<---Hello World--->>>
23126 You can define a hook for any single-word command in @value{GDBN}, but
23127 not for command aliases; you should define a hook for the basic command
23128 name, e.g.@: @code{backtrace} rather than @code{bt}.
23129 @c FIXME! So how does Joe User discover whether a command is an alias
23131 You can hook a multi-word command by adding @code{hook-} or
23132 @code{hookpost-} to the last word of the command, e.g.@:
23133 @samp{define target hook-remote} to add a hook to @samp{target remote}.
23135 If an error occurs during the execution of your hook, execution of
23136 @value{GDBN} commands stops and @value{GDBN} issues a prompt
23137 (before the command that you actually typed had a chance to run).
23139 If you try to define a hook which does not match any known command, you
23140 get a warning from the @code{define} command.
23142 @node Command Files
23143 @subsection Command Files
23145 @cindex command files
23146 @cindex scripting commands
23147 A command file for @value{GDBN} is a text file made of lines that are
23148 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
23149 also be included. An empty line in a command file does nothing; it
23150 does not mean to repeat the last command, as it would from the
23153 You can request the execution of a command file with the @code{source}
23154 command. Note that the @code{source} command is also used to evaluate
23155 scripts that are not Command Files. The exact behavior can be configured
23156 using the @code{script-extension} setting.
23157 @xref{Extending GDB,, Extending GDB}.
23161 @cindex execute commands from a file
23162 @item source [-s] [-v] @var{filename}
23163 Execute the command file @var{filename}.
23166 The lines in a command file are generally executed sequentially,
23167 unless the order of execution is changed by one of the
23168 @emph{flow-control commands} described below. The commands are not
23169 printed as they are executed. An error in any command terminates
23170 execution of the command file and control is returned to the console.
23172 @value{GDBN} first searches for @var{filename} in the current directory.
23173 If the file is not found there, and @var{filename} does not specify a
23174 directory, then @value{GDBN} also looks for the file on the source search path
23175 (specified with the @samp{directory} command);
23176 except that @file{$cdir} is not searched because the compilation directory
23177 is not relevant to scripts.
23179 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
23180 on the search path even if @var{filename} specifies a directory.
23181 The search is done by appending @var{filename} to each element of the
23182 search path. So, for example, if @var{filename} is @file{mylib/myscript}
23183 and the search path contains @file{/home/user} then @value{GDBN} will
23184 look for the script @file{/home/user/mylib/myscript}.
23185 The search is also done if @var{filename} is an absolute path.
23186 For example, if @var{filename} is @file{/tmp/myscript} and
23187 the search path contains @file{/home/user} then @value{GDBN} will
23188 look for the script @file{/home/user/tmp/myscript}.
23189 For DOS-like systems, if @var{filename} contains a drive specification,
23190 it is stripped before concatenation. For example, if @var{filename} is
23191 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
23192 will look for the script @file{c:/tmp/myscript}.
23194 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
23195 each command as it is executed. The option must be given before
23196 @var{filename}, and is interpreted as part of the filename anywhere else.
23198 Commands that would ask for confirmation if used interactively proceed
23199 without asking when used in a command file. Many @value{GDBN} commands that
23200 normally print messages to say what they are doing omit the messages
23201 when called from command files.
23203 @value{GDBN} also accepts command input from standard input. In this
23204 mode, normal output goes to standard output and error output goes to
23205 standard error. Errors in a command file supplied on standard input do
23206 not terminate execution of the command file---execution continues with
23210 gdb < cmds > log 2>&1
23213 (The syntax above will vary depending on the shell used.) This example
23214 will execute commands from the file @file{cmds}. All output and errors
23215 would be directed to @file{log}.
23217 Since commands stored on command files tend to be more general than
23218 commands typed interactively, they frequently need to deal with
23219 complicated situations, such as different or unexpected values of
23220 variables and symbols, changes in how the program being debugged is
23221 built, etc. @value{GDBN} provides a set of flow-control commands to
23222 deal with these complexities. Using these commands, you can write
23223 complex scripts that loop over data structures, execute commands
23224 conditionally, etc.
23231 This command allows to include in your script conditionally executed
23232 commands. The @code{if} command takes a single argument, which is an
23233 expression to evaluate. It is followed by a series of commands that
23234 are executed only if the expression is true (its value is nonzero).
23235 There can then optionally be an @code{else} line, followed by a series
23236 of commands that are only executed if the expression was false. The
23237 end of the list is marked by a line containing @code{end}.
23241 This command allows to write loops. Its syntax is similar to
23242 @code{if}: the command takes a single argument, which is an expression
23243 to evaluate, and must be followed by the commands to execute, one per
23244 line, terminated by an @code{end}. These commands are called the
23245 @dfn{body} of the loop. The commands in the body of @code{while} are
23246 executed repeatedly as long as the expression evaluates to true.
23250 This command exits the @code{while} loop in whose body it is included.
23251 Execution of the script continues after that @code{while}s @code{end}
23254 @kindex loop_continue
23255 @item loop_continue
23256 This command skips the execution of the rest of the body of commands
23257 in the @code{while} loop in whose body it is included. Execution
23258 branches to the beginning of the @code{while} loop, where it evaluates
23259 the controlling expression.
23261 @kindex end@r{ (if/else/while commands)}
23263 Terminate the block of commands that are the body of @code{if},
23264 @code{else}, or @code{while} flow-control commands.
23269 @subsection Commands for Controlled Output
23271 During the execution of a command file or a user-defined command, normal
23272 @value{GDBN} output is suppressed; the only output that appears is what is
23273 explicitly printed by the commands in the definition. This section
23274 describes three commands useful for generating exactly the output you
23279 @item echo @var{text}
23280 @c I do not consider backslash-space a standard C escape sequence
23281 @c because it is not in ANSI.
23282 Print @var{text}. Nonprinting characters can be included in
23283 @var{text} using C escape sequences, such as @samp{\n} to print a
23284 newline. @strong{No newline is printed unless you specify one.}
23285 In addition to the standard C escape sequences, a backslash followed
23286 by a space stands for a space. This is useful for displaying a
23287 string with spaces at the beginning or the end, since leading and
23288 trailing spaces are otherwise trimmed from all arguments.
23289 To print @samp{@w{ }and foo =@w{ }}, use the command
23290 @samp{echo \@w{ }and foo = \@w{ }}.
23292 A backslash at the end of @var{text} can be used, as in C, to continue
23293 the command onto subsequent lines. For example,
23296 echo This is some text\n\
23297 which is continued\n\
23298 onto several lines.\n
23301 produces the same output as
23304 echo This is some text\n
23305 echo which is continued\n
23306 echo onto several lines.\n
23310 @item output @var{expression}
23311 Print the value of @var{expression} and nothing but that value: no
23312 newlines, no @samp{$@var{nn} = }. The value is not entered in the
23313 value history either. @xref{Expressions, ,Expressions}, for more information
23316 @item output/@var{fmt} @var{expression}
23317 Print the value of @var{expression} in format @var{fmt}. You can use
23318 the same formats as for @code{print}. @xref{Output Formats,,Output
23319 Formats}, for more information.
23322 @item printf @var{template}, @var{expressions}@dots{}
23323 Print the values of one or more @var{expressions} under the control of
23324 the string @var{template}. To print several values, make
23325 @var{expressions} be a comma-separated list of individual expressions,
23326 which may be either numbers or pointers. Their values are printed as
23327 specified by @var{template}, exactly as a C program would do by
23328 executing the code below:
23331 printf (@var{template}, @var{expressions}@dots{});
23334 As in @code{C} @code{printf}, ordinary characters in @var{template}
23335 are printed verbatim, while @dfn{conversion specification} introduced
23336 by the @samp{%} character cause subsequent @var{expressions} to be
23337 evaluated, their values converted and formatted according to type and
23338 style information encoded in the conversion specifications, and then
23341 For example, you can print two values in hex like this:
23344 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
23347 @code{printf} supports all the standard @code{C} conversion
23348 specifications, including the flags and modifiers between the @samp{%}
23349 character and the conversion letter, with the following exceptions:
23353 The argument-ordering modifiers, such as @samp{2$}, are not supported.
23356 The modifier @samp{*} is not supported for specifying precision or
23360 The @samp{'} flag (for separation of digits into groups according to
23361 @code{LC_NUMERIC'}) is not supported.
23364 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
23368 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
23371 The conversion letters @samp{a} and @samp{A} are not supported.
23375 Note that the @samp{ll} type modifier is supported only if the
23376 underlying @code{C} implementation used to build @value{GDBN} supports
23377 the @code{long long int} type, and the @samp{L} type modifier is
23378 supported only if @code{long double} type is available.
23380 As in @code{C}, @code{printf} supports simple backslash-escape
23381 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
23382 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
23383 single character. Octal and hexadecimal escape sequences are not
23386 Additionally, @code{printf} supports conversion specifications for DFP
23387 (@dfn{Decimal Floating Point}) types using the following length modifiers
23388 together with a floating point specifier.
23393 @samp{H} for printing @code{Decimal32} types.
23396 @samp{D} for printing @code{Decimal64} types.
23399 @samp{DD} for printing @code{Decimal128} types.
23402 If the underlying @code{C} implementation used to build @value{GDBN} has
23403 support for the three length modifiers for DFP types, other modifiers
23404 such as width and precision will also be available for @value{GDBN} to use.
23406 In case there is no such @code{C} support, no additional modifiers will be
23407 available and the value will be printed in the standard way.
23409 Here's an example of printing DFP types using the above conversion letters:
23411 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
23415 @item eval @var{template}, @var{expressions}@dots{}
23416 Convert the values of one or more @var{expressions} under the control of
23417 the string @var{template} to a command line, and call it.
23421 @node Auto-loading sequences
23422 @subsection Controlling auto-loading native @value{GDBN} scripts
23423 @cindex native script auto-loading
23425 When a new object file is read (for example, due to the @code{file}
23426 command, or because the inferior has loaded a shared library),
23427 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
23428 @xref{Auto-loading extensions}.
23430 Auto-loading can be enabled or disabled,
23431 and the list of auto-loaded scripts can be printed.
23434 @anchor{set auto-load gdb-scripts}
23435 @kindex set auto-load gdb-scripts
23436 @item set auto-load gdb-scripts [on|off]
23437 Enable or disable the auto-loading of canned sequences of commands scripts.
23439 @anchor{show auto-load gdb-scripts}
23440 @kindex show auto-load gdb-scripts
23441 @item show auto-load gdb-scripts
23442 Show whether auto-loading of canned sequences of commands scripts is enabled or
23445 @anchor{info auto-load gdb-scripts}
23446 @kindex info auto-load gdb-scripts
23447 @cindex print list of auto-loaded canned sequences of commands scripts
23448 @item info auto-load gdb-scripts [@var{regexp}]
23449 Print the list of all canned sequences of commands scripts that @value{GDBN}
23453 If @var{regexp} is supplied only canned sequences of commands scripts with
23454 matching names are printed.
23457 @section Extending @value{GDBN} using Python
23458 @cindex python scripting
23459 @cindex scripting with python
23461 You can extend @value{GDBN} using the @uref{http://www.python.org/,
23462 Python programming language}. This feature is available only if
23463 @value{GDBN} was configured using @option{--with-python}.
23465 @cindex python directory
23466 Python scripts used by @value{GDBN} should be installed in
23467 @file{@var{data-directory}/python}, where @var{data-directory} is
23468 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
23469 This directory, known as the @dfn{python directory},
23470 is automatically added to the Python Search Path in order to allow
23471 the Python interpreter to locate all scripts installed at this location.
23473 Additionally, @value{GDBN} commands and convenience functions which
23474 are written in Python and are located in the
23475 @file{@var{data-directory}/python/gdb/command} or
23476 @file{@var{data-directory}/python/gdb/function} directories are
23477 automatically imported when @value{GDBN} starts.
23480 * Python Commands:: Accessing Python from @value{GDBN}.
23481 * Python API:: Accessing @value{GDBN} from Python.
23482 * Python Auto-loading:: Automatically loading Python code.
23483 * Python modules:: Python modules provided by @value{GDBN}.
23486 @node Python Commands
23487 @subsection Python Commands
23488 @cindex python commands
23489 @cindex commands to access python
23491 @value{GDBN} provides two commands for accessing the Python interpreter,
23492 and one related setting:
23495 @kindex python-interactive
23497 @item python-interactive @r{[}@var{command}@r{]}
23498 @itemx pi @r{[}@var{command}@r{]}
23499 Without an argument, the @code{python-interactive} command can be used
23500 to start an interactive Python prompt. To return to @value{GDBN},
23501 type the @code{EOF} character (e.g., @kbd{Ctrl-D} on an empty prompt).
23503 Alternatively, a single-line Python command can be given as an
23504 argument and evaluated. If the command is an expression, the result
23505 will be printed; otherwise, nothing will be printed. For example:
23508 (@value{GDBP}) python-interactive 2 + 3
23514 @item python @r{[}@var{command}@r{]}
23515 @itemx py @r{[}@var{command}@r{]}
23516 The @code{python} command can be used to evaluate Python code.
23518 If given an argument, the @code{python} command will evaluate the
23519 argument as a Python command. For example:
23522 (@value{GDBP}) python print 23
23526 If you do not provide an argument to @code{python}, it will act as a
23527 multi-line command, like @code{define}. In this case, the Python
23528 script is made up of subsequent command lines, given after the
23529 @code{python} command. This command list is terminated using a line
23530 containing @code{end}. For example:
23533 (@value{GDBP}) python
23535 End with a line saying just "end".
23541 @kindex set python print-stack
23542 @item set python print-stack
23543 By default, @value{GDBN} will print only the message component of a
23544 Python exception when an error occurs in a Python script. This can be
23545 controlled using @code{set python print-stack}: if @code{full}, then
23546 full Python stack printing is enabled; if @code{none}, then Python stack
23547 and message printing is disabled; if @code{message}, the default, only
23548 the message component of the error is printed.
23551 It is also possible to execute a Python script from the @value{GDBN}
23555 @item source @file{script-name}
23556 The script name must end with @samp{.py} and @value{GDBN} must be configured
23557 to recognize the script language based on filename extension using
23558 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
23560 @item python execfile ("script-name")
23561 This method is based on the @code{execfile} Python built-in function,
23562 and thus is always available.
23566 @subsection Python API
23568 @cindex programming in python
23570 You can get quick online help for @value{GDBN}'s Python API by issuing
23571 the command @w{@kbd{python help (gdb)}}.
23573 Functions and methods which have two or more optional arguments allow
23574 them to be specified using keyword syntax. This allows passing some
23575 optional arguments while skipping others. Example:
23576 @w{@code{gdb.some_function ('foo', bar = 1, baz = 2)}}.
23579 * Basic Python:: Basic Python Functions.
23580 * Exception Handling:: How Python exceptions are translated.
23581 * Values From Inferior:: Python representation of values.
23582 * Types In Python:: Python representation of types.
23583 * Pretty Printing API:: Pretty-printing values.
23584 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
23585 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
23586 * Type Printing API:: Pretty-printing types.
23587 * Frame Filter API:: Filtering Frames.
23588 * Frame Decorator API:: Decorating Frames.
23589 * Writing a Frame Filter:: Writing a Frame Filter.
23590 * Inferiors In Python:: Python representation of inferiors (processes)
23591 * Events In Python:: Listening for events from @value{GDBN}.
23592 * Threads In Python:: Accessing inferior threads from Python.
23593 * Commands In Python:: Implementing new commands in Python.
23594 * Parameters In Python:: Adding new @value{GDBN} parameters.
23595 * Functions In Python:: Writing new convenience functions.
23596 * Progspaces In Python:: Program spaces.
23597 * Objfiles In Python:: Object files.
23598 * Frames In Python:: Accessing inferior stack frames from Python.
23599 * Blocks In Python:: Accessing blocks from Python.
23600 * Symbols In Python:: Python representation of symbols.
23601 * Symbol Tables In Python:: Python representation of symbol tables.
23602 * Line Tables In Python:: Python representation of line tables.
23603 * Breakpoints In Python:: Manipulating breakpoints using Python.
23604 * Finish Breakpoints in Python:: Setting Breakpoints on function return
23606 * Lazy Strings In Python:: Python representation of lazy strings.
23607 * Architectures In Python:: Python representation of architectures.
23611 @subsubsection Basic Python
23613 @cindex python stdout
23614 @cindex python pagination
23615 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
23616 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
23617 A Python program which outputs to one of these streams may have its
23618 output interrupted by the user (@pxref{Screen Size}). In this
23619 situation, a Python @code{KeyboardInterrupt} exception is thrown.
23621 Some care must be taken when writing Python code to run in
23622 @value{GDBN}. Two things worth noting in particular:
23626 @value{GDBN} install handlers for @code{SIGCHLD} and @code{SIGINT}.
23627 Python code must not override these, or even change the options using
23628 @code{sigaction}. If your program changes the handling of these
23629 signals, @value{GDBN} will most likely stop working correctly. Note
23630 that it is unfortunately common for GUI toolkits to install a
23631 @code{SIGCHLD} handler.
23634 @value{GDBN} takes care to mark its internal file descriptors as
23635 close-on-exec. However, this cannot be done in a thread-safe way on
23636 all platforms. Your Python programs should be aware of this and
23637 should both create new file descriptors with the close-on-exec flag
23638 set and arrange to close unneeded file descriptors before starting a
23642 @cindex python functions
23643 @cindex python module
23645 @value{GDBN} introduces a new Python module, named @code{gdb}. All
23646 methods and classes added by @value{GDBN} are placed in this module.
23647 @value{GDBN} automatically @code{import}s the @code{gdb} module for
23648 use in all scripts evaluated by the @code{python} command.
23650 @findex gdb.PYTHONDIR
23651 @defvar gdb.PYTHONDIR
23652 A string containing the python directory (@pxref{Python}).
23655 @findex gdb.execute
23656 @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]})
23657 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
23658 If a GDB exception happens while @var{command} runs, it is
23659 translated as described in @ref{Exception Handling,,Exception Handling}.
23661 @var{from_tty} specifies whether @value{GDBN} ought to consider this
23662 command as having originated from the user invoking it interactively.
23663 It must be a boolean value. If omitted, it defaults to @code{False}.
23665 By default, any output produced by @var{command} is sent to
23666 @value{GDBN}'s standard output. If the @var{to_string} parameter is
23667 @code{True}, then output will be collected by @code{gdb.execute} and
23668 returned as a string. The default is @code{False}, in which case the
23669 return value is @code{None}. If @var{to_string} is @code{True}, the
23670 @value{GDBN} virtual terminal will be temporarily set to unlimited width
23671 and height, and its pagination will be disabled; @pxref{Screen Size}.
23674 @findex gdb.breakpoints
23675 @defun gdb.breakpoints ()
23676 Return a sequence holding all of @value{GDBN}'s breakpoints.
23677 @xref{Breakpoints In Python}, for more information.
23680 @findex gdb.parameter
23681 @defun gdb.parameter (parameter)
23682 Return the value of a @value{GDBN} parameter. @var{parameter} is a
23683 string naming the parameter to look up; @var{parameter} may contain
23684 spaces if the parameter has a multi-part name. For example,
23685 @samp{print object} is a valid parameter name.
23687 If the named parameter does not exist, this function throws a
23688 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
23689 parameter's value is converted to a Python value of the appropriate
23690 type, and returned.
23693 @findex gdb.history
23694 @defun gdb.history (number)
23695 Return a value from @value{GDBN}'s value history (@pxref{Value
23696 History}). @var{number} indicates which history element to return.
23697 If @var{number} is negative, then @value{GDBN} will take its absolute value
23698 and count backward from the last element (i.e., the most recent element) to
23699 find the value to return. If @var{number} is zero, then @value{GDBN} will
23700 return the most recent element. If the element specified by @var{number}
23701 doesn't exist in the value history, a @code{gdb.error} exception will be
23704 If no exception is raised, the return value is always an instance of
23705 @code{gdb.Value} (@pxref{Values From Inferior}).
23708 @findex gdb.parse_and_eval
23709 @defun gdb.parse_and_eval (expression)
23710 Parse @var{expression} as an expression in the current language,
23711 evaluate it, and return the result as a @code{gdb.Value}.
23712 @var{expression} must be a string.
23714 This function can be useful when implementing a new command
23715 (@pxref{Commands In Python}), as it provides a way to parse the
23716 command's argument as an expression. It is also useful simply to
23717 compute values, for example, it is the only way to get the value of a
23718 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
23721 @findex gdb.find_pc_line
23722 @defun gdb.find_pc_line (pc)
23723 Return the @code{gdb.Symtab_and_line} object corresponding to the
23724 @var{pc} value. @xref{Symbol Tables In Python}. If an invalid
23725 value of @var{pc} is passed as an argument, then the @code{symtab} and
23726 @code{line} attributes of the returned @code{gdb.Symtab_and_line} object
23727 will be @code{None} and 0 respectively.
23730 @findex gdb.post_event
23731 @defun gdb.post_event (event)
23732 Put @var{event}, a callable object taking no arguments, into
23733 @value{GDBN}'s internal event queue. This callable will be invoked at
23734 some later point, during @value{GDBN}'s event processing. Events
23735 posted using @code{post_event} will be run in the order in which they
23736 were posted; however, there is no way to know when they will be
23737 processed relative to other events inside @value{GDBN}.
23739 @value{GDBN} is not thread-safe. If your Python program uses multiple
23740 threads, you must be careful to only call @value{GDBN}-specific
23741 functions in the main @value{GDBN} thread. @code{post_event} ensures
23745 (@value{GDBP}) python
23749 > def __init__(self, message):
23750 > self.message = message;
23751 > def __call__(self):
23752 > gdb.write(self.message)
23754 >class MyThread1 (threading.Thread):
23756 > gdb.post_event(Writer("Hello "))
23758 >class MyThread2 (threading.Thread):
23760 > gdb.post_event(Writer("World\n"))
23762 >MyThread1().start()
23763 >MyThread2().start()
23765 (@value{GDBP}) Hello World
23770 @defun gdb.write (string @r{[}, stream{]})
23771 Print a string to @value{GDBN}'s paginated output stream. The
23772 optional @var{stream} determines the stream to print to. The default
23773 stream is @value{GDBN}'s standard output stream. Possible stream
23780 @value{GDBN}'s standard output stream.
23785 @value{GDBN}'s standard error stream.
23790 @value{GDBN}'s log stream (@pxref{Logging Output}).
23793 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
23794 call this function and will automatically direct the output to the
23799 @defun gdb.flush ()
23800 Flush the buffer of a @value{GDBN} paginated stream so that the
23801 contents are displayed immediately. @value{GDBN} will flush the
23802 contents of a stream automatically when it encounters a newline in the
23803 buffer. The optional @var{stream} determines the stream to flush. The
23804 default stream is @value{GDBN}'s standard output stream. Possible
23811 @value{GDBN}'s standard output stream.
23816 @value{GDBN}'s standard error stream.
23821 @value{GDBN}'s log stream (@pxref{Logging Output}).
23825 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
23826 call this function for the relevant stream.
23829 @findex gdb.target_charset
23830 @defun gdb.target_charset ()
23831 Return the name of the current target character set (@pxref{Character
23832 Sets}). This differs from @code{gdb.parameter('target-charset')} in
23833 that @samp{auto} is never returned.
23836 @findex gdb.target_wide_charset
23837 @defun gdb.target_wide_charset ()
23838 Return the name of the current target wide character set
23839 (@pxref{Character Sets}). This differs from
23840 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
23844 @findex gdb.solib_name
23845 @defun gdb.solib_name (address)
23846 Return the name of the shared library holding the given @var{address}
23847 as a string, or @code{None}.
23850 @findex gdb.decode_line
23851 @defun gdb.decode_line @r{[}expression@r{]}
23852 Return locations of the line specified by @var{expression}, or of the
23853 current line if no argument was given. This function returns a Python
23854 tuple containing two elements. The first element contains a string
23855 holding any unparsed section of @var{expression} (or @code{None} if
23856 the expression has been fully parsed). The second element contains
23857 either @code{None} or another tuple that contains all the locations
23858 that match the expression represented as @code{gdb.Symtab_and_line}
23859 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
23860 provided, it is decoded the way that @value{GDBN}'s inbuilt
23861 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
23864 @defun gdb.prompt_hook (current_prompt)
23865 @anchor{prompt_hook}
23867 If @var{prompt_hook} is callable, @value{GDBN} will call the method
23868 assigned to this operation before a prompt is displayed by
23871 The parameter @code{current_prompt} contains the current @value{GDBN}
23872 prompt. This method must return a Python string, or @code{None}. If
23873 a string is returned, the @value{GDBN} prompt will be set to that
23874 string. If @code{None} is returned, @value{GDBN} will continue to use
23875 the current prompt.
23877 Some prompts cannot be substituted in @value{GDBN}. Secondary prompts
23878 such as those used by readline for command input, and annotation
23879 related prompts are prohibited from being changed.
23882 @node Exception Handling
23883 @subsubsection Exception Handling
23884 @cindex python exceptions
23885 @cindex exceptions, python
23887 When executing the @code{python} command, Python exceptions
23888 uncaught within the Python code are translated to calls to
23889 @value{GDBN} error-reporting mechanism. If the command that called
23890 @code{python} does not handle the error, @value{GDBN} will
23891 terminate it and print an error message containing the Python
23892 exception name, the associated value, and the Python call stack
23893 backtrace at the point where the exception was raised. Example:
23896 (@value{GDBP}) python print foo
23897 Traceback (most recent call last):
23898 File "<string>", line 1, in <module>
23899 NameError: name 'foo' is not defined
23902 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
23903 Python code are converted to Python exceptions. The type of the
23904 Python exception depends on the error.
23908 This is the base class for most exceptions generated by @value{GDBN}.
23909 It is derived from @code{RuntimeError}, for compatibility with earlier
23910 versions of @value{GDBN}.
23912 If an error occurring in @value{GDBN} does not fit into some more
23913 specific category, then the generated exception will have this type.
23915 @item gdb.MemoryError
23916 This is a subclass of @code{gdb.error} which is thrown when an
23917 operation tried to access invalid memory in the inferior.
23919 @item KeyboardInterrupt
23920 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
23921 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
23924 In all cases, your exception handler will see the @value{GDBN} error
23925 message as its value and the Python call stack backtrace at the Python
23926 statement closest to where the @value{GDBN} error occured as the
23929 @findex gdb.GdbError
23930 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
23931 it is useful to be able to throw an exception that doesn't cause a
23932 traceback to be printed. For example, the user may have invoked the
23933 command incorrectly. Use the @code{gdb.GdbError} exception
23934 to handle this case. Example:
23938 >class HelloWorld (gdb.Command):
23939 > """Greet the whole world."""
23940 > def __init__ (self):
23941 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
23942 > def invoke (self, args, from_tty):
23943 > argv = gdb.string_to_argv (args)
23944 > if len (argv) != 0:
23945 > raise gdb.GdbError ("hello-world takes no arguments")
23946 > print "Hello, World!"
23949 (gdb) hello-world 42
23950 hello-world takes no arguments
23953 @node Values From Inferior
23954 @subsubsection Values From Inferior
23955 @cindex values from inferior, with Python
23956 @cindex python, working with values from inferior
23958 @cindex @code{gdb.Value}
23959 @value{GDBN} provides values it obtains from the inferior program in
23960 an object of type @code{gdb.Value}. @value{GDBN} uses this object
23961 for its internal bookkeeping of the inferior's values, and for
23962 fetching values when necessary.
23964 Inferior values that are simple scalars can be used directly in
23965 Python expressions that are valid for the value's data type. Here's
23966 an example for an integer or floating-point value @code{some_val}:
23973 As result of this, @code{bar} will also be a @code{gdb.Value} object
23974 whose values are of the same type as those of @code{some_val}.
23976 Inferior values that are structures or instances of some class can
23977 be accessed using the Python @dfn{dictionary syntax}. For example, if
23978 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
23979 can access its @code{foo} element with:
23982 bar = some_val['foo']
23985 @cindex getting structure elements using gdb.Field objects as subscripts
23986 Again, @code{bar} will also be a @code{gdb.Value} object. Structure
23987 elements can also be accessed by using @code{gdb.Field} objects as
23988 subscripts (@pxref{Types In Python}, for more information on
23989 @code{gdb.Field} objects). For example, if @code{foo_field} is a
23990 @code{gdb.Field} object corresponding to element @code{foo} of the above
23991 structure, then @code{bar} can also be accessed as follows:
23994 bar = some_val[foo_field]
23997 A @code{gdb.Value} that represents a function can be executed via
23998 inferior function call. Any arguments provided to the call must match
23999 the function's prototype, and must be provided in the order specified
24002 For example, @code{some_val} is a @code{gdb.Value} instance
24003 representing a function that takes two integers as arguments. To
24004 execute this function, call it like so:
24007 result = some_val (10,20)
24010 Any values returned from a function call will be stored as a
24013 The following attributes are provided:
24015 @defvar Value.address
24016 If this object is addressable, this read-only attribute holds a
24017 @code{gdb.Value} object representing the address. Otherwise,
24018 this attribute holds @code{None}.
24021 @cindex optimized out value in Python
24022 @defvar Value.is_optimized_out
24023 This read-only boolean attribute is true if the compiler optimized out
24024 this value, thus it is not available for fetching from the inferior.
24028 The type of this @code{gdb.Value}. The value of this attribute is a
24029 @code{gdb.Type} object (@pxref{Types In Python}).
24032 @defvar Value.dynamic_type
24033 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
24034 type information (@acronym{RTTI}) to determine the dynamic type of the
24035 value. If this value is of class type, it will return the class in
24036 which the value is embedded, if any. If this value is of pointer or
24037 reference to a class type, it will compute the dynamic type of the
24038 referenced object, and return a pointer or reference to that type,
24039 respectively. In all other cases, it will return the value's static
24042 Note that this feature will only work when debugging a C@t{++} program
24043 that includes @acronym{RTTI} for the object in question. Otherwise,
24044 it will just return the static type of the value as in @kbd{ptype foo}
24045 (@pxref{Symbols, ptype}).
24048 @defvar Value.is_lazy
24049 The value of this read-only boolean attribute is @code{True} if this
24050 @code{gdb.Value} has not yet been fetched from the inferior.
24051 @value{GDBN} does not fetch values until necessary, for efficiency.
24055 myval = gdb.parse_and_eval ('somevar')
24058 The value of @code{somevar} is not fetched at this time. It will be
24059 fetched when the value is needed, or when the @code{fetch_lazy}
24063 The following methods are provided:
24065 @defun Value.__init__ (@var{val})
24066 Many Python values can be converted directly to a @code{gdb.Value} via
24067 this object initializer. Specifically:
24070 @item Python boolean
24071 A Python boolean is converted to the boolean type from the current
24074 @item Python integer
24075 A Python integer is converted to the C @code{long} type for the
24076 current architecture.
24079 A Python long is converted to the C @code{long long} type for the
24080 current architecture.
24083 A Python float is converted to the C @code{double} type for the
24084 current architecture.
24086 @item Python string
24087 A Python string is converted to a target string, using the current
24090 @item @code{gdb.Value}
24091 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
24093 @item @code{gdb.LazyString}
24094 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
24095 Python}), then the lazy string's @code{value} method is called, and
24096 its result is used.
24100 @defun Value.cast (type)
24101 Return a new instance of @code{gdb.Value} that is the result of
24102 casting this instance to the type described by @var{type}, which must
24103 be a @code{gdb.Type} object. If the cast cannot be performed for some
24104 reason, this method throws an exception.
24107 @defun Value.dereference ()
24108 For pointer data types, this method returns a new @code{gdb.Value} object
24109 whose contents is the object pointed to by the pointer. For example, if
24110 @code{foo} is a C pointer to an @code{int}, declared in your C program as
24117 then you can use the corresponding @code{gdb.Value} to access what
24118 @code{foo} points to like this:
24121 bar = foo.dereference ()
24124 The result @code{bar} will be a @code{gdb.Value} object holding the
24125 value pointed to by @code{foo}.
24127 A similar function @code{Value.referenced_value} exists which also
24128 returns @code{gdb.Value} objects corresonding to the values pointed to
24129 by pointer values (and additionally, values referenced by reference
24130 values). However, the behavior of @code{Value.dereference}
24131 differs from @code{Value.referenced_value} by the fact that the
24132 behavior of @code{Value.dereference} is identical to applying the C
24133 unary operator @code{*} on a given value. For example, consider a
24134 reference to a pointer @code{ptrref}, declared in your C@t{++} program
24138 typedef int *intptr;
24142 intptr &ptrref = ptr;
24145 Though @code{ptrref} is a reference value, one can apply the method
24146 @code{Value.dereference} to the @code{gdb.Value} object corresponding
24147 to it and obtain a @code{gdb.Value} which is identical to that
24148 corresponding to @code{val}. However, if you apply the method
24149 @code{Value.referenced_value}, the result would be a @code{gdb.Value}
24150 object identical to that corresponding to @code{ptr}.
24153 py_ptrref = gdb.parse_and_eval ("ptrref")
24154 py_val = py_ptrref.dereference ()
24155 py_ptr = py_ptrref.referenced_value ()
24158 The @code{gdb.Value} object @code{py_val} is identical to that
24159 corresponding to @code{val}, and @code{py_ptr} is identical to that
24160 corresponding to @code{ptr}. In general, @code{Value.dereference} can
24161 be applied whenever the C unary operator @code{*} can be applied
24162 to the corresponding C value. For those cases where applying both
24163 @code{Value.dereference} and @code{Value.referenced_value} is allowed,
24164 the results obtained need not be identical (as we have seen in the above
24165 example). The results are however identical when applied on
24166 @code{gdb.Value} objects corresponding to pointers (@code{gdb.Value}
24167 objects with type code @code{TYPE_CODE_PTR}) in a C/C@t{++} program.
24170 @defun Value.referenced_value ()
24171 For pointer or reference data types, this method returns a new
24172 @code{gdb.Value} object corresponding to the value referenced by the
24173 pointer/reference value. For pointer data types,
24174 @code{Value.dereference} and @code{Value.referenced_value} produce
24175 identical results. The difference between these methods is that
24176 @code{Value.dereference} cannot get the values referenced by reference
24177 values. For example, consider a reference to an @code{int}, declared
24178 in your C@t{++} program as
24186 then applying @code{Value.dereference} to the @code{gdb.Value} object
24187 corresponding to @code{ref} will result in an error, while applying
24188 @code{Value.referenced_value} will result in a @code{gdb.Value} object
24189 identical to that corresponding to @code{val}.
24192 py_ref = gdb.parse_and_eval ("ref")
24193 er_ref = py_ref.dereference () # Results in error
24194 py_val = py_ref.referenced_value () # Returns the referenced value
24197 The @code{gdb.Value} object @code{py_val} is identical to that
24198 corresponding to @code{val}.
24201 @defun Value.dynamic_cast (type)
24202 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
24203 operator were used. Consult a C@t{++} reference for details.
24206 @defun Value.reinterpret_cast (type)
24207 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
24208 operator were used. Consult a C@t{++} reference for details.
24211 @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]})
24212 If this @code{gdb.Value} represents a string, then this method
24213 converts the contents to a Python string. Otherwise, this method will
24214 throw an exception.
24216 Strings are recognized in a language-specific way; whether a given
24217 @code{gdb.Value} represents a string is determined by the current
24220 For C-like languages, a value is a string if it is a pointer to or an
24221 array of characters or ints. The string is assumed to be terminated
24222 by a zero of the appropriate width. However if the optional length
24223 argument is given, the string will be converted to that given length,
24224 ignoring any embedded zeros that the string may contain.
24226 If the optional @var{encoding} argument is given, it must be a string
24227 naming the encoding of the string in the @code{gdb.Value}, such as
24228 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
24229 the same encodings as the corresponding argument to Python's
24230 @code{string.decode} method, and the Python codec machinery will be used
24231 to convert the string. If @var{encoding} is not given, or if
24232 @var{encoding} is the empty string, then either the @code{target-charset}
24233 (@pxref{Character Sets}) will be used, or a language-specific encoding
24234 will be used, if the current language is able to supply one.
24236 The optional @var{errors} argument is the same as the corresponding
24237 argument to Python's @code{string.decode} method.
24239 If the optional @var{length} argument is given, the string will be
24240 fetched and converted to the given length.
24243 @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]})
24244 If this @code{gdb.Value} represents a string, then this method
24245 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
24246 In Python}). Otherwise, this method will throw an exception.
24248 If the optional @var{encoding} argument is given, it must be a string
24249 naming the encoding of the @code{gdb.LazyString}. Some examples are:
24250 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
24251 @var{encoding} argument is an encoding that @value{GDBN} does
24252 recognize, @value{GDBN} will raise an error.
24254 When a lazy string is printed, the @value{GDBN} encoding machinery is
24255 used to convert the string during printing. If the optional
24256 @var{encoding} argument is not provided, or is an empty string,
24257 @value{GDBN} will automatically select the encoding most suitable for
24258 the string type. For further information on encoding in @value{GDBN}
24259 please see @ref{Character Sets}.
24261 If the optional @var{length} argument is given, the string will be
24262 fetched and encoded to the length of characters specified. If
24263 the @var{length} argument is not provided, the string will be fetched
24264 and encoded until a null of appropriate width is found.
24267 @defun Value.fetch_lazy ()
24268 If the @code{gdb.Value} object is currently a lazy value
24269 (@code{gdb.Value.is_lazy} is @code{True}), then the value is
24270 fetched from the inferior. Any errors that occur in the process
24271 will produce a Python exception.
24273 If the @code{gdb.Value} object is not a lazy value, this method
24276 This method does not return a value.
24280 @node Types In Python
24281 @subsubsection Types In Python
24282 @cindex types in Python
24283 @cindex Python, working with types
24286 @value{GDBN} represents types from the inferior using the class
24289 The following type-related functions are available in the @code{gdb}
24292 @findex gdb.lookup_type
24293 @defun gdb.lookup_type (name @r{[}, block@r{]})
24294 This function looks up a type by name. @var{name} is the name of the
24295 type to look up. It must be a string.
24297 If @var{block} is given, then @var{name} is looked up in that scope.
24298 Otherwise, it is searched for globally.
24300 Ordinarily, this function will return an instance of @code{gdb.Type}.
24301 If the named type cannot be found, it will throw an exception.
24304 If the type is a structure or class type, or an enum type, the fields
24305 of that type can be accessed using the Python @dfn{dictionary syntax}.
24306 For example, if @code{some_type} is a @code{gdb.Type} instance holding
24307 a structure type, you can access its @code{foo} field with:
24310 bar = some_type['foo']
24313 @code{bar} will be a @code{gdb.Field} object; see below under the
24314 description of the @code{Type.fields} method for a description of the
24315 @code{gdb.Field} class.
24317 An instance of @code{Type} has the following attributes:
24320 The type code for this type. The type code will be one of the
24321 @code{TYPE_CODE_} constants defined below.
24325 The name of this type. If this type has no name, then @code{None}
24329 @defvar Type.sizeof
24330 The size of this type, in target @code{char} units. Usually, a
24331 target's @code{char} type will be an 8-bit byte. However, on some
24332 unusual platforms, this type may have a different size.
24336 The tag name for this type. The tag name is the name after
24337 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
24338 languages have this concept. If this type has no tag name, then
24339 @code{None} is returned.
24342 The following methods are provided:
24344 @defun Type.fields ()
24345 For structure and union types, this method returns the fields. Range
24346 types have two fields, the minimum and maximum values. Enum types
24347 have one field per enum constant. Function and method types have one
24348 field per parameter. The base types of C@t{++} classes are also
24349 represented as fields. If the type has no fields, or does not fit
24350 into one of these categories, an empty sequence will be returned.
24352 Each field is a @code{gdb.Field} object, with some pre-defined attributes:
24355 This attribute is not available for @code{enum} or @code{static}
24356 (as in C@t{++} or Java) fields. The value is the position, counting
24357 in bits, from the start of the containing type.
24360 This attribute is only available for @code{enum} fields, and its value
24361 is the enumeration member's integer representation.
24364 The name of the field, or @code{None} for anonymous fields.
24367 This is @code{True} if the field is artificial, usually meaning that
24368 it was provided by the compiler and not the user. This attribute is
24369 always provided, and is @code{False} if the field is not artificial.
24371 @item is_base_class
24372 This is @code{True} if the field represents a base class of a C@t{++}
24373 structure. This attribute is always provided, and is @code{False}
24374 if the field is not a base class of the type that is the argument of
24375 @code{fields}, or if that type was not a C@t{++} class.
24378 If the field is packed, or is a bitfield, then this will have a
24379 non-zero value, which is the size of the field in bits. Otherwise,
24380 this will be zero; in this case the field's size is given by its type.
24383 The type of the field. This is usually an instance of @code{Type},
24384 but it can be @code{None} in some situations.
24387 The type which contains this field. This is an instance of
24392 @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]})
24393 Return a new @code{gdb.Type} object which represents an array of this
24394 type. If one argument is given, it is the inclusive upper bound of
24395 the array; in this case the lower bound is zero. If two arguments are
24396 given, the first argument is the lower bound of the array, and the
24397 second argument is the upper bound of the array. An array's length
24398 must not be negative, but the bounds can be.
24401 @defun Type.vector (@var{n1} @r{[}, @var{n2}@r{]})
24402 Return a new @code{gdb.Type} object which represents a vector of this
24403 type. If one argument is given, it is the inclusive upper bound of
24404 the vector; in this case the lower bound is zero. If two arguments are
24405 given, the first argument is the lower bound of the vector, and the
24406 second argument is the upper bound of the vector. A vector's length
24407 must not be negative, but the bounds can be.
24409 The difference between an @code{array} and a @code{vector} is that
24410 arrays behave like in C: when used in expressions they decay to a pointer
24411 to the first element whereas vectors are treated as first class values.
24414 @defun Type.const ()
24415 Return a new @code{gdb.Type} object which represents a
24416 @code{const}-qualified variant of this type.
24419 @defun Type.volatile ()
24420 Return a new @code{gdb.Type} object which represents a
24421 @code{volatile}-qualified variant of this type.
24424 @defun Type.unqualified ()
24425 Return a new @code{gdb.Type} object which represents an unqualified
24426 variant of this type. That is, the result is neither @code{const} nor
24430 @defun Type.range ()
24431 Return a Python @code{Tuple} object that contains two elements: the
24432 low bound of the argument type and the high bound of that type. If
24433 the type does not have a range, @value{GDBN} will raise a
24434 @code{gdb.error} exception (@pxref{Exception Handling}).
24437 @defun Type.reference ()
24438 Return a new @code{gdb.Type} object which represents a reference to this
24442 @defun Type.pointer ()
24443 Return a new @code{gdb.Type} object which represents a pointer to this
24447 @defun Type.strip_typedefs ()
24448 Return a new @code{gdb.Type} that represents the real type,
24449 after removing all layers of typedefs.
24452 @defun Type.target ()
24453 Return a new @code{gdb.Type} object which represents the target type
24456 For a pointer type, the target type is the type of the pointed-to
24457 object. For an array type (meaning C-like arrays), the target type is
24458 the type of the elements of the array. For a function or method type,
24459 the target type is the type of the return value. For a complex type,
24460 the target type is the type of the elements. For a typedef, the
24461 target type is the aliased type.
24463 If the type does not have a target, this method will throw an
24467 @defun Type.template_argument (n @r{[}, block@r{]})
24468 If this @code{gdb.Type} is an instantiation of a template, this will
24469 return a new @code{gdb.Type} which represents the type of the
24470 @var{n}th template argument.
24472 If this @code{gdb.Type} is not a template type, this will throw an
24473 exception. Ordinarily, only C@t{++} code will have template types.
24475 If @var{block} is given, then @var{name} is looked up in that scope.
24476 Otherwise, it is searched for globally.
24480 Each type has a code, which indicates what category this type falls
24481 into. The available type categories are represented by constants
24482 defined in the @code{gdb} module:
24485 @findex TYPE_CODE_PTR
24486 @findex gdb.TYPE_CODE_PTR
24487 @item gdb.TYPE_CODE_PTR
24488 The type is a pointer.
24490 @findex TYPE_CODE_ARRAY
24491 @findex gdb.TYPE_CODE_ARRAY
24492 @item gdb.TYPE_CODE_ARRAY
24493 The type is an array.
24495 @findex TYPE_CODE_STRUCT
24496 @findex gdb.TYPE_CODE_STRUCT
24497 @item gdb.TYPE_CODE_STRUCT
24498 The type is a structure.
24500 @findex TYPE_CODE_UNION
24501 @findex gdb.TYPE_CODE_UNION
24502 @item gdb.TYPE_CODE_UNION
24503 The type is a union.
24505 @findex TYPE_CODE_ENUM
24506 @findex gdb.TYPE_CODE_ENUM
24507 @item gdb.TYPE_CODE_ENUM
24508 The type is an enum.
24510 @findex TYPE_CODE_FLAGS
24511 @findex gdb.TYPE_CODE_FLAGS
24512 @item gdb.TYPE_CODE_FLAGS
24513 A bit flags type, used for things such as status registers.
24515 @findex TYPE_CODE_FUNC
24516 @findex gdb.TYPE_CODE_FUNC
24517 @item gdb.TYPE_CODE_FUNC
24518 The type is a function.
24520 @findex TYPE_CODE_INT
24521 @findex gdb.TYPE_CODE_INT
24522 @item gdb.TYPE_CODE_INT
24523 The type is an integer type.
24525 @findex TYPE_CODE_FLT
24526 @findex gdb.TYPE_CODE_FLT
24527 @item gdb.TYPE_CODE_FLT
24528 A floating point type.
24530 @findex TYPE_CODE_VOID
24531 @findex gdb.TYPE_CODE_VOID
24532 @item gdb.TYPE_CODE_VOID
24533 The special type @code{void}.
24535 @findex TYPE_CODE_SET
24536 @findex gdb.TYPE_CODE_SET
24537 @item gdb.TYPE_CODE_SET
24540 @findex TYPE_CODE_RANGE
24541 @findex gdb.TYPE_CODE_RANGE
24542 @item gdb.TYPE_CODE_RANGE
24543 A range type, that is, an integer type with bounds.
24545 @findex TYPE_CODE_STRING
24546 @findex gdb.TYPE_CODE_STRING
24547 @item gdb.TYPE_CODE_STRING
24548 A string type. Note that this is only used for certain languages with
24549 language-defined string types; C strings are not represented this way.
24551 @findex TYPE_CODE_BITSTRING
24552 @findex gdb.TYPE_CODE_BITSTRING
24553 @item gdb.TYPE_CODE_BITSTRING
24554 A string of bits. It is deprecated.
24556 @findex TYPE_CODE_ERROR
24557 @findex gdb.TYPE_CODE_ERROR
24558 @item gdb.TYPE_CODE_ERROR
24559 An unknown or erroneous type.
24561 @findex TYPE_CODE_METHOD
24562 @findex gdb.TYPE_CODE_METHOD
24563 @item gdb.TYPE_CODE_METHOD
24564 A method type, as found in C@t{++} or Java.
24566 @findex TYPE_CODE_METHODPTR
24567 @findex gdb.TYPE_CODE_METHODPTR
24568 @item gdb.TYPE_CODE_METHODPTR
24569 A pointer-to-member-function.
24571 @findex TYPE_CODE_MEMBERPTR
24572 @findex gdb.TYPE_CODE_MEMBERPTR
24573 @item gdb.TYPE_CODE_MEMBERPTR
24574 A pointer-to-member.
24576 @findex TYPE_CODE_REF
24577 @findex gdb.TYPE_CODE_REF
24578 @item gdb.TYPE_CODE_REF
24581 @findex TYPE_CODE_CHAR
24582 @findex gdb.TYPE_CODE_CHAR
24583 @item gdb.TYPE_CODE_CHAR
24586 @findex TYPE_CODE_BOOL
24587 @findex gdb.TYPE_CODE_BOOL
24588 @item gdb.TYPE_CODE_BOOL
24591 @findex TYPE_CODE_COMPLEX
24592 @findex gdb.TYPE_CODE_COMPLEX
24593 @item gdb.TYPE_CODE_COMPLEX
24594 A complex float type.
24596 @findex TYPE_CODE_TYPEDEF
24597 @findex gdb.TYPE_CODE_TYPEDEF
24598 @item gdb.TYPE_CODE_TYPEDEF
24599 A typedef to some other type.
24601 @findex TYPE_CODE_NAMESPACE
24602 @findex gdb.TYPE_CODE_NAMESPACE
24603 @item gdb.TYPE_CODE_NAMESPACE
24604 A C@t{++} namespace.
24606 @findex TYPE_CODE_DECFLOAT
24607 @findex gdb.TYPE_CODE_DECFLOAT
24608 @item gdb.TYPE_CODE_DECFLOAT
24609 A decimal floating point type.
24611 @findex TYPE_CODE_INTERNAL_FUNCTION
24612 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
24613 @item gdb.TYPE_CODE_INTERNAL_FUNCTION
24614 A function internal to @value{GDBN}. This is the type used to represent
24615 convenience functions.
24618 Further support for types is provided in the @code{gdb.types}
24619 Python module (@pxref{gdb.types}).
24621 @node Pretty Printing API
24622 @subsubsection Pretty Printing API
24624 An example output is provided (@pxref{Pretty Printing}).
24626 A pretty-printer is just an object that holds a value and implements a
24627 specific interface, defined here.
24629 @defun pretty_printer.children (self)
24630 @value{GDBN} will call this method on a pretty-printer to compute the
24631 children of the pretty-printer's value.
24633 This method must return an object conforming to the Python iterator
24634 protocol. Each item returned by the iterator must be a tuple holding
24635 two elements. The first element is the ``name'' of the child; the
24636 second element is the child's value. The value can be any Python
24637 object which is convertible to a @value{GDBN} value.
24639 This method is optional. If it does not exist, @value{GDBN} will act
24640 as though the value has no children.
24643 @defun pretty_printer.display_hint (self)
24644 The CLI may call this method and use its result to change the
24645 formatting of a value. The result will also be supplied to an MI
24646 consumer as a @samp{displayhint} attribute of the variable being
24649 This method is optional. If it does exist, this method must return a
24652 Some display hints are predefined by @value{GDBN}:
24656 Indicate that the object being printed is ``array-like''. The CLI
24657 uses this to respect parameters such as @code{set print elements} and
24658 @code{set print array}.
24661 Indicate that the object being printed is ``map-like'', and that the
24662 children of this value can be assumed to alternate between keys and
24666 Indicate that the object being printed is ``string-like''. If the
24667 printer's @code{to_string} method returns a Python string of some
24668 kind, then @value{GDBN} will call its internal language-specific
24669 string-printing function to format the string. For the CLI this means
24670 adding quotation marks, possibly escaping some characters, respecting
24671 @code{set print elements}, and the like.
24675 @defun pretty_printer.to_string (self)
24676 @value{GDBN} will call this method to display the string
24677 representation of the value passed to the object's constructor.
24679 When printing from the CLI, if the @code{to_string} method exists,
24680 then @value{GDBN} will prepend its result to the values returned by
24681 @code{children}. Exactly how this formatting is done is dependent on
24682 the display hint, and may change as more hints are added. Also,
24683 depending on the print settings (@pxref{Print Settings}), the CLI may
24684 print just the result of @code{to_string} in a stack trace, omitting
24685 the result of @code{children}.
24687 If this method returns a string, it is printed verbatim.
24689 Otherwise, if this method returns an instance of @code{gdb.Value},
24690 then @value{GDBN} prints this value. This may result in a call to
24691 another pretty-printer.
24693 If instead the method returns a Python value which is convertible to a
24694 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
24695 the resulting value. Again, this may result in a call to another
24696 pretty-printer. Python scalars (integers, floats, and booleans) and
24697 strings are convertible to @code{gdb.Value}; other types are not.
24699 Finally, if this method returns @code{None} then no further operations
24700 are peformed in this method and nothing is printed.
24702 If the result is not one of these types, an exception is raised.
24705 @value{GDBN} provides a function which can be used to look up the
24706 default pretty-printer for a @code{gdb.Value}:
24708 @findex gdb.default_visualizer
24709 @defun gdb.default_visualizer (value)
24710 This function takes a @code{gdb.Value} object as an argument. If a
24711 pretty-printer for this value exists, then it is returned. If no such
24712 printer exists, then this returns @code{None}.
24715 @node Selecting Pretty-Printers
24716 @subsubsection Selecting Pretty-Printers
24718 The Python list @code{gdb.pretty_printers} contains an array of
24719 functions or callable objects that have been registered via addition
24720 as a pretty-printer. Printers in this list are called @code{global}
24721 printers, they're available when debugging all inferiors.
24722 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
24723 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
24726 Each function on these lists is passed a single @code{gdb.Value}
24727 argument and should return a pretty-printer object conforming to the
24728 interface definition above (@pxref{Pretty Printing API}). If a function
24729 cannot create a pretty-printer for the value, it should return
24732 @value{GDBN} first checks the @code{pretty_printers} attribute of each
24733 @code{gdb.Objfile} in the current program space and iteratively calls
24734 each enabled lookup routine in the list for that @code{gdb.Objfile}
24735 until it receives a pretty-printer object.
24736 If no pretty-printer is found in the objfile lists, @value{GDBN} then
24737 searches the pretty-printer list of the current program space,
24738 calling each enabled function until an object is returned.
24739 After these lists have been exhausted, it tries the global
24740 @code{gdb.pretty_printers} list, again calling each enabled function until an
24741 object is returned.
24743 The order in which the objfiles are searched is not specified. For a
24744 given list, functions are always invoked from the head of the list,
24745 and iterated over sequentially until the end of the list, or a printer
24746 object is returned.
24748 For various reasons a pretty-printer may not work.
24749 For example, the underlying data structure may have changed and
24750 the pretty-printer is out of date.
24752 The consequences of a broken pretty-printer are severe enough that
24753 @value{GDBN} provides support for enabling and disabling individual
24754 printers. For example, if @code{print frame-arguments} is on,
24755 a backtrace can become highly illegible if any argument is printed
24756 with a broken printer.
24758 Pretty-printers are enabled and disabled by attaching an @code{enabled}
24759 attribute to the registered function or callable object. If this attribute
24760 is present and its value is @code{False}, the printer is disabled, otherwise
24761 the printer is enabled.
24763 @node Writing a Pretty-Printer
24764 @subsubsection Writing a Pretty-Printer
24765 @cindex writing a pretty-printer
24767 A pretty-printer consists of two parts: a lookup function to detect
24768 if the type is supported, and the printer itself.
24770 Here is an example showing how a @code{std::string} printer might be
24771 written. @xref{Pretty Printing API}, for details on the API this class
24775 class StdStringPrinter(object):
24776 "Print a std::string"
24778 def __init__(self, val):
24781 def to_string(self):
24782 return self.val['_M_dataplus']['_M_p']
24784 def display_hint(self):
24788 And here is an example showing how a lookup function for the printer
24789 example above might be written.
24792 def str_lookup_function(val):
24793 lookup_tag = val.type.tag
24794 if lookup_tag == None:
24796 regex = re.compile("^std::basic_string<char,.*>$")
24797 if regex.match(lookup_tag):
24798 return StdStringPrinter(val)
24802 The example lookup function extracts the value's type, and attempts to
24803 match it to a type that it can pretty-print. If it is a type the
24804 printer can pretty-print, it will return a printer object. If not, it
24805 returns @code{None}.
24807 We recommend that you put your core pretty-printers into a Python
24808 package. If your pretty-printers are for use with a library, we
24809 further recommend embedding a version number into the package name.
24810 This practice will enable @value{GDBN} to load multiple versions of
24811 your pretty-printers at the same time, because they will have
24814 You should write auto-loaded code (@pxref{Python Auto-loading}) such that it
24815 can be evaluated multiple times without changing its meaning. An
24816 ideal auto-load file will consist solely of @code{import}s of your
24817 printer modules, followed by a call to a register pretty-printers with
24818 the current objfile.
24820 Taken as a whole, this approach will scale nicely to multiple
24821 inferiors, each potentially using a different library version.
24822 Embedding a version number in the Python package name will ensure that
24823 @value{GDBN} is able to load both sets of printers simultaneously.
24824 Then, because the search for pretty-printers is done by objfile, and
24825 because your auto-loaded code took care to register your library's
24826 printers with a specific objfile, @value{GDBN} will find the correct
24827 printers for the specific version of the library used by each
24830 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
24831 this code might appear in @code{gdb.libstdcxx.v6}:
24834 def register_printers(objfile):
24835 objfile.pretty_printers.append(str_lookup_function)
24839 And then the corresponding contents of the auto-load file would be:
24842 import gdb.libstdcxx.v6
24843 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
24846 The previous example illustrates a basic pretty-printer.
24847 There are a few things that can be improved on.
24848 The printer doesn't have a name, making it hard to identify in a
24849 list of installed printers. The lookup function has a name, but
24850 lookup functions can have arbitrary, even identical, names.
24852 Second, the printer only handles one type, whereas a library typically has
24853 several types. One could install a lookup function for each desired type
24854 in the library, but one could also have a single lookup function recognize
24855 several types. The latter is the conventional way this is handled.
24856 If a pretty-printer can handle multiple data types, then its
24857 @dfn{subprinters} are the printers for the individual data types.
24859 The @code{gdb.printing} module provides a formal way of solving these
24860 problems (@pxref{gdb.printing}).
24861 Here is another example that handles multiple types.
24863 These are the types we are going to pretty-print:
24866 struct foo @{ int a, b; @};
24867 struct bar @{ struct foo x, y; @};
24870 Here are the printers:
24874 """Print a foo object."""
24876 def __init__(self, val):
24879 def to_string(self):
24880 return ("a=<" + str(self.val["a"]) +
24881 "> b=<" + str(self.val["b"]) + ">")
24884 """Print a bar object."""
24886 def __init__(self, val):
24889 def to_string(self):
24890 return ("x=<" + str(self.val["x"]) +
24891 "> y=<" + str(self.val["y"]) + ">")
24894 This example doesn't need a lookup function, that is handled by the
24895 @code{gdb.printing} module. Instead a function is provided to build up
24896 the object that handles the lookup.
24899 import gdb.printing
24901 def build_pretty_printer():
24902 pp = gdb.printing.RegexpCollectionPrettyPrinter(
24904 pp.add_printer('foo', '^foo$', fooPrinter)
24905 pp.add_printer('bar', '^bar$', barPrinter)
24909 And here is the autoload support:
24912 import gdb.printing
24914 gdb.printing.register_pretty_printer(
24915 gdb.current_objfile(),
24916 my_library.build_pretty_printer())
24919 Finally, when this printer is loaded into @value{GDBN}, here is the
24920 corresponding output of @samp{info pretty-printer}:
24923 (gdb) info pretty-printer
24930 @node Type Printing API
24931 @subsubsection Type Printing API
24932 @cindex type printing API for Python
24934 @value{GDBN} provides a way for Python code to customize type display.
24935 This is mainly useful for substituting canonical typedef names for
24938 @cindex type printer
24939 A @dfn{type printer} is just a Python object conforming to a certain
24940 protocol. A simple base class implementing the protocol is provided;
24941 see @ref{gdb.types}. A type printer must supply at least:
24943 @defivar type_printer enabled
24944 A boolean which is True if the printer is enabled, and False
24945 otherwise. This is manipulated by the @code{enable type-printer}
24946 and @code{disable type-printer} commands.
24949 @defivar type_printer name
24950 The name of the type printer. This must be a string. This is used by
24951 the @code{enable type-printer} and @code{disable type-printer}
24955 @defmethod type_printer instantiate (self)
24956 This is called by @value{GDBN} at the start of type-printing. It is
24957 only called if the type printer is enabled. This method must return a
24958 new object that supplies a @code{recognize} method, as described below.
24962 When displaying a type, say via the @code{ptype} command, @value{GDBN}
24963 will compute a list of type recognizers. This is done by iterating
24964 first over the per-objfile type printers (@pxref{Objfiles In Python}),
24965 followed by the per-progspace type printers (@pxref{Progspaces In
24966 Python}), and finally the global type printers.
24968 @value{GDBN} will call the @code{instantiate} method of each enabled
24969 type printer. If this method returns @code{None}, then the result is
24970 ignored; otherwise, it is appended to the list of recognizers.
24972 Then, when @value{GDBN} is going to display a type name, it iterates
24973 over the list of recognizers. For each one, it calls the recognition
24974 function, stopping if the function returns a non-@code{None} value.
24975 The recognition function is defined as:
24977 @defmethod type_recognizer recognize (self, type)
24978 If @var{type} is not recognized, return @code{None}. Otherwise,
24979 return a string which is to be printed as the name of @var{type}.
24980 @var{type} will be an instance of @code{gdb.Type} (@pxref{Types In
24984 @value{GDBN} uses this two-pass approach so that type printers can
24985 efficiently cache information without holding on to it too long. For
24986 example, it can be convenient to look up type information in a type
24987 printer and hold it for a recognizer's lifetime; if a single pass were
24988 done then type printers would have to make use of the event system in
24989 order to avoid holding information that could become stale as the
24992 @node Frame Filter API
24993 @subsubsection Filtering Frames.
24994 @cindex frame filters api
24996 Frame filters are Python objects that manipulate the visibility of a
24997 frame or frames when a backtrace (@pxref{Backtrace}) is printed by
25000 Only commands that print a backtrace, or, in the case of @sc{gdb/mi}
25001 commands (@pxref{GDB/MI}), those that return a collection of frames
25002 are affected. The commands that work with frame filters are:
25004 @code{backtrace} (@pxref{backtrace-command,, The backtrace command}),
25005 @code{-stack-list-frames}
25006 (@pxref{-stack-list-frames,, The -stack-list-frames command}),
25007 @code{-stack-list-variables} (@pxref{-stack-list-variables,, The
25008 -stack-list-variables command}), @code{-stack-list-arguments}
25009 @pxref{-stack-list-arguments,, The -stack-list-arguments command}) and
25010 @code{-stack-list-locals} (@pxref{-stack-list-locals,, The
25011 -stack-list-locals command}).
25013 A frame filter works by taking an iterator as an argument, applying
25014 actions to the contents of that iterator, and returning another
25015 iterator (or, possibly, the same iterator it was provided in the case
25016 where the filter does not perform any operations). Typically, frame
25017 filters utilize tools such as the Python's @code{itertools} module to
25018 work with and create new iterators from the source iterator.
25019 Regardless of how a filter chooses to apply actions, it must not alter
25020 the underlying @value{GDBN} frame or frames, or attempt to alter the
25021 call-stack within @value{GDBN}. This preserves data integrity within
25022 @value{GDBN}. Frame filters are executed on a priority basis and care
25023 should be taken that some frame filters may have been executed before,
25024 and that some frame filters will be executed after.
25026 An important consideration when designing frame filters, and well
25027 worth reflecting upon, is that frame filters should avoid unwinding
25028 the call stack if possible. Some stacks can run very deep, into the
25029 tens of thousands in some cases. To search every frame when a frame
25030 filter executes may be too expensive at that step. The frame filter
25031 cannot know how many frames it has to iterate over, and it may have to
25032 iterate through them all. This ends up duplicating effort as
25033 @value{GDBN} performs this iteration when it prints the frames. If
25034 the filter can defer unwinding frames until frame decorators are
25035 executed, after the last filter has executed, it should. @xref{Frame
25036 Decorator API}, for more information on decorators. Also, there are
25037 examples for both frame decorators and filters in later chapters.
25038 @xref{Writing a Frame Filter}, for more information.
25040 The Python dictionary @code{gdb.frame_filters} contains key/object
25041 pairings that comprise a frame filter. Frame filters in this
25042 dictionary are called @code{global} frame filters, and they are
25043 available when debugging all inferiors. These frame filters must
25044 register with the dictionary directly. In addition to the
25045 @code{global} dictionary, there are other dictionaries that are loaded
25046 with different inferiors via auto-loading (@pxref{Python
25047 Auto-loading}). The two other areas where frame filter dictionaries
25048 can be found are: @code{gdb.Progspace} which contains a
25049 @code{frame_filters} dictionary attribute, and each @code{gdb.Objfile}
25050 object which also contains a @code{frame_filters} dictionary
25053 When a command is executed from @value{GDBN} that is compatible with
25054 frame filters, @value{GDBN} combines the @code{global},
25055 @code{gdb.Progspace} and all @code{gdb.Objfile} dictionaries currently
25056 loaded. All of the @code{gdb.Objfile} dictionaries are combined, as
25057 several frames, and thus several object files, might be in use.
25058 @value{GDBN} then prunes any frame filter whose @code{enabled}
25059 attribute is @code{False}. This pruned list is then sorted according
25060 to the @code{priority} attribute in each filter.
25062 Once the dictionaries are combined, pruned and sorted, @value{GDBN}
25063 creates an iterator which wraps each frame in the call stack in a
25064 @code{FrameDecorator} object, and calls each filter in order. The
25065 output from the previous filter will always be the input to the next
25068 Frame filters have a mandatory interface which each frame filter must
25069 implement, defined here:
25071 @defun FrameFilter.filter (iterator)
25072 @value{GDBN} will call this method on a frame filter when it has
25073 reached the order in the priority list for that filter.
25075 For example, if there are four frame filters:
25086 The order that the frame filters will be called is:
25089 Filter3 -> Filter2 -> Filter1 -> Filter4
25092 Note that the output from @code{Filter3} is passed to the input of
25093 @code{Filter2}, and so on.
25095 This @code{filter} method is passed a Python iterator. This iterator
25096 contains a sequence of frame decorators that wrap each
25097 @code{gdb.Frame}, or a frame decorator that wraps another frame
25098 decorator. The first filter that is executed in the sequence of frame
25099 filters will receive an iterator entirely comprised of default
25100 @code{FrameDecorator} objects. However, after each frame filter is
25101 executed, the previous frame filter may have wrapped some or all of
25102 the frame decorators with their own frame decorator. As frame
25103 decorators must also conform to a mandatory interface, these
25104 decorators can be assumed to act in a uniform manner (@pxref{Frame
25107 This method must return an object conforming to the Python iterator
25108 protocol. Each item in the iterator must be an object conforming to
25109 the frame decorator interface. If a frame filter does not wish to
25110 perform any operations on this iterator, it should return that
25111 iterator untouched.
25113 This method is not optional. If it does not exist, @value{GDBN} will
25114 raise and print an error.
25117 @defvar FrameFilter.name
25118 The @code{name} attribute must be Python string which contains the
25119 name of the filter displayed by @value{GDBN} (@pxref{Frame Filter
25120 Management}). This attribute may contain any combination of letters
25121 or numbers. Care should be taken to ensure that it is unique. This
25122 attribute is mandatory.
25125 @defvar FrameFilter.enabled
25126 The @code{enabled} attribute must be Python boolean. This attribute
25127 indicates to @value{GDBN} whether the frame filter is enabled, and
25128 should be considered when frame filters are executed. If
25129 @code{enabled} is @code{True}, then the frame filter will be executed
25130 when any of the backtrace commands detailed earlier in this chapter
25131 are executed. If @code{enabled} is @code{False}, then the frame
25132 filter will not be executed. This attribute is mandatory.
25135 @defvar FrameFilter.priority
25136 The @code{priority} attribute must be Python integer. This attribute
25137 controls the order of execution in relation to other frame filters.
25138 There are no imposed limits on the range of @code{priority} other than
25139 it must be a valid integer. The higher the @code{priority} attribute,
25140 the sooner the frame filter will be executed in relation to other
25141 frame filters. Although @code{priority} can be negative, it is
25142 recommended practice to assume zero is the lowest priority that a
25143 frame filter can be assigned. Frame filters that have the same
25144 priority are executed in unsorted order in that priority slot. This
25145 attribute is mandatory.
25148 @node Frame Decorator API
25149 @subsubsection Decorating Frames.
25150 @cindex frame decorator api
25152 Frame decorators are sister objects to frame filters (@pxref{Frame
25153 Filter API}). Frame decorators are applied by a frame filter and can
25154 only be used in conjunction with frame filters.
25156 The purpose of a frame decorator is to customize the printed content
25157 of each @code{gdb.Frame} in commands where frame filters are executed.
25158 This concept is called decorating a frame. Frame decorators decorate
25159 a @code{gdb.Frame} with Python code contained within each API call.
25160 This separates the actual data contained in a @code{gdb.Frame} from
25161 the decorated data produced by a frame decorator. This abstraction is
25162 necessary to maintain integrity of the data contained in each
25165 Frame decorators have a mandatory interface, defined below.
25167 @value{GDBN} already contains a frame decorator called
25168 @code{FrameDecorator}. This contains substantial amounts of
25169 boilerplate code to decorate the content of a @code{gdb.Frame}. It is
25170 recommended that other frame decorators inherit and extend this
25171 object, and only to override the methods needed.
25173 @defun FrameDecorator.elided (self)
25175 The @code{elided} method groups frames together in a hierarchical
25176 system. An example would be an interpreter, where multiple low-level
25177 frames make up a single call in the interpreted language. In this
25178 example, the frame filter would elide the low-level frames and present
25179 a single high-level frame, representing the call in the interpreted
25180 language, to the user.
25182 The @code{elided} function must return an iterable and this iterable
25183 must contain the frames that are being elided wrapped in a suitable
25184 frame decorator. If no frames are being elided this function may
25185 return an empty iterable, or @code{None}. Elided frames are indented
25186 from normal frames in a @code{CLI} backtrace, or in the case of
25187 @code{GDB/MI}, are placed in the @code{children} field of the eliding
25190 It is the frame filter's task to also filter out the elided frames from
25191 the source iterator. This will avoid printing the frame twice.
25194 @defun FrameDecorator.function (self)
25196 This method returns the name of the function in the frame that is to
25199 This method must return a Python string describing the function, or
25202 If this function returns @code{None}, @value{GDBN} will not print any
25203 data for this field.
25206 @defun FrameDecorator.address (self)
25208 This method returns the address of the frame that is to be printed.
25210 This method must return a Python numeric integer type of sufficient
25211 size to describe the address of the frame, or @code{None}.
25213 If this function returns a @code{None}, @value{GDBN} will not print
25214 any data for this field.
25217 @defun FrameDecorator.filename (self)
25219 This method returns the filename and path associated with this frame.
25221 This method must return a Python string containing the filename and
25222 the path to the object file backing the frame, or @code{None}.
25224 If this function returns a @code{None}, @value{GDBN} will not print
25225 any data for this field.
25228 @defun FrameDecorator.line (self):
25230 This method returns the line number associated with the current
25231 position within the function addressed by this frame.
25233 This method must return a Python integer type, or @code{None}.
25235 If this function returns a @code{None}, @value{GDBN} will not print
25236 any data for this field.
25239 @defun FrameDecorator.frame_args (self)
25240 @anchor{frame_args}
25242 This method must return an iterable, or @code{None}. Returning an
25243 empty iterable, or @code{None} means frame arguments will not be
25244 printed for this frame. This iterable must contain objects that
25245 implement two methods, described here.
25247 This object must implement a @code{argument} method which takes a
25248 single @code{self} parameter and must return a @code{gdb.Symbol}
25249 (@pxref{Symbols In Python}), or a Python string. The object must also
25250 implement a @code{value} method which takes a single @code{self}
25251 parameter and must return a @code{gdb.Value} (@pxref{Values From
25252 Inferior}), a Python value, or @code{None}. If the @code{value}
25253 method returns @code{None}, and the @code{argument} method returns a
25254 @code{gdb.Symbol}, @value{GDBN} will look-up and print the value of
25255 the @code{gdb.Symbol} automatically.
25260 class SymValueWrapper():
25262 def __init__(self, symbol, value):
25272 class SomeFrameDecorator()
25275 def frame_args(self):
25278 block = self.inferior_frame.block()
25282 # Iterate over all symbols in a block. Only add
25283 # symbols that are arguments.
25285 if not sym.is_argument:
25287 args.append(SymValueWrapper(sym,None))
25289 # Add example synthetic argument.
25290 args.append(SymValueWrapper(``foo'', 42))
25296 @defun FrameDecorator.frame_locals (self)
25298 This method must return an iterable or @code{None}. Returning an
25299 empty iterable, or @code{None} means frame local arguments will not be
25300 printed for this frame.
25302 The object interface, the description of the various strategies for
25303 reading frame locals, and the example are largely similar to those
25304 described in the @code{frame_args} function, (@pxref{frame_args,,The
25305 frame filter frame_args function}). Below is a modified example:
25308 class SomeFrameDecorator()
25311 def frame_locals(self):
25314 block = self.inferior_frame.block()
25318 # Iterate over all symbols in a block. Add all
25319 # symbols, except arguments.
25321 if sym.is_argument:
25323 vars.append(SymValueWrapper(sym,None))
25325 # Add an example of a synthetic local variable.
25326 vars.append(SymValueWrapper(``bar'', 99))
25332 @defun FrameDecorator.inferior_frame (self):
25334 This method must return the underlying @code{gdb.Frame} that this
25335 frame decorator is decorating. @value{GDBN} requires the underlying
25336 frame for internal frame information to determine how to print certain
25337 values when printing a frame.
25340 @node Writing a Frame Filter
25341 @subsubsection Writing a Frame Filter
25342 @cindex writing a frame filter
25344 There are three basic elements that a frame filter must implement: it
25345 must correctly implement the documented interface (@pxref{Frame Filter
25346 API}), it must register itself with @value{GDBN}, and finally, it must
25347 decide if it is to work on the data provided by @value{GDBN}. In all
25348 cases, whether it works on the iterator or not, each frame filter must
25349 return an iterator. A bare-bones frame filter follows the pattern in
25350 the following example.
25355 class FrameFilter():
25357 def __init__(self):
25358 # Frame filter attribute creation.
25360 # 'name' is the name of the filter that GDB will display.
25362 # 'priority' is the priority of the filter relative to other
25365 # 'enabled' is a boolean that indicates whether this filter is
25366 # enabled and should be executed.
25369 self.priority = 100
25370 self.enabled = True
25372 # Register this frame filter with the global frame_filters
25374 gdb.frame_filters[self.name] = self
25376 def filter(self, frame_iter):
25377 # Just return the iterator.
25381 The frame filter in the example above implements the three
25382 requirements for all frame filters. It implements the API, self
25383 registers, and makes a decision on the iterator (in this case, it just
25384 returns the iterator untouched).
25386 The first step is attribute creation and assignment, and as shown in
25387 the comments the filter assigns the following attributes: @code{name},
25388 @code{priority} and whether the filter should be enabled with the
25389 @code{enabled} attribute.
25391 The second step is registering the frame filter with the dictionary or
25392 dictionaries that the frame filter has interest in. As shown in the
25393 comments, this filter just registers itself with the global dictionary
25394 @code{gdb.frame_filters}. As noted earlier, @code{gdb.frame_filters}
25395 is a dictionary that is initialized in the @code{gdb} module when
25396 @value{GDBN} starts. What dictionary a filter registers with is an
25397 important consideration. Generally, if a filter is specific to a set
25398 of code, it should be registered either in the @code{objfile} or
25399 @code{progspace} dictionaries as they are specific to the program
25400 currently loaded in @value{GDBN}. The global dictionary is always
25401 present in @value{GDBN} and is never unloaded. Any filters registered
25402 with the global dictionary will exist until @value{GDBN} exits. To
25403 avoid filters that may conflict, it is generally better to register
25404 frame filters against the dictionaries that more closely align with
25405 the usage of the filter currently in question. @xref{Python
25406 Auto-loading}, for further information on auto-loading Python scripts.
25408 @value{GDBN} takes a hands-off approach to frame filter registration,
25409 therefore it is the frame filter's responsibility to ensure
25410 registration has occurred, and that any exceptions are handled
25411 appropriately. In particular, you may wish to handle exceptions
25412 relating to Python dictionary key uniqueness. It is mandatory that
25413 the dictionary key is the same as frame filter's @code{name}
25414 attribute. When a user manages frame filters (@pxref{Frame Filter
25415 Management}), the names @value{GDBN} will display are those contained
25416 in the @code{name} attribute.
25418 The final step of this example is the implementation of the
25419 @code{filter} method. As shown in the example comments, we define the
25420 @code{filter} method and note that the method must take an iterator,
25421 and also must return an iterator. In this bare-bones example, the
25422 frame filter is not very useful as it just returns the iterator
25423 untouched. However this is a valid operation for frame filters that
25424 have the @code{enabled} attribute set, but decide not to operate on
25427 In the next example, the frame filter operates on all frames and
25428 utilizes a frame decorator to perform some work on the frames.
25429 @xref{Frame Decorator API}, for further information on the frame
25430 decorator interface.
25432 This example works on inlined frames. It highlights frames which are
25433 inlined by tagging them with an ``[inlined]'' tag. By applying a
25434 frame decorator to all frames with the Python @code{itertools imap}
25435 method, the example defers actions to the frame decorator. Frame
25436 decorators are only processed when @value{GDBN} prints the backtrace.
25438 This introduces a new decision making topic: whether to perform
25439 decision making operations at the filtering step, or at the printing
25440 step. In this example's approach, it does not perform any filtering
25441 decisions at the filtering step beyond mapping a frame decorator to
25442 each frame. This allows the actual decision making to be performed
25443 when each frame is printed. This is an important consideration, and
25444 well worth reflecting upon when designing a frame filter. An issue
25445 that frame filters should avoid is unwinding the stack if possible.
25446 Some stacks can run very deep, into the tens of thousands in some
25447 cases. To search every frame to determine if it is inlined ahead of
25448 time may be too expensive at the filtering step. The frame filter
25449 cannot know how many frames it has to iterate over, and it would have
25450 to iterate through them all. This ends up duplicating effort as
25451 @value{GDBN} performs this iteration when it prints the frames.
25453 In this example decision making can be deferred to the printing step.
25454 As each frame is printed, the frame decorator can examine each frame
25455 in turn when @value{GDBN} iterates. From a performance viewpoint,
25456 this is the most appropriate decision to make as it avoids duplicating
25457 the effort that the printing step would undertake anyway. Also, if
25458 there are many frame filters unwinding the stack during filtering, it
25459 can substantially delay the printing of the backtrace which will
25460 result in large memory usage, and a poor user experience.
25463 class InlineFilter():
25465 def __init__(self):
25466 self.name = "InlinedFrameFilter"
25467 self.priority = 100
25468 self.enabled = True
25469 gdb.frame_filters[self.name] = self
25471 def filter(self, frame_iter):
25472 frame_iter = itertools.imap(InlinedFrameDecorator,
25477 This frame filter is somewhat similar to the earlier example, except
25478 that the @code{filter} method applies a frame decorator object called
25479 @code{InlinedFrameDecorator} to each element in the iterator. The
25480 @code{imap} Python method is light-weight. It does not proactively
25481 iterate over the iterator, but rather creates a new iterator which
25482 wraps the existing one.
25484 Below is the frame decorator for this example.
25487 class InlinedFrameDecorator(FrameDecorator):
25489 def __init__(self, fobj):
25490 super(InlinedFrameDecorator, self).__init__(fobj)
25492 def function(self):
25493 frame = fobj.inferior_frame()
25494 name = str(frame.name())
25496 if frame.type() == gdb.INLINE_FRAME:
25497 name = name + " [inlined]"
25502 This frame decorator only defines and overrides the @code{function}
25503 method. It lets the supplied @code{FrameDecorator}, which is shipped
25504 with @value{GDBN}, perform the other work associated with printing
25507 The combination of these two objects create this output from a
25511 #0 0x004004e0 in bar () at inline.c:11
25512 #1 0x00400566 in max [inlined] (b=6, a=12) at inline.c:21
25513 #2 0x00400566 in main () at inline.c:31
25516 So in the case of this example, a frame decorator is applied to all
25517 frames, regardless of whether they may be inlined or not. As
25518 @value{GDBN} iterates over the iterator produced by the frame filters,
25519 @value{GDBN} executes each frame decorator which then makes a decision
25520 on what to print in the @code{function} callback. Using a strategy
25521 like this is a way to defer decisions on the frame content to printing
25524 @subheading Eliding Frames
25526 It might be that the above example is not desirable for representing
25527 inlined frames, and a hierarchical approach may be preferred. If we
25528 want to hierarchically represent frames, the @code{elided} frame
25529 decorator interface might be preferable.
25531 This example approaches the issue with the @code{elided} method. This
25532 example is quite long, but very simplistic. It is out-of-scope for
25533 this section to write a complete example that comprehensively covers
25534 all approaches of finding and printing inlined frames. However, this
25535 example illustrates the approach an author might use.
25537 This example comprises of three sections.
25540 class InlineFrameFilter():
25542 def __init__(self):
25543 self.name = "InlinedFrameFilter"
25544 self.priority = 100
25545 self.enabled = True
25546 gdb.frame_filters[self.name] = self
25548 def filter(self, frame_iter):
25549 return ElidingInlineIterator(frame_iter)
25552 This frame filter is very similar to the other examples. The only
25553 difference is this frame filter is wrapping the iterator provided to
25554 it (@code{frame_iter}) with a custom iterator called
25555 @code{ElidingInlineIterator}. This again defers actions to when
25556 @value{GDBN} prints the backtrace, as the iterator is not traversed
25559 The iterator for this example is as follows. It is in this section of
25560 the example where decisions are made on the content of the backtrace.
25563 class ElidingInlineIterator:
25564 def __init__(self, ii):
25565 self.input_iterator = ii
25567 def __iter__(self):
25571 frame = next(self.input_iterator)
25573 if frame.inferior_frame().type() != gdb.INLINE_FRAME:
25577 eliding_frame = next(self.input_iterator)
25578 except StopIteration:
25580 return ElidingFrameDecorator(eliding_frame, [frame])
25583 This iterator implements the Python iterator protocol. When the
25584 @code{next} function is called (when @value{GDBN} prints each frame),
25585 the iterator checks if this frame decorator, @code{frame}, is wrapping
25586 an inlined frame. If it is not, it returns the existing frame decorator
25587 untouched. If it is wrapping an inlined frame, it assumes that the
25588 inlined frame was contained within the next oldest frame,
25589 @code{eliding_frame}, which it fetches. It then creates and returns a
25590 frame decorator, @code{ElidingFrameDecorator}, which contains both the
25591 elided frame, and the eliding frame.
25594 class ElidingInlineDecorator(FrameDecorator):
25596 def __init__(self, frame, elided_frames):
25597 super(ElidingInlineDecorator, self).__init__(frame)
25599 self.elided_frames = elided_frames
25602 return iter(self.elided_frames)
25605 This frame decorator overrides one function and returns the inlined
25606 frame in the @code{elided} method. As before it lets
25607 @code{FrameDecorator} do the rest of the work involved in printing
25608 this frame. This produces the following output.
25611 #0 0x004004e0 in bar () at inline.c:11
25612 #2 0x00400529 in main () at inline.c:25
25613 #1 0x00400529 in max (b=6, a=12) at inline.c:15
25616 In that output, @code{max} which has been inlined into @code{main} is
25617 printed hierarchically. Another approach would be to combine the
25618 @code{function} method, and the @code{elided} method to both print a
25619 marker in the inlined frame, and also show the hierarchical
25622 @node Inferiors In Python
25623 @subsubsection Inferiors In Python
25624 @cindex inferiors in Python
25626 @findex gdb.Inferior
25627 Programs which are being run under @value{GDBN} are called inferiors
25628 (@pxref{Inferiors and Programs}). Python scripts can access
25629 information about and manipulate inferiors controlled by @value{GDBN}
25630 via objects of the @code{gdb.Inferior} class.
25632 The following inferior-related functions are available in the @code{gdb}
25635 @defun gdb.inferiors ()
25636 Return a tuple containing all inferior objects.
25639 @defun gdb.selected_inferior ()
25640 Return an object representing the current inferior.
25643 A @code{gdb.Inferior} object has the following attributes:
25645 @defvar Inferior.num
25646 ID of inferior, as assigned by GDB.
25649 @defvar Inferior.pid
25650 Process ID of the inferior, as assigned by the underlying operating
25654 @defvar Inferior.was_attached
25655 Boolean signaling whether the inferior was created using `attach', or
25656 started by @value{GDBN} itself.
25659 A @code{gdb.Inferior} object has the following methods:
25661 @defun Inferior.is_valid ()
25662 Returns @code{True} if the @code{gdb.Inferior} object is valid,
25663 @code{False} if not. A @code{gdb.Inferior} object will become invalid
25664 if the inferior no longer exists within @value{GDBN}. All other
25665 @code{gdb.Inferior} methods will throw an exception if it is invalid
25666 at the time the method is called.
25669 @defun Inferior.threads ()
25670 This method returns a tuple holding all the threads which are valid
25671 when it is called. If there are no valid threads, the method will
25672 return an empty tuple.
25675 @findex Inferior.read_memory
25676 @defun Inferior.read_memory (address, length)
25677 Read @var{length} bytes of memory from the inferior, starting at
25678 @var{address}. Returns a buffer object, which behaves much like an array
25679 or a string. It can be modified and given to the
25680 @code{Inferior.write_memory} function. In @code{Python} 3, the return
25681 value is a @code{memoryview} object.
25684 @findex Inferior.write_memory
25685 @defun Inferior.write_memory (address, buffer @r{[}, length@r{]})
25686 Write the contents of @var{buffer} to the inferior, starting at
25687 @var{address}. The @var{buffer} parameter must be a Python object
25688 which supports the buffer protocol, i.e., a string, an array or the
25689 object returned from @code{Inferior.read_memory}. If given, @var{length}
25690 determines the number of bytes from @var{buffer} to be written.
25693 @findex gdb.search_memory
25694 @defun Inferior.search_memory (address, length, pattern)
25695 Search a region of the inferior memory starting at @var{address} with
25696 the given @var{length} using the search pattern supplied in
25697 @var{pattern}. The @var{pattern} parameter must be a Python object
25698 which supports the buffer protocol, i.e., a string, an array or the
25699 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
25700 containing the address where the pattern was found, or @code{None} if
25701 the pattern could not be found.
25704 @node Events In Python
25705 @subsubsection Events In Python
25706 @cindex inferior events in Python
25708 @value{GDBN} provides a general event facility so that Python code can be
25709 notified of various state changes, particularly changes that occur in
25712 An @dfn{event} is just an object that describes some state change. The
25713 type of the object and its attributes will vary depending on the details
25714 of the change. All the existing events are described below.
25716 In order to be notified of an event, you must register an event handler
25717 with an @dfn{event registry}. An event registry is an object in the
25718 @code{gdb.events} module which dispatches particular events. A registry
25719 provides methods to register and unregister event handlers:
25721 @defun EventRegistry.connect (object)
25722 Add the given callable @var{object} to the registry. This object will be
25723 called when an event corresponding to this registry occurs.
25726 @defun EventRegistry.disconnect (object)
25727 Remove the given @var{object} from the registry. Once removed, the object
25728 will no longer receive notifications of events.
25731 Here is an example:
25734 def exit_handler (event):
25735 print "event type: exit"
25736 print "exit code: %d" % (event.exit_code)
25738 gdb.events.exited.connect (exit_handler)
25741 In the above example we connect our handler @code{exit_handler} to the
25742 registry @code{events.exited}. Once connected, @code{exit_handler} gets
25743 called when the inferior exits. The argument @dfn{event} in this example is
25744 of type @code{gdb.ExitedEvent}. As you can see in the example the
25745 @code{ExitedEvent} object has an attribute which indicates the exit code of
25748 The following is a listing of the event registries that are available and
25749 details of the events they emit:
25754 Emits @code{gdb.ThreadEvent}.
25756 Some events can be thread specific when @value{GDBN} is running in non-stop
25757 mode. When represented in Python, these events all extend
25758 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
25759 events which are emitted by this or other modules might extend this event.
25760 Examples of these events are @code{gdb.BreakpointEvent} and
25761 @code{gdb.ContinueEvent}.
25763 @defvar ThreadEvent.inferior_thread
25764 In non-stop mode this attribute will be set to the specific thread which was
25765 involved in the emitted event. Otherwise, it will be set to @code{None}.
25768 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
25770 This event indicates that the inferior has been continued after a stop. For
25771 inherited attribute refer to @code{gdb.ThreadEvent} above.
25773 @item events.exited
25774 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
25775 @code{events.ExitedEvent} has two attributes:
25776 @defvar ExitedEvent.exit_code
25777 An integer representing the exit code, if available, which the inferior
25778 has returned. (The exit code could be unavailable if, for example,
25779 @value{GDBN} detaches from the inferior.) If the exit code is unavailable,
25780 the attribute does not exist.
25782 @defvar ExitedEvent inferior
25783 A reference to the inferior which triggered the @code{exited} event.
25787 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
25789 Indicates that the inferior has stopped. All events emitted by this registry
25790 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
25791 will indicate the stopped thread when @value{GDBN} is running in non-stop
25792 mode. Refer to @code{gdb.ThreadEvent} above for more details.
25794 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
25796 This event indicates that the inferior or one of its threads has received as
25797 signal. @code{gdb.SignalEvent} has the following attributes:
25799 @defvar SignalEvent.stop_signal
25800 A string representing the signal received by the inferior. A list of possible
25801 signal values can be obtained by running the command @code{info signals} in
25802 the @value{GDBN} command prompt.
25805 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
25807 @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have
25808 been hit, and has the following attributes:
25810 @defvar BreakpointEvent.breakpoints
25811 A sequence containing references to all the breakpoints (type
25812 @code{gdb.Breakpoint}) that were hit.
25813 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
25815 @defvar BreakpointEvent.breakpoint
25816 A reference to the first breakpoint that was hit.
25817 This function is maintained for backward compatibility and is now deprecated
25818 in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute.
25821 @item events.new_objfile
25822 Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has
25823 been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute:
25825 @defvar NewObjFileEvent.new_objfile
25826 A reference to the object file (@code{gdb.Objfile}) which has been loaded.
25827 @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object.
25832 @node Threads In Python
25833 @subsubsection Threads In Python
25834 @cindex threads in python
25836 @findex gdb.InferiorThread
25837 Python scripts can access information about, and manipulate inferior threads
25838 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
25840 The following thread-related functions are available in the @code{gdb}
25843 @findex gdb.selected_thread
25844 @defun gdb.selected_thread ()
25845 This function returns the thread object for the selected thread. If there
25846 is no selected thread, this will return @code{None}.
25849 A @code{gdb.InferiorThread} object has the following attributes:
25851 @defvar InferiorThread.name
25852 The name of the thread. If the user specified a name using
25853 @code{thread name}, then this returns that name. Otherwise, if an
25854 OS-supplied name is available, then it is returned. Otherwise, this
25855 returns @code{None}.
25857 This attribute can be assigned to. The new value must be a string
25858 object, which sets the new name, or @code{None}, which removes any
25859 user-specified thread name.
25862 @defvar InferiorThread.num
25863 ID of the thread, as assigned by GDB.
25866 @defvar InferiorThread.ptid
25867 ID of the thread, as assigned by the operating system. This attribute is a
25868 tuple containing three integers. The first is the Process ID (PID); the second
25869 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
25870 Either the LWPID or TID may be 0, which indicates that the operating system
25871 does not use that identifier.
25874 A @code{gdb.InferiorThread} object has the following methods:
25876 @defun InferiorThread.is_valid ()
25877 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
25878 @code{False} if not. A @code{gdb.InferiorThread} object will become
25879 invalid if the thread exits, or the inferior that the thread belongs
25880 is deleted. All other @code{gdb.InferiorThread} methods will throw an
25881 exception if it is invalid at the time the method is called.
25884 @defun InferiorThread.switch ()
25885 This changes @value{GDBN}'s currently selected thread to the one represented
25889 @defun InferiorThread.is_stopped ()
25890 Return a Boolean indicating whether the thread is stopped.
25893 @defun InferiorThread.is_running ()
25894 Return a Boolean indicating whether the thread is running.
25897 @defun InferiorThread.is_exited ()
25898 Return a Boolean indicating whether the thread is exited.
25901 @node Commands In Python
25902 @subsubsection Commands In Python
25904 @cindex commands in python
25905 @cindex python commands
25906 You can implement new @value{GDBN} CLI commands in Python. A CLI
25907 command is implemented using an instance of the @code{gdb.Command}
25908 class, most commonly using a subclass.
25910 @defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]})
25911 The object initializer for @code{Command} registers the new command
25912 with @value{GDBN}. This initializer is normally invoked from the
25913 subclass' own @code{__init__} method.
25915 @var{name} is the name of the command. If @var{name} consists of
25916 multiple words, then the initial words are looked for as prefix
25917 commands. In this case, if one of the prefix commands does not exist,
25918 an exception is raised.
25920 There is no support for multi-line commands.
25922 @var{command_class} should be one of the @samp{COMMAND_} constants
25923 defined below. This argument tells @value{GDBN} how to categorize the
25924 new command in the help system.
25926 @var{completer_class} is an optional argument. If given, it should be
25927 one of the @samp{COMPLETE_} constants defined below. This argument
25928 tells @value{GDBN} how to perform completion for this command. If not
25929 given, @value{GDBN} will attempt to complete using the object's
25930 @code{complete} method (see below); if no such method is found, an
25931 error will occur when completion is attempted.
25933 @var{prefix} is an optional argument. If @code{True}, then the new
25934 command is a prefix command; sub-commands of this command may be
25937 The help text for the new command is taken from the Python
25938 documentation string for the command's class, if there is one. If no
25939 documentation string is provided, the default value ``This command is
25940 not documented.'' is used.
25943 @cindex don't repeat Python command
25944 @defun Command.dont_repeat ()
25945 By default, a @value{GDBN} command is repeated when the user enters a
25946 blank line at the command prompt. A command can suppress this
25947 behavior by invoking the @code{dont_repeat} method. This is similar
25948 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
25951 @defun Command.invoke (argument, from_tty)
25952 This method is called by @value{GDBN} when this command is invoked.
25954 @var{argument} is a string. It is the argument to the command, after
25955 leading and trailing whitespace has been stripped.
25957 @var{from_tty} is a boolean argument. When true, this means that the
25958 command was entered by the user at the terminal; when false it means
25959 that the command came from elsewhere.
25961 If this method throws an exception, it is turned into a @value{GDBN}
25962 @code{error} call. Otherwise, the return value is ignored.
25964 @findex gdb.string_to_argv
25965 To break @var{argument} up into an argv-like string use
25966 @code{gdb.string_to_argv}. This function behaves identically to
25967 @value{GDBN}'s internal argument lexer @code{buildargv}.
25968 It is recommended to use this for consistency.
25969 Arguments are separated by spaces and may be quoted.
25973 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
25974 ['1', '2 "3', '4 "5', "6 '7"]
25979 @cindex completion of Python commands
25980 @defun Command.complete (text, word)
25981 This method is called by @value{GDBN} when the user attempts
25982 completion on this command. All forms of completion are handled by
25983 this method, that is, the @key{TAB} and @key{M-?} key bindings
25984 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
25987 The arguments @var{text} and @var{word} are both strings. @var{text}
25988 holds the complete command line up to the cursor's location.
25989 @var{word} holds the last word of the command line; this is computed
25990 using a word-breaking heuristic.
25992 The @code{complete} method can return several values:
25995 If the return value is a sequence, the contents of the sequence are
25996 used as the completions. It is up to @code{complete} to ensure that the
25997 contents actually do complete the word. A zero-length sequence is
25998 allowed, it means that there were no completions available. Only
25999 string elements of the sequence are used; other elements in the
26000 sequence are ignored.
26003 If the return value is one of the @samp{COMPLETE_} constants defined
26004 below, then the corresponding @value{GDBN}-internal completion
26005 function is invoked, and its result is used.
26008 All other results are treated as though there were no available
26013 When a new command is registered, it must be declared as a member of
26014 some general class of commands. This is used to classify top-level
26015 commands in the on-line help system; note that prefix commands are not
26016 listed under their own category but rather that of their top-level
26017 command. The available classifications are represented by constants
26018 defined in the @code{gdb} module:
26021 @findex COMMAND_NONE
26022 @findex gdb.COMMAND_NONE
26023 @item gdb.COMMAND_NONE
26024 The command does not belong to any particular class. A command in
26025 this category will not be displayed in any of the help categories.
26027 @findex COMMAND_RUNNING
26028 @findex gdb.COMMAND_RUNNING
26029 @item gdb.COMMAND_RUNNING
26030 The command is related to running the inferior. For example,
26031 @code{start}, @code{step}, and @code{continue} are in this category.
26032 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
26033 commands in this category.
26035 @findex COMMAND_DATA
26036 @findex gdb.COMMAND_DATA
26037 @item gdb.COMMAND_DATA
26038 The command is related to data or variables. For example,
26039 @code{call}, @code{find}, and @code{print} are in this category. Type
26040 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
26043 @findex COMMAND_STACK
26044 @findex gdb.COMMAND_STACK
26045 @item gdb.COMMAND_STACK
26046 The command has to do with manipulation of the stack. For example,
26047 @code{backtrace}, @code{frame}, and @code{return} are in this
26048 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
26049 list of commands in this category.
26051 @findex COMMAND_FILES
26052 @findex gdb.COMMAND_FILES
26053 @item gdb.COMMAND_FILES
26054 This class is used for file-related commands. For example,
26055 @code{file}, @code{list} and @code{section} are in this category.
26056 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
26057 commands in this category.
26059 @findex COMMAND_SUPPORT
26060 @findex gdb.COMMAND_SUPPORT
26061 @item gdb.COMMAND_SUPPORT
26062 This should be used for ``support facilities'', generally meaning
26063 things that are useful to the user when interacting with @value{GDBN},
26064 but not related to the state of the inferior. For example,
26065 @code{help}, @code{make}, and @code{shell} are in this category. Type
26066 @kbd{help support} at the @value{GDBN} prompt to see a list of
26067 commands in this category.
26069 @findex COMMAND_STATUS
26070 @findex gdb.COMMAND_STATUS
26071 @item gdb.COMMAND_STATUS
26072 The command is an @samp{info}-related command, that is, related to the
26073 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
26074 and @code{show} are in this category. Type @kbd{help status} at the
26075 @value{GDBN} prompt to see a list of commands in this category.
26077 @findex COMMAND_BREAKPOINTS
26078 @findex gdb.COMMAND_BREAKPOINTS
26079 @item gdb.COMMAND_BREAKPOINTS
26080 The command has to do with breakpoints. For example, @code{break},
26081 @code{clear}, and @code{delete} are in this category. Type @kbd{help
26082 breakpoints} at the @value{GDBN} prompt to see a list of commands in
26085 @findex COMMAND_TRACEPOINTS
26086 @findex gdb.COMMAND_TRACEPOINTS
26087 @item gdb.COMMAND_TRACEPOINTS
26088 The command has to do with tracepoints. For example, @code{trace},
26089 @code{actions}, and @code{tfind} are in this category. Type
26090 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
26091 commands in this category.
26093 @findex COMMAND_USER
26094 @findex gdb.COMMAND_USER
26095 @item gdb.COMMAND_USER
26096 The command is a general purpose command for the user, and typically
26097 does not fit in one of the other categories.
26098 Type @kbd{help user-defined} at the @value{GDBN} prompt to see
26099 a list of commands in this category, as well as the list of gdb macros
26100 (@pxref{Sequences}).
26102 @findex COMMAND_OBSCURE
26103 @findex gdb.COMMAND_OBSCURE
26104 @item gdb.COMMAND_OBSCURE
26105 The command is only used in unusual circumstances, or is not of
26106 general interest to users. For example, @code{checkpoint},
26107 @code{fork}, and @code{stop} are in this category. Type @kbd{help
26108 obscure} at the @value{GDBN} prompt to see a list of commands in this
26111 @findex COMMAND_MAINTENANCE
26112 @findex gdb.COMMAND_MAINTENANCE
26113 @item gdb.COMMAND_MAINTENANCE
26114 The command is only useful to @value{GDBN} maintainers. The
26115 @code{maintenance} and @code{flushregs} commands are in this category.
26116 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
26117 commands in this category.
26120 A new command can use a predefined completion function, either by
26121 specifying it via an argument at initialization, or by returning it
26122 from the @code{complete} method. These predefined completion
26123 constants are all defined in the @code{gdb} module:
26126 @findex COMPLETE_NONE
26127 @findex gdb.COMPLETE_NONE
26128 @item gdb.COMPLETE_NONE
26129 This constant means that no completion should be done.
26131 @findex COMPLETE_FILENAME
26132 @findex gdb.COMPLETE_FILENAME
26133 @item gdb.COMPLETE_FILENAME
26134 This constant means that filename completion should be performed.
26136 @findex COMPLETE_LOCATION
26137 @findex gdb.COMPLETE_LOCATION
26138 @item gdb.COMPLETE_LOCATION
26139 This constant means that location completion should be done.
26140 @xref{Specify Location}.
26142 @findex COMPLETE_COMMAND
26143 @findex gdb.COMPLETE_COMMAND
26144 @item gdb.COMPLETE_COMMAND
26145 This constant means that completion should examine @value{GDBN}
26148 @findex COMPLETE_SYMBOL
26149 @findex gdb.COMPLETE_SYMBOL
26150 @item gdb.COMPLETE_SYMBOL
26151 This constant means that completion should be done using symbol names
26154 @findex COMPLETE_EXPRESSION
26155 @findex gdb.COMPLETE_EXPRESSION
26156 @item gdb.COMPLETE_EXPRESSION
26157 This constant means that completion should be done on expressions.
26158 Often this means completing on symbol names, but some language
26159 parsers also have support for completing on field names.
26162 The following code snippet shows how a trivial CLI command can be
26163 implemented in Python:
26166 class HelloWorld (gdb.Command):
26167 """Greet the whole world."""
26169 def __init__ (self):
26170 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
26172 def invoke (self, arg, from_tty):
26173 print "Hello, World!"
26178 The last line instantiates the class, and is necessary to trigger the
26179 registration of the command with @value{GDBN}. Depending on how the
26180 Python code is read into @value{GDBN}, you may need to import the
26181 @code{gdb} module explicitly.
26183 @node Parameters In Python
26184 @subsubsection Parameters In Python
26186 @cindex parameters in python
26187 @cindex python parameters
26188 @tindex gdb.Parameter
26190 You can implement new @value{GDBN} parameters using Python. A new
26191 parameter is implemented as an instance of the @code{gdb.Parameter}
26194 Parameters are exposed to the user via the @code{set} and
26195 @code{show} commands. @xref{Help}.
26197 There are many parameters that already exist and can be set in
26198 @value{GDBN}. Two examples are: @code{set follow fork} and
26199 @code{set charset}. Setting these parameters influences certain
26200 behavior in @value{GDBN}. Similarly, you can define parameters that
26201 can be used to influence behavior in custom Python scripts and commands.
26203 @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]})
26204 The object initializer for @code{Parameter} registers the new
26205 parameter with @value{GDBN}. This initializer is normally invoked
26206 from the subclass' own @code{__init__} method.
26208 @var{name} is the name of the new parameter. If @var{name} consists
26209 of multiple words, then the initial words are looked for as prefix
26210 parameters. An example of this can be illustrated with the
26211 @code{set print} set of parameters. If @var{name} is
26212 @code{print foo}, then @code{print} will be searched as the prefix
26213 parameter. In this case the parameter can subsequently be accessed in
26214 @value{GDBN} as @code{set print foo}.
26216 If @var{name} consists of multiple words, and no prefix parameter group
26217 can be found, an exception is raised.
26219 @var{command-class} should be one of the @samp{COMMAND_} constants
26220 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
26221 categorize the new parameter in the help system.
26223 @var{parameter-class} should be one of the @samp{PARAM_} constants
26224 defined below. This argument tells @value{GDBN} the type of the new
26225 parameter; this information is used for input validation and
26228 If @var{parameter-class} is @code{PARAM_ENUM}, then
26229 @var{enum-sequence} must be a sequence of strings. These strings
26230 represent the possible values for the parameter.
26232 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
26233 of a fourth argument will cause an exception to be thrown.
26235 The help text for the new parameter is taken from the Python
26236 documentation string for the parameter's class, if there is one. If
26237 there is no documentation string, a default value is used.
26240 @defvar Parameter.set_doc
26241 If this attribute exists, and is a string, then its value is used as
26242 the help text for this parameter's @code{set} command. The value is
26243 examined when @code{Parameter.__init__} is invoked; subsequent changes
26247 @defvar Parameter.show_doc
26248 If this attribute exists, and is a string, then its value is used as
26249 the help text for this parameter's @code{show} command. The value is
26250 examined when @code{Parameter.__init__} is invoked; subsequent changes
26254 @defvar Parameter.value
26255 The @code{value} attribute holds the underlying value of the
26256 parameter. It can be read and assigned to just as any other
26257 attribute. @value{GDBN} does validation when assignments are made.
26260 There are two methods that should be implemented in any
26261 @code{Parameter} class. These are:
26263 @defun Parameter.get_set_string (self)
26264 @value{GDBN} will call this method when a @var{parameter}'s value has
26265 been changed via the @code{set} API (for example, @kbd{set foo off}).
26266 The @code{value} attribute has already been populated with the new
26267 value and may be used in output. This method must return a string.
26270 @defun Parameter.get_show_string (self, svalue)
26271 @value{GDBN} will call this method when a @var{parameter}'s
26272 @code{show} API has been invoked (for example, @kbd{show foo}). The
26273 argument @code{svalue} receives the string representation of the
26274 current value. This method must return a string.
26277 When a new parameter is defined, its type must be specified. The
26278 available types are represented by constants defined in the @code{gdb}
26282 @findex PARAM_BOOLEAN
26283 @findex gdb.PARAM_BOOLEAN
26284 @item gdb.PARAM_BOOLEAN
26285 The value is a plain boolean. The Python boolean values, @code{True}
26286 and @code{False} are the only valid values.
26288 @findex PARAM_AUTO_BOOLEAN
26289 @findex gdb.PARAM_AUTO_BOOLEAN
26290 @item gdb.PARAM_AUTO_BOOLEAN
26291 The value has three possible states: true, false, and @samp{auto}. In
26292 Python, true and false are represented using boolean constants, and
26293 @samp{auto} is represented using @code{None}.
26295 @findex PARAM_UINTEGER
26296 @findex gdb.PARAM_UINTEGER
26297 @item gdb.PARAM_UINTEGER
26298 The value is an unsigned integer. The value of 0 should be
26299 interpreted to mean ``unlimited''.
26301 @findex PARAM_INTEGER
26302 @findex gdb.PARAM_INTEGER
26303 @item gdb.PARAM_INTEGER
26304 The value is a signed integer. The value of 0 should be interpreted
26305 to mean ``unlimited''.
26307 @findex PARAM_STRING
26308 @findex gdb.PARAM_STRING
26309 @item gdb.PARAM_STRING
26310 The value is a string. When the user modifies the string, any escape
26311 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
26312 translated into corresponding characters and encoded into the current
26315 @findex PARAM_STRING_NOESCAPE
26316 @findex gdb.PARAM_STRING_NOESCAPE
26317 @item gdb.PARAM_STRING_NOESCAPE
26318 The value is a string. When the user modifies the string, escapes are
26319 passed through untranslated.
26321 @findex PARAM_OPTIONAL_FILENAME
26322 @findex gdb.PARAM_OPTIONAL_FILENAME
26323 @item gdb.PARAM_OPTIONAL_FILENAME
26324 The value is a either a filename (a string), or @code{None}.
26326 @findex PARAM_FILENAME
26327 @findex gdb.PARAM_FILENAME
26328 @item gdb.PARAM_FILENAME
26329 The value is a filename. This is just like
26330 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
26332 @findex PARAM_ZINTEGER
26333 @findex gdb.PARAM_ZINTEGER
26334 @item gdb.PARAM_ZINTEGER
26335 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
26336 is interpreted as itself.
26339 @findex gdb.PARAM_ENUM
26340 @item gdb.PARAM_ENUM
26341 The value is a string, which must be one of a collection string
26342 constants provided when the parameter is created.
26345 @node Functions In Python
26346 @subsubsection Writing new convenience functions
26348 @cindex writing convenience functions
26349 @cindex convenience functions in python
26350 @cindex python convenience functions
26351 @tindex gdb.Function
26353 You can implement new convenience functions (@pxref{Convenience Vars})
26354 in Python. A convenience function is an instance of a subclass of the
26355 class @code{gdb.Function}.
26357 @defun Function.__init__ (name)
26358 The initializer for @code{Function} registers the new function with
26359 @value{GDBN}. The argument @var{name} is the name of the function,
26360 a string. The function will be visible to the user as a convenience
26361 variable of type @code{internal function}, whose name is the same as
26362 the given @var{name}.
26364 The documentation for the new function is taken from the documentation
26365 string for the new class.
26368 @defun Function.invoke (@var{*args})
26369 When a convenience function is evaluated, its arguments are converted
26370 to instances of @code{gdb.Value}, and then the function's
26371 @code{invoke} method is called. Note that @value{GDBN} does not
26372 predetermine the arity of convenience functions. Instead, all
26373 available arguments are passed to @code{invoke}, following the
26374 standard Python calling convention. In particular, a convenience
26375 function can have default values for parameters without ill effect.
26377 The return value of this method is used as its value in the enclosing
26378 expression. If an ordinary Python value is returned, it is converted
26379 to a @code{gdb.Value} following the usual rules.
26382 The following code snippet shows how a trivial convenience function can
26383 be implemented in Python:
26386 class Greet (gdb.Function):
26387 """Return string to greet someone.
26388 Takes a name as argument."""
26390 def __init__ (self):
26391 super (Greet, self).__init__ ("greet")
26393 def invoke (self, name):
26394 return "Hello, %s!" % name.string ()
26399 The last line instantiates the class, and is necessary to trigger the
26400 registration of the function with @value{GDBN}. Depending on how the
26401 Python code is read into @value{GDBN}, you may need to import the
26402 @code{gdb} module explicitly.
26404 Now you can use the function in an expression:
26407 (gdb) print $greet("Bob")
26411 @node Progspaces In Python
26412 @subsubsection Program Spaces In Python
26414 @cindex progspaces in python
26415 @tindex gdb.Progspace
26417 A program space, or @dfn{progspace}, represents a symbolic view
26418 of an address space.
26419 It consists of all of the objfiles of the program.
26420 @xref{Objfiles In Python}.
26421 @xref{Inferiors and Programs, program spaces}, for more details
26422 about program spaces.
26424 The following progspace-related functions are available in the
26427 @findex gdb.current_progspace
26428 @defun gdb.current_progspace ()
26429 This function returns the program space of the currently selected inferior.
26430 @xref{Inferiors and Programs}.
26433 @findex gdb.progspaces
26434 @defun gdb.progspaces ()
26435 Return a sequence of all the progspaces currently known to @value{GDBN}.
26438 Each progspace is represented by an instance of the @code{gdb.Progspace}
26441 @defvar Progspace.filename
26442 The file name of the progspace as a string.
26445 @defvar Progspace.pretty_printers
26446 The @code{pretty_printers} attribute is a list of functions. It is
26447 used to look up pretty-printers. A @code{Value} is passed to each
26448 function in order; if the function returns @code{None}, then the
26449 search continues. Otherwise, the return value should be an object
26450 which is used to format the value. @xref{Pretty Printing API}, for more
26454 @defvar Progspace.type_printers
26455 The @code{type_printers} attribute is a list of type printer objects.
26456 @xref{Type Printing API}, for more information.
26459 @defvar Progspace.frame_filters
26460 The @code{frame_filters} attribute is a dictionary of frame filter
26461 objects. @xref{Frame Filter API}, for more information.
26464 @node Objfiles In Python
26465 @subsubsection Objfiles In Python
26467 @cindex objfiles in python
26468 @tindex gdb.Objfile
26470 @value{GDBN} loads symbols for an inferior from various
26471 symbol-containing files (@pxref{Files}). These include the primary
26472 executable file, any shared libraries used by the inferior, and any
26473 separate debug info files (@pxref{Separate Debug Files}).
26474 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
26476 The following objfile-related functions are available in the
26479 @findex gdb.current_objfile
26480 @defun gdb.current_objfile ()
26481 When auto-loading a Python script (@pxref{Python Auto-loading}), @value{GDBN}
26482 sets the ``current objfile'' to the corresponding objfile. This
26483 function returns the current objfile. If there is no current objfile,
26484 this function returns @code{None}.
26487 @findex gdb.objfiles
26488 @defun gdb.objfiles ()
26489 Return a sequence of all the objfiles current known to @value{GDBN}.
26490 @xref{Objfiles In Python}.
26493 Each objfile is represented by an instance of the @code{gdb.Objfile}
26496 @defvar Objfile.filename
26497 The file name of the objfile as a string.
26500 @defvar Objfile.pretty_printers
26501 The @code{pretty_printers} attribute is a list of functions. It is
26502 used to look up pretty-printers. A @code{Value} is passed to each
26503 function in order; if the function returns @code{None}, then the
26504 search continues. Otherwise, the return value should be an object
26505 which is used to format the value. @xref{Pretty Printing API}, for more
26509 @defvar Objfile.type_printers
26510 The @code{type_printers} attribute is a list of type printer objects.
26511 @xref{Type Printing API}, for more information.
26514 @defvar Objfile.frame_filters
26515 The @code{frame_filters} attribute is a dictionary of frame filter
26516 objects. @xref{Frame Filter API}, for more information.
26519 A @code{gdb.Objfile} object has the following methods:
26521 @defun Objfile.is_valid ()
26522 Returns @code{True} if the @code{gdb.Objfile} object is valid,
26523 @code{False} if not. A @code{gdb.Objfile} object can become invalid
26524 if the object file it refers to is not loaded in @value{GDBN} any
26525 longer. All other @code{gdb.Objfile} methods will throw an exception
26526 if it is invalid at the time the method is called.
26529 @node Frames In Python
26530 @subsubsection Accessing inferior stack frames from Python.
26532 @cindex frames in python
26533 When the debugged program stops, @value{GDBN} is able to analyze its call
26534 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
26535 represents a frame in the stack. A @code{gdb.Frame} object is only valid
26536 while its corresponding frame exists in the inferior's stack. If you try
26537 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
26538 exception (@pxref{Exception Handling}).
26540 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
26544 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
26548 The following frame-related functions are available in the @code{gdb} module:
26550 @findex gdb.selected_frame
26551 @defun gdb.selected_frame ()
26552 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
26555 @findex gdb.newest_frame
26556 @defun gdb.newest_frame ()
26557 Return the newest frame object for the selected thread.
26560 @defun gdb.frame_stop_reason_string (reason)
26561 Return a string explaining the reason why @value{GDBN} stopped unwinding
26562 frames, as expressed by the given @var{reason} code (an integer, see the
26563 @code{unwind_stop_reason} method further down in this section).
26566 A @code{gdb.Frame} object has the following methods:
26568 @defun Frame.is_valid ()
26569 Returns true if the @code{gdb.Frame} object is valid, false if not.
26570 A frame object can become invalid if the frame it refers to doesn't
26571 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
26572 an exception if it is invalid at the time the method is called.
26575 @defun Frame.name ()
26576 Returns the function name of the frame, or @code{None} if it can't be
26580 @defun Frame.architecture ()
26581 Returns the @code{gdb.Architecture} object corresponding to the frame's
26582 architecture. @xref{Architectures In Python}.
26585 @defun Frame.type ()
26586 Returns the type of the frame. The value can be one of:
26588 @item gdb.NORMAL_FRAME
26589 An ordinary stack frame.
26591 @item gdb.DUMMY_FRAME
26592 A fake stack frame that was created by @value{GDBN} when performing an
26593 inferior function call.
26595 @item gdb.INLINE_FRAME
26596 A frame representing an inlined function. The function was inlined
26597 into a @code{gdb.NORMAL_FRAME} that is older than this one.
26599 @item gdb.TAILCALL_FRAME
26600 A frame representing a tail call. @xref{Tail Call Frames}.
26602 @item gdb.SIGTRAMP_FRAME
26603 A signal trampoline frame. This is the frame created by the OS when
26604 it calls into a signal handler.
26606 @item gdb.ARCH_FRAME
26607 A fake stack frame representing a cross-architecture call.
26609 @item gdb.SENTINEL_FRAME
26610 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
26615 @defun Frame.unwind_stop_reason ()
26616 Return an integer representing the reason why it's not possible to find
26617 more frames toward the outermost frame. Use
26618 @code{gdb.frame_stop_reason_string} to convert the value returned by this
26619 function to a string. The value can be one of:
26622 @item gdb.FRAME_UNWIND_NO_REASON
26623 No particular reason (older frames should be available).
26625 @item gdb.FRAME_UNWIND_NULL_ID
26626 The previous frame's analyzer returns an invalid result. This is no
26627 longer used by @value{GDBN}, and is kept only for backward
26630 @item gdb.FRAME_UNWIND_OUTERMOST
26631 This frame is the outermost.
26633 @item gdb.FRAME_UNWIND_UNAVAILABLE
26634 Cannot unwind further, because that would require knowing the
26635 values of registers or memory that have not been collected.
26637 @item gdb.FRAME_UNWIND_INNER_ID
26638 This frame ID looks like it ought to belong to a NEXT frame,
26639 but we got it for a PREV frame. Normally, this is a sign of
26640 unwinder failure. It could also indicate stack corruption.
26642 @item gdb.FRAME_UNWIND_SAME_ID
26643 This frame has the same ID as the previous one. That means
26644 that unwinding further would almost certainly give us another
26645 frame with exactly the same ID, so break the chain. Normally,
26646 this is a sign of unwinder failure. It could also indicate
26649 @item gdb.FRAME_UNWIND_NO_SAVED_PC
26650 The frame unwinder did not find any saved PC, but we needed
26651 one to unwind further.
26653 @item gdb.FRAME_UNWIND_FIRST_ERROR
26654 Any stop reason greater or equal to this value indicates some kind
26655 of error. This special value facilitates writing code that tests
26656 for errors in unwinding in a way that will work correctly even if
26657 the list of the other values is modified in future @value{GDBN}
26658 versions. Using it, you could write:
26660 reason = gdb.selected_frame().unwind_stop_reason ()
26661 reason_str = gdb.frame_stop_reason_string (reason)
26662 if reason >= gdb.FRAME_UNWIND_FIRST_ERROR:
26663 print "An error occured: %s" % reason_str
26670 Returns the frame's resume address.
26673 @defun Frame.block ()
26674 Return the frame's code block. @xref{Blocks In Python}.
26677 @defun Frame.function ()
26678 Return the symbol for the function corresponding to this frame.
26679 @xref{Symbols In Python}.
26682 @defun Frame.older ()
26683 Return the frame that called this frame.
26686 @defun Frame.newer ()
26687 Return the frame called by this frame.
26690 @defun Frame.find_sal ()
26691 Return the frame's symtab and line object.
26692 @xref{Symbol Tables In Python}.
26695 @defun Frame.read_var (variable @r{[}, block@r{]})
26696 Return the value of @var{variable} in this frame. If the optional
26697 argument @var{block} is provided, search for the variable from that
26698 block; otherwise start at the frame's current block (which is
26699 determined by the frame's current program counter). @var{variable}
26700 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
26701 @code{gdb.Block} object.
26704 @defun Frame.select ()
26705 Set this frame to be the selected frame. @xref{Stack, ,Examining the
26709 @node Blocks In Python
26710 @subsubsection Accessing blocks from Python.
26712 @cindex blocks in python
26715 In @value{GDBN}, symbols are stored in blocks. A block corresponds
26716 roughly to a scope in the source code. Blocks are organized
26717 hierarchically, and are represented individually in Python as a
26718 @code{gdb.Block}. Blocks rely on debugging information being
26721 A frame has a block. Please see @ref{Frames In Python}, for a more
26722 in-depth discussion of frames.
26724 The outermost block is known as the @dfn{global block}. The global
26725 block typically holds public global variables and functions.
26727 The block nested just inside the global block is the @dfn{static
26728 block}. The static block typically holds file-scoped variables and
26731 @value{GDBN} provides a method to get a block's superblock, but there
26732 is currently no way to examine the sub-blocks of a block, or to
26733 iterate over all the blocks in a symbol table (@pxref{Symbol Tables In
26736 Here is a short example that should help explain blocks:
26739 /* This is in the global block. */
26742 /* This is in the static block. */
26743 static int file_scope;
26745 /* 'function' is in the global block, and 'argument' is
26746 in a block nested inside of 'function'. */
26747 int function (int argument)
26749 /* 'local' is in a block inside 'function'. It may or may
26750 not be in the same block as 'argument'. */
26754 /* 'inner' is in a block whose superblock is the one holding
26758 /* If this call is expanded by the compiler, you may see
26759 a nested block here whose function is 'inline_function'
26760 and whose superblock is the one holding 'inner'. */
26761 inline_function ();
26766 A @code{gdb.Block} is iterable. The iterator returns the symbols
26767 (@pxref{Symbols In Python}) local to the block. Python programs
26768 should not assume that a specific block object will always contain a
26769 given symbol, since changes in @value{GDBN} features and
26770 infrastructure may cause symbols move across blocks in a symbol
26773 The following block-related functions are available in the @code{gdb}
26776 @findex gdb.block_for_pc
26777 @defun gdb.block_for_pc (pc)
26778 Return the innermost @code{gdb.Block} containing the given @var{pc}
26779 value. If the block cannot be found for the @var{pc} value specified,
26780 the function will return @code{None}.
26783 A @code{gdb.Block} object has the following methods:
26785 @defun Block.is_valid ()
26786 Returns @code{True} if the @code{gdb.Block} object is valid,
26787 @code{False} if not. A block object can become invalid if the block it
26788 refers to doesn't exist anymore in the inferior. All other
26789 @code{gdb.Block} methods will throw an exception if it is invalid at
26790 the time the method is called. The block's validity is also checked
26791 during iteration over symbols of the block.
26794 A @code{gdb.Block} object has the following attributes:
26796 @defvar Block.start
26797 The start address of the block. This attribute is not writable.
26801 The end address of the block. This attribute is not writable.
26804 @defvar Block.function
26805 The name of the block represented as a @code{gdb.Symbol}. If the
26806 block is not named, then this attribute holds @code{None}. This
26807 attribute is not writable.
26809 For ordinary function blocks, the superblock is the static block.
26810 However, you should note that it is possible for a function block to
26811 have a superblock that is not the static block -- for instance this
26812 happens for an inlined function.
26815 @defvar Block.superblock
26816 The block containing this block. If this parent block does not exist,
26817 this attribute holds @code{None}. This attribute is not writable.
26820 @defvar Block.global_block
26821 The global block associated with this block. This attribute is not
26825 @defvar Block.static_block
26826 The static block associated with this block. This attribute is not
26830 @defvar Block.is_global
26831 @code{True} if the @code{gdb.Block} object is a global block,
26832 @code{False} if not. This attribute is not
26836 @defvar Block.is_static
26837 @code{True} if the @code{gdb.Block} object is a static block,
26838 @code{False} if not. This attribute is not writable.
26841 @node Symbols In Python
26842 @subsubsection Python representation of Symbols.
26844 @cindex symbols in python
26847 @value{GDBN} represents every variable, function and type as an
26848 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
26849 Similarly, Python represents these symbols in @value{GDBN} with the
26850 @code{gdb.Symbol} object.
26852 The following symbol-related functions are available in the @code{gdb}
26855 @findex gdb.lookup_symbol
26856 @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]})
26857 This function searches for a symbol by name. The search scope can be
26858 restricted to the parameters defined in the optional domain and block
26861 @var{name} is the name of the symbol. It must be a string. The
26862 optional @var{block} argument restricts the search to symbols visible
26863 in that @var{block}. The @var{block} argument must be a
26864 @code{gdb.Block} object. If omitted, the block for the current frame
26865 is used. The optional @var{domain} argument restricts
26866 the search to the domain type. The @var{domain} argument must be a
26867 domain constant defined in the @code{gdb} module and described later
26870 The result is a tuple of two elements.
26871 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
26873 If the symbol is found, the second element is @code{True} if the symbol
26874 is a field of a method's object (e.g., @code{this} in C@t{++}),
26875 otherwise it is @code{False}.
26876 If the symbol is not found, the second element is @code{False}.
26879 @findex gdb.lookup_global_symbol
26880 @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]})
26881 This function searches for a global symbol by name.
26882 The search scope can be restricted to by the domain argument.
26884 @var{name} is the name of the symbol. It must be a string.
26885 The optional @var{domain} argument restricts the search to the domain type.
26886 The @var{domain} argument must be a domain constant defined in the @code{gdb}
26887 module and described later in this chapter.
26889 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
26893 A @code{gdb.Symbol} object has the following attributes:
26895 @defvar Symbol.type
26896 The type of the symbol or @code{None} if no type is recorded.
26897 This attribute is represented as a @code{gdb.Type} object.
26898 @xref{Types In Python}. This attribute is not writable.
26901 @defvar Symbol.symtab
26902 The symbol table in which the symbol appears. This attribute is
26903 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
26904 Python}. This attribute is not writable.
26907 @defvar Symbol.line
26908 The line number in the source code at which the symbol was defined.
26909 This is an integer.
26912 @defvar Symbol.name
26913 The name of the symbol as a string. This attribute is not writable.
26916 @defvar Symbol.linkage_name
26917 The name of the symbol, as used by the linker (i.e., may be mangled).
26918 This attribute is not writable.
26921 @defvar Symbol.print_name
26922 The name of the symbol in a form suitable for output. This is either
26923 @code{name} or @code{linkage_name}, depending on whether the user
26924 asked @value{GDBN} to display demangled or mangled names.
26927 @defvar Symbol.addr_class
26928 The address class of the symbol. This classifies how to find the value
26929 of a symbol. Each address class is a constant defined in the
26930 @code{gdb} module and described later in this chapter.
26933 @defvar Symbol.needs_frame
26934 This is @code{True} if evaluating this symbol's value requires a frame
26935 (@pxref{Frames In Python}) and @code{False} otherwise. Typically,
26936 local variables will require a frame, but other symbols will not.
26939 @defvar Symbol.is_argument
26940 @code{True} if the symbol is an argument of a function.
26943 @defvar Symbol.is_constant
26944 @code{True} if the symbol is a constant.
26947 @defvar Symbol.is_function
26948 @code{True} if the symbol is a function or a method.
26951 @defvar Symbol.is_variable
26952 @code{True} if the symbol is a variable.
26955 A @code{gdb.Symbol} object has the following methods:
26957 @defun Symbol.is_valid ()
26958 Returns @code{True} if the @code{gdb.Symbol} object is valid,
26959 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
26960 the symbol it refers to does not exist in @value{GDBN} any longer.
26961 All other @code{gdb.Symbol} methods will throw an exception if it is
26962 invalid at the time the method is called.
26965 @defun Symbol.value (@r{[}frame@r{]})
26966 Compute the value of the symbol, as a @code{gdb.Value}. For
26967 functions, this computes the address of the function, cast to the
26968 appropriate type. If the symbol requires a frame in order to compute
26969 its value, then @var{frame} must be given. If @var{frame} is not
26970 given, or if @var{frame} is invalid, then this method will throw an
26974 The available domain categories in @code{gdb.Symbol} are represented
26975 as constants in the @code{gdb} module:
26978 @findex SYMBOL_UNDEF_DOMAIN
26979 @findex gdb.SYMBOL_UNDEF_DOMAIN
26980 @item gdb.SYMBOL_UNDEF_DOMAIN
26981 This is used when a domain has not been discovered or none of the
26982 following domains apply. This usually indicates an error either
26983 in the symbol information or in @value{GDBN}'s handling of symbols.
26984 @findex SYMBOL_VAR_DOMAIN
26985 @findex gdb.SYMBOL_VAR_DOMAIN
26986 @item gdb.SYMBOL_VAR_DOMAIN
26987 This domain contains variables, function names, typedef names and enum
26989 @findex SYMBOL_STRUCT_DOMAIN
26990 @findex gdb.SYMBOL_STRUCT_DOMAIN
26991 @item gdb.SYMBOL_STRUCT_DOMAIN
26992 This domain holds struct, union and enum type names.
26993 @findex SYMBOL_LABEL_DOMAIN
26994 @findex gdb.SYMBOL_LABEL_DOMAIN
26995 @item gdb.SYMBOL_LABEL_DOMAIN
26996 This domain contains names of labels (for gotos).
26997 @findex SYMBOL_VARIABLES_DOMAIN
26998 @findex gdb.SYMBOL_VARIABLES_DOMAIN
26999 @item gdb.SYMBOL_VARIABLES_DOMAIN
27000 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
27001 contains everything minus functions and types.
27002 @findex SYMBOL_FUNCTIONS_DOMAIN
27003 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
27004 @item gdb.SYMBOL_FUNCTION_DOMAIN
27005 This domain contains all functions.
27006 @findex SYMBOL_TYPES_DOMAIN
27007 @findex gdb.SYMBOL_TYPES_DOMAIN
27008 @item gdb.SYMBOL_TYPES_DOMAIN
27009 This domain contains all types.
27012 The available address class categories in @code{gdb.Symbol} are represented
27013 as constants in the @code{gdb} module:
27016 @findex SYMBOL_LOC_UNDEF
27017 @findex gdb.SYMBOL_LOC_UNDEF
27018 @item gdb.SYMBOL_LOC_UNDEF
27019 If this is returned by address class, it indicates an error either in
27020 the symbol information or in @value{GDBN}'s handling of symbols.
27021 @findex SYMBOL_LOC_CONST
27022 @findex gdb.SYMBOL_LOC_CONST
27023 @item gdb.SYMBOL_LOC_CONST
27024 Value is constant int.
27025 @findex SYMBOL_LOC_STATIC
27026 @findex gdb.SYMBOL_LOC_STATIC
27027 @item gdb.SYMBOL_LOC_STATIC
27028 Value is at a fixed address.
27029 @findex SYMBOL_LOC_REGISTER
27030 @findex gdb.SYMBOL_LOC_REGISTER
27031 @item gdb.SYMBOL_LOC_REGISTER
27032 Value is in a register.
27033 @findex SYMBOL_LOC_ARG
27034 @findex gdb.SYMBOL_LOC_ARG
27035 @item gdb.SYMBOL_LOC_ARG
27036 Value is an argument. This value is at the offset stored within the
27037 symbol inside the frame's argument list.
27038 @findex SYMBOL_LOC_REF_ARG
27039 @findex gdb.SYMBOL_LOC_REF_ARG
27040 @item gdb.SYMBOL_LOC_REF_ARG
27041 Value address is stored in the frame's argument list. Just like
27042 @code{LOC_ARG} except that the value's address is stored at the
27043 offset, not the value itself.
27044 @findex SYMBOL_LOC_REGPARM_ADDR
27045 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
27046 @item gdb.SYMBOL_LOC_REGPARM_ADDR
27047 Value is a specified register. Just like @code{LOC_REGISTER} except
27048 the register holds the address of the argument instead of the argument
27050 @findex SYMBOL_LOC_LOCAL
27051 @findex gdb.SYMBOL_LOC_LOCAL
27052 @item gdb.SYMBOL_LOC_LOCAL
27053 Value is a local variable.
27054 @findex SYMBOL_LOC_TYPEDEF
27055 @findex gdb.SYMBOL_LOC_TYPEDEF
27056 @item gdb.SYMBOL_LOC_TYPEDEF
27057 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
27059 @findex SYMBOL_LOC_BLOCK
27060 @findex gdb.SYMBOL_LOC_BLOCK
27061 @item gdb.SYMBOL_LOC_BLOCK
27063 @findex SYMBOL_LOC_CONST_BYTES
27064 @findex gdb.SYMBOL_LOC_CONST_BYTES
27065 @item gdb.SYMBOL_LOC_CONST_BYTES
27066 Value is a byte-sequence.
27067 @findex SYMBOL_LOC_UNRESOLVED
27068 @findex gdb.SYMBOL_LOC_UNRESOLVED
27069 @item gdb.SYMBOL_LOC_UNRESOLVED
27070 Value is at a fixed address, but the address of the variable has to be
27071 determined from the minimal symbol table whenever the variable is
27073 @findex SYMBOL_LOC_OPTIMIZED_OUT
27074 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
27075 @item gdb.SYMBOL_LOC_OPTIMIZED_OUT
27076 The value does not actually exist in the program.
27077 @findex SYMBOL_LOC_COMPUTED
27078 @findex gdb.SYMBOL_LOC_COMPUTED
27079 @item gdb.SYMBOL_LOC_COMPUTED
27080 The value's address is a computed location.
27083 @node Symbol Tables In Python
27084 @subsubsection Symbol table representation in Python.
27086 @cindex symbol tables in python
27088 @tindex gdb.Symtab_and_line
27090 Access to symbol table data maintained by @value{GDBN} on the inferior
27091 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
27092 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
27093 from the @code{find_sal} method in @code{gdb.Frame} object.
27094 @xref{Frames In Python}.
27096 For more information on @value{GDBN}'s symbol table management, see
27097 @ref{Symbols, ,Examining the Symbol Table}, for more information.
27099 A @code{gdb.Symtab_and_line} object has the following attributes:
27101 @defvar Symtab_and_line.symtab
27102 The symbol table object (@code{gdb.Symtab}) for this frame.
27103 This attribute is not writable.
27106 @defvar Symtab_and_line.pc
27107 Indicates the start of the address range occupied by code for the
27108 current source line. This attribute is not writable.
27111 @defvar Symtab_and_line.last
27112 Indicates the end of the address range occupied by code for the current
27113 source line. This attribute is not writable.
27116 @defvar Symtab_and_line.line
27117 Indicates the current line number for this object. This
27118 attribute is not writable.
27121 A @code{gdb.Symtab_and_line} object has the following methods:
27123 @defun Symtab_and_line.is_valid ()
27124 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
27125 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
27126 invalid if the Symbol table and line object it refers to does not
27127 exist in @value{GDBN} any longer. All other
27128 @code{gdb.Symtab_and_line} methods will throw an exception if it is
27129 invalid at the time the method is called.
27132 A @code{gdb.Symtab} object has the following attributes:
27134 @defvar Symtab.filename
27135 The symbol table's source filename. This attribute is not writable.
27138 @defvar Symtab.objfile
27139 The symbol table's backing object file. @xref{Objfiles In Python}.
27140 This attribute is not writable.
27143 A @code{gdb.Symtab} object has the following methods:
27145 @defun Symtab.is_valid ()
27146 Returns @code{True} if the @code{gdb.Symtab} object is valid,
27147 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
27148 the symbol table it refers to does not exist in @value{GDBN} any
27149 longer. All other @code{gdb.Symtab} methods will throw an exception
27150 if it is invalid at the time the method is called.
27153 @defun Symtab.fullname ()
27154 Return the symbol table's source absolute file name.
27157 @defun Symtab.global_block ()
27158 Return the global block of the underlying symbol table.
27159 @xref{Blocks In Python}.
27162 @defun Symtab.static_block ()
27163 Return the static block of the underlying symbol table.
27164 @xref{Blocks In Python}.
27167 @defun Symtab.linetable ()
27168 Return the line table associated with the symbol table.
27169 @xref{Line Tables In Python}.
27172 @node Line Tables In Python
27173 @subsubsection Manipulating line tables using Python
27175 @cindex line tables in python
27176 @tindex gdb.LineTable
27178 Python code can request and inspect line table information from a
27179 symbol table that is loaded in @value{GDBN}. A line table is a
27180 mapping of source lines to their executable locations in memory. To
27181 acquire the line table information for a particular symbol table, use
27182 the @code{linetable} function (@pxref{Symbol Tables In Python}).
27184 A @code{gdb.LineTable} is iterable. The iterator returns
27185 @code{LineTableEntry} objects that correspond to the source line and
27186 address for each line table entry. @code{LineTableEntry} objects have
27187 the following attributes:
27189 @defvar LineTableEntry.line
27190 The source line number for this line table entry. This number
27191 corresponds to the actual line of source. This attribute is not
27195 @defvar LineTableEntry.pc
27196 The address that is associated with the line table entry where the
27197 executable code for that source line resides in memory. This
27198 attribute is not writable.
27201 As there can be multiple addresses for a single source line, you may
27202 receive multiple @code{LineTableEntry} objects with matching
27203 @code{line} attributes, but with different @code{pc} attributes. The
27204 iterator is sorted in ascending @code{pc} order. Here is a small
27205 example illustrating iterating over a line table.
27208 symtab = gdb.selected_frame().find_sal().symtab
27209 linetable = symtab.linetable()
27210 for line in linetable:
27211 print "Line: "+str(line.line)+" Address: "+hex(line.pc)
27214 This will have the following output:
27217 Line: 33 Address: 0x4005c8L
27218 Line: 37 Address: 0x4005caL
27219 Line: 39 Address: 0x4005d2L
27220 Line: 40 Address: 0x4005f8L
27221 Line: 42 Address: 0x4005ffL
27222 Line: 44 Address: 0x400608L
27223 Line: 42 Address: 0x40060cL
27224 Line: 45 Address: 0x400615L
27227 In addition to being able to iterate over a @code{LineTable}, it also
27228 has the following direct access methods:
27230 @defun LineTable.line (line)
27231 Return a Python @code{Tuple} of @code{LineTableEntry} objects for any
27232 entries in the line table for the given @var{line}. @var{line} refers
27233 to the source code line. If there are no entries for that source code
27234 @var{line}, the Python @code{None} is returned.
27237 @defun LineTable.has_line (line)
27238 Return a Python @code{Boolean} indicating whether there is an entry in
27239 the line table for this source line. Return @code{True} if an entry
27240 is found, or @code{False} if not.
27243 @defun LineTable.source_lines ()
27244 Return a Python @code{List} of the source line numbers in the symbol
27245 table. Only lines with executable code locations are returned. The
27246 contents of the @code{List} will just be the source line entries
27247 represented as Python @code{Long} values.
27250 @node Breakpoints In Python
27251 @subsubsection Manipulating breakpoints using Python
27253 @cindex breakpoints in python
27254 @tindex gdb.Breakpoint
27256 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
27259 @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal @r{[},temporary@r{]]]]})
27260 Create a new breakpoint. @var{spec} is a string naming the location
27261 of the breakpoint, or an expression that defines a watchpoint. The
27262 contents can be any location recognized by the @code{break} command,
27263 or in the case of a watchpoint, by the @code{watch} command. The
27264 optional @var{type} denotes the breakpoint to create from the types
27265 defined later in this chapter. This argument can be either:
27266 @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type}
27267 defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal}
27268 argument allows the breakpoint to become invisible to the user. The
27269 breakpoint will neither be reported when created, nor will it be
27270 listed in the output from @code{info breakpoints} (but will be listed
27271 with the @code{maint info breakpoints} command). The optional
27272 @var{temporary} argument makes the breakpoint a temporary breakpoint.
27273 Temporary breakpoints are deleted after they have been hit. Any
27274 further access to the Python breakpoint after it has been hit will
27275 result in a runtime error (as that breakpoint has now been
27276 automatically deleted). The optional @var{wp_class} argument defines
27277 the class of watchpoint to create, if @var{type} is
27278 @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it
27279 is assumed to be a @code{gdb.WP_WRITE} class.
27282 @defun Breakpoint.stop (self)
27283 The @code{gdb.Breakpoint} class can be sub-classed and, in
27284 particular, you may choose to implement the @code{stop} method.
27285 If this method is defined in a sub-class of @code{gdb.Breakpoint},
27286 it will be called when the inferior reaches any location of a
27287 breakpoint which instantiates that sub-class. If the method returns
27288 @code{True}, the inferior will be stopped at the location of the
27289 breakpoint, otherwise the inferior will continue.
27291 If there are multiple breakpoints at the same location with a
27292 @code{stop} method, each one will be called regardless of the
27293 return status of the previous. This ensures that all @code{stop}
27294 methods have a chance to execute at that location. In this scenario
27295 if one of the methods returns @code{True} but the others return
27296 @code{False}, the inferior will still be stopped.
27298 You should not alter the execution state of the inferior (i.e.@:, step,
27299 next, etc.), alter the current frame context (i.e.@:, change the current
27300 active frame), or alter, add or delete any breakpoint. As a general
27301 rule, you should not alter any data within @value{GDBN} or the inferior
27304 Example @code{stop} implementation:
27307 class MyBreakpoint (gdb.Breakpoint):
27309 inf_val = gdb.parse_and_eval("foo")
27316 The available watchpoint types represented by constants are defined in the
27321 @findex gdb.WP_READ
27323 Read only watchpoint.
27326 @findex gdb.WP_WRITE
27328 Write only watchpoint.
27331 @findex gdb.WP_ACCESS
27332 @item gdb.WP_ACCESS
27333 Read/Write watchpoint.
27336 @defun Breakpoint.is_valid ()
27337 Return @code{True} if this @code{Breakpoint} object is valid,
27338 @code{False} otherwise. A @code{Breakpoint} object can become invalid
27339 if the user deletes the breakpoint. In this case, the object still
27340 exists, but the underlying breakpoint does not. In the cases of
27341 watchpoint scope, the watchpoint remains valid even if execution of the
27342 inferior leaves the scope of that watchpoint.
27345 @defun Breakpoint.delete
27346 Permanently deletes the @value{GDBN} breakpoint. This also
27347 invalidates the Python @code{Breakpoint} object. Any further access
27348 to this object's attributes or methods will raise an error.
27351 @defvar Breakpoint.enabled
27352 This attribute is @code{True} if the breakpoint is enabled, and
27353 @code{False} otherwise. This attribute is writable.
27356 @defvar Breakpoint.silent
27357 This attribute is @code{True} if the breakpoint is silent, and
27358 @code{False} otherwise. This attribute is writable.
27360 Note that a breakpoint can also be silent if it has commands and the
27361 first command is @code{silent}. This is not reported by the
27362 @code{silent} attribute.
27365 @defvar Breakpoint.thread
27366 If the breakpoint is thread-specific, this attribute holds the thread
27367 id. If the breakpoint is not thread-specific, this attribute is
27368 @code{None}. This attribute is writable.
27371 @defvar Breakpoint.task
27372 If the breakpoint is Ada task-specific, this attribute holds the Ada task
27373 id. If the breakpoint is not task-specific (or the underlying
27374 language is not Ada), this attribute is @code{None}. This attribute
27378 @defvar Breakpoint.ignore_count
27379 This attribute holds the ignore count for the breakpoint, an integer.
27380 This attribute is writable.
27383 @defvar Breakpoint.number
27384 This attribute holds the breakpoint's number --- the identifier used by
27385 the user to manipulate the breakpoint. This attribute is not writable.
27388 @defvar Breakpoint.type
27389 This attribute holds the breakpoint's type --- the identifier used to
27390 determine the actual breakpoint type or use-case. This attribute is not
27394 @defvar Breakpoint.visible
27395 This attribute tells whether the breakpoint is visible to the user
27396 when set, or when the @samp{info breakpoints} command is run. This
27397 attribute is not writable.
27400 @defvar Breakpoint.temporary
27401 This attribute indicates whether the breakpoint was created as a
27402 temporary breakpoint. Temporary breakpoints are automatically deleted
27403 after that breakpoint has been hit. Access to this attribute, and all
27404 other attributes and functions other than the @code{is_valid}
27405 function, will result in an error after the breakpoint has been hit
27406 (as it has been automatically deleted). This attribute is not
27410 The available types are represented by constants defined in the @code{gdb}
27414 @findex BP_BREAKPOINT
27415 @findex gdb.BP_BREAKPOINT
27416 @item gdb.BP_BREAKPOINT
27417 Normal code breakpoint.
27419 @findex BP_WATCHPOINT
27420 @findex gdb.BP_WATCHPOINT
27421 @item gdb.BP_WATCHPOINT
27422 Watchpoint breakpoint.
27424 @findex BP_HARDWARE_WATCHPOINT
27425 @findex gdb.BP_HARDWARE_WATCHPOINT
27426 @item gdb.BP_HARDWARE_WATCHPOINT
27427 Hardware assisted watchpoint.
27429 @findex BP_READ_WATCHPOINT
27430 @findex gdb.BP_READ_WATCHPOINT
27431 @item gdb.BP_READ_WATCHPOINT
27432 Hardware assisted read watchpoint.
27434 @findex BP_ACCESS_WATCHPOINT
27435 @findex gdb.BP_ACCESS_WATCHPOINT
27436 @item gdb.BP_ACCESS_WATCHPOINT
27437 Hardware assisted access watchpoint.
27440 @defvar Breakpoint.hit_count
27441 This attribute holds the hit count for the breakpoint, an integer.
27442 This attribute is writable, but currently it can only be set to zero.
27445 @defvar Breakpoint.location
27446 This attribute holds the location of the breakpoint, as specified by
27447 the user. It is a string. If the breakpoint does not have a location
27448 (that is, it is a watchpoint) the attribute's value is @code{None}. This
27449 attribute is not writable.
27452 @defvar Breakpoint.expression
27453 This attribute holds a breakpoint expression, as specified by
27454 the user. It is a string. If the breakpoint does not have an
27455 expression (the breakpoint is not a watchpoint) the attribute's value
27456 is @code{None}. This attribute is not writable.
27459 @defvar Breakpoint.condition
27460 This attribute holds the condition of the breakpoint, as specified by
27461 the user. It is a string. If there is no condition, this attribute's
27462 value is @code{None}. This attribute is writable.
27465 @defvar Breakpoint.commands
27466 This attribute holds the commands attached to the breakpoint. If
27467 there are commands, this attribute's value is a string holding all the
27468 commands, separated by newlines. If there are no commands, this
27469 attribute is @code{None}. This attribute is not writable.
27472 @node Finish Breakpoints in Python
27473 @subsubsection Finish Breakpoints
27475 @cindex python finish breakpoints
27476 @tindex gdb.FinishBreakpoint
27478 A finish breakpoint is a temporary breakpoint set at the return address of
27479 a frame, based on the @code{finish} command. @code{gdb.FinishBreakpoint}
27480 extends @code{gdb.Breakpoint}. The underlying breakpoint will be disabled
27481 and deleted when the execution will run out of the breakpoint scope (i.e.@:
27482 @code{Breakpoint.stop} or @code{FinishBreakpoint.out_of_scope} triggered).
27483 Finish breakpoints are thread specific and must be create with the right
27486 @defun FinishBreakpoint.__init__ (@r{[}frame@r{]} @r{[}, internal@r{]})
27487 Create a finish breakpoint at the return address of the @code{gdb.Frame}
27488 object @var{frame}. If @var{frame} is not provided, this defaults to the
27489 newest frame. The optional @var{internal} argument allows the breakpoint to
27490 become invisible to the user. @xref{Breakpoints In Python}, for further
27491 details about this argument.
27494 @defun FinishBreakpoint.out_of_scope (self)
27495 In some circumstances (e.g.@: @code{longjmp}, C@t{++} exceptions, @value{GDBN}
27496 @code{return} command, @dots{}), a function may not properly terminate, and
27497 thus never hit the finish breakpoint. When @value{GDBN} notices such a
27498 situation, the @code{out_of_scope} callback will be triggered.
27500 You may want to sub-class @code{gdb.FinishBreakpoint} and override this
27504 class MyFinishBreakpoint (gdb.FinishBreakpoint)
27506 print "normal finish"
27509 def out_of_scope ():
27510 print "abnormal finish"
27514 @defvar FinishBreakpoint.return_value
27515 When @value{GDBN} is stopped at a finish breakpoint and the frame
27516 used to build the @code{gdb.FinishBreakpoint} object had debug symbols, this
27517 attribute will contain a @code{gdb.Value} object corresponding to the return
27518 value of the function. The value will be @code{None} if the function return
27519 type is @code{void} or if the return value was not computable. This attribute
27523 @node Lazy Strings In Python
27524 @subsubsection Python representation of lazy strings.
27526 @cindex lazy strings in python
27527 @tindex gdb.LazyString
27529 A @dfn{lazy string} is a string whose contents is not retrieved or
27530 encoded until it is needed.
27532 A @code{gdb.LazyString} is represented in @value{GDBN} as an
27533 @code{address} that points to a region of memory, an @code{encoding}
27534 that will be used to encode that region of memory, and a @code{length}
27535 to delimit the region of memory that represents the string. The
27536 difference between a @code{gdb.LazyString} and a string wrapped within
27537 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
27538 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
27539 retrieved and encoded during printing, while a @code{gdb.Value}
27540 wrapping a string is immediately retrieved and encoded on creation.
27542 A @code{gdb.LazyString} object has the following functions:
27544 @defun LazyString.value ()
27545 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
27546 will point to the string in memory, but will lose all the delayed
27547 retrieval, encoding and handling that @value{GDBN} applies to a
27548 @code{gdb.LazyString}.
27551 @defvar LazyString.address
27552 This attribute holds the address of the string. This attribute is not
27556 @defvar LazyString.length
27557 This attribute holds the length of the string in characters. If the
27558 length is -1, then the string will be fetched and encoded up to the
27559 first null of appropriate width. This attribute is not writable.
27562 @defvar LazyString.encoding
27563 This attribute holds the encoding that will be applied to the string
27564 when the string is printed by @value{GDBN}. If the encoding is not
27565 set, or contains an empty string, then @value{GDBN} will select the
27566 most appropriate encoding when the string is printed. This attribute
27570 @defvar LazyString.type
27571 This attribute holds the type that is represented by the lazy string's
27572 type. For a lazy string this will always be a pointer type. To
27573 resolve this to the lazy string's character type, use the type's
27574 @code{target} method. @xref{Types In Python}. This attribute is not
27578 @node Architectures In Python
27579 @subsubsection Python representation of architectures
27580 @cindex Python architectures
27582 @value{GDBN} uses architecture specific parameters and artifacts in a
27583 number of its various computations. An architecture is represented
27584 by an instance of the @code{gdb.Architecture} class.
27586 A @code{gdb.Architecture} class has the following methods:
27588 @defun Architecture.name ()
27589 Return the name (string value) of the architecture.
27592 @defun Architecture.disassemble (@var{start_pc} @r{[}, @var{end_pc} @r{[}, @var{count}@r{]]})
27593 Return a list of disassembled instructions starting from the memory
27594 address @var{start_pc}. The optional arguments @var{end_pc} and
27595 @var{count} determine the number of instructions in the returned list.
27596 If both the optional arguments @var{end_pc} and @var{count} are
27597 specified, then a list of at most @var{count} disassembled instructions
27598 whose start address falls in the closed memory address interval from
27599 @var{start_pc} to @var{end_pc} are returned. If @var{end_pc} is not
27600 specified, but @var{count} is specified, then @var{count} number of
27601 instructions starting from the address @var{start_pc} are returned. If
27602 @var{count} is not specified but @var{end_pc} is specified, then all
27603 instructions whose start address falls in the closed memory address
27604 interval from @var{start_pc} to @var{end_pc} are returned. If neither
27605 @var{end_pc} nor @var{count} are specified, then a single instruction at
27606 @var{start_pc} is returned. For all of these cases, each element of the
27607 returned list is a Python @code{dict} with the following string keys:
27612 The value corresponding to this key is a Python long integer capturing
27613 the memory address of the instruction.
27616 The value corresponding to this key is a string value which represents
27617 the instruction with assembly language mnemonics. The assembly
27618 language flavor used is the same as that specified by the current CLI
27619 variable @code{disassembly-flavor}. @xref{Machine Code}.
27622 The value corresponding to this key is the length (integer value) of the
27623 instruction in bytes.
27628 @node Python Auto-loading
27629 @subsection Python Auto-loading
27630 @cindex Python auto-loading
27632 When a new object file is read (for example, due to the @code{file}
27633 command, or because the inferior has loaded a shared library),
27634 @value{GDBN} will look for Python support scripts in several ways:
27635 @file{@var{objfile}-gdb.py} and @code{.debug_gdb_scripts} section.
27636 @xref{Auto-loading extensions}.
27638 The auto-loading feature is useful for supplying application-specific
27639 debugging commands and scripts.
27641 Auto-loading can be enabled or disabled,
27642 and the list of auto-loaded scripts can be printed.
27645 @anchor{set auto-load python-scripts}
27646 @kindex set auto-load python-scripts
27647 @item set auto-load python-scripts [on|off]
27648 Enable or disable the auto-loading of Python scripts.
27650 @anchor{show auto-load python-scripts}
27651 @kindex show auto-load python-scripts
27652 @item show auto-load python-scripts
27653 Show whether auto-loading of Python scripts is enabled or disabled.
27655 @anchor{info auto-load python-scripts}
27656 @kindex info auto-load python-scripts
27657 @cindex print list of auto-loaded Python scripts
27658 @item info auto-load python-scripts [@var{regexp}]
27659 Print the list of all Python scripts that @value{GDBN} auto-loaded.
27661 Also printed is the list of Python scripts that were mentioned in
27662 the @code{.debug_gdb_scripts} section and were not found
27663 (@pxref{dotdebug_gdb_scripts section}).
27664 This is useful because their names are not printed when @value{GDBN}
27665 tries to load them and fails. There may be many of them, and printing
27666 an error message for each one is problematic.
27668 If @var{regexp} is supplied only Python scripts with matching names are printed.
27673 (gdb) info auto-load python-scripts
27675 Yes py-section-script.py
27676 full name: /tmp/py-section-script.py
27677 No my-foo-pretty-printers.py
27681 When reading an auto-loaded file, @value{GDBN} sets the
27682 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
27683 function (@pxref{Objfiles In Python}). This can be useful for
27684 registering objfile-specific pretty-printers and frame-filters.
27686 @node Python modules
27687 @subsection Python modules
27688 @cindex python modules
27690 @value{GDBN} comes with several modules to assist writing Python code.
27693 * gdb.printing:: Building and registering pretty-printers.
27694 * gdb.types:: Utilities for working with types.
27695 * gdb.prompt:: Utilities for prompt value substitution.
27699 @subsubsection gdb.printing
27700 @cindex gdb.printing
27702 This module provides a collection of utilities for working with
27706 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
27707 This class specifies the API that makes @samp{info pretty-printer},
27708 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
27709 Pretty-printers should generally inherit from this class.
27711 @item SubPrettyPrinter (@var{name})
27712 For printers that handle multiple types, this class specifies the
27713 corresponding API for the subprinters.
27715 @item RegexpCollectionPrettyPrinter (@var{name})
27716 Utility class for handling multiple printers, all recognized via
27717 regular expressions.
27718 @xref{Writing a Pretty-Printer}, for an example.
27720 @item FlagEnumerationPrinter (@var{name})
27721 A pretty-printer which handles printing of @code{enum} values. Unlike
27722 @value{GDBN}'s built-in @code{enum} printing, this printer attempts to
27723 work properly when there is some overlap between the enumeration
27724 constants. @var{name} is the name of the printer and also the name of
27725 the @code{enum} type to look up.
27727 @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False)
27728 Register @var{printer} with the pretty-printer list of @var{obj}.
27729 If @var{replace} is @code{True} then any existing copy of the printer
27730 is replaced. Otherwise a @code{RuntimeError} exception is raised
27731 if a printer with the same name already exists.
27735 @subsubsection gdb.types
27738 This module provides a collection of utilities for working with
27739 @code{gdb.Type} objects.
27742 @item get_basic_type (@var{type})
27743 Return @var{type} with const and volatile qualifiers stripped,
27744 and with typedefs and C@t{++} references converted to the underlying type.
27749 typedef const int const_int;
27751 const_int& foo_ref (foo);
27752 int main () @{ return 0; @}
27759 (gdb) python import gdb.types
27760 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
27761 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
27765 @item has_field (@var{type}, @var{field})
27766 Return @code{True} if @var{type}, assumed to be a type with fields
27767 (e.g., a structure or union), has field @var{field}.
27769 @item make_enum_dict (@var{enum_type})
27770 Return a Python @code{dictionary} type produced from @var{enum_type}.
27772 @item deep_items (@var{type})
27773 Returns a Python iterator similar to the standard
27774 @code{gdb.Type.iteritems} method, except that the iterator returned
27775 by @code{deep_items} will recursively traverse anonymous struct or
27776 union fields. For example:
27790 Then in @value{GDBN}:
27792 (@value{GDBP}) python import gdb.types
27793 (@value{GDBP}) python struct_a = gdb.lookup_type("struct A")
27794 (@value{GDBP}) python print struct_a.keys ()
27796 (@value{GDBP}) python print [k for k,v in gdb.types.deep_items(struct_a)]
27797 @{['a', 'b0', 'b1']@}
27800 @item get_type_recognizers ()
27801 Return a list of the enabled type recognizers for the current context.
27802 This is called by @value{GDBN} during the type-printing process
27803 (@pxref{Type Printing API}).
27805 @item apply_type_recognizers (recognizers, type_obj)
27806 Apply the type recognizers, @var{recognizers}, to the type object
27807 @var{type_obj}. If any recognizer returns a string, return that
27808 string. Otherwise, return @code{None}. This is called by
27809 @value{GDBN} during the type-printing process (@pxref{Type Printing
27812 @item register_type_printer (locus, printer)
27813 This is a convenience function to register a type printer.
27814 @var{printer} is the type printer to register. It must implement the
27815 type printer protocol. @var{locus} is either a @code{gdb.Objfile}, in
27816 which case the printer is registered with that objfile; a
27817 @code{gdb.Progspace}, in which case the printer is registered with
27818 that progspace; or @code{None}, in which case the printer is
27819 registered globally.
27822 This is a base class that implements the type printer protocol. Type
27823 printers are encouraged, but not required, to derive from this class.
27824 It defines a constructor:
27826 @defmethod TypePrinter __init__ (self, name)
27827 Initialize the type printer with the given name. The new printer
27828 starts in the enabled state.
27834 @subsubsection gdb.prompt
27837 This module provides a method for prompt value-substitution.
27840 @item substitute_prompt (@var{string})
27841 Return @var{string} with escape sequences substituted by values. Some
27842 escape sequences take arguments. You can specify arguments inside
27843 ``@{@}'' immediately following the escape sequence.
27845 The escape sequences you can pass to this function are:
27849 Substitute a backslash.
27851 Substitute an ESC character.
27853 Substitute the selected frame; an argument names a frame parameter.
27855 Substitute a newline.
27857 Substitute a parameter's value; the argument names the parameter.
27859 Substitute a carriage return.
27861 Substitute the selected thread; an argument names a thread parameter.
27863 Substitute the version of GDB.
27865 Substitute the current working directory.
27867 Begin a sequence of non-printing characters. These sequences are
27868 typically used with the ESC character, and are not counted in the string
27869 length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a
27870 blue-colored ``(gdb)'' prompt where the length is five.
27872 End a sequence of non-printing characters.
27878 substitute_prompt (``frame: \f,
27879 print arguments: \p@{print frame-arguments@}'')
27882 @exdent will return the string:
27885 "frame: main, print arguments: scalars"
27889 @node Auto-loading extensions
27890 @section Auto-loading extensions
27891 @cindex auto-loading extensions
27893 @value{GDBN} provides two mechanisms for automatically loading extensions
27894 when a new object file is read (for example, due to the @code{file}
27895 command, or because the inferior has loaded a shared library):
27896 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
27897 section of modern file formats like ELF.
27900 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
27901 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
27902 * Which flavor to choose?::
27905 The auto-loading feature is useful for supplying application-specific
27906 debugging commands and features.
27908 Auto-loading can be enabled or disabled,
27909 and the list of auto-loaded scripts can be printed.
27910 See the @samp{auto-loading} section of each extension language
27911 for more information.
27912 For @value{GDBN} command files see @ref{Auto-loading sequences}.
27913 For Python files see @ref{Python Auto-loading}.
27915 Note that loading of this script file also requires accordingly configured
27916 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27918 @node objfile-gdbdotext file
27919 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
27920 @cindex @file{@var{objfile}-gdb.gdb}
27921 @cindex @file{@var{objfile}-gdb.py}
27922 @cindex @file{@var{objfile}-gdb.scm}
27924 When a new object file is read, @value{GDBN} looks for a file named
27925 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
27926 where @var{objfile} is the object file's name and
27927 where @var{ext} is the file extension for the extension language:
27930 @item @file{@var{objfile}-gdb.gdb}
27931 GDB's own command language
27932 @item @file{@var{objfile}-gdb.py}
27936 @var{script-name} is formed by ensuring that the file name of @var{objfile}
27937 is absolute, following all symlinks, and resolving @code{.} and @code{..}
27938 components, and appending the @file{-gdb.@var{ext}} suffix.
27939 If this file exists and is readable, @value{GDBN} will evaluate it as a
27940 script in the specified extension language.
27942 If this file does not exist, then @value{GDBN} will look for
27943 @var{script-name} file in all of the directories as specified below.
27945 Note that loading of these files requires an accordingly configured
27946 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27948 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
27949 scripts normally according to its @file{.exe} filename. But if no scripts are
27950 found @value{GDBN} also tries script filenames matching the object file without
27951 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
27952 is attempted on any platform. This makes the script filenames compatible
27953 between Unix and MS-Windows hosts.
27956 @anchor{set auto-load scripts-directory}
27957 @kindex set auto-load scripts-directory
27958 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
27959 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
27960 may be delimited by the host platform path separator in use
27961 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
27963 Each entry here needs to be covered also by the security setting
27964 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
27966 @anchor{with-auto-load-dir}
27967 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
27968 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
27969 configuration option @option{--with-auto-load-dir}.
27971 Any reference to @file{$debugdir} will get replaced by
27972 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
27973 reference to @file{$datadir} will get replaced by @var{data-directory} which is
27974 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
27975 @file{$datadir} must be placed as a directory component --- either alone or
27976 delimited by @file{/} or @file{\} directory separators, depending on the host
27979 The list of directories uses path separator (@samp{:} on GNU and Unix
27980 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
27981 to the @env{PATH} environment variable.
27983 @anchor{show auto-load scripts-directory}
27984 @kindex show auto-load scripts-directory
27985 @item show auto-load scripts-directory
27986 Show @value{GDBN} auto-loaded scripts location.
27989 @value{GDBN} does not track which files it has already auto-loaded this way.
27990 @value{GDBN} will load the associated script every time the corresponding
27991 @var{objfile} is opened.
27992 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
27993 is evaluated more than once.
27995 @node dotdebug_gdb_scripts section
27996 @subsection The @code{.debug_gdb_scripts} section
27997 @cindex @code{.debug_gdb_scripts} section
27999 For systems using file formats like ELF and COFF,
28000 when @value{GDBN} loads a new object file
28001 it will look for a special section named @code{.debug_gdb_scripts}.
28002 If this section exists, its contents is a list of NUL-terminated names
28003 of scripts to load. Each entry begins with a non-NULL prefix byte that
28004 specifies the kind of entry, typically the extension language.
28006 @value{GDBN} will look for each specified script file first in the
28007 current directory and then along the source search path
28008 (@pxref{Source Path, ,Specifying Source Directories}),
28009 except that @file{$cdir} is not searched, since the compilation
28010 directory is not relevant to scripts.
28012 Entries can be placed in section @code{.debug_gdb_scripts} with,
28013 for example, this GCC macro for Python scripts.
28016 /* Note: The "MS" section flags are to remove duplicates. */
28017 #define DEFINE_GDB_PY_SCRIPT(script_name) \
28019 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
28020 .byte 1 /* Python */\n\
28021 .asciz \"" script_name "\"\n\
28027 Then one can reference the macro in a header or source file like this:
28030 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
28033 The script name may include directories if desired.
28035 Note that loading of this script file also requires accordingly configured
28036 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
28038 If the macro invocation is put in a header, any application or library
28039 using this header will get a reference to the specified script,
28040 and with the use of @code{"MS"} attributes on the section, the linker
28041 will remove duplicates.
28043 @node Which flavor to choose?
28044 @subsection Which flavor to choose?
28046 Given the multiple ways of auto-loading extensions, it might not always
28047 be clear which one to choose. This section provides some guidance.
28050 Benefits of the @file{-gdb.@var{ext}} way:
28054 Can be used with file formats that don't support multiple sections.
28057 Ease of finding scripts for public libraries.
28059 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
28060 in the source search path.
28061 For publicly installed libraries, e.g., @file{libstdc++}, there typically
28062 isn't a source directory in which to find the script.
28065 Doesn't require source code additions.
28069 Benefits of the @code{.debug_gdb_scripts} way:
28073 Works with static linking.
28075 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
28076 trigger their loading. When an application is statically linked the only
28077 objfile available is the executable, and it is cumbersome to attach all the
28078 scripts from all the input libraries to the executable's
28079 @file{-gdb.@var{ext}} script.
28082 Works with classes that are entirely inlined.
28084 Some classes can be entirely inlined, and thus there may not be an associated
28085 shared library to attach a @file{-gdb.@var{ext}} script to.
28088 Scripts needn't be copied out of the source tree.
28090 In some circumstances, apps can be built out of large collections of internal
28091 libraries, and the build infrastructure necessary to install the
28092 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
28093 cumbersome. It may be easier to specify the scripts in the
28094 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
28095 top of the source tree to the source search path.
28099 @section Creating new spellings of existing commands
28100 @cindex aliases for commands
28102 It is often useful to define alternate spellings of existing commands.
28103 For example, if a new @value{GDBN} command defined in Python has
28104 a long name to type, it is handy to have an abbreviated version of it
28105 that involves less typing.
28107 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
28108 of the @samp{step} command even though it is otherwise an ambiguous
28109 abbreviation of other commands like @samp{set} and @samp{show}.
28111 Aliases are also used to provide shortened or more common versions
28112 of multi-word commands. For example, @value{GDBN} provides the
28113 @samp{tty} alias of the @samp{set inferior-tty} command.
28115 You can define a new alias with the @samp{alias} command.
28120 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
28124 @var{ALIAS} specifies the name of the new alias.
28125 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
28128 @var{COMMAND} specifies the name of an existing command
28129 that is being aliased.
28131 The @samp{-a} option specifies that the new alias is an abbreviation
28132 of the command. Abbreviations are not shown in command
28133 lists displayed by the @samp{help} command.
28135 The @samp{--} option specifies the end of options,
28136 and is useful when @var{ALIAS} begins with a dash.
28138 Here is a simple example showing how to make an abbreviation
28139 of a command so that there is less to type.
28140 Suppose you were tired of typing @samp{disas}, the current
28141 shortest unambiguous abbreviation of the @samp{disassemble} command
28142 and you wanted an even shorter version named @samp{di}.
28143 The following will accomplish this.
28146 (gdb) alias -a di = disas
28149 Note that aliases are different from user-defined commands.
28150 With a user-defined command, you also need to write documentation
28151 for it with the @samp{document} command.
28152 An alias automatically picks up the documentation of the existing command.
28154 Here is an example where we make @samp{elms} an abbreviation of
28155 @samp{elements} in the @samp{set print elements} command.
28156 This is to show that you can make an abbreviation of any part
28160 (gdb) alias -a set print elms = set print elements
28161 (gdb) alias -a show print elms = show print elements
28162 (gdb) set p elms 20
28164 Limit on string chars or array elements to print is 200.
28167 Note that if you are defining an alias of a @samp{set} command,
28168 and you want to have an alias for the corresponding @samp{show}
28169 command, then you need to define the latter separately.
28171 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
28172 @var{ALIAS}, just as they are normally.
28175 (gdb) alias -a set pr elms = set p ele
28178 Finally, here is an example showing the creation of a one word
28179 alias for a more complex command.
28180 This creates alias @samp{spe} of the command @samp{set print elements}.
28183 (gdb) alias spe = set print elements
28188 @chapter Command Interpreters
28189 @cindex command interpreters
28191 @value{GDBN} supports multiple command interpreters, and some command
28192 infrastructure to allow users or user interface writers to switch
28193 between interpreters or run commands in other interpreters.
28195 @value{GDBN} currently supports two command interpreters, the console
28196 interpreter (sometimes called the command-line interpreter or @sc{cli})
28197 and the machine interface interpreter (or @sc{gdb/mi}). This manual
28198 describes both of these interfaces in great detail.
28200 By default, @value{GDBN} will start with the console interpreter.
28201 However, the user may choose to start @value{GDBN} with another
28202 interpreter by specifying the @option{-i} or @option{--interpreter}
28203 startup options. Defined interpreters include:
28207 @cindex console interpreter
28208 The traditional console or command-line interpreter. This is the most often
28209 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
28210 @value{GDBN} will use this interpreter.
28213 @cindex mi interpreter
28214 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
28215 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
28216 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
28220 @cindex mi2 interpreter
28221 The current @sc{gdb/mi} interface.
28224 @cindex mi1 interpreter
28225 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
28229 @cindex invoke another interpreter
28230 The interpreter being used by @value{GDBN} may not be dynamically
28231 switched at runtime. Although possible, this could lead to a very
28232 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
28233 enters the command "interpreter-set console" in a console view,
28234 @value{GDBN} would switch to using the console interpreter, rendering
28235 the IDE inoperable!
28237 @kindex interpreter-exec
28238 Although you may only choose a single interpreter at startup, you may execute
28239 commands in any interpreter from the current interpreter using the appropriate
28240 command. If you are running the console interpreter, simply use the
28241 @code{interpreter-exec} command:
28244 interpreter-exec mi "-data-list-register-names"
28247 @sc{gdb/mi} has a similar command, although it is only available in versions of
28248 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
28251 @chapter @value{GDBN} Text User Interface
28253 @cindex Text User Interface
28256 * TUI Overview:: TUI overview
28257 * TUI Keys:: TUI key bindings
28258 * TUI Single Key Mode:: TUI single key mode
28259 * TUI Commands:: TUI-specific commands
28260 * TUI Configuration:: TUI configuration variables
28263 The @value{GDBN} Text User Interface (TUI) is a terminal
28264 interface which uses the @code{curses} library to show the source
28265 file, the assembly output, the program registers and @value{GDBN}
28266 commands in separate text windows. The TUI mode is supported only
28267 on platforms where a suitable version of the @code{curses} library
28270 The TUI mode is enabled by default when you invoke @value{GDBN} as
28271 @samp{@value{GDBP} -tui}.
28272 You can also switch in and out of TUI mode while @value{GDBN} runs by
28273 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
28274 @xref{TUI Keys, ,TUI Key Bindings}.
28277 @section TUI Overview
28279 In TUI mode, @value{GDBN} can display several text windows:
28283 This window is the @value{GDBN} command window with the @value{GDBN}
28284 prompt and the @value{GDBN} output. The @value{GDBN} input is still
28285 managed using readline.
28288 The source window shows the source file of the program. The current
28289 line and active breakpoints are displayed in this window.
28292 The assembly window shows the disassembly output of the program.
28295 This window shows the processor registers. Registers are highlighted
28296 when their values change.
28299 The source and assembly windows show the current program position
28300 by highlighting the current line and marking it with a @samp{>} marker.
28301 Breakpoints are indicated with two markers. The first marker
28302 indicates the breakpoint type:
28306 Breakpoint which was hit at least once.
28309 Breakpoint which was never hit.
28312 Hardware breakpoint which was hit at least once.
28315 Hardware breakpoint which was never hit.
28318 The second marker indicates whether the breakpoint is enabled or not:
28322 Breakpoint is enabled.
28325 Breakpoint is disabled.
28328 The source, assembly and register windows are updated when the current
28329 thread changes, when the frame changes, or when the program counter
28332 These windows are not all visible at the same time. The command
28333 window is always visible. The others can be arranged in several
28344 source and assembly,
28347 source and registers, or
28350 assembly and registers.
28353 A status line above the command window shows the following information:
28357 Indicates the current @value{GDBN} target.
28358 (@pxref{Targets, ,Specifying a Debugging Target}).
28361 Gives the current process or thread number.
28362 When no process is being debugged, this field is set to @code{No process}.
28365 Gives the current function name for the selected frame.
28366 The name is demangled if demangling is turned on (@pxref{Print Settings}).
28367 When there is no symbol corresponding to the current program counter,
28368 the string @code{??} is displayed.
28371 Indicates the current line number for the selected frame.
28372 When the current line number is not known, the string @code{??} is displayed.
28375 Indicates the current program counter address.
28379 @section TUI Key Bindings
28380 @cindex TUI key bindings
28382 The TUI installs several key bindings in the readline keymaps
28383 @ifset SYSTEM_READLINE
28384 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
28386 @ifclear SYSTEM_READLINE
28387 (@pxref{Command Line Editing}).
28389 The following key bindings are installed for both TUI mode and the
28390 @value{GDBN} standard mode.
28399 Enter or leave the TUI mode. When leaving the TUI mode,
28400 the curses window management stops and @value{GDBN} operates using
28401 its standard mode, writing on the terminal directly. When reentering
28402 the TUI mode, control is given back to the curses windows.
28403 The screen is then refreshed.
28407 Use a TUI layout with only one window. The layout will
28408 either be @samp{source} or @samp{assembly}. When the TUI mode
28409 is not active, it will switch to the TUI mode.
28411 Think of this key binding as the Emacs @kbd{C-x 1} binding.
28415 Use a TUI layout with at least two windows. When the current
28416 layout already has two windows, the next layout with two windows is used.
28417 When a new layout is chosen, one window will always be common to the
28418 previous layout and the new one.
28420 Think of it as the Emacs @kbd{C-x 2} binding.
28424 Change the active window. The TUI associates several key bindings
28425 (like scrolling and arrow keys) with the active window. This command
28426 gives the focus to the next TUI window.
28428 Think of it as the Emacs @kbd{C-x o} binding.
28432 Switch in and out of the TUI SingleKey mode that binds single
28433 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
28436 The following key bindings only work in the TUI mode:
28441 Scroll the active window one page up.
28445 Scroll the active window one page down.
28449 Scroll the active window one line up.
28453 Scroll the active window one line down.
28457 Scroll the active window one column left.
28461 Scroll the active window one column right.
28465 Refresh the screen.
28468 Because the arrow keys scroll the active window in the TUI mode, they
28469 are not available for their normal use by readline unless the command
28470 window has the focus. When another window is active, you must use
28471 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
28472 and @kbd{C-f} to control the command window.
28474 @node TUI Single Key Mode
28475 @section TUI Single Key Mode
28476 @cindex TUI single key mode
28478 The TUI also provides a @dfn{SingleKey} mode, which binds several
28479 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
28480 switch into this mode, where the following key bindings are used:
28483 @kindex c @r{(SingleKey TUI key)}
28487 @kindex d @r{(SingleKey TUI key)}
28491 @kindex f @r{(SingleKey TUI key)}
28495 @kindex n @r{(SingleKey TUI key)}
28499 @kindex q @r{(SingleKey TUI key)}
28501 exit the SingleKey mode.
28503 @kindex r @r{(SingleKey TUI key)}
28507 @kindex s @r{(SingleKey TUI key)}
28511 @kindex u @r{(SingleKey TUI key)}
28515 @kindex v @r{(SingleKey TUI key)}
28519 @kindex w @r{(SingleKey TUI key)}
28524 Other keys temporarily switch to the @value{GDBN} command prompt.
28525 The key that was pressed is inserted in the editing buffer so that
28526 it is possible to type most @value{GDBN} commands without interaction
28527 with the TUI SingleKey mode. Once the command is entered the TUI
28528 SingleKey mode is restored. The only way to permanently leave
28529 this mode is by typing @kbd{q} or @kbd{C-x s}.
28533 @section TUI-specific Commands
28534 @cindex TUI commands
28536 The TUI has specific commands to control the text windows.
28537 These commands are always available, even when @value{GDBN} is not in
28538 the TUI mode. When @value{GDBN} is in the standard mode, most
28539 of these commands will automatically switch to the TUI mode.
28541 Note that if @value{GDBN}'s @code{stdout} is not connected to a
28542 terminal, or @value{GDBN} has been started with the machine interface
28543 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
28544 these commands will fail with an error, because it would not be
28545 possible or desirable to enable curses window management.
28550 List and give the size of all displayed windows.
28554 Display the next layout.
28557 Display the previous layout.
28560 Display the source window only.
28563 Display the assembly window only.
28566 Display the source and assembly window.
28569 Display the register window together with the source or assembly window.
28573 Make the next window active for scrolling.
28576 Make the previous window active for scrolling.
28579 Make the source window active for scrolling.
28582 Make the assembly window active for scrolling.
28585 Make the register window active for scrolling.
28588 Make the command window active for scrolling.
28592 Refresh the screen. This is similar to typing @kbd{C-L}.
28594 @item tui reg float
28596 Show the floating point registers in the register window.
28598 @item tui reg general
28599 Show the general registers in the register window.
28602 Show the next register group. The list of register groups as well as
28603 their order is target specific. The predefined register groups are the
28604 following: @code{general}, @code{float}, @code{system}, @code{vector},
28605 @code{all}, @code{save}, @code{restore}.
28607 @item tui reg system
28608 Show the system registers in the register window.
28612 Update the source window and the current execution point.
28614 @item winheight @var{name} +@var{count}
28615 @itemx winheight @var{name} -@var{count}
28617 Change the height of the window @var{name} by @var{count}
28618 lines. Positive counts increase the height, while negative counts
28621 @item tabset @var{nchars}
28623 Set the width of tab stops to be @var{nchars} characters.
28626 @node TUI Configuration
28627 @section TUI Configuration Variables
28628 @cindex TUI configuration variables
28630 Several configuration variables control the appearance of TUI windows.
28633 @item set tui border-kind @var{kind}
28634 @kindex set tui border-kind
28635 Select the border appearance for the source, assembly and register windows.
28636 The possible values are the following:
28639 Use a space character to draw the border.
28642 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
28645 Use the Alternate Character Set to draw the border. The border is
28646 drawn using character line graphics if the terminal supports them.
28649 @item set tui border-mode @var{mode}
28650 @kindex set tui border-mode
28651 @itemx set tui active-border-mode @var{mode}
28652 @kindex set tui active-border-mode
28653 Select the display attributes for the borders of the inactive windows
28654 or the active window. The @var{mode} can be one of the following:
28657 Use normal attributes to display the border.
28663 Use reverse video mode.
28666 Use half bright mode.
28668 @item half-standout
28669 Use half bright and standout mode.
28672 Use extra bright or bold mode.
28674 @item bold-standout
28675 Use extra bright or bold and standout mode.
28680 @chapter Using @value{GDBN} under @sc{gnu} Emacs
28683 @cindex @sc{gnu} Emacs
28684 A special interface allows you to use @sc{gnu} Emacs to view (and
28685 edit) the source files for the program you are debugging with
28688 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
28689 executable file you want to debug as an argument. This command starts
28690 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
28691 created Emacs buffer.
28692 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
28694 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
28699 All ``terminal'' input and output goes through an Emacs buffer, called
28702 This applies both to @value{GDBN} commands and their output, and to the input
28703 and output done by the program you are debugging.
28705 This is useful because it means that you can copy the text of previous
28706 commands and input them again; you can even use parts of the output
28709 All the facilities of Emacs' Shell mode are available for interacting
28710 with your program. In particular, you can send signals the usual
28711 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
28715 @value{GDBN} displays source code through Emacs.
28717 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
28718 source file for that frame and puts an arrow (@samp{=>}) at the
28719 left margin of the current line. Emacs uses a separate buffer for
28720 source display, and splits the screen to show both your @value{GDBN} session
28723 Explicit @value{GDBN} @code{list} or search commands still produce output as
28724 usual, but you probably have no reason to use them from Emacs.
28727 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
28728 a graphical mode, enabled by default, which provides further buffers
28729 that can control the execution and describe the state of your program.
28730 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
28732 If you specify an absolute file name when prompted for the @kbd{M-x
28733 gdb} argument, then Emacs sets your current working directory to where
28734 your program resides. If you only specify the file name, then Emacs
28735 sets your current working directory to the directory associated
28736 with the previous buffer. In this case, @value{GDBN} may find your
28737 program by searching your environment's @code{PATH} variable, but on
28738 some operating systems it might not find the source. So, although the
28739 @value{GDBN} input and output session proceeds normally, the auxiliary
28740 buffer does not display the current source and line of execution.
28742 The initial working directory of @value{GDBN} is printed on the top
28743 line of the GUD buffer and this serves as a default for the commands
28744 that specify files for @value{GDBN} to operate on. @xref{Files,
28745 ,Commands to Specify Files}.
28747 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
28748 need to call @value{GDBN} by a different name (for example, if you
28749 keep several configurations around, with different names) you can
28750 customize the Emacs variable @code{gud-gdb-command-name} to run the
28753 In the GUD buffer, you can use these special Emacs commands in
28754 addition to the standard Shell mode commands:
28758 Describe the features of Emacs' GUD Mode.
28761 Execute to another source line, like the @value{GDBN} @code{step} command; also
28762 update the display window to show the current file and location.
28765 Execute to next source line in this function, skipping all function
28766 calls, like the @value{GDBN} @code{next} command. Then update the display window
28767 to show the current file and location.
28770 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
28771 display window accordingly.
28774 Execute until exit from the selected stack frame, like the @value{GDBN}
28775 @code{finish} command.
28778 Continue execution of your program, like the @value{GDBN} @code{continue}
28782 Go up the number of frames indicated by the numeric argument
28783 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
28784 like the @value{GDBN} @code{up} command.
28787 Go down the number of frames indicated by the numeric argument, like the
28788 @value{GDBN} @code{down} command.
28791 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
28792 tells @value{GDBN} to set a breakpoint on the source line point is on.
28794 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
28795 separate frame which shows a backtrace when the GUD buffer is current.
28796 Move point to any frame in the stack and type @key{RET} to make it
28797 become the current frame and display the associated source in the
28798 source buffer. Alternatively, click @kbd{Mouse-2} to make the
28799 selected frame become the current one. In graphical mode, the
28800 speedbar displays watch expressions.
28802 If you accidentally delete the source-display buffer, an easy way to get
28803 it back is to type the command @code{f} in the @value{GDBN} buffer, to
28804 request a frame display; when you run under Emacs, this recreates
28805 the source buffer if necessary to show you the context of the current
28808 The source files displayed in Emacs are in ordinary Emacs buffers
28809 which are visiting the source files in the usual way. You can edit
28810 the files with these buffers if you wish; but keep in mind that @value{GDBN}
28811 communicates with Emacs in terms of line numbers. If you add or
28812 delete lines from the text, the line numbers that @value{GDBN} knows cease
28813 to correspond properly with the code.
28815 A more detailed description of Emacs' interaction with @value{GDBN} is
28816 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
28820 @chapter The @sc{gdb/mi} Interface
28822 @unnumberedsec Function and Purpose
28824 @cindex @sc{gdb/mi}, its purpose
28825 @sc{gdb/mi} is a line based machine oriented text interface to
28826 @value{GDBN} and is activated by specifying using the
28827 @option{--interpreter} command line option (@pxref{Mode Options}). It
28828 is specifically intended to support the development of systems which
28829 use the debugger as just one small component of a larger system.
28831 This chapter is a specification of the @sc{gdb/mi} interface. It is written
28832 in the form of a reference manual.
28834 Note that @sc{gdb/mi} is still under construction, so some of the
28835 features described below are incomplete and subject to change
28836 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
28838 @unnumberedsec Notation and Terminology
28840 @cindex notational conventions, for @sc{gdb/mi}
28841 This chapter uses the following notation:
28845 @code{|} separates two alternatives.
28848 @code{[ @var{something} ]} indicates that @var{something} is optional:
28849 it may or may not be given.
28852 @code{( @var{group} )*} means that @var{group} inside the parentheses
28853 may repeat zero or more times.
28856 @code{( @var{group} )+} means that @var{group} inside the parentheses
28857 may repeat one or more times.
28860 @code{"@var{string}"} means a literal @var{string}.
28864 @heading Dependencies
28868 * GDB/MI General Design::
28869 * GDB/MI Command Syntax::
28870 * GDB/MI Compatibility with CLI::
28871 * GDB/MI Development and Front Ends::
28872 * GDB/MI Output Records::
28873 * GDB/MI Simple Examples::
28874 * GDB/MI Command Description Format::
28875 * GDB/MI Breakpoint Commands::
28876 * GDB/MI Catchpoint Commands::
28877 * GDB/MI Program Context::
28878 * GDB/MI Thread Commands::
28879 * GDB/MI Ada Tasking Commands::
28880 * GDB/MI Program Execution::
28881 * GDB/MI Stack Manipulation::
28882 * GDB/MI Variable Objects::
28883 * GDB/MI Data Manipulation::
28884 * GDB/MI Tracepoint Commands::
28885 * GDB/MI Symbol Query::
28886 * GDB/MI File Commands::
28888 * GDB/MI Kod Commands::
28889 * GDB/MI Memory Overlay Commands::
28890 * GDB/MI Signal Handling Commands::
28892 * GDB/MI Target Manipulation::
28893 * GDB/MI File Transfer Commands::
28894 * GDB/MI Ada Exceptions Commands::
28895 * GDB/MI Support Commands::
28896 * GDB/MI Miscellaneous Commands::
28899 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28900 @node GDB/MI General Design
28901 @section @sc{gdb/mi} General Design
28902 @cindex GDB/MI General Design
28904 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
28905 parts---commands sent to @value{GDBN}, responses to those commands
28906 and notifications. Each command results in exactly one response,
28907 indicating either successful completion of the command, or an error.
28908 For the commands that do not resume the target, the response contains the
28909 requested information. For the commands that resume the target, the
28910 response only indicates whether the target was successfully resumed.
28911 Notifications is the mechanism for reporting changes in the state of the
28912 target, or in @value{GDBN} state, that cannot conveniently be associated with
28913 a command and reported as part of that command response.
28915 The important examples of notifications are:
28919 Exec notifications. These are used to report changes in
28920 target state---when a target is resumed, or stopped. It would not
28921 be feasible to include this information in response of resuming
28922 commands, because one resume commands can result in multiple events in
28923 different threads. Also, quite some time may pass before any event
28924 happens in the target, while a frontend needs to know whether the resuming
28925 command itself was successfully executed.
28928 Console output, and status notifications. Console output
28929 notifications are used to report output of CLI commands, as well as
28930 diagnostics for other commands. Status notifications are used to
28931 report the progress of a long-running operation. Naturally, including
28932 this information in command response would mean no output is produced
28933 until the command is finished, which is undesirable.
28936 General notifications. Commands may have various side effects on
28937 the @value{GDBN} or target state beyond their official purpose. For example,
28938 a command may change the selected thread. Although such changes can
28939 be included in command response, using notification allows for more
28940 orthogonal frontend design.
28944 There's no guarantee that whenever an MI command reports an error,
28945 @value{GDBN} or the target are in any specific state, and especially,
28946 the state is not reverted to the state before the MI command was
28947 processed. Therefore, whenever an MI command results in an error,
28948 we recommend that the frontend refreshes all the information shown in
28949 the user interface.
28953 * Context management::
28954 * Asynchronous and non-stop modes::
28958 @node Context management
28959 @subsection Context management
28961 @subsubsection Threads and Frames
28963 In most cases when @value{GDBN} accesses the target, this access is
28964 done in context of a specific thread and frame (@pxref{Frames}).
28965 Often, even when accessing global data, the target requires that a thread
28966 be specified. The CLI interface maintains the selected thread and frame,
28967 and supplies them to target on each command. This is convenient,
28968 because a command line user would not want to specify that information
28969 explicitly on each command, and because user interacts with
28970 @value{GDBN} via a single terminal, so no confusion is possible as
28971 to what thread and frame are the current ones.
28973 In the case of MI, the concept of selected thread and frame is less
28974 useful. First, a frontend can easily remember this information
28975 itself. Second, a graphical frontend can have more than one window,
28976 each one used for debugging a different thread, and the frontend might
28977 want to access additional threads for internal purposes. This
28978 increases the risk that by relying on implicitly selected thread, the
28979 frontend may be operating on a wrong one. Therefore, each MI command
28980 should explicitly specify which thread and frame to operate on. To
28981 make it possible, each MI command accepts the @samp{--thread} and
28982 @samp{--frame} options, the value to each is @value{GDBN} identifier
28983 for thread and frame to operate on.
28985 Usually, each top-level window in a frontend allows the user to select
28986 a thread and a frame, and remembers the user selection for further
28987 operations. However, in some cases @value{GDBN} may suggest that the
28988 current thread be changed. For example, when stopping on a breakpoint
28989 it is reasonable to switch to the thread where breakpoint is hit. For
28990 another example, if the user issues the CLI @samp{thread} command via
28991 the frontend, it is desirable to change the frontend's selected thread to the
28992 one specified by user. @value{GDBN} communicates the suggestion to
28993 change current thread using the @samp{=thread-selected} notification.
28994 No such notification is available for the selected frame at the moment.
28996 Note that historically, MI shares the selected thread with CLI, so
28997 frontends used the @code{-thread-select} to execute commands in the
28998 right context. However, getting this to work right is cumbersome. The
28999 simplest way is for frontend to emit @code{-thread-select} command
29000 before every command. This doubles the number of commands that need
29001 to be sent. The alternative approach is to suppress @code{-thread-select}
29002 if the selected thread in @value{GDBN} is supposed to be identical to the
29003 thread the frontend wants to operate on. However, getting this
29004 optimization right can be tricky. In particular, if the frontend
29005 sends several commands to @value{GDBN}, and one of the commands changes the
29006 selected thread, then the behaviour of subsequent commands will
29007 change. So, a frontend should either wait for response from such
29008 problematic commands, or explicitly add @code{-thread-select} for
29009 all subsequent commands. No frontend is known to do this exactly
29010 right, so it is suggested to just always pass the @samp{--thread} and
29011 @samp{--frame} options.
29013 @subsubsection Language
29015 The execution of several commands depends on which language is selected.
29016 By default, the current language (@pxref{show language}) is used.
29017 But for commands known to be language-sensitive, it is recommended
29018 to use the @samp{--language} option. This option takes one argument,
29019 which is the name of the language to use while executing the command.
29023 -data-evaluate-expression --language c "sizeof (void*)"
29028 The valid language names are the same names accepted by the
29029 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
29030 @samp{local} or @samp{unknown}.
29032 @node Asynchronous and non-stop modes
29033 @subsection Asynchronous command execution and non-stop mode
29035 On some targets, @value{GDBN} is capable of processing MI commands
29036 even while the target is running. This is called @dfn{asynchronous
29037 command execution} (@pxref{Background Execution}). The frontend may
29038 specify a preferrence for asynchronous execution using the
29039 @code{-gdb-set target-async 1} command, which should be emitted before
29040 either running the executable or attaching to the target. After the
29041 frontend has started the executable or attached to the target, it can
29042 find if asynchronous execution is enabled using the
29043 @code{-list-target-features} command.
29045 Even if @value{GDBN} can accept a command while target is running,
29046 many commands that access the target do not work when the target is
29047 running. Therefore, asynchronous command execution is most useful
29048 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
29049 it is possible to examine the state of one thread, while other threads
29052 When a given thread is running, MI commands that try to access the
29053 target in the context of that thread may not work, or may work only on
29054 some targets. In particular, commands that try to operate on thread's
29055 stack will not work, on any target. Commands that read memory, or
29056 modify breakpoints, may work or not work, depending on the target. Note
29057 that even commands that operate on global state, such as @code{print},
29058 @code{set}, and breakpoint commands, still access the target in the
29059 context of a specific thread, so frontend should try to find a
29060 stopped thread and perform the operation on that thread (using the
29061 @samp{--thread} option).
29063 Which commands will work in the context of a running thread is
29064 highly target dependent. However, the two commands
29065 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
29066 to find the state of a thread, will always work.
29068 @node Thread groups
29069 @subsection Thread groups
29070 @value{GDBN} may be used to debug several processes at the same time.
29071 On some platfroms, @value{GDBN} may support debugging of several
29072 hardware systems, each one having several cores with several different
29073 processes running on each core. This section describes the MI
29074 mechanism to support such debugging scenarios.
29076 The key observation is that regardless of the structure of the
29077 target, MI can have a global list of threads, because most commands that
29078 accept the @samp{--thread} option do not need to know what process that
29079 thread belongs to. Therefore, it is not necessary to introduce
29080 neither additional @samp{--process} option, nor an notion of the
29081 current process in the MI interface. The only strictly new feature
29082 that is required is the ability to find how the threads are grouped
29085 To allow the user to discover such grouping, and to support arbitrary
29086 hierarchy of machines/cores/processes, MI introduces the concept of a
29087 @dfn{thread group}. Thread group is a collection of threads and other
29088 thread groups. A thread group always has a string identifier, a type,
29089 and may have additional attributes specific to the type. A new
29090 command, @code{-list-thread-groups}, returns the list of top-level
29091 thread groups, which correspond to processes that @value{GDBN} is
29092 debugging at the moment. By passing an identifier of a thread group
29093 to the @code{-list-thread-groups} command, it is possible to obtain
29094 the members of specific thread group.
29096 To allow the user to easily discover processes, and other objects, he
29097 wishes to debug, a concept of @dfn{available thread group} is
29098 introduced. Available thread group is an thread group that
29099 @value{GDBN} is not debugging, but that can be attached to, using the
29100 @code{-target-attach} command. The list of available top-level thread
29101 groups can be obtained using @samp{-list-thread-groups --available}.
29102 In general, the content of a thread group may be only retrieved only
29103 after attaching to that thread group.
29105 Thread groups are related to inferiors (@pxref{Inferiors and
29106 Programs}). Each inferior corresponds to a thread group of a special
29107 type @samp{process}, and some additional operations are permitted on
29108 such thread groups.
29110 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29111 @node GDB/MI Command Syntax
29112 @section @sc{gdb/mi} Command Syntax
29115 * GDB/MI Input Syntax::
29116 * GDB/MI Output Syntax::
29119 @node GDB/MI Input Syntax
29120 @subsection @sc{gdb/mi} Input Syntax
29122 @cindex input syntax for @sc{gdb/mi}
29123 @cindex @sc{gdb/mi}, input syntax
29125 @item @var{command} @expansion{}
29126 @code{@var{cli-command} | @var{mi-command}}
29128 @item @var{cli-command} @expansion{}
29129 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
29130 @var{cli-command} is any existing @value{GDBN} CLI command.
29132 @item @var{mi-command} @expansion{}
29133 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
29134 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
29136 @item @var{token} @expansion{}
29137 "any sequence of digits"
29139 @item @var{option} @expansion{}
29140 @code{"-" @var{parameter} [ " " @var{parameter} ]}
29142 @item @var{parameter} @expansion{}
29143 @code{@var{non-blank-sequence} | @var{c-string}}
29145 @item @var{operation} @expansion{}
29146 @emph{any of the operations described in this chapter}
29148 @item @var{non-blank-sequence} @expansion{}
29149 @emph{anything, provided it doesn't contain special characters such as
29150 "-", @var{nl}, """ and of course " "}
29152 @item @var{c-string} @expansion{}
29153 @code{""" @var{seven-bit-iso-c-string-content} """}
29155 @item @var{nl} @expansion{}
29164 The CLI commands are still handled by the @sc{mi} interpreter; their
29165 output is described below.
29168 The @code{@var{token}}, when present, is passed back when the command
29172 Some @sc{mi} commands accept optional arguments as part of the parameter
29173 list. Each option is identified by a leading @samp{-} (dash) and may be
29174 followed by an optional argument parameter. Options occur first in the
29175 parameter list and can be delimited from normal parameters using
29176 @samp{--} (this is useful when some parameters begin with a dash).
29183 We want easy access to the existing CLI syntax (for debugging).
29186 We want it to be easy to spot a @sc{mi} operation.
29189 @node GDB/MI Output Syntax
29190 @subsection @sc{gdb/mi} Output Syntax
29192 @cindex output syntax of @sc{gdb/mi}
29193 @cindex @sc{gdb/mi}, output syntax
29194 The output from @sc{gdb/mi} consists of zero or more out-of-band records
29195 followed, optionally, by a single result record. This result record
29196 is for the most recent command. The sequence of output records is
29197 terminated by @samp{(gdb)}.
29199 If an input command was prefixed with a @code{@var{token}} then the
29200 corresponding output for that command will also be prefixed by that same
29204 @item @var{output} @expansion{}
29205 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
29207 @item @var{result-record} @expansion{}
29208 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
29210 @item @var{out-of-band-record} @expansion{}
29211 @code{@var{async-record} | @var{stream-record}}
29213 @item @var{async-record} @expansion{}
29214 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
29216 @item @var{exec-async-output} @expansion{}
29217 @code{[ @var{token} ] "*" @var{async-output nl}}
29219 @item @var{status-async-output} @expansion{}
29220 @code{[ @var{token} ] "+" @var{async-output nl}}
29222 @item @var{notify-async-output} @expansion{}
29223 @code{[ @var{token} ] "=" @var{async-output nl}}
29225 @item @var{async-output} @expansion{}
29226 @code{@var{async-class} ( "," @var{result} )*}
29228 @item @var{result-class} @expansion{}
29229 @code{"done" | "running" | "connected" | "error" | "exit"}
29231 @item @var{async-class} @expansion{}
29232 @code{"stopped" | @var{others}} (where @var{others} will be added
29233 depending on the needs---this is still in development).
29235 @item @var{result} @expansion{}
29236 @code{ @var{variable} "=" @var{value}}
29238 @item @var{variable} @expansion{}
29239 @code{ @var{string} }
29241 @item @var{value} @expansion{}
29242 @code{ @var{const} | @var{tuple} | @var{list} }
29244 @item @var{const} @expansion{}
29245 @code{@var{c-string}}
29247 @item @var{tuple} @expansion{}
29248 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
29250 @item @var{list} @expansion{}
29251 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
29252 @var{result} ( "," @var{result} )* "]" }
29254 @item @var{stream-record} @expansion{}
29255 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
29257 @item @var{console-stream-output} @expansion{}
29258 @code{"~" @var{c-string nl}}
29260 @item @var{target-stream-output} @expansion{}
29261 @code{"@@" @var{c-string nl}}
29263 @item @var{log-stream-output} @expansion{}
29264 @code{"&" @var{c-string nl}}
29266 @item @var{nl} @expansion{}
29269 @item @var{token} @expansion{}
29270 @emph{any sequence of digits}.
29278 All output sequences end in a single line containing a period.
29281 The @code{@var{token}} is from the corresponding request. Note that
29282 for all async output, while the token is allowed by the grammar and
29283 may be output by future versions of @value{GDBN} for select async
29284 output messages, it is generally omitted. Frontends should treat
29285 all async output as reporting general changes in the state of the
29286 target and there should be no need to associate async output to any
29290 @cindex status output in @sc{gdb/mi}
29291 @var{status-async-output} contains on-going status information about the
29292 progress of a slow operation. It can be discarded. All status output is
29293 prefixed by @samp{+}.
29296 @cindex async output in @sc{gdb/mi}
29297 @var{exec-async-output} contains asynchronous state change on the target
29298 (stopped, started, disappeared). All async output is prefixed by
29302 @cindex notify output in @sc{gdb/mi}
29303 @var{notify-async-output} contains supplementary information that the
29304 client should handle (e.g., a new breakpoint information). All notify
29305 output is prefixed by @samp{=}.
29308 @cindex console output in @sc{gdb/mi}
29309 @var{console-stream-output} is output that should be displayed as is in the
29310 console. It is the textual response to a CLI command. All the console
29311 output is prefixed by @samp{~}.
29314 @cindex target output in @sc{gdb/mi}
29315 @var{target-stream-output} is the output produced by the target program.
29316 All the target output is prefixed by @samp{@@}.
29319 @cindex log output in @sc{gdb/mi}
29320 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
29321 instance messages that should be displayed as part of an error log. All
29322 the log output is prefixed by @samp{&}.
29325 @cindex list output in @sc{gdb/mi}
29326 New @sc{gdb/mi} commands should only output @var{lists} containing
29332 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
29333 details about the various output records.
29335 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29336 @node GDB/MI Compatibility with CLI
29337 @section @sc{gdb/mi} Compatibility with CLI
29339 @cindex compatibility, @sc{gdb/mi} and CLI
29340 @cindex @sc{gdb/mi}, compatibility with CLI
29342 For the developers convenience CLI commands can be entered directly,
29343 but there may be some unexpected behaviour. For example, commands
29344 that query the user will behave as if the user replied yes, breakpoint
29345 command lists are not executed and some CLI commands, such as
29346 @code{if}, @code{when} and @code{define}, prompt for further input with
29347 @samp{>}, which is not valid MI output.
29349 This feature may be removed at some stage in the future and it is
29350 recommended that front ends use the @code{-interpreter-exec} command
29351 (@pxref{-interpreter-exec}).
29353 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29354 @node GDB/MI Development and Front Ends
29355 @section @sc{gdb/mi} Development and Front Ends
29356 @cindex @sc{gdb/mi} development
29358 The application which takes the MI output and presents the state of the
29359 program being debugged to the user is called a @dfn{front end}.
29361 Although @sc{gdb/mi} is still incomplete, it is currently being used
29362 by a variety of front ends to @value{GDBN}. This makes it difficult
29363 to introduce new functionality without breaking existing usage. This
29364 section tries to minimize the problems by describing how the protocol
29367 Some changes in MI need not break a carefully designed front end, and
29368 for these the MI version will remain unchanged. The following is a
29369 list of changes that may occur within one level, so front ends should
29370 parse MI output in a way that can handle them:
29374 New MI commands may be added.
29377 New fields may be added to the output of any MI command.
29380 The range of values for fields with specified values, e.g.,
29381 @code{in_scope} (@pxref{-var-update}) may be extended.
29383 @c The format of field's content e.g type prefix, may change so parse it
29384 @c at your own risk. Yes, in general?
29386 @c The order of fields may change? Shouldn't really matter but it might
29387 @c resolve inconsistencies.
29390 If the changes are likely to break front ends, the MI version level
29391 will be increased by one. This will allow the front end to parse the
29392 output according to the MI version. Apart from mi0, new versions of
29393 @value{GDBN} will not support old versions of MI and it will be the
29394 responsibility of the front end to work with the new one.
29396 @c Starting with mi3, add a new command -mi-version that prints the MI
29399 The best way to avoid unexpected changes in MI that might break your front
29400 end is to make your project known to @value{GDBN} developers and
29401 follow development on @email{gdb@@sourceware.org} and
29402 @email{gdb-patches@@sourceware.org}.
29403 @cindex mailing lists
29405 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29406 @node GDB/MI Output Records
29407 @section @sc{gdb/mi} Output Records
29410 * GDB/MI Result Records::
29411 * GDB/MI Stream Records::
29412 * GDB/MI Async Records::
29413 * GDB/MI Breakpoint Information::
29414 * GDB/MI Frame Information::
29415 * GDB/MI Thread Information::
29416 * GDB/MI Ada Exception Information::
29419 @node GDB/MI Result Records
29420 @subsection @sc{gdb/mi} Result Records
29422 @cindex result records in @sc{gdb/mi}
29423 @cindex @sc{gdb/mi}, result records
29424 In addition to a number of out-of-band notifications, the response to a
29425 @sc{gdb/mi} command includes one of the following result indications:
29429 @item "^done" [ "," @var{results} ]
29430 The synchronous operation was successful, @code{@var{results}} are the return
29435 This result record is equivalent to @samp{^done}. Historically, it
29436 was output instead of @samp{^done} if the command has resumed the
29437 target. This behaviour is maintained for backward compatibility, but
29438 all frontends should treat @samp{^done} and @samp{^running}
29439 identically and rely on the @samp{*running} output record to determine
29440 which threads are resumed.
29444 @value{GDBN} has connected to a remote target.
29446 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
29448 The operation failed. The @code{msg=@var{c-string}} variable contains
29449 the corresponding error message.
29451 If present, the @code{code=@var{c-string}} variable provides an error
29452 code on which consumers can rely on to detect the corresponding
29453 error condition. At present, only one error code is defined:
29456 @item "undefined-command"
29457 Indicates that the command causing the error does not exist.
29462 @value{GDBN} has terminated.
29466 @node GDB/MI Stream Records
29467 @subsection @sc{gdb/mi} Stream Records
29469 @cindex @sc{gdb/mi}, stream records
29470 @cindex stream records in @sc{gdb/mi}
29471 @value{GDBN} internally maintains a number of output streams: the console, the
29472 target, and the log. The output intended for each of these streams is
29473 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
29475 Each stream record begins with a unique @dfn{prefix character} which
29476 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
29477 Syntax}). In addition to the prefix, each stream record contains a
29478 @code{@var{string-output}}. This is either raw text (with an implicit new
29479 line) or a quoted C string (which does not contain an implicit newline).
29482 @item "~" @var{string-output}
29483 The console output stream contains text that should be displayed in the
29484 CLI console window. It contains the textual responses to CLI commands.
29486 @item "@@" @var{string-output}
29487 The target output stream contains any textual output from the running
29488 target. This is only present when GDB's event loop is truly
29489 asynchronous, which is currently only the case for remote targets.
29491 @item "&" @var{string-output}
29492 The log stream contains debugging messages being produced by @value{GDBN}'s
29496 @node GDB/MI Async Records
29497 @subsection @sc{gdb/mi} Async Records
29499 @cindex async records in @sc{gdb/mi}
29500 @cindex @sc{gdb/mi}, async records
29501 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
29502 additional changes that have occurred. Those changes can either be a
29503 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
29504 target activity (e.g., target stopped).
29506 The following is the list of possible async records:
29510 @item *running,thread-id="@var{thread}"
29511 The target is now running. The @var{thread} field tells which
29512 specific thread is now running, and can be @samp{all} if all threads
29513 are running. The frontend should assume that no interaction with a
29514 running thread is possible after this notification is produced.
29515 The frontend should not assume that this notification is output
29516 only once for any command. @value{GDBN} may emit this notification
29517 several times, either for different threads, because it cannot resume
29518 all threads together, or even for a single thread, if the thread must
29519 be stepped though some code before letting it run freely.
29521 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
29522 The target has stopped. The @var{reason} field can have one of the
29526 @item breakpoint-hit
29527 A breakpoint was reached.
29528 @item watchpoint-trigger
29529 A watchpoint was triggered.
29530 @item read-watchpoint-trigger
29531 A read watchpoint was triggered.
29532 @item access-watchpoint-trigger
29533 An access watchpoint was triggered.
29534 @item function-finished
29535 An -exec-finish or similar CLI command was accomplished.
29536 @item location-reached
29537 An -exec-until or similar CLI command was accomplished.
29538 @item watchpoint-scope
29539 A watchpoint has gone out of scope.
29540 @item end-stepping-range
29541 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
29542 similar CLI command was accomplished.
29543 @item exited-signalled
29544 The inferior exited because of a signal.
29546 The inferior exited.
29547 @item exited-normally
29548 The inferior exited normally.
29549 @item signal-received
29550 A signal was received by the inferior.
29552 The inferior has stopped due to a library being loaded or unloaded.
29553 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
29554 set or when a @code{catch load} or @code{catch unload} catchpoint is
29555 in use (@pxref{Set Catchpoints}).
29557 The inferior has forked. This is reported when @code{catch fork}
29558 (@pxref{Set Catchpoints}) has been used.
29560 The inferior has vforked. This is reported in when @code{catch vfork}
29561 (@pxref{Set Catchpoints}) has been used.
29562 @item syscall-entry
29563 The inferior entered a system call. This is reported when @code{catch
29564 syscall} (@pxref{Set Catchpoints}) has been used.
29565 @item syscall-entry
29566 The inferior returned from a system call. This is reported when
29567 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
29569 The inferior called @code{exec}. This is reported when @code{catch exec}
29570 (@pxref{Set Catchpoints}) has been used.
29573 The @var{id} field identifies the thread that directly caused the stop
29574 -- for example by hitting a breakpoint. Depending on whether all-stop
29575 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
29576 stop all threads, or only the thread that directly triggered the stop.
29577 If all threads are stopped, the @var{stopped} field will have the
29578 value of @code{"all"}. Otherwise, the value of the @var{stopped}
29579 field will be a list of thread identifiers. Presently, this list will
29580 always include a single thread, but frontend should be prepared to see
29581 several threads in the list. The @var{core} field reports the
29582 processor core on which the stop event has happened. This field may be absent
29583 if such information is not available.
29585 @item =thread-group-added,id="@var{id}"
29586 @itemx =thread-group-removed,id="@var{id}"
29587 A thread group was either added or removed. The @var{id} field
29588 contains the @value{GDBN} identifier of the thread group. When a thread
29589 group is added, it generally might not be associated with a running
29590 process. When a thread group is removed, its id becomes invalid and
29591 cannot be used in any way.
29593 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
29594 A thread group became associated with a running program,
29595 either because the program was just started or the thread group
29596 was attached to a program. The @var{id} field contains the
29597 @value{GDBN} identifier of the thread group. The @var{pid} field
29598 contains process identifier, specific to the operating system.
29600 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
29601 A thread group is no longer associated with a running program,
29602 either because the program has exited, or because it was detached
29603 from. The @var{id} field contains the @value{GDBN} identifier of the
29604 thread group. @var{code} is the exit code of the inferior; it exists
29605 only when the inferior exited with some code.
29607 @item =thread-created,id="@var{id}",group-id="@var{gid}"
29608 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
29609 A thread either was created, or has exited. The @var{id} field
29610 contains the @value{GDBN} identifier of the thread. The @var{gid}
29611 field identifies the thread group this thread belongs to.
29613 @item =thread-selected,id="@var{id}"
29614 Informs that the selected thread was changed as result of the last
29615 command. This notification is not emitted as result of @code{-thread-select}
29616 command but is emitted whenever an MI command that is not documented
29617 to change the selected thread actually changes it. In particular,
29618 invoking, directly or indirectly (via user-defined command), the CLI
29619 @code{thread} command, will generate this notification.
29621 We suggest that in response to this notification, front ends
29622 highlight the selected thread and cause subsequent commands to apply to
29625 @item =library-loaded,...
29626 Reports that a new library file was loaded by the program. This
29627 notification has 4 fields---@var{id}, @var{target-name},
29628 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
29629 opaque identifier of the library. For remote debugging case,
29630 @var{target-name} and @var{host-name} fields give the name of the
29631 library file on the target, and on the host respectively. For native
29632 debugging, both those fields have the same value. The
29633 @var{symbols-loaded} field is emitted only for backward compatibility
29634 and should not be relied on to convey any useful information. The
29635 @var{thread-group} field, if present, specifies the id of the thread
29636 group in whose context the library was loaded. If the field is
29637 absent, it means the library was loaded in the context of all present
29640 @item =library-unloaded,...
29641 Reports that a library was unloaded by the program. This notification
29642 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
29643 the same meaning as for the @code{=library-loaded} notification.
29644 The @var{thread-group} field, if present, specifies the id of the
29645 thread group in whose context the library was unloaded. If the field is
29646 absent, it means the library was unloaded in the context of all present
29649 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
29650 @itemx =traceframe-changed,end
29651 Reports that the trace frame was changed and its new number is
29652 @var{tfnum}. The number of the tracepoint associated with this trace
29653 frame is @var{tpnum}.
29655 @item =tsv-created,name=@var{name},initial=@var{initial}
29656 Reports that the new trace state variable @var{name} is created with
29657 initial value @var{initial}.
29659 @item =tsv-deleted,name=@var{name}
29660 @itemx =tsv-deleted
29661 Reports that the trace state variable @var{name} is deleted or all
29662 trace state variables are deleted.
29664 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
29665 Reports that the trace state variable @var{name} is modified with
29666 the initial value @var{initial}. The current value @var{current} of
29667 trace state variable is optional and is reported if the current
29668 value of trace state variable is known.
29670 @item =breakpoint-created,bkpt=@{...@}
29671 @itemx =breakpoint-modified,bkpt=@{...@}
29672 @itemx =breakpoint-deleted,id=@var{number}
29673 Reports that a breakpoint was created, modified, or deleted,
29674 respectively. Only user-visible breakpoints are reported to the MI
29677 The @var{bkpt} argument is of the same form as returned by the various
29678 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
29679 @var{number} is the ordinal number of the breakpoint.
29681 Note that if a breakpoint is emitted in the result record of a
29682 command, then it will not also be emitted in an async record.
29684 @item =record-started,thread-group="@var{id}"
29685 @itemx =record-stopped,thread-group="@var{id}"
29686 Execution log recording was either started or stopped on an
29687 inferior. The @var{id} is the @value{GDBN} identifier of the thread
29688 group corresponding to the affected inferior.
29690 @item =cmd-param-changed,param=@var{param},value=@var{value}
29691 Reports that a parameter of the command @code{set @var{param}} is
29692 changed to @var{value}. In the multi-word @code{set} command,
29693 the @var{param} is the whole parameter list to @code{set} command.
29694 For example, In command @code{set check type on}, @var{param}
29695 is @code{check type} and @var{value} is @code{on}.
29697 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
29698 Reports that bytes from @var{addr} to @var{data} + @var{len} were
29699 written in an inferior. The @var{id} is the identifier of the
29700 thread group corresponding to the affected inferior. The optional
29701 @code{type="code"} part is reported if the memory written to holds
29705 @node GDB/MI Breakpoint Information
29706 @subsection @sc{gdb/mi} Breakpoint Information
29708 When @value{GDBN} reports information about a breakpoint, a
29709 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
29714 The breakpoint number. For a breakpoint that represents one location
29715 of a multi-location breakpoint, this will be a dotted pair, like
29719 The type of the breakpoint. For ordinary breakpoints this will be
29720 @samp{breakpoint}, but many values are possible.
29723 If the type of the breakpoint is @samp{catchpoint}, then this
29724 indicates the exact type of catchpoint.
29727 This is the breakpoint disposition---either @samp{del}, meaning that
29728 the breakpoint will be deleted at the next stop, or @samp{keep},
29729 meaning that the breakpoint will not be deleted.
29732 This indicates whether the breakpoint is enabled, in which case the
29733 value is @samp{y}, or disabled, in which case the value is @samp{n}.
29734 Note that this is not the same as the field @code{enable}.
29737 The address of the breakpoint. This may be a hexidecimal number,
29738 giving the address; or the string @samp{<PENDING>}, for a pending
29739 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
29740 multiple locations. This field will not be present if no address can
29741 be determined. For example, a watchpoint does not have an address.
29744 If known, the function in which the breakpoint appears.
29745 If not known, this field is not present.
29748 The name of the source file which contains this function, if known.
29749 If not known, this field is not present.
29752 The full file name of the source file which contains this function, if
29753 known. If not known, this field is not present.
29756 The line number at which this breakpoint appears, if known.
29757 If not known, this field is not present.
29760 If the source file is not known, this field may be provided. If
29761 provided, this holds the address of the breakpoint, possibly followed
29765 If this breakpoint is pending, this field is present and holds the
29766 text used to set the breakpoint, as entered by the user.
29769 Where this breakpoint's condition is evaluated, either @samp{host} or
29773 If this is a thread-specific breakpoint, then this identifies the
29774 thread in which the breakpoint can trigger.
29777 If this breakpoint is restricted to a particular Ada task, then this
29778 field will hold the task identifier.
29781 If the breakpoint is conditional, this is the condition expression.
29784 The ignore count of the breakpoint.
29787 The enable count of the breakpoint.
29789 @item traceframe-usage
29792 @item static-tracepoint-marker-string-id
29793 For a static tracepoint, the name of the static tracepoint marker.
29796 For a masked watchpoint, this is the mask.
29799 A tracepoint's pass count.
29801 @item original-location
29802 The location of the breakpoint as originally specified by the user.
29803 This field is optional.
29806 The number of times the breakpoint has been hit.
29809 This field is only given for tracepoints. This is either @samp{y},
29810 meaning that the tracepoint is installed, or @samp{n}, meaning that it
29814 Some extra data, the exact contents of which are type-dependent.
29818 For example, here is what the output of @code{-break-insert}
29819 (@pxref{GDB/MI Breakpoint Commands}) might be:
29822 -> -break-insert main
29823 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29824 enabled="y",addr="0x08048564",func="main",file="myprog.c",
29825 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
29830 @node GDB/MI Frame Information
29831 @subsection @sc{gdb/mi} Frame Information
29833 Response from many MI commands includes an information about stack
29834 frame. This information is a tuple that may have the following
29839 The level of the stack frame. The innermost frame has the level of
29840 zero. This field is always present.
29843 The name of the function corresponding to the frame. This field may
29844 be absent if @value{GDBN} is unable to determine the function name.
29847 The code address for the frame. This field is always present.
29850 The name of the source files that correspond to the frame's code
29851 address. This field may be absent.
29854 The source line corresponding to the frames' code address. This field
29858 The name of the binary file (either executable or shared library) the
29859 corresponds to the frame's code address. This field may be absent.
29863 @node GDB/MI Thread Information
29864 @subsection @sc{gdb/mi} Thread Information
29866 Whenever @value{GDBN} has to report an information about a thread, it
29867 uses a tuple with the following fields:
29871 The numeric id assigned to the thread by @value{GDBN}. This field is
29875 Target-specific string identifying the thread. This field is always present.
29878 Additional information about the thread provided by the target.
29879 It is supposed to be human-readable and not interpreted by the
29880 frontend. This field is optional.
29883 Either @samp{stopped} or @samp{running}, depending on whether the
29884 thread is presently running. This field is always present.
29887 The value of this field is an integer number of the processor core the
29888 thread was last seen on. This field is optional.
29891 @node GDB/MI Ada Exception Information
29892 @subsection @sc{gdb/mi} Ada Exception Information
29894 Whenever a @code{*stopped} record is emitted because the program
29895 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
29896 @value{GDBN} provides the name of the exception that was raised via
29897 the @code{exception-name} field.
29899 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29900 @node GDB/MI Simple Examples
29901 @section Simple Examples of @sc{gdb/mi} Interaction
29902 @cindex @sc{gdb/mi}, simple examples
29904 This subsection presents several simple examples of interaction using
29905 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
29906 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
29907 the output received from @sc{gdb/mi}.
29909 Note the line breaks shown in the examples are here only for
29910 readability, they don't appear in the real output.
29912 @subheading Setting a Breakpoint
29914 Setting a breakpoint generates synchronous output which contains detailed
29915 information of the breakpoint.
29918 -> -break-insert main
29919 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29920 enabled="y",addr="0x08048564",func="main",file="myprog.c",
29921 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
29926 @subheading Program Execution
29928 Program execution generates asynchronous records and MI gives the
29929 reason that execution stopped.
29935 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
29936 frame=@{addr="0x08048564",func="main",
29937 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
29938 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
29943 <- *stopped,reason="exited-normally"
29947 @subheading Quitting @value{GDBN}
29949 Quitting @value{GDBN} just prints the result class @samp{^exit}.
29957 Please note that @samp{^exit} is printed immediately, but it might
29958 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
29959 performs necessary cleanups, including killing programs being debugged
29960 or disconnecting from debug hardware, so the frontend should wait till
29961 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
29962 fails to exit in reasonable time.
29964 @subheading A Bad Command
29966 Here's what happens if you pass a non-existent command:
29970 <- ^error,msg="Undefined MI command: rubbish"
29975 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29976 @node GDB/MI Command Description Format
29977 @section @sc{gdb/mi} Command Description Format
29979 The remaining sections describe blocks of commands. Each block of
29980 commands is laid out in a fashion similar to this section.
29982 @subheading Motivation
29984 The motivation for this collection of commands.
29986 @subheading Introduction
29988 A brief introduction to this collection of commands as a whole.
29990 @subheading Commands
29992 For each command in the block, the following is described:
29994 @subsubheading Synopsis
29997 -command @var{args}@dots{}
30000 @subsubheading Result
30002 @subsubheading @value{GDBN} Command
30004 The corresponding @value{GDBN} CLI command(s), if any.
30006 @subsubheading Example
30008 Example(s) formatted for readability. Some of the described commands have
30009 not been implemented yet and these are labeled N.A.@: (not available).
30012 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30013 @node GDB/MI Breakpoint Commands
30014 @section @sc{gdb/mi} Breakpoint Commands
30016 @cindex breakpoint commands for @sc{gdb/mi}
30017 @cindex @sc{gdb/mi}, breakpoint commands
30018 This section documents @sc{gdb/mi} commands for manipulating
30021 @subheading The @code{-break-after} Command
30022 @findex -break-after
30024 @subsubheading Synopsis
30027 -break-after @var{number} @var{count}
30030 The breakpoint number @var{number} is not in effect until it has been
30031 hit @var{count} times. To see how this is reflected in the output of
30032 the @samp{-break-list} command, see the description of the
30033 @samp{-break-list} command below.
30035 @subsubheading @value{GDBN} Command
30037 The corresponding @value{GDBN} command is @samp{ignore}.
30039 @subsubheading Example
30044 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
30045 enabled="y",addr="0x000100d0",func="main",file="hello.c",
30046 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
30054 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30055 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30056 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30057 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30058 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30059 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30060 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30061 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30062 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30063 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
30068 @subheading The @code{-break-catch} Command
30069 @findex -break-catch
30072 @subheading The @code{-break-commands} Command
30073 @findex -break-commands
30075 @subsubheading Synopsis
30078 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
30081 Specifies the CLI commands that should be executed when breakpoint
30082 @var{number} is hit. The parameters @var{command1} to @var{commandN}
30083 are the commands. If no command is specified, any previously-set
30084 commands are cleared. @xref{Break Commands}. Typical use of this
30085 functionality is tracing a program, that is, printing of values of
30086 some variables whenever breakpoint is hit and then continuing.
30088 @subsubheading @value{GDBN} Command
30090 The corresponding @value{GDBN} command is @samp{commands}.
30092 @subsubheading Example
30097 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
30098 enabled="y",addr="0x000100d0",func="main",file="hello.c",
30099 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
30102 -break-commands 1 "print v" "continue"
30107 @subheading The @code{-break-condition} Command
30108 @findex -break-condition
30110 @subsubheading Synopsis
30113 -break-condition @var{number} @var{expr}
30116 Breakpoint @var{number} will stop the program only if the condition in
30117 @var{expr} is true. The condition becomes part of the
30118 @samp{-break-list} output (see the description of the @samp{-break-list}
30121 @subsubheading @value{GDBN} Command
30123 The corresponding @value{GDBN} command is @samp{condition}.
30125 @subsubheading Example
30129 -break-condition 1 1
30133 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30134 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30135 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30136 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30137 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30138 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30139 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30140 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30141 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30142 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
30146 @subheading The @code{-break-delete} Command
30147 @findex -break-delete
30149 @subsubheading Synopsis
30152 -break-delete ( @var{breakpoint} )+
30155 Delete the breakpoint(s) whose number(s) are specified in the argument
30156 list. This is obviously reflected in the breakpoint list.
30158 @subsubheading @value{GDBN} Command
30160 The corresponding @value{GDBN} command is @samp{delete}.
30162 @subsubheading Example
30170 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
30171 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30172 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30173 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30174 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30175 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30176 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30181 @subheading The @code{-break-disable} Command
30182 @findex -break-disable
30184 @subsubheading Synopsis
30187 -break-disable ( @var{breakpoint} )+
30190 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
30191 break list is now set to @samp{n} for the named @var{breakpoint}(s).
30193 @subsubheading @value{GDBN} Command
30195 The corresponding @value{GDBN} command is @samp{disable}.
30197 @subsubheading Example
30205 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30206 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30207 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30208 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30209 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30210 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30211 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30212 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
30213 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30214 line="5",thread-groups=["i1"],times="0"@}]@}
30218 @subheading The @code{-break-enable} Command
30219 @findex -break-enable
30221 @subsubheading Synopsis
30224 -break-enable ( @var{breakpoint} )+
30227 Enable (previously disabled) @var{breakpoint}(s).
30229 @subsubheading @value{GDBN} Command
30231 The corresponding @value{GDBN} command is @samp{enable}.
30233 @subsubheading Example
30241 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30242 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30243 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30244 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30245 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30246 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30247 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30248 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
30249 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30250 line="5",thread-groups=["i1"],times="0"@}]@}
30254 @subheading The @code{-break-info} Command
30255 @findex -break-info
30257 @subsubheading Synopsis
30260 -break-info @var{breakpoint}
30264 Get information about a single breakpoint.
30266 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
30267 Information}, for details on the format of each breakpoint in the
30270 @subsubheading @value{GDBN} Command
30272 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
30274 @subsubheading Example
30277 @subheading The @code{-break-insert} Command
30278 @findex -break-insert
30280 @subsubheading Synopsis
30283 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
30284 [ -c @var{condition} ] [ -i @var{ignore-count} ]
30285 [ -p @var{thread-id} ] [ @var{location} ]
30289 If specified, @var{location}, can be one of:
30296 @item filename:linenum
30297 @item filename:function
30301 The possible optional parameters of this command are:
30305 Insert a temporary breakpoint.
30307 Insert a hardware breakpoint.
30309 If @var{location} cannot be parsed (for example if it
30310 refers to unknown files or functions), create a pending
30311 breakpoint. Without this flag, @value{GDBN} will report
30312 an error, and won't create a breakpoint, if @var{location}
30315 Create a disabled breakpoint.
30317 Create a tracepoint. @xref{Tracepoints}. When this parameter
30318 is used together with @samp{-h}, a fast tracepoint is created.
30319 @item -c @var{condition}
30320 Make the breakpoint conditional on @var{condition}.
30321 @item -i @var{ignore-count}
30322 Initialize the @var{ignore-count}.
30323 @item -p @var{thread-id}
30324 Restrict the breakpoint to the specified @var{thread-id}.
30327 @subsubheading Result
30329 @xref{GDB/MI Breakpoint Information}, for details on the format of the
30330 resulting breakpoint.
30332 Note: this format is open to change.
30333 @c An out-of-band breakpoint instead of part of the result?
30335 @subsubheading @value{GDBN} Command
30337 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
30338 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
30340 @subsubheading Example
30345 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
30346 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
30349 -break-insert -t foo
30350 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
30351 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
30355 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30356 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30357 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30358 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30359 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30360 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30361 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30362 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30363 addr="0x0001072c", func="main",file="recursive2.c",
30364 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
30366 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
30367 addr="0x00010774",func="foo",file="recursive2.c",
30368 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
30371 @c -break-insert -r foo.*
30372 @c ~int foo(int, int);
30373 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
30374 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
30379 @subheading The @code{-dprintf-insert} Command
30380 @findex -dprintf-insert
30382 @subsubheading Synopsis
30385 -dprintf-insert [ -t ] [ -f ] [ -d ]
30386 [ -c @var{condition} ] [ -i @var{ignore-count} ]
30387 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
30392 If specified, @var{location}, can be one of:
30395 @item @var{function}
30398 @c @item @var{linenum}
30399 @item @var{filename}:@var{linenum}
30400 @item @var{filename}:function
30401 @item *@var{address}
30404 The possible optional parameters of this command are:
30408 Insert a temporary breakpoint.
30410 If @var{location} cannot be parsed (for example, if it
30411 refers to unknown files or functions), create a pending
30412 breakpoint. Without this flag, @value{GDBN} will report
30413 an error, and won't create a breakpoint, if @var{location}
30416 Create a disabled breakpoint.
30417 @item -c @var{condition}
30418 Make the breakpoint conditional on @var{condition}.
30419 @item -i @var{ignore-count}
30420 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
30421 to @var{ignore-count}.
30422 @item -p @var{thread-id}
30423 Restrict the breakpoint to the specified @var{thread-id}.
30426 @subsubheading Result
30428 @xref{GDB/MI Breakpoint Information}, for details on the format of the
30429 resulting breakpoint.
30431 @c An out-of-band breakpoint instead of part of the result?
30433 @subsubheading @value{GDBN} Command
30435 The corresponding @value{GDBN} command is @samp{dprintf}.
30437 @subsubheading Example
30441 4-dprintf-insert foo "At foo entry\n"
30442 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
30443 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
30444 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
30445 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
30446 original-location="foo"@}
30448 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
30449 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
30450 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
30451 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
30452 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
30453 original-location="mi-dprintf.c:26"@}
30457 @subheading The @code{-break-list} Command
30458 @findex -break-list
30460 @subsubheading Synopsis
30466 Displays the list of inserted breakpoints, showing the following fields:
30470 number of the breakpoint
30472 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
30474 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
30477 is the breakpoint enabled or no: @samp{y} or @samp{n}
30479 memory location at which the breakpoint is set
30481 logical location of the breakpoint, expressed by function name, file
30483 @item Thread-groups
30484 list of thread groups to which this breakpoint applies
30486 number of times the breakpoint has been hit
30489 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
30490 @code{body} field is an empty list.
30492 @subsubheading @value{GDBN} Command
30494 The corresponding @value{GDBN} command is @samp{info break}.
30496 @subsubheading Example
30501 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30502 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30503 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30504 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30505 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30506 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30507 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30508 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30509 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
30511 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
30512 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
30513 line="13",thread-groups=["i1"],times="0"@}]@}
30517 Here's an example of the result when there are no breakpoints:
30522 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
30523 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30524 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30525 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30526 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30527 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30528 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30533 @subheading The @code{-break-passcount} Command
30534 @findex -break-passcount
30536 @subsubheading Synopsis
30539 -break-passcount @var{tracepoint-number} @var{passcount}
30542 Set the passcount for tracepoint @var{tracepoint-number} to
30543 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
30544 is not a tracepoint, error is emitted. This corresponds to CLI
30545 command @samp{passcount}.
30547 @subheading The @code{-break-watch} Command
30548 @findex -break-watch
30550 @subsubheading Synopsis
30553 -break-watch [ -a | -r ]
30556 Create a watchpoint. With the @samp{-a} option it will create an
30557 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
30558 read from or on a write to the memory location. With the @samp{-r}
30559 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
30560 trigger only when the memory location is accessed for reading. Without
30561 either of the options, the watchpoint created is a regular watchpoint,
30562 i.e., it will trigger when the memory location is accessed for writing.
30563 @xref{Set Watchpoints, , Setting Watchpoints}.
30565 Note that @samp{-break-list} will report a single list of watchpoints and
30566 breakpoints inserted.
30568 @subsubheading @value{GDBN} Command
30570 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
30573 @subsubheading Example
30575 Setting a watchpoint on a variable in the @code{main} function:
30580 ^done,wpt=@{number="2",exp="x"@}
30585 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
30586 value=@{old="-268439212",new="55"@},
30587 frame=@{func="main",args=[],file="recursive2.c",
30588 fullname="/home/foo/bar/recursive2.c",line="5"@}
30592 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
30593 the program execution twice: first for the variable changing value, then
30594 for the watchpoint going out of scope.
30599 ^done,wpt=@{number="5",exp="C"@}
30604 *stopped,reason="watchpoint-trigger",
30605 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
30606 frame=@{func="callee4",args=[],
30607 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30608 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
30613 *stopped,reason="watchpoint-scope",wpnum="5",
30614 frame=@{func="callee3",args=[@{name="strarg",
30615 value="0x11940 \"A string argument.\""@}],
30616 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30617 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
30621 Listing breakpoints and watchpoints, at different points in the program
30622 execution. Note that once the watchpoint goes out of scope, it is
30628 ^done,wpt=@{number="2",exp="C"@}
30631 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30632 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30633 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30634 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30635 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30636 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30637 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30638 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30639 addr="0x00010734",func="callee4",
30640 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30641 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
30643 bkpt=@{number="2",type="watchpoint",disp="keep",
30644 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
30649 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
30650 value=@{old="-276895068",new="3"@},
30651 frame=@{func="callee4",args=[],
30652 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30653 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
30656 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30657 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30658 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30659 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30660 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30661 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30662 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30663 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30664 addr="0x00010734",func="callee4",
30665 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30666 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
30668 bkpt=@{number="2",type="watchpoint",disp="keep",
30669 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
30673 ^done,reason="watchpoint-scope",wpnum="2",
30674 frame=@{func="callee3",args=[@{name="strarg",
30675 value="0x11940 \"A string argument.\""@}],
30676 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30677 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
30680 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30681 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30682 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30683 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30684 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30685 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30686 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30687 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30688 addr="0x00010734",func="callee4",
30689 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30690 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
30691 thread-groups=["i1"],times="1"@}]@}
30696 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30697 @node GDB/MI Catchpoint Commands
30698 @section @sc{gdb/mi} Catchpoint Commands
30700 This section documents @sc{gdb/mi} commands for manipulating
30704 * Shared Library GDB/MI Catchpoint Commands::
30705 * Ada Exception GDB/MI Catchpoint Commands::
30708 @node Shared Library GDB/MI Catchpoint Commands
30709 @subsection Shared Library @sc{gdb/mi} Catchpoints
30711 @subheading The @code{-catch-load} Command
30712 @findex -catch-load
30714 @subsubheading Synopsis
30717 -catch-load [ -t ] [ -d ] @var{regexp}
30720 Add a catchpoint for library load events. If the @samp{-t} option is used,
30721 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
30722 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
30723 in a disabled state. The @samp{regexp} argument is a regular
30724 expression used to match the name of the loaded library.
30727 @subsubheading @value{GDBN} Command
30729 The corresponding @value{GDBN} command is @samp{catch load}.
30731 @subsubheading Example
30734 -catch-load -t foo.so
30735 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
30736 what="load of library matching foo.so",catch-type="load",times="0"@}
30741 @subheading The @code{-catch-unload} Command
30742 @findex -catch-unload
30744 @subsubheading Synopsis
30747 -catch-unload [ -t ] [ -d ] @var{regexp}
30750 Add a catchpoint for library unload events. If the @samp{-t} option is
30751 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
30752 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
30753 created in a disabled state. The @samp{regexp} argument is a regular
30754 expression used to match the name of the unloaded library.
30756 @subsubheading @value{GDBN} Command
30758 The corresponding @value{GDBN} command is @samp{catch unload}.
30760 @subsubheading Example
30763 -catch-unload -d bar.so
30764 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
30765 what="load of library matching bar.so",catch-type="unload",times="0"@}
30769 @node Ada Exception GDB/MI Catchpoint Commands
30770 @subsection Ada Exception @sc{gdb/mi} Catchpoints
30772 The following @sc{gdb/mi} commands can be used to create catchpoints
30773 that stop the execution when Ada exceptions are being raised.
30775 @subheading The @code{-catch-assert} Command
30776 @findex -catch-assert
30778 @subsubheading Synopsis
30781 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
30784 Add a catchpoint for failed Ada assertions.
30786 The possible optional parameters for this command are:
30789 @item -c @var{condition}
30790 Make the catchpoint conditional on @var{condition}.
30792 Create a disabled catchpoint.
30794 Create a temporary catchpoint.
30797 @subsubheading @value{GDBN} Command
30799 The corresponding @value{GDBN} command is @samp{catch assert}.
30801 @subsubheading Example
30805 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
30806 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
30807 thread-groups=["i1"],times="0",
30808 original-location="__gnat_debug_raise_assert_failure"@}
30812 @subheading The @code{-catch-exception} Command
30813 @findex -catch-exception
30815 @subsubheading Synopsis
30818 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
30822 Add a catchpoint stopping when Ada exceptions are raised.
30823 By default, the command stops the program when any Ada exception
30824 gets raised. But it is also possible, by using some of the
30825 optional parameters described below, to create more selective
30828 The possible optional parameters for this command are:
30831 @item -c @var{condition}
30832 Make the catchpoint conditional on @var{condition}.
30834 Create a disabled catchpoint.
30835 @item -e @var{exception-name}
30836 Only stop when @var{exception-name} is raised. This option cannot
30837 be used combined with @samp{-u}.
30839 Create a temporary catchpoint.
30841 Stop only when an unhandled exception gets raised. This option
30842 cannot be used combined with @samp{-e}.
30845 @subsubheading @value{GDBN} Command
30847 The corresponding @value{GDBN} commands are @samp{catch exception}
30848 and @samp{catch exception unhandled}.
30850 @subsubheading Example
30853 -catch-exception -e Program_Error
30854 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
30855 enabled="y",addr="0x0000000000404874",
30856 what="`Program_Error' Ada exception", thread-groups=["i1"],
30857 times="0",original-location="__gnat_debug_raise_exception"@}
30861 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30862 @node GDB/MI Program Context
30863 @section @sc{gdb/mi} Program Context
30865 @subheading The @code{-exec-arguments} Command
30866 @findex -exec-arguments
30869 @subsubheading Synopsis
30872 -exec-arguments @var{args}
30875 Set the inferior program arguments, to be used in the next
30878 @subsubheading @value{GDBN} Command
30880 The corresponding @value{GDBN} command is @samp{set args}.
30882 @subsubheading Example
30886 -exec-arguments -v word
30893 @subheading The @code{-exec-show-arguments} Command
30894 @findex -exec-show-arguments
30896 @subsubheading Synopsis
30899 -exec-show-arguments
30902 Print the arguments of the program.
30904 @subsubheading @value{GDBN} Command
30906 The corresponding @value{GDBN} command is @samp{show args}.
30908 @subsubheading Example
30913 @subheading The @code{-environment-cd} Command
30914 @findex -environment-cd
30916 @subsubheading Synopsis
30919 -environment-cd @var{pathdir}
30922 Set @value{GDBN}'s working directory.
30924 @subsubheading @value{GDBN} Command
30926 The corresponding @value{GDBN} command is @samp{cd}.
30928 @subsubheading Example
30932 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
30938 @subheading The @code{-environment-directory} Command
30939 @findex -environment-directory
30941 @subsubheading Synopsis
30944 -environment-directory [ -r ] [ @var{pathdir} ]+
30947 Add directories @var{pathdir} to beginning of search path for source files.
30948 If the @samp{-r} option is used, the search path is reset to the default
30949 search path. If directories @var{pathdir} are supplied in addition to the
30950 @samp{-r} option, the search path is first reset and then addition
30952 Multiple directories may be specified, separated by blanks. Specifying
30953 multiple directories in a single command
30954 results in the directories added to the beginning of the
30955 search path in the same order they were presented in the command.
30956 If blanks are needed as
30957 part of a directory name, double-quotes should be used around
30958 the name. In the command output, the path will show up separated
30959 by the system directory-separator character. The directory-separator
30960 character must not be used
30961 in any directory name.
30962 If no directories are specified, the current search path is displayed.
30964 @subsubheading @value{GDBN} Command
30966 The corresponding @value{GDBN} command is @samp{dir}.
30968 @subsubheading Example
30972 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
30973 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
30975 -environment-directory ""
30976 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
30978 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
30979 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
30981 -environment-directory -r
30982 ^done,source-path="$cdir:$cwd"
30987 @subheading The @code{-environment-path} Command
30988 @findex -environment-path
30990 @subsubheading Synopsis
30993 -environment-path [ -r ] [ @var{pathdir} ]+
30996 Add directories @var{pathdir} to beginning of search path for object files.
30997 If the @samp{-r} option is used, the search path is reset to the original
30998 search path that existed at gdb start-up. If directories @var{pathdir} are
30999 supplied in addition to the
31000 @samp{-r} option, the search path is first reset and then addition
31002 Multiple directories may be specified, separated by blanks. Specifying
31003 multiple directories in a single command
31004 results in the directories added to the beginning of the
31005 search path in the same order they were presented in the command.
31006 If blanks are needed as
31007 part of a directory name, double-quotes should be used around
31008 the name. In the command output, the path will show up separated
31009 by the system directory-separator character. The directory-separator
31010 character must not be used
31011 in any directory name.
31012 If no directories are specified, the current path is displayed.
31015 @subsubheading @value{GDBN} Command
31017 The corresponding @value{GDBN} command is @samp{path}.
31019 @subsubheading Example
31024 ^done,path="/usr/bin"
31026 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
31027 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
31029 -environment-path -r /usr/local/bin
31030 ^done,path="/usr/local/bin:/usr/bin"
31035 @subheading The @code{-environment-pwd} Command
31036 @findex -environment-pwd
31038 @subsubheading Synopsis
31044 Show the current working directory.
31046 @subsubheading @value{GDBN} Command
31048 The corresponding @value{GDBN} command is @samp{pwd}.
31050 @subsubheading Example
31055 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
31059 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31060 @node GDB/MI Thread Commands
31061 @section @sc{gdb/mi} Thread Commands
31064 @subheading The @code{-thread-info} Command
31065 @findex -thread-info
31067 @subsubheading Synopsis
31070 -thread-info [ @var{thread-id} ]
31073 Reports information about either a specific thread, if
31074 the @var{thread-id} parameter is present, or about all
31075 threads. When printing information about all threads,
31076 also reports the current thread.
31078 @subsubheading @value{GDBN} Command
31080 The @samp{info thread} command prints the same information
31083 @subsubheading Result
31085 The result is a list of threads. The following attributes are
31086 defined for a given thread:
31090 This field exists only for the current thread. It has the value @samp{*}.
31093 The identifier that @value{GDBN} uses to refer to the thread.
31096 The identifier that the target uses to refer to the thread.
31099 Extra information about the thread, in a target-specific format. This
31103 The name of the thread. If the user specified a name using the
31104 @code{thread name} command, then this name is given. Otherwise, if
31105 @value{GDBN} can extract the thread name from the target, then that
31106 name is given. If @value{GDBN} cannot find the thread name, then this
31110 The stack frame currently executing in the thread.
31113 The thread's state. The @samp{state} field may have the following
31118 The thread is stopped. Frame information is available for stopped
31122 The thread is running. There's no frame information for running
31128 If @value{GDBN} can find the CPU core on which this thread is running,
31129 then this field is the core identifier. This field is optional.
31133 @subsubheading Example
31138 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
31139 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
31140 args=[]@},state="running"@},
31141 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
31142 frame=@{level="0",addr="0x0804891f",func="foo",
31143 args=[@{name="i",value="10"@}],
31144 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
31145 state="running"@}],
31146 current-thread-id="1"
31150 @subheading The @code{-thread-list-ids} Command
31151 @findex -thread-list-ids
31153 @subsubheading Synopsis
31159 Produces a list of the currently known @value{GDBN} thread ids. At the
31160 end of the list it also prints the total number of such threads.
31162 This command is retained for historical reasons, the
31163 @code{-thread-info} command should be used instead.
31165 @subsubheading @value{GDBN} Command
31167 Part of @samp{info threads} supplies the same information.
31169 @subsubheading Example
31174 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
31175 current-thread-id="1",number-of-threads="3"
31180 @subheading The @code{-thread-select} Command
31181 @findex -thread-select
31183 @subsubheading Synopsis
31186 -thread-select @var{threadnum}
31189 Make @var{threadnum} the current thread. It prints the number of the new
31190 current thread, and the topmost frame for that thread.
31192 This command is deprecated in favor of explicitly using the
31193 @samp{--thread} option to each command.
31195 @subsubheading @value{GDBN} Command
31197 The corresponding @value{GDBN} command is @samp{thread}.
31199 @subsubheading Example
31206 *stopped,reason="end-stepping-range",thread-id="2",line="187",
31207 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
31211 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
31212 number-of-threads="3"
31215 ^done,new-thread-id="3",
31216 frame=@{level="0",func="vprintf",
31217 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
31218 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
31222 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31223 @node GDB/MI Ada Tasking Commands
31224 @section @sc{gdb/mi} Ada Tasking Commands
31226 @subheading The @code{-ada-task-info} Command
31227 @findex -ada-task-info
31229 @subsubheading Synopsis
31232 -ada-task-info [ @var{task-id} ]
31235 Reports information about either a specific Ada task, if the
31236 @var{task-id} parameter is present, or about all Ada tasks.
31238 @subsubheading @value{GDBN} Command
31240 The @samp{info tasks} command prints the same information
31241 about all Ada tasks (@pxref{Ada Tasks}).
31243 @subsubheading Result
31245 The result is a table of Ada tasks. The following columns are
31246 defined for each Ada task:
31250 This field exists only for the current thread. It has the value @samp{*}.
31253 The identifier that @value{GDBN} uses to refer to the Ada task.
31256 The identifier that the target uses to refer to the Ada task.
31259 The identifier of the thread corresponding to the Ada task.
31261 This field should always exist, as Ada tasks are always implemented
31262 on top of a thread. But if @value{GDBN} cannot find this corresponding
31263 thread for any reason, the field is omitted.
31266 This field exists only when the task was created by another task.
31267 In this case, it provides the ID of the parent task.
31270 The base priority of the task.
31273 The current state of the task. For a detailed description of the
31274 possible states, see @ref{Ada Tasks}.
31277 The name of the task.
31281 @subsubheading Example
31285 ^done,tasks=@{nr_rows="3",nr_cols="8",
31286 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
31287 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
31288 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
31289 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
31290 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
31291 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
31292 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
31293 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
31294 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
31295 state="Child Termination Wait",name="main_task"@}]@}
31299 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31300 @node GDB/MI Program Execution
31301 @section @sc{gdb/mi} Program Execution
31303 These are the asynchronous commands which generate the out-of-band
31304 record @samp{*stopped}. Currently @value{GDBN} only really executes
31305 asynchronously with remote targets and this interaction is mimicked in
31308 @subheading The @code{-exec-continue} Command
31309 @findex -exec-continue
31311 @subsubheading Synopsis
31314 -exec-continue [--reverse] [--all|--thread-group N]
31317 Resumes the execution of the inferior program, which will continue
31318 to execute until it reaches a debugger stop event. If the
31319 @samp{--reverse} option is specified, execution resumes in reverse until
31320 it reaches a stop event. Stop events may include
31323 breakpoints or watchpoints
31325 signals or exceptions
31327 the end of the process (or its beginning under @samp{--reverse})
31329 the end or beginning of a replay log if one is being used.
31331 In all-stop mode (@pxref{All-Stop
31332 Mode}), may resume only one thread, or all threads, depending on the
31333 value of the @samp{scheduler-locking} variable. If @samp{--all} is
31334 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
31335 ignored in all-stop mode. If the @samp{--thread-group} options is
31336 specified, then all threads in that thread group are resumed.
31338 @subsubheading @value{GDBN} Command
31340 The corresponding @value{GDBN} corresponding is @samp{continue}.
31342 @subsubheading Example
31349 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
31350 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
31356 @subheading The @code{-exec-finish} Command
31357 @findex -exec-finish
31359 @subsubheading Synopsis
31362 -exec-finish [--reverse]
31365 Resumes the execution of the inferior program until the current
31366 function is exited. Displays the results returned by the function.
31367 If the @samp{--reverse} option is specified, resumes the reverse
31368 execution of the inferior program until the point where current
31369 function was called.
31371 @subsubheading @value{GDBN} Command
31373 The corresponding @value{GDBN} command is @samp{finish}.
31375 @subsubheading Example
31377 Function returning @code{void}.
31384 *stopped,reason="function-finished",frame=@{func="main",args=[],
31385 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
31389 Function returning other than @code{void}. The name of the internal
31390 @value{GDBN} variable storing the result is printed, together with the
31397 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
31398 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
31399 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31400 gdb-result-var="$1",return-value="0"
31405 @subheading The @code{-exec-interrupt} Command
31406 @findex -exec-interrupt
31408 @subsubheading Synopsis
31411 -exec-interrupt [--all|--thread-group N]
31414 Interrupts the background execution of the target. Note how the token
31415 associated with the stop message is the one for the execution command
31416 that has been interrupted. The token for the interrupt itself only
31417 appears in the @samp{^done} output. If the user is trying to
31418 interrupt a non-running program, an error message will be printed.
31420 Note that when asynchronous execution is enabled, this command is
31421 asynchronous just like other execution commands. That is, first the
31422 @samp{^done} response will be printed, and the target stop will be
31423 reported after that using the @samp{*stopped} notification.
31425 In non-stop mode, only the context thread is interrupted by default.
31426 All threads (in all inferiors) will be interrupted if the
31427 @samp{--all} option is specified. If the @samp{--thread-group}
31428 option is specified, all threads in that group will be interrupted.
31430 @subsubheading @value{GDBN} Command
31432 The corresponding @value{GDBN} command is @samp{interrupt}.
31434 @subsubheading Example
31445 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
31446 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
31447 fullname="/home/foo/bar/try.c",line="13"@}
31452 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
31456 @subheading The @code{-exec-jump} Command
31459 @subsubheading Synopsis
31462 -exec-jump @var{location}
31465 Resumes execution of the inferior program at the location specified by
31466 parameter. @xref{Specify Location}, for a description of the
31467 different forms of @var{location}.
31469 @subsubheading @value{GDBN} Command
31471 The corresponding @value{GDBN} command is @samp{jump}.
31473 @subsubheading Example
31476 -exec-jump foo.c:10
31477 *running,thread-id="all"
31482 @subheading The @code{-exec-next} Command
31485 @subsubheading Synopsis
31488 -exec-next [--reverse]
31491 Resumes execution of the inferior program, stopping when the beginning
31492 of the next source line is reached.
31494 If the @samp{--reverse} option is specified, resumes reverse execution
31495 of the inferior program, stopping at the beginning of the previous
31496 source line. If you issue this command on the first line of a
31497 function, it will take you back to the caller of that function, to the
31498 source line where the function was called.
31501 @subsubheading @value{GDBN} Command
31503 The corresponding @value{GDBN} command is @samp{next}.
31505 @subsubheading Example
31511 *stopped,reason="end-stepping-range",line="8",file="hello.c"
31516 @subheading The @code{-exec-next-instruction} Command
31517 @findex -exec-next-instruction
31519 @subsubheading Synopsis
31522 -exec-next-instruction [--reverse]
31525 Executes one machine instruction. If the instruction is a function
31526 call, continues until the function returns. If the program stops at an
31527 instruction in the middle of a source line, the address will be
31530 If the @samp{--reverse} option is specified, resumes reverse execution
31531 of the inferior program, stopping at the previous instruction. If the
31532 previously executed instruction was a return from another function,
31533 it will continue to execute in reverse until the call to that function
31534 (from the current stack frame) is reached.
31536 @subsubheading @value{GDBN} Command
31538 The corresponding @value{GDBN} command is @samp{nexti}.
31540 @subsubheading Example
31544 -exec-next-instruction
31548 *stopped,reason="end-stepping-range",
31549 addr="0x000100d4",line="5",file="hello.c"
31554 @subheading The @code{-exec-return} Command
31555 @findex -exec-return
31557 @subsubheading Synopsis
31563 Makes current function return immediately. Doesn't execute the inferior.
31564 Displays the new current frame.
31566 @subsubheading @value{GDBN} Command
31568 The corresponding @value{GDBN} command is @samp{return}.
31570 @subsubheading Example
31574 200-break-insert callee4
31575 200^done,bkpt=@{number="1",addr="0x00010734",
31576 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
31581 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
31582 frame=@{func="callee4",args=[],
31583 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31584 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
31590 111^done,frame=@{level="0",func="callee3",
31591 args=[@{name="strarg",
31592 value="0x11940 \"A string argument.\""@}],
31593 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31594 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
31599 @subheading The @code{-exec-run} Command
31602 @subsubheading Synopsis
31605 -exec-run [ --all | --thread-group N ] [ --start ]
31608 Starts execution of the inferior from the beginning. The inferior
31609 executes until either a breakpoint is encountered or the program
31610 exits. In the latter case the output will include an exit code, if
31611 the program has exited exceptionally.
31613 When neither the @samp{--all} nor the @samp{--thread-group} option
31614 is specified, the current inferior is started. If the
31615 @samp{--thread-group} option is specified, it should refer to a thread
31616 group of type @samp{process}, and that thread group will be started.
31617 If the @samp{--all} option is specified, then all inferiors will be started.
31619 Using the @samp{--start} option instructs the debugger to stop
31620 the execution at the start of the inferior's main subprogram,
31621 following the same behavior as the @code{start} command
31622 (@pxref{Starting}).
31624 @subsubheading @value{GDBN} Command
31626 The corresponding @value{GDBN} command is @samp{run}.
31628 @subsubheading Examples
31633 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
31638 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
31639 frame=@{func="main",args=[],file="recursive2.c",
31640 fullname="/home/foo/bar/recursive2.c",line="4"@}
31645 Program exited normally:
31653 *stopped,reason="exited-normally"
31658 Program exited exceptionally:
31666 *stopped,reason="exited",exit-code="01"
31670 Another way the program can terminate is if it receives a signal such as
31671 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
31675 *stopped,reason="exited-signalled",signal-name="SIGINT",
31676 signal-meaning="Interrupt"
31680 @c @subheading -exec-signal
31683 @subheading The @code{-exec-step} Command
31686 @subsubheading Synopsis
31689 -exec-step [--reverse]
31692 Resumes execution of the inferior program, stopping when the beginning
31693 of the next source line is reached, if the next source line is not a
31694 function call. If it is, stop at the first instruction of the called
31695 function. If the @samp{--reverse} option is specified, resumes reverse
31696 execution of the inferior program, stopping at the beginning of the
31697 previously executed source line.
31699 @subsubheading @value{GDBN} Command
31701 The corresponding @value{GDBN} command is @samp{step}.
31703 @subsubheading Example
31705 Stepping into a function:
31711 *stopped,reason="end-stepping-range",
31712 frame=@{func="foo",args=[@{name="a",value="10"@},
31713 @{name="b",value="0"@}],file="recursive2.c",
31714 fullname="/home/foo/bar/recursive2.c",line="11"@}
31724 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
31729 @subheading The @code{-exec-step-instruction} Command
31730 @findex -exec-step-instruction
31732 @subsubheading Synopsis
31735 -exec-step-instruction [--reverse]
31738 Resumes the inferior which executes one machine instruction. If the
31739 @samp{--reverse} option is specified, resumes reverse execution of the
31740 inferior program, stopping at the previously executed instruction.
31741 The output, once @value{GDBN} has stopped, will vary depending on
31742 whether we have stopped in the middle of a source line or not. In the
31743 former case, the address at which the program stopped will be printed
31746 @subsubheading @value{GDBN} Command
31748 The corresponding @value{GDBN} command is @samp{stepi}.
31750 @subsubheading Example
31754 -exec-step-instruction
31758 *stopped,reason="end-stepping-range",
31759 frame=@{func="foo",args=[],file="try.c",
31760 fullname="/home/foo/bar/try.c",line="10"@}
31762 -exec-step-instruction
31766 *stopped,reason="end-stepping-range",
31767 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
31768 fullname="/home/foo/bar/try.c",line="10"@}
31773 @subheading The @code{-exec-until} Command
31774 @findex -exec-until
31776 @subsubheading Synopsis
31779 -exec-until [ @var{location} ]
31782 Executes the inferior until the @var{location} specified in the
31783 argument is reached. If there is no argument, the inferior executes
31784 until a source line greater than the current one is reached. The
31785 reason for stopping in this case will be @samp{location-reached}.
31787 @subsubheading @value{GDBN} Command
31789 The corresponding @value{GDBN} command is @samp{until}.
31791 @subsubheading Example
31795 -exec-until recursive2.c:6
31799 *stopped,reason="location-reached",frame=@{func="main",args=[],
31800 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
31805 @subheading -file-clear
31806 Is this going away????
31809 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31810 @node GDB/MI Stack Manipulation
31811 @section @sc{gdb/mi} Stack Manipulation Commands
31813 @subheading The @code{-enable-frame-filters} Command
31814 @findex -enable-frame-filters
31817 -enable-frame-filters
31820 @value{GDBN} allows Python-based frame filters to affect the output of
31821 the MI commands relating to stack traces. As there is no way to
31822 implement this in a fully backward-compatible way, a front end must
31823 request that this functionality be enabled.
31825 Once enabled, this feature cannot be disabled.
31827 Note that if Python support has not been compiled into @value{GDBN},
31828 this command will still succeed (and do nothing).
31830 @subheading The @code{-stack-info-frame} Command
31831 @findex -stack-info-frame
31833 @subsubheading Synopsis
31839 Get info on the selected frame.
31841 @subsubheading @value{GDBN} Command
31843 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
31844 (without arguments).
31846 @subsubheading Example
31851 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
31852 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31853 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
31857 @subheading The @code{-stack-info-depth} Command
31858 @findex -stack-info-depth
31860 @subsubheading Synopsis
31863 -stack-info-depth [ @var{max-depth} ]
31866 Return the depth of the stack. If the integer argument @var{max-depth}
31867 is specified, do not count beyond @var{max-depth} frames.
31869 @subsubheading @value{GDBN} Command
31871 There's no equivalent @value{GDBN} command.
31873 @subsubheading Example
31875 For a stack with frame levels 0 through 11:
31882 -stack-info-depth 4
31885 -stack-info-depth 12
31888 -stack-info-depth 11
31891 -stack-info-depth 13
31896 @anchor{-stack-list-arguments}
31897 @subheading The @code{-stack-list-arguments} Command
31898 @findex -stack-list-arguments
31900 @subsubheading Synopsis
31903 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
31904 [ @var{low-frame} @var{high-frame} ]
31907 Display a list of the arguments for the frames between @var{low-frame}
31908 and @var{high-frame} (inclusive). If @var{low-frame} and
31909 @var{high-frame} are not provided, list the arguments for the whole
31910 call stack. If the two arguments are equal, show the single frame
31911 at the corresponding level. It is an error if @var{low-frame} is
31912 larger than the actual number of frames. On the other hand,
31913 @var{high-frame} may be larger than the actual number of frames, in
31914 which case only existing frames will be returned.
31916 If @var{print-values} is 0 or @code{--no-values}, print only the names of
31917 the variables; if it is 1 or @code{--all-values}, print also their
31918 values; and if it is 2 or @code{--simple-values}, print the name,
31919 type and value for simple data types, and the name and type for arrays,
31920 structures and unions. If the option @code{--no-frame-filters} is
31921 supplied, then Python frame filters will not be executed.
31923 If the @code{--skip-unavailable} option is specified, arguments that
31924 are not available are not listed. Partially available arguments
31925 are still displayed, however.
31927 Use of this command to obtain arguments in a single frame is
31928 deprecated in favor of the @samp{-stack-list-variables} command.
31930 @subsubheading @value{GDBN} Command
31932 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
31933 @samp{gdb_get_args} command which partially overlaps with the
31934 functionality of @samp{-stack-list-arguments}.
31936 @subsubheading Example
31943 frame=@{level="0",addr="0x00010734",func="callee4",
31944 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31945 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
31946 frame=@{level="1",addr="0x0001076c",func="callee3",
31947 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31948 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
31949 frame=@{level="2",addr="0x0001078c",func="callee2",
31950 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31951 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
31952 frame=@{level="3",addr="0x000107b4",func="callee1",
31953 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31954 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
31955 frame=@{level="4",addr="0x000107e0",func="main",
31956 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31957 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
31959 -stack-list-arguments 0
31962 frame=@{level="0",args=[]@},
31963 frame=@{level="1",args=[name="strarg"]@},
31964 frame=@{level="2",args=[name="intarg",name="strarg"]@},
31965 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
31966 frame=@{level="4",args=[]@}]
31968 -stack-list-arguments 1
31971 frame=@{level="0",args=[]@},
31973 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
31974 frame=@{level="2",args=[
31975 @{name="intarg",value="2"@},
31976 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
31977 @{frame=@{level="3",args=[
31978 @{name="intarg",value="2"@},
31979 @{name="strarg",value="0x11940 \"A string argument.\""@},
31980 @{name="fltarg",value="3.5"@}]@},
31981 frame=@{level="4",args=[]@}]
31983 -stack-list-arguments 0 2 2
31984 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
31986 -stack-list-arguments 1 2 2
31987 ^done,stack-args=[frame=@{level="2",
31988 args=[@{name="intarg",value="2"@},
31989 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
31993 @c @subheading -stack-list-exception-handlers
31996 @anchor{-stack-list-frames}
31997 @subheading The @code{-stack-list-frames} Command
31998 @findex -stack-list-frames
32000 @subsubheading Synopsis
32003 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
32006 List the frames currently on the stack. For each frame it displays the
32011 The frame number, 0 being the topmost frame, i.e., the innermost function.
32013 The @code{$pc} value for that frame.
32017 File name of the source file where the function lives.
32018 @item @var{fullname}
32019 The full file name of the source file where the function lives.
32021 Line number corresponding to the @code{$pc}.
32023 The shared library where this function is defined. This is only given
32024 if the frame's function is not known.
32027 If invoked without arguments, this command prints a backtrace for the
32028 whole stack. If given two integer arguments, it shows the frames whose
32029 levels are between the two arguments (inclusive). If the two arguments
32030 are equal, it shows the single frame at the corresponding level. It is
32031 an error if @var{low-frame} is larger than the actual number of
32032 frames. On the other hand, @var{high-frame} may be larger than the
32033 actual number of frames, in which case only existing frames will be
32034 returned. If the option @code{--no-frame-filters} is supplied, then
32035 Python frame filters will not be executed.
32037 @subsubheading @value{GDBN} Command
32039 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
32041 @subsubheading Example
32043 Full stack backtrace:
32049 [frame=@{level="0",addr="0x0001076c",func="foo",
32050 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
32051 frame=@{level="1",addr="0x000107a4",func="foo",
32052 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
32053 frame=@{level="2",addr="0x000107a4",func="foo",
32054 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
32055 frame=@{level="3",addr="0x000107a4",func="foo",
32056 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
32057 frame=@{level="4",addr="0x000107a4",func="foo",
32058 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
32059 frame=@{level="5",addr="0x000107a4",func="foo",
32060 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
32061 frame=@{level="6",addr="0x000107a4",func="foo",
32062 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
32063 frame=@{level="7",addr="0x000107a4",func="foo",
32064 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
32065 frame=@{level="8",addr="0x000107a4",func="foo",
32066 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
32067 frame=@{level="9",addr="0x000107a4",func="foo",
32068 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
32069 frame=@{level="10",addr="0x000107a4",func="foo",
32070 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
32071 frame=@{level="11",addr="0x00010738",func="main",
32072 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
32076 Show frames between @var{low_frame} and @var{high_frame}:
32080 -stack-list-frames 3 5
32082 [frame=@{level="3",addr="0x000107a4",func="foo",
32083 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
32084 frame=@{level="4",addr="0x000107a4",func="foo",
32085 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
32086 frame=@{level="5",addr="0x000107a4",func="foo",
32087 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
32091 Show a single frame:
32095 -stack-list-frames 3 3
32097 [frame=@{level="3",addr="0x000107a4",func="foo",
32098 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
32103 @subheading The @code{-stack-list-locals} Command
32104 @findex -stack-list-locals
32105 @anchor{-stack-list-locals}
32107 @subsubheading Synopsis
32110 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
32113 Display the local variable names for the selected frame. If
32114 @var{print-values} is 0 or @code{--no-values}, print only the names of
32115 the variables; if it is 1 or @code{--all-values}, print also their
32116 values; and if it is 2 or @code{--simple-values}, print the name,
32117 type and value for simple data types, and the name and type for arrays,
32118 structures and unions. In this last case, a frontend can immediately
32119 display the value of simple data types and create variable objects for
32120 other data types when the user wishes to explore their values in
32121 more detail. If the option @code{--no-frame-filters} is supplied, then
32122 Python frame filters will not be executed.
32124 If the @code{--skip-unavailable} option is specified, local variables
32125 that are not available are not listed. Partially available local
32126 variables are still displayed, however.
32128 This command is deprecated in favor of the
32129 @samp{-stack-list-variables} command.
32131 @subsubheading @value{GDBN} Command
32133 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
32135 @subsubheading Example
32139 -stack-list-locals 0
32140 ^done,locals=[name="A",name="B",name="C"]
32142 -stack-list-locals --all-values
32143 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
32144 @{name="C",value="@{1, 2, 3@}"@}]
32145 -stack-list-locals --simple-values
32146 ^done,locals=[@{name="A",type="int",value="1"@},
32147 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
32151 @anchor{-stack-list-variables}
32152 @subheading The @code{-stack-list-variables} Command
32153 @findex -stack-list-variables
32155 @subsubheading Synopsis
32158 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
32161 Display the names of local variables and function arguments for the selected frame. If
32162 @var{print-values} is 0 or @code{--no-values}, print only the names of
32163 the variables; if it is 1 or @code{--all-values}, print also their
32164 values; and if it is 2 or @code{--simple-values}, print the name,
32165 type and value for simple data types, and the name and type for arrays,
32166 structures and unions. If the option @code{--no-frame-filters} is
32167 supplied, then Python frame filters will not be executed.
32169 If the @code{--skip-unavailable} option is specified, local variables
32170 and arguments that are not available are not listed. Partially
32171 available arguments and local variables are still displayed, however.
32173 @subsubheading Example
32177 -stack-list-variables --thread 1 --frame 0 --all-values
32178 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
32183 @subheading The @code{-stack-select-frame} Command
32184 @findex -stack-select-frame
32186 @subsubheading Synopsis
32189 -stack-select-frame @var{framenum}
32192 Change the selected frame. Select a different frame @var{framenum} on
32195 This command in deprecated in favor of passing the @samp{--frame}
32196 option to every command.
32198 @subsubheading @value{GDBN} Command
32200 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
32201 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
32203 @subsubheading Example
32207 -stack-select-frame 2
32212 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32213 @node GDB/MI Variable Objects
32214 @section @sc{gdb/mi} Variable Objects
32218 @subheading Motivation for Variable Objects in @sc{gdb/mi}
32220 For the implementation of a variable debugger window (locals, watched
32221 expressions, etc.), we are proposing the adaptation of the existing code
32222 used by @code{Insight}.
32224 The two main reasons for that are:
32228 It has been proven in practice (it is already on its second generation).
32231 It will shorten development time (needless to say how important it is
32235 The original interface was designed to be used by Tcl code, so it was
32236 slightly changed so it could be used through @sc{gdb/mi}. This section
32237 describes the @sc{gdb/mi} operations that will be available and gives some
32238 hints about their use.
32240 @emph{Note}: In addition to the set of operations described here, we
32241 expect the @sc{gui} implementation of a variable window to require, at
32242 least, the following operations:
32245 @item @code{-gdb-show} @code{output-radix}
32246 @item @code{-stack-list-arguments}
32247 @item @code{-stack-list-locals}
32248 @item @code{-stack-select-frame}
32253 @subheading Introduction to Variable Objects
32255 @cindex variable objects in @sc{gdb/mi}
32257 Variable objects are "object-oriented" MI interface for examining and
32258 changing values of expressions. Unlike some other MI interfaces that
32259 work with expressions, variable objects are specifically designed for
32260 simple and efficient presentation in the frontend. A variable object
32261 is identified by string name. When a variable object is created, the
32262 frontend specifies the expression for that variable object. The
32263 expression can be a simple variable, or it can be an arbitrary complex
32264 expression, and can even involve CPU registers. After creating a
32265 variable object, the frontend can invoke other variable object
32266 operations---for example to obtain or change the value of a variable
32267 object, or to change display format.
32269 Variable objects have hierarchical tree structure. Any variable object
32270 that corresponds to a composite type, such as structure in C, has
32271 a number of child variable objects, for example corresponding to each
32272 element of a structure. A child variable object can itself have
32273 children, recursively. Recursion ends when we reach
32274 leaf variable objects, which always have built-in types. Child variable
32275 objects are created only by explicit request, so if a frontend
32276 is not interested in the children of a particular variable object, no
32277 child will be created.
32279 For a leaf variable object it is possible to obtain its value as a
32280 string, or set the value from a string. String value can be also
32281 obtained for a non-leaf variable object, but it's generally a string
32282 that only indicates the type of the object, and does not list its
32283 contents. Assignment to a non-leaf variable object is not allowed.
32285 A frontend does not need to read the values of all variable objects each time
32286 the program stops. Instead, MI provides an update command that lists all
32287 variable objects whose values has changed since the last update
32288 operation. This considerably reduces the amount of data that must
32289 be transferred to the frontend. As noted above, children variable
32290 objects are created on demand, and only leaf variable objects have a
32291 real value. As result, gdb will read target memory only for leaf
32292 variables that frontend has created.
32294 The automatic update is not always desirable. For example, a frontend
32295 might want to keep a value of some expression for future reference,
32296 and never update it. For another example, fetching memory is
32297 relatively slow for embedded targets, so a frontend might want
32298 to disable automatic update for the variables that are either not
32299 visible on the screen, or ``closed''. This is possible using so
32300 called ``frozen variable objects''. Such variable objects are never
32301 implicitly updated.
32303 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
32304 fixed variable object, the expression is parsed when the variable
32305 object is created, including associating identifiers to specific
32306 variables. The meaning of expression never changes. For a floating
32307 variable object the values of variables whose names appear in the
32308 expressions are re-evaluated every time in the context of the current
32309 frame. Consider this example:
32314 struct work_state state;
32321 If a fixed variable object for the @code{state} variable is created in
32322 this function, and we enter the recursive call, the variable
32323 object will report the value of @code{state} in the top-level
32324 @code{do_work} invocation. On the other hand, a floating variable
32325 object will report the value of @code{state} in the current frame.
32327 If an expression specified when creating a fixed variable object
32328 refers to a local variable, the variable object becomes bound to the
32329 thread and frame in which the variable object is created. When such
32330 variable object is updated, @value{GDBN} makes sure that the
32331 thread/frame combination the variable object is bound to still exists,
32332 and re-evaluates the variable object in context of that thread/frame.
32334 The following is the complete set of @sc{gdb/mi} operations defined to
32335 access this functionality:
32337 @multitable @columnfractions .4 .6
32338 @item @strong{Operation}
32339 @tab @strong{Description}
32341 @item @code{-enable-pretty-printing}
32342 @tab enable Python-based pretty-printing
32343 @item @code{-var-create}
32344 @tab create a variable object
32345 @item @code{-var-delete}
32346 @tab delete the variable object and/or its children
32347 @item @code{-var-set-format}
32348 @tab set the display format of this variable
32349 @item @code{-var-show-format}
32350 @tab show the display format of this variable
32351 @item @code{-var-info-num-children}
32352 @tab tells how many children this object has
32353 @item @code{-var-list-children}
32354 @tab return a list of the object's children
32355 @item @code{-var-info-type}
32356 @tab show the type of this variable object
32357 @item @code{-var-info-expression}
32358 @tab print parent-relative expression that this variable object represents
32359 @item @code{-var-info-path-expression}
32360 @tab print full expression that this variable object represents
32361 @item @code{-var-show-attributes}
32362 @tab is this variable editable? does it exist here?
32363 @item @code{-var-evaluate-expression}
32364 @tab get the value of this variable
32365 @item @code{-var-assign}
32366 @tab set the value of this variable
32367 @item @code{-var-update}
32368 @tab update the variable and its children
32369 @item @code{-var-set-frozen}
32370 @tab set frozeness attribute
32371 @item @code{-var-set-update-range}
32372 @tab set range of children to display on update
32375 In the next subsection we describe each operation in detail and suggest
32376 how it can be used.
32378 @subheading Description And Use of Operations on Variable Objects
32380 @subheading The @code{-enable-pretty-printing} Command
32381 @findex -enable-pretty-printing
32384 -enable-pretty-printing
32387 @value{GDBN} allows Python-based visualizers to affect the output of the
32388 MI variable object commands. However, because there was no way to
32389 implement this in a fully backward-compatible way, a front end must
32390 request that this functionality be enabled.
32392 Once enabled, this feature cannot be disabled.
32394 Note that if Python support has not been compiled into @value{GDBN},
32395 this command will still succeed (and do nothing).
32397 This feature is currently (as of @value{GDBN} 7.0) experimental, and
32398 may work differently in future versions of @value{GDBN}.
32400 @subheading The @code{-var-create} Command
32401 @findex -var-create
32403 @subsubheading Synopsis
32406 -var-create @{@var{name} | "-"@}
32407 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
32410 This operation creates a variable object, which allows the monitoring of
32411 a variable, the result of an expression, a memory cell or a CPU
32414 The @var{name} parameter is the string by which the object can be
32415 referenced. It must be unique. If @samp{-} is specified, the varobj
32416 system will generate a string ``varNNNNNN'' automatically. It will be
32417 unique provided that one does not specify @var{name} of that format.
32418 The command fails if a duplicate name is found.
32420 The frame under which the expression should be evaluated can be
32421 specified by @var{frame-addr}. A @samp{*} indicates that the current
32422 frame should be used. A @samp{@@} indicates that a floating variable
32423 object must be created.
32425 @var{expression} is any expression valid on the current language set (must not
32426 begin with a @samp{*}), or one of the following:
32430 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
32433 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
32436 @samp{$@var{regname}} --- a CPU register name
32439 @cindex dynamic varobj
32440 A varobj's contents may be provided by a Python-based pretty-printer. In this
32441 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
32442 have slightly different semantics in some cases. If the
32443 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
32444 will never create a dynamic varobj. This ensures backward
32445 compatibility for existing clients.
32447 @subsubheading Result
32449 This operation returns attributes of the newly-created varobj. These
32454 The name of the varobj.
32457 The number of children of the varobj. This number is not necessarily
32458 reliable for a dynamic varobj. Instead, you must examine the
32459 @samp{has_more} attribute.
32462 The varobj's scalar value. For a varobj whose type is some sort of
32463 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
32464 will not be interesting.
32467 The varobj's type. This is a string representation of the type, as
32468 would be printed by the @value{GDBN} CLI. If @samp{print object}
32469 (@pxref{Print Settings, set print object}) is set to @code{on}, the
32470 @emph{actual} (derived) type of the object is shown rather than the
32471 @emph{declared} one.
32474 If a variable object is bound to a specific thread, then this is the
32475 thread's identifier.
32478 For a dynamic varobj, this indicates whether there appear to be any
32479 children available. For a non-dynamic varobj, this will be 0.
32482 This attribute will be present and have the value @samp{1} if the
32483 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
32484 then this attribute will not be present.
32487 A dynamic varobj can supply a display hint to the front end. The
32488 value comes directly from the Python pretty-printer object's
32489 @code{display_hint} method. @xref{Pretty Printing API}.
32492 Typical output will look like this:
32495 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
32496 has_more="@var{has_more}"
32500 @subheading The @code{-var-delete} Command
32501 @findex -var-delete
32503 @subsubheading Synopsis
32506 -var-delete [ -c ] @var{name}
32509 Deletes a previously created variable object and all of its children.
32510 With the @samp{-c} option, just deletes the children.
32512 Returns an error if the object @var{name} is not found.
32515 @subheading The @code{-var-set-format} Command
32516 @findex -var-set-format
32518 @subsubheading Synopsis
32521 -var-set-format @var{name} @var{format-spec}
32524 Sets the output format for the value of the object @var{name} to be
32527 @anchor{-var-set-format}
32528 The syntax for the @var{format-spec} is as follows:
32531 @var{format-spec} @expansion{}
32532 @{binary | decimal | hexadecimal | octal | natural@}
32535 The natural format is the default format choosen automatically
32536 based on the variable type (like decimal for an @code{int}, hex
32537 for pointers, etc.).
32539 For a variable with children, the format is set only on the
32540 variable itself, and the children are not affected.
32542 @subheading The @code{-var-show-format} Command
32543 @findex -var-show-format
32545 @subsubheading Synopsis
32548 -var-show-format @var{name}
32551 Returns the format used to display the value of the object @var{name}.
32554 @var{format} @expansion{}
32559 @subheading The @code{-var-info-num-children} Command
32560 @findex -var-info-num-children
32562 @subsubheading Synopsis
32565 -var-info-num-children @var{name}
32568 Returns the number of children of a variable object @var{name}:
32574 Note that this number is not completely reliable for a dynamic varobj.
32575 It will return the current number of children, but more children may
32579 @subheading The @code{-var-list-children} Command
32580 @findex -var-list-children
32582 @subsubheading Synopsis
32585 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
32587 @anchor{-var-list-children}
32589 Return a list of the children of the specified variable object and
32590 create variable objects for them, if they do not already exist. With
32591 a single argument or if @var{print-values} has a value of 0 or
32592 @code{--no-values}, print only the names of the variables; if
32593 @var{print-values} is 1 or @code{--all-values}, also print their
32594 values; and if it is 2 or @code{--simple-values} print the name and
32595 value for simple data types and just the name for arrays, structures
32598 @var{from} and @var{to}, if specified, indicate the range of children
32599 to report. If @var{from} or @var{to} is less than zero, the range is
32600 reset and all children will be reported. Otherwise, children starting
32601 at @var{from} (zero-based) and up to and excluding @var{to} will be
32604 If a child range is requested, it will only affect the current call to
32605 @code{-var-list-children}, but not future calls to @code{-var-update}.
32606 For this, you must instead use @code{-var-set-update-range}. The
32607 intent of this approach is to enable a front end to implement any
32608 update approach it likes; for example, scrolling a view may cause the
32609 front end to request more children with @code{-var-list-children}, and
32610 then the front end could call @code{-var-set-update-range} with a
32611 different range to ensure that future updates are restricted to just
32614 For each child the following results are returned:
32619 Name of the variable object created for this child.
32622 The expression to be shown to the user by the front end to designate this child.
32623 For example this may be the name of a structure member.
32625 For a dynamic varobj, this value cannot be used to form an
32626 expression. There is no way to do this at all with a dynamic varobj.
32628 For C/C@t{++} structures there are several pseudo children returned to
32629 designate access qualifiers. For these pseudo children @var{exp} is
32630 @samp{public}, @samp{private}, or @samp{protected}. In this case the
32631 type and value are not present.
32633 A dynamic varobj will not report the access qualifying
32634 pseudo-children, regardless of the language. This information is not
32635 available at all with a dynamic varobj.
32638 Number of children this child has. For a dynamic varobj, this will be
32642 The type of the child. If @samp{print object}
32643 (@pxref{Print Settings, set print object}) is set to @code{on}, the
32644 @emph{actual} (derived) type of the object is shown rather than the
32645 @emph{declared} one.
32648 If values were requested, this is the value.
32651 If this variable object is associated with a thread, this is the thread id.
32652 Otherwise this result is not present.
32655 If the variable object is frozen, this variable will be present with a value of 1.
32658 A dynamic varobj can supply a display hint to the front end. The
32659 value comes directly from the Python pretty-printer object's
32660 @code{display_hint} method. @xref{Pretty Printing API}.
32663 This attribute will be present and have the value @samp{1} if the
32664 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
32665 then this attribute will not be present.
32669 The result may have its own attributes:
32673 A dynamic varobj can supply a display hint to the front end. The
32674 value comes directly from the Python pretty-printer object's
32675 @code{display_hint} method. @xref{Pretty Printing API}.
32678 This is an integer attribute which is nonzero if there are children
32679 remaining after the end of the selected range.
32682 @subsubheading Example
32686 -var-list-children n
32687 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
32688 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
32690 -var-list-children --all-values n
32691 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
32692 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
32696 @subheading The @code{-var-info-type} Command
32697 @findex -var-info-type
32699 @subsubheading Synopsis
32702 -var-info-type @var{name}
32705 Returns the type of the specified variable @var{name}. The type is
32706 returned as a string in the same format as it is output by the
32710 type=@var{typename}
32714 @subheading The @code{-var-info-expression} Command
32715 @findex -var-info-expression
32717 @subsubheading Synopsis
32720 -var-info-expression @var{name}
32723 Returns a string that is suitable for presenting this
32724 variable object in user interface. The string is generally
32725 not valid expression in the current language, and cannot be evaluated.
32727 For example, if @code{a} is an array, and variable object
32728 @code{A} was created for @code{a}, then we'll get this output:
32731 (gdb) -var-info-expression A.1
32732 ^done,lang="C",exp="1"
32736 Here, the value of @code{lang} is the language name, which can be
32737 found in @ref{Supported Languages}.
32739 Note that the output of the @code{-var-list-children} command also
32740 includes those expressions, so the @code{-var-info-expression} command
32743 @subheading The @code{-var-info-path-expression} Command
32744 @findex -var-info-path-expression
32746 @subsubheading Synopsis
32749 -var-info-path-expression @var{name}
32752 Returns an expression that can be evaluated in the current
32753 context and will yield the same value that a variable object has.
32754 Compare this with the @code{-var-info-expression} command, which
32755 result can be used only for UI presentation. Typical use of
32756 the @code{-var-info-path-expression} command is creating a
32757 watchpoint from a variable object.
32759 This command is currently not valid for children of a dynamic varobj,
32760 and will give an error when invoked on one.
32762 For example, suppose @code{C} is a C@t{++} class, derived from class
32763 @code{Base}, and that the @code{Base} class has a member called
32764 @code{m_size}. Assume a variable @code{c} is has the type of
32765 @code{C} and a variable object @code{C} was created for variable
32766 @code{c}. Then, we'll get this output:
32768 (gdb) -var-info-path-expression C.Base.public.m_size
32769 ^done,path_expr=((Base)c).m_size)
32772 @subheading The @code{-var-show-attributes} Command
32773 @findex -var-show-attributes
32775 @subsubheading Synopsis
32778 -var-show-attributes @var{name}
32781 List attributes of the specified variable object @var{name}:
32784 status=@var{attr} [ ( ,@var{attr} )* ]
32788 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
32790 @subheading The @code{-var-evaluate-expression} Command
32791 @findex -var-evaluate-expression
32793 @subsubheading Synopsis
32796 -var-evaluate-expression [-f @var{format-spec}] @var{name}
32799 Evaluates the expression that is represented by the specified variable
32800 object and returns its value as a string. The format of the string
32801 can be specified with the @samp{-f} option. The possible values of
32802 this option are the same as for @code{-var-set-format}
32803 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
32804 the current display format will be used. The current display format
32805 can be changed using the @code{-var-set-format} command.
32811 Note that one must invoke @code{-var-list-children} for a variable
32812 before the value of a child variable can be evaluated.
32814 @subheading The @code{-var-assign} Command
32815 @findex -var-assign
32817 @subsubheading Synopsis
32820 -var-assign @var{name} @var{expression}
32823 Assigns the value of @var{expression} to the variable object specified
32824 by @var{name}. The object must be @samp{editable}. If the variable's
32825 value is altered by the assign, the variable will show up in any
32826 subsequent @code{-var-update} list.
32828 @subsubheading Example
32836 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
32840 @subheading The @code{-var-update} Command
32841 @findex -var-update
32843 @subsubheading Synopsis
32846 -var-update [@var{print-values}] @{@var{name} | "*"@}
32849 Reevaluate the expressions corresponding to the variable object
32850 @var{name} and all its direct and indirect children, and return the
32851 list of variable objects whose values have changed; @var{name} must
32852 be a root variable object. Here, ``changed'' means that the result of
32853 @code{-var-evaluate-expression} before and after the
32854 @code{-var-update} is different. If @samp{*} is used as the variable
32855 object names, all existing variable objects are updated, except
32856 for frozen ones (@pxref{-var-set-frozen}). The option
32857 @var{print-values} determines whether both names and values, or just
32858 names are printed. The possible values of this option are the same
32859 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
32860 recommended to use the @samp{--all-values} option, to reduce the
32861 number of MI commands needed on each program stop.
32863 With the @samp{*} parameter, if a variable object is bound to a
32864 currently running thread, it will not be updated, without any
32867 If @code{-var-set-update-range} was previously used on a varobj, then
32868 only the selected range of children will be reported.
32870 @code{-var-update} reports all the changed varobjs in a tuple named
32873 Each item in the change list is itself a tuple holding:
32877 The name of the varobj.
32880 If values were requested for this update, then this field will be
32881 present and will hold the value of the varobj.
32884 @anchor{-var-update}
32885 This field is a string which may take one of three values:
32889 The variable object's current value is valid.
32892 The variable object does not currently hold a valid value but it may
32893 hold one in the future if its associated expression comes back into
32897 The variable object no longer holds a valid value.
32898 This can occur when the executable file being debugged has changed,
32899 either through recompilation or by using the @value{GDBN} @code{file}
32900 command. The front end should normally choose to delete these variable
32904 In the future new values may be added to this list so the front should
32905 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
32908 This is only present if the varobj is still valid. If the type
32909 changed, then this will be the string @samp{true}; otherwise it will
32912 When a varobj's type changes, its children are also likely to have
32913 become incorrect. Therefore, the varobj's children are automatically
32914 deleted when this attribute is @samp{true}. Also, the varobj's update
32915 range, when set using the @code{-var-set-update-range} command, is
32919 If the varobj's type changed, then this field will be present and will
32922 @item new_num_children
32923 For a dynamic varobj, if the number of children changed, or if the
32924 type changed, this will be the new number of children.
32926 The @samp{numchild} field in other varobj responses is generally not
32927 valid for a dynamic varobj -- it will show the number of children that
32928 @value{GDBN} knows about, but because dynamic varobjs lazily
32929 instantiate their children, this will not reflect the number of
32930 children which may be available.
32932 The @samp{new_num_children} attribute only reports changes to the
32933 number of children known by @value{GDBN}. This is the only way to
32934 detect whether an update has removed children (which necessarily can
32935 only happen at the end of the update range).
32938 The display hint, if any.
32941 This is an integer value, which will be 1 if there are more children
32942 available outside the varobj's update range.
32945 This attribute will be present and have the value @samp{1} if the
32946 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
32947 then this attribute will not be present.
32950 If new children were added to a dynamic varobj within the selected
32951 update range (as set by @code{-var-set-update-range}), then they will
32952 be listed in this attribute.
32955 @subsubheading Example
32962 -var-update --all-values var1
32963 ^done,changelist=[@{name="var1",value="3",in_scope="true",
32964 type_changed="false"@}]
32968 @subheading The @code{-var-set-frozen} Command
32969 @findex -var-set-frozen
32970 @anchor{-var-set-frozen}
32972 @subsubheading Synopsis
32975 -var-set-frozen @var{name} @var{flag}
32978 Set the frozenness flag on the variable object @var{name}. The
32979 @var{flag} parameter should be either @samp{1} to make the variable
32980 frozen or @samp{0} to make it unfrozen. If a variable object is
32981 frozen, then neither itself, nor any of its children, are
32982 implicitly updated by @code{-var-update} of
32983 a parent variable or by @code{-var-update *}. Only
32984 @code{-var-update} of the variable itself will update its value and
32985 values of its children. After a variable object is unfrozen, it is
32986 implicitly updated by all subsequent @code{-var-update} operations.
32987 Unfreezing a variable does not update it, only subsequent
32988 @code{-var-update} does.
32990 @subsubheading Example
32994 -var-set-frozen V 1
32999 @subheading The @code{-var-set-update-range} command
33000 @findex -var-set-update-range
33001 @anchor{-var-set-update-range}
33003 @subsubheading Synopsis
33006 -var-set-update-range @var{name} @var{from} @var{to}
33009 Set the range of children to be returned by future invocations of
33010 @code{-var-update}.
33012 @var{from} and @var{to} indicate the range of children to report. If
33013 @var{from} or @var{to} is less than zero, the range is reset and all
33014 children will be reported. Otherwise, children starting at @var{from}
33015 (zero-based) and up to and excluding @var{to} will be reported.
33017 @subsubheading Example
33021 -var-set-update-range V 1 2
33025 @subheading The @code{-var-set-visualizer} command
33026 @findex -var-set-visualizer
33027 @anchor{-var-set-visualizer}
33029 @subsubheading Synopsis
33032 -var-set-visualizer @var{name} @var{visualizer}
33035 Set a visualizer for the variable object @var{name}.
33037 @var{visualizer} is the visualizer to use. The special value
33038 @samp{None} means to disable any visualizer in use.
33040 If not @samp{None}, @var{visualizer} must be a Python expression.
33041 This expression must evaluate to a callable object which accepts a
33042 single argument. @value{GDBN} will call this object with the value of
33043 the varobj @var{name} as an argument (this is done so that the same
33044 Python pretty-printing code can be used for both the CLI and MI).
33045 When called, this object must return an object which conforms to the
33046 pretty-printing interface (@pxref{Pretty Printing API}).
33048 The pre-defined function @code{gdb.default_visualizer} may be used to
33049 select a visualizer by following the built-in process
33050 (@pxref{Selecting Pretty-Printers}). This is done automatically when
33051 a varobj is created, and so ordinarily is not needed.
33053 This feature is only available if Python support is enabled. The MI
33054 command @code{-list-features} (@pxref{GDB/MI Support Commands})
33055 can be used to check this.
33057 @subsubheading Example
33059 Resetting the visualizer:
33063 -var-set-visualizer V None
33067 Reselecting the default (type-based) visualizer:
33071 -var-set-visualizer V gdb.default_visualizer
33075 Suppose @code{SomeClass} is a visualizer class. A lambda expression
33076 can be used to instantiate this class for a varobj:
33080 -var-set-visualizer V "lambda val: SomeClass()"
33084 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33085 @node GDB/MI Data Manipulation
33086 @section @sc{gdb/mi} Data Manipulation
33088 @cindex data manipulation, in @sc{gdb/mi}
33089 @cindex @sc{gdb/mi}, data manipulation
33090 This section describes the @sc{gdb/mi} commands that manipulate data:
33091 examine memory and registers, evaluate expressions, etc.
33093 @c REMOVED FROM THE INTERFACE.
33094 @c @subheading -data-assign
33095 @c Change the value of a program variable. Plenty of side effects.
33096 @c @subsubheading GDB Command
33098 @c @subsubheading Example
33101 @subheading The @code{-data-disassemble} Command
33102 @findex -data-disassemble
33104 @subsubheading Synopsis
33108 [ -s @var{start-addr} -e @var{end-addr} ]
33109 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
33117 @item @var{start-addr}
33118 is the beginning address (or @code{$pc})
33119 @item @var{end-addr}
33121 @item @var{filename}
33122 is the name of the file to disassemble
33123 @item @var{linenum}
33124 is the line number to disassemble around
33126 is the number of disassembly lines to be produced. If it is -1,
33127 the whole function will be disassembled, in case no @var{end-addr} is
33128 specified. If @var{end-addr} is specified as a non-zero value, and
33129 @var{lines} is lower than the number of disassembly lines between
33130 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
33131 displayed; if @var{lines} is higher than the number of lines between
33132 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
33135 is either 0 (meaning only disassembly), 1 (meaning mixed source and
33136 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
33137 mixed source and disassembly with raw opcodes).
33140 @subsubheading Result
33142 The result of the @code{-data-disassemble} command will be a list named
33143 @samp{asm_insns}, the contents of this list depend on the @var{mode}
33144 used with the @code{-data-disassemble} command.
33146 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
33151 The address at which this instruction was disassembled.
33154 The name of the function this instruction is within.
33157 The decimal offset in bytes from the start of @samp{func-name}.
33160 The text disassembly for this @samp{address}.
33163 This field is only present for mode 2. This contains the raw opcode
33164 bytes for the @samp{inst} field.
33168 For modes 1 and 3 the @samp{asm_insns} list contains tuples named
33169 @samp{src_and_asm_line}, each of which has the following fields:
33173 The line number within @samp{file}.
33176 The file name from the compilation unit. This might be an absolute
33177 file name or a relative file name depending on the compile command
33181 Absolute file name of @samp{file}. It is converted to a canonical form
33182 using the source file search path
33183 (@pxref{Source Path, ,Specifying Source Directories})
33184 and after resolving all the symbolic links.
33186 If the source file is not found this field will contain the path as
33187 present in the debug information.
33189 @item line_asm_insn
33190 This is a list of tuples containing the disassembly for @samp{line} in
33191 @samp{file}. The fields of each tuple are the same as for
33192 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
33193 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
33198 Note that whatever included in the @samp{inst} field, is not
33199 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
33202 @subsubheading @value{GDBN} Command
33204 The corresponding @value{GDBN} command is @samp{disassemble}.
33206 @subsubheading Example
33208 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
33212 -data-disassemble -s $pc -e "$pc + 20" -- 0
33215 @{address="0x000107c0",func-name="main",offset="4",
33216 inst="mov 2, %o0"@},
33217 @{address="0x000107c4",func-name="main",offset="8",
33218 inst="sethi %hi(0x11800), %o2"@},
33219 @{address="0x000107c8",func-name="main",offset="12",
33220 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
33221 @{address="0x000107cc",func-name="main",offset="16",
33222 inst="sethi %hi(0x11800), %o2"@},
33223 @{address="0x000107d0",func-name="main",offset="20",
33224 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
33228 Disassemble the whole @code{main} function. Line 32 is part of
33232 -data-disassemble -f basics.c -l 32 -- 0
33234 @{address="0x000107bc",func-name="main",offset="0",
33235 inst="save %sp, -112, %sp"@},
33236 @{address="0x000107c0",func-name="main",offset="4",
33237 inst="mov 2, %o0"@},
33238 @{address="0x000107c4",func-name="main",offset="8",
33239 inst="sethi %hi(0x11800), %o2"@},
33241 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
33242 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
33246 Disassemble 3 instructions from the start of @code{main}:
33250 -data-disassemble -f basics.c -l 32 -n 3 -- 0
33252 @{address="0x000107bc",func-name="main",offset="0",
33253 inst="save %sp, -112, %sp"@},
33254 @{address="0x000107c0",func-name="main",offset="4",
33255 inst="mov 2, %o0"@},
33256 @{address="0x000107c4",func-name="main",offset="8",
33257 inst="sethi %hi(0x11800), %o2"@}]
33261 Disassemble 3 instructions from the start of @code{main} in mixed mode:
33265 -data-disassemble -f basics.c -l 32 -n 3 -- 1
33267 src_and_asm_line=@{line="31",
33268 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
33269 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
33270 line_asm_insn=[@{address="0x000107bc",
33271 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
33272 src_and_asm_line=@{line="32",
33273 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
33274 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
33275 line_asm_insn=[@{address="0x000107c0",
33276 func-name="main",offset="4",inst="mov 2, %o0"@},
33277 @{address="0x000107c4",func-name="main",offset="8",
33278 inst="sethi %hi(0x11800), %o2"@}]@}]
33283 @subheading The @code{-data-evaluate-expression} Command
33284 @findex -data-evaluate-expression
33286 @subsubheading Synopsis
33289 -data-evaluate-expression @var{expr}
33292 Evaluate @var{expr} as an expression. The expression could contain an
33293 inferior function call. The function call will execute synchronously.
33294 If the expression contains spaces, it must be enclosed in double quotes.
33296 @subsubheading @value{GDBN} Command
33298 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
33299 @samp{call}. In @code{gdbtk} only, there's a corresponding
33300 @samp{gdb_eval} command.
33302 @subsubheading Example
33304 In the following example, the numbers that precede the commands are the
33305 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
33306 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
33310 211-data-evaluate-expression A
33313 311-data-evaluate-expression &A
33314 311^done,value="0xefffeb7c"
33316 411-data-evaluate-expression A+3
33319 511-data-evaluate-expression "A + 3"
33325 @subheading The @code{-data-list-changed-registers} Command
33326 @findex -data-list-changed-registers
33328 @subsubheading Synopsis
33331 -data-list-changed-registers
33334 Display a list of the registers that have changed.
33336 @subsubheading @value{GDBN} Command
33338 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
33339 has the corresponding command @samp{gdb_changed_register_list}.
33341 @subsubheading Example
33343 On a PPC MBX board:
33351 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
33352 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
33355 -data-list-changed-registers
33356 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
33357 "10","11","13","14","15","16","17","18","19","20","21","22","23",
33358 "24","25","26","27","28","30","31","64","65","66","67","69"]
33363 @subheading The @code{-data-list-register-names} Command
33364 @findex -data-list-register-names
33366 @subsubheading Synopsis
33369 -data-list-register-names [ ( @var{regno} )+ ]
33372 Show a list of register names for the current target. If no arguments
33373 are given, it shows a list of the names of all the registers. If
33374 integer numbers are given as arguments, it will print a list of the
33375 names of the registers corresponding to the arguments. To ensure
33376 consistency between a register name and its number, the output list may
33377 include empty register names.
33379 @subsubheading @value{GDBN} Command
33381 @value{GDBN} does not have a command which corresponds to
33382 @samp{-data-list-register-names}. In @code{gdbtk} there is a
33383 corresponding command @samp{gdb_regnames}.
33385 @subsubheading Example
33387 For the PPC MBX board:
33390 -data-list-register-names
33391 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
33392 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
33393 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
33394 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
33395 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
33396 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
33397 "", "pc","ps","cr","lr","ctr","xer"]
33399 -data-list-register-names 1 2 3
33400 ^done,register-names=["r1","r2","r3"]
33404 @subheading The @code{-data-list-register-values} Command
33405 @findex -data-list-register-values
33407 @subsubheading Synopsis
33410 -data-list-register-values
33411 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
33414 Display the registers' contents. @var{fmt} is the format according to
33415 which the registers' contents are to be returned, followed by an optional
33416 list of numbers specifying the registers to display. A missing list of
33417 numbers indicates that the contents of all the registers must be
33418 returned. The @code{--skip-unavailable} option indicates that only
33419 the available registers are to be returned.
33421 Allowed formats for @var{fmt} are:
33438 @subsubheading @value{GDBN} Command
33440 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
33441 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
33443 @subsubheading Example
33445 For a PPC MBX board (note: line breaks are for readability only, they
33446 don't appear in the actual output):
33450 -data-list-register-values r 64 65
33451 ^done,register-values=[@{number="64",value="0xfe00a300"@},
33452 @{number="65",value="0x00029002"@}]
33454 -data-list-register-values x
33455 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
33456 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
33457 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
33458 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
33459 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
33460 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
33461 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
33462 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
33463 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
33464 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
33465 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
33466 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
33467 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
33468 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
33469 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
33470 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
33471 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
33472 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
33473 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
33474 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
33475 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
33476 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
33477 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
33478 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
33479 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
33480 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
33481 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
33482 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
33483 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
33484 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
33485 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
33486 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
33487 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
33488 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
33489 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
33490 @{number="69",value="0x20002b03"@}]
33495 @subheading The @code{-data-read-memory} Command
33496 @findex -data-read-memory
33498 This command is deprecated, use @code{-data-read-memory-bytes} instead.
33500 @subsubheading Synopsis
33503 -data-read-memory [ -o @var{byte-offset} ]
33504 @var{address} @var{word-format} @var{word-size}
33505 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
33512 @item @var{address}
33513 An expression specifying the address of the first memory word to be
33514 read. Complex expressions containing embedded white space should be
33515 quoted using the C convention.
33517 @item @var{word-format}
33518 The format to be used to print the memory words. The notation is the
33519 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
33522 @item @var{word-size}
33523 The size of each memory word in bytes.
33525 @item @var{nr-rows}
33526 The number of rows in the output table.
33528 @item @var{nr-cols}
33529 The number of columns in the output table.
33532 If present, indicates that each row should include an @sc{ascii} dump. The
33533 value of @var{aschar} is used as a padding character when a byte is not a
33534 member of the printable @sc{ascii} character set (printable @sc{ascii}
33535 characters are those whose code is between 32 and 126, inclusively).
33537 @item @var{byte-offset}
33538 An offset to add to the @var{address} before fetching memory.
33541 This command displays memory contents as a table of @var{nr-rows} by
33542 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
33543 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
33544 (returned as @samp{total-bytes}). Should less than the requested number
33545 of bytes be returned by the target, the missing words are identified
33546 using @samp{N/A}. The number of bytes read from the target is returned
33547 in @samp{nr-bytes} and the starting address used to read memory in
33550 The address of the next/previous row or page is available in
33551 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
33554 @subsubheading @value{GDBN} Command
33556 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
33557 @samp{gdb_get_mem} memory read command.
33559 @subsubheading Example
33561 Read six bytes of memory starting at @code{bytes+6} but then offset by
33562 @code{-6} bytes. Format as three rows of two columns. One byte per
33563 word. Display each word in hex.
33567 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
33568 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
33569 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
33570 prev-page="0x0000138a",memory=[
33571 @{addr="0x00001390",data=["0x00","0x01"]@},
33572 @{addr="0x00001392",data=["0x02","0x03"]@},
33573 @{addr="0x00001394",data=["0x04","0x05"]@}]
33577 Read two bytes of memory starting at address @code{shorts + 64} and
33578 display as a single word formatted in decimal.
33582 5-data-read-memory shorts+64 d 2 1 1
33583 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
33584 next-row="0x00001512",prev-row="0x0000150e",
33585 next-page="0x00001512",prev-page="0x0000150e",memory=[
33586 @{addr="0x00001510",data=["128"]@}]
33590 Read thirty two bytes of memory starting at @code{bytes+16} and format
33591 as eight rows of four columns. Include a string encoding with @samp{x}
33592 used as the non-printable character.
33596 4-data-read-memory bytes+16 x 1 8 4 x
33597 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
33598 next-row="0x000013c0",prev-row="0x0000139c",
33599 next-page="0x000013c0",prev-page="0x00001380",memory=[
33600 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
33601 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
33602 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
33603 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
33604 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
33605 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
33606 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
33607 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
33611 @subheading The @code{-data-read-memory-bytes} Command
33612 @findex -data-read-memory-bytes
33614 @subsubheading Synopsis
33617 -data-read-memory-bytes [ -o @var{byte-offset} ]
33618 @var{address} @var{count}
33625 @item @var{address}
33626 An expression specifying the address of the first memory word to be
33627 read. Complex expressions containing embedded white space should be
33628 quoted using the C convention.
33631 The number of bytes to read. This should be an integer literal.
33633 @item @var{byte-offset}
33634 The offsets in bytes relative to @var{address} at which to start
33635 reading. This should be an integer literal. This option is provided
33636 so that a frontend is not required to first evaluate address and then
33637 perform address arithmetics itself.
33641 This command attempts to read all accessible memory regions in the
33642 specified range. First, all regions marked as unreadable in the memory
33643 map (if one is defined) will be skipped. @xref{Memory Region
33644 Attributes}. Second, @value{GDBN} will attempt to read the remaining
33645 regions. For each one, if reading full region results in an errors,
33646 @value{GDBN} will try to read a subset of the region.
33648 In general, every single byte in the region may be readable or not,
33649 and the only way to read every readable byte is to try a read at
33650 every address, which is not practical. Therefore, @value{GDBN} will
33651 attempt to read all accessible bytes at either beginning or the end
33652 of the region, using a binary division scheme. This heuristic works
33653 well for reading accross a memory map boundary. Note that if a region
33654 has a readable range that is neither at the beginning or the end,
33655 @value{GDBN} will not read it.
33657 The result record (@pxref{GDB/MI Result Records}) that is output of
33658 the command includes a field named @samp{memory} whose content is a
33659 list of tuples. Each tuple represent a successfully read memory block
33660 and has the following fields:
33664 The start address of the memory block, as hexadecimal literal.
33667 The end address of the memory block, as hexadecimal literal.
33670 The offset of the memory block, as hexadecimal literal, relative to
33671 the start address passed to @code{-data-read-memory-bytes}.
33674 The contents of the memory block, in hex.
33680 @subsubheading @value{GDBN} Command
33682 The corresponding @value{GDBN} command is @samp{x}.
33684 @subsubheading Example
33688 -data-read-memory-bytes &a 10
33689 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
33691 contents="01000000020000000300"@}]
33696 @subheading The @code{-data-write-memory-bytes} Command
33697 @findex -data-write-memory-bytes
33699 @subsubheading Synopsis
33702 -data-write-memory-bytes @var{address} @var{contents}
33703 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
33710 @item @var{address}
33711 An expression specifying the address of the first memory word to be
33712 read. Complex expressions containing embedded white space should be
33713 quoted using the C convention.
33715 @item @var{contents}
33716 The hex-encoded bytes to write.
33719 Optional argument indicating the number of bytes to be written. If @var{count}
33720 is greater than @var{contents}' length, @value{GDBN} will repeatedly
33721 write @var{contents} until it fills @var{count} bytes.
33725 @subsubheading @value{GDBN} Command
33727 There's no corresponding @value{GDBN} command.
33729 @subsubheading Example
33733 -data-write-memory-bytes &a "aabbccdd"
33740 -data-write-memory-bytes &a "aabbccdd" 16e
33745 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33746 @node GDB/MI Tracepoint Commands
33747 @section @sc{gdb/mi} Tracepoint Commands
33749 The commands defined in this section implement MI support for
33750 tracepoints. For detailed introduction, see @ref{Tracepoints}.
33752 @subheading The @code{-trace-find} Command
33753 @findex -trace-find
33755 @subsubheading Synopsis
33758 -trace-find @var{mode} [@var{parameters}@dots{}]
33761 Find a trace frame using criteria defined by @var{mode} and
33762 @var{parameters}. The following table lists permissible
33763 modes and their parameters. For details of operation, see @ref{tfind}.
33768 No parameters are required. Stops examining trace frames.
33771 An integer is required as parameter. Selects tracepoint frame with
33774 @item tracepoint-number
33775 An integer is required as parameter. Finds next
33776 trace frame that corresponds to tracepoint with the specified number.
33779 An address is required as parameter. Finds
33780 next trace frame that corresponds to any tracepoint at the specified
33783 @item pc-inside-range
33784 Two addresses are required as parameters. Finds next trace
33785 frame that corresponds to a tracepoint at an address inside the
33786 specified range. Both bounds are considered to be inside the range.
33788 @item pc-outside-range
33789 Two addresses are required as parameters. Finds
33790 next trace frame that corresponds to a tracepoint at an address outside
33791 the specified range. Both bounds are considered to be inside the range.
33794 Line specification is required as parameter. @xref{Specify Location}.
33795 Finds next trace frame that corresponds to a tracepoint at
33796 the specified location.
33800 If @samp{none} was passed as @var{mode}, the response does not
33801 have fields. Otherwise, the response may have the following fields:
33805 This field has either @samp{0} or @samp{1} as the value, depending
33806 on whether a matching tracepoint was found.
33809 The index of the found traceframe. This field is present iff
33810 the @samp{found} field has value of @samp{1}.
33813 The index of the found tracepoint. This field is present iff
33814 the @samp{found} field has value of @samp{1}.
33817 The information about the frame corresponding to the found trace
33818 frame. This field is present only if a trace frame was found.
33819 @xref{GDB/MI Frame Information}, for description of this field.
33823 @subsubheading @value{GDBN} Command
33825 The corresponding @value{GDBN} command is @samp{tfind}.
33827 @subheading -trace-define-variable
33828 @findex -trace-define-variable
33830 @subsubheading Synopsis
33833 -trace-define-variable @var{name} [ @var{value} ]
33836 Create trace variable @var{name} if it does not exist. If
33837 @var{value} is specified, sets the initial value of the specified
33838 trace variable to that value. Note that the @var{name} should start
33839 with the @samp{$} character.
33841 @subsubheading @value{GDBN} Command
33843 The corresponding @value{GDBN} command is @samp{tvariable}.
33845 @subheading The @code{-trace-frame-collected} Command
33846 @findex -trace-frame-collected
33848 @subsubheading Synopsis
33851 -trace-frame-collected
33852 [--var-print-values @var{var_pval}]
33853 [--comp-print-values @var{comp_pval}]
33854 [--registers-format @var{regformat}]
33855 [--memory-contents]
33858 This command returns the set of collected objects, register names,
33859 trace state variable names, memory ranges and computed expressions
33860 that have been collected at a particular trace frame. The optional
33861 parameters to the command affect the output format in different ways.
33862 See the output description table below for more details.
33864 The reported names can be used in the normal manner to create
33865 varobjs and inspect the objects themselves. The items returned by
33866 this command are categorized so that it is clear which is a variable,
33867 which is a register, which is a trace state variable, which is a
33868 memory range and which is a computed expression.
33870 For instance, if the actions were
33872 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
33873 collect *(int*)0xaf02bef0@@40
33877 the object collected in its entirety would be @code{myVar}. The
33878 object @code{myArray} would be partially collected, because only the
33879 element at index @code{myIndex} would be collected. The remaining
33880 objects would be computed expressions.
33882 An example output would be:
33886 -trace-frame-collected
33888 explicit-variables=[@{name="myVar",value="1"@}],
33889 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
33890 @{name="myObj.field",value="0"@},
33891 @{name="myPtr->field",value="1"@},
33892 @{name="myCount + 2",value="3"@},
33893 @{name="$tvar1 + 1",value="43970027"@}],
33894 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
33895 @{number="1",value="0x0"@},
33896 @{number="2",value="0x4"@},
33898 @{number="125",value="0x0"@}],
33899 tvars=[@{name="$tvar1",current="43970026"@}],
33900 memory=[@{address="0x0000000000602264",length="4"@},
33901 @{address="0x0000000000615bc0",length="4"@}]
33908 @item explicit-variables
33909 The set of objects that have been collected in their entirety (as
33910 opposed to collecting just a few elements of an array or a few struct
33911 members). For each object, its name and value are printed.
33912 The @code{--var-print-values} option affects how or whether the value
33913 field is output. If @var{var_pval} is 0, then print only the names;
33914 if it is 1, print also their values; and if it is 2, print the name,
33915 type and value for simple data types, and the name and type for
33916 arrays, structures and unions.
33918 @item computed-expressions
33919 The set of computed expressions that have been collected at the
33920 current trace frame. The @code{--comp-print-values} option affects
33921 this set like the @code{--var-print-values} option affects the
33922 @code{explicit-variables} set. See above.
33925 The registers that have been collected at the current trace frame.
33926 For each register collected, the name and current value are returned.
33927 The value is formatted according to the @code{--registers-format}
33928 option. See the @command{-data-list-register-values} command for a
33929 list of the allowed formats. The default is @samp{x}.
33932 The trace state variables that have been collected at the current
33933 trace frame. For each trace state variable collected, the name and
33934 current value are returned.
33937 The set of memory ranges that have been collected at the current trace
33938 frame. Its content is a list of tuples. Each tuple represents a
33939 collected memory range and has the following fields:
33943 The start address of the memory range, as hexadecimal literal.
33946 The length of the memory range, as decimal literal.
33949 The contents of the memory block, in hex. This field is only present
33950 if the @code{--memory-contents} option is specified.
33956 @subsubheading @value{GDBN} Command
33958 There is no corresponding @value{GDBN} command.
33960 @subsubheading Example
33962 @subheading -trace-list-variables
33963 @findex -trace-list-variables
33965 @subsubheading Synopsis
33968 -trace-list-variables
33971 Return a table of all defined trace variables. Each element of the
33972 table has the following fields:
33976 The name of the trace variable. This field is always present.
33979 The initial value. This is a 64-bit signed integer. This
33980 field is always present.
33983 The value the trace variable has at the moment. This is a 64-bit
33984 signed integer. This field is absent iff current value is
33985 not defined, for example if the trace was never run, or is
33990 @subsubheading @value{GDBN} Command
33992 The corresponding @value{GDBN} command is @samp{tvariables}.
33994 @subsubheading Example
33998 -trace-list-variables
33999 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
34000 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
34001 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
34002 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
34003 body=[variable=@{name="$trace_timestamp",initial="0"@}
34004 variable=@{name="$foo",initial="10",current="15"@}]@}
34008 @subheading -trace-save
34009 @findex -trace-save
34011 @subsubheading Synopsis
34014 -trace-save [-r ] @var{filename}
34017 Saves the collected trace data to @var{filename}. Without the
34018 @samp{-r} option, the data is downloaded from the target and saved
34019 in a local file. With the @samp{-r} option the target is asked
34020 to perform the save.
34022 @subsubheading @value{GDBN} Command
34024 The corresponding @value{GDBN} command is @samp{tsave}.
34027 @subheading -trace-start
34028 @findex -trace-start
34030 @subsubheading Synopsis
34036 Starts a tracing experiments. The result of this command does not
34039 @subsubheading @value{GDBN} Command
34041 The corresponding @value{GDBN} command is @samp{tstart}.
34043 @subheading -trace-status
34044 @findex -trace-status
34046 @subsubheading Synopsis
34052 Obtains the status of a tracing experiment. The result may include
34053 the following fields:
34058 May have a value of either @samp{0}, when no tracing operations are
34059 supported, @samp{1}, when all tracing operations are supported, or
34060 @samp{file} when examining trace file. In the latter case, examining
34061 of trace frame is possible but new tracing experiement cannot be
34062 started. This field is always present.
34065 May have a value of either @samp{0} or @samp{1} depending on whether
34066 tracing experiement is in progress on target. This field is present
34067 if @samp{supported} field is not @samp{0}.
34070 Report the reason why the tracing was stopped last time. This field
34071 may be absent iff tracing was never stopped on target yet. The
34072 value of @samp{request} means the tracing was stopped as result of
34073 the @code{-trace-stop} command. The value of @samp{overflow} means
34074 the tracing buffer is full. The value of @samp{disconnection} means
34075 tracing was automatically stopped when @value{GDBN} has disconnected.
34076 The value of @samp{passcount} means tracing was stopped when a
34077 tracepoint was passed a maximal number of times for that tracepoint.
34078 This field is present if @samp{supported} field is not @samp{0}.
34080 @item stopping-tracepoint
34081 The number of tracepoint whose passcount as exceeded. This field is
34082 present iff the @samp{stop-reason} field has the value of
34086 @itemx frames-created
34087 The @samp{frames} field is a count of the total number of trace frames
34088 in the trace buffer, while @samp{frames-created} is the total created
34089 during the run, including ones that were discarded, such as when a
34090 circular trace buffer filled up. Both fields are optional.
34094 These fields tell the current size of the tracing buffer and the
34095 remaining space. These fields are optional.
34098 The value of the circular trace buffer flag. @code{1} means that the
34099 trace buffer is circular and old trace frames will be discarded if
34100 necessary to make room, @code{0} means that the trace buffer is linear
34104 The value of the disconnected tracing flag. @code{1} means that
34105 tracing will continue after @value{GDBN} disconnects, @code{0} means
34106 that the trace run will stop.
34109 The filename of the trace file being examined. This field is
34110 optional, and only present when examining a trace file.
34114 @subsubheading @value{GDBN} Command
34116 The corresponding @value{GDBN} command is @samp{tstatus}.
34118 @subheading -trace-stop
34119 @findex -trace-stop
34121 @subsubheading Synopsis
34127 Stops a tracing experiment. The result of this command has the same
34128 fields as @code{-trace-status}, except that the @samp{supported} and
34129 @samp{running} fields are not output.
34131 @subsubheading @value{GDBN} Command
34133 The corresponding @value{GDBN} command is @samp{tstop}.
34136 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34137 @node GDB/MI Symbol Query
34138 @section @sc{gdb/mi} Symbol Query Commands
34142 @subheading The @code{-symbol-info-address} Command
34143 @findex -symbol-info-address
34145 @subsubheading Synopsis
34148 -symbol-info-address @var{symbol}
34151 Describe where @var{symbol} is stored.
34153 @subsubheading @value{GDBN} Command
34155 The corresponding @value{GDBN} command is @samp{info address}.
34157 @subsubheading Example
34161 @subheading The @code{-symbol-info-file} Command
34162 @findex -symbol-info-file
34164 @subsubheading Synopsis
34170 Show the file for the symbol.
34172 @subsubheading @value{GDBN} Command
34174 There's no equivalent @value{GDBN} command. @code{gdbtk} has
34175 @samp{gdb_find_file}.
34177 @subsubheading Example
34181 @subheading The @code{-symbol-info-function} Command
34182 @findex -symbol-info-function
34184 @subsubheading Synopsis
34187 -symbol-info-function
34190 Show which function the symbol lives in.
34192 @subsubheading @value{GDBN} Command
34194 @samp{gdb_get_function} in @code{gdbtk}.
34196 @subsubheading Example
34200 @subheading The @code{-symbol-info-line} Command
34201 @findex -symbol-info-line
34203 @subsubheading Synopsis
34209 Show the core addresses of the code for a source line.
34211 @subsubheading @value{GDBN} Command
34213 The corresponding @value{GDBN} command is @samp{info line}.
34214 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
34216 @subsubheading Example
34220 @subheading The @code{-symbol-info-symbol} Command
34221 @findex -symbol-info-symbol
34223 @subsubheading Synopsis
34226 -symbol-info-symbol @var{addr}
34229 Describe what symbol is at location @var{addr}.
34231 @subsubheading @value{GDBN} Command
34233 The corresponding @value{GDBN} command is @samp{info symbol}.
34235 @subsubheading Example
34239 @subheading The @code{-symbol-list-functions} Command
34240 @findex -symbol-list-functions
34242 @subsubheading Synopsis
34245 -symbol-list-functions
34248 List the functions in the executable.
34250 @subsubheading @value{GDBN} Command
34252 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
34253 @samp{gdb_search} in @code{gdbtk}.
34255 @subsubheading Example
34260 @subheading The @code{-symbol-list-lines} Command
34261 @findex -symbol-list-lines
34263 @subsubheading Synopsis
34266 -symbol-list-lines @var{filename}
34269 Print the list of lines that contain code and their associated program
34270 addresses for the given source filename. The entries are sorted in
34271 ascending PC order.
34273 @subsubheading @value{GDBN} Command
34275 There is no corresponding @value{GDBN} command.
34277 @subsubheading Example
34280 -symbol-list-lines basics.c
34281 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
34287 @subheading The @code{-symbol-list-types} Command
34288 @findex -symbol-list-types
34290 @subsubheading Synopsis
34296 List all the type names.
34298 @subsubheading @value{GDBN} Command
34300 The corresponding commands are @samp{info types} in @value{GDBN},
34301 @samp{gdb_search} in @code{gdbtk}.
34303 @subsubheading Example
34307 @subheading The @code{-symbol-list-variables} Command
34308 @findex -symbol-list-variables
34310 @subsubheading Synopsis
34313 -symbol-list-variables
34316 List all the global and static variable names.
34318 @subsubheading @value{GDBN} Command
34320 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
34322 @subsubheading Example
34326 @subheading The @code{-symbol-locate} Command
34327 @findex -symbol-locate
34329 @subsubheading Synopsis
34335 @subsubheading @value{GDBN} Command
34337 @samp{gdb_loc} in @code{gdbtk}.
34339 @subsubheading Example
34343 @subheading The @code{-symbol-type} Command
34344 @findex -symbol-type
34346 @subsubheading Synopsis
34349 -symbol-type @var{variable}
34352 Show type of @var{variable}.
34354 @subsubheading @value{GDBN} Command
34356 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
34357 @samp{gdb_obj_variable}.
34359 @subsubheading Example
34364 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34365 @node GDB/MI File Commands
34366 @section @sc{gdb/mi} File Commands
34368 This section describes the GDB/MI commands to specify executable file names
34369 and to read in and obtain symbol table information.
34371 @subheading The @code{-file-exec-and-symbols} Command
34372 @findex -file-exec-and-symbols
34374 @subsubheading Synopsis
34377 -file-exec-and-symbols @var{file}
34380 Specify the executable file to be debugged. This file is the one from
34381 which the symbol table is also read. If no file is specified, the
34382 command clears the executable and symbol information. If breakpoints
34383 are set when using this command with no arguments, @value{GDBN} will produce
34384 error messages. Otherwise, no output is produced, except a completion
34387 @subsubheading @value{GDBN} Command
34389 The corresponding @value{GDBN} command is @samp{file}.
34391 @subsubheading Example
34395 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
34401 @subheading The @code{-file-exec-file} Command
34402 @findex -file-exec-file
34404 @subsubheading Synopsis
34407 -file-exec-file @var{file}
34410 Specify the executable file to be debugged. Unlike
34411 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
34412 from this file. If used without argument, @value{GDBN} clears the information
34413 about the executable file. No output is produced, except a completion
34416 @subsubheading @value{GDBN} Command
34418 The corresponding @value{GDBN} command is @samp{exec-file}.
34420 @subsubheading Example
34424 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
34431 @subheading The @code{-file-list-exec-sections} Command
34432 @findex -file-list-exec-sections
34434 @subsubheading Synopsis
34437 -file-list-exec-sections
34440 List the sections of the current executable file.
34442 @subsubheading @value{GDBN} Command
34444 The @value{GDBN} command @samp{info file} shows, among the rest, the same
34445 information as this command. @code{gdbtk} has a corresponding command
34446 @samp{gdb_load_info}.
34448 @subsubheading Example
34453 @subheading The @code{-file-list-exec-source-file} Command
34454 @findex -file-list-exec-source-file
34456 @subsubheading Synopsis
34459 -file-list-exec-source-file
34462 List the line number, the current source file, and the absolute path
34463 to the current source file for the current executable. The macro
34464 information field has a value of @samp{1} or @samp{0} depending on
34465 whether or not the file includes preprocessor macro information.
34467 @subsubheading @value{GDBN} Command
34469 The @value{GDBN} equivalent is @samp{info source}
34471 @subsubheading Example
34475 123-file-list-exec-source-file
34476 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
34481 @subheading The @code{-file-list-exec-source-files} Command
34482 @findex -file-list-exec-source-files
34484 @subsubheading Synopsis
34487 -file-list-exec-source-files
34490 List the source files for the current executable.
34492 It will always output both the filename and fullname (absolute file
34493 name) of a source file.
34495 @subsubheading @value{GDBN} Command
34497 The @value{GDBN} equivalent is @samp{info sources}.
34498 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
34500 @subsubheading Example
34503 -file-list-exec-source-files
34505 @{file=foo.c,fullname=/home/foo.c@},
34506 @{file=/home/bar.c,fullname=/home/bar.c@},
34507 @{file=gdb_could_not_find_fullpath.c@}]
34512 @subheading The @code{-file-list-shared-libraries} Command
34513 @findex -file-list-shared-libraries
34515 @subsubheading Synopsis
34518 -file-list-shared-libraries
34521 List the shared libraries in the program.
34523 @subsubheading @value{GDBN} Command
34525 The corresponding @value{GDBN} command is @samp{info shared}.
34527 @subsubheading Example
34531 @subheading The @code{-file-list-symbol-files} Command
34532 @findex -file-list-symbol-files
34534 @subsubheading Synopsis
34537 -file-list-symbol-files
34542 @subsubheading @value{GDBN} Command
34544 The corresponding @value{GDBN} command is @samp{info file} (part of it).
34546 @subsubheading Example
34551 @subheading The @code{-file-symbol-file} Command
34552 @findex -file-symbol-file
34554 @subsubheading Synopsis
34557 -file-symbol-file @var{file}
34560 Read symbol table info from the specified @var{file} argument. When
34561 used without arguments, clears @value{GDBN}'s symbol table info. No output is
34562 produced, except for a completion notification.
34564 @subsubheading @value{GDBN} Command
34566 The corresponding @value{GDBN} command is @samp{symbol-file}.
34568 @subsubheading Example
34572 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
34578 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34579 @node GDB/MI Memory Overlay Commands
34580 @section @sc{gdb/mi} Memory Overlay Commands
34582 The memory overlay commands are not implemented.
34584 @c @subheading -overlay-auto
34586 @c @subheading -overlay-list-mapping-state
34588 @c @subheading -overlay-list-overlays
34590 @c @subheading -overlay-map
34592 @c @subheading -overlay-off
34594 @c @subheading -overlay-on
34596 @c @subheading -overlay-unmap
34598 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34599 @node GDB/MI Signal Handling Commands
34600 @section @sc{gdb/mi} Signal Handling Commands
34602 Signal handling commands are not implemented.
34604 @c @subheading -signal-handle
34606 @c @subheading -signal-list-handle-actions
34608 @c @subheading -signal-list-signal-types
34612 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34613 @node GDB/MI Target Manipulation
34614 @section @sc{gdb/mi} Target Manipulation Commands
34617 @subheading The @code{-target-attach} Command
34618 @findex -target-attach
34620 @subsubheading Synopsis
34623 -target-attach @var{pid} | @var{gid} | @var{file}
34626 Attach to a process @var{pid} or a file @var{file} outside of
34627 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
34628 group, the id previously returned by
34629 @samp{-list-thread-groups --available} must be used.
34631 @subsubheading @value{GDBN} Command
34633 The corresponding @value{GDBN} command is @samp{attach}.
34635 @subsubheading Example
34639 =thread-created,id="1"
34640 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
34646 @subheading The @code{-target-compare-sections} Command
34647 @findex -target-compare-sections
34649 @subsubheading Synopsis
34652 -target-compare-sections [ @var{section} ]
34655 Compare data of section @var{section} on target to the exec file.
34656 Without the argument, all sections are compared.
34658 @subsubheading @value{GDBN} Command
34660 The @value{GDBN} equivalent is @samp{compare-sections}.
34662 @subsubheading Example
34667 @subheading The @code{-target-detach} Command
34668 @findex -target-detach
34670 @subsubheading Synopsis
34673 -target-detach [ @var{pid} | @var{gid} ]
34676 Detach from the remote target which normally resumes its execution.
34677 If either @var{pid} or @var{gid} is specified, detaches from either
34678 the specified process, or specified thread group. There's no output.
34680 @subsubheading @value{GDBN} Command
34682 The corresponding @value{GDBN} command is @samp{detach}.
34684 @subsubheading Example
34694 @subheading The @code{-target-disconnect} Command
34695 @findex -target-disconnect
34697 @subsubheading Synopsis
34703 Disconnect from the remote target. There's no output and the target is
34704 generally not resumed.
34706 @subsubheading @value{GDBN} Command
34708 The corresponding @value{GDBN} command is @samp{disconnect}.
34710 @subsubheading Example
34720 @subheading The @code{-target-download} Command
34721 @findex -target-download
34723 @subsubheading Synopsis
34729 Loads the executable onto the remote target.
34730 It prints out an update message every half second, which includes the fields:
34734 The name of the section.
34736 The size of what has been sent so far for that section.
34738 The size of the section.
34740 The total size of what was sent so far (the current and the previous sections).
34742 The size of the overall executable to download.
34746 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
34747 @sc{gdb/mi} Output Syntax}).
34749 In addition, it prints the name and size of the sections, as they are
34750 downloaded. These messages include the following fields:
34754 The name of the section.
34756 The size of the section.
34758 The size of the overall executable to download.
34762 At the end, a summary is printed.
34764 @subsubheading @value{GDBN} Command
34766 The corresponding @value{GDBN} command is @samp{load}.
34768 @subsubheading Example
34770 Note: each status message appears on a single line. Here the messages
34771 have been broken down so that they can fit onto a page.
34776 +download,@{section=".text",section-size="6668",total-size="9880"@}
34777 +download,@{section=".text",section-sent="512",section-size="6668",
34778 total-sent="512",total-size="9880"@}
34779 +download,@{section=".text",section-sent="1024",section-size="6668",
34780 total-sent="1024",total-size="9880"@}
34781 +download,@{section=".text",section-sent="1536",section-size="6668",
34782 total-sent="1536",total-size="9880"@}
34783 +download,@{section=".text",section-sent="2048",section-size="6668",
34784 total-sent="2048",total-size="9880"@}
34785 +download,@{section=".text",section-sent="2560",section-size="6668",
34786 total-sent="2560",total-size="9880"@}
34787 +download,@{section=".text",section-sent="3072",section-size="6668",
34788 total-sent="3072",total-size="9880"@}
34789 +download,@{section=".text",section-sent="3584",section-size="6668",
34790 total-sent="3584",total-size="9880"@}
34791 +download,@{section=".text",section-sent="4096",section-size="6668",
34792 total-sent="4096",total-size="9880"@}
34793 +download,@{section=".text",section-sent="4608",section-size="6668",
34794 total-sent="4608",total-size="9880"@}
34795 +download,@{section=".text",section-sent="5120",section-size="6668",
34796 total-sent="5120",total-size="9880"@}
34797 +download,@{section=".text",section-sent="5632",section-size="6668",
34798 total-sent="5632",total-size="9880"@}
34799 +download,@{section=".text",section-sent="6144",section-size="6668",
34800 total-sent="6144",total-size="9880"@}
34801 +download,@{section=".text",section-sent="6656",section-size="6668",
34802 total-sent="6656",total-size="9880"@}
34803 +download,@{section=".init",section-size="28",total-size="9880"@}
34804 +download,@{section=".fini",section-size="28",total-size="9880"@}
34805 +download,@{section=".data",section-size="3156",total-size="9880"@}
34806 +download,@{section=".data",section-sent="512",section-size="3156",
34807 total-sent="7236",total-size="9880"@}
34808 +download,@{section=".data",section-sent="1024",section-size="3156",
34809 total-sent="7748",total-size="9880"@}
34810 +download,@{section=".data",section-sent="1536",section-size="3156",
34811 total-sent="8260",total-size="9880"@}
34812 +download,@{section=".data",section-sent="2048",section-size="3156",
34813 total-sent="8772",total-size="9880"@}
34814 +download,@{section=".data",section-sent="2560",section-size="3156",
34815 total-sent="9284",total-size="9880"@}
34816 +download,@{section=".data",section-sent="3072",section-size="3156",
34817 total-sent="9796",total-size="9880"@}
34818 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
34825 @subheading The @code{-target-exec-status} Command
34826 @findex -target-exec-status
34828 @subsubheading Synopsis
34831 -target-exec-status
34834 Provide information on the state of the target (whether it is running or
34835 not, for instance).
34837 @subsubheading @value{GDBN} Command
34839 There's no equivalent @value{GDBN} command.
34841 @subsubheading Example
34845 @subheading The @code{-target-list-available-targets} Command
34846 @findex -target-list-available-targets
34848 @subsubheading Synopsis
34851 -target-list-available-targets
34854 List the possible targets to connect to.
34856 @subsubheading @value{GDBN} Command
34858 The corresponding @value{GDBN} command is @samp{help target}.
34860 @subsubheading Example
34864 @subheading The @code{-target-list-current-targets} Command
34865 @findex -target-list-current-targets
34867 @subsubheading Synopsis
34870 -target-list-current-targets
34873 Describe the current target.
34875 @subsubheading @value{GDBN} Command
34877 The corresponding information is printed by @samp{info file} (among
34880 @subsubheading Example
34884 @subheading The @code{-target-list-parameters} Command
34885 @findex -target-list-parameters
34887 @subsubheading Synopsis
34890 -target-list-parameters
34896 @subsubheading @value{GDBN} Command
34900 @subsubheading Example
34904 @subheading The @code{-target-select} Command
34905 @findex -target-select
34907 @subsubheading Synopsis
34910 -target-select @var{type} @var{parameters @dots{}}
34913 Connect @value{GDBN} to the remote target. This command takes two args:
34917 The type of target, for instance @samp{remote}, etc.
34918 @item @var{parameters}
34919 Device names, host names and the like. @xref{Target Commands, ,
34920 Commands for Managing Targets}, for more details.
34923 The output is a connection notification, followed by the address at
34924 which the target program is, in the following form:
34927 ^connected,addr="@var{address}",func="@var{function name}",
34928 args=[@var{arg list}]
34931 @subsubheading @value{GDBN} Command
34933 The corresponding @value{GDBN} command is @samp{target}.
34935 @subsubheading Example
34939 -target-select remote /dev/ttya
34940 ^connected,addr="0xfe00a300",func="??",args=[]
34944 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34945 @node GDB/MI File Transfer Commands
34946 @section @sc{gdb/mi} File Transfer Commands
34949 @subheading The @code{-target-file-put} Command
34950 @findex -target-file-put
34952 @subsubheading Synopsis
34955 -target-file-put @var{hostfile} @var{targetfile}
34958 Copy file @var{hostfile} from the host system (the machine running
34959 @value{GDBN}) to @var{targetfile} on the target system.
34961 @subsubheading @value{GDBN} Command
34963 The corresponding @value{GDBN} command is @samp{remote put}.
34965 @subsubheading Example
34969 -target-file-put localfile remotefile
34975 @subheading The @code{-target-file-get} Command
34976 @findex -target-file-get
34978 @subsubheading Synopsis
34981 -target-file-get @var{targetfile} @var{hostfile}
34984 Copy file @var{targetfile} from the target system to @var{hostfile}
34985 on the host system.
34987 @subsubheading @value{GDBN} Command
34989 The corresponding @value{GDBN} command is @samp{remote get}.
34991 @subsubheading Example
34995 -target-file-get remotefile localfile
35001 @subheading The @code{-target-file-delete} Command
35002 @findex -target-file-delete
35004 @subsubheading Synopsis
35007 -target-file-delete @var{targetfile}
35010 Delete @var{targetfile} from the target system.
35012 @subsubheading @value{GDBN} Command
35014 The corresponding @value{GDBN} command is @samp{remote delete}.
35016 @subsubheading Example
35020 -target-file-delete remotefile
35026 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35027 @node GDB/MI Ada Exceptions Commands
35028 @section Ada Exceptions @sc{gdb/mi} Commands
35030 @subheading The @code{-info-ada-exceptions} Command
35031 @findex -info-ada-exceptions
35033 @subsubheading Synopsis
35036 -info-ada-exceptions [ @var{regexp}]
35039 List all Ada exceptions defined within the program being debugged.
35040 With a regular expression @var{regexp}, only those exceptions whose
35041 names match @var{regexp} are listed.
35043 @subsubheading @value{GDBN} Command
35045 The corresponding @value{GDBN} command is @samp{info exceptions}.
35047 @subsubheading Result
35049 The result is a table of Ada exceptions. The following columns are
35050 defined for each exception:
35054 The name of the exception.
35057 The address of the exception.
35061 @subsubheading Example
35064 -info-ada-exceptions aint
35065 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
35066 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
35067 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
35068 body=[@{name="constraint_error",address="0x0000000000613da0"@},
35069 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
35072 @subheading Catching Ada Exceptions
35074 The commands describing how to ask @value{GDBN} to stop when a program
35075 raises an exception are described at @ref{Ada Exception GDB/MI
35076 Catchpoint Commands}.
35079 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35080 @node GDB/MI Support Commands
35081 @section @sc{gdb/mi} Support Commands
35083 Since new commands and features get regularly added to @sc{gdb/mi},
35084 some commands are available to help front-ends query the debugger
35085 about support for these capabilities. Similarly, it is also possible
35086 to query @value{GDBN} about target support of certain features.
35088 @subheading The @code{-info-gdb-mi-command} Command
35089 @cindex @code{-info-gdb-mi-command}
35090 @findex -info-gdb-mi-command
35092 @subsubheading Synopsis
35095 -info-gdb-mi-command @var{cmd_name}
35098 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
35100 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
35101 is technically not part of the command name (@pxref{GDB/MI Input
35102 Syntax}), and thus should be omitted in @var{cmd_name}. However,
35103 for ease of use, this command also accepts the form with the leading
35106 @subsubheading @value{GDBN} Command
35108 There is no corresponding @value{GDBN} command.
35110 @subsubheading Result
35112 The result is a tuple. There is currently only one field:
35116 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
35117 @code{"false"} otherwise.
35121 @subsubheading Example
35123 Here is an example where the @sc{gdb/mi} command does not exist:
35126 -info-gdb-mi-command unsupported-command
35127 ^done,command=@{exists="false"@}
35131 And here is an example where the @sc{gdb/mi} command is known
35135 -info-gdb-mi-command symbol-list-lines
35136 ^done,command=@{exists="true"@}
35139 @subheading The @code{-list-features} Command
35140 @findex -list-features
35141 @cindex supported @sc{gdb/mi} features, list
35143 Returns a list of particular features of the MI protocol that
35144 this version of gdb implements. A feature can be a command,
35145 or a new field in an output of some command, or even an
35146 important bugfix. While a frontend can sometimes detect presence
35147 of a feature at runtime, it is easier to perform detection at debugger
35150 The command returns a list of strings, with each string naming an
35151 available feature. Each returned string is just a name, it does not
35152 have any internal structure. The list of possible feature names
35158 (gdb) -list-features
35159 ^done,result=["feature1","feature2"]
35162 The current list of features is:
35165 @item frozen-varobjs
35166 Indicates support for the @code{-var-set-frozen} command, as well
35167 as possible presense of the @code{frozen} field in the output
35168 of @code{-varobj-create}.
35169 @item pending-breakpoints
35170 Indicates support for the @option{-f} option to the @code{-break-insert}
35173 Indicates Python scripting support, Python-based
35174 pretty-printing commands, and possible presence of the
35175 @samp{display_hint} field in the output of @code{-var-list-children}
35177 Indicates support for the @code{-thread-info} command.
35178 @item data-read-memory-bytes
35179 Indicates support for the @code{-data-read-memory-bytes} and the
35180 @code{-data-write-memory-bytes} commands.
35181 @item breakpoint-notifications
35182 Indicates that changes to breakpoints and breakpoints created via the
35183 CLI will be announced via async records.
35184 @item ada-task-info
35185 Indicates support for the @code{-ada-task-info} command.
35186 @item language-option
35187 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
35188 option (@pxref{Context management}).
35189 @item info-gdb-mi-command
35190 Indicates support for the @code{-info-gdb-mi-command} command.
35191 @item undefined-command-error-code
35192 Indicates support for the "undefined-command" error code in error result
35193 records, produced when trying to execute an undefined @sc{gdb/mi} command
35194 (@pxref{GDB/MI Result Records}).
35195 @item exec-run-start-option
35196 Indicates that the @code{-exec-run} command supports the @option{--start}
35197 option (@pxref{GDB/MI Program Execution}).
35200 @subheading The @code{-list-target-features} Command
35201 @findex -list-target-features
35203 Returns a list of particular features that are supported by the
35204 target. Those features affect the permitted MI commands, but
35205 unlike the features reported by the @code{-list-features} command, the
35206 features depend on which target GDB is using at the moment. Whenever
35207 a target can change, due to commands such as @code{-target-select},
35208 @code{-target-attach} or @code{-exec-run}, the list of target features
35209 may change, and the frontend should obtain it again.
35213 (gdb) -list-target-features
35214 ^done,result=["async"]
35217 The current list of features is:
35221 Indicates that the target is capable of asynchronous command
35222 execution, which means that @value{GDBN} will accept further commands
35223 while the target is running.
35226 Indicates that the target is capable of reverse execution.
35227 @xref{Reverse Execution}, for more information.
35231 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35232 @node GDB/MI Miscellaneous Commands
35233 @section Miscellaneous @sc{gdb/mi} Commands
35235 @c @subheading -gdb-complete
35237 @subheading The @code{-gdb-exit} Command
35240 @subsubheading Synopsis
35246 Exit @value{GDBN} immediately.
35248 @subsubheading @value{GDBN} Command
35250 Approximately corresponds to @samp{quit}.
35252 @subsubheading Example
35262 @subheading The @code{-exec-abort} Command
35263 @findex -exec-abort
35265 @subsubheading Synopsis
35271 Kill the inferior running program.
35273 @subsubheading @value{GDBN} Command
35275 The corresponding @value{GDBN} command is @samp{kill}.
35277 @subsubheading Example
35282 @subheading The @code{-gdb-set} Command
35285 @subsubheading Synopsis
35291 Set an internal @value{GDBN} variable.
35292 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
35294 @subsubheading @value{GDBN} Command
35296 The corresponding @value{GDBN} command is @samp{set}.
35298 @subsubheading Example
35308 @subheading The @code{-gdb-show} Command
35311 @subsubheading Synopsis
35317 Show the current value of a @value{GDBN} variable.
35319 @subsubheading @value{GDBN} Command
35321 The corresponding @value{GDBN} command is @samp{show}.
35323 @subsubheading Example
35332 @c @subheading -gdb-source
35335 @subheading The @code{-gdb-version} Command
35336 @findex -gdb-version
35338 @subsubheading Synopsis
35344 Show version information for @value{GDBN}. Used mostly in testing.
35346 @subsubheading @value{GDBN} Command
35348 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
35349 default shows this information when you start an interactive session.
35351 @subsubheading Example
35353 @c This example modifies the actual output from GDB to avoid overfull
35359 ~Copyright 2000 Free Software Foundation, Inc.
35360 ~GDB is free software, covered by the GNU General Public License, and
35361 ~you are welcome to change it and/or distribute copies of it under
35362 ~ certain conditions.
35363 ~Type "show copying" to see the conditions.
35364 ~There is absolutely no warranty for GDB. Type "show warranty" for
35366 ~This GDB was configured as
35367 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
35372 @subheading The @code{-list-thread-groups} Command
35373 @findex -list-thread-groups
35375 @subheading Synopsis
35378 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
35381 Lists thread groups (@pxref{Thread groups}). When a single thread
35382 group is passed as the argument, lists the children of that group.
35383 When several thread group are passed, lists information about those
35384 thread groups. Without any parameters, lists information about all
35385 top-level thread groups.
35387 Normally, thread groups that are being debugged are reported.
35388 With the @samp{--available} option, @value{GDBN} reports thread groups
35389 available on the target.
35391 The output of this command may have either a @samp{threads} result or
35392 a @samp{groups} result. The @samp{thread} result has a list of tuples
35393 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
35394 Information}). The @samp{groups} result has a list of tuples as value,
35395 each tuple describing a thread group. If top-level groups are
35396 requested (that is, no parameter is passed), or when several groups
35397 are passed, the output always has a @samp{groups} result. The format
35398 of the @samp{group} result is described below.
35400 To reduce the number of roundtrips it's possible to list thread groups
35401 together with their children, by passing the @samp{--recurse} option
35402 and the recursion depth. Presently, only recursion depth of 1 is
35403 permitted. If this option is present, then every reported thread group
35404 will also include its children, either as @samp{group} or
35405 @samp{threads} field.
35407 In general, any combination of option and parameters is permitted, with
35408 the following caveats:
35412 When a single thread group is passed, the output will typically
35413 be the @samp{threads} result. Because threads may not contain
35414 anything, the @samp{recurse} option will be ignored.
35417 When the @samp{--available} option is passed, limited information may
35418 be available. In particular, the list of threads of a process might
35419 be inaccessible. Further, specifying specific thread groups might
35420 not give any performance advantage over listing all thread groups.
35421 The frontend should assume that @samp{-list-thread-groups --available}
35422 is always an expensive operation and cache the results.
35426 The @samp{groups} result is a list of tuples, where each tuple may
35427 have the following fields:
35431 Identifier of the thread group. This field is always present.
35432 The identifier is an opaque string; frontends should not try to
35433 convert it to an integer, even though it might look like one.
35436 The type of the thread group. At present, only @samp{process} is a
35440 The target-specific process identifier. This field is only present
35441 for thread groups of type @samp{process} and only if the process exists.
35444 The number of children this thread group has. This field may be
35445 absent for an available thread group.
35448 This field has a list of tuples as value, each tuple describing a
35449 thread. It may be present if the @samp{--recurse} option is
35450 specified, and it's actually possible to obtain the threads.
35453 This field is a list of integers, each identifying a core that one
35454 thread of the group is running on. This field may be absent if
35455 such information is not available.
35458 The name of the executable file that corresponds to this thread group.
35459 The field is only present for thread groups of type @samp{process},
35460 and only if there is a corresponding executable file.
35464 @subheading Example
35468 -list-thread-groups
35469 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
35470 -list-thread-groups 17
35471 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
35472 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
35473 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
35474 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
35475 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
35476 -list-thread-groups --available
35477 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
35478 -list-thread-groups --available --recurse 1
35479 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
35480 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
35481 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
35482 -list-thread-groups --available --recurse 1 17 18
35483 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
35484 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
35485 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
35488 @subheading The @code{-info-os} Command
35491 @subsubheading Synopsis
35494 -info-os [ @var{type} ]
35497 If no argument is supplied, the command returns a table of available
35498 operating-system-specific information types. If one of these types is
35499 supplied as an argument @var{type}, then the command returns a table
35500 of data of that type.
35502 The types of information available depend on the target operating
35505 @subsubheading @value{GDBN} Command
35507 The corresponding @value{GDBN} command is @samp{info os}.
35509 @subsubheading Example
35511 When run on a @sc{gnu}/Linux system, the output will look something
35517 ^done,OSDataTable=@{nr_rows="9",nr_cols="3",
35518 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
35519 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
35520 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
35521 body=[item=@{col0="processes",col1="Listing of all processes",
35522 col2="Processes"@},
35523 item=@{col0="procgroups",col1="Listing of all process groups",
35524 col2="Process groups"@},
35525 item=@{col0="threads",col1="Listing of all threads",
35527 item=@{col0="files",col1="Listing of all file descriptors",
35528 col2="File descriptors"@},
35529 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
35531 item=@{col0="shm",col1="Listing of all shared-memory regions",
35532 col2="Shared-memory regions"@},
35533 item=@{col0="semaphores",col1="Listing of all semaphores",
35534 col2="Semaphores"@},
35535 item=@{col0="msg",col1="Listing of all message queues",
35536 col2="Message queues"@},
35537 item=@{col0="modules",col1="Listing of all loaded kernel modules",
35538 col2="Kernel modules"@}]@}
35541 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
35542 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
35543 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
35544 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
35545 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
35546 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
35547 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
35548 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
35550 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
35551 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
35555 (Note that the MI output here includes a @code{"Title"} column that
35556 does not appear in command-line @code{info os}; this column is useful
35557 for MI clients that want to enumerate the types of data, such as in a
35558 popup menu, but is needless clutter on the command line, and
35559 @code{info os} omits it.)
35561 @subheading The @code{-add-inferior} Command
35562 @findex -add-inferior
35564 @subheading Synopsis
35570 Creates a new inferior (@pxref{Inferiors and Programs}). The created
35571 inferior is not associated with any executable. Such association may
35572 be established with the @samp{-file-exec-and-symbols} command
35573 (@pxref{GDB/MI File Commands}). The command response has a single
35574 field, @samp{inferior}, whose value is the identifier of the
35575 thread group corresponding to the new inferior.
35577 @subheading Example
35582 ^done,inferior="i3"
35585 @subheading The @code{-interpreter-exec} Command
35586 @findex -interpreter-exec
35588 @subheading Synopsis
35591 -interpreter-exec @var{interpreter} @var{command}
35593 @anchor{-interpreter-exec}
35595 Execute the specified @var{command} in the given @var{interpreter}.
35597 @subheading @value{GDBN} Command
35599 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
35601 @subheading Example
35605 -interpreter-exec console "break main"
35606 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
35607 &"During symbol reading, bad structure-type format.\n"
35608 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
35613 @subheading The @code{-inferior-tty-set} Command
35614 @findex -inferior-tty-set
35616 @subheading Synopsis
35619 -inferior-tty-set /dev/pts/1
35622 Set terminal for future runs of the program being debugged.
35624 @subheading @value{GDBN} Command
35626 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
35628 @subheading Example
35632 -inferior-tty-set /dev/pts/1
35637 @subheading The @code{-inferior-tty-show} Command
35638 @findex -inferior-tty-show
35640 @subheading Synopsis
35646 Show terminal for future runs of program being debugged.
35648 @subheading @value{GDBN} Command
35650 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
35652 @subheading Example
35656 -inferior-tty-set /dev/pts/1
35660 ^done,inferior_tty_terminal="/dev/pts/1"
35664 @subheading The @code{-enable-timings} Command
35665 @findex -enable-timings
35667 @subheading Synopsis
35670 -enable-timings [yes | no]
35673 Toggle the printing of the wallclock, user and system times for an MI
35674 command as a field in its output. This command is to help frontend
35675 developers optimize the performance of their code. No argument is
35676 equivalent to @samp{yes}.
35678 @subheading @value{GDBN} Command
35682 @subheading Example
35690 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
35691 addr="0x080484ed",func="main",file="myprog.c",
35692 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
35694 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
35702 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
35703 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
35704 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
35705 fullname="/home/nickrob/myprog.c",line="73"@}
35710 @chapter @value{GDBN} Annotations
35712 This chapter describes annotations in @value{GDBN}. Annotations were
35713 designed to interface @value{GDBN} to graphical user interfaces or other
35714 similar programs which want to interact with @value{GDBN} at a
35715 relatively high level.
35717 The annotation mechanism has largely been superseded by @sc{gdb/mi}
35721 This is Edition @value{EDITION}, @value{DATE}.
35725 * Annotations Overview:: What annotations are; the general syntax.
35726 * Server Prefix:: Issuing a command without affecting user state.
35727 * Prompting:: Annotations marking @value{GDBN}'s need for input.
35728 * Errors:: Annotations for error messages.
35729 * Invalidation:: Some annotations describe things now invalid.
35730 * Annotations for Running::
35731 Whether the program is running, how it stopped, etc.
35732 * Source Annotations:: Annotations describing source code.
35735 @node Annotations Overview
35736 @section What is an Annotation?
35737 @cindex annotations
35739 Annotations start with a newline character, two @samp{control-z}
35740 characters, and the name of the annotation. If there is no additional
35741 information associated with this annotation, the name of the annotation
35742 is followed immediately by a newline. If there is additional
35743 information, the name of the annotation is followed by a space, the
35744 additional information, and a newline. The additional information
35745 cannot contain newline characters.
35747 Any output not beginning with a newline and two @samp{control-z}
35748 characters denotes literal output from @value{GDBN}. Currently there is
35749 no need for @value{GDBN} to output a newline followed by two
35750 @samp{control-z} characters, but if there was such a need, the
35751 annotations could be extended with an @samp{escape} annotation which
35752 means those three characters as output.
35754 The annotation @var{level}, which is specified using the
35755 @option{--annotate} command line option (@pxref{Mode Options}), controls
35756 how much information @value{GDBN} prints together with its prompt,
35757 values of expressions, source lines, and other types of output. Level 0
35758 is for no annotations, level 1 is for use when @value{GDBN} is run as a
35759 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
35760 for programs that control @value{GDBN}, and level 2 annotations have
35761 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
35762 Interface, annotate, GDB's Obsolete Annotations}).
35765 @kindex set annotate
35766 @item set annotate @var{level}
35767 The @value{GDBN} command @code{set annotate} sets the level of
35768 annotations to the specified @var{level}.
35770 @item show annotate
35771 @kindex show annotate
35772 Show the current annotation level.
35775 This chapter describes level 3 annotations.
35777 A simple example of starting up @value{GDBN} with annotations is:
35780 $ @kbd{gdb --annotate=3}
35782 Copyright 2003 Free Software Foundation, Inc.
35783 GDB is free software, covered by the GNU General Public License,
35784 and you are welcome to change it and/or distribute copies of it
35785 under certain conditions.
35786 Type "show copying" to see the conditions.
35787 There is absolutely no warranty for GDB. Type "show warranty"
35789 This GDB was configured as "i386-pc-linux-gnu"
35800 Here @samp{quit} is input to @value{GDBN}; the rest is output from
35801 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
35802 denotes a @samp{control-z} character) are annotations; the rest is
35803 output from @value{GDBN}.
35805 @node Server Prefix
35806 @section The Server Prefix
35807 @cindex server prefix
35809 If you prefix a command with @samp{server } then it will not affect
35810 the command history, nor will it affect @value{GDBN}'s notion of which
35811 command to repeat if @key{RET} is pressed on a line by itself. This
35812 means that commands can be run behind a user's back by a front-end in
35813 a transparent manner.
35815 The @code{server } prefix does not affect the recording of values into
35816 the value history; to print a value without recording it into the
35817 value history, use the @code{output} command instead of the
35818 @code{print} command.
35820 Using this prefix also disables confirmation requests
35821 (@pxref{confirmation requests}).
35824 @section Annotation for @value{GDBN} Input
35826 @cindex annotations for prompts
35827 When @value{GDBN} prompts for input, it annotates this fact so it is possible
35828 to know when to send output, when the output from a given command is
35831 Different kinds of input each have a different @dfn{input type}. Each
35832 input type has three annotations: a @code{pre-} annotation, which
35833 denotes the beginning of any prompt which is being output, a plain
35834 annotation, which denotes the end of the prompt, and then a @code{post-}
35835 annotation which denotes the end of any echo which may (or may not) be
35836 associated with the input. For example, the @code{prompt} input type
35837 features the following annotations:
35845 The input types are
35848 @findex pre-prompt annotation
35849 @findex prompt annotation
35850 @findex post-prompt annotation
35852 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
35854 @findex pre-commands annotation
35855 @findex commands annotation
35856 @findex post-commands annotation
35858 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
35859 command. The annotations are repeated for each command which is input.
35861 @findex pre-overload-choice annotation
35862 @findex overload-choice annotation
35863 @findex post-overload-choice annotation
35864 @item overload-choice
35865 When @value{GDBN} wants the user to select between various overloaded functions.
35867 @findex pre-query annotation
35868 @findex query annotation
35869 @findex post-query annotation
35871 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
35873 @findex pre-prompt-for-continue annotation
35874 @findex prompt-for-continue annotation
35875 @findex post-prompt-for-continue annotation
35876 @item prompt-for-continue
35877 When @value{GDBN} is asking the user to press return to continue. Note: Don't
35878 expect this to work well; instead use @code{set height 0} to disable
35879 prompting. This is because the counting of lines is buggy in the
35880 presence of annotations.
35885 @cindex annotations for errors, warnings and interrupts
35887 @findex quit annotation
35892 This annotation occurs right before @value{GDBN} responds to an interrupt.
35894 @findex error annotation
35899 This annotation occurs right before @value{GDBN} responds to an error.
35901 Quit and error annotations indicate that any annotations which @value{GDBN} was
35902 in the middle of may end abruptly. For example, if a
35903 @code{value-history-begin} annotation is followed by a @code{error}, one
35904 cannot expect to receive the matching @code{value-history-end}. One
35905 cannot expect not to receive it either, however; an error annotation
35906 does not necessarily mean that @value{GDBN} is immediately returning all the way
35909 @findex error-begin annotation
35910 A quit or error annotation may be preceded by
35916 Any output between that and the quit or error annotation is the error
35919 Warning messages are not yet annotated.
35920 @c If we want to change that, need to fix warning(), type_error(),
35921 @c range_error(), and possibly other places.
35924 @section Invalidation Notices
35926 @cindex annotations for invalidation messages
35927 The following annotations say that certain pieces of state may have
35931 @findex frames-invalid annotation
35932 @item ^Z^Zframes-invalid
35934 The frames (for example, output from the @code{backtrace} command) may
35937 @findex breakpoints-invalid annotation
35938 @item ^Z^Zbreakpoints-invalid
35940 The breakpoints may have changed. For example, the user just added or
35941 deleted a breakpoint.
35944 @node Annotations for Running
35945 @section Running the Program
35946 @cindex annotations for running programs
35948 @findex starting annotation
35949 @findex stopping annotation
35950 When the program starts executing due to a @value{GDBN} command such as
35951 @code{step} or @code{continue},
35957 is output. When the program stops,
35963 is output. Before the @code{stopped} annotation, a variety of
35964 annotations describe how the program stopped.
35967 @findex exited annotation
35968 @item ^Z^Zexited @var{exit-status}
35969 The program exited, and @var{exit-status} is the exit status (zero for
35970 successful exit, otherwise nonzero).
35972 @findex signalled annotation
35973 @findex signal-name annotation
35974 @findex signal-name-end annotation
35975 @findex signal-string annotation
35976 @findex signal-string-end annotation
35977 @item ^Z^Zsignalled
35978 The program exited with a signal. After the @code{^Z^Zsignalled}, the
35979 annotation continues:
35985 ^Z^Zsignal-name-end
35989 ^Z^Zsignal-string-end
35994 where @var{name} is the name of the signal, such as @code{SIGILL} or
35995 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
35996 as @code{Illegal Instruction} or @code{Segmentation fault}.
35997 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
35998 user's benefit and have no particular format.
36000 @findex signal annotation
36002 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
36003 just saying that the program received the signal, not that it was
36004 terminated with it.
36006 @findex breakpoint annotation
36007 @item ^Z^Zbreakpoint @var{number}
36008 The program hit breakpoint number @var{number}.
36010 @findex watchpoint annotation
36011 @item ^Z^Zwatchpoint @var{number}
36012 The program hit watchpoint number @var{number}.
36015 @node Source Annotations
36016 @section Displaying Source
36017 @cindex annotations for source display
36019 @findex source annotation
36020 The following annotation is used instead of displaying source code:
36023 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
36026 where @var{filename} is an absolute file name indicating which source
36027 file, @var{line} is the line number within that file (where 1 is the
36028 first line in the file), @var{character} is the character position
36029 within the file (where 0 is the first character in the file) (for most
36030 debug formats this will necessarily point to the beginning of a line),
36031 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
36032 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
36033 @var{addr} is the address in the target program associated with the
36034 source which is being displayed. @var{addr} is in the form @samp{0x}
36035 followed by one or more lowercase hex digits (note that this does not
36036 depend on the language).
36038 @node JIT Interface
36039 @chapter JIT Compilation Interface
36040 @cindex just-in-time compilation
36041 @cindex JIT compilation interface
36043 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
36044 interface. A JIT compiler is a program or library that generates native
36045 executable code at runtime and executes it, usually in order to achieve good
36046 performance while maintaining platform independence.
36048 Programs that use JIT compilation are normally difficult to debug because
36049 portions of their code are generated at runtime, instead of being loaded from
36050 object files, which is where @value{GDBN} normally finds the program's symbols
36051 and debug information. In order to debug programs that use JIT compilation,
36052 @value{GDBN} has an interface that allows the program to register in-memory
36053 symbol files with @value{GDBN} at runtime.
36055 If you are using @value{GDBN} to debug a program that uses this interface, then
36056 it should work transparently so long as you have not stripped the binary. If
36057 you are developing a JIT compiler, then the interface is documented in the rest
36058 of this chapter. At this time, the only known client of this interface is the
36061 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
36062 JIT compiler communicates with @value{GDBN} by writing data into a global
36063 variable and calling a fuction at a well-known symbol. When @value{GDBN}
36064 attaches, it reads a linked list of symbol files from the global variable to
36065 find existing code, and puts a breakpoint in the function so that it can find
36066 out about additional code.
36069 * Declarations:: Relevant C struct declarations
36070 * Registering Code:: Steps to register code
36071 * Unregistering Code:: Steps to unregister code
36072 * Custom Debug Info:: Emit debug information in a custom format
36076 @section JIT Declarations
36078 These are the relevant struct declarations that a C program should include to
36079 implement the interface:
36089 struct jit_code_entry
36091 struct jit_code_entry *next_entry;
36092 struct jit_code_entry *prev_entry;
36093 const char *symfile_addr;
36094 uint64_t symfile_size;
36097 struct jit_descriptor
36100 /* This type should be jit_actions_t, but we use uint32_t
36101 to be explicit about the bitwidth. */
36102 uint32_t action_flag;
36103 struct jit_code_entry *relevant_entry;
36104 struct jit_code_entry *first_entry;
36107 /* GDB puts a breakpoint in this function. */
36108 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
36110 /* Make sure to specify the version statically, because the
36111 debugger may check the version before we can set it. */
36112 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
36115 If the JIT is multi-threaded, then it is important that the JIT synchronize any
36116 modifications to this global data properly, which can easily be done by putting
36117 a global mutex around modifications to these structures.
36119 @node Registering Code
36120 @section Registering Code
36122 To register code with @value{GDBN}, the JIT should follow this protocol:
36126 Generate an object file in memory with symbols and other desired debug
36127 information. The file must include the virtual addresses of the sections.
36130 Create a code entry for the file, which gives the start and size of the symbol
36134 Add it to the linked list in the JIT descriptor.
36137 Point the relevant_entry field of the descriptor at the entry.
36140 Set @code{action_flag} to @code{JIT_REGISTER} and call
36141 @code{__jit_debug_register_code}.
36144 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
36145 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
36146 new code. However, the linked list must still be maintained in order to allow
36147 @value{GDBN} to attach to a running process and still find the symbol files.
36149 @node Unregistering Code
36150 @section Unregistering Code
36152 If code is freed, then the JIT should use the following protocol:
36156 Remove the code entry corresponding to the code from the linked list.
36159 Point the @code{relevant_entry} field of the descriptor at the code entry.
36162 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
36163 @code{__jit_debug_register_code}.
36166 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
36167 and the JIT will leak the memory used for the associated symbol files.
36169 @node Custom Debug Info
36170 @section Custom Debug Info
36171 @cindex custom JIT debug info
36172 @cindex JIT debug info reader
36174 Generating debug information in platform-native file formats (like ELF
36175 or COFF) may be an overkill for JIT compilers; especially if all the
36176 debug info is used for is displaying a meaningful backtrace. The
36177 issue can be resolved by having the JIT writers decide on a debug info
36178 format and also provide a reader that parses the debug info generated
36179 by the JIT compiler. This section gives a brief overview on writing
36180 such a parser. More specific details can be found in the source file
36181 @file{gdb/jit-reader.in}, which is also installed as a header at
36182 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
36184 The reader is implemented as a shared object (so this functionality is
36185 not available on platforms which don't allow loading shared objects at
36186 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
36187 @code{jit-reader-unload} are provided, to be used to load and unload
36188 the readers from a preconfigured directory. Once loaded, the shared
36189 object is used the parse the debug information emitted by the JIT
36193 * Using JIT Debug Info Readers:: How to use supplied readers correctly
36194 * Writing JIT Debug Info Readers:: Creating a debug-info reader
36197 @node Using JIT Debug Info Readers
36198 @subsection Using JIT Debug Info Readers
36199 @kindex jit-reader-load
36200 @kindex jit-reader-unload
36202 Readers can be loaded and unloaded using the @code{jit-reader-load}
36203 and @code{jit-reader-unload} commands.
36206 @item jit-reader-load @var{reader}
36207 Load the JIT reader named @var{reader}. @var{reader} is a shared
36208 object specified as either an absolute or a relative file name. In
36209 the latter case, @value{GDBN} will try to load the reader from a
36210 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
36211 system (here @var{libdir} is the system library directory, often
36212 @file{/usr/local/lib}).
36214 Only one reader can be active at a time; trying to load a second
36215 reader when one is already loaded will result in @value{GDBN}
36216 reporting an error. A new JIT reader can be loaded by first unloading
36217 the current one using @code{jit-reader-unload} and then invoking
36218 @code{jit-reader-load}.
36220 @item jit-reader-unload
36221 Unload the currently loaded JIT reader.
36225 @node Writing JIT Debug Info Readers
36226 @subsection Writing JIT Debug Info Readers
36227 @cindex writing JIT debug info readers
36229 As mentioned, a reader is essentially a shared object conforming to a
36230 certain ABI. This ABI is described in @file{jit-reader.h}.
36232 @file{jit-reader.h} defines the structures, macros and functions
36233 required to write a reader. It is installed (along with
36234 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
36235 the system include directory.
36237 Readers need to be released under a GPL compatible license. A reader
36238 can be declared as released under such a license by placing the macro
36239 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
36241 The entry point for readers is the symbol @code{gdb_init_reader},
36242 which is expected to be a function with the prototype
36244 @findex gdb_init_reader
36246 extern struct gdb_reader_funcs *gdb_init_reader (void);
36249 @cindex @code{struct gdb_reader_funcs}
36251 @code{struct gdb_reader_funcs} contains a set of pointers to callback
36252 functions. These functions are executed to read the debug info
36253 generated by the JIT compiler (@code{read}), to unwind stack frames
36254 (@code{unwind}) and to create canonical frame IDs
36255 (@code{get_Frame_id}). It also has a callback that is called when the
36256 reader is being unloaded (@code{destroy}). The struct looks like this
36259 struct gdb_reader_funcs
36261 /* Must be set to GDB_READER_INTERFACE_VERSION. */
36262 int reader_version;
36264 /* For use by the reader. */
36267 gdb_read_debug_info *read;
36268 gdb_unwind_frame *unwind;
36269 gdb_get_frame_id *get_frame_id;
36270 gdb_destroy_reader *destroy;
36274 @cindex @code{struct gdb_symbol_callbacks}
36275 @cindex @code{struct gdb_unwind_callbacks}
36277 The callbacks are provided with another set of callbacks by
36278 @value{GDBN} to do their job. For @code{read}, these callbacks are
36279 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
36280 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
36281 @code{struct gdb_symbol_callbacks} has callbacks to create new object
36282 files and new symbol tables inside those object files. @code{struct
36283 gdb_unwind_callbacks} has callbacks to read registers off the current
36284 frame and to write out the values of the registers in the previous
36285 frame. Both have a callback (@code{target_read}) to read bytes off the
36286 target's address space.
36288 @node In-Process Agent
36289 @chapter In-Process Agent
36290 @cindex debugging agent
36291 The traditional debugging model is conceptually low-speed, but works fine,
36292 because most bugs can be reproduced in debugging-mode execution. However,
36293 as multi-core or many-core processors are becoming mainstream, and
36294 multi-threaded programs become more and more popular, there should be more
36295 and more bugs that only manifest themselves at normal-mode execution, for
36296 example, thread races, because debugger's interference with the program's
36297 timing may conceal the bugs. On the other hand, in some applications,
36298 it is not feasible for the debugger to interrupt the program's execution
36299 long enough for the developer to learn anything helpful about its behavior.
36300 If the program's correctness depends on its real-time behavior, delays
36301 introduced by a debugger might cause the program to fail, even when the
36302 code itself is correct. It is useful to be able to observe the program's
36303 behavior without interrupting it.
36305 Therefore, traditional debugging model is too intrusive to reproduce
36306 some bugs. In order to reduce the interference with the program, we can
36307 reduce the number of operations performed by debugger. The
36308 @dfn{In-Process Agent}, a shared library, is running within the same
36309 process with inferior, and is able to perform some debugging operations
36310 itself. As a result, debugger is only involved when necessary, and
36311 performance of debugging can be improved accordingly. Note that
36312 interference with program can be reduced but can't be removed completely,
36313 because the in-process agent will still stop or slow down the program.
36315 The in-process agent can interpret and execute Agent Expressions
36316 (@pxref{Agent Expressions}) during performing debugging operations. The
36317 agent expressions can be used for different purposes, such as collecting
36318 data in tracepoints, and condition evaluation in breakpoints.
36320 @anchor{Control Agent}
36321 You can control whether the in-process agent is used as an aid for
36322 debugging with the following commands:
36325 @kindex set agent on
36327 Causes the in-process agent to perform some operations on behalf of the
36328 debugger. Just which operations requested by the user will be done
36329 by the in-process agent depends on the its capabilities. For example,
36330 if you request to evaluate breakpoint conditions in the in-process agent,
36331 and the in-process agent has such capability as well, then breakpoint
36332 conditions will be evaluated in the in-process agent.
36334 @kindex set agent off
36335 @item set agent off
36336 Disables execution of debugging operations by the in-process agent. All
36337 of the operations will be performed by @value{GDBN}.
36341 Display the current setting of execution of debugging operations by
36342 the in-process agent.
36346 * In-Process Agent Protocol::
36349 @node In-Process Agent Protocol
36350 @section In-Process Agent Protocol
36351 @cindex in-process agent protocol
36353 The in-process agent is able to communicate with both @value{GDBN} and
36354 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
36355 used for communications between @value{GDBN} or GDBserver and the IPA.
36356 In general, @value{GDBN} or GDBserver sends commands
36357 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
36358 in-process agent replies back with the return result of the command, or
36359 some other information. The data sent to in-process agent is composed
36360 of primitive data types, such as 4-byte or 8-byte type, and composite
36361 types, which are called objects (@pxref{IPA Protocol Objects}).
36364 * IPA Protocol Objects::
36365 * IPA Protocol Commands::
36368 @node IPA Protocol Objects
36369 @subsection IPA Protocol Objects
36370 @cindex ipa protocol objects
36372 The commands sent to and results received from agent may contain some
36373 complex data types called @dfn{objects}.
36375 The in-process agent is running on the same machine with @value{GDBN}
36376 or GDBserver, so it doesn't have to handle as much differences between
36377 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
36378 However, there are still some differences of two ends in two processes:
36382 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
36383 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
36385 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
36386 GDBserver is compiled with one, and in-process agent is compiled with
36390 Here are the IPA Protocol Objects:
36394 agent expression object. It represents an agent expression
36395 (@pxref{Agent Expressions}).
36396 @anchor{agent expression object}
36398 tracepoint action object. It represents a tracepoint action
36399 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
36400 memory, static trace data and to evaluate expression.
36401 @anchor{tracepoint action object}
36403 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
36404 @anchor{tracepoint object}
36408 The following table describes important attributes of each IPA protocol
36411 @multitable @columnfractions .30 .20 .50
36412 @headitem Name @tab Size @tab Description
36413 @item @emph{agent expression object} @tab @tab
36414 @item length @tab 4 @tab length of bytes code
36415 @item byte code @tab @var{length} @tab contents of byte code
36416 @item @emph{tracepoint action for collecting memory} @tab @tab
36417 @item 'M' @tab 1 @tab type of tracepoint action
36418 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
36419 address of the lowest byte to collect, otherwise @var{addr} is the offset
36420 of @var{basereg} for memory collecting.
36421 @item len @tab 8 @tab length of memory for collecting
36422 @item basereg @tab 4 @tab the register number containing the starting
36423 memory address for collecting.
36424 @item @emph{tracepoint action for collecting registers} @tab @tab
36425 @item 'R' @tab 1 @tab type of tracepoint action
36426 @item @emph{tracepoint action for collecting static trace data} @tab @tab
36427 @item 'L' @tab 1 @tab type of tracepoint action
36428 @item @emph{tracepoint action for expression evaluation} @tab @tab
36429 @item 'X' @tab 1 @tab type of tracepoint action
36430 @item agent expression @tab length of @tab @ref{agent expression object}
36431 @item @emph{tracepoint object} @tab @tab
36432 @item number @tab 4 @tab number of tracepoint
36433 @item address @tab 8 @tab address of tracepoint inserted on
36434 @item type @tab 4 @tab type of tracepoint
36435 @item enabled @tab 1 @tab enable or disable of tracepoint
36436 @item step_count @tab 8 @tab step
36437 @item pass_count @tab 8 @tab pass
36438 @item numactions @tab 4 @tab number of tracepoint actions
36439 @item hit count @tab 8 @tab hit count
36440 @item trace frame usage @tab 8 @tab trace frame usage
36441 @item compiled_cond @tab 8 @tab compiled condition
36442 @item orig_size @tab 8 @tab orig size
36443 @item condition @tab 4 if condition is NULL otherwise length of
36444 @ref{agent expression object}
36445 @tab zero if condition is NULL, otherwise is
36446 @ref{agent expression object}
36447 @item actions @tab variable
36448 @tab numactions number of @ref{tracepoint action object}
36451 @node IPA Protocol Commands
36452 @subsection IPA Protocol Commands
36453 @cindex ipa protocol commands
36455 The spaces in each command are delimiters to ease reading this commands
36456 specification. They don't exist in real commands.
36460 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
36461 Installs a new fast tracepoint described by @var{tracepoint_object}
36462 (@pxref{tracepoint object}). @var{gdb_jump_pad_head}, 8-byte long, is the
36463 head of @dfn{jumppad}, which is used to jump to data collection routine
36468 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
36469 @var{target_address} is address of tracepoint in the inferior.
36470 @var{gdb_jump_pad_head} is updated head of jumppad. Both of
36471 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
36472 @var{fjump} contains a sequence of instructions jump to jumppad entry.
36473 @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
36480 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
36481 is about to kill inferiors.
36489 @item probe_marker_at:@var{address}
36490 Asks in-process agent to probe the marker at @var{address}.
36497 @item unprobe_marker_at:@var{address}
36498 Asks in-process agent to unprobe the marker at @var{address}.
36502 @chapter Reporting Bugs in @value{GDBN}
36503 @cindex bugs in @value{GDBN}
36504 @cindex reporting bugs in @value{GDBN}
36506 Your bug reports play an essential role in making @value{GDBN} reliable.
36508 Reporting a bug may help you by bringing a solution to your problem, or it
36509 may not. But in any case the principal function of a bug report is to help
36510 the entire community by making the next version of @value{GDBN} work better. Bug
36511 reports are your contribution to the maintenance of @value{GDBN}.
36513 In order for a bug report to serve its purpose, you must include the
36514 information that enables us to fix the bug.
36517 * Bug Criteria:: Have you found a bug?
36518 * Bug Reporting:: How to report bugs
36522 @section Have You Found a Bug?
36523 @cindex bug criteria
36525 If you are not sure whether you have found a bug, here are some guidelines:
36528 @cindex fatal signal
36529 @cindex debugger crash
36530 @cindex crash of debugger
36532 If the debugger gets a fatal signal, for any input whatever, that is a
36533 @value{GDBN} bug. Reliable debuggers never crash.
36535 @cindex error on valid input
36537 If @value{GDBN} produces an error message for valid input, that is a
36538 bug. (Note that if you're cross debugging, the problem may also be
36539 somewhere in the connection to the target.)
36541 @cindex invalid input
36543 If @value{GDBN} does not produce an error message for invalid input,
36544 that is a bug. However, you should note that your idea of
36545 ``invalid input'' might be our idea of ``an extension'' or ``support
36546 for traditional practice''.
36549 If you are an experienced user of debugging tools, your suggestions
36550 for improvement of @value{GDBN} are welcome in any case.
36553 @node Bug Reporting
36554 @section How to Report Bugs
36555 @cindex bug reports
36556 @cindex @value{GDBN} bugs, reporting
36558 A number of companies and individuals offer support for @sc{gnu} products.
36559 If you obtained @value{GDBN} from a support organization, we recommend you
36560 contact that organization first.
36562 You can find contact information for many support companies and
36563 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
36565 @c should add a web page ref...
36568 @ifset BUGURL_DEFAULT
36569 In any event, we also recommend that you submit bug reports for
36570 @value{GDBN}. The preferred method is to submit them directly using
36571 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
36572 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
36575 @strong{Do not send bug reports to @samp{info-gdb}, or to
36576 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
36577 not want to receive bug reports. Those that do have arranged to receive
36580 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
36581 serves as a repeater. The mailing list and the newsgroup carry exactly
36582 the same messages. Often people think of posting bug reports to the
36583 newsgroup instead of mailing them. This appears to work, but it has one
36584 problem which can be crucial: a newsgroup posting often lacks a mail
36585 path back to the sender. Thus, if we need to ask for more information,
36586 we may be unable to reach you. For this reason, it is better to send
36587 bug reports to the mailing list.
36589 @ifclear BUGURL_DEFAULT
36590 In any event, we also recommend that you submit bug reports for
36591 @value{GDBN} to @value{BUGURL}.
36595 The fundamental principle of reporting bugs usefully is this:
36596 @strong{report all the facts}. If you are not sure whether to state a
36597 fact or leave it out, state it!
36599 Often people omit facts because they think they know what causes the
36600 problem and assume that some details do not matter. Thus, you might
36601 assume that the name of the variable you use in an example does not matter.
36602 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
36603 stray memory reference which happens to fetch from the location where that
36604 name is stored in memory; perhaps, if the name were different, the contents
36605 of that location would fool the debugger into doing the right thing despite
36606 the bug. Play it safe and give a specific, complete example. That is the
36607 easiest thing for you to do, and the most helpful.
36609 Keep in mind that the purpose of a bug report is to enable us to fix the
36610 bug. It may be that the bug has been reported previously, but neither
36611 you nor we can know that unless your bug report is complete and
36614 Sometimes people give a few sketchy facts and ask, ``Does this ring a
36615 bell?'' Those bug reports are useless, and we urge everyone to
36616 @emph{refuse to respond to them} except to chide the sender to report
36619 To enable us to fix the bug, you should include all these things:
36623 The version of @value{GDBN}. @value{GDBN} announces it if you start
36624 with no arguments; you can also print it at any time using @code{show
36627 Without this, we will not know whether there is any point in looking for
36628 the bug in the current version of @value{GDBN}.
36631 The type of machine you are using, and the operating system name and
36635 The details of the @value{GDBN} build-time configuration.
36636 @value{GDBN} shows these details if you invoke it with the
36637 @option{--configuration} command-line option, or if you type
36638 @code{show configuration} at @value{GDBN}'s prompt.
36641 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
36642 ``@value{GCC}--2.8.1''.
36645 What compiler (and its version) was used to compile the program you are
36646 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
36647 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
36648 to get this information; for other compilers, see the documentation for
36652 The command arguments you gave the compiler to compile your example and
36653 observe the bug. For example, did you use @samp{-O}? To guarantee
36654 you will not omit something important, list them all. A copy of the
36655 Makefile (or the output from make) is sufficient.
36657 If we were to try to guess the arguments, we would probably guess wrong
36658 and then we might not encounter the bug.
36661 A complete input script, and all necessary source files, that will
36665 A description of what behavior you observe that you believe is
36666 incorrect. For example, ``It gets a fatal signal.''
36668 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
36669 will certainly notice it. But if the bug is incorrect output, we might
36670 not notice unless it is glaringly wrong. You might as well not give us
36671 a chance to make a mistake.
36673 Even if the problem you experience is a fatal signal, you should still
36674 say so explicitly. Suppose something strange is going on, such as, your
36675 copy of @value{GDBN} is out of synch, or you have encountered a bug in
36676 the C library on your system. (This has happened!) Your copy might
36677 crash and ours would not. If you told us to expect a crash, then when
36678 ours fails to crash, we would know that the bug was not happening for
36679 us. If you had not told us to expect a crash, then we would not be able
36680 to draw any conclusion from our observations.
36683 @cindex recording a session script
36684 To collect all this information, you can use a session recording program
36685 such as @command{script}, which is available on many Unix systems.
36686 Just run your @value{GDBN} session inside @command{script} and then
36687 include the @file{typescript} file with your bug report.
36689 Another way to record a @value{GDBN} session is to run @value{GDBN}
36690 inside Emacs and then save the entire buffer to a file.
36693 If you wish to suggest changes to the @value{GDBN} source, send us context
36694 diffs. If you even discuss something in the @value{GDBN} source, refer to
36695 it by context, not by line number.
36697 The line numbers in our development sources will not match those in your
36698 sources. Your line numbers would convey no useful information to us.
36702 Here are some things that are not necessary:
36706 A description of the envelope of the bug.
36708 Often people who encounter a bug spend a lot of time investigating
36709 which changes to the input file will make the bug go away and which
36710 changes will not affect it.
36712 This is often time consuming and not very useful, because the way we
36713 will find the bug is by running a single example under the debugger
36714 with breakpoints, not by pure deduction from a series of examples.
36715 We recommend that you save your time for something else.
36717 Of course, if you can find a simpler example to report @emph{instead}
36718 of the original one, that is a convenience for us. Errors in the
36719 output will be easier to spot, running under the debugger will take
36720 less time, and so on.
36722 However, simplification is not vital; if you do not want to do this,
36723 report the bug anyway and send us the entire test case you used.
36726 A patch for the bug.
36728 A patch for the bug does help us if it is a good one. But do not omit
36729 the necessary information, such as the test case, on the assumption that
36730 a patch is all we need. We might see problems with your patch and decide
36731 to fix the problem another way, or we might not understand it at all.
36733 Sometimes with a program as complicated as @value{GDBN} it is very hard to
36734 construct an example that will make the program follow a certain path
36735 through the code. If you do not send us the example, we will not be able
36736 to construct one, so we will not be able to verify that the bug is fixed.
36738 And if we cannot understand what bug you are trying to fix, or why your
36739 patch should be an improvement, we will not install it. A test case will
36740 help us to understand.
36743 A guess about what the bug is or what it depends on.
36745 Such guesses are usually wrong. Even we cannot guess right about such
36746 things without first using the debugger to find the facts.
36749 @c The readline documentation is distributed with the readline code
36750 @c and consists of the two following files:
36753 @c Use -I with makeinfo to point to the appropriate directory,
36754 @c environment var TEXINPUTS with TeX.
36755 @ifclear SYSTEM_READLINE
36756 @include rluser.texi
36757 @include hsuser.texi
36761 @appendix In Memoriam
36763 The @value{GDBN} project mourns the loss of the following long-time
36768 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
36769 to Free Software in general. Outside of @value{GDBN}, he was known in
36770 the Amiga world for his series of Fish Disks, and the GeekGadget project.
36772 @item Michael Snyder
36773 Michael was one of the Global Maintainers of the @value{GDBN} project,
36774 with contributions recorded as early as 1996, until 2011. In addition
36775 to his day to day participation, he was a large driving force behind
36776 adding Reverse Debugging to @value{GDBN}.
36779 Beyond their technical contributions to the project, they were also
36780 enjoyable members of the Free Software Community. We will miss them.
36782 @node Formatting Documentation
36783 @appendix Formatting Documentation
36785 @cindex @value{GDBN} reference card
36786 @cindex reference card
36787 The @value{GDBN} 4 release includes an already-formatted reference card, ready
36788 for printing with PostScript or Ghostscript, in the @file{gdb}
36789 subdirectory of the main source directory@footnote{In
36790 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
36791 release.}. If you can use PostScript or Ghostscript with your printer,
36792 you can print the reference card immediately with @file{refcard.ps}.
36794 The release also includes the source for the reference card. You
36795 can format it, using @TeX{}, by typing:
36801 The @value{GDBN} reference card is designed to print in @dfn{landscape}
36802 mode on US ``letter'' size paper;
36803 that is, on a sheet 11 inches wide by 8.5 inches
36804 high. You will need to specify this form of printing as an option to
36805 your @sc{dvi} output program.
36807 @cindex documentation
36809 All the documentation for @value{GDBN} comes as part of the machine-readable
36810 distribution. The documentation is written in Texinfo format, which is
36811 a documentation system that uses a single source file to produce both
36812 on-line information and a printed manual. You can use one of the Info
36813 formatting commands to create the on-line version of the documentation
36814 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
36816 @value{GDBN} includes an already formatted copy of the on-line Info
36817 version of this manual in the @file{gdb} subdirectory. The main Info
36818 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
36819 subordinate files matching @samp{gdb.info*} in the same directory. If
36820 necessary, you can print out these files, or read them with any editor;
36821 but they are easier to read using the @code{info} subsystem in @sc{gnu}
36822 Emacs or the standalone @code{info} program, available as part of the
36823 @sc{gnu} Texinfo distribution.
36825 If you want to format these Info files yourself, you need one of the
36826 Info formatting programs, such as @code{texinfo-format-buffer} or
36829 If you have @code{makeinfo} installed, and are in the top level
36830 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
36831 version @value{GDBVN}), you can make the Info file by typing:
36838 If you want to typeset and print copies of this manual, you need @TeX{},
36839 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
36840 Texinfo definitions file.
36842 @TeX{} is a typesetting program; it does not print files directly, but
36843 produces output files called @sc{dvi} files. To print a typeset
36844 document, you need a program to print @sc{dvi} files. If your system
36845 has @TeX{} installed, chances are it has such a program. The precise
36846 command to use depends on your system; @kbd{lpr -d} is common; another
36847 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
36848 require a file name without any extension or a @samp{.dvi} extension.
36850 @TeX{} also requires a macro definitions file called
36851 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
36852 written in Texinfo format. On its own, @TeX{} cannot either read or
36853 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
36854 and is located in the @file{gdb-@var{version-number}/texinfo}
36857 If you have @TeX{} and a @sc{dvi} printer program installed, you can
36858 typeset and print this manual. First switch to the @file{gdb}
36859 subdirectory of the main source directory (for example, to
36860 @file{gdb-@value{GDBVN}/gdb}) and type:
36866 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
36868 @node Installing GDB
36869 @appendix Installing @value{GDBN}
36870 @cindex installation
36873 * Requirements:: Requirements for building @value{GDBN}
36874 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
36875 * Separate Objdir:: Compiling @value{GDBN} in another directory
36876 * Config Names:: Specifying names for hosts and targets
36877 * Configure Options:: Summary of options for configure
36878 * System-wide configuration:: Having a system-wide init file
36882 @section Requirements for Building @value{GDBN}
36883 @cindex building @value{GDBN}, requirements for
36885 Building @value{GDBN} requires various tools and packages to be available.
36886 Other packages will be used only if they are found.
36888 @heading Tools/Packages Necessary for Building @value{GDBN}
36890 @item ISO C90 compiler
36891 @value{GDBN} is written in ISO C90. It should be buildable with any
36892 working C90 compiler, e.g.@: GCC.
36896 @heading Tools/Packages Optional for Building @value{GDBN}
36900 @value{GDBN} can use the Expat XML parsing library. This library may be
36901 included with your operating system distribution; if it is not, you
36902 can get the latest version from @url{http://expat.sourceforge.net}.
36903 The @file{configure} script will search for this library in several
36904 standard locations; if it is installed in an unusual path, you can
36905 use the @option{--with-libexpat-prefix} option to specify its location.
36911 Remote protocol memory maps (@pxref{Memory Map Format})
36913 Target descriptions (@pxref{Target Descriptions})
36915 Remote shared library lists (@xref{Library List Format},
36916 or alternatively @pxref{Library List Format for SVR4 Targets})
36918 MS-Windows shared libraries (@pxref{Shared Libraries})
36920 Traceframe info (@pxref{Traceframe Info Format})
36922 Branch trace (@pxref{Branch Trace Format})
36926 @cindex compressed debug sections
36927 @value{GDBN} will use the @samp{zlib} library, if available, to read
36928 compressed debug sections. Some linkers, such as GNU gold, are capable
36929 of producing binaries with compressed debug sections. If @value{GDBN}
36930 is compiled with @samp{zlib}, it will be able to read the debug
36931 information in such binaries.
36933 The @samp{zlib} library is likely included with your operating system
36934 distribution; if it is not, you can get the latest version from
36935 @url{http://zlib.net}.
36938 @value{GDBN}'s features related to character sets (@pxref{Character
36939 Sets}) require a functioning @code{iconv} implementation. If you are
36940 on a GNU system, then this is provided by the GNU C Library. Some
36941 other systems also provide a working @code{iconv}.
36943 If @value{GDBN} is using the @code{iconv} program which is installed
36944 in a non-standard place, you will need to tell @value{GDBN} where to find it.
36945 This is done with @option{--with-iconv-bin} which specifies the
36946 directory that contains the @code{iconv} program.
36948 On systems without @code{iconv}, you can install GNU Libiconv. If you
36949 have previously installed Libiconv, you can use the
36950 @option{--with-libiconv-prefix} option to configure.
36952 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
36953 arrange to build Libiconv if a directory named @file{libiconv} appears
36954 in the top-most source directory. If Libiconv is built this way, and
36955 if the operating system does not provide a suitable @code{iconv}
36956 implementation, then the just-built library will automatically be used
36957 by @value{GDBN}. One easy way to set this up is to download GNU
36958 Libiconv, unpack it, and then rename the directory holding the
36959 Libiconv source code to @samp{libiconv}.
36962 @node Running Configure
36963 @section Invoking the @value{GDBN} @file{configure} Script
36964 @cindex configuring @value{GDBN}
36965 @value{GDBN} comes with a @file{configure} script that automates the process
36966 of preparing @value{GDBN} for installation; you can then use @code{make} to
36967 build the @code{gdb} program.
36969 @c irrelevant in info file; it's as current as the code it lives with.
36970 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
36971 look at the @file{README} file in the sources; we may have improved the
36972 installation procedures since publishing this manual.}
36975 The @value{GDBN} distribution includes all the source code you need for
36976 @value{GDBN} in a single directory, whose name is usually composed by
36977 appending the version number to @samp{gdb}.
36979 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
36980 @file{gdb-@value{GDBVN}} directory. That directory contains:
36983 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
36984 script for configuring @value{GDBN} and all its supporting libraries
36986 @item gdb-@value{GDBVN}/gdb
36987 the source specific to @value{GDBN} itself
36989 @item gdb-@value{GDBVN}/bfd
36990 source for the Binary File Descriptor library
36992 @item gdb-@value{GDBVN}/include
36993 @sc{gnu} include files
36995 @item gdb-@value{GDBVN}/libiberty
36996 source for the @samp{-liberty} free software library
36998 @item gdb-@value{GDBVN}/opcodes
36999 source for the library of opcode tables and disassemblers
37001 @item gdb-@value{GDBVN}/readline
37002 source for the @sc{gnu} command-line interface
37004 @item gdb-@value{GDBVN}/glob
37005 source for the @sc{gnu} filename pattern-matching subroutine
37007 @item gdb-@value{GDBVN}/mmalloc
37008 source for the @sc{gnu} memory-mapped malloc package
37011 The simplest way to configure and build @value{GDBN} is to run @file{configure}
37012 from the @file{gdb-@var{version-number}} source directory, which in
37013 this example is the @file{gdb-@value{GDBVN}} directory.
37015 First switch to the @file{gdb-@var{version-number}} source directory
37016 if you are not already in it; then run @file{configure}. Pass the
37017 identifier for the platform on which @value{GDBN} will run as an
37023 cd gdb-@value{GDBVN}
37024 ./configure @var{host}
37029 where @var{host} is an identifier such as @samp{sun4} or
37030 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
37031 (You can often leave off @var{host}; @file{configure} tries to guess the
37032 correct value by examining your system.)
37034 Running @samp{configure @var{host}} and then running @code{make} builds the
37035 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
37036 libraries, then @code{gdb} itself. The configured source files, and the
37037 binaries, are left in the corresponding source directories.
37040 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
37041 system does not recognize this automatically when you run a different
37042 shell, you may need to run @code{sh} on it explicitly:
37045 sh configure @var{host}
37048 If you run @file{configure} from a directory that contains source
37049 directories for multiple libraries or programs, such as the
37050 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
37052 creates configuration files for every directory level underneath (unless
37053 you tell it not to, with the @samp{--norecursion} option).
37055 You should run the @file{configure} script from the top directory in the
37056 source tree, the @file{gdb-@var{version-number}} directory. If you run
37057 @file{configure} from one of the subdirectories, you will configure only
37058 that subdirectory. That is usually not what you want. In particular,
37059 if you run the first @file{configure} from the @file{gdb} subdirectory
37060 of the @file{gdb-@var{version-number}} directory, you will omit the
37061 configuration of @file{bfd}, @file{readline}, and other sibling
37062 directories of the @file{gdb} subdirectory. This leads to build errors
37063 about missing include files such as @file{bfd/bfd.h}.
37065 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
37066 However, you should make sure that the shell on your path (named by
37067 the @samp{SHELL} environment variable) is publicly readable. Remember
37068 that @value{GDBN} uses the shell to start your program---some systems refuse to
37069 let @value{GDBN} debug child processes whose programs are not readable.
37071 @node Separate Objdir
37072 @section Compiling @value{GDBN} in Another Directory
37074 If you want to run @value{GDBN} versions for several host or target machines,
37075 you need a different @code{gdb} compiled for each combination of
37076 host and target. @file{configure} is designed to make this easy by
37077 allowing you to generate each configuration in a separate subdirectory,
37078 rather than in the source directory. If your @code{make} program
37079 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
37080 @code{make} in each of these directories builds the @code{gdb}
37081 program specified there.
37083 To build @code{gdb} in a separate directory, run @file{configure}
37084 with the @samp{--srcdir} option to specify where to find the source.
37085 (You also need to specify a path to find @file{configure}
37086 itself from your working directory. If the path to @file{configure}
37087 would be the same as the argument to @samp{--srcdir}, you can leave out
37088 the @samp{--srcdir} option; it is assumed.)
37090 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
37091 separate directory for a Sun 4 like this:
37095 cd gdb-@value{GDBVN}
37098 ../gdb-@value{GDBVN}/configure sun4
37103 When @file{configure} builds a configuration using a remote source
37104 directory, it creates a tree for the binaries with the same structure
37105 (and using the same names) as the tree under the source directory. In
37106 the example, you'd find the Sun 4 library @file{libiberty.a} in the
37107 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
37108 @file{gdb-sun4/gdb}.
37110 Make sure that your path to the @file{configure} script has just one
37111 instance of @file{gdb} in it. If your path to @file{configure} looks
37112 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
37113 one subdirectory of @value{GDBN}, not the whole package. This leads to
37114 build errors about missing include files such as @file{bfd/bfd.h}.
37116 One popular reason to build several @value{GDBN} configurations in separate
37117 directories is to configure @value{GDBN} for cross-compiling (where
37118 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
37119 programs that run on another machine---the @dfn{target}).
37120 You specify a cross-debugging target by
37121 giving the @samp{--target=@var{target}} option to @file{configure}.
37123 When you run @code{make} to build a program or library, you must run
37124 it in a configured directory---whatever directory you were in when you
37125 called @file{configure} (or one of its subdirectories).
37127 The @code{Makefile} that @file{configure} generates in each source
37128 directory also runs recursively. If you type @code{make} in a source
37129 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
37130 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
37131 will build all the required libraries, and then build GDB.
37133 When you have multiple hosts or targets configured in separate
37134 directories, you can run @code{make} on them in parallel (for example,
37135 if they are NFS-mounted on each of the hosts); they will not interfere
37139 @section Specifying Names for Hosts and Targets
37141 The specifications used for hosts and targets in the @file{configure}
37142 script are based on a three-part naming scheme, but some short predefined
37143 aliases are also supported. The full naming scheme encodes three pieces
37144 of information in the following pattern:
37147 @var{architecture}-@var{vendor}-@var{os}
37150 For example, you can use the alias @code{sun4} as a @var{host} argument,
37151 or as the value for @var{target} in a @code{--target=@var{target}}
37152 option. The equivalent full name is @samp{sparc-sun-sunos4}.
37154 The @file{configure} script accompanying @value{GDBN} does not provide
37155 any query facility to list all supported host and target names or
37156 aliases. @file{configure} calls the Bourne shell script
37157 @code{config.sub} to map abbreviations to full names; you can read the
37158 script, if you wish, or you can use it to test your guesses on
37159 abbreviations---for example:
37162 % sh config.sub i386-linux
37164 % sh config.sub alpha-linux
37165 alpha-unknown-linux-gnu
37166 % sh config.sub hp9k700
37168 % sh config.sub sun4
37169 sparc-sun-sunos4.1.1
37170 % sh config.sub sun3
37171 m68k-sun-sunos4.1.1
37172 % sh config.sub i986v
37173 Invalid configuration `i986v': machine `i986v' not recognized
37177 @code{config.sub} is also distributed in the @value{GDBN} source
37178 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
37180 @node Configure Options
37181 @section @file{configure} Options
37183 Here is a summary of the @file{configure} options and arguments that
37184 are most often useful for building @value{GDBN}. @file{configure} also has
37185 several other options not listed here. @inforef{What Configure
37186 Does,,configure.info}, for a full explanation of @file{configure}.
37189 configure @r{[}--help@r{]}
37190 @r{[}--prefix=@var{dir}@r{]}
37191 @r{[}--exec-prefix=@var{dir}@r{]}
37192 @r{[}--srcdir=@var{dirname}@r{]}
37193 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
37194 @r{[}--target=@var{target}@r{]}
37199 You may introduce options with a single @samp{-} rather than
37200 @samp{--} if you prefer; but you may abbreviate option names if you use
37205 Display a quick summary of how to invoke @file{configure}.
37207 @item --prefix=@var{dir}
37208 Configure the source to install programs and files under directory
37211 @item --exec-prefix=@var{dir}
37212 Configure the source to install programs under directory
37215 @c avoid splitting the warning from the explanation:
37217 @item --srcdir=@var{dirname}
37218 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
37219 @code{make} that implements the @code{VPATH} feature.}@*
37220 Use this option to make configurations in directories separate from the
37221 @value{GDBN} source directories. Among other things, you can use this to
37222 build (or maintain) several configurations simultaneously, in separate
37223 directories. @file{configure} writes configuration-specific files in
37224 the current directory, but arranges for them to use the source in the
37225 directory @var{dirname}. @file{configure} creates directories under
37226 the working directory in parallel to the source directories below
37229 @item --norecursion
37230 Configure only the directory level where @file{configure} is executed; do not
37231 propagate configuration to subdirectories.
37233 @item --target=@var{target}
37234 Configure @value{GDBN} for cross-debugging programs running on the specified
37235 @var{target}. Without this option, @value{GDBN} is configured to debug
37236 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
37238 There is no convenient way to generate a list of all available targets.
37240 @item @var{host} @dots{}
37241 Configure @value{GDBN} to run on the specified @var{host}.
37243 There is no convenient way to generate a list of all available hosts.
37246 There are many other options available as well, but they are generally
37247 needed for special purposes only.
37249 @node System-wide configuration
37250 @section System-wide configuration and settings
37251 @cindex system-wide init file
37253 @value{GDBN} can be configured to have a system-wide init file;
37254 this file will be read and executed at startup (@pxref{Startup, , What
37255 @value{GDBN} does during startup}).
37257 Here is the corresponding configure option:
37260 @item --with-system-gdbinit=@var{file}
37261 Specify that the default location of the system-wide init file is
37265 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
37266 it may be subject to relocation. Two possible cases:
37270 If the default location of this init file contains @file{$prefix},
37271 it will be subject to relocation. Suppose that the configure options
37272 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
37273 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
37274 init file is looked for as @file{$install/etc/gdbinit} instead of
37275 @file{$prefix/etc/gdbinit}.
37278 By contrast, if the default location does not contain the prefix,
37279 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
37280 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
37281 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
37282 wherever @value{GDBN} is installed.
37285 If the configured location of the system-wide init file (as given by the
37286 @option{--with-system-gdbinit} option at configure time) is in the
37287 data-directory (as specified by @option{--with-gdb-datadir} at configure
37288 time) or in one of its subdirectories, then @value{GDBN} will look for the
37289 system-wide init file in the directory specified by the
37290 @option{--data-directory} command-line option.
37291 Note that the system-wide init file is only read once, during @value{GDBN}
37292 initialization. If the data-directory is changed after @value{GDBN} has
37293 started with the @code{set data-directory} command, the file will not be
37297 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
37300 @node System-wide Configuration Scripts
37301 @subsection Installed System-wide Configuration Scripts
37302 @cindex system-wide configuration scripts
37304 The @file{system-gdbinit} directory, located inside the data-directory
37305 (as specified by @option{--with-gdb-datadir} at configure time) contains
37306 a number of scripts which can be used as system-wide init files. To
37307 automatically source those scripts at startup, @value{GDBN} should be
37308 configured with @option{--with-system-gdbinit}. Otherwise, any user
37309 should be able to source them by hand as needed.
37311 The following scripts are currently available:
37314 @item @file{elinos.py}
37316 @cindex ELinOS system-wide configuration script
37317 This script is useful when debugging a program on an ELinOS target.
37318 It takes advantage of the environment variables defined in a standard
37319 ELinOS environment in order to determine the location of the system
37320 shared libraries, and then sets the @samp{solib-absolute-prefix}
37321 and @samp{solib-search-path} variables appropriately.
37323 @item @file{wrs-linux.py}
37324 @pindex wrs-linux.py
37325 @cindex Wind River Linux system-wide configuration script
37326 This script is useful when debugging a program on a target running
37327 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
37328 the host-side sysroot used by the target system.
37332 @node Maintenance Commands
37333 @appendix Maintenance Commands
37334 @cindex maintenance commands
37335 @cindex internal commands
37337 In addition to commands intended for @value{GDBN} users, @value{GDBN}
37338 includes a number of commands intended for @value{GDBN} developers,
37339 that are not documented elsewhere in this manual. These commands are
37340 provided here for reference. (For commands that turn on debugging
37341 messages, see @ref{Debugging Output}.)
37344 @kindex maint agent
37345 @kindex maint agent-eval
37346 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
37347 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
37348 Translate the given @var{expression} into remote agent bytecodes.
37349 This command is useful for debugging the Agent Expression mechanism
37350 (@pxref{Agent Expressions}). The @samp{agent} version produces an
37351 expression useful for data collection, such as by tracepoints, while
37352 @samp{maint agent-eval} produces an expression that evaluates directly
37353 to a result. For instance, a collection expression for @code{globa +
37354 globb} will include bytecodes to record four bytes of memory at each
37355 of the addresses of @code{globa} and @code{globb}, while discarding
37356 the result of the addition, while an evaluation expression will do the
37357 addition and return the sum.
37358 If @code{-at} is given, generate remote agent bytecode for @var{location}.
37359 If not, generate remote agent bytecode for current frame PC address.
37361 @kindex maint agent-printf
37362 @item maint agent-printf @var{format},@var{expr},...
37363 Translate the given format string and list of argument expressions
37364 into remote agent bytecodes and display them as a disassembled list.
37365 This command is useful for debugging the agent version of dynamic
37366 printf (@pxref{Dynamic Printf}).
37368 @kindex maint info breakpoints
37369 @item @anchor{maint info breakpoints}maint info breakpoints
37370 Using the same format as @samp{info breakpoints}, display both the
37371 breakpoints you've set explicitly, and those @value{GDBN} is using for
37372 internal purposes. Internal breakpoints are shown with negative
37373 breakpoint numbers. The type column identifies what kind of breakpoint
37378 Normal, explicitly set breakpoint.
37381 Normal, explicitly set watchpoint.
37384 Internal breakpoint, used to handle correctly stepping through
37385 @code{longjmp} calls.
37387 @item longjmp resume
37388 Internal breakpoint at the target of a @code{longjmp}.
37391 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
37394 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
37397 Shared library events.
37401 @kindex maint info bfds
37402 @item maint info bfds
37403 This prints information about each @code{bfd} object that is known to
37404 @value{GDBN}. @xref{Top, , BFD, bfd, The Binary File Descriptor Library}.
37406 @kindex set displaced-stepping
37407 @kindex show displaced-stepping
37408 @cindex displaced stepping support
37409 @cindex out-of-line single-stepping
37410 @item set displaced-stepping
37411 @itemx show displaced-stepping
37412 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
37413 if the target supports it. Displaced stepping is a way to single-step
37414 over breakpoints without removing them from the inferior, by executing
37415 an out-of-line copy of the instruction that was originally at the
37416 breakpoint location. It is also known as out-of-line single-stepping.
37419 @item set displaced-stepping on
37420 If the target architecture supports it, @value{GDBN} will use
37421 displaced stepping to step over breakpoints.
37423 @item set displaced-stepping off
37424 @value{GDBN} will not use displaced stepping to step over breakpoints,
37425 even if such is supported by the target architecture.
37427 @cindex non-stop mode, and @samp{set displaced-stepping}
37428 @item set displaced-stepping auto
37429 This is the default mode. @value{GDBN} will use displaced stepping
37430 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
37431 architecture supports displaced stepping.
37434 @kindex maint check-psymtabs
37435 @item maint check-psymtabs
37436 Check the consistency of currently expanded psymtabs versus symtabs.
37437 Use this to check, for example, whether a symbol is in one but not the other.
37439 @kindex maint check-symtabs
37440 @item maint check-symtabs
37441 Check the consistency of currently expanded symtabs.
37443 @kindex maint expand-symtabs
37444 @item maint expand-symtabs [@var{regexp}]
37445 Expand symbol tables.
37446 If @var{regexp} is specified, only expand symbol tables for file
37447 names matching @var{regexp}.
37449 @kindex maint cplus first_component
37450 @item maint cplus first_component @var{name}
37451 Print the first C@t{++} class/namespace component of @var{name}.
37453 @kindex maint cplus namespace
37454 @item maint cplus namespace
37455 Print the list of possible C@t{++} namespaces.
37457 @kindex maint demangle
37458 @item maint demangle @var{name}
37459 Demangle a C@t{++} or Objective-C mangled @var{name}.
37461 @kindex maint deprecate
37462 @kindex maint undeprecate
37463 @cindex deprecated commands
37464 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
37465 @itemx maint undeprecate @var{command}
37466 Deprecate or undeprecate the named @var{command}. Deprecated commands
37467 cause @value{GDBN} to issue a warning when you use them. The optional
37468 argument @var{replacement} says which newer command should be used in
37469 favor of the deprecated one; if it is given, @value{GDBN} will mention
37470 the replacement as part of the warning.
37472 @kindex maint dump-me
37473 @item maint dump-me
37474 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
37475 Cause a fatal signal in the debugger and force it to dump its core.
37476 This is supported only on systems which support aborting a program
37477 with the @code{SIGQUIT} signal.
37479 @kindex maint internal-error
37480 @kindex maint internal-warning
37481 @item maint internal-error @r{[}@var{message-text}@r{]}
37482 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
37483 Cause @value{GDBN} to call the internal function @code{internal_error}
37484 or @code{internal_warning} and hence behave as though an internal error
37485 or internal warning has been detected. In addition to reporting the
37486 internal problem, these functions give the user the opportunity to
37487 either quit @value{GDBN} or create a core file of the current
37488 @value{GDBN} session.
37490 These commands take an optional parameter @var{message-text} that is
37491 used as the text of the error or warning message.
37493 Here's an example of using @code{internal-error}:
37496 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
37497 @dots{}/maint.c:121: internal-error: testing, 1, 2
37498 A problem internal to GDB has been detected. Further
37499 debugging may prove unreliable.
37500 Quit this debugging session? (y or n) @kbd{n}
37501 Create a core file? (y or n) @kbd{n}
37505 @cindex @value{GDBN} internal error
37506 @cindex internal errors, control of @value{GDBN} behavior
37508 @kindex maint set internal-error
37509 @kindex maint show internal-error
37510 @kindex maint set internal-warning
37511 @kindex maint show internal-warning
37512 @item maint set internal-error @var{action} [ask|yes|no]
37513 @itemx maint show internal-error @var{action}
37514 @itemx maint set internal-warning @var{action} [ask|yes|no]
37515 @itemx maint show internal-warning @var{action}
37516 When @value{GDBN} reports an internal problem (error or warning) it
37517 gives the user the opportunity to both quit @value{GDBN} and create a
37518 core file of the current @value{GDBN} session. These commands let you
37519 override the default behaviour for each particular @var{action},
37520 described in the table below.
37524 You can specify that @value{GDBN} should always (yes) or never (no)
37525 quit. The default is to ask the user what to do.
37528 You can specify that @value{GDBN} should always (yes) or never (no)
37529 create a core file. The default is to ask the user what to do.
37532 @kindex maint packet
37533 @item maint packet @var{text}
37534 If @value{GDBN} is talking to an inferior via the serial protocol,
37535 then this command sends the string @var{text} to the inferior, and
37536 displays the response packet. @value{GDBN} supplies the initial
37537 @samp{$} character, the terminating @samp{#} character, and the
37540 @kindex maint print architecture
37541 @item maint print architecture @r{[}@var{file}@r{]}
37542 Print the entire architecture configuration. The optional argument
37543 @var{file} names the file where the output goes.
37545 @kindex maint print c-tdesc
37546 @item maint print c-tdesc
37547 Print the current target description (@pxref{Target Descriptions}) as
37548 a C source file. The created source file can be used in @value{GDBN}
37549 when an XML parser is not available to parse the description.
37551 @kindex maint print dummy-frames
37552 @item maint print dummy-frames
37553 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
37556 (@value{GDBP}) @kbd{b add}
37558 (@value{GDBP}) @kbd{print add(2,3)}
37559 Breakpoint 2, add (a=2, b=3) at @dots{}
37561 The program being debugged stopped while in a function called from GDB.
37563 (@value{GDBP}) @kbd{maint print dummy-frames}
37564 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
37565 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
37566 call_lo=0x01014000 call_hi=0x01014001
37570 Takes an optional file parameter.
37572 @kindex maint print registers
37573 @kindex maint print raw-registers
37574 @kindex maint print cooked-registers
37575 @kindex maint print register-groups
37576 @kindex maint print remote-registers
37577 @item maint print registers @r{[}@var{file}@r{]}
37578 @itemx maint print raw-registers @r{[}@var{file}@r{]}
37579 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
37580 @itemx maint print register-groups @r{[}@var{file}@r{]}
37581 @itemx maint print remote-registers @r{[}@var{file}@r{]}
37582 Print @value{GDBN}'s internal register data structures.
37584 The command @code{maint print raw-registers} includes the contents of
37585 the raw register cache; the command @code{maint print
37586 cooked-registers} includes the (cooked) value of all registers,
37587 including registers which aren't available on the target nor visible
37588 to user; the command @code{maint print register-groups} includes the
37589 groups that each register is a member of; and the command @code{maint
37590 print remote-registers} includes the remote target's register numbers
37591 and offsets in the `G' packets.
37593 These commands take an optional parameter, a file name to which to
37594 write the information.
37596 @kindex maint print reggroups
37597 @item maint print reggroups @r{[}@var{file}@r{]}
37598 Print @value{GDBN}'s internal register group data structures. The
37599 optional argument @var{file} tells to what file to write the
37602 The register groups info looks like this:
37605 (@value{GDBP}) @kbd{maint print reggroups}
37618 This command forces @value{GDBN} to flush its internal register cache.
37620 @kindex maint print objfiles
37621 @cindex info for known object files
37622 @item maint print objfiles @r{[}@var{regexp}@r{]}
37623 Print a dump of all known object files.
37624 If @var{regexp} is specified, only print object files whose names
37625 match @var{regexp}. For each object file, this command prints its name,
37626 address in memory, and all of its psymtabs and symtabs.
37628 @kindex maint print section-scripts
37629 @cindex info for known .debug_gdb_scripts-loaded scripts
37630 @item maint print section-scripts [@var{regexp}]
37631 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
37632 If @var{regexp} is specified, only print scripts loaded by object files
37633 matching @var{regexp}.
37634 For each script, this command prints its name as specified in the objfile,
37635 and the full path if known.
37636 @xref{dotdebug_gdb_scripts section}.
37638 @kindex maint print statistics
37639 @cindex bcache statistics
37640 @item maint print statistics
37641 This command prints, for each object file in the program, various data
37642 about that object file followed by the byte cache (@dfn{bcache})
37643 statistics for the object file. The objfile data includes the number
37644 of minimal, partial, full, and stabs symbols, the number of types
37645 defined by the objfile, the number of as yet unexpanded psym tables,
37646 the number of line tables and string tables, and the amount of memory
37647 used by the various tables. The bcache statistics include the counts,
37648 sizes, and counts of duplicates of all and unique objects, max,
37649 average, and median entry size, total memory used and its overhead and
37650 savings, and various measures of the hash table size and chain
37653 @kindex maint print target-stack
37654 @cindex target stack description
37655 @item maint print target-stack
37656 A @dfn{target} is an interface between the debugger and a particular
37657 kind of file or process. Targets can be stacked in @dfn{strata},
37658 so that more than one target can potentially respond to a request.
37659 In particular, memory accesses will walk down the stack of targets
37660 until they find a target that is interested in handling that particular
37663 This command prints a short description of each layer that was pushed on
37664 the @dfn{target stack}, starting from the top layer down to the bottom one.
37666 @kindex maint print type
37667 @cindex type chain of a data type
37668 @item maint print type @var{expr}
37669 Print the type chain for a type specified by @var{expr}. The argument
37670 can be either a type name or a symbol. If it is a symbol, the type of
37671 that symbol is described. The type chain produced by this command is
37672 a recursive definition of the data type as stored in @value{GDBN}'s
37673 data structures, including its flags and contained types.
37675 @kindex maint set dwarf2 always-disassemble
37676 @kindex maint show dwarf2 always-disassemble
37677 @item maint set dwarf2 always-disassemble
37678 @item maint show dwarf2 always-disassemble
37679 Control the behavior of @code{info address} when using DWARF debugging
37682 The default is @code{off}, which means that @value{GDBN} should try to
37683 describe a variable's location in an easily readable format. When
37684 @code{on}, @value{GDBN} will instead display the DWARF location
37685 expression in an assembly-like format. Note that some locations are
37686 too complex for @value{GDBN} to describe simply; in this case you will
37687 always see the disassembly form.
37689 Here is an example of the resulting disassembly:
37692 (gdb) info addr argc
37693 Symbol "argc" is a complex DWARF expression:
37697 For more information on these expressions, see
37698 @uref{http://www.dwarfstd.org/, the DWARF standard}.
37700 @kindex maint set dwarf2 max-cache-age
37701 @kindex maint show dwarf2 max-cache-age
37702 @item maint set dwarf2 max-cache-age
37703 @itemx maint show dwarf2 max-cache-age
37704 Control the DWARF 2 compilation unit cache.
37706 @cindex DWARF 2 compilation units cache
37707 In object files with inter-compilation-unit references, such as those
37708 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
37709 reader needs to frequently refer to previously read compilation units.
37710 This setting controls how long a compilation unit will remain in the
37711 cache if it is not referenced. A higher limit means that cached
37712 compilation units will be stored in memory longer, and more total
37713 memory will be used. Setting it to zero disables caching, which will
37714 slow down @value{GDBN} startup, but reduce memory consumption.
37716 @kindex maint set profile
37717 @kindex maint show profile
37718 @cindex profiling GDB
37719 @item maint set profile
37720 @itemx maint show profile
37721 Control profiling of @value{GDBN}.
37723 Profiling will be disabled until you use the @samp{maint set profile}
37724 command to enable it. When you enable profiling, the system will begin
37725 collecting timing and execution count data; when you disable profiling or
37726 exit @value{GDBN}, the results will be written to a log file. Remember that
37727 if you use profiling, @value{GDBN} will overwrite the profiling log file
37728 (often called @file{gmon.out}). If you have a record of important profiling
37729 data in a @file{gmon.out} file, be sure to move it to a safe location.
37731 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
37732 compiled with the @samp{-pg} compiler option.
37734 @kindex maint set show-debug-regs
37735 @kindex maint show show-debug-regs
37736 @cindex hardware debug registers
37737 @item maint set show-debug-regs
37738 @itemx maint show show-debug-regs
37739 Control whether to show variables that mirror the hardware debug
37740 registers. Use @code{on} to enable, @code{off} to disable. If
37741 enabled, the debug registers values are shown when @value{GDBN} inserts or
37742 removes a hardware breakpoint or watchpoint, and when the inferior
37743 triggers a hardware-assisted breakpoint or watchpoint.
37745 @kindex maint set show-all-tib
37746 @kindex maint show show-all-tib
37747 @item maint set show-all-tib
37748 @itemx maint show show-all-tib
37749 Control whether to show all non zero areas within a 1k block starting
37750 at thread local base, when using the @samp{info w32 thread-information-block}
37753 @kindex maint set per-command
37754 @kindex maint show per-command
37755 @item maint set per-command
37756 @itemx maint show per-command
37757 @cindex resources used by commands
37759 @value{GDBN} can display the resources used by each command.
37760 This is useful in debugging performance problems.
37763 @item maint set per-command space [on|off]
37764 @itemx maint show per-command space
37765 Enable or disable the printing of the memory used by GDB for each command.
37766 If enabled, @value{GDBN} will display how much memory each command
37767 took, following the command's own output.
37768 This can also be requested by invoking @value{GDBN} with the
37769 @option{--statistics} command-line switch (@pxref{Mode Options}).
37771 @item maint set per-command time [on|off]
37772 @itemx maint show per-command time
37773 Enable or disable the printing of the execution time of @value{GDBN}
37775 If enabled, @value{GDBN} will display how much time it
37776 took to execute each command, following the command's own output.
37777 Both CPU time and wallclock time are printed.
37778 Printing both is useful when trying to determine whether the cost is
37779 CPU or, e.g., disk/network latency.
37780 Note that the CPU time printed is for @value{GDBN} only, it does not include
37781 the execution time of the inferior because there's no mechanism currently
37782 to compute how much time was spent by @value{GDBN} and how much time was
37783 spent by the program been debugged.
37784 This can also be requested by invoking @value{GDBN} with the
37785 @option{--statistics} command-line switch (@pxref{Mode Options}).
37787 @item maint set per-command symtab [on|off]
37788 @itemx maint show per-command symtab
37789 Enable or disable the printing of basic symbol table statistics
37791 If enabled, @value{GDBN} will display the following information:
37795 number of symbol tables
37797 number of primary symbol tables
37799 number of blocks in the blockvector
37803 @kindex maint space
37804 @cindex memory used by commands
37805 @item maint space @var{value}
37806 An alias for @code{maint set per-command space}.
37807 A non-zero value enables it, zero disables it.
37810 @cindex time of command execution
37811 @item maint time @var{value}
37812 An alias for @code{maint set per-command time}.
37813 A non-zero value enables it, zero disables it.
37815 @kindex maint translate-address
37816 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
37817 Find the symbol stored at the location specified by the address
37818 @var{addr} and an optional section name @var{section}. If found,
37819 @value{GDBN} prints the name of the closest symbol and an offset from
37820 the symbol's location to the specified address. This is similar to
37821 the @code{info address} command (@pxref{Symbols}), except that this
37822 command also allows to find symbols in other sections.
37824 If section was not specified, the section in which the symbol was found
37825 is also printed. For dynamically linked executables, the name of
37826 executable or shared library containing the symbol is printed as well.
37830 The following command is useful for non-interactive invocations of
37831 @value{GDBN}, such as in the test suite.
37834 @item set watchdog @var{nsec}
37835 @kindex set watchdog
37836 @cindex watchdog timer
37837 @cindex timeout for commands
37838 Set the maximum number of seconds @value{GDBN} will wait for the
37839 target operation to finish. If this time expires, @value{GDBN}
37840 reports and error and the command is aborted.
37842 @item show watchdog
37843 Show the current setting of the target wait timeout.
37846 @node Remote Protocol
37847 @appendix @value{GDBN} Remote Serial Protocol
37852 * Stop Reply Packets::
37853 * General Query Packets::
37854 * Architecture-Specific Protocol Details::
37855 * Tracepoint Packets::
37856 * Host I/O Packets::
37858 * Notification Packets::
37859 * Remote Non-Stop::
37860 * Packet Acknowledgment::
37862 * File-I/O Remote Protocol Extension::
37863 * Library List Format::
37864 * Library List Format for SVR4 Targets::
37865 * Memory Map Format::
37866 * Thread List Format::
37867 * Traceframe Info Format::
37868 * Branch Trace Format::
37874 There may be occasions when you need to know something about the
37875 protocol---for example, if there is only one serial port to your target
37876 machine, you might want your program to do something special if it
37877 recognizes a packet meant for @value{GDBN}.
37879 In the examples below, @samp{->} and @samp{<-} are used to indicate
37880 transmitted and received data, respectively.
37882 @cindex protocol, @value{GDBN} remote serial
37883 @cindex serial protocol, @value{GDBN} remote
37884 @cindex remote serial protocol
37885 All @value{GDBN} commands and responses (other than acknowledgments
37886 and notifications, see @ref{Notification Packets}) are sent as a
37887 @var{packet}. A @var{packet} is introduced with the character
37888 @samp{$}, the actual @var{packet-data}, and the terminating character
37889 @samp{#} followed by a two-digit @var{checksum}:
37892 @code{$}@var{packet-data}@code{#}@var{checksum}
37896 @cindex checksum, for @value{GDBN} remote
37898 The two-digit @var{checksum} is computed as the modulo 256 sum of all
37899 characters between the leading @samp{$} and the trailing @samp{#} (an
37900 eight bit unsigned checksum).
37902 Implementors should note that prior to @value{GDBN} 5.0 the protocol
37903 specification also included an optional two-digit @var{sequence-id}:
37906 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
37909 @cindex sequence-id, for @value{GDBN} remote
37911 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
37912 has never output @var{sequence-id}s. Stubs that handle packets added
37913 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
37915 When either the host or the target machine receives a packet, the first
37916 response expected is an acknowledgment: either @samp{+} (to indicate
37917 the package was received correctly) or @samp{-} (to request
37921 -> @code{$}@var{packet-data}@code{#}@var{checksum}
37926 The @samp{+}/@samp{-} acknowledgments can be disabled
37927 once a connection is established.
37928 @xref{Packet Acknowledgment}, for details.
37930 The host (@value{GDBN}) sends @var{command}s, and the target (the
37931 debugging stub incorporated in your program) sends a @var{response}. In
37932 the case of step and continue @var{command}s, the response is only sent
37933 when the operation has completed, and the target has again stopped all
37934 threads in all attached processes. This is the default all-stop mode
37935 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
37936 execution mode; see @ref{Remote Non-Stop}, for details.
37938 @var{packet-data} consists of a sequence of characters with the
37939 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
37942 @cindex remote protocol, field separator
37943 Fields within the packet should be separated using @samp{,} @samp{;} or
37944 @samp{:}. Except where otherwise noted all numbers are represented in
37945 @sc{hex} with leading zeros suppressed.
37947 Implementors should note that prior to @value{GDBN} 5.0, the character
37948 @samp{:} could not appear as the third character in a packet (as it
37949 would potentially conflict with the @var{sequence-id}).
37951 @cindex remote protocol, binary data
37952 @anchor{Binary Data}
37953 Binary data in most packets is encoded either as two hexadecimal
37954 digits per byte of binary data. This allowed the traditional remote
37955 protocol to work over connections which were only seven-bit clean.
37956 Some packets designed more recently assume an eight-bit clean
37957 connection, and use a more efficient encoding to send and receive
37960 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
37961 as an escape character. Any escaped byte is transmitted as the escape
37962 character followed by the original character XORed with @code{0x20}.
37963 For example, the byte @code{0x7d} would be transmitted as the two
37964 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
37965 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
37966 @samp{@}}) must always be escaped. Responses sent by the stub
37967 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
37968 is not interpreted as the start of a run-length encoded sequence
37971 Response @var{data} can be run-length encoded to save space.
37972 Run-length encoding replaces runs of identical characters with one
37973 instance of the repeated character, followed by a @samp{*} and a
37974 repeat count. The repeat count is itself sent encoded, to avoid
37975 binary characters in @var{data}: a value of @var{n} is sent as
37976 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
37977 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
37978 code 32) for a repeat count of 3. (This is because run-length
37979 encoding starts to win for counts 3 or more.) Thus, for example,
37980 @samp{0* } is a run-length encoding of ``0000'': the space character
37981 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
37984 The printable characters @samp{#} and @samp{$} or with a numeric value
37985 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
37986 seven repeats (@samp{$}) can be expanded using a repeat count of only
37987 five (@samp{"}). For example, @samp{00000000} can be encoded as
37990 The error response returned for some packets includes a two character
37991 error number. That number is not well defined.
37993 @cindex empty response, for unsupported packets
37994 For any @var{command} not supported by the stub, an empty response
37995 (@samp{$#00}) should be returned. That way it is possible to extend the
37996 protocol. A newer @value{GDBN} can tell if a packet is supported based
37999 At a minimum, a stub is required to support the @samp{g} and @samp{G}
38000 commands for register access, and the @samp{m} and @samp{M} commands
38001 for memory access. Stubs that only control single-threaded targets
38002 can implement run control with the @samp{c} (continue), and @samp{s}
38003 (step) commands. Stubs that support multi-threading targets should
38004 support the @samp{vCont} command. All other commands are optional.
38009 The following table provides a complete list of all currently defined
38010 @var{command}s and their corresponding response @var{data}.
38011 @xref{File-I/O Remote Protocol Extension}, for details about the File
38012 I/O extension of the remote protocol.
38014 Each packet's description has a template showing the packet's overall
38015 syntax, followed by an explanation of the packet's meaning. We
38016 include spaces in some of the templates for clarity; these are not
38017 part of the packet's syntax. No @value{GDBN} packet uses spaces to
38018 separate its components. For example, a template like @samp{foo
38019 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
38020 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
38021 @var{baz}. @value{GDBN} does not transmit a space character between the
38022 @samp{foo} and the @var{bar}, or between the @var{bar} and the
38025 @cindex @var{thread-id}, in remote protocol
38026 @anchor{thread-id syntax}
38027 Several packets and replies include a @var{thread-id} field to identify
38028 a thread. Normally these are positive numbers with a target-specific
38029 interpretation, formatted as big-endian hex strings. A @var{thread-id}
38030 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
38033 In addition, the remote protocol supports a multiprocess feature in
38034 which the @var{thread-id} syntax is extended to optionally include both
38035 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
38036 The @var{pid} (process) and @var{tid} (thread) components each have the
38037 format described above: a positive number with target-specific
38038 interpretation formatted as a big-endian hex string, literal @samp{-1}
38039 to indicate all processes or threads (respectively), or @samp{0} to
38040 indicate an arbitrary process or thread. Specifying just a process, as
38041 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
38042 error to specify all processes but a specific thread, such as
38043 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
38044 for those packets and replies explicitly documented to include a process
38045 ID, rather than a @var{thread-id}.
38047 The multiprocess @var{thread-id} syntax extensions are only used if both
38048 @value{GDBN} and the stub report support for the @samp{multiprocess}
38049 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
38052 Note that all packet forms beginning with an upper- or lower-case
38053 letter, other than those described here, are reserved for future use.
38055 Here are the packet descriptions.
38060 @cindex @samp{!} packet
38061 @anchor{extended mode}
38062 Enable extended mode. In extended mode, the remote server is made
38063 persistent. The @samp{R} packet is used to restart the program being
38069 The remote target both supports and has enabled extended mode.
38073 @cindex @samp{?} packet
38074 Indicate the reason the target halted. The reply is the same as for
38075 step and continue. This packet has a special interpretation when the
38076 target is in non-stop mode; see @ref{Remote Non-Stop}.
38079 @xref{Stop Reply Packets}, for the reply specifications.
38081 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
38082 @cindex @samp{A} packet
38083 Initialized @code{argv[]} array passed into program. @var{arglen}
38084 specifies the number of bytes in the hex encoded byte stream
38085 @var{arg}. See @code{gdbserver} for more details.
38090 The arguments were set.
38096 @cindex @samp{b} packet
38097 (Don't use this packet; its behavior is not well-defined.)
38098 Change the serial line speed to @var{baud}.
38100 JTC: @emph{When does the transport layer state change? When it's
38101 received, or after the ACK is transmitted. In either case, there are
38102 problems if the command or the acknowledgment packet is dropped.}
38104 Stan: @emph{If people really wanted to add something like this, and get
38105 it working for the first time, they ought to modify ser-unix.c to send
38106 some kind of out-of-band message to a specially-setup stub and have the
38107 switch happen "in between" packets, so that from remote protocol's point
38108 of view, nothing actually happened.}
38110 @item B @var{addr},@var{mode}
38111 @cindex @samp{B} packet
38112 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
38113 breakpoint at @var{addr}.
38115 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
38116 (@pxref{insert breakpoint or watchpoint packet}).
38118 @cindex @samp{bc} packet
38121 Backward continue. Execute the target system in reverse. No parameter.
38122 @xref{Reverse Execution}, for more information.
38125 @xref{Stop Reply Packets}, for the reply specifications.
38127 @cindex @samp{bs} packet
38130 Backward single step. Execute one instruction in reverse. No parameter.
38131 @xref{Reverse Execution}, for more information.
38134 @xref{Stop Reply Packets}, for the reply specifications.
38136 @item c @r{[}@var{addr}@r{]}
38137 @cindex @samp{c} packet
38138 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
38139 resume at current address.
38141 This packet is deprecated for multi-threading support. @xref{vCont
38145 @xref{Stop Reply Packets}, for the reply specifications.
38147 @item C @var{sig}@r{[};@var{addr}@r{]}
38148 @cindex @samp{C} packet
38149 Continue with signal @var{sig} (hex signal number). If
38150 @samp{;@var{addr}} is omitted, resume at same address.
38152 This packet is deprecated for multi-threading support. @xref{vCont
38156 @xref{Stop Reply Packets}, for the reply specifications.
38159 @cindex @samp{d} packet
38162 Don't use this packet; instead, define a general set packet
38163 (@pxref{General Query Packets}).
38167 @cindex @samp{D} packet
38168 The first form of the packet is used to detach @value{GDBN} from the
38169 remote system. It is sent to the remote target
38170 before @value{GDBN} disconnects via the @code{detach} command.
38172 The second form, including a process ID, is used when multiprocess
38173 protocol extensions are enabled (@pxref{multiprocess extensions}), to
38174 detach only a specific process. The @var{pid} is specified as a
38175 big-endian hex string.
38185 @item F @var{RC},@var{EE},@var{CF};@var{XX}
38186 @cindex @samp{F} packet
38187 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
38188 This is part of the File-I/O protocol extension. @xref{File-I/O
38189 Remote Protocol Extension}, for the specification.
38192 @anchor{read registers packet}
38193 @cindex @samp{g} packet
38194 Read general registers.
38198 @item @var{XX@dots{}}
38199 Each byte of register data is described by two hex digits. The bytes
38200 with the register are transmitted in target byte order. The size of
38201 each register and their position within the @samp{g} packet are
38202 determined by the @value{GDBN} internal gdbarch functions
38203 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
38204 specification of several standard @samp{g} packets is specified below.
38206 When reading registers from a trace frame (@pxref{Analyze Collected
38207 Data,,Using the Collected Data}), the stub may also return a string of
38208 literal @samp{x}'s in place of the register data digits, to indicate
38209 that the corresponding register has not been collected, thus its value
38210 is unavailable. For example, for an architecture with 4 registers of
38211 4 bytes each, the following reply indicates to @value{GDBN} that
38212 registers 0 and 2 have not been collected, while registers 1 and 3
38213 have been collected, and both have zero value:
38217 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
38224 @item G @var{XX@dots{}}
38225 @cindex @samp{G} packet
38226 Write general registers. @xref{read registers packet}, for a
38227 description of the @var{XX@dots{}} data.
38237 @item H @var{op} @var{thread-id}
38238 @cindex @samp{H} packet
38239 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
38240 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
38241 it should be @samp{c} for step and continue operations (note that this
38242 is deprecated, supporting the @samp{vCont} command is a better
38243 option), @samp{g} for other operations. The thread designator
38244 @var{thread-id} has the format and interpretation described in
38245 @ref{thread-id syntax}.
38256 @c 'H': How restrictive (or permissive) is the thread model. If a
38257 @c thread is selected and stopped, are other threads allowed
38258 @c to continue to execute? As I mentioned above, I think the
38259 @c semantics of each command when a thread is selected must be
38260 @c described. For example:
38262 @c 'g': If the stub supports threads and a specific thread is
38263 @c selected, returns the register block from that thread;
38264 @c otherwise returns current registers.
38266 @c 'G' If the stub supports threads and a specific thread is
38267 @c selected, sets the registers of the register block of
38268 @c that thread; otherwise sets current registers.
38270 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
38271 @anchor{cycle step packet}
38272 @cindex @samp{i} packet
38273 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
38274 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
38275 step starting at that address.
38278 @cindex @samp{I} packet
38279 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
38283 @cindex @samp{k} packet
38286 FIXME: @emph{There is no description of how to operate when a specific
38287 thread context has been selected (i.e.@: does 'k' kill only that
38290 @item m @var{addr},@var{length}
38291 @cindex @samp{m} packet
38292 Read @var{length} bytes of memory starting at address @var{addr}.
38293 Note that @var{addr} may not be aligned to any particular boundary.
38295 The stub need not use any particular size or alignment when gathering
38296 data from memory for the response; even if @var{addr} is word-aligned
38297 and @var{length} is a multiple of the word size, the stub is free to
38298 use byte accesses, or not. For this reason, this packet may not be
38299 suitable for accessing memory-mapped I/O devices.
38300 @cindex alignment of remote memory accesses
38301 @cindex size of remote memory accesses
38302 @cindex memory, alignment and size of remote accesses
38306 @item @var{XX@dots{}}
38307 Memory contents; each byte is transmitted as a two-digit hexadecimal
38308 number. The reply may contain fewer bytes than requested if the
38309 server was able to read only part of the region of memory.
38314 @item M @var{addr},@var{length}:@var{XX@dots{}}
38315 @cindex @samp{M} packet
38316 Write @var{length} bytes of memory starting at address @var{addr}.
38317 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
38318 hexadecimal number.
38325 for an error (this includes the case where only part of the data was
38330 @cindex @samp{p} packet
38331 Read the value of register @var{n}; @var{n} is in hex.
38332 @xref{read registers packet}, for a description of how the returned
38333 register value is encoded.
38337 @item @var{XX@dots{}}
38338 the register's value
38342 Indicating an unrecognized @var{query}.
38345 @item P @var{n@dots{}}=@var{r@dots{}}
38346 @anchor{write register packet}
38347 @cindex @samp{P} packet
38348 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
38349 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
38350 digits for each byte in the register (target byte order).
38360 @item q @var{name} @var{params}@dots{}
38361 @itemx Q @var{name} @var{params}@dots{}
38362 @cindex @samp{q} packet
38363 @cindex @samp{Q} packet
38364 General query (@samp{q}) and set (@samp{Q}). These packets are
38365 described fully in @ref{General Query Packets}.
38368 @cindex @samp{r} packet
38369 Reset the entire system.
38371 Don't use this packet; use the @samp{R} packet instead.
38374 @cindex @samp{R} packet
38375 Restart the program being debugged. @var{XX}, while needed, is ignored.
38376 This packet is only available in extended mode (@pxref{extended mode}).
38378 The @samp{R} packet has no reply.
38380 @item s @r{[}@var{addr}@r{]}
38381 @cindex @samp{s} packet
38382 Single step. @var{addr} is the address at which to resume. If
38383 @var{addr} is omitted, resume at same address.
38385 This packet is deprecated for multi-threading support. @xref{vCont
38389 @xref{Stop Reply Packets}, for the reply specifications.
38391 @item S @var{sig}@r{[};@var{addr}@r{]}
38392 @anchor{step with signal packet}
38393 @cindex @samp{S} packet
38394 Step with signal. This is analogous to the @samp{C} packet, but
38395 requests a single-step, rather than a normal resumption of execution.
38397 This packet is deprecated for multi-threading support. @xref{vCont
38401 @xref{Stop Reply Packets}, for the reply specifications.
38403 @item t @var{addr}:@var{PP},@var{MM}
38404 @cindex @samp{t} packet
38405 Search backwards starting at address @var{addr} for a match with pattern
38406 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
38407 @var{addr} must be at least 3 digits.
38409 @item T @var{thread-id}
38410 @cindex @samp{T} packet
38411 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
38416 thread is still alive
38422 Packets starting with @samp{v} are identified by a multi-letter name,
38423 up to the first @samp{;} or @samp{?} (or the end of the packet).
38425 @item vAttach;@var{pid}
38426 @cindex @samp{vAttach} packet
38427 Attach to a new process with the specified process ID @var{pid}.
38428 The process ID is a
38429 hexadecimal integer identifying the process. In all-stop mode, all
38430 threads in the attached process are stopped; in non-stop mode, it may be
38431 attached without being stopped if that is supported by the target.
38433 @c In non-stop mode, on a successful vAttach, the stub should set the
38434 @c current thread to a thread of the newly-attached process. After
38435 @c attaching, GDB queries for the attached process's thread ID with qC.
38436 @c Also note that, from a user perspective, whether or not the
38437 @c target is stopped on attach in non-stop mode depends on whether you
38438 @c use the foreground or background version of the attach command, not
38439 @c on what vAttach does; GDB does the right thing with respect to either
38440 @c stopping or restarting threads.
38442 This packet is only available in extended mode (@pxref{extended mode}).
38448 @item @r{Any stop packet}
38449 for success in all-stop mode (@pxref{Stop Reply Packets})
38451 for success in non-stop mode (@pxref{Remote Non-Stop})
38454 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
38455 @cindex @samp{vCont} packet
38456 @anchor{vCont packet}
38457 Resume the inferior, specifying different actions for each thread.
38458 If an action is specified with no @var{thread-id}, then it is applied to any
38459 threads that don't have a specific action specified; if no default action is
38460 specified then other threads should remain stopped in all-stop mode and
38461 in their current state in non-stop mode.
38462 Specifying multiple
38463 default actions is an error; specifying no actions is also an error.
38464 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
38466 Currently supported actions are:
38472 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
38476 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
38479 @item r @var{start},@var{end}
38480 Step once, and then keep stepping as long as the thread stops at
38481 addresses between @var{start} (inclusive) and @var{end} (exclusive).
38482 The remote stub reports a stop reply when either the thread goes out
38483 of the range or is stopped due to an unrelated reason, such as hitting
38484 a breakpoint. @xref{range stepping}.
38486 If the range is empty (@var{start} == @var{end}), then the action
38487 becomes equivalent to the @samp{s} action. In other words,
38488 single-step once, and report the stop (even if the stepped instruction
38489 jumps to @var{start}).
38491 (A stop reply may be sent at any point even if the PC is still within
38492 the stepping range; for example, it is valid to implement this packet
38493 in a degenerate way as a single instruction step operation.)
38497 The optional argument @var{addr} normally associated with the
38498 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
38499 not supported in @samp{vCont}.
38501 The @samp{t} action is only relevant in non-stop mode
38502 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
38503 A stop reply should be generated for any affected thread not already stopped.
38504 When a thread is stopped by means of a @samp{t} action,
38505 the corresponding stop reply should indicate that the thread has stopped with
38506 signal @samp{0}, regardless of whether the target uses some other signal
38507 as an implementation detail.
38509 The stub must support @samp{vCont} if it reports support for
38510 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
38511 this case @samp{vCont} actions can be specified to apply to all threads
38512 in a process by using the @samp{p@var{pid}.-1} form of the
38516 @xref{Stop Reply Packets}, for the reply specifications.
38519 @cindex @samp{vCont?} packet
38520 Request a list of actions supported by the @samp{vCont} packet.
38524 @item vCont@r{[};@var{action}@dots{}@r{]}
38525 The @samp{vCont} packet is supported. Each @var{action} is a supported
38526 command in the @samp{vCont} packet.
38528 The @samp{vCont} packet is not supported.
38531 @item vFile:@var{operation}:@var{parameter}@dots{}
38532 @cindex @samp{vFile} packet
38533 Perform a file operation on the target system. For details,
38534 see @ref{Host I/O Packets}.
38536 @item vFlashErase:@var{addr},@var{length}
38537 @cindex @samp{vFlashErase} packet
38538 Direct the stub to erase @var{length} bytes of flash starting at
38539 @var{addr}. The region may enclose any number of flash blocks, but
38540 its start and end must fall on block boundaries, as indicated by the
38541 flash block size appearing in the memory map (@pxref{Memory Map
38542 Format}). @value{GDBN} groups flash memory programming operations
38543 together, and sends a @samp{vFlashDone} request after each group; the
38544 stub is allowed to delay erase operation until the @samp{vFlashDone}
38545 packet is received.
38555 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
38556 @cindex @samp{vFlashWrite} packet
38557 Direct the stub to write data to flash address @var{addr}. The data
38558 is passed in binary form using the same encoding as for the @samp{X}
38559 packet (@pxref{Binary Data}). The memory ranges specified by
38560 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
38561 not overlap, and must appear in order of increasing addresses
38562 (although @samp{vFlashErase} packets for higher addresses may already
38563 have been received; the ordering is guaranteed only between
38564 @samp{vFlashWrite} packets). If a packet writes to an address that was
38565 neither erased by a preceding @samp{vFlashErase} packet nor by some other
38566 target-specific method, the results are unpredictable.
38574 for vFlashWrite addressing non-flash memory
38580 @cindex @samp{vFlashDone} packet
38581 Indicate to the stub that flash programming operation is finished.
38582 The stub is permitted to delay or batch the effects of a group of
38583 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
38584 @samp{vFlashDone} packet is received. The contents of the affected
38585 regions of flash memory are unpredictable until the @samp{vFlashDone}
38586 request is completed.
38588 @item vKill;@var{pid}
38589 @cindex @samp{vKill} packet
38590 Kill the process with the specified process ID. @var{pid} is a
38591 hexadecimal integer identifying the process. This packet is used in
38592 preference to @samp{k} when multiprocess protocol extensions are
38593 supported; see @ref{multiprocess extensions}.
38603 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
38604 @cindex @samp{vRun} packet
38605 Run the program @var{filename}, passing it each @var{argument} on its
38606 command line. The file and arguments are hex-encoded strings. If
38607 @var{filename} is an empty string, the stub may use a default program
38608 (e.g.@: the last program run). The program is created in the stopped
38611 @c FIXME: What about non-stop mode?
38613 This packet is only available in extended mode (@pxref{extended mode}).
38619 @item @r{Any stop packet}
38620 for success (@pxref{Stop Reply Packets})
38624 @cindex @samp{vStopped} packet
38625 @xref{Notification Packets}.
38627 @item X @var{addr},@var{length}:@var{XX@dots{}}
38629 @cindex @samp{X} packet
38630 Write data to memory, where the data is transmitted in binary.
38631 @var{addr} is address, @var{length} is number of bytes,
38632 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
38642 @item z @var{type},@var{addr},@var{kind}
38643 @itemx Z @var{type},@var{addr},@var{kind}
38644 @anchor{insert breakpoint or watchpoint packet}
38645 @cindex @samp{z} packet
38646 @cindex @samp{Z} packets
38647 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
38648 watchpoint starting at address @var{address} of kind @var{kind}.
38650 Each breakpoint and watchpoint packet @var{type} is documented
38653 @emph{Implementation notes: A remote target shall return an empty string
38654 for an unrecognized breakpoint or watchpoint packet @var{type}. A
38655 remote target shall support either both or neither of a given
38656 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
38657 avoid potential problems with duplicate packets, the operations should
38658 be implemented in an idempotent way.}
38660 @item z0,@var{addr},@var{kind}
38661 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
38662 @cindex @samp{z0} packet
38663 @cindex @samp{Z0} packet
38664 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
38665 @var{addr} of type @var{kind}.
38667 A memory breakpoint is implemented by replacing the instruction at
38668 @var{addr} with a software breakpoint or trap instruction. The
38669 @var{kind} is target-specific and typically indicates the size of
38670 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
38671 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
38672 architectures have additional meanings for @var{kind};
38673 @var{cond_list} is an optional list of conditional expressions in bytecode
38674 form that should be evaluated on the target's side. These are the
38675 conditions that should be taken into consideration when deciding if
38676 the breakpoint trigger should be reported back to @var{GDBN}.
38678 The @var{cond_list} parameter is comprised of a series of expressions,
38679 concatenated without separators. Each expression has the following form:
38683 @item X @var{len},@var{expr}
38684 @var{len} is the length of the bytecode expression and @var{expr} is the
38685 actual conditional expression in bytecode form.
38689 The optional @var{cmd_list} parameter introduces commands that may be
38690 run on the target, rather than being reported back to @value{GDBN}.
38691 The parameter starts with a numeric flag @var{persist}; if the flag is
38692 nonzero, then the breakpoint may remain active and the commands
38693 continue to be run even when @value{GDBN} disconnects from the target.
38694 Following this flag is a series of expressions concatenated with no
38695 separators. Each expression has the following form:
38699 @item X @var{len},@var{expr}
38700 @var{len} is the length of the bytecode expression and @var{expr} is the
38701 actual conditional expression in bytecode form.
38705 see @ref{Architecture-Specific Protocol Details}.
38707 @emph{Implementation note: It is possible for a target to copy or move
38708 code that contains memory breakpoints (e.g., when implementing
38709 overlays). The behavior of this packet, in the presence of such a
38710 target, is not defined.}
38722 @item z1,@var{addr},@var{kind}
38723 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
38724 @cindex @samp{z1} packet
38725 @cindex @samp{Z1} packet
38726 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
38727 address @var{addr}.
38729 A hardware breakpoint is implemented using a mechanism that is not
38730 dependant on being able to modify the target's memory. @var{kind}
38731 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
38733 @emph{Implementation note: A hardware breakpoint is not affected by code
38746 @item z2,@var{addr},@var{kind}
38747 @itemx Z2,@var{addr},@var{kind}
38748 @cindex @samp{z2} packet
38749 @cindex @samp{Z2} packet
38750 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
38751 @var{kind} is interpreted as the number of bytes to watch.
38763 @item z3,@var{addr},@var{kind}
38764 @itemx Z3,@var{addr},@var{kind}
38765 @cindex @samp{z3} packet
38766 @cindex @samp{Z3} packet
38767 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
38768 @var{kind} is interpreted as the number of bytes to watch.
38780 @item z4,@var{addr},@var{kind}
38781 @itemx Z4,@var{addr},@var{kind}
38782 @cindex @samp{z4} packet
38783 @cindex @samp{Z4} packet
38784 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
38785 @var{kind} is interpreted as the number of bytes to watch.
38799 @node Stop Reply Packets
38800 @section Stop Reply Packets
38801 @cindex stop reply packets
38803 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
38804 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
38805 receive any of the below as a reply. Except for @samp{?}
38806 and @samp{vStopped}, that reply is only returned
38807 when the target halts. In the below the exact meaning of @dfn{signal
38808 number} is defined by the header @file{include/gdb/signals.h} in the
38809 @value{GDBN} source code.
38811 As in the description of request packets, we include spaces in the
38812 reply templates for clarity; these are not part of the reply packet's
38813 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
38819 The program received signal number @var{AA} (a two-digit hexadecimal
38820 number). This is equivalent to a @samp{T} response with no
38821 @var{n}:@var{r} pairs.
38823 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
38824 @cindex @samp{T} packet reply
38825 The program received signal number @var{AA} (a two-digit hexadecimal
38826 number). This is equivalent to an @samp{S} response, except that the
38827 @samp{@var{n}:@var{r}} pairs can carry values of important registers
38828 and other information directly in the stop reply packet, reducing
38829 round-trip latency. Single-step and breakpoint traps are reported
38830 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
38834 If @var{n} is a hexadecimal number, it is a register number, and the
38835 corresponding @var{r} gives that register's value. @var{r} is a
38836 series of bytes in target byte order, with each byte given by a
38837 two-digit hex number.
38840 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
38841 the stopped thread, as specified in @ref{thread-id syntax}.
38844 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
38845 the core on which the stop event was detected.
38848 If @var{n} is a recognized @dfn{stop reason}, it describes a more
38849 specific event that stopped the target. The currently defined stop
38850 reasons are listed below. @var{aa} should be @samp{05}, the trap
38851 signal. At most one stop reason should be present.
38854 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
38855 and go on to the next; this allows us to extend the protocol in the
38859 The currently defined stop reasons are:
38865 The packet indicates a watchpoint hit, and @var{r} is the data address, in
38868 @cindex shared library events, remote reply
38870 The packet indicates that the loaded libraries have changed.
38871 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
38872 list of loaded libraries. @var{r} is ignored.
38874 @cindex replay log events, remote reply
38876 The packet indicates that the target cannot continue replaying
38877 logged execution events, because it has reached the end (or the
38878 beginning when executing backward) of the log. The value of @var{r}
38879 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
38880 for more information.
38884 @itemx W @var{AA} ; process:@var{pid}
38885 The process exited, and @var{AA} is the exit status. This is only
38886 applicable to certain targets.
38888 The second form of the response, including the process ID of the exited
38889 process, can be used only when @value{GDBN} has reported support for
38890 multiprocess protocol extensions; see @ref{multiprocess extensions}.
38891 The @var{pid} is formatted as a big-endian hex string.
38894 @itemx X @var{AA} ; process:@var{pid}
38895 The process terminated with signal @var{AA}.
38897 The second form of the response, including the process ID of the
38898 terminated process, can be used only when @value{GDBN} has reported
38899 support for multiprocess protocol extensions; see @ref{multiprocess
38900 extensions}. The @var{pid} is formatted as a big-endian hex string.
38902 @item O @var{XX}@dots{}
38903 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
38904 written as the program's console output. This can happen at any time
38905 while the program is running and the debugger should continue to wait
38906 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
38908 @item F @var{call-id},@var{parameter}@dots{}
38909 @var{call-id} is the identifier which says which host system call should
38910 be called. This is just the name of the function. Translation into the
38911 correct system call is only applicable as it's defined in @value{GDBN}.
38912 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
38915 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
38916 this very system call.
38918 The target replies with this packet when it expects @value{GDBN} to
38919 call a host system call on behalf of the target. @value{GDBN} replies
38920 with an appropriate @samp{F} packet and keeps up waiting for the next
38921 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
38922 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
38923 Protocol Extension}, for more details.
38927 @node General Query Packets
38928 @section General Query Packets
38929 @cindex remote query requests
38931 Packets starting with @samp{q} are @dfn{general query packets};
38932 packets starting with @samp{Q} are @dfn{general set packets}. General
38933 query and set packets are a semi-unified form for retrieving and
38934 sending information to and from the stub.
38936 The initial letter of a query or set packet is followed by a name
38937 indicating what sort of thing the packet applies to. For example,
38938 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
38939 definitions with the stub. These packet names follow some
38944 The name must not contain commas, colons or semicolons.
38946 Most @value{GDBN} query and set packets have a leading upper case
38949 The names of custom vendor packets should use a company prefix, in
38950 lower case, followed by a period. For example, packets designed at
38951 the Acme Corporation might begin with @samp{qacme.foo} (for querying
38952 foos) or @samp{Qacme.bar} (for setting bars).
38955 The name of a query or set packet should be separated from any
38956 parameters by a @samp{:}; the parameters themselves should be
38957 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
38958 full packet name, and check for a separator or the end of the packet,
38959 in case two packet names share a common prefix. New packets should not begin
38960 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
38961 packets predate these conventions, and have arguments without any terminator
38962 for the packet name; we suspect they are in widespread use in places that
38963 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
38964 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
38967 Like the descriptions of the other packets, each description here
38968 has a template showing the packet's overall syntax, followed by an
38969 explanation of the packet's meaning. We include spaces in some of the
38970 templates for clarity; these are not part of the packet's syntax. No
38971 @value{GDBN} packet uses spaces to separate its components.
38973 Here are the currently defined query and set packets:
38979 Turn on or off the agent as a helper to perform some debugging operations
38980 delegated from @value{GDBN} (@pxref{Control Agent}).
38982 @item QAllow:@var{op}:@var{val}@dots{}
38983 @cindex @samp{QAllow} packet
38984 Specify which operations @value{GDBN} expects to request of the
38985 target, as a semicolon-separated list of operation name and value
38986 pairs. Possible values for @var{op} include @samp{WriteReg},
38987 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
38988 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
38989 indicating that @value{GDBN} will not request the operation, or 1,
38990 indicating that it may. (The target can then use this to set up its
38991 own internals optimally, for instance if the debugger never expects to
38992 insert breakpoints, it may not need to install its own trap handler.)
38995 @cindex current thread, remote request
38996 @cindex @samp{qC} packet
38997 Return the current thread ID.
39001 @item QC @var{thread-id}
39002 Where @var{thread-id} is a thread ID as documented in
39003 @ref{thread-id syntax}.
39004 @item @r{(anything else)}
39005 Any other reply implies the old thread ID.
39008 @item qCRC:@var{addr},@var{length}
39009 @cindex CRC of memory block, remote request
39010 @cindex @samp{qCRC} packet
39011 Compute the CRC checksum of a block of memory using CRC-32 defined in
39012 IEEE 802.3. The CRC is computed byte at a time, taking the most
39013 significant bit of each byte first. The initial pattern code
39014 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
39016 @emph{Note:} This is the same CRC used in validating separate debug
39017 files (@pxref{Separate Debug Files, , Debugging Information in Separate
39018 Files}). However the algorithm is slightly different. When validating
39019 separate debug files, the CRC is computed taking the @emph{least}
39020 significant bit of each byte first, and the final result is inverted to
39021 detect trailing zeros.
39026 An error (such as memory fault)
39027 @item C @var{crc32}
39028 The specified memory region's checksum is @var{crc32}.
39031 @item QDisableRandomization:@var{value}
39032 @cindex disable address space randomization, remote request
39033 @cindex @samp{QDisableRandomization} packet
39034 Some target operating systems will randomize the virtual address space
39035 of the inferior process as a security feature, but provide a feature
39036 to disable such randomization, e.g.@: to allow for a more deterministic
39037 debugging experience. On such systems, this packet with a @var{value}
39038 of 1 directs the target to disable address space randomization for
39039 processes subsequently started via @samp{vRun} packets, while a packet
39040 with a @var{value} of 0 tells the target to enable address space
39043 This packet is only available in extended mode (@pxref{extended mode}).
39048 The request succeeded.
39051 An error occurred. @var{nn} are hex digits.
39054 An empty reply indicates that @samp{QDisableRandomization} is not supported
39058 This packet is not probed by default; the remote stub must request it,
39059 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39060 This should only be done on targets that actually support disabling
39061 address space randomization.
39064 @itemx qsThreadInfo
39065 @cindex list active threads, remote request
39066 @cindex @samp{qfThreadInfo} packet
39067 @cindex @samp{qsThreadInfo} packet
39068 Obtain a list of all active thread IDs from the target (OS). Since there
39069 may be too many active threads to fit into one reply packet, this query
39070 works iteratively: it may require more than one query/reply sequence to
39071 obtain the entire list of threads. The first query of the sequence will
39072 be the @samp{qfThreadInfo} query; subsequent queries in the
39073 sequence will be the @samp{qsThreadInfo} query.
39075 NOTE: This packet replaces the @samp{qL} query (see below).
39079 @item m @var{thread-id}
39081 @item m @var{thread-id},@var{thread-id}@dots{}
39082 a comma-separated list of thread IDs
39084 (lower case letter @samp{L}) denotes end of list.
39087 In response to each query, the target will reply with a list of one or
39088 more thread IDs, separated by commas.
39089 @value{GDBN} will respond to each reply with a request for more thread
39090 ids (using the @samp{qs} form of the query), until the target responds
39091 with @samp{l} (lower-case ell, for @dfn{last}).
39092 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
39095 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
39096 @cindex get thread-local storage address, remote request
39097 @cindex @samp{qGetTLSAddr} packet
39098 Fetch the address associated with thread local storage specified
39099 by @var{thread-id}, @var{offset}, and @var{lm}.
39101 @var{thread-id} is the thread ID associated with the
39102 thread for which to fetch the TLS address. @xref{thread-id syntax}.
39104 @var{offset} is the (big endian, hex encoded) offset associated with the
39105 thread local variable. (This offset is obtained from the debug
39106 information associated with the variable.)
39108 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
39109 load module associated with the thread local storage. For example,
39110 a @sc{gnu}/Linux system will pass the link map address of the shared
39111 object associated with the thread local storage under consideration.
39112 Other operating environments may choose to represent the load module
39113 differently, so the precise meaning of this parameter will vary.
39117 @item @var{XX}@dots{}
39118 Hex encoded (big endian) bytes representing the address of the thread
39119 local storage requested.
39122 An error occurred. @var{nn} are hex digits.
39125 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
39128 @item qGetTIBAddr:@var{thread-id}
39129 @cindex get thread information block address
39130 @cindex @samp{qGetTIBAddr} packet
39131 Fetch address of the Windows OS specific Thread Information Block.
39133 @var{thread-id} is the thread ID associated with the thread.
39137 @item @var{XX}@dots{}
39138 Hex encoded (big endian) bytes representing the linear address of the
39139 thread information block.
39142 An error occured. This means that either the thread was not found, or the
39143 address could not be retrieved.
39146 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
39149 @item qL @var{startflag} @var{threadcount} @var{nextthread}
39150 Obtain thread information from RTOS. Where: @var{startflag} (one hex
39151 digit) is one to indicate the first query and zero to indicate a
39152 subsequent query; @var{threadcount} (two hex digits) is the maximum
39153 number of threads the response packet can contain; and @var{nextthread}
39154 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
39155 returned in the response as @var{argthread}.
39157 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
39161 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
39162 Where: @var{count} (two hex digits) is the number of threads being
39163 returned; @var{done} (one hex digit) is zero to indicate more threads
39164 and one indicates no further threads; @var{argthreadid} (eight hex
39165 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
39166 is a sequence of thread IDs from the target. @var{threadid} (eight hex
39167 digits). See @code{remote.c:parse_threadlist_response()}.
39171 @cindex section offsets, remote request
39172 @cindex @samp{qOffsets} packet
39173 Get section offsets that the target used when relocating the downloaded
39178 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
39179 Relocate the @code{Text} section by @var{xxx} from its original address.
39180 Relocate the @code{Data} section by @var{yyy} from its original address.
39181 If the object file format provides segment information (e.g.@: @sc{elf}
39182 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
39183 segments by the supplied offsets.
39185 @emph{Note: while a @code{Bss} offset may be included in the response,
39186 @value{GDBN} ignores this and instead applies the @code{Data} offset
39187 to the @code{Bss} section.}
39189 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
39190 Relocate the first segment of the object file, which conventionally
39191 contains program code, to a starting address of @var{xxx}. If
39192 @samp{DataSeg} is specified, relocate the second segment, which
39193 conventionally contains modifiable data, to a starting address of
39194 @var{yyy}. @value{GDBN} will report an error if the object file
39195 does not contain segment information, or does not contain at least
39196 as many segments as mentioned in the reply. Extra segments are
39197 kept at fixed offsets relative to the last relocated segment.
39200 @item qP @var{mode} @var{thread-id}
39201 @cindex thread information, remote request
39202 @cindex @samp{qP} packet
39203 Returns information on @var{thread-id}. Where: @var{mode} is a hex
39204 encoded 32 bit mode; @var{thread-id} is a thread ID
39205 (@pxref{thread-id syntax}).
39207 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
39210 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
39214 @cindex non-stop mode, remote request
39215 @cindex @samp{QNonStop} packet
39217 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
39218 @xref{Remote Non-Stop}, for more information.
39223 The request succeeded.
39226 An error occurred. @var{nn} are hex digits.
39229 An empty reply indicates that @samp{QNonStop} is not supported by
39233 This packet is not probed by default; the remote stub must request it,
39234 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39235 Use of this packet is controlled by the @code{set non-stop} command;
39236 @pxref{Non-Stop Mode}.
39238 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
39239 @cindex pass signals to inferior, remote request
39240 @cindex @samp{QPassSignals} packet
39241 @anchor{QPassSignals}
39242 Each listed @var{signal} should be passed directly to the inferior process.
39243 Signals are numbered identically to continue packets and stop replies
39244 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
39245 strictly greater than the previous item. These signals do not need to stop
39246 the inferior, or be reported to @value{GDBN}. All other signals should be
39247 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
39248 combine; any earlier @samp{QPassSignals} list is completely replaced by the
39249 new list. This packet improves performance when using @samp{handle
39250 @var{signal} nostop noprint pass}.
39255 The request succeeded.
39258 An error occurred. @var{nn} are hex digits.
39261 An empty reply indicates that @samp{QPassSignals} is not supported by
39265 Use of this packet is controlled by the @code{set remote pass-signals}
39266 command (@pxref{Remote Configuration, set remote pass-signals}).
39267 This packet is not probed by default; the remote stub must request it,
39268 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39270 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
39271 @cindex signals the inferior may see, remote request
39272 @cindex @samp{QProgramSignals} packet
39273 @anchor{QProgramSignals}
39274 Each listed @var{signal} may be delivered to the inferior process.
39275 Others should be silently discarded.
39277 In some cases, the remote stub may need to decide whether to deliver a
39278 signal to the program or not without @value{GDBN} involvement. One
39279 example of that is while detaching --- the program's threads may have
39280 stopped for signals that haven't yet had a chance of being reported to
39281 @value{GDBN}, and so the remote stub can use the signal list specified
39282 by this packet to know whether to deliver or ignore those pending
39285 This does not influence whether to deliver a signal as requested by a
39286 resumption packet (@pxref{vCont packet}).
39288 Signals are numbered identically to continue packets and stop replies
39289 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
39290 strictly greater than the previous item. Multiple
39291 @samp{QProgramSignals} packets do not combine; any earlier
39292 @samp{QProgramSignals} list is completely replaced by the new list.
39297 The request succeeded.
39300 An error occurred. @var{nn} are hex digits.
39303 An empty reply indicates that @samp{QProgramSignals} is not supported
39307 Use of this packet is controlled by the @code{set remote program-signals}
39308 command (@pxref{Remote Configuration, set remote program-signals}).
39309 This packet is not probed by default; the remote stub must request it,
39310 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39312 @item qRcmd,@var{command}
39313 @cindex execute remote command, remote request
39314 @cindex @samp{qRcmd} packet
39315 @var{command} (hex encoded) is passed to the local interpreter for
39316 execution. Invalid commands should be reported using the output
39317 string. Before the final result packet, the target may also respond
39318 with a number of intermediate @samp{O@var{output}} console output
39319 packets. @emph{Implementors should note that providing access to a
39320 stubs's interpreter may have security implications}.
39325 A command response with no output.
39327 A command response with the hex encoded output string @var{OUTPUT}.
39329 Indicate a badly formed request.
39331 An empty reply indicates that @samp{qRcmd} is not recognized.
39334 (Note that the @code{qRcmd} packet's name is separated from the
39335 command by a @samp{,}, not a @samp{:}, contrary to the naming
39336 conventions above. Please don't use this packet as a model for new
39339 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
39340 @cindex searching memory, in remote debugging
39342 @cindex @samp{qSearch:memory} packet
39344 @cindex @samp{qSearch memory} packet
39345 @anchor{qSearch memory}
39346 Search @var{length} bytes at @var{address} for @var{search-pattern}.
39347 @var{address} and @var{length} are encoded in hex.
39348 @var{search-pattern} is a sequence of bytes, hex encoded.
39353 The pattern was not found.
39355 The pattern was found at @var{address}.
39357 A badly formed request or an error was encountered while searching memory.
39359 An empty reply indicates that @samp{qSearch:memory} is not recognized.
39362 @item QStartNoAckMode
39363 @cindex @samp{QStartNoAckMode} packet
39364 @anchor{QStartNoAckMode}
39365 Request that the remote stub disable the normal @samp{+}/@samp{-}
39366 protocol acknowledgments (@pxref{Packet Acknowledgment}).
39371 The stub has switched to no-acknowledgment mode.
39372 @value{GDBN} acknowledges this reponse,
39373 but neither the stub nor @value{GDBN} shall send or expect further
39374 @samp{+}/@samp{-} acknowledgments in the current connection.
39376 An empty reply indicates that the stub does not support no-acknowledgment mode.
39379 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
39380 @cindex supported packets, remote query
39381 @cindex features of the remote protocol
39382 @cindex @samp{qSupported} packet
39383 @anchor{qSupported}
39384 Tell the remote stub about features supported by @value{GDBN}, and
39385 query the stub for features it supports. This packet allows
39386 @value{GDBN} and the remote stub to take advantage of each others'
39387 features. @samp{qSupported} also consolidates multiple feature probes
39388 at startup, to improve @value{GDBN} performance---a single larger
39389 packet performs better than multiple smaller probe packets on
39390 high-latency links. Some features may enable behavior which must not
39391 be on by default, e.g.@: because it would confuse older clients or
39392 stubs. Other features may describe packets which could be
39393 automatically probed for, but are not. These features must be
39394 reported before @value{GDBN} will use them. This ``default
39395 unsupported'' behavior is not appropriate for all packets, but it
39396 helps to keep the initial connection time under control with new
39397 versions of @value{GDBN} which support increasing numbers of packets.
39401 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
39402 The stub supports or does not support each returned @var{stubfeature},
39403 depending on the form of each @var{stubfeature} (see below for the
39406 An empty reply indicates that @samp{qSupported} is not recognized,
39407 or that no features needed to be reported to @value{GDBN}.
39410 The allowed forms for each feature (either a @var{gdbfeature} in the
39411 @samp{qSupported} packet, or a @var{stubfeature} in the response)
39415 @item @var{name}=@var{value}
39416 The remote protocol feature @var{name} is supported, and associated
39417 with the specified @var{value}. The format of @var{value} depends
39418 on the feature, but it must not include a semicolon.
39420 The remote protocol feature @var{name} is supported, and does not
39421 need an associated value.
39423 The remote protocol feature @var{name} is not supported.
39425 The remote protocol feature @var{name} may be supported, and
39426 @value{GDBN} should auto-detect support in some other way when it is
39427 needed. This form will not be used for @var{gdbfeature} notifications,
39428 but may be used for @var{stubfeature} responses.
39431 Whenever the stub receives a @samp{qSupported} request, the
39432 supplied set of @value{GDBN} features should override any previous
39433 request. This allows @value{GDBN} to put the stub in a known
39434 state, even if the stub had previously been communicating with
39435 a different version of @value{GDBN}.
39437 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
39442 This feature indicates whether @value{GDBN} supports multiprocess
39443 extensions to the remote protocol. @value{GDBN} does not use such
39444 extensions unless the stub also reports that it supports them by
39445 including @samp{multiprocess+} in its @samp{qSupported} reply.
39446 @xref{multiprocess extensions}, for details.
39449 This feature indicates that @value{GDBN} supports the XML target
39450 description. If the stub sees @samp{xmlRegisters=} with target
39451 specific strings separated by a comma, it will report register
39455 This feature indicates whether @value{GDBN} supports the
39456 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
39457 instruction reply packet}).
39460 Stubs should ignore any unknown values for
39461 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
39462 packet supports receiving packets of unlimited length (earlier
39463 versions of @value{GDBN} may reject overly long responses). Additional values
39464 for @var{gdbfeature} may be defined in the future to let the stub take
39465 advantage of new features in @value{GDBN}, e.g.@: incompatible
39466 improvements in the remote protocol---the @samp{multiprocess} feature is
39467 an example of such a feature. The stub's reply should be independent
39468 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
39469 describes all the features it supports, and then the stub replies with
39470 all the features it supports.
39472 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
39473 responses, as long as each response uses one of the standard forms.
39475 Some features are flags. A stub which supports a flag feature
39476 should respond with a @samp{+} form response. Other features
39477 require values, and the stub should respond with an @samp{=}
39480 Each feature has a default value, which @value{GDBN} will use if
39481 @samp{qSupported} is not available or if the feature is not mentioned
39482 in the @samp{qSupported} response. The default values are fixed; a
39483 stub is free to omit any feature responses that match the defaults.
39485 Not all features can be probed, but for those which can, the probing
39486 mechanism is useful: in some cases, a stub's internal
39487 architecture may not allow the protocol layer to know some information
39488 about the underlying target in advance. This is especially common in
39489 stubs which may be configured for multiple targets.
39491 These are the currently defined stub features and their properties:
39493 @multitable @columnfractions 0.35 0.2 0.12 0.2
39494 @c NOTE: The first row should be @headitem, but we do not yet require
39495 @c a new enough version of Texinfo (4.7) to use @headitem.
39497 @tab Value Required
39501 @item @samp{PacketSize}
39506 @item @samp{qXfer:auxv:read}
39511 @item @samp{qXfer:btrace:read}
39516 @item @samp{qXfer:features:read}
39521 @item @samp{qXfer:libraries:read}
39526 @item @samp{qXfer:libraries-svr4:read}
39531 @item @samp{augmented-libraries-svr4-read}
39536 @item @samp{qXfer:memory-map:read}
39541 @item @samp{qXfer:sdata:read}
39546 @item @samp{qXfer:spu:read}
39551 @item @samp{qXfer:spu:write}
39556 @item @samp{qXfer:siginfo:read}
39561 @item @samp{qXfer:siginfo:write}
39566 @item @samp{qXfer:threads:read}
39571 @item @samp{qXfer:traceframe-info:read}
39576 @item @samp{qXfer:uib:read}
39581 @item @samp{qXfer:fdpic:read}
39586 @item @samp{Qbtrace:off}
39591 @item @samp{Qbtrace:bts}
39596 @item @samp{QNonStop}
39601 @item @samp{QPassSignals}
39606 @item @samp{QStartNoAckMode}
39611 @item @samp{multiprocess}
39616 @item @samp{ConditionalBreakpoints}
39621 @item @samp{ConditionalTracepoints}
39626 @item @samp{ReverseContinue}
39631 @item @samp{ReverseStep}
39636 @item @samp{TracepointSource}
39641 @item @samp{QAgent}
39646 @item @samp{QAllow}
39651 @item @samp{QDisableRandomization}
39656 @item @samp{EnableDisableTracepoints}
39661 @item @samp{QTBuffer:size}
39666 @item @samp{tracenz}
39671 @item @samp{BreakpointCommands}
39678 These are the currently defined stub features, in more detail:
39681 @cindex packet size, remote protocol
39682 @item PacketSize=@var{bytes}
39683 The remote stub can accept packets up to at least @var{bytes} in
39684 length. @value{GDBN} will send packets up to this size for bulk
39685 transfers, and will never send larger packets. This is a limit on the
39686 data characters in the packet, including the frame and checksum.
39687 There is no trailing NUL byte in a remote protocol packet; if the stub
39688 stores packets in a NUL-terminated format, it should allow an extra
39689 byte in its buffer for the NUL. If this stub feature is not supported,
39690 @value{GDBN} guesses based on the size of the @samp{g} packet response.
39692 @item qXfer:auxv:read
39693 The remote stub understands the @samp{qXfer:auxv:read} packet
39694 (@pxref{qXfer auxiliary vector read}).
39696 @item qXfer:btrace:read
39697 The remote stub understands the @samp{qXfer:btrace:read}
39698 packet (@pxref{qXfer btrace read}).
39700 @item qXfer:features:read
39701 The remote stub understands the @samp{qXfer:features:read} packet
39702 (@pxref{qXfer target description read}).
39704 @item qXfer:libraries:read
39705 The remote stub understands the @samp{qXfer:libraries:read} packet
39706 (@pxref{qXfer library list read}).
39708 @item qXfer:libraries-svr4:read
39709 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
39710 (@pxref{qXfer svr4 library list read}).
39712 @item augmented-libraries-svr4-read
39713 The remote stub understands the augmented form of the
39714 @samp{qXfer:libraries-svr4:read} packet
39715 (@pxref{qXfer svr4 library list read}).
39717 @item qXfer:memory-map:read
39718 The remote stub understands the @samp{qXfer:memory-map:read} packet
39719 (@pxref{qXfer memory map read}).
39721 @item qXfer:sdata:read
39722 The remote stub understands the @samp{qXfer:sdata:read} packet
39723 (@pxref{qXfer sdata read}).
39725 @item qXfer:spu:read
39726 The remote stub understands the @samp{qXfer:spu:read} packet
39727 (@pxref{qXfer spu read}).
39729 @item qXfer:spu:write
39730 The remote stub understands the @samp{qXfer:spu:write} packet
39731 (@pxref{qXfer spu write}).
39733 @item qXfer:siginfo:read
39734 The remote stub understands the @samp{qXfer:siginfo:read} packet
39735 (@pxref{qXfer siginfo read}).
39737 @item qXfer:siginfo:write
39738 The remote stub understands the @samp{qXfer:siginfo:write} packet
39739 (@pxref{qXfer siginfo write}).
39741 @item qXfer:threads:read
39742 The remote stub understands the @samp{qXfer:threads:read} packet
39743 (@pxref{qXfer threads read}).
39745 @item qXfer:traceframe-info:read
39746 The remote stub understands the @samp{qXfer:traceframe-info:read}
39747 packet (@pxref{qXfer traceframe info read}).
39749 @item qXfer:uib:read
39750 The remote stub understands the @samp{qXfer:uib:read}
39751 packet (@pxref{qXfer unwind info block}).
39753 @item qXfer:fdpic:read
39754 The remote stub understands the @samp{qXfer:fdpic:read}
39755 packet (@pxref{qXfer fdpic loadmap read}).
39758 The remote stub understands the @samp{QNonStop} packet
39759 (@pxref{QNonStop}).
39762 The remote stub understands the @samp{QPassSignals} packet
39763 (@pxref{QPassSignals}).
39765 @item QStartNoAckMode
39766 The remote stub understands the @samp{QStartNoAckMode} packet and
39767 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
39770 @anchor{multiprocess extensions}
39771 @cindex multiprocess extensions, in remote protocol
39772 The remote stub understands the multiprocess extensions to the remote
39773 protocol syntax. The multiprocess extensions affect the syntax of
39774 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
39775 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
39776 replies. Note that reporting this feature indicates support for the
39777 syntactic extensions only, not that the stub necessarily supports
39778 debugging of more than one process at a time. The stub must not use
39779 multiprocess extensions in packet replies unless @value{GDBN} has also
39780 indicated it supports them in its @samp{qSupported} request.
39782 @item qXfer:osdata:read
39783 The remote stub understands the @samp{qXfer:osdata:read} packet
39784 ((@pxref{qXfer osdata read}).
39786 @item ConditionalBreakpoints
39787 The target accepts and implements evaluation of conditional expressions
39788 defined for breakpoints. The target will only report breakpoint triggers
39789 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
39791 @item ConditionalTracepoints
39792 The remote stub accepts and implements conditional expressions defined
39793 for tracepoints (@pxref{Tracepoint Conditions}).
39795 @item ReverseContinue
39796 The remote stub accepts and implements the reverse continue packet
39800 The remote stub accepts and implements the reverse step packet
39803 @item TracepointSource
39804 The remote stub understands the @samp{QTDPsrc} packet that supplies
39805 the source form of tracepoint definitions.
39808 The remote stub understands the @samp{QAgent} packet.
39811 The remote stub understands the @samp{QAllow} packet.
39813 @item QDisableRandomization
39814 The remote stub understands the @samp{QDisableRandomization} packet.
39816 @item StaticTracepoint
39817 @cindex static tracepoints, in remote protocol
39818 The remote stub supports static tracepoints.
39820 @item InstallInTrace
39821 @anchor{install tracepoint in tracing}
39822 The remote stub supports installing tracepoint in tracing.
39824 @item EnableDisableTracepoints
39825 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
39826 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
39827 to be enabled and disabled while a trace experiment is running.
39829 @item QTBuffer:size
39830 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
39831 packet that allows to change the size of the trace buffer.
39834 @cindex string tracing, in remote protocol
39835 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
39836 See @ref{Bytecode Descriptions} for details about the bytecode.
39838 @item BreakpointCommands
39839 @cindex breakpoint commands, in remote protocol
39840 The remote stub supports running a breakpoint's command list itself,
39841 rather than reporting the hit to @value{GDBN}.
39844 The remote stub understands the @samp{Qbtrace:off} packet.
39847 The remote stub understands the @samp{Qbtrace:bts} packet.
39852 @cindex symbol lookup, remote request
39853 @cindex @samp{qSymbol} packet
39854 Notify the target that @value{GDBN} is prepared to serve symbol lookup
39855 requests. Accept requests from the target for the values of symbols.
39860 The target does not need to look up any (more) symbols.
39861 @item qSymbol:@var{sym_name}
39862 The target requests the value of symbol @var{sym_name} (hex encoded).
39863 @value{GDBN} may provide the value by using the
39864 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
39868 @item qSymbol:@var{sym_value}:@var{sym_name}
39869 Set the value of @var{sym_name} to @var{sym_value}.
39871 @var{sym_name} (hex encoded) is the name of a symbol whose value the
39872 target has previously requested.
39874 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
39875 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
39881 The target does not need to look up any (more) symbols.
39882 @item qSymbol:@var{sym_name}
39883 The target requests the value of a new symbol @var{sym_name} (hex
39884 encoded). @value{GDBN} will continue to supply the values of symbols
39885 (if available), until the target ceases to request them.
39890 @itemx QTDisconnected
39897 @itemx qTMinFTPILen
39899 @xref{Tracepoint Packets}.
39901 @item qThreadExtraInfo,@var{thread-id}
39902 @cindex thread attributes info, remote request
39903 @cindex @samp{qThreadExtraInfo} packet
39904 Obtain a printable string description of a thread's attributes from
39905 the target OS. @var{thread-id} is a thread ID;
39906 see @ref{thread-id syntax}. This
39907 string may contain anything that the target OS thinks is interesting
39908 for @value{GDBN} to tell the user about the thread. The string is
39909 displayed in @value{GDBN}'s @code{info threads} display. Some
39910 examples of possible thread extra info strings are @samp{Runnable}, or
39911 @samp{Blocked on Mutex}.
39915 @item @var{XX}@dots{}
39916 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
39917 comprising the printable string containing the extra information about
39918 the thread's attributes.
39921 (Note that the @code{qThreadExtraInfo} packet's name is separated from
39922 the command by a @samp{,}, not a @samp{:}, contrary to the naming
39923 conventions above. Please don't use this packet as a model for new
39942 @xref{Tracepoint Packets}.
39944 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
39945 @cindex read special object, remote request
39946 @cindex @samp{qXfer} packet
39947 @anchor{qXfer read}
39948 Read uninterpreted bytes from the target's special data area
39949 identified by the keyword @var{object}. Request @var{length} bytes
39950 starting at @var{offset} bytes into the data. The content and
39951 encoding of @var{annex} is specific to @var{object}; it can supply
39952 additional details about what data to access.
39954 Here are the specific requests of this form defined so far. All
39955 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
39956 formats, listed below.
39959 @item qXfer:auxv:read::@var{offset},@var{length}
39960 @anchor{qXfer auxiliary vector read}
39961 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
39962 auxiliary vector}. Note @var{annex} must be empty.
39964 This packet is not probed by default; the remote stub must request it,
39965 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39967 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
39968 @anchor{qXfer btrace read}
39970 Return a description of the current branch trace.
39971 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
39972 packet may have one of the following values:
39976 Returns all available branch trace.
39979 Returns all available branch trace if the branch trace changed since
39980 the last read request.
39983 Returns the new branch trace since the last read request. Adds a new
39984 block to the end of the trace that begins at zero and ends at the source
39985 location of the first branch in the trace buffer. This extra block is
39986 used to stitch traces together.
39988 If the trace buffer overflowed, returns an error indicating the overflow.
39991 This packet is not probed by default; the remote stub must request it
39992 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39994 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
39995 @anchor{qXfer target description read}
39996 Access the @dfn{target description}. @xref{Target Descriptions}. The
39997 annex specifies which XML document to access. The main description is
39998 always loaded from the @samp{target.xml} annex.
40000 This packet is not probed by default; the remote stub must request it,
40001 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40003 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
40004 @anchor{qXfer library list read}
40005 Access the target's list of loaded libraries. @xref{Library List Format}.
40006 The annex part of the generic @samp{qXfer} packet must be empty
40007 (@pxref{qXfer read}).
40009 Targets which maintain a list of libraries in the program's memory do
40010 not need to implement this packet; it is designed for platforms where
40011 the operating system manages the list of loaded libraries.
40013 This packet is not probed by default; the remote stub must request it,
40014 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40016 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
40017 @anchor{qXfer svr4 library list read}
40018 Access the target's list of loaded libraries when the target is an SVR4
40019 platform. @xref{Library List Format for SVR4 Targets}. The annex part
40020 of the generic @samp{qXfer} packet must be empty unless the remote
40021 stub indicated it supports the augmented form of this packet
40022 by supplying an appropriate @samp{qSupported} response
40023 (@pxref{qXfer read}, @ref{qSupported}).
40025 This packet is optional for better performance on SVR4 targets.
40026 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
40028 This packet is not probed by default; the remote stub must request it,
40029 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40031 If the remote stub indicates it supports the augmented form of this
40032 packet then the annex part of the generic @samp{qXfer} packet may
40033 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
40034 arguments. The currently supported arguments are:
40037 @item start=@var{address}
40038 A hexadecimal number specifying the address of the @samp{struct
40039 link_map} to start reading the library list from. If unset or zero
40040 then the first @samp{struct link_map} in the library list will be
40041 chosen as the starting point.
40043 @item prev=@var{address}
40044 A hexadecimal number specifying the address of the @samp{struct
40045 link_map} immediately preceding the @samp{struct link_map}
40046 specified by the @samp{start} argument. If unset or zero then
40047 the remote stub will expect that no @samp{struct link_map}
40048 exists prior to the starting point.
40052 Arguments that are not understood by the remote stub will be silently
40055 @item qXfer:memory-map:read::@var{offset},@var{length}
40056 @anchor{qXfer memory map read}
40057 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
40058 annex part of the generic @samp{qXfer} packet must be empty
40059 (@pxref{qXfer read}).
40061 This packet is not probed by default; the remote stub must request it,
40062 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40064 @item qXfer:sdata:read::@var{offset},@var{length}
40065 @anchor{qXfer sdata read}
40067 Read contents of the extra collected static tracepoint marker
40068 information. The annex part of the generic @samp{qXfer} packet must
40069 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
40072 This packet is not probed by default; the remote stub must request it,
40073 by supplying an appropriate @samp{qSupported} response
40074 (@pxref{qSupported}).
40076 @item qXfer:siginfo:read::@var{offset},@var{length}
40077 @anchor{qXfer siginfo read}
40078 Read contents of the extra signal information on the target
40079 system. The annex part of the generic @samp{qXfer} packet must be
40080 empty (@pxref{qXfer read}).
40082 This packet is not probed by default; the remote stub must request it,
40083 by supplying an appropriate @samp{qSupported} response
40084 (@pxref{qSupported}).
40086 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
40087 @anchor{qXfer spu read}
40088 Read contents of an @code{spufs} file on the target system. The
40089 annex specifies which file to read; it must be of the form
40090 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
40091 in the target process, and @var{name} identifes the @code{spufs} file
40092 in that context to be accessed.
40094 This packet is not probed by default; the remote stub must request it,
40095 by supplying an appropriate @samp{qSupported} response
40096 (@pxref{qSupported}).
40098 @item qXfer:threads:read::@var{offset},@var{length}
40099 @anchor{qXfer threads read}
40100 Access the list of threads on target. @xref{Thread List Format}. The
40101 annex part of the generic @samp{qXfer} packet must be empty
40102 (@pxref{qXfer read}).
40104 This packet is not probed by default; the remote stub must request it,
40105 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40107 @item qXfer:traceframe-info:read::@var{offset},@var{length}
40108 @anchor{qXfer traceframe info read}
40110 Return a description of the current traceframe's contents.
40111 @xref{Traceframe Info Format}. The annex part of the generic
40112 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
40114 This packet is not probed by default; the remote stub must request it,
40115 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40117 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
40118 @anchor{qXfer unwind info block}
40120 Return the unwind information block for @var{pc}. This packet is used
40121 on OpenVMS/ia64 to ask the kernel unwind information.
40123 This packet is not probed by default.
40125 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
40126 @anchor{qXfer fdpic loadmap read}
40127 Read contents of @code{loadmap}s on the target system. The
40128 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
40129 executable @code{loadmap} or interpreter @code{loadmap} to read.
40131 This packet is not probed by default; the remote stub must request it,
40132 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40134 @item qXfer:osdata:read::@var{offset},@var{length}
40135 @anchor{qXfer osdata read}
40136 Access the target's @dfn{operating system information}.
40137 @xref{Operating System Information}.
40144 Data @var{data} (@pxref{Binary Data}) has been read from the
40145 target. There may be more data at a higher address (although
40146 it is permitted to return @samp{m} even for the last valid
40147 block of data, as long as at least one byte of data was read).
40148 @var{data} may have fewer bytes than the @var{length} in the
40152 Data @var{data} (@pxref{Binary Data}) has been read from the target.
40153 There is no more data to be read. @var{data} may have fewer bytes
40154 than the @var{length} in the request.
40157 The @var{offset} in the request is at the end of the data.
40158 There is no more data to be read.
40161 The request was malformed, or @var{annex} was invalid.
40164 The offset was invalid, or there was an error encountered reading the data.
40165 @var{nn} is a hex-encoded @code{errno} value.
40168 An empty reply indicates the @var{object} string was not recognized by
40169 the stub, or that the object does not support reading.
40172 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
40173 @cindex write data into object, remote request
40174 @anchor{qXfer write}
40175 Write uninterpreted bytes into the target's special data area
40176 identified by the keyword @var{object}, starting at @var{offset} bytes
40177 into the data. @var{data}@dots{} is the binary-encoded data
40178 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
40179 is specific to @var{object}; it can supply additional details about what data
40182 Here are the specific requests of this form defined so far. All
40183 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
40184 formats, listed below.
40187 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
40188 @anchor{qXfer siginfo write}
40189 Write @var{data} to the extra signal information on the target system.
40190 The annex part of the generic @samp{qXfer} packet must be
40191 empty (@pxref{qXfer write}).
40193 This packet is not probed by default; the remote stub must request it,
40194 by supplying an appropriate @samp{qSupported} response
40195 (@pxref{qSupported}).
40197 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
40198 @anchor{qXfer spu write}
40199 Write @var{data} to an @code{spufs} file on the target system. The
40200 annex specifies which file to write; it must be of the form
40201 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
40202 in the target process, and @var{name} identifes the @code{spufs} file
40203 in that context to be accessed.
40205 This packet is not probed by default; the remote stub must request it,
40206 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40212 @var{nn} (hex encoded) is the number of bytes written.
40213 This may be fewer bytes than supplied in the request.
40216 The request was malformed, or @var{annex} was invalid.
40219 The offset was invalid, or there was an error encountered writing the data.
40220 @var{nn} is a hex-encoded @code{errno} value.
40223 An empty reply indicates the @var{object} string was not
40224 recognized by the stub, or that the object does not support writing.
40227 @item qXfer:@var{object}:@var{operation}:@dots{}
40228 Requests of this form may be added in the future. When a stub does
40229 not recognize the @var{object} keyword, or its support for
40230 @var{object} does not recognize the @var{operation} keyword, the stub
40231 must respond with an empty packet.
40233 @item qAttached:@var{pid}
40234 @cindex query attached, remote request
40235 @cindex @samp{qAttached} packet
40236 Return an indication of whether the remote server attached to an
40237 existing process or created a new process. When the multiprocess
40238 protocol extensions are supported (@pxref{multiprocess extensions}),
40239 @var{pid} is an integer in hexadecimal format identifying the target
40240 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
40241 the query packet will be simplified as @samp{qAttached}.
40243 This query is used, for example, to know whether the remote process
40244 should be detached or killed when a @value{GDBN} session is ended with
40245 the @code{quit} command.
40250 The remote server attached to an existing process.
40252 The remote server created a new process.
40254 A badly formed request or an error was encountered.
40258 Enable branch tracing for the current thread using bts tracing.
40263 Branch tracing has been enabled.
40265 A badly formed request or an error was encountered.
40269 Disable branch tracing for the current thread.
40274 Branch tracing has been disabled.
40276 A badly formed request or an error was encountered.
40281 @node Architecture-Specific Protocol Details
40282 @section Architecture-Specific Protocol Details
40284 This section describes how the remote protocol is applied to specific
40285 target architectures. Also see @ref{Standard Target Features}, for
40286 details of XML target descriptions for each architecture.
40289 * ARM-Specific Protocol Details::
40290 * MIPS-Specific Protocol Details::
40293 @node ARM-Specific Protocol Details
40294 @subsection @acronym{ARM}-specific Protocol Details
40297 * ARM Breakpoint Kinds::
40300 @node ARM Breakpoint Kinds
40301 @subsubsection @acronym{ARM} Breakpoint Kinds
40302 @cindex breakpoint kinds, @acronym{ARM}
40304 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
40309 16-bit Thumb mode breakpoint.
40312 32-bit Thumb mode (Thumb-2) breakpoint.
40315 32-bit @acronym{ARM} mode breakpoint.
40319 @node MIPS-Specific Protocol Details
40320 @subsection @acronym{MIPS}-specific Protocol Details
40323 * MIPS Register packet Format::
40324 * MIPS Breakpoint Kinds::
40327 @node MIPS Register packet Format
40328 @subsubsection @acronym{MIPS} Register Packet Format
40329 @cindex register packet format, @acronym{MIPS}
40331 The following @code{g}/@code{G} packets have previously been defined.
40332 In the below, some thirty-two bit registers are transferred as
40333 sixty-four bits. Those registers should be zero/sign extended (which?)
40334 to fill the space allocated. Register bytes are transferred in target
40335 byte order. The two nibbles within a register byte are transferred
40336 most-significant -- least-significant.
40341 All registers are transferred as thirty-two bit quantities in the order:
40342 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
40343 registers; fsr; fir; fp.
40346 All registers are transferred as sixty-four bit quantities (including
40347 thirty-two bit registers such as @code{sr}). The ordering is the same
40352 @node MIPS Breakpoint Kinds
40353 @subsubsection @acronym{MIPS} Breakpoint Kinds
40354 @cindex breakpoint kinds, @acronym{MIPS}
40356 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
40361 16-bit @acronym{MIPS16} mode breakpoint.
40364 16-bit @acronym{microMIPS} mode breakpoint.
40367 32-bit standard @acronym{MIPS} mode breakpoint.
40370 32-bit @acronym{microMIPS} mode breakpoint.
40374 @node Tracepoint Packets
40375 @section Tracepoint Packets
40376 @cindex tracepoint packets
40377 @cindex packets, tracepoint
40379 Here we describe the packets @value{GDBN} uses to implement
40380 tracepoints (@pxref{Tracepoints}).
40384 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
40385 @cindex @samp{QTDP} packet
40386 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
40387 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
40388 the tracepoint is disabled. @var{step} is the tracepoint's step
40389 count, and @var{pass} is its pass count. If an @samp{F} is present,
40390 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
40391 the number of bytes that the target should copy elsewhere to make room
40392 for the tracepoint. If an @samp{X} is present, it introduces a
40393 tracepoint condition, which consists of a hexadecimal length, followed
40394 by a comma and hex-encoded bytes, in a manner similar to action
40395 encodings as described below. If the trailing @samp{-} is present,
40396 further @samp{QTDP} packets will follow to specify this tracepoint's
40402 The packet was understood and carried out.
40404 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
40406 The packet was not recognized.
40409 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
40410 Define actions to be taken when a tracepoint is hit. @var{n} and
40411 @var{addr} must be the same as in the initial @samp{QTDP} packet for
40412 this tracepoint. This packet may only be sent immediately after
40413 another @samp{QTDP} packet that ended with a @samp{-}. If the
40414 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
40415 specifying more actions for this tracepoint.
40417 In the series of action packets for a given tracepoint, at most one
40418 can have an @samp{S} before its first @var{action}. If such a packet
40419 is sent, it and the following packets define ``while-stepping''
40420 actions. Any prior packets define ordinary actions --- that is, those
40421 taken when the tracepoint is first hit. If no action packet has an
40422 @samp{S}, then all the packets in the series specify ordinary
40423 tracepoint actions.
40425 The @samp{@var{action}@dots{}} portion of the packet is a series of
40426 actions, concatenated without separators. Each action has one of the
40432 Collect the registers whose bits are set in @var{mask}. @var{mask} is
40433 a hexadecimal number whose @var{i}'th bit is set if register number
40434 @var{i} should be collected. (The least significant bit is numbered
40435 zero.) Note that @var{mask} may be any number of digits long; it may
40436 not fit in a 32-bit word.
40438 @item M @var{basereg},@var{offset},@var{len}
40439 Collect @var{len} bytes of memory starting at the address in register
40440 number @var{basereg}, plus @var{offset}. If @var{basereg} is
40441 @samp{-1}, then the range has a fixed address: @var{offset} is the
40442 address of the lowest byte to collect. The @var{basereg},
40443 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
40444 values (the @samp{-1} value for @var{basereg} is a special case).
40446 @item X @var{len},@var{expr}
40447 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
40448 it directs. @var{expr} is an agent expression, as described in
40449 @ref{Agent Expressions}. Each byte of the expression is encoded as a
40450 two-digit hex number in the packet; @var{len} is the number of bytes
40451 in the expression (and thus one-half the number of hex digits in the
40456 Any number of actions may be packed together in a single @samp{QTDP}
40457 packet, as long as the packet does not exceed the maximum packet
40458 length (400 bytes, for many stubs). There may be only one @samp{R}
40459 action per tracepoint, and it must precede any @samp{M} or @samp{X}
40460 actions. Any registers referred to by @samp{M} and @samp{X} actions
40461 must be collected by a preceding @samp{R} action. (The
40462 ``while-stepping'' actions are treated as if they were attached to a
40463 separate tracepoint, as far as these restrictions are concerned.)
40468 The packet was understood and carried out.
40470 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
40472 The packet was not recognized.
40475 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
40476 @cindex @samp{QTDPsrc} packet
40477 Specify a source string of tracepoint @var{n} at address @var{addr}.
40478 This is useful to get accurate reproduction of the tracepoints
40479 originally downloaded at the beginning of the trace run. @var{type}
40480 is the name of the tracepoint part, such as @samp{cond} for the
40481 tracepoint's conditional expression (see below for a list of types), while
40482 @var{bytes} is the string, encoded in hexadecimal.
40484 @var{start} is the offset of the @var{bytes} within the overall source
40485 string, while @var{slen} is the total length of the source string.
40486 This is intended for handling source strings that are longer than will
40487 fit in a single packet.
40488 @c Add detailed example when this info is moved into a dedicated
40489 @c tracepoint descriptions section.
40491 The available string types are @samp{at} for the location,
40492 @samp{cond} for the conditional, and @samp{cmd} for an action command.
40493 @value{GDBN} sends a separate packet for each command in the action
40494 list, in the same order in which the commands are stored in the list.
40496 The target does not need to do anything with source strings except
40497 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
40500 Although this packet is optional, and @value{GDBN} will only send it
40501 if the target replies with @samp{TracepointSource} @xref{General
40502 Query Packets}, it makes both disconnected tracing and trace files
40503 much easier to use. Otherwise the user must be careful that the
40504 tracepoints in effect while looking at trace frames are identical to
40505 the ones in effect during the trace run; even a small discrepancy
40506 could cause @samp{tdump} not to work, or a particular trace frame not
40509 @item QTDV:@var{n}:@var{value}
40510 @cindex define trace state variable, remote request
40511 @cindex @samp{QTDV} packet
40512 Create a new trace state variable, number @var{n}, with an initial
40513 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
40514 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
40515 the option of not using this packet for initial values of zero; the
40516 target should simply create the trace state variables as they are
40517 mentioned in expressions.
40519 @item QTFrame:@var{n}
40520 @cindex @samp{QTFrame} packet
40521 Select the @var{n}'th tracepoint frame from the buffer, and use the
40522 register and memory contents recorded there to answer subsequent
40523 request packets from @value{GDBN}.
40525 A successful reply from the stub indicates that the stub has found the
40526 requested frame. The response is a series of parts, concatenated
40527 without separators, describing the frame we selected. Each part has
40528 one of the following forms:
40532 The selected frame is number @var{n} in the trace frame buffer;
40533 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
40534 was no frame matching the criteria in the request packet.
40537 The selected trace frame records a hit of tracepoint number @var{t};
40538 @var{t} is a hexadecimal number.
40542 @item QTFrame:pc:@var{addr}
40543 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40544 currently selected frame whose PC is @var{addr};
40545 @var{addr} is a hexadecimal number.
40547 @item QTFrame:tdp:@var{t}
40548 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40549 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
40550 is a hexadecimal number.
40552 @item QTFrame:range:@var{start}:@var{end}
40553 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40554 currently selected frame whose PC is between @var{start} (inclusive)
40555 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
40558 @item QTFrame:outside:@var{start}:@var{end}
40559 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
40560 frame @emph{outside} the given range of addresses (exclusive).
40563 @cindex @samp{qTMinFTPILen} packet
40564 This packet requests the minimum length of instruction at which a fast
40565 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
40566 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
40567 it depends on the target system being able to create trampolines in
40568 the first 64K of memory, which might or might not be possible for that
40569 system. So the reply to this packet will be 4 if it is able to
40576 The minimum instruction length is currently unknown.
40578 The minimum instruction length is @var{length}, where @var{length} is greater
40579 or equal to 1. @var{length} is a hexadecimal number. A reply of 1 means
40580 that a fast tracepoint may be placed on any instruction regardless of size.
40582 An error has occurred.
40584 An empty reply indicates that the request is not supported by the stub.
40588 @cindex @samp{QTStart} packet
40589 Begin the tracepoint experiment. Begin collecting data from
40590 tracepoint hits in the trace frame buffer. This packet supports the
40591 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
40592 instruction reply packet}).
40595 @cindex @samp{QTStop} packet
40596 End the tracepoint experiment. Stop collecting trace frames.
40598 @item QTEnable:@var{n}:@var{addr}
40600 @cindex @samp{QTEnable} packet
40601 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
40602 experiment. If the tracepoint was previously disabled, then collection
40603 of data from it will resume.
40605 @item QTDisable:@var{n}:@var{addr}
40607 @cindex @samp{QTDisable} packet
40608 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
40609 experiment. No more data will be collected from the tracepoint unless
40610 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
40613 @cindex @samp{QTinit} packet
40614 Clear the table of tracepoints, and empty the trace frame buffer.
40616 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
40617 @cindex @samp{QTro} packet
40618 Establish the given ranges of memory as ``transparent''. The stub
40619 will answer requests for these ranges from memory's current contents,
40620 if they were not collected as part of the tracepoint hit.
40622 @value{GDBN} uses this to mark read-only regions of memory, like those
40623 containing program code. Since these areas never change, they should
40624 still have the same contents they did when the tracepoint was hit, so
40625 there's no reason for the stub to refuse to provide their contents.
40627 @item QTDisconnected:@var{value}
40628 @cindex @samp{QTDisconnected} packet
40629 Set the choice to what to do with the tracing run when @value{GDBN}
40630 disconnects from the target. A @var{value} of 1 directs the target to
40631 continue the tracing run, while 0 tells the target to stop tracing if
40632 @value{GDBN} is no longer in the picture.
40635 @cindex @samp{qTStatus} packet
40636 Ask the stub if there is a trace experiment running right now.
40638 The reply has the form:
40642 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
40643 @var{running} is a single digit @code{1} if the trace is presently
40644 running, or @code{0} if not. It is followed by semicolon-separated
40645 optional fields that an agent may use to report additional status.
40649 If the trace is not running, the agent may report any of several
40650 explanations as one of the optional fields:
40655 No trace has been run yet.
40657 @item tstop[:@var{text}]:0
40658 The trace was stopped by a user-originated stop command. The optional
40659 @var{text} field is a user-supplied string supplied as part of the
40660 stop command (for instance, an explanation of why the trace was
40661 stopped manually). It is hex-encoded.
40664 The trace stopped because the trace buffer filled up.
40666 @item tdisconnected:0
40667 The trace stopped because @value{GDBN} disconnected from the target.
40669 @item tpasscount:@var{tpnum}
40670 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
40672 @item terror:@var{text}:@var{tpnum}
40673 The trace stopped because tracepoint @var{tpnum} had an error. The
40674 string @var{text} is available to describe the nature of the error
40675 (for instance, a divide by zero in the condition expression).
40676 @var{text} is hex encoded.
40679 The trace stopped for some other reason.
40683 Additional optional fields supply statistical and other information.
40684 Although not required, they are extremely useful for users monitoring
40685 the progress of a trace run. If a trace has stopped, and these
40686 numbers are reported, they must reflect the state of the just-stopped
40691 @item tframes:@var{n}
40692 The number of trace frames in the buffer.
40694 @item tcreated:@var{n}
40695 The total number of trace frames created during the run. This may
40696 be larger than the trace frame count, if the buffer is circular.
40698 @item tsize:@var{n}
40699 The total size of the trace buffer, in bytes.
40701 @item tfree:@var{n}
40702 The number of bytes still unused in the buffer.
40704 @item circular:@var{n}
40705 The value of the circular trace buffer flag. @code{1} means that the
40706 trace buffer is circular and old trace frames will be discarded if
40707 necessary to make room, @code{0} means that the trace buffer is linear
40710 @item disconn:@var{n}
40711 The value of the disconnected tracing flag. @code{1} means that
40712 tracing will continue after @value{GDBN} disconnects, @code{0} means
40713 that the trace run will stop.
40717 @item qTP:@var{tp}:@var{addr}
40718 @cindex tracepoint status, remote request
40719 @cindex @samp{qTP} packet
40720 Ask the stub for the current state of tracepoint number @var{tp} at
40721 address @var{addr}.
40725 @item V@var{hits}:@var{usage}
40726 The tracepoint has been hit @var{hits} times so far during the trace
40727 run, and accounts for @var{usage} in the trace buffer. Note that
40728 @code{while-stepping} steps are not counted as separate hits, but the
40729 steps' space consumption is added into the usage number.
40733 @item qTV:@var{var}
40734 @cindex trace state variable value, remote request
40735 @cindex @samp{qTV} packet
40736 Ask the stub for the value of the trace state variable number @var{var}.
40741 The value of the variable is @var{value}. This will be the current
40742 value of the variable if the user is examining a running target, or a
40743 saved value if the variable was collected in the trace frame that the
40744 user is looking at. Note that multiple requests may result in
40745 different reply values, such as when requesting values while the
40746 program is running.
40749 The value of the variable is unknown. This would occur, for example,
40750 if the user is examining a trace frame in which the requested variable
40755 @cindex @samp{qTfP} packet
40757 @cindex @samp{qTsP} packet
40758 These packets request data about tracepoints that are being used by
40759 the target. @value{GDBN} sends @code{qTfP} to get the first piece
40760 of data, and multiple @code{qTsP} to get additional pieces. Replies
40761 to these packets generally take the form of the @code{QTDP} packets
40762 that define tracepoints. (FIXME add detailed syntax)
40765 @cindex @samp{qTfV} packet
40767 @cindex @samp{qTsV} packet
40768 These packets request data about trace state variables that are on the
40769 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
40770 and multiple @code{qTsV} to get additional variables. Replies to
40771 these packets follow the syntax of the @code{QTDV} packets that define
40772 trace state variables.
40778 @cindex @samp{qTfSTM} packet
40779 @cindex @samp{qTsSTM} packet
40780 These packets request data about static tracepoint markers that exist
40781 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
40782 first piece of data, and multiple @code{qTsSTM} to get additional
40783 pieces. Replies to these packets take the following form:
40787 @item m @var{address}:@var{id}:@var{extra}
40789 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
40790 a comma-separated list of markers
40792 (lower case letter @samp{L}) denotes end of list.
40794 An error occurred. @var{nn} are hex digits.
40796 An empty reply indicates that the request is not supported by the
40800 @var{address} is encoded in hex.
40801 @var{id} and @var{extra} are strings encoded in hex.
40803 In response to each query, the target will reply with a list of one or
40804 more markers, separated by commas. @value{GDBN} will respond to each
40805 reply with a request for more markers (using the @samp{qs} form of the
40806 query), until the target responds with @samp{l} (lower-case ell, for
40809 @item qTSTMat:@var{address}
40811 @cindex @samp{qTSTMat} packet
40812 This packets requests data about static tracepoint markers in the
40813 target program at @var{address}. Replies to this packet follow the
40814 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
40815 tracepoint markers.
40817 @item QTSave:@var{filename}
40818 @cindex @samp{QTSave} packet
40819 This packet directs the target to save trace data to the file name
40820 @var{filename} in the target's filesystem. @var{filename} is encoded
40821 as a hex string; the interpretation of the file name (relative vs
40822 absolute, wild cards, etc) is up to the target.
40824 @item qTBuffer:@var{offset},@var{len}
40825 @cindex @samp{qTBuffer} packet
40826 Return up to @var{len} bytes of the current contents of trace buffer,
40827 starting at @var{offset}. The trace buffer is treated as if it were
40828 a contiguous collection of traceframes, as per the trace file format.
40829 The reply consists as many hex-encoded bytes as the target can deliver
40830 in a packet; it is not an error to return fewer than were asked for.
40831 A reply consisting of just @code{l} indicates that no bytes are
40834 @item QTBuffer:circular:@var{value}
40835 This packet directs the target to use a circular trace buffer if
40836 @var{value} is 1, or a linear buffer if the value is 0.
40838 @item QTBuffer:size:@var{size}
40839 @anchor{QTBuffer-size}
40840 @cindex @samp{QTBuffer size} packet
40841 This packet directs the target to make the trace buffer be of size
40842 @var{size} if possible. A value of @code{-1} tells the target to
40843 use whatever size it prefers.
40845 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
40846 @cindex @samp{QTNotes} packet
40847 This packet adds optional textual notes to the trace run. Allowable
40848 types include @code{user}, @code{notes}, and @code{tstop}, the
40849 @var{text} fields are arbitrary strings, hex-encoded.
40853 @subsection Relocate instruction reply packet
40854 When installing fast tracepoints in memory, the target may need to
40855 relocate the instruction currently at the tracepoint address to a
40856 different address in memory. For most instructions, a simple copy is
40857 enough, but, for example, call instructions that implicitly push the
40858 return address on the stack, and relative branches or other
40859 PC-relative instructions require offset adjustment, so that the effect
40860 of executing the instruction at a different address is the same as if
40861 it had executed in the original location.
40863 In response to several of the tracepoint packets, the target may also
40864 respond with a number of intermediate @samp{qRelocInsn} request
40865 packets before the final result packet, to have @value{GDBN} handle
40866 this relocation operation. If a packet supports this mechanism, its
40867 documentation will explicitly say so. See for example the above
40868 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
40869 format of the request is:
40872 @item qRelocInsn:@var{from};@var{to}
40874 This requests @value{GDBN} to copy instruction at address @var{from}
40875 to address @var{to}, possibly adjusted so that executing the
40876 instruction at @var{to} has the same effect as executing it at
40877 @var{from}. @value{GDBN} writes the adjusted instruction to target
40878 memory starting at @var{to}.
40883 @item qRelocInsn:@var{adjusted_size}
40884 Informs the stub the relocation is complete. @var{adjusted_size} is
40885 the length in bytes of resulting relocated instruction sequence.
40887 A badly formed request was detected, or an error was encountered while
40888 relocating the instruction.
40891 @node Host I/O Packets
40892 @section Host I/O Packets
40893 @cindex Host I/O, remote protocol
40894 @cindex file transfer, remote protocol
40896 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
40897 operations on the far side of a remote link. For example, Host I/O is
40898 used to upload and download files to a remote target with its own
40899 filesystem. Host I/O uses the same constant values and data structure
40900 layout as the target-initiated File-I/O protocol. However, the
40901 Host I/O packets are structured differently. The target-initiated
40902 protocol relies on target memory to store parameters and buffers.
40903 Host I/O requests are initiated by @value{GDBN}, and the
40904 target's memory is not involved. @xref{File-I/O Remote Protocol
40905 Extension}, for more details on the target-initiated protocol.
40907 The Host I/O request packets all encode a single operation along with
40908 its arguments. They have this format:
40912 @item vFile:@var{operation}: @var{parameter}@dots{}
40913 @var{operation} is the name of the particular request; the target
40914 should compare the entire packet name up to the second colon when checking
40915 for a supported operation. The format of @var{parameter} depends on
40916 the operation. Numbers are always passed in hexadecimal. Negative
40917 numbers have an explicit minus sign (i.e.@: two's complement is not
40918 used). Strings (e.g.@: filenames) are encoded as a series of
40919 hexadecimal bytes. The last argument to a system call may be a
40920 buffer of escaped binary data (@pxref{Binary Data}).
40924 The valid responses to Host I/O packets are:
40928 @item F @var{result} [, @var{errno}] [; @var{attachment}]
40929 @var{result} is the integer value returned by this operation, usually
40930 non-negative for success and -1 for errors. If an error has occured,
40931 @var{errno} will be included in the result. @var{errno} will have a
40932 value defined by the File-I/O protocol (@pxref{Errno Values}). For
40933 operations which return data, @var{attachment} supplies the data as a
40934 binary buffer. Binary buffers in response packets are escaped in the
40935 normal way (@pxref{Binary Data}). See the individual packet
40936 documentation for the interpretation of @var{result} and
40940 An empty response indicates that this operation is not recognized.
40944 These are the supported Host I/O operations:
40947 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
40948 Open a file at @var{pathname} and return a file descriptor for it, or
40949 return -1 if an error occurs. @var{pathname} is a string,
40950 @var{flags} is an integer indicating a mask of open flags
40951 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
40952 of mode bits to use if the file is created (@pxref{mode_t Values}).
40953 @xref{open}, for details of the open flags and mode values.
40955 @item vFile:close: @var{fd}
40956 Close the open file corresponding to @var{fd} and return 0, or
40957 -1 if an error occurs.
40959 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
40960 Read data from the open file corresponding to @var{fd}. Up to
40961 @var{count} bytes will be read from the file, starting at @var{offset}
40962 relative to the start of the file. The target may read fewer bytes;
40963 common reasons include packet size limits and an end-of-file
40964 condition. The number of bytes read is returned. Zero should only be
40965 returned for a successful read at the end of the file, or if
40966 @var{count} was zero.
40968 The data read should be returned as a binary attachment on success.
40969 If zero bytes were read, the response should include an empty binary
40970 attachment (i.e.@: a trailing semicolon). The return value is the
40971 number of target bytes read; the binary attachment may be longer if
40972 some characters were escaped.
40974 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
40975 Write @var{data} (a binary buffer) to the open file corresponding
40976 to @var{fd}. Start the write at @var{offset} from the start of the
40977 file. Unlike many @code{write} system calls, there is no
40978 separate @var{count} argument; the length of @var{data} in the
40979 packet is used. @samp{vFile:write} returns the number of bytes written,
40980 which may be shorter than the length of @var{data}, or -1 if an
40983 @item vFile:unlink: @var{pathname}
40984 Delete the file at @var{pathname} on the target. Return 0,
40985 or -1 if an error occurs. @var{pathname} is a string.
40987 @item vFile:readlink: @var{filename}
40988 Read value of symbolic link @var{filename} on the target. Return
40989 the number of bytes read, or -1 if an error occurs.
40991 The data read should be returned as a binary attachment on success.
40992 If zero bytes were read, the response should include an empty binary
40993 attachment (i.e.@: a trailing semicolon). The return value is the
40994 number of target bytes read; the binary attachment may be longer if
40995 some characters were escaped.
41000 @section Interrupts
41001 @cindex interrupts (remote protocol)
41003 When a program on the remote target is running, @value{GDBN} may
41004 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
41005 a @code{BREAK} followed by @code{g},
41006 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
41008 The precise meaning of @code{BREAK} is defined by the transport
41009 mechanism and may, in fact, be undefined. @value{GDBN} does not
41010 currently define a @code{BREAK} mechanism for any of the network
41011 interfaces except for TCP, in which case @value{GDBN} sends the
41012 @code{telnet} BREAK sequence.
41014 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
41015 transport mechanisms. It is represented by sending the single byte
41016 @code{0x03} without any of the usual packet overhead described in
41017 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
41018 transmitted as part of a packet, it is considered to be packet data
41019 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
41020 (@pxref{X packet}), used for binary downloads, may include an unescaped
41021 @code{0x03} as part of its packet.
41023 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
41024 When Linux kernel receives this sequence from serial port,
41025 it stops execution and connects to gdb.
41027 Stubs are not required to recognize these interrupt mechanisms and the
41028 precise meaning associated with receipt of the interrupt is
41029 implementation defined. If the target supports debugging of multiple
41030 threads and/or processes, it should attempt to interrupt all
41031 currently-executing threads and processes.
41032 If the stub is successful at interrupting the
41033 running program, it should send one of the stop
41034 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
41035 of successfully stopping the program in all-stop mode, and a stop reply
41036 for each stopped thread in non-stop mode.
41037 Interrupts received while the
41038 program is stopped are discarded.
41040 @node Notification Packets
41041 @section Notification Packets
41042 @cindex notification packets
41043 @cindex packets, notification
41045 The @value{GDBN} remote serial protocol includes @dfn{notifications},
41046 packets that require no acknowledgment. Both the GDB and the stub
41047 may send notifications (although the only notifications defined at
41048 present are sent by the stub). Notifications carry information
41049 without incurring the round-trip latency of an acknowledgment, and so
41050 are useful for low-impact communications where occasional packet loss
41053 A notification packet has the form @samp{% @var{data} #
41054 @var{checksum}}, where @var{data} is the content of the notification,
41055 and @var{checksum} is a checksum of @var{data}, computed and formatted
41056 as for ordinary @value{GDBN} packets. A notification's @var{data}
41057 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
41058 receiving a notification, the recipient sends no @samp{+} or @samp{-}
41059 to acknowledge the notification's receipt or to report its corruption.
41061 Every notification's @var{data} begins with a name, which contains no
41062 colon characters, followed by a colon character.
41064 Recipients should silently ignore corrupted notifications and
41065 notifications they do not understand. Recipients should restart
41066 timeout periods on receipt of a well-formed notification, whether or
41067 not they understand it.
41069 Senders should only send the notifications described here when this
41070 protocol description specifies that they are permitted. In the
41071 future, we may extend the protocol to permit existing notifications in
41072 new contexts; this rule helps older senders avoid confusing newer
41075 (Older versions of @value{GDBN} ignore bytes received until they see
41076 the @samp{$} byte that begins an ordinary packet, so new stubs may
41077 transmit notifications without fear of confusing older clients. There
41078 are no notifications defined for @value{GDBN} to send at the moment, but we
41079 assume that most older stubs would ignore them, as well.)
41081 Each notification is comprised of three parts:
41083 @item @var{name}:@var{event}
41084 The notification packet is sent by the side that initiates the
41085 exchange (currently, only the stub does that), with @var{event}
41086 carrying the specific information about the notification.
41087 @var{name} is the name of the notification.
41089 The acknowledge sent by the other side, usually @value{GDBN}, to
41090 acknowledge the exchange and request the event.
41093 The purpose of an asynchronous notification mechanism is to report to
41094 @value{GDBN} that something interesting happened in the remote stub.
41096 The remote stub may send notification @var{name}:@var{event}
41097 at any time, but @value{GDBN} acknowledges the notification when
41098 appropriate. The notification event is pending before @value{GDBN}
41099 acknowledges. Only one notification at a time may be pending; if
41100 additional events occur before @value{GDBN} has acknowledged the
41101 previous notification, they must be queued by the stub for later
41102 synchronous transmission in response to @var{ack} packets from
41103 @value{GDBN}. Because the notification mechanism is unreliable,
41104 the stub is permitted to resend a notification if it believes
41105 @value{GDBN} may not have received it.
41107 Specifically, notifications may appear when @value{GDBN} is not
41108 otherwise reading input from the stub, or when @value{GDBN} is
41109 expecting to read a normal synchronous response or a
41110 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
41111 Notification packets are distinct from any other communication from
41112 the stub so there is no ambiguity.
41114 After receiving a notification, @value{GDBN} shall acknowledge it by
41115 sending a @var{ack} packet as a regular, synchronous request to the
41116 stub. Such acknowledgment is not required to happen immediately, as
41117 @value{GDBN} is permitted to send other, unrelated packets to the
41118 stub first, which the stub should process normally.
41120 Upon receiving a @var{ack} packet, if the stub has other queued
41121 events to report to @value{GDBN}, it shall respond by sending a
41122 normal @var{event}. @value{GDBN} shall then send another @var{ack}
41123 packet to solicit further responses; again, it is permitted to send
41124 other, unrelated packets as well which the stub should process
41127 If the stub receives a @var{ack} packet and there are no additional
41128 @var{event} to report, the stub shall return an @samp{OK} response.
41129 At this point, @value{GDBN} has finished processing a notification
41130 and the stub has completed sending any queued events. @value{GDBN}
41131 won't accept any new notifications until the final @samp{OK} is
41132 received . If further notification events occur, the stub shall send
41133 a new notification, @value{GDBN} shall accept the notification, and
41134 the process shall be repeated.
41136 The process of asynchronous notification can be illustrated by the
41139 <- @code{%%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
41142 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
41144 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
41149 The following notifications are defined:
41150 @multitable @columnfractions 0.12 0.12 0.38 0.38
41159 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
41160 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
41161 for information on how these notifications are acknowledged by
41163 @tab Report an asynchronous stop event in non-stop mode.
41167 @node Remote Non-Stop
41168 @section Remote Protocol Support for Non-Stop Mode
41170 @value{GDBN}'s remote protocol supports non-stop debugging of
41171 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
41172 supports non-stop mode, it should report that to @value{GDBN} by including
41173 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
41175 @value{GDBN} typically sends a @samp{QNonStop} packet only when
41176 establishing a new connection with the stub. Entering non-stop mode
41177 does not alter the state of any currently-running threads, but targets
41178 must stop all threads in any already-attached processes when entering
41179 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
41180 probe the target state after a mode change.
41182 In non-stop mode, when an attached process encounters an event that
41183 would otherwise be reported with a stop reply, it uses the
41184 asynchronous notification mechanism (@pxref{Notification Packets}) to
41185 inform @value{GDBN}. In contrast to all-stop mode, where all threads
41186 in all processes are stopped when a stop reply is sent, in non-stop
41187 mode only the thread reporting the stop event is stopped. That is,
41188 when reporting a @samp{S} or @samp{T} response to indicate completion
41189 of a step operation, hitting a breakpoint, or a fault, only the
41190 affected thread is stopped; any other still-running threads continue
41191 to run. When reporting a @samp{W} or @samp{X} response, all running
41192 threads belonging to other attached processes continue to run.
41194 In non-stop mode, the target shall respond to the @samp{?} packet as
41195 follows. First, any incomplete stop reply notification/@samp{vStopped}
41196 sequence in progress is abandoned. The target must begin a new
41197 sequence reporting stop events for all stopped threads, whether or not
41198 it has previously reported those events to @value{GDBN}. The first
41199 stop reply is sent as a synchronous reply to the @samp{?} packet, and
41200 subsequent stop replies are sent as responses to @samp{vStopped} packets
41201 using the mechanism described above. The target must not send
41202 asynchronous stop reply notifications until the sequence is complete.
41203 If all threads are running when the target receives the @samp{?} packet,
41204 or if the target is not attached to any process, it shall respond
41207 @node Packet Acknowledgment
41208 @section Packet Acknowledgment
41210 @cindex acknowledgment, for @value{GDBN} remote
41211 @cindex packet acknowledgment, for @value{GDBN} remote
41212 By default, when either the host or the target machine receives a packet,
41213 the first response expected is an acknowledgment: either @samp{+} (to indicate
41214 the package was received correctly) or @samp{-} (to request retransmission).
41215 This mechanism allows the @value{GDBN} remote protocol to operate over
41216 unreliable transport mechanisms, such as a serial line.
41218 In cases where the transport mechanism is itself reliable (such as a pipe or
41219 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
41220 It may be desirable to disable them in that case to reduce communication
41221 overhead, or for other reasons. This can be accomplished by means of the
41222 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
41224 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
41225 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
41226 and response format still includes the normal checksum, as described in
41227 @ref{Overview}, but the checksum may be ignored by the receiver.
41229 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
41230 no-acknowledgment mode, it should report that to @value{GDBN}
41231 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
41232 @pxref{qSupported}.
41233 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
41234 disabled via the @code{set remote noack-packet off} command
41235 (@pxref{Remote Configuration}),
41236 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
41237 Only then may the stub actually turn off packet acknowledgments.
41238 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
41239 response, which can be safely ignored by the stub.
41241 Note that @code{set remote noack-packet} command only affects negotiation
41242 between @value{GDBN} and the stub when subsequent connections are made;
41243 it does not affect the protocol acknowledgment state for any current
41245 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
41246 new connection is established,
41247 there is also no protocol request to re-enable the acknowledgments
41248 for the current connection, once disabled.
41253 Example sequence of a target being re-started. Notice how the restart
41254 does not get any direct output:
41259 @emph{target restarts}
41262 <- @code{T001:1234123412341234}
41266 Example sequence of a target being stepped by a single instruction:
41269 -> @code{G1445@dots{}}
41274 <- @code{T001:1234123412341234}
41278 <- @code{1455@dots{}}
41282 @node File-I/O Remote Protocol Extension
41283 @section File-I/O Remote Protocol Extension
41284 @cindex File-I/O remote protocol extension
41287 * File-I/O Overview::
41288 * Protocol Basics::
41289 * The F Request Packet::
41290 * The F Reply Packet::
41291 * The Ctrl-C Message::
41293 * List of Supported Calls::
41294 * Protocol-specific Representation of Datatypes::
41296 * File-I/O Examples::
41299 @node File-I/O Overview
41300 @subsection File-I/O Overview
41301 @cindex file-i/o overview
41303 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
41304 target to use the host's file system and console I/O to perform various
41305 system calls. System calls on the target system are translated into a
41306 remote protocol packet to the host system, which then performs the needed
41307 actions and returns a response packet to the target system.
41308 This simulates file system operations even on targets that lack file systems.
41310 The protocol is defined to be independent of both the host and target systems.
41311 It uses its own internal representation of datatypes and values. Both
41312 @value{GDBN} and the target's @value{GDBN} stub are responsible for
41313 translating the system-dependent value representations into the internal
41314 protocol representations when data is transmitted.
41316 The communication is synchronous. A system call is possible only when
41317 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
41318 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
41319 the target is stopped to allow deterministic access to the target's
41320 memory. Therefore File-I/O is not interruptible by target signals. On
41321 the other hand, it is possible to interrupt File-I/O by a user interrupt
41322 (@samp{Ctrl-C}) within @value{GDBN}.
41324 The target's request to perform a host system call does not finish
41325 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
41326 after finishing the system call, the target returns to continuing the
41327 previous activity (continue, step). No additional continue or step
41328 request from @value{GDBN} is required.
41331 (@value{GDBP}) continue
41332 <- target requests 'system call X'
41333 target is stopped, @value{GDBN} executes system call
41334 -> @value{GDBN} returns result
41335 ... target continues, @value{GDBN} returns to wait for the target
41336 <- target hits breakpoint and sends a Txx packet
41339 The protocol only supports I/O on the console and to regular files on
41340 the host file system. Character or block special devices, pipes,
41341 named pipes, sockets or any other communication method on the host
41342 system are not supported by this protocol.
41344 File I/O is not supported in non-stop mode.
41346 @node Protocol Basics
41347 @subsection Protocol Basics
41348 @cindex protocol basics, file-i/o
41350 The File-I/O protocol uses the @code{F} packet as the request as well
41351 as reply packet. Since a File-I/O system call can only occur when
41352 @value{GDBN} is waiting for a response from the continuing or stepping target,
41353 the File-I/O request is a reply that @value{GDBN} has to expect as a result
41354 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
41355 This @code{F} packet contains all information needed to allow @value{GDBN}
41356 to call the appropriate host system call:
41360 A unique identifier for the requested system call.
41363 All parameters to the system call. Pointers are given as addresses
41364 in the target memory address space. Pointers to strings are given as
41365 pointer/length pair. Numerical values are given as they are.
41366 Numerical control flags are given in a protocol-specific representation.
41370 At this point, @value{GDBN} has to perform the following actions.
41374 If the parameters include pointer values to data needed as input to a
41375 system call, @value{GDBN} requests this data from the target with a
41376 standard @code{m} packet request. This additional communication has to be
41377 expected by the target implementation and is handled as any other @code{m}
41381 @value{GDBN} translates all value from protocol representation to host
41382 representation as needed. Datatypes are coerced into the host types.
41385 @value{GDBN} calls the system call.
41388 It then coerces datatypes back to protocol representation.
41391 If the system call is expected to return data in buffer space specified
41392 by pointer parameters to the call, the data is transmitted to the
41393 target using a @code{M} or @code{X} packet. This packet has to be expected
41394 by the target implementation and is handled as any other @code{M} or @code{X}
41399 Eventually @value{GDBN} replies with another @code{F} packet which contains all
41400 necessary information for the target to continue. This at least contains
41407 @code{errno}, if has been changed by the system call.
41414 After having done the needed type and value coercion, the target continues
41415 the latest continue or step action.
41417 @node The F Request Packet
41418 @subsection The @code{F} Request Packet
41419 @cindex file-i/o request packet
41420 @cindex @code{F} request packet
41422 The @code{F} request packet has the following format:
41425 @item F@var{call-id},@var{parameter@dots{}}
41427 @var{call-id} is the identifier to indicate the host system call to be called.
41428 This is just the name of the function.
41430 @var{parameter@dots{}} are the parameters to the system call.
41431 Parameters are hexadecimal integer values, either the actual values in case
41432 of scalar datatypes, pointers to target buffer space in case of compound
41433 datatypes and unspecified memory areas, or pointer/length pairs in case
41434 of string parameters. These are appended to the @var{call-id} as a
41435 comma-delimited list. All values are transmitted in ASCII
41436 string representation, pointer/length pairs separated by a slash.
41442 @node The F Reply Packet
41443 @subsection The @code{F} Reply Packet
41444 @cindex file-i/o reply packet
41445 @cindex @code{F} reply packet
41447 The @code{F} reply packet has the following format:
41451 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
41453 @var{retcode} is the return code of the system call as hexadecimal value.
41455 @var{errno} is the @code{errno} set by the call, in protocol-specific
41457 This parameter can be omitted if the call was successful.
41459 @var{Ctrl-C flag} is only sent if the user requested a break. In this
41460 case, @var{errno} must be sent as well, even if the call was successful.
41461 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
41468 or, if the call was interrupted before the host call has been performed:
41475 assuming 4 is the protocol-specific representation of @code{EINTR}.
41480 @node The Ctrl-C Message
41481 @subsection The @samp{Ctrl-C} Message
41482 @cindex ctrl-c message, in file-i/o protocol
41484 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
41485 reply packet (@pxref{The F Reply Packet}),
41486 the target should behave as if it had
41487 gotten a break message. The meaning for the target is ``system call
41488 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
41489 (as with a break message) and return to @value{GDBN} with a @code{T02}
41492 It's important for the target to know in which
41493 state the system call was interrupted. There are two possible cases:
41497 The system call hasn't been performed on the host yet.
41500 The system call on the host has been finished.
41504 These two states can be distinguished by the target by the value of the
41505 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
41506 call hasn't been performed. This is equivalent to the @code{EINTR} handling
41507 on POSIX systems. In any other case, the target may presume that the
41508 system call has been finished --- successfully or not --- and should behave
41509 as if the break message arrived right after the system call.
41511 @value{GDBN} must behave reliably. If the system call has not been called
41512 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
41513 @code{errno} in the packet. If the system call on the host has been finished
41514 before the user requests a break, the full action must be finished by
41515 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
41516 The @code{F} packet may only be sent when either nothing has happened
41517 or the full action has been completed.
41520 @subsection Console I/O
41521 @cindex console i/o as part of file-i/o
41523 By default and if not explicitly closed by the target system, the file
41524 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
41525 on the @value{GDBN} console is handled as any other file output operation
41526 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
41527 by @value{GDBN} so that after the target read request from file descriptor
41528 0 all following typing is buffered until either one of the following
41533 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
41535 system call is treated as finished.
41538 The user presses @key{RET}. This is treated as end of input with a trailing
41542 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
41543 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
41547 If the user has typed more characters than fit in the buffer given to
41548 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
41549 either another @code{read(0, @dots{})} is requested by the target, or debugging
41550 is stopped at the user's request.
41553 @node List of Supported Calls
41554 @subsection List of Supported Calls
41555 @cindex list of supported file-i/o calls
41572 @unnumberedsubsubsec open
41573 @cindex open, file-i/o system call
41578 int open(const char *pathname, int flags);
41579 int open(const char *pathname, int flags, mode_t mode);
41583 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
41586 @var{flags} is the bitwise @code{OR} of the following values:
41590 If the file does not exist it will be created. The host
41591 rules apply as far as file ownership and time stamps
41595 When used with @code{O_CREAT}, if the file already exists it is
41596 an error and open() fails.
41599 If the file already exists and the open mode allows
41600 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
41601 truncated to zero length.
41604 The file is opened in append mode.
41607 The file is opened for reading only.
41610 The file is opened for writing only.
41613 The file is opened for reading and writing.
41617 Other bits are silently ignored.
41621 @var{mode} is the bitwise @code{OR} of the following values:
41625 User has read permission.
41628 User has write permission.
41631 Group has read permission.
41634 Group has write permission.
41637 Others have read permission.
41640 Others have write permission.
41644 Other bits are silently ignored.
41647 @item Return value:
41648 @code{open} returns the new file descriptor or -1 if an error
41655 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
41658 @var{pathname} refers to a directory.
41661 The requested access is not allowed.
41664 @var{pathname} was too long.
41667 A directory component in @var{pathname} does not exist.
41670 @var{pathname} refers to a device, pipe, named pipe or socket.
41673 @var{pathname} refers to a file on a read-only filesystem and
41674 write access was requested.
41677 @var{pathname} is an invalid pointer value.
41680 No space on device to create the file.
41683 The process already has the maximum number of files open.
41686 The limit on the total number of files open on the system
41690 The call was interrupted by the user.
41696 @unnumberedsubsubsec close
41697 @cindex close, file-i/o system call
41706 @samp{Fclose,@var{fd}}
41708 @item Return value:
41709 @code{close} returns zero on success, or -1 if an error occurred.
41715 @var{fd} isn't a valid open file descriptor.
41718 The call was interrupted by the user.
41724 @unnumberedsubsubsec read
41725 @cindex read, file-i/o system call
41730 int read(int fd, void *buf, unsigned int count);
41734 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
41736 @item Return value:
41737 On success, the number of bytes read is returned.
41738 Zero indicates end of file. If count is zero, read
41739 returns zero as well. On error, -1 is returned.
41745 @var{fd} is not a valid file descriptor or is not open for
41749 @var{bufptr} is an invalid pointer value.
41752 The call was interrupted by the user.
41758 @unnumberedsubsubsec write
41759 @cindex write, file-i/o system call
41764 int write(int fd, const void *buf, unsigned int count);
41768 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
41770 @item Return value:
41771 On success, the number of bytes written are returned.
41772 Zero indicates nothing was written. On error, -1
41779 @var{fd} is not a valid file descriptor or is not open for
41783 @var{bufptr} is an invalid pointer value.
41786 An attempt was made to write a file that exceeds the
41787 host-specific maximum file size allowed.
41790 No space on device to write the data.
41793 The call was interrupted by the user.
41799 @unnumberedsubsubsec lseek
41800 @cindex lseek, file-i/o system call
41805 long lseek (int fd, long offset, int flag);
41809 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
41811 @var{flag} is one of:
41815 The offset is set to @var{offset} bytes.
41818 The offset is set to its current location plus @var{offset}
41822 The offset is set to the size of the file plus @var{offset}
41826 @item Return value:
41827 On success, the resulting unsigned offset in bytes from
41828 the beginning of the file is returned. Otherwise, a
41829 value of -1 is returned.
41835 @var{fd} is not a valid open file descriptor.
41838 @var{fd} is associated with the @value{GDBN} console.
41841 @var{flag} is not a proper value.
41844 The call was interrupted by the user.
41850 @unnumberedsubsubsec rename
41851 @cindex rename, file-i/o system call
41856 int rename(const char *oldpath, const char *newpath);
41860 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
41862 @item Return value:
41863 On success, zero is returned. On error, -1 is returned.
41869 @var{newpath} is an existing directory, but @var{oldpath} is not a
41873 @var{newpath} is a non-empty directory.
41876 @var{oldpath} or @var{newpath} is a directory that is in use by some
41880 An attempt was made to make a directory a subdirectory
41884 A component used as a directory in @var{oldpath} or new
41885 path is not a directory. Or @var{oldpath} is a directory
41886 and @var{newpath} exists but is not a directory.
41889 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
41892 No access to the file or the path of the file.
41896 @var{oldpath} or @var{newpath} was too long.
41899 A directory component in @var{oldpath} or @var{newpath} does not exist.
41902 The file is on a read-only filesystem.
41905 The device containing the file has no room for the new
41909 The call was interrupted by the user.
41915 @unnumberedsubsubsec unlink
41916 @cindex unlink, file-i/o system call
41921 int unlink(const char *pathname);
41925 @samp{Funlink,@var{pathnameptr}/@var{len}}
41927 @item Return value:
41928 On success, zero is returned. On error, -1 is returned.
41934 No access to the file or the path of the file.
41937 The system does not allow unlinking of directories.
41940 The file @var{pathname} cannot be unlinked because it's
41941 being used by another process.
41944 @var{pathnameptr} is an invalid pointer value.
41947 @var{pathname} was too long.
41950 A directory component in @var{pathname} does not exist.
41953 A component of the path is not a directory.
41956 The file is on a read-only filesystem.
41959 The call was interrupted by the user.
41965 @unnumberedsubsubsec stat/fstat
41966 @cindex fstat, file-i/o system call
41967 @cindex stat, file-i/o system call
41972 int stat(const char *pathname, struct stat *buf);
41973 int fstat(int fd, struct stat *buf);
41977 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
41978 @samp{Ffstat,@var{fd},@var{bufptr}}
41980 @item Return value:
41981 On success, zero is returned. On error, -1 is returned.
41987 @var{fd} is not a valid open file.
41990 A directory component in @var{pathname} does not exist or the
41991 path is an empty string.
41994 A component of the path is not a directory.
41997 @var{pathnameptr} is an invalid pointer value.
42000 No access to the file or the path of the file.
42003 @var{pathname} was too long.
42006 The call was interrupted by the user.
42012 @unnumberedsubsubsec gettimeofday
42013 @cindex gettimeofday, file-i/o system call
42018 int gettimeofday(struct timeval *tv, void *tz);
42022 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
42024 @item Return value:
42025 On success, 0 is returned, -1 otherwise.
42031 @var{tz} is a non-NULL pointer.
42034 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
42040 @unnumberedsubsubsec isatty
42041 @cindex isatty, file-i/o system call
42046 int isatty(int fd);
42050 @samp{Fisatty,@var{fd}}
42052 @item Return value:
42053 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
42059 The call was interrupted by the user.
42064 Note that the @code{isatty} call is treated as a special case: it returns
42065 1 to the target if the file descriptor is attached
42066 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
42067 would require implementing @code{ioctl} and would be more complex than
42072 @unnumberedsubsubsec system
42073 @cindex system, file-i/o system call
42078 int system(const char *command);
42082 @samp{Fsystem,@var{commandptr}/@var{len}}
42084 @item Return value:
42085 If @var{len} is zero, the return value indicates whether a shell is
42086 available. A zero return value indicates a shell is not available.
42087 For non-zero @var{len}, the value returned is -1 on error and the
42088 return status of the command otherwise. Only the exit status of the
42089 command is returned, which is extracted from the host's @code{system}
42090 return value by calling @code{WEXITSTATUS(retval)}. In case
42091 @file{/bin/sh} could not be executed, 127 is returned.
42097 The call was interrupted by the user.
42102 @value{GDBN} takes over the full task of calling the necessary host calls
42103 to perform the @code{system} call. The return value of @code{system} on
42104 the host is simplified before it's returned
42105 to the target. Any termination signal information from the child process
42106 is discarded, and the return value consists
42107 entirely of the exit status of the called command.
42109 Due to security concerns, the @code{system} call is by default refused
42110 by @value{GDBN}. The user has to allow this call explicitly with the
42111 @code{set remote system-call-allowed 1} command.
42114 @item set remote system-call-allowed
42115 @kindex set remote system-call-allowed
42116 Control whether to allow the @code{system} calls in the File I/O
42117 protocol for the remote target. The default is zero (disabled).
42119 @item show remote system-call-allowed
42120 @kindex show remote system-call-allowed
42121 Show whether the @code{system} calls are allowed in the File I/O
42125 @node Protocol-specific Representation of Datatypes
42126 @subsection Protocol-specific Representation of Datatypes
42127 @cindex protocol-specific representation of datatypes, in file-i/o protocol
42130 * Integral Datatypes::
42132 * Memory Transfer::
42137 @node Integral Datatypes
42138 @unnumberedsubsubsec Integral Datatypes
42139 @cindex integral datatypes, in file-i/o protocol
42141 The integral datatypes used in the system calls are @code{int},
42142 @code{unsigned int}, @code{long}, @code{unsigned long},
42143 @code{mode_t}, and @code{time_t}.
42145 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
42146 implemented as 32 bit values in this protocol.
42148 @code{long} and @code{unsigned long} are implemented as 64 bit types.
42150 @xref{Limits}, for corresponding MIN and MAX values (similar to those
42151 in @file{limits.h}) to allow range checking on host and target.
42153 @code{time_t} datatypes are defined as seconds since the Epoch.
42155 All integral datatypes transferred as part of a memory read or write of a
42156 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
42159 @node Pointer Values
42160 @unnumberedsubsubsec Pointer Values
42161 @cindex pointer values, in file-i/o protocol
42163 Pointers to target data are transmitted as they are. An exception
42164 is made for pointers to buffers for which the length isn't
42165 transmitted as part of the function call, namely strings. Strings
42166 are transmitted as a pointer/length pair, both as hex values, e.g.@:
42173 which is a pointer to data of length 18 bytes at position 0x1aaf.
42174 The length is defined as the full string length in bytes, including
42175 the trailing null byte. For example, the string @code{"hello world"}
42176 at address 0x123456 is transmitted as
42182 @node Memory Transfer
42183 @unnumberedsubsubsec Memory Transfer
42184 @cindex memory transfer, in file-i/o protocol
42186 Structured data which is transferred using a memory read or write (for
42187 example, a @code{struct stat}) is expected to be in a protocol-specific format
42188 with all scalar multibyte datatypes being big endian. Translation to
42189 this representation needs to be done both by the target before the @code{F}
42190 packet is sent, and by @value{GDBN} before
42191 it transfers memory to the target. Transferred pointers to structured
42192 data should point to the already-coerced data at any time.
42196 @unnumberedsubsubsec struct stat
42197 @cindex struct stat, in file-i/o protocol
42199 The buffer of type @code{struct stat} used by the target and @value{GDBN}
42200 is defined as follows:
42204 unsigned int st_dev; /* device */
42205 unsigned int st_ino; /* inode */
42206 mode_t st_mode; /* protection */
42207 unsigned int st_nlink; /* number of hard links */
42208 unsigned int st_uid; /* user ID of owner */
42209 unsigned int st_gid; /* group ID of owner */
42210 unsigned int st_rdev; /* device type (if inode device) */
42211 unsigned long st_size; /* total size, in bytes */
42212 unsigned long st_blksize; /* blocksize for filesystem I/O */
42213 unsigned long st_blocks; /* number of blocks allocated */
42214 time_t st_atime; /* time of last access */
42215 time_t st_mtime; /* time of last modification */
42216 time_t st_ctime; /* time of last change */
42220 The integral datatypes conform to the definitions given in the
42221 appropriate section (see @ref{Integral Datatypes}, for details) so this
42222 structure is of size 64 bytes.
42224 The values of several fields have a restricted meaning and/or
42230 A value of 0 represents a file, 1 the console.
42233 No valid meaning for the target. Transmitted unchanged.
42236 Valid mode bits are described in @ref{Constants}. Any other
42237 bits have currently no meaning for the target.
42242 No valid meaning for the target. Transmitted unchanged.
42247 These values have a host and file system dependent
42248 accuracy. Especially on Windows hosts, the file system may not
42249 support exact timing values.
42252 The target gets a @code{struct stat} of the above representation and is
42253 responsible for coercing it to the target representation before
42256 Note that due to size differences between the host, target, and protocol
42257 representations of @code{struct stat} members, these members could eventually
42258 get truncated on the target.
42260 @node struct timeval
42261 @unnumberedsubsubsec struct timeval
42262 @cindex struct timeval, in file-i/o protocol
42264 The buffer of type @code{struct timeval} used by the File-I/O protocol
42265 is defined as follows:
42269 time_t tv_sec; /* second */
42270 long tv_usec; /* microsecond */
42274 The integral datatypes conform to the definitions given in the
42275 appropriate section (see @ref{Integral Datatypes}, for details) so this
42276 structure is of size 8 bytes.
42279 @subsection Constants
42280 @cindex constants, in file-i/o protocol
42282 The following values are used for the constants inside of the
42283 protocol. @value{GDBN} and target are responsible for translating these
42284 values before and after the call as needed.
42295 @unnumberedsubsubsec Open Flags
42296 @cindex open flags, in file-i/o protocol
42298 All values are given in hexadecimal representation.
42310 @node mode_t Values
42311 @unnumberedsubsubsec mode_t Values
42312 @cindex mode_t values, in file-i/o protocol
42314 All values are given in octal representation.
42331 @unnumberedsubsubsec Errno Values
42332 @cindex errno values, in file-i/o protocol
42334 All values are given in decimal representation.
42359 @code{EUNKNOWN} is used as a fallback error value if a host system returns
42360 any error value not in the list of supported error numbers.
42363 @unnumberedsubsubsec Lseek Flags
42364 @cindex lseek flags, in file-i/o protocol
42373 @unnumberedsubsubsec Limits
42374 @cindex limits, in file-i/o protocol
42376 All values are given in decimal representation.
42379 INT_MIN -2147483648
42381 UINT_MAX 4294967295
42382 LONG_MIN -9223372036854775808
42383 LONG_MAX 9223372036854775807
42384 ULONG_MAX 18446744073709551615
42387 @node File-I/O Examples
42388 @subsection File-I/O Examples
42389 @cindex file-i/o examples
42391 Example sequence of a write call, file descriptor 3, buffer is at target
42392 address 0x1234, 6 bytes should be written:
42395 <- @code{Fwrite,3,1234,6}
42396 @emph{request memory read from target}
42399 @emph{return "6 bytes written"}
42403 Example sequence of a read call, file descriptor 3, buffer is at target
42404 address 0x1234, 6 bytes should be read:
42407 <- @code{Fread,3,1234,6}
42408 @emph{request memory write to target}
42409 -> @code{X1234,6:XXXXXX}
42410 @emph{return "6 bytes read"}
42414 Example sequence of a read call, call fails on the host due to invalid
42415 file descriptor (@code{EBADF}):
42418 <- @code{Fread,3,1234,6}
42422 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
42426 <- @code{Fread,3,1234,6}
42431 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
42435 <- @code{Fread,3,1234,6}
42436 -> @code{X1234,6:XXXXXX}
42440 @node Library List Format
42441 @section Library List Format
42442 @cindex library list format, remote protocol
42444 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
42445 same process as your application to manage libraries. In this case,
42446 @value{GDBN} can use the loader's symbol table and normal memory
42447 operations to maintain a list of shared libraries. On other
42448 platforms, the operating system manages loaded libraries.
42449 @value{GDBN} can not retrieve the list of currently loaded libraries
42450 through memory operations, so it uses the @samp{qXfer:libraries:read}
42451 packet (@pxref{qXfer library list read}) instead. The remote stub
42452 queries the target's operating system and reports which libraries
42455 The @samp{qXfer:libraries:read} packet returns an XML document which
42456 lists loaded libraries and their offsets. Each library has an
42457 associated name and one or more segment or section base addresses,
42458 which report where the library was loaded in memory.
42460 For the common case of libraries that are fully linked binaries, the
42461 library should have a list of segments. If the target supports
42462 dynamic linking of a relocatable object file, its library XML element
42463 should instead include a list of allocated sections. The segment or
42464 section bases are start addresses, not relocation offsets; they do not
42465 depend on the library's link-time base addresses.
42467 @value{GDBN} must be linked with the Expat library to support XML
42468 library lists. @xref{Expat}.
42470 A simple memory map, with one loaded library relocated by a single
42471 offset, looks like this:
42475 <library name="/lib/libc.so.6">
42476 <segment address="0x10000000"/>
42481 Another simple memory map, with one loaded library with three
42482 allocated sections (.text, .data, .bss), looks like this:
42486 <library name="sharedlib.o">
42487 <section address="0x10000000"/>
42488 <section address="0x20000000"/>
42489 <section address="0x30000000"/>
42494 The format of a library list is described by this DTD:
42497 <!-- library-list: Root element with versioning -->
42498 <!ELEMENT library-list (library)*>
42499 <!ATTLIST library-list version CDATA #FIXED "1.0">
42500 <!ELEMENT library (segment*, section*)>
42501 <!ATTLIST library name CDATA #REQUIRED>
42502 <!ELEMENT segment EMPTY>
42503 <!ATTLIST segment address CDATA #REQUIRED>
42504 <!ELEMENT section EMPTY>
42505 <!ATTLIST section address CDATA #REQUIRED>
42508 In addition, segments and section descriptors cannot be mixed within a
42509 single library element, and you must supply at least one segment or
42510 section for each library.
42512 @node Library List Format for SVR4 Targets
42513 @section Library List Format for SVR4 Targets
42514 @cindex library list format, remote protocol
42516 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
42517 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
42518 shared libraries. Still a special library list provided by this packet is
42519 more efficient for the @value{GDBN} remote protocol.
42521 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
42522 loaded libraries and their SVR4 linker parameters. For each library on SVR4
42523 target, the following parameters are reported:
42527 @code{name}, the absolute file name from the @code{l_name} field of
42528 @code{struct link_map}.
42530 @code{lm} with address of @code{struct link_map} used for TLS
42531 (Thread Local Storage) access.
42533 @code{l_addr}, the displacement as read from the field @code{l_addr} of
42534 @code{struct link_map}. For prelinked libraries this is not an absolute
42535 memory address. It is a displacement of absolute memory address against
42536 address the file was prelinked to during the library load.
42538 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
42541 Additionally the single @code{main-lm} attribute specifies address of
42542 @code{struct link_map} used for the main executable. This parameter is used
42543 for TLS access and its presence is optional.
42545 @value{GDBN} must be linked with the Expat library to support XML
42546 SVR4 library lists. @xref{Expat}.
42548 A simple memory map, with two loaded libraries (which do not use prelink),
42552 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
42553 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
42555 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
42557 </library-list-svr>
42560 The format of an SVR4 library list is described by this DTD:
42563 <!-- library-list-svr4: Root element with versioning -->
42564 <!ELEMENT library-list-svr4 (library)*>
42565 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
42566 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
42567 <!ELEMENT library EMPTY>
42568 <!ATTLIST library name CDATA #REQUIRED>
42569 <!ATTLIST library lm CDATA #REQUIRED>
42570 <!ATTLIST library l_addr CDATA #REQUIRED>
42571 <!ATTLIST library l_ld CDATA #REQUIRED>
42574 @node Memory Map Format
42575 @section Memory Map Format
42576 @cindex memory map format
42578 To be able to write into flash memory, @value{GDBN} needs to obtain a
42579 memory map from the target. This section describes the format of the
42582 The memory map is obtained using the @samp{qXfer:memory-map:read}
42583 (@pxref{qXfer memory map read}) packet and is an XML document that
42584 lists memory regions.
42586 @value{GDBN} must be linked with the Expat library to support XML
42587 memory maps. @xref{Expat}.
42589 The top-level structure of the document is shown below:
42592 <?xml version="1.0"?>
42593 <!DOCTYPE memory-map
42594 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
42595 "http://sourceware.org/gdb/gdb-memory-map.dtd">
42601 Each region can be either:
42606 A region of RAM starting at @var{addr} and extending for @var{length}
42610 <memory type="ram" start="@var{addr}" length="@var{length}"/>
42615 A region of read-only memory:
42618 <memory type="rom" start="@var{addr}" length="@var{length}"/>
42623 A region of flash memory, with erasure blocks @var{blocksize}
42627 <memory type="flash" start="@var{addr}" length="@var{length}">
42628 <property name="blocksize">@var{blocksize}</property>
42634 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
42635 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
42636 packets to write to addresses in such ranges.
42638 The formal DTD for memory map format is given below:
42641 <!-- ................................................... -->
42642 <!-- Memory Map XML DTD ................................ -->
42643 <!-- File: memory-map.dtd .............................. -->
42644 <!-- .................................... .............. -->
42645 <!-- memory-map.dtd -->
42646 <!-- memory-map: Root element with versioning -->
42647 <!ELEMENT memory-map (memory | property)>
42648 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
42649 <!ELEMENT memory (property)>
42650 <!-- memory: Specifies a memory region,
42651 and its type, or device. -->
42652 <!ATTLIST memory type CDATA #REQUIRED
42653 start CDATA #REQUIRED
42654 length CDATA #REQUIRED
42655 device CDATA #IMPLIED>
42656 <!-- property: Generic attribute tag -->
42657 <!ELEMENT property (#PCDATA | property)*>
42658 <!ATTLIST property name CDATA #REQUIRED>
42661 @node Thread List Format
42662 @section Thread List Format
42663 @cindex thread list format
42665 To efficiently update the list of threads and their attributes,
42666 @value{GDBN} issues the @samp{qXfer:threads:read} packet
42667 (@pxref{qXfer threads read}) and obtains the XML document with
42668 the following structure:
42671 <?xml version="1.0"?>
42673 <thread id="id" core="0">
42674 ... description ...
42679 Each @samp{thread} element must have the @samp{id} attribute that
42680 identifies the thread (@pxref{thread-id syntax}). The
42681 @samp{core} attribute, if present, specifies which processor core
42682 the thread was last executing on. The content of the of @samp{thread}
42683 element is interpreted as human-readable auxilliary information.
42685 @node Traceframe Info Format
42686 @section Traceframe Info Format
42687 @cindex traceframe info format
42689 To be able to know which objects in the inferior can be examined when
42690 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
42691 memory ranges, registers and trace state variables that have been
42692 collected in a traceframe.
42694 This list is obtained using the @samp{qXfer:traceframe-info:read}
42695 (@pxref{qXfer traceframe info read}) packet and is an XML document.
42697 @value{GDBN} must be linked with the Expat library to support XML
42698 traceframe info discovery. @xref{Expat}.
42700 The top-level structure of the document is shown below:
42703 <?xml version="1.0"?>
42704 <!DOCTYPE traceframe-info
42705 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
42706 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
42712 Each traceframe block can be either:
42717 A region of collected memory starting at @var{addr} and extending for
42718 @var{length} bytes from there:
42721 <memory start="@var{addr}" length="@var{length}"/>
42725 A block indicating trace state variable numbered @var{number} has been
42729 <tvar id="@var{number}"/>
42734 The formal DTD for the traceframe info format is given below:
42737 <!ELEMENT traceframe-info (memory | tvar)* >
42738 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
42740 <!ELEMENT memory EMPTY>
42741 <!ATTLIST memory start CDATA #REQUIRED
42742 length CDATA #REQUIRED>
42744 <!ATTLIST tvar id CDATA #REQUIRED>
42747 @node Branch Trace Format
42748 @section Branch Trace Format
42749 @cindex branch trace format
42751 In order to display the branch trace of an inferior thread,
42752 @value{GDBN} needs to obtain the list of branches. This list is
42753 represented as list of sequential code blocks that are connected via
42754 branches. The code in each block has been executed sequentially.
42756 This list is obtained using the @samp{qXfer:btrace:read}
42757 (@pxref{qXfer btrace read}) packet and is an XML document.
42759 @value{GDBN} must be linked with the Expat library to support XML
42760 traceframe info discovery. @xref{Expat}.
42762 The top-level structure of the document is shown below:
42765 <?xml version="1.0"?>
42767 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
42768 "http://sourceware.org/gdb/gdb-btrace.dtd">
42777 A block of sequentially executed instructions starting at @var{begin}
42778 and ending at @var{end}:
42781 <block begin="@var{begin}" end="@var{end}"/>
42786 The formal DTD for the branch trace format is given below:
42789 <!ELEMENT btrace (block)* >
42790 <!ATTLIST btrace version CDATA #FIXED "1.0">
42792 <!ELEMENT block EMPTY>
42793 <!ATTLIST block begin CDATA #REQUIRED
42794 end CDATA #REQUIRED>
42797 @include agentexpr.texi
42799 @node Target Descriptions
42800 @appendix Target Descriptions
42801 @cindex target descriptions
42803 One of the challenges of using @value{GDBN} to debug embedded systems
42804 is that there are so many minor variants of each processor
42805 architecture in use. It is common practice for vendors to start with
42806 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
42807 and then make changes to adapt it to a particular market niche. Some
42808 architectures have hundreds of variants, available from dozens of
42809 vendors. This leads to a number of problems:
42813 With so many different customized processors, it is difficult for
42814 the @value{GDBN} maintainers to keep up with the changes.
42816 Since individual variants may have short lifetimes or limited
42817 audiences, it may not be worthwhile to carry information about every
42818 variant in the @value{GDBN} source tree.
42820 When @value{GDBN} does support the architecture of the embedded system
42821 at hand, the task of finding the correct architecture name to give the
42822 @command{set architecture} command can be error-prone.
42825 To address these problems, the @value{GDBN} remote protocol allows a
42826 target system to not only identify itself to @value{GDBN}, but to
42827 actually describe its own features. This lets @value{GDBN} support
42828 processor variants it has never seen before --- to the extent that the
42829 descriptions are accurate, and that @value{GDBN} understands them.
42831 @value{GDBN} must be linked with the Expat library to support XML
42832 target descriptions. @xref{Expat}.
42835 * Retrieving Descriptions:: How descriptions are fetched from a target.
42836 * Target Description Format:: The contents of a target description.
42837 * Predefined Target Types:: Standard types available for target
42839 * Standard Target Features:: Features @value{GDBN} knows about.
42842 @node Retrieving Descriptions
42843 @section Retrieving Descriptions
42845 Target descriptions can be read from the target automatically, or
42846 specified by the user manually. The default behavior is to read the
42847 description from the target. @value{GDBN} retrieves it via the remote
42848 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
42849 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
42850 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
42851 XML document, of the form described in @ref{Target Description
42854 Alternatively, you can specify a file to read for the target description.
42855 If a file is set, the target will not be queried. The commands to
42856 specify a file are:
42859 @cindex set tdesc filename
42860 @item set tdesc filename @var{path}
42861 Read the target description from @var{path}.
42863 @cindex unset tdesc filename
42864 @item unset tdesc filename
42865 Do not read the XML target description from a file. @value{GDBN}
42866 will use the description supplied by the current target.
42868 @cindex show tdesc filename
42869 @item show tdesc filename
42870 Show the filename to read for a target description, if any.
42874 @node Target Description Format
42875 @section Target Description Format
42876 @cindex target descriptions, XML format
42878 A target description annex is an @uref{http://www.w3.org/XML/, XML}
42879 document which complies with the Document Type Definition provided in
42880 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
42881 means you can use generally available tools like @command{xmllint} to
42882 check that your feature descriptions are well-formed and valid.
42883 However, to help people unfamiliar with XML write descriptions for
42884 their targets, we also describe the grammar here.
42886 Target descriptions can identify the architecture of the remote target
42887 and (for some architectures) provide information about custom register
42888 sets. They can also identify the OS ABI of the remote target.
42889 @value{GDBN} can use this information to autoconfigure for your
42890 target, or to warn you if you connect to an unsupported target.
42892 Here is a simple target description:
42895 <target version="1.0">
42896 <architecture>i386:x86-64</architecture>
42901 This minimal description only says that the target uses
42902 the x86-64 architecture.
42904 A target description has the following overall form, with [ ] marking
42905 optional elements and @dots{} marking repeatable elements. The elements
42906 are explained further below.
42909 <?xml version="1.0"?>
42910 <!DOCTYPE target SYSTEM "gdb-target.dtd">
42911 <target version="1.0">
42912 @r{[}@var{architecture}@r{]}
42913 @r{[}@var{osabi}@r{]}
42914 @r{[}@var{compatible}@r{]}
42915 @r{[}@var{feature}@dots{}@r{]}
42920 The description is generally insensitive to whitespace and line
42921 breaks, under the usual common-sense rules. The XML version
42922 declaration and document type declaration can generally be omitted
42923 (@value{GDBN} does not require them), but specifying them may be
42924 useful for XML validation tools. The @samp{version} attribute for
42925 @samp{<target>} may also be omitted, but we recommend
42926 including it; if future versions of @value{GDBN} use an incompatible
42927 revision of @file{gdb-target.dtd}, they will detect and report
42928 the version mismatch.
42930 @subsection Inclusion
42931 @cindex target descriptions, inclusion
42934 @cindex <xi:include>
42937 It can sometimes be valuable to split a target description up into
42938 several different annexes, either for organizational purposes, or to
42939 share files between different possible target descriptions. You can
42940 divide a description into multiple files by replacing any element of
42941 the target description with an inclusion directive of the form:
42944 <xi:include href="@var{document}"/>
42948 When @value{GDBN} encounters an element of this form, it will retrieve
42949 the named XML @var{document}, and replace the inclusion directive with
42950 the contents of that document. If the current description was read
42951 using @samp{qXfer}, then so will be the included document;
42952 @var{document} will be interpreted as the name of an annex. If the
42953 current description was read from a file, @value{GDBN} will look for
42954 @var{document} as a file in the same directory where it found the
42955 original description.
42957 @subsection Architecture
42958 @cindex <architecture>
42960 An @samp{<architecture>} element has this form:
42963 <architecture>@var{arch}</architecture>
42966 @var{arch} is one of the architectures from the set accepted by
42967 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
42970 @cindex @code{<osabi>}
42972 This optional field was introduced in @value{GDBN} version 7.0.
42973 Previous versions of @value{GDBN} ignore it.
42975 An @samp{<osabi>} element has this form:
42978 <osabi>@var{abi-name}</osabi>
42981 @var{abi-name} is an OS ABI name from the same selection accepted by
42982 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
42984 @subsection Compatible Architecture
42985 @cindex @code{<compatible>}
42987 This optional field was introduced in @value{GDBN} version 7.0.
42988 Previous versions of @value{GDBN} ignore it.
42990 A @samp{<compatible>} element has this form:
42993 <compatible>@var{arch}</compatible>
42996 @var{arch} is one of the architectures from the set accepted by
42997 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
42999 A @samp{<compatible>} element is used to specify that the target
43000 is able to run binaries in some other than the main target architecture
43001 given by the @samp{<architecture>} element. For example, on the
43002 Cell Broadband Engine, the main architecture is @code{powerpc:common}
43003 or @code{powerpc:common64}, but the system is able to run binaries
43004 in the @code{spu} architecture as well. The way to describe this
43005 capability with @samp{<compatible>} is as follows:
43008 <architecture>powerpc:common</architecture>
43009 <compatible>spu</compatible>
43012 @subsection Features
43015 Each @samp{<feature>} describes some logical portion of the target
43016 system. Features are currently used to describe available CPU
43017 registers and the types of their contents. A @samp{<feature>} element
43021 <feature name="@var{name}">
43022 @r{[}@var{type}@dots{}@r{]}
43028 Each feature's name should be unique within the description. The name
43029 of a feature does not matter unless @value{GDBN} has some special
43030 knowledge of the contents of that feature; if it does, the feature
43031 should have its standard name. @xref{Standard Target Features}.
43035 Any register's value is a collection of bits which @value{GDBN} must
43036 interpret. The default interpretation is a two's complement integer,
43037 but other types can be requested by name in the register description.
43038 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
43039 Target Types}), and the description can define additional composite types.
43041 Each type element must have an @samp{id} attribute, which gives
43042 a unique (within the containing @samp{<feature>}) name to the type.
43043 Types must be defined before they are used.
43046 Some targets offer vector registers, which can be treated as arrays
43047 of scalar elements. These types are written as @samp{<vector>} elements,
43048 specifying the array element type, @var{type}, and the number of elements,
43052 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
43056 If a register's value is usefully viewed in multiple ways, define it
43057 with a union type containing the useful representations. The
43058 @samp{<union>} element contains one or more @samp{<field>} elements,
43059 each of which has a @var{name} and a @var{type}:
43062 <union id="@var{id}">
43063 <field name="@var{name}" type="@var{type}"/>
43069 If a register's value is composed from several separate values, define
43070 it with a structure type. There are two forms of the @samp{<struct>}
43071 element; a @samp{<struct>} element must either contain only bitfields
43072 or contain no bitfields. If the structure contains only bitfields,
43073 its total size in bytes must be specified, each bitfield must have an
43074 explicit start and end, and bitfields are automatically assigned an
43075 integer type. The field's @var{start} should be less than or
43076 equal to its @var{end}, and zero represents the least significant bit.
43079 <struct id="@var{id}" size="@var{size}">
43080 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
43085 If the structure contains no bitfields, then each field has an
43086 explicit type, and no implicit padding is added.
43089 <struct id="@var{id}">
43090 <field name="@var{name}" type="@var{type}"/>
43096 If a register's value is a series of single-bit flags, define it with
43097 a flags type. The @samp{<flags>} element has an explicit @var{size}
43098 and contains one or more @samp{<field>} elements. Each field has a
43099 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
43103 <flags id="@var{id}" size="@var{size}">
43104 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
43109 @subsection Registers
43112 Each register is represented as an element with this form:
43115 <reg name="@var{name}"
43116 bitsize="@var{size}"
43117 @r{[}regnum="@var{num}"@r{]}
43118 @r{[}save-restore="@var{save-restore}"@r{]}
43119 @r{[}type="@var{type}"@r{]}
43120 @r{[}group="@var{group}"@r{]}/>
43124 The components are as follows:
43129 The register's name; it must be unique within the target description.
43132 The register's size, in bits.
43135 The register's number. If omitted, a register's number is one greater
43136 than that of the previous register (either in the current feature or in
43137 a preceding feature); the first register in the target description
43138 defaults to zero. This register number is used to read or write
43139 the register; e.g.@: it is used in the remote @code{p} and @code{P}
43140 packets, and registers appear in the @code{g} and @code{G} packets
43141 in order of increasing register number.
43144 Whether the register should be preserved across inferior function
43145 calls; this must be either @code{yes} or @code{no}. The default is
43146 @code{yes}, which is appropriate for most registers except for
43147 some system control registers; this is not related to the target's
43151 The type of the register. @var{type} may be a predefined type, a type
43152 defined in the current feature, or one of the special types @code{int}
43153 and @code{float}. @code{int} is an integer type of the correct size
43154 for @var{bitsize}, and @code{float} is a floating point type (in the
43155 architecture's normal floating point format) of the correct size for
43156 @var{bitsize}. The default is @code{int}.
43159 The register group to which this register belongs. @var{group} must
43160 be either @code{general}, @code{float}, or @code{vector}. If no
43161 @var{group} is specified, @value{GDBN} will not display the register
43162 in @code{info registers}.
43166 @node Predefined Target Types
43167 @section Predefined Target Types
43168 @cindex target descriptions, predefined types
43170 Type definitions in the self-description can build up composite types
43171 from basic building blocks, but can not define fundamental types. Instead,
43172 standard identifiers are provided by @value{GDBN} for the fundamental
43173 types. The currently supported types are:
43182 Signed integer types holding the specified number of bits.
43189 Unsigned integer types holding the specified number of bits.
43193 Pointers to unspecified code and data. The program counter and
43194 any dedicated return address register may be marked as code
43195 pointers; printing a code pointer converts it into a symbolic
43196 address. The stack pointer and any dedicated address registers
43197 may be marked as data pointers.
43200 Single precision IEEE floating point.
43203 Double precision IEEE floating point.
43206 The 12-byte extended precision format used by ARM FPA registers.
43209 The 10-byte extended precision format used by x87 registers.
43212 32bit @sc{eflags} register used by x86.
43215 32bit @sc{mxcsr} register used by x86.
43219 @node Standard Target Features
43220 @section Standard Target Features
43221 @cindex target descriptions, standard features
43223 A target description must contain either no registers or all the
43224 target's registers. If the description contains no registers, then
43225 @value{GDBN} will assume a default register layout, selected based on
43226 the architecture. If the description contains any registers, the
43227 default layout will not be used; the standard registers must be
43228 described in the target description, in such a way that @value{GDBN}
43229 can recognize them.
43231 This is accomplished by giving specific names to feature elements
43232 which contain standard registers. @value{GDBN} will look for features
43233 with those names and verify that they contain the expected registers;
43234 if any known feature is missing required registers, or if any required
43235 feature is missing, @value{GDBN} will reject the target
43236 description. You can add additional registers to any of the
43237 standard features --- @value{GDBN} will display them just as if
43238 they were added to an unrecognized feature.
43240 This section lists the known features and their expected contents.
43241 Sample XML documents for these features are included in the
43242 @value{GDBN} source tree, in the directory @file{gdb/features}.
43244 Names recognized by @value{GDBN} should include the name of the
43245 company or organization which selected the name, and the overall
43246 architecture to which the feature applies; so e.g.@: the feature
43247 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
43249 The names of registers are not case sensitive for the purpose
43250 of recognizing standard features, but @value{GDBN} will only display
43251 registers using the capitalization used in the description.
43254 * AArch64 Features::
43259 * Nios II Features::
43260 * PowerPC Features::
43261 * S/390 and System z Features::
43266 @node AArch64 Features
43267 @subsection AArch64 Features
43268 @cindex target descriptions, AArch64 features
43270 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
43271 targets. It should contain registers @samp{x0} through @samp{x30},
43272 @samp{sp}, @samp{pc}, and @samp{cpsr}.
43274 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
43275 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
43279 @subsection ARM Features
43280 @cindex target descriptions, ARM features
43282 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
43284 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
43285 @samp{lr}, @samp{pc}, and @samp{cpsr}.
43287 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
43288 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
43289 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
43292 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
43293 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
43295 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
43296 it should contain at least registers @samp{wR0} through @samp{wR15} and
43297 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
43298 @samp{wCSSF}, and @samp{wCASF} registers are optional.
43300 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
43301 should contain at least registers @samp{d0} through @samp{d15}. If
43302 they are present, @samp{d16} through @samp{d31} should also be included.
43303 @value{GDBN} will synthesize the single-precision registers from
43304 halves of the double-precision registers.
43306 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
43307 need to contain registers; it instructs @value{GDBN} to display the
43308 VFP double-precision registers as vectors and to synthesize the
43309 quad-precision registers from pairs of double-precision registers.
43310 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
43311 be present and include 32 double-precision registers.
43313 @node i386 Features
43314 @subsection i386 Features
43315 @cindex target descriptions, i386 features
43317 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
43318 targets. It should describe the following registers:
43322 @samp{eax} through @samp{edi} plus @samp{eip} for i386
43324 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
43326 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
43327 @samp{fs}, @samp{gs}
43329 @samp{st0} through @samp{st7}
43331 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
43332 @samp{foseg}, @samp{fooff} and @samp{fop}
43335 The register sets may be different, depending on the target.
43337 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
43338 describe registers:
43342 @samp{xmm0} through @samp{xmm7} for i386
43344 @samp{xmm0} through @samp{xmm15} for amd64
43349 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
43350 @samp{org.gnu.gdb.i386.sse} feature. It should
43351 describe the upper 128 bits of @sc{ymm} registers:
43355 @samp{ymm0h} through @samp{ymm7h} for i386
43357 @samp{ymm0h} through @samp{ymm15h} for amd64
43360 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel(R)
43361 Memory Protection Extension (MPX). It should describe the following registers:
43365 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
43367 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
43370 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
43371 describe a single register, @samp{orig_eax}.
43373 @node MIPS Features
43374 @subsection @acronym{MIPS} Features
43375 @cindex target descriptions, @acronym{MIPS} features
43377 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
43378 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
43379 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
43382 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
43383 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
43384 registers. They may be 32-bit or 64-bit depending on the target.
43386 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
43387 it may be optional in a future version of @value{GDBN}. It should
43388 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
43389 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
43391 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
43392 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
43393 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
43394 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
43396 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
43397 contain a single register, @samp{restart}, which is used by the
43398 Linux kernel to control restartable syscalls.
43400 @node M68K Features
43401 @subsection M68K Features
43402 @cindex target descriptions, M68K features
43405 @item @samp{org.gnu.gdb.m68k.core}
43406 @itemx @samp{org.gnu.gdb.coldfire.core}
43407 @itemx @samp{org.gnu.gdb.fido.core}
43408 One of those features must be always present.
43409 The feature that is present determines which flavor of m68k is
43410 used. The feature that is present should contain registers
43411 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
43412 @samp{sp}, @samp{ps} and @samp{pc}.
43414 @item @samp{org.gnu.gdb.coldfire.fp}
43415 This feature is optional. If present, it should contain registers
43416 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
43420 @node Nios II Features
43421 @subsection Nios II Features
43422 @cindex target descriptions, Nios II features
43424 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
43425 targets. It should contain the 32 core registers (@samp{zero},
43426 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
43427 @samp{pc}, and the 16 control registers (@samp{status} through
43430 @node PowerPC Features
43431 @subsection PowerPC Features
43432 @cindex target descriptions, PowerPC features
43434 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
43435 targets. It should contain registers @samp{r0} through @samp{r31},
43436 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
43437 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
43439 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
43440 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
43442 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
43443 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
43446 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
43447 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
43448 will combine these registers with the floating point registers
43449 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
43450 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
43451 through @samp{vs63}, the set of vector registers for POWER7.
43453 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
43454 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
43455 @samp{spefscr}. SPE targets should provide 32-bit registers in
43456 @samp{org.gnu.gdb.power.core} and provide the upper halves in
43457 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
43458 these to present registers @samp{ev0} through @samp{ev31} to the
43461 @node S/390 and System z Features
43462 @subsection S/390 and System z Features
43463 @cindex target descriptions, S/390 features
43464 @cindex target descriptions, System z features
43466 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
43467 System z targets. It should contain the PSW and the 16 general
43468 registers. In particular, System z targets should provide the 64-bit
43469 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
43470 S/390 targets should provide the 32-bit versions of these registers.
43471 A System z target that runs in 31-bit addressing mode should provide
43472 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
43473 register's upper halves @samp{r0h} through @samp{r15h}, and their
43474 lower halves @samp{r0l} through @samp{r15l}.
43476 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
43477 contain the 64-bit registers @samp{f0} through @samp{f15}, and
43480 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
43481 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
43483 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
43484 contain the register @samp{orig_r2}, which is 64-bit wide on System z
43485 targets and 32-bit otherwise. In addition, the feature may contain
43486 the @samp{last_break} register, whose width depends on the addressing
43487 mode, as well as the @samp{system_call} register, which is always
43490 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
43491 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
43492 @samp{atia}, and @samp{tr0} through @samp{tr15}.
43494 @node TIC6x Features
43495 @subsection TMS320C6x Features
43496 @cindex target descriptions, TIC6x features
43497 @cindex target descriptions, TMS320C6x features
43498 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
43499 targets. It should contain registers @samp{A0} through @samp{A15},
43500 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
43502 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
43503 contain registers @samp{A16} through @samp{A31} and @samp{B16}
43504 through @samp{B31}.
43506 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
43507 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
43509 @node Operating System Information
43510 @appendix Operating System Information
43511 @cindex operating system information
43517 Users of @value{GDBN} often wish to obtain information about the state of
43518 the operating system running on the target---for example the list of
43519 processes, or the list of open files. This section describes the
43520 mechanism that makes it possible. This mechanism is similar to the
43521 target features mechanism (@pxref{Target Descriptions}), but focuses
43522 on a different aspect of target.
43524 Operating system information is retrived from the target via the
43525 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
43526 read}). The object name in the request should be @samp{osdata}, and
43527 the @var{annex} identifies the data to be fetched.
43530 @appendixsection Process list
43531 @cindex operating system information, process list
43533 When requesting the process list, the @var{annex} field in the
43534 @samp{qXfer} request should be @samp{processes}. The returned data is
43535 an XML document. The formal syntax of this document is defined in
43536 @file{gdb/features/osdata.dtd}.
43538 An example document is:
43541 <?xml version="1.0"?>
43542 <!DOCTYPE target SYSTEM "osdata.dtd">
43543 <osdata type="processes">
43545 <column name="pid">1</column>
43546 <column name="user">root</column>
43547 <column name="command">/sbin/init</column>
43548 <column name="cores">1,2,3</column>
43553 Each item should include a column whose name is @samp{pid}. The value
43554 of that column should identify the process on the target. The
43555 @samp{user} and @samp{command} columns are optional, and will be
43556 displayed by @value{GDBN}. The @samp{cores} column, if present,
43557 should contain a comma-separated list of cores that this process
43558 is running on. Target may provide additional columns,
43559 which @value{GDBN} currently ignores.
43561 @node Trace File Format
43562 @appendix Trace File Format
43563 @cindex trace file format
43565 The trace file comes in three parts: a header, a textual description
43566 section, and a trace frame section with binary data.
43568 The header has the form @code{\x7fTRACE0\n}. The first byte is
43569 @code{0x7f} so as to indicate that the file contains binary data,
43570 while the @code{0} is a version number that may have different values
43573 The description section consists of multiple lines of @sc{ascii} text
43574 separated by newline characters (@code{0xa}). The lines may include a
43575 variety of optional descriptive or context-setting information, such
43576 as tracepoint definitions or register set size. @value{GDBN} will
43577 ignore any line that it does not recognize. An empty line marks the end
43580 @c FIXME add some specific types of data
43582 The trace frame section consists of a number of consecutive frames.
43583 Each frame begins with a two-byte tracepoint number, followed by a
43584 four-byte size giving the amount of data in the frame. The data in
43585 the frame consists of a number of blocks, each introduced by a
43586 character indicating its type (at least register, memory, and trace
43587 state variable). The data in this section is raw binary, not a
43588 hexadecimal or other encoding; its endianness matches the target's
43591 @c FIXME bi-arch may require endianness/arch info in description section
43594 @item R @var{bytes}
43595 Register block. The number and ordering of bytes matches that of a
43596 @code{g} packet in the remote protocol. Note that these are the
43597 actual bytes, in target order and @value{GDBN} register order, not a
43598 hexadecimal encoding.
43600 @item M @var{address} @var{length} @var{bytes}...
43601 Memory block. This is a contiguous block of memory, at the 8-byte
43602 address @var{address}, with a 2-byte length @var{length}, followed by
43603 @var{length} bytes.
43605 @item V @var{number} @var{value}
43606 Trace state variable block. This records the 8-byte signed value
43607 @var{value} of trace state variable numbered @var{number}.
43611 Future enhancements of the trace file format may include additional types
43614 @node Index Section Format
43615 @appendix @code{.gdb_index} section format
43616 @cindex .gdb_index section format
43617 @cindex index section format
43619 This section documents the index section that is created by @code{save
43620 gdb-index} (@pxref{Index Files}). The index section is
43621 DWARF-specific; some knowledge of DWARF is assumed in this
43624 The mapped index file format is designed to be directly
43625 @code{mmap}able on any architecture. In most cases, a datum is
43626 represented using a little-endian 32-bit integer value, called an
43627 @code{offset_type}. Big endian machines must byte-swap the values
43628 before using them. Exceptions to this rule are noted. The data is
43629 laid out such that alignment is always respected.
43631 A mapped index consists of several areas, laid out in order.
43635 The file header. This is a sequence of values, of @code{offset_type}
43636 unless otherwise noted:
43640 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
43641 Version 4 uses a different hashing function from versions 5 and 6.
43642 Version 6 includes symbols for inlined functions, whereas versions 4
43643 and 5 do not. Version 7 adds attributes to the CU indices in the
43644 symbol table. Version 8 specifies that symbols from DWARF type units
43645 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
43646 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
43648 @value{GDBN} will only read version 4, 5, or 6 indices
43649 by specifying @code{set use-deprecated-index-sections on}.
43650 GDB has a workaround for potentially broken version 7 indices so it is
43651 currently not flagged as deprecated.
43654 The offset, from the start of the file, of the CU list.
43657 The offset, from the start of the file, of the types CU list. Note
43658 that this area can be empty, in which case this offset will be equal
43659 to the next offset.
43662 The offset, from the start of the file, of the address area.
43665 The offset, from the start of the file, of the symbol table.
43668 The offset, from the start of the file, of the constant pool.
43672 The CU list. This is a sequence of pairs of 64-bit little-endian
43673 values, sorted by the CU offset. The first element in each pair is
43674 the offset of a CU in the @code{.debug_info} section. The second
43675 element in each pair is the length of that CU. References to a CU
43676 elsewhere in the map are done using a CU index, which is just the
43677 0-based index into this table. Note that if there are type CUs, then
43678 conceptually CUs and type CUs form a single list for the purposes of
43682 The types CU list. This is a sequence of triplets of 64-bit
43683 little-endian values. In a triplet, the first value is the CU offset,
43684 the second value is the type offset in the CU, and the third value is
43685 the type signature. The types CU list is not sorted.
43688 The address area. The address area consists of a sequence of address
43689 entries. Each address entry has three elements:
43693 The low address. This is a 64-bit little-endian value.
43696 The high address. This is a 64-bit little-endian value. Like
43697 @code{DW_AT_high_pc}, the value is one byte beyond the end.
43700 The CU index. This is an @code{offset_type} value.
43704 The symbol table. This is an open-addressed hash table. The size of
43705 the hash table is always a power of 2.
43707 Each slot in the hash table consists of a pair of @code{offset_type}
43708 values. The first value is the offset of the symbol's name in the
43709 constant pool. The second value is the offset of the CU vector in the
43712 If both values are 0, then this slot in the hash table is empty. This
43713 is ok because while 0 is a valid constant pool index, it cannot be a
43714 valid index for both a string and a CU vector.
43716 The hash value for a table entry is computed by applying an
43717 iterative hash function to the symbol's name. Starting with an
43718 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
43719 the string is incorporated into the hash using the formula depending on the
43724 The formula is @code{r = r * 67 + c - 113}.
43726 @item Versions 5 to 7
43727 The formula is @code{r = r * 67 + tolower (c) - 113}.
43730 The terminating @samp{\0} is not incorporated into the hash.
43732 The step size used in the hash table is computed via
43733 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
43734 value, and @samp{size} is the size of the hash table. The step size
43735 is used to find the next candidate slot when handling a hash
43738 The names of C@t{++} symbols in the hash table are canonicalized. We
43739 don't currently have a simple description of the canonicalization
43740 algorithm; if you intend to create new index sections, you must read
43744 The constant pool. This is simply a bunch of bytes. It is organized
43745 so that alignment is correct: CU vectors are stored first, followed by
43748 A CU vector in the constant pool is a sequence of @code{offset_type}
43749 values. The first value is the number of CU indices in the vector.
43750 Each subsequent value is the index and symbol attributes of a CU in
43751 the CU list. This element in the hash table is used to indicate which
43752 CUs define the symbol and how the symbol is used.
43753 See below for the format of each CU index+attributes entry.
43755 A string in the constant pool is zero-terminated.
43758 Attributes were added to CU index values in @code{.gdb_index} version 7.
43759 If a symbol has multiple uses within a CU then there is one
43760 CU index+attributes value for each use.
43762 The format of each CU index+attributes entry is as follows
43768 This is the index of the CU in the CU list.
43770 These bits are reserved for future purposes and must be zero.
43772 The kind of the symbol in the CU.
43776 This value is reserved and should not be used.
43777 By reserving zero the full @code{offset_type} value is backwards compatible
43778 with previous versions of the index.
43780 The symbol is a type.
43782 The symbol is a variable or an enum value.
43784 The symbol is a function.
43786 Any other kind of symbol.
43788 These values are reserved.
43792 This bit is zero if the value is global and one if it is static.
43794 The determination of whether a symbol is global or static is complicated.
43795 The authorative reference is the file @file{dwarf2read.c} in
43796 @value{GDBN} sources.
43800 This pseudo-code describes the computation of a symbol's kind and
43801 global/static attributes in the index.
43804 is_external = get_attribute (die, DW_AT_external);
43805 language = get_attribute (cu_die, DW_AT_language);
43808 case DW_TAG_typedef:
43809 case DW_TAG_base_type:
43810 case DW_TAG_subrange_type:
43814 case DW_TAG_enumerator:
43816 is_static = (language != CPLUS && language != JAVA);
43818 case DW_TAG_subprogram:
43820 is_static = ! (is_external || language == ADA);
43822 case DW_TAG_constant:
43824 is_static = ! is_external;
43826 case DW_TAG_variable:
43828 is_static = ! is_external;
43830 case DW_TAG_namespace:
43834 case DW_TAG_class_type:
43835 case DW_TAG_interface_type:
43836 case DW_TAG_structure_type:
43837 case DW_TAG_union_type:
43838 case DW_TAG_enumeration_type:
43840 is_static = (language != CPLUS && language != JAVA);
43848 @appendix Manual pages
43852 * gdb man:: The GNU Debugger man page
43853 * gdbserver man:: Remote Server for the GNU Debugger man page
43854 * gcore man:: Generate a core file of a running program
43855 * gdbinit man:: gdbinit scripts
43861 @c man title gdb The GNU Debugger
43863 @c man begin SYNOPSIS gdb
43864 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
43865 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
43866 [@option{-b}@w{ }@var{bps}]
43867 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
43868 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
43869 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
43870 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
43871 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
43874 @c man begin DESCRIPTION gdb
43875 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
43876 going on ``inside'' another program while it executes -- or what another
43877 program was doing at the moment it crashed.
43879 @value{GDBN} can do four main kinds of things (plus other things in support of
43880 these) to help you catch bugs in the act:
43884 Start your program, specifying anything that might affect its behavior.
43887 Make your program stop on specified conditions.
43890 Examine what has happened, when your program has stopped.
43893 Change things in your program, so you can experiment with correcting the
43894 effects of one bug and go on to learn about another.
43897 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
43900 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
43901 commands from the terminal until you tell it to exit with the @value{GDBN}
43902 command @code{quit}. You can get online help from @value{GDBN} itself
43903 by using the command @code{help}.
43905 You can run @code{gdb} with no arguments or options; but the most
43906 usual way to start @value{GDBN} is with one argument or two, specifying an
43907 executable program as the argument:
43913 You can also start with both an executable program and a core file specified:
43919 You can, instead, specify a process ID as a second argument, if you want
43920 to debug a running process:
43928 would attach @value{GDBN} to process @code{1234} (unless you also have a file
43929 named @file{1234}; @value{GDBN} does check for a core file first).
43930 With option @option{-p} you can omit the @var{program} filename.
43932 Here are some of the most frequently needed @value{GDBN} commands:
43934 @c pod2man highlights the right hand side of the @item lines.
43936 @item break [@var{file}:]@var{functiop}
43937 Set a breakpoint at @var{function} (in @var{file}).
43939 @item run [@var{arglist}]
43940 Start your program (with @var{arglist}, if specified).
43943 Backtrace: display the program stack.
43945 @item print @var{expr}
43946 Display the value of an expression.
43949 Continue running your program (after stopping, e.g. at a breakpoint).
43952 Execute next program line (after stopping); step @emph{over} any
43953 function calls in the line.
43955 @item edit [@var{file}:]@var{function}
43956 look at the program line where it is presently stopped.
43958 @item list [@var{file}:]@var{function}
43959 type the text of the program in the vicinity of where it is presently stopped.
43962 Execute next program line (after stopping); step @emph{into} any
43963 function calls in the line.
43965 @item help [@var{name}]
43966 Show information about @value{GDBN} command @var{name}, or general information
43967 about using @value{GDBN}.
43970 Exit from @value{GDBN}.
43974 For full details on @value{GDBN},
43975 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43976 by Richard M. Stallman and Roland H. Pesch. The same text is available online
43977 as the @code{gdb} entry in the @code{info} program.
43981 @c man begin OPTIONS gdb
43982 Any arguments other than options specify an executable
43983 file and core file (or process ID); that is, the first argument
43984 encountered with no
43985 associated option flag is equivalent to a @option{-se} option, and the second,
43986 if any, is equivalent to a @option{-c} option if it's the name of a file.
43988 both long and short forms; both are shown here. The long forms are also
43989 recognized if you truncate them, so long as enough of the option is
43990 present to be unambiguous. (If you prefer, you can flag option
43991 arguments with @option{+} rather than @option{-}, though we illustrate the
43992 more usual convention.)
43994 All the options and command line arguments you give are processed
43995 in sequential order. The order makes a difference when the @option{-x}
44001 List all options, with brief explanations.
44003 @item -symbols=@var{file}
44004 @itemx -s @var{file}
44005 Read symbol table from file @var{file}.
44008 Enable writing into executable and core files.
44010 @item -exec=@var{file}
44011 @itemx -e @var{file}
44012 Use file @var{file} as the executable file to execute when
44013 appropriate, and for examining pure data in conjunction with a core
44016 @item -se=@var{file}
44017 Read symbol table from file @var{file} and use it as the executable
44020 @item -core=@var{file}
44021 @itemx -c @var{file}
44022 Use file @var{file} as a core dump to examine.
44024 @item -command=@var{file}
44025 @itemx -x @var{file}
44026 Execute @value{GDBN} commands from file @var{file}.
44028 @item -ex @var{command}
44029 Execute given @value{GDBN} @var{command}.
44031 @item -directory=@var{directory}
44032 @itemx -d @var{directory}
44033 Add @var{directory} to the path to search for source files.
44036 Do not execute commands from @file{~/.gdbinit}.
44040 Do not execute commands from any @file{.gdbinit} initialization files.
44044 ``Quiet''. Do not print the introductory and copyright messages. These
44045 messages are also suppressed in batch mode.
44048 Run in batch mode. Exit with status @code{0} after processing all the command
44049 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
44050 Exit with nonzero status if an error occurs in executing the @value{GDBN}
44051 commands in the command files.
44053 Batch mode may be useful for running @value{GDBN} as a filter, for example to
44054 download and run a program on another computer; in order to make this
44055 more useful, the message
44058 Program exited normally.
44062 (which is ordinarily issued whenever a program running under @value{GDBN} control
44063 terminates) is not issued when running in batch mode.
44065 @item -cd=@var{directory}
44066 Run @value{GDBN} using @var{directory} as its working directory,
44067 instead of the current directory.
44071 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
44072 @value{GDBN} to output the full file name and line number in a standard,
44073 recognizable fashion each time a stack frame is displayed (which
44074 includes each time the program stops). This recognizable format looks
44075 like two @samp{\032} characters, followed by the file name, line number
44076 and character position separated by colons, and a newline. The
44077 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
44078 characters as a signal to display the source code for the frame.
44081 Set the line speed (baud rate or bits per second) of any serial
44082 interface used by @value{GDBN} for remote debugging.
44084 @item -tty=@var{device}
44085 Run using @var{device} for your program's standard input and output.
44089 @c man begin SEEALSO gdb
44091 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44092 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44093 documentation are properly installed at your site, the command
44100 should give you access to the complete manual.
44102 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44103 Richard M. Stallman and Roland H. Pesch, July 1991.
44107 @node gdbserver man
44108 @heading gdbserver man
44110 @c man title gdbserver Remote Server for the GNU Debugger
44112 @c man begin SYNOPSIS gdbserver
44113 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
44115 gdbserver --attach @var{comm} @var{pid}
44117 gdbserver --multi @var{comm}
44121 @c man begin DESCRIPTION gdbserver
44122 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
44123 than the one which is running the program being debugged.
44126 @subheading Usage (server (target) side)
44129 Usage (server (target) side):
44132 First, you need to have a copy of the program you want to debug put onto
44133 the target system. The program can be stripped to save space if needed, as
44134 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
44135 the @value{GDBN} running on the host system.
44137 To use the server, you log on to the target system, and run the @command{gdbserver}
44138 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
44139 your program, and (c) its arguments. The general syntax is:
44142 target> gdbserver @var{comm} @var{program} [@var{args} ...]
44145 For example, using a serial port, you might say:
44149 @c @file would wrap it as F</dev/com1>.
44150 target> gdbserver /dev/com1 emacs foo.txt
44153 target> gdbserver @file{/dev/com1} emacs foo.txt
44157 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
44158 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
44159 waits patiently for the host @value{GDBN} to communicate with it.
44161 To use a TCP connection, you could say:
44164 target> gdbserver host:2345 emacs foo.txt
44167 This says pretty much the same thing as the last example, except that we are
44168 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
44169 that we are expecting to see a TCP connection from @code{host} to local TCP port
44170 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
44171 want for the port number as long as it does not conflict with any existing TCP
44172 ports on the target system. This same port number must be used in the host
44173 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
44174 you chose a port number that conflicts with another service, @command{gdbserver} will
44175 print an error message and exit.
44177 @command{gdbserver} can also attach to running programs.
44178 This is accomplished via the @option{--attach} argument. The syntax is:
44181 target> gdbserver --attach @var{comm} @var{pid}
44184 @var{pid} is the process ID of a currently running process. It isn't
44185 necessary to point @command{gdbserver} at a binary for the running process.
44187 To start @code{gdbserver} without supplying an initial command to run
44188 or process ID to attach, use the @option{--multi} command line option.
44189 In such case you should connect using @kbd{target extended-remote} to start
44190 the program you want to debug.
44193 target> gdbserver --multi @var{comm}
44197 @subheading Usage (host side)
44203 You need an unstripped copy of the target program on your host system, since
44204 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
44205 would, with the target program as the first argument. (You may need to use the
44206 @option{--baud} option if the serial line is running at anything except 9600 baud.)
44207 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
44208 new command you need to know about is @code{target remote}
44209 (or @code{target extended-remote}). Its argument is either
44210 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
44211 descriptor. For example:
44215 @c @file would wrap it as F</dev/ttyb>.
44216 (gdb) target remote /dev/ttyb
44219 (gdb) target remote @file{/dev/ttyb}
44224 communicates with the server via serial line @file{/dev/ttyb}, and:
44227 (gdb) target remote the-target:2345
44231 communicates via a TCP connection to port 2345 on host `the-target', where
44232 you previously started up @command{gdbserver} with the same port number. Note that for
44233 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
44234 command, otherwise you may get an error that looks something like
44235 `Connection refused'.
44237 @command{gdbserver} can also debug multiple inferiors at once,
44240 the @value{GDBN} manual in node @code{Inferiors and Programs}
44241 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
44244 @ref{Inferiors and Programs}.
44246 In such case use the @code{extended-remote} @value{GDBN} command variant:
44249 (gdb) target extended-remote the-target:2345
44252 The @command{gdbserver} option @option{--multi} may or may not be used in such
44256 @c man begin OPTIONS gdbserver
44257 There are three different modes for invoking @command{gdbserver}:
44262 Debug a specific program specified by its program name:
44265 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
44268 The @var{comm} parameter specifies how should the server communicate
44269 with @value{GDBN}; it is either a device name (to use a serial line),
44270 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
44271 stdin/stdout of @code{gdbserver}. Specify the name of the program to
44272 debug in @var{prog}. Any remaining arguments will be passed to the
44273 program verbatim. When the program exits, @value{GDBN} will close the
44274 connection, and @code{gdbserver} will exit.
44277 Debug a specific program by specifying the process ID of a running
44281 gdbserver --attach @var{comm} @var{pid}
44284 The @var{comm} parameter is as described above. Supply the process ID
44285 of a running program in @var{pid}; @value{GDBN} will do everything
44286 else. Like with the previous mode, when the process @var{pid} exits,
44287 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
44290 Multi-process mode -- debug more than one program/process:
44293 gdbserver --multi @var{comm}
44296 In this mode, @value{GDBN} can instruct @command{gdbserver} which
44297 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
44298 close the connection when a process being debugged exits, so you can
44299 debug several processes in the same session.
44302 In each of the modes you may specify these options:
44307 List all options, with brief explanations.
44310 This option causes @command{gdbserver} to print its version number and exit.
44313 @command{gdbserver} will attach to a running program. The syntax is:
44316 target> gdbserver --attach @var{comm} @var{pid}
44319 @var{pid} is the process ID of a currently running process. It isn't
44320 necessary to point @command{gdbserver} at a binary for the running process.
44323 To start @code{gdbserver} without supplying an initial command to run
44324 or process ID to attach, use this command line option.
44325 Then you can connect using @kbd{target extended-remote} and start
44326 the program you want to debug. The syntax is:
44329 target> gdbserver --multi @var{comm}
44333 Instruct @code{gdbserver} to display extra status information about the debugging
44335 This option is intended for @code{gdbserver} development and for bug reports to
44338 @item --remote-debug
44339 Instruct @code{gdbserver} to display remote protocol debug output.
44340 This option is intended for @code{gdbserver} development and for bug reports to
44344 Specify a wrapper to launch programs
44345 for debugging. The option should be followed by the name of the
44346 wrapper, then any command-line arguments to pass to the wrapper, then
44347 @kbd{--} indicating the end of the wrapper arguments.
44350 By default, @command{gdbserver} keeps the listening TCP port open, so that
44351 additional connections are possible. However, if you start @code{gdbserver}
44352 with the @option{--once} option, it will stop listening for any further
44353 connection attempts after connecting to the first @value{GDBN} session.
44355 @c --disable-packet is not documented for users.
44357 @c --disable-randomization and --no-disable-randomization are superseded by
44358 @c QDisableRandomization.
44363 @c man begin SEEALSO gdbserver
44365 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44366 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44367 documentation are properly installed at your site, the command
44373 should give you access to the complete manual.
44375 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44376 Richard M. Stallman and Roland H. Pesch, July 1991.
44383 @c man title gcore Generate a core file of a running program
44386 @c man begin SYNOPSIS gcore
44387 gcore [-o @var{filename}] @var{pid}
44391 @c man begin DESCRIPTION gcore
44392 Generate a core dump of a running program with process ID @var{pid}.
44393 Produced file is equivalent to a kernel produced core file as if the process
44394 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
44395 limit). Unlike after a crash, after @command{gcore} the program remains
44396 running without any change.
44399 @c man begin OPTIONS gcore
44401 @item -o @var{filename}
44402 The optional argument
44403 @var{filename} specifies the file name where to put the core dump.
44404 If not specified, the file name defaults to @file{core.@var{pid}},
44405 where @var{pid} is the running program process ID.
44409 @c man begin SEEALSO gcore
44411 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44412 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44413 documentation are properly installed at your site, the command
44420 should give you access to the complete manual.
44422 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44423 Richard M. Stallman and Roland H. Pesch, July 1991.
44430 @c man title gdbinit GDB initialization scripts
44433 @c man begin SYNOPSIS gdbinit
44434 @ifset SYSTEM_GDBINIT
44435 @value{SYSTEM_GDBINIT}
44444 @c man begin DESCRIPTION gdbinit
44445 These files contain @value{GDBN} commands to automatically execute during
44446 @value{GDBN} startup. The lines of contents are canned sequences of commands,
44449 the @value{GDBN} manual in node @code{Sequences}
44450 -- shell command @code{info -f gdb -n Sequences}.
44456 Please read more in
44458 the @value{GDBN} manual in node @code{Startup}
44459 -- shell command @code{info -f gdb -n Startup}.
44466 @ifset SYSTEM_GDBINIT
44467 @item @value{SYSTEM_GDBINIT}
44469 @ifclear SYSTEM_GDBINIT
44470 @item (not enabled with @code{--with-system-gdbinit} during compilation)
44472 System-wide initialization file. It is executed unless user specified
44473 @value{GDBN} option @code{-nx} or @code{-n}.
44476 the @value{GDBN} manual in node @code{System-wide configuration}
44477 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
44480 @ref{System-wide configuration}.
44484 User initialization file. It is executed unless user specified
44485 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
44488 Initialization file for current directory. It may need to be enabled with
44489 @value{GDBN} security command @code{set auto-load local-gdbinit}.
44492 the @value{GDBN} manual in node @code{Init File in the Current Directory}
44493 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
44496 @ref{Init File in the Current Directory}.
44501 @c man begin SEEALSO gdbinit
44503 gdb(1), @code{info -f gdb -n Startup}
44505 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44506 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44507 documentation are properly installed at your site, the command
44513 should give you access to the complete manual.
44515 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44516 Richard M. Stallman and Roland H. Pesch, July 1991.
44522 @node GNU Free Documentation License
44523 @appendix GNU Free Documentation License
44526 @node Concept Index
44527 @unnumbered Concept Index
44531 @node Command and Variable Index
44532 @unnumbered Command, Variable, and Function Index
44537 % I think something like @@colophon should be in texinfo. In the
44539 \long\def\colophon{\hbox to0pt{}\vfill
44540 \centerline{The body of this manual is set in}
44541 \centerline{\fontname\tenrm,}
44542 \centerline{with headings in {\bf\fontname\tenbf}}
44543 \centerline{and examples in {\tt\fontname\tentt}.}
44544 \centerline{{\it\fontname\tenit\/},}
44545 \centerline{{\bf\fontname\tenbf}, and}
44546 \centerline{{\sl\fontname\tensl\/}}
44547 \centerline{are used for emphasis.}\vfill}
44549 % Blame: doc@@cygnus.com, 1991.